CA2197583A1 - Capacity indicator and load measuring system for arial lifts - Google Patents
Capacity indicator and load measuring system for arial liftsInfo
- Publication number
- CA2197583A1 CA2197583A1 CA002197583A CA2197583A CA2197583A1 CA 2197583 A1 CA2197583 A1 CA 2197583A1 CA 002197583 A CA002197583 A CA 002197583A CA 2197583 A CA2197583 A CA 2197583A CA 2197583 A1 CA2197583 A1 CA 2197583A1
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- Prior art keywords
- load
- jib
- residual
- aerial lift
- measuring
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- Forklifts And Lifting Vehicles (AREA)
- Jib Cranes (AREA)
Abstract
A residual capacity indicator and load measuring system for aerial lifts of the type having a pair of articulated arms mounted on a revolving turret and having a jib and a bucket provided at a free end of the upper one of the two articulated arms comprises first and second protractors for measuring the respective angles of the upper and lower arms, an angle measuring device for measuring, in any given position of the aerial lift, the angle of the jib, and a reach measuring device for measuring the extension of the jib, all of the data obtained thereby being fed to a micro-processor which determines the load capacity of the lift in a given position thereof. The system also uses strain-gauges to measure the load on the jib.
The micro-processor determines by way of the capacity and jib loads a residual load of the lift.
A display device displays the residual load to the lift operator and an alarm informs the operator of an overload of the lift. The measurements are transmitted to the micro-processor by fiber optic or radio wave technologies and the micro-processor records high residual loads and residual overloads.
The present invention also proposes a method for determining the residual load of the aerial lift.
The micro-processor determines by way of the capacity and jib loads a residual load of the lift.
A display device displays the residual load to the lift operator and an alarm informs the operator of an overload of the lift. The measurements are transmitted to the micro-processor by fiber optic or radio wave technologies and the micro-processor records high residual loads and residual overloads.
The present invention also proposes a method for determining the residual load of the aerial lift.
Description
CAPACITY INDICATOR AND LOAD
MEASURING SYSTEM FOR AERIAL LIFTS
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to aerial lifts and, more particularly, to a load-monitoring system for use with aerial lifts used, for instance, in the maintenance of distribution lines and having a pair of articulated arms and having a jib and a bucket, basket or nacelle provided at a free end of the upper one of the two articulated arms.
MEASURING SYSTEM FOR AERIAL LIFTS
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to aerial lifts and, more particularly, to a load-monitoring system for use with aerial lifts used, for instance, in the maintenance of distribution lines and having a pair of articulated arms and having a jib and a bucket, basket or nacelle provided at a free end of the upper one of the two articulated arms.
2. Description of the Prior Art For many years now, workmen have used aerial lifts in various types of operations related to the maintenance of electrical distribution lines with such aerial lifts having articulated arms for carrying the workmen and for handling various equipment, e.g. transformers, etc. When such distribution transformers are, for instance, involved, the aerial lifts must be able to lift and handle heavy loads. For doing so, the aerial lifts are equipped at the free end of the uppermost arm thereof with a jib assembly adapted with a hydraulic winch. For each type of aerial lift, there are limitations within which it must be operated in order to ensure the safety of the workmen. For instance, the loads carried by the jib assembly can vary and are limited by the configuration of the articulated arms of the aerial lifts.
In the cases of aerial lifts having articulated upper and lower arms, a typical method of operating the aerial lift can presently be as follows. Once the vehicle carrying the aerial lifts has been properly positioned and stabilized with respect to the elevated area that will be worked on, the workman climbs in the bucket provided at the free end of the upper arm which is also provided with a jib that can be displaced longitudinally and can be pivoted to handle and position the load, e.g. transformer, which will be carried thereby by way of a cable and hook assembly operated by a winch mounted on the jib. The weight of the transformer is estimated and, in the position which the articulated arms and the jib will undertake during the installation of the transformer for example to a post, the angles of the upper and lower arms are measured as well as the horizontal span or reach of the jib. A chart established specifically for the aerial lift being used is then consulted using the data retrieved at the level of the aforementioned angles and reach to ensure that the aerial lift can operate safely in the measured positions of the upper and lower arms and of the jib, that is the positions undertaken when the transformer is to be installed. Then, if the aerial lift can safely be used for the particular task previously measured, the arms are retracted to a lower position for allowing the workman to access the bucket and the bucket is then elevated above the transformer which had been positioned close to the post. The transformer is then attached to the hook provided at the end of the electrically insulated cable which is operated by the jib's winch. The transformer is elevated by the winch and then secured to the post.
Obviously, the transformer can be attached to the cable once the bucket is in the functional position thereof which allows the workman to mount the transformer to the post, or the bucket can be gradually displaced by way of the articulated arms towards the working position of the bucket with the transformer being already suspended from the jib.
Typically, the aforementioned chart allows, for given angles of the upper and lower arms and for a given horizontal reach of the jib, the operator to establish the residual load which can be lifted by the jib. If the angles of the articulated arms are varied or if the reach of the jib has to be modified during the operation of the aerial lift, the operator must again refer to the protractors to determine the new angles of the arms and must again determine the reach of the jib before consulting the chart to verify the safety of the new position of the aerial lift or the aerial lift position that the operator intends to adopt. By using such methods, there are many approximations as well as difficulties in monitoring the safety of the aerial lift for all of the positions that it will undertake.
In general, the operator would use such graphic charts to determine the capacity of the aerial lift in view of its position and the load to be elevated thereby would be estimated. No measurements would be collected to determine scientifically and non-subjectively the safety of the operation. The charts are difficult to read which can cause dangerous errors. It is well known that the aerial lifts would be overloaded by lack of knowledge of the weight of the load or equipment being lifted.
There are various methods and devices which have been developed to verify the safety of aerial lifts in their various positions and under various loads or to simplify the computation of the aforementioned residual load.
United States Patent No. 4,861,224 issued on August 29, 1989 to Holmes discloses an aerial lift which includes a sensor for sensing the load 2197~8~
placed on the upper end of the upper boom and the relative position of the upper boom with respect to the horizontal. A device sounds an alarm to indicate that the load on the boom is approaching a maximum load at that relative position of the upper boom. A device is also provided for interrupting the supply of hydraulic fluid to the hydraulic lift cylinders in the event that the load on the boom exceeds a selected load and to prevent the operator from moving the boom to a position in which an overload condition will exist.
United States Patent No. 4,838,381 issued on June 13, 1989 to Michaud et al. discloses a jib assembly which is displaceably attached to an articulated boom which comprises an elongated jib member having an attachment sleeve element secured thereto. A planetary gear reducer having a driving element is coupled to a gear train and is securable inside the boom. The gear train has an output drive gear protruding adjacent to a side wall of the boom.
A drive gear coupling element secured to the jib attachment sleeve meshes with the output drive gear for rotatably connecting the sleeve element closely to the boom side wall so as to reduce stress on the gear coupling caused by the load supported by the jib assembly. The stress forces acting on the support shaft of the bucket associated with the boom is reduced by closely spacing the bucket and the boom.
United States Patent No. 5,076,449 issued on December 31, 1991 to Clutter discloses a lift apparatus provided on a truck and having a boom, a bucket mounted at the upper end of the boom and a mast which has a central longitudinal axis and which can be selectively positioned on the boom. The longitudinal axis of the mast can be oriented at various different angles relative to the boom and the mast can be secured at a selected angle.
Supports provided for limiting the mast's axial movement relative to the boom in the direction of the central longitudinal axis include a hydraulic cylinder which is fixed relative to one of the mast and the boom and which is movable relative to the other of the mast and the boom. Load measurement sensors are included for measuring the axial load experienced by the mast. More particularly, a cooperating piston associated with the cylinder is fixed relative to the other of the mast and the boom and is displaceable relative to the one of the mast and the boom. The piston is received in the cylinder to define a variable volume in which the pressure changes depending upon the relative position of the piston within the cylinder. A
pressure measuring and indicating unit is provided for measuring the pressure in the variable volume, for converting with a scale the measured pressure into an indication of the load experienced by the mast, and for providing an indication of the load.
United States Patent No. 5,263,597 issued on November 23, 1993 to Stewart et al. discloses a crane load detection system which includes an electronic strain-gauge located in series with the deadline of the boom and located adjacent the gantry tie-down of the deadline of the boom. A pendulum potentiometer and transmitter are provided on the boom adjacent its pivot point. A microprocessor is used to solve several triangles using trigonometric functions to calculate the radius of rotation, the actual weight of the load and the percentage of the load as compared to the maximum load limit of the crane.
United States Patent No. 4,532,595 issued on July 30, 1985 to Wilhelm discloses a load monitoring system which comprises a memory to store a number of groups of coefficients of several polynomials of at least the fifth order. The polynomials approximate closely the curves describing the maximum permissible load for various lengths of booms as a function of the boom's inclination or of the horizontal projection of the length thereof, i.e. its reach. A boom-length sensor and a boom-angle sensor provide data which permit a processor to evaluate the permissible maximum load of the boom. The hydraulic pressure of a jack engaging the boom at an intermediate location thereof is used to determine the actual value of the load. This actual value is compared to the permissible maximum load of the boom calculated by the processor and if the latter is exceeded, an alarm is given. The memory is reprogrammable to allow modifications and inclusion of additional parameters.
United States Patent No. 4,216,868 issued on August 12, 1980 to Geppert discloses a crane safe-load indicator which includes one or more absolute encoding digital optical sensors for monitoring various crane parameters, such as slewing angle, boom angle and boom extension or length. A
computer then calculates the percentage of load capacity as a function of the crane's load ratings tables. Each sensor includes a detector having a light emitting element spaced from a light receiving element and an encoder disc mounted for displacement relative to the detector. The encoder disc presents concentric rings of tracks, each made up of opaque and transparent portions in alternation around the ring. By moving the encoder disc relative to the 2197~83 detector, digitally encoded signals are produced which represent the movement of the crane portions being monitored. Since there is no contact between the disc and the detector, there no mechanical wear as opposed to the variable resistors previously used to monitor crane parameters.
United States Patent No. 4,222,491 issued on September 16, 1980 also to Geppert discloses a crane operating aid which includes a pivoted boom and two hydraulic lift rams operating to lift the boom along a given range of operating positions.
Each hydraulic lift ram comprises two fluid-receiving chambers and the rams are moved upwards in response to fluid received in one of the chambers and downwards in response to fluid received in the other one of the chambers. Fluid pressure sensors associated with the fluid-receiving chambers are connected to transducers. An operator interface located adjacent the crane operator provides a total effective crane load signal as a function of the reaction force output signal calculated from the signals fed from the transducers to a logic circuitry.
A Simon-Telelect publication entitled "Simon ELC - Electronic Load Chart" discloses a system which provides the operator of the aerial lift with the a digital readout of the actual weight being lifted by the jib and by the winch of the aerial lift and also indicates the remaining weight that can be lifted in view of the positions of the jib and of the upper boom of the dual-armed aerial lift. This is accomplished by measuring by way of sensors the angle of the upper boom, the angle and extension of the jib and by measuring by way of a load pin the load on the winch line. The measurements are fed to a micro-processor which 2i97583 compares the measured application data to the data which was inputted during the calibration procedure.
The micro-processor thus provides displayed load information to the operator for both load weight and remaining capacity on the basis of the actual boom and jib positions of the aerial lift. The micro-processor can allow certain parameters to be recorded, stored and accessed by authorized personnel. The system activates an audible alarm when the load exceeds the capacity of the aerial lift for specific jib and upper boom positions.
SUMMARY OF THE INVENTION
It is therefore an aim of the present invention to provide an improved load monitoring system for aerial lifts of the type having a pair of articulated arms, and a jib and a bucket provided at a free end of the upper one of the two of articulated arms.
It is also an aim of the present invention to provide an improved load monitoring system for aerial lifts which can determine in any given position of an aerial lift the residual charge of the aerial lift by subtracting the measured load at the jib for a given configuration of the aerial lift from the load capacity thereof.
It is a further aim of the present invention to provide an improved load monitoring system for aerial lifts wherein the load capacity is established by measuring the angles of the upper and lower booms, and the angle of rotation and the extension of the jib, whereas the load measured at the jib is measured by way of a device using strain-gauges.
It is a still further aim of the present invention to provide an improved load monitoring system for aerial lifts wherein the load measured at the jib is not limited to the load on the winch line thereof but to the complete load on the jib, taking into account the loads if other equipments handled or carried by the jib, e.g. conductors of distribution lines.
It is a still further aim of the present invention to provide an improved load monitoring system for aerial lifts which uses for conserving the electrical insulation of the aerial lift a fiber-optic or radio-wave transmission system for transmitting the boom and jib measurements to the micro-processor which computes the load capacity and the jib load to determine the residual jib load.
Therefore, in accordance with the present invention, there is provided a load measuring system for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, comprising first and second angle measuring means adapted to measure respective angular positions respectively of the upper and lower arms, third angle measuring means adapted to measure an angular position of the jib, reach measuring means adapted to measure an extension of the jib, jib load measuring means adapted to measure a load on the jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
2197~8~
Also in accordance with the present invention, there is provided a load measuring method for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, said method comprising the steps of:
a) measuring first, second and third angles defined respectively by the upper arm, the lower arm and the jib in a given position of the aerial lift, and measuring an extension of the jib in said given position;
b) measuring a jib load on the jib;
c) calculating a load capacity of the aerial lift in said given position from said first, second and third angles and from said extensioni and d) determining from said load capacity and from said jib load a residual load of the jig in said given position.
Further in accordance with the present invention, there is provided an aerial lift comprising an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm, a jib mounted to said bucket for handling equipment and a load measuring system, said load measuring system comprising first and second angle measuring means adapted to measure respective angular positions respectively of said upper and lower arms, third angle measuring means adapted to measure an angular position of said jib, reach measuring means adapted to measure an extension of said jib, jib load measuring means adapted to measure a load on said jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which:
Figs. la, lb and lc are schematic perspective views of an aerial lift adapted with a capacity indicator and load measuring system in accordance with the present invention, wherein the drawings respectively show the aerial lift in lower ground-leaving, intermediate and upper operational positions thereof;
Fig. 2 is a schematic perspective view of a jib assembly of the aerial lift of Figs. la to lc, the jib assembly being mounted at a free end of an upper arm of the aerial lift;
Fig. 3 is a schematic elevational view of the upper and lower arms and of the jib assembly of the aerial lift which shows the positions of a pair of protractors on the upper and lower arms and the angles defined between these arms and the horizontal;
Fig. 4 is an elevational view of the jib assembly of the aerial lift which shows the horizontal reach of the jib assembly; and Fig. 5 is a schematic block diagram of the capacity indicator and load measuring system of the present invention.
21g7583 DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, there is illustrated an aerial lift L adapted with a capacity indicator and load measuring system S in accordance with the present invention. Aerial lifts are typically used for the maintenance of electrical distribution lines and the present system S is intended to facilitate and render safer the handling of various loads during such maintenance operations.
Referring to Figs. la to lc, the aerial lift L is mounted to a truck 10 and comprises a pair of articulated arms, namely an upper arm 12 and a lower arm 14, with the upper and lower arms 12 and 14 being pivotally connected one to another at 16. The aerial lift L also comprises a horizontally revolving turret 18 and a bucket 20 provided with a jib assembly 22. More particularly, a lower end of the lower arm 14 is pivotally mounted at 24 to the turret 18 which itself is rotatably mounted to the truck 10. The bucket 20 is mounted to a free end 26 of the upper arm 12 with a free pivot so that the bucket 20 and a workman W carried thereby remain vertical for any given positions of the articulated upper and lower arms 12 and 14, as seen in Figs. la to lc.
As best seen in Fig. 2, the jib assembly 22 comprises an axially extendible and retractable jib 28 operated by a hydraulic cylinder 30 having a reciprocating movement, a pulley system 32 provided at an upper end of the jib 28, a motorized winch 34 including a rotatable drum 36 for operating a winch line 38. The winch 34 in a well known manner can cause the line 38 to wind around or unwind from the drum 36 with the line 38 extending from the drum 36, around the pulley system 32 and downwardly therefrom. At a lower free end of the winch line -38, there is provided an eye 40 and a shackle 42 engaged therein for allowing the jib assembly 22 to handle equipment, such as transformers.
The capacity indicator and load measuring system S of the present invention which is herein adapted to the aerial lift L comprises upper and lower protractors 44 and 46 mounted respectively to the upper and lower arms 12 and 14, as illustrated in Fig. 3, for measuring the respective upper and lower angles 48 and 50 defined respectively by the upper and lower arms 12 and 14, typically relative to the horizontal. The capacity indicator and load measuring system S also comprises a similar angle measuring device (not shown) for determining the relative angle of the jib 28, and an extension measuring device (not shown) for determining a relative axial position of the jib 28. With reference to Fig. 4, the jib extension measuring device typically measures a reach 60 of the jib 28.
The capacity indicator and load measuring system S
further includes a system of strain-gauges (not shown) indifferent to variations in temperature and adapted to determine the load on the jib 28 and not only on the winch line 38. In this preferred embodiment, the load in the bucket 20 is not considered to determine the residual load, although it could be. As the rotational angle of the turret 18 only affects the stability of the truck 10, it is not considered to determine the load capacity, and there already are industry standards governing trucks 10 carrying aerial arms to ensure the stability thereof.
Now referring mainly to Fig. 5, the capacity indicator and load measuring system S is used to determine a residual load 60 of the aerial lift L for any given position thereof and in view of the load at the jib 28. To determine the residual capacity 60 of the capacity indicator and load measuring system S, a load capacity 62 of the aerial lift L must be determined for a given position thereof and a jib load 64 which represents the load at the jib 28 must also be determined. The load capacity 62 is calculated by way of a micro-processor M (see block diagram of Fig. 5) which receives data from the various sensors and, more particularly, the upper arm angle 48 from the upper protractor 44, the lower arm angle 50 from the lower protractor 46, a jib angle 66 from the jib angle measuring device and a jib extension 68 from the jib extension measuring device. The jib load 64 is obtained from the strain-gauges. The residual load 60 is determined by subtracting the jib load 64 from the load capacity 62 of the aerial lift L for the given position thereof at the time of the aforementioned measurements.
The residual load is displayed to the operator of the aerial lift L by a display device 72. If the residual load 60 so calculated by the micro-processor M is above a safe limit thereof (the safe limits of the aerial lift L having been previously determined during calibration of the system S and having been entered in the micro-processor M), an audible and/or visual alarm 74 will be activated. The micro-processor M can be programmed to at least record (see block 76 in Fig.
5) the residual loads 60 which are high and the overloads thereof, i.e. when the jib load 64 surpasses the load capacity 62 of the aerial lift L
in the position thereof for which the data has been obtained and used by the micro-processor M to determine the residual load 60. The date and time of the residual loads 60 so recorded are also recorded by the micro-processor M.
To maintain the electrical insulation of the aerial lift L, a fiber optic or radio wave transmission system 70 is used to transmit the lower arm angle 50 obtained by the lower protractor 46 to the micro-processor M as the latter is located close to the bucket 20.
The capacity indicator and load measuring system S is adapted to operate within a large range of temperatures and is of completely tight construction.
Therefore, the system of the present invention improves the safety of the lift operators and allows the life of the aerial lifts to be extended by accurately and in real time the residual load of the aerial lifts. The present system S also increases the workman productivity as it eliminates the need to refer to written charts. Indeed, the residual load is displayed to the operator in real time and in a clear and simple manner.
In the cases of aerial lifts having articulated upper and lower arms, a typical method of operating the aerial lift can presently be as follows. Once the vehicle carrying the aerial lifts has been properly positioned and stabilized with respect to the elevated area that will be worked on, the workman climbs in the bucket provided at the free end of the upper arm which is also provided with a jib that can be displaced longitudinally and can be pivoted to handle and position the load, e.g. transformer, which will be carried thereby by way of a cable and hook assembly operated by a winch mounted on the jib. The weight of the transformer is estimated and, in the position which the articulated arms and the jib will undertake during the installation of the transformer for example to a post, the angles of the upper and lower arms are measured as well as the horizontal span or reach of the jib. A chart established specifically for the aerial lift being used is then consulted using the data retrieved at the level of the aforementioned angles and reach to ensure that the aerial lift can operate safely in the measured positions of the upper and lower arms and of the jib, that is the positions undertaken when the transformer is to be installed. Then, if the aerial lift can safely be used for the particular task previously measured, the arms are retracted to a lower position for allowing the workman to access the bucket and the bucket is then elevated above the transformer which had been positioned close to the post. The transformer is then attached to the hook provided at the end of the electrically insulated cable which is operated by the jib's winch. The transformer is elevated by the winch and then secured to the post.
Obviously, the transformer can be attached to the cable once the bucket is in the functional position thereof which allows the workman to mount the transformer to the post, or the bucket can be gradually displaced by way of the articulated arms towards the working position of the bucket with the transformer being already suspended from the jib.
Typically, the aforementioned chart allows, for given angles of the upper and lower arms and for a given horizontal reach of the jib, the operator to establish the residual load which can be lifted by the jib. If the angles of the articulated arms are varied or if the reach of the jib has to be modified during the operation of the aerial lift, the operator must again refer to the protractors to determine the new angles of the arms and must again determine the reach of the jib before consulting the chart to verify the safety of the new position of the aerial lift or the aerial lift position that the operator intends to adopt. By using such methods, there are many approximations as well as difficulties in monitoring the safety of the aerial lift for all of the positions that it will undertake.
In general, the operator would use such graphic charts to determine the capacity of the aerial lift in view of its position and the load to be elevated thereby would be estimated. No measurements would be collected to determine scientifically and non-subjectively the safety of the operation. The charts are difficult to read which can cause dangerous errors. It is well known that the aerial lifts would be overloaded by lack of knowledge of the weight of the load or equipment being lifted.
There are various methods and devices which have been developed to verify the safety of aerial lifts in their various positions and under various loads or to simplify the computation of the aforementioned residual load.
United States Patent No. 4,861,224 issued on August 29, 1989 to Holmes discloses an aerial lift which includes a sensor for sensing the load 2197~8~
placed on the upper end of the upper boom and the relative position of the upper boom with respect to the horizontal. A device sounds an alarm to indicate that the load on the boom is approaching a maximum load at that relative position of the upper boom. A device is also provided for interrupting the supply of hydraulic fluid to the hydraulic lift cylinders in the event that the load on the boom exceeds a selected load and to prevent the operator from moving the boom to a position in which an overload condition will exist.
United States Patent No. 4,838,381 issued on June 13, 1989 to Michaud et al. discloses a jib assembly which is displaceably attached to an articulated boom which comprises an elongated jib member having an attachment sleeve element secured thereto. A planetary gear reducer having a driving element is coupled to a gear train and is securable inside the boom. The gear train has an output drive gear protruding adjacent to a side wall of the boom.
A drive gear coupling element secured to the jib attachment sleeve meshes with the output drive gear for rotatably connecting the sleeve element closely to the boom side wall so as to reduce stress on the gear coupling caused by the load supported by the jib assembly. The stress forces acting on the support shaft of the bucket associated with the boom is reduced by closely spacing the bucket and the boom.
United States Patent No. 5,076,449 issued on December 31, 1991 to Clutter discloses a lift apparatus provided on a truck and having a boom, a bucket mounted at the upper end of the boom and a mast which has a central longitudinal axis and which can be selectively positioned on the boom. The longitudinal axis of the mast can be oriented at various different angles relative to the boom and the mast can be secured at a selected angle.
Supports provided for limiting the mast's axial movement relative to the boom in the direction of the central longitudinal axis include a hydraulic cylinder which is fixed relative to one of the mast and the boom and which is movable relative to the other of the mast and the boom. Load measurement sensors are included for measuring the axial load experienced by the mast. More particularly, a cooperating piston associated with the cylinder is fixed relative to the other of the mast and the boom and is displaceable relative to the one of the mast and the boom. The piston is received in the cylinder to define a variable volume in which the pressure changes depending upon the relative position of the piston within the cylinder. A
pressure measuring and indicating unit is provided for measuring the pressure in the variable volume, for converting with a scale the measured pressure into an indication of the load experienced by the mast, and for providing an indication of the load.
United States Patent No. 5,263,597 issued on November 23, 1993 to Stewart et al. discloses a crane load detection system which includes an electronic strain-gauge located in series with the deadline of the boom and located adjacent the gantry tie-down of the deadline of the boom. A pendulum potentiometer and transmitter are provided on the boom adjacent its pivot point. A microprocessor is used to solve several triangles using trigonometric functions to calculate the radius of rotation, the actual weight of the load and the percentage of the load as compared to the maximum load limit of the crane.
United States Patent No. 4,532,595 issued on July 30, 1985 to Wilhelm discloses a load monitoring system which comprises a memory to store a number of groups of coefficients of several polynomials of at least the fifth order. The polynomials approximate closely the curves describing the maximum permissible load for various lengths of booms as a function of the boom's inclination or of the horizontal projection of the length thereof, i.e. its reach. A boom-length sensor and a boom-angle sensor provide data which permit a processor to evaluate the permissible maximum load of the boom. The hydraulic pressure of a jack engaging the boom at an intermediate location thereof is used to determine the actual value of the load. This actual value is compared to the permissible maximum load of the boom calculated by the processor and if the latter is exceeded, an alarm is given. The memory is reprogrammable to allow modifications and inclusion of additional parameters.
United States Patent No. 4,216,868 issued on August 12, 1980 to Geppert discloses a crane safe-load indicator which includes one or more absolute encoding digital optical sensors for monitoring various crane parameters, such as slewing angle, boom angle and boom extension or length. A
computer then calculates the percentage of load capacity as a function of the crane's load ratings tables. Each sensor includes a detector having a light emitting element spaced from a light receiving element and an encoder disc mounted for displacement relative to the detector. The encoder disc presents concentric rings of tracks, each made up of opaque and transparent portions in alternation around the ring. By moving the encoder disc relative to the 2197~83 detector, digitally encoded signals are produced which represent the movement of the crane portions being monitored. Since there is no contact between the disc and the detector, there no mechanical wear as opposed to the variable resistors previously used to monitor crane parameters.
United States Patent No. 4,222,491 issued on September 16, 1980 also to Geppert discloses a crane operating aid which includes a pivoted boom and two hydraulic lift rams operating to lift the boom along a given range of operating positions.
Each hydraulic lift ram comprises two fluid-receiving chambers and the rams are moved upwards in response to fluid received in one of the chambers and downwards in response to fluid received in the other one of the chambers. Fluid pressure sensors associated with the fluid-receiving chambers are connected to transducers. An operator interface located adjacent the crane operator provides a total effective crane load signal as a function of the reaction force output signal calculated from the signals fed from the transducers to a logic circuitry.
A Simon-Telelect publication entitled "Simon ELC - Electronic Load Chart" discloses a system which provides the operator of the aerial lift with the a digital readout of the actual weight being lifted by the jib and by the winch of the aerial lift and also indicates the remaining weight that can be lifted in view of the positions of the jib and of the upper boom of the dual-armed aerial lift. This is accomplished by measuring by way of sensors the angle of the upper boom, the angle and extension of the jib and by measuring by way of a load pin the load on the winch line. The measurements are fed to a micro-processor which 2i97583 compares the measured application data to the data which was inputted during the calibration procedure.
The micro-processor thus provides displayed load information to the operator for both load weight and remaining capacity on the basis of the actual boom and jib positions of the aerial lift. The micro-processor can allow certain parameters to be recorded, stored and accessed by authorized personnel. The system activates an audible alarm when the load exceeds the capacity of the aerial lift for specific jib and upper boom positions.
SUMMARY OF THE INVENTION
It is therefore an aim of the present invention to provide an improved load monitoring system for aerial lifts of the type having a pair of articulated arms, and a jib and a bucket provided at a free end of the upper one of the two of articulated arms.
It is also an aim of the present invention to provide an improved load monitoring system for aerial lifts which can determine in any given position of an aerial lift the residual charge of the aerial lift by subtracting the measured load at the jib for a given configuration of the aerial lift from the load capacity thereof.
It is a further aim of the present invention to provide an improved load monitoring system for aerial lifts wherein the load capacity is established by measuring the angles of the upper and lower booms, and the angle of rotation and the extension of the jib, whereas the load measured at the jib is measured by way of a device using strain-gauges.
It is a still further aim of the present invention to provide an improved load monitoring system for aerial lifts wherein the load measured at the jib is not limited to the load on the winch line thereof but to the complete load on the jib, taking into account the loads if other equipments handled or carried by the jib, e.g. conductors of distribution lines.
It is a still further aim of the present invention to provide an improved load monitoring system for aerial lifts which uses for conserving the electrical insulation of the aerial lift a fiber-optic or radio-wave transmission system for transmitting the boom and jib measurements to the micro-processor which computes the load capacity and the jib load to determine the residual jib load.
Therefore, in accordance with the present invention, there is provided a load measuring system for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, comprising first and second angle measuring means adapted to measure respective angular positions respectively of the upper and lower arms, third angle measuring means adapted to measure an angular position of the jib, reach measuring means adapted to measure an extension of the jib, jib load measuring means adapted to measure a load on the jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
2197~8~
Also in accordance with the present invention, there is provided a load measuring method for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, said method comprising the steps of:
a) measuring first, second and third angles defined respectively by the upper arm, the lower arm and the jib in a given position of the aerial lift, and measuring an extension of the jib in said given position;
b) measuring a jib load on the jib;
c) calculating a load capacity of the aerial lift in said given position from said first, second and third angles and from said extensioni and d) determining from said load capacity and from said jib load a residual load of the jig in said given position.
Further in accordance with the present invention, there is provided an aerial lift comprising an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm, a jib mounted to said bucket for handling equipment and a load measuring system, said load measuring system comprising first and second angle measuring means adapted to measure respective angular positions respectively of said upper and lower arms, third angle measuring means adapted to measure an angular position of said jib, reach measuring means adapted to measure an extension of said jib, jib load measuring means adapted to measure a load on said jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which:
Figs. la, lb and lc are schematic perspective views of an aerial lift adapted with a capacity indicator and load measuring system in accordance with the present invention, wherein the drawings respectively show the aerial lift in lower ground-leaving, intermediate and upper operational positions thereof;
Fig. 2 is a schematic perspective view of a jib assembly of the aerial lift of Figs. la to lc, the jib assembly being mounted at a free end of an upper arm of the aerial lift;
Fig. 3 is a schematic elevational view of the upper and lower arms and of the jib assembly of the aerial lift which shows the positions of a pair of protractors on the upper and lower arms and the angles defined between these arms and the horizontal;
Fig. 4 is an elevational view of the jib assembly of the aerial lift which shows the horizontal reach of the jib assembly; and Fig. 5 is a schematic block diagram of the capacity indicator and load measuring system of the present invention.
21g7583 DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, there is illustrated an aerial lift L adapted with a capacity indicator and load measuring system S in accordance with the present invention. Aerial lifts are typically used for the maintenance of electrical distribution lines and the present system S is intended to facilitate and render safer the handling of various loads during such maintenance operations.
Referring to Figs. la to lc, the aerial lift L is mounted to a truck 10 and comprises a pair of articulated arms, namely an upper arm 12 and a lower arm 14, with the upper and lower arms 12 and 14 being pivotally connected one to another at 16. The aerial lift L also comprises a horizontally revolving turret 18 and a bucket 20 provided with a jib assembly 22. More particularly, a lower end of the lower arm 14 is pivotally mounted at 24 to the turret 18 which itself is rotatably mounted to the truck 10. The bucket 20 is mounted to a free end 26 of the upper arm 12 with a free pivot so that the bucket 20 and a workman W carried thereby remain vertical for any given positions of the articulated upper and lower arms 12 and 14, as seen in Figs. la to lc.
As best seen in Fig. 2, the jib assembly 22 comprises an axially extendible and retractable jib 28 operated by a hydraulic cylinder 30 having a reciprocating movement, a pulley system 32 provided at an upper end of the jib 28, a motorized winch 34 including a rotatable drum 36 for operating a winch line 38. The winch 34 in a well known manner can cause the line 38 to wind around or unwind from the drum 36 with the line 38 extending from the drum 36, around the pulley system 32 and downwardly therefrom. At a lower free end of the winch line -38, there is provided an eye 40 and a shackle 42 engaged therein for allowing the jib assembly 22 to handle equipment, such as transformers.
The capacity indicator and load measuring system S of the present invention which is herein adapted to the aerial lift L comprises upper and lower protractors 44 and 46 mounted respectively to the upper and lower arms 12 and 14, as illustrated in Fig. 3, for measuring the respective upper and lower angles 48 and 50 defined respectively by the upper and lower arms 12 and 14, typically relative to the horizontal. The capacity indicator and load measuring system S also comprises a similar angle measuring device (not shown) for determining the relative angle of the jib 28, and an extension measuring device (not shown) for determining a relative axial position of the jib 28. With reference to Fig. 4, the jib extension measuring device typically measures a reach 60 of the jib 28.
The capacity indicator and load measuring system S
further includes a system of strain-gauges (not shown) indifferent to variations in temperature and adapted to determine the load on the jib 28 and not only on the winch line 38. In this preferred embodiment, the load in the bucket 20 is not considered to determine the residual load, although it could be. As the rotational angle of the turret 18 only affects the stability of the truck 10, it is not considered to determine the load capacity, and there already are industry standards governing trucks 10 carrying aerial arms to ensure the stability thereof.
Now referring mainly to Fig. 5, the capacity indicator and load measuring system S is used to determine a residual load 60 of the aerial lift L for any given position thereof and in view of the load at the jib 28. To determine the residual capacity 60 of the capacity indicator and load measuring system S, a load capacity 62 of the aerial lift L must be determined for a given position thereof and a jib load 64 which represents the load at the jib 28 must also be determined. The load capacity 62 is calculated by way of a micro-processor M (see block diagram of Fig. 5) which receives data from the various sensors and, more particularly, the upper arm angle 48 from the upper protractor 44, the lower arm angle 50 from the lower protractor 46, a jib angle 66 from the jib angle measuring device and a jib extension 68 from the jib extension measuring device. The jib load 64 is obtained from the strain-gauges. The residual load 60 is determined by subtracting the jib load 64 from the load capacity 62 of the aerial lift L for the given position thereof at the time of the aforementioned measurements.
The residual load is displayed to the operator of the aerial lift L by a display device 72. If the residual load 60 so calculated by the micro-processor M is above a safe limit thereof (the safe limits of the aerial lift L having been previously determined during calibration of the system S and having been entered in the micro-processor M), an audible and/or visual alarm 74 will be activated. The micro-processor M can be programmed to at least record (see block 76 in Fig.
5) the residual loads 60 which are high and the overloads thereof, i.e. when the jib load 64 surpasses the load capacity 62 of the aerial lift L
in the position thereof for which the data has been obtained and used by the micro-processor M to determine the residual load 60. The date and time of the residual loads 60 so recorded are also recorded by the micro-processor M.
To maintain the electrical insulation of the aerial lift L, a fiber optic or radio wave transmission system 70 is used to transmit the lower arm angle 50 obtained by the lower protractor 46 to the micro-processor M as the latter is located close to the bucket 20.
The capacity indicator and load measuring system S is adapted to operate within a large range of temperatures and is of completely tight construction.
Therefore, the system of the present invention improves the safety of the lift operators and allows the life of the aerial lifts to be extended by accurately and in real time the residual load of the aerial lifts. The present system S also increases the workman productivity as it eliminates the need to refer to written charts. Indeed, the residual load is displayed to the operator in real time and in a clear and simple manner.
Claims (20)
1. A load measuring system for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, comprising first and second angle measuring means adapted to measure respective angular positions respectively of the upper and lower arms, third angle measuring means adapted to measure an angular position of the jib, reach measuring means adapted to measure an extension of the jib, jib load measuring means adapted to measure a load on the jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
2. A load measuring system as defined in Claim 1, wherein said jib load measuring means measures not only a line load on a cable of a winch means of said jib but also other loads carried by said jib.
3. A load measuring system as defined in Claim 1, wherein a display device is provided for displaying to an operator of the aerial lift said residual load.
4. A load measuring system as defined in Claim 1, wherein said jib load measuring means comprise strain-gauge means.
5. A load measuring system as defined in Claim 1, wherein a display device is provided for displaying to an operator of the aerial lift said residual load.
6. A load measuring system as defined in Claim 1, wherein alarm means are provided to inform an operator of the aerial lift of an overload thereof.
7. A load measuring system as defined in Claim 1, further comprising transmission means for transmitting said measurements obtained from said first, second and third angle measuring means, from said reach measuring means and from said jib load measuring means to said micro-processor means.
8. A load measuring system as defined in Claim 1, further comprising transmission means including at least one of fiber optic means and radio wave means for transmitting any measurement obtained from said second angle measuring means to said micro-processor means while preserving an electrical insulation of the aerial lift.
9. A load measuring system as defined in Claim 1, wherein said micro-processor means is adapted to record at least one of high residual loads and residual overloads.
10. A load measuring method for aerial lifts and the like of the type having an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm and a jib mounted to the bucket for handling equipment, said method comprising the steps of:
a) measuring first, second and third angles defined respectively by the upper arm, the lower arm and the jib in a given position of the aerial lift, and measuring an extension of the jib in said given position;
b) measuring a jib load on the jib;
c) calculating a load capacity of the aerial lift in said given position from said first, second and third angles and from said extension; and d) determining from said load capacity and from said jib load a residual load of the jig in said given position.
a) measuring first, second and third angles defined respectively by the upper arm, the lower arm and the jib in a given position of the aerial lift, and measuring an extension of the jib in said given position;
b) measuring a jib load on the jib;
c) calculating a load capacity of the aerial lift in said given position from said first, second and third angles and from said extension; and d) determining from said load capacity and from said jib load a residual load of the jig in said given position.
11. A load measuring method as defined in Claim 10, wherein in step b) there is measured not only a winch line load of the jib means of said jib but also other loads carried by the jib.
12. A load measuring method as defined in Claim 10, wherein after step d) said residual load is displayed to an operator of the aerial lift.
13. A load measuring method as defined in Claim 10, wherein alarm means are provided to inform an operator of the aerial lift of an overload thereof following the determination in step d) of said residual load.
14. A load measuring method as defined in Claim 10, wherein after step d) said residual load is recorded at least in cases of high residual loads and residual overloads.
15. An aerial lift comprising an upper arm and a lower arm articulated to one another, a bucket provided at a free end of the upper articulated arm, a jib mounted to said bucket for handling equipment and a load measuring system, said load measuring system comprising first and second angle measuring means adapted to measure respective angular positions respectively of said upper and lower arms, third angle measuring means adapted to measure an angular position of said jib, reach measuring means adapted to measure an extension of said jib, jib load measuring means adapted to measure a load on said jib, micro-processor means adapted to determine a load capacity of the aerial lift for any given configuration thereof on the basis of measurements obtained from said first, second and third angle measuring means and from said reach measuring means, and further adapted to determine from said load capacity and a jig load obtained from said jib load measuring means a residual load of the jig in said given configuration.
16. An aerial lift as defined in Claim 15, wherein said jib load measuring means measures not only a line load on a cable of a winch means of said jib but also other loads carried by said jib.
17. An aerial lift as defined in Claim 15, wherein said load measuring system further comprises a display device for displaying to an operator of the aerial lift said residual load.
18. An aerial lift as defined in Claim 15, wherein said load measuring system further comprises alarm means for informing an operator of the aerial lift of an overload thereof, and wherein said micro-processor means is adapted to record at least one of high residual loads and residual overloads.
19. An aerial lift as defined in Claim 15, further comprising transmission means for transmitting said measurements obtained from said first, second and third angle measuring means, from said reach measuring means and from said jib load measuring means to said micro-processor means.
20. An aerial lift as defined in Claim 15, further comprising transmission means including at least one of fiber optic means and radio wave means for transmitting any measurement obtained from said second angle measuring means to said micro-processor means while preserving an electrical insulation of the aerial lift.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US61546596A | 1996-03-14 | 1996-03-14 | |
| US08/615,465 | 1996-03-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2197583A1 true CA2197583A1 (en) | 1997-09-15 |
Family
ID=24465484
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002197583A Abandoned CA2197583A1 (en) | 1996-03-14 | 1997-02-14 | Capacity indicator and load measuring system for arial lifts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2197583A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022266454A3 (en) * | 2021-06-17 | 2023-02-02 | Time Manufacturing Company | Aerial lift slope adjustment system |
-
1997
- 1997-02-14 CA CA002197583A patent/CA2197583A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022266454A3 (en) * | 2021-06-17 | 2023-02-02 | Time Manufacturing Company | Aerial lift slope adjustment system |
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