DE29903815U1 - Device for controlling the relative stroke of a lifting device attacking objects - Google Patents

Description

Herz System and Plant Technology GmbH, Industriestr. 3-5, D29499 Zernien

Device for controlling the relative stroke of a lifting device acting on objects

The invention relates to a device for controlling the relative stroke of a lifting device that engages objects, comprising a measuring device that is arranged in a fixed position on the lifting device, an electrical control device connected thereto and a sensing element that is arranged so that it can slide relative to the measuring device and that moves as a result of contact with a respective object, with a plurality of sliding positions of the sensing element being assigned pre-settable switching points of the measuring device for controlling the lifting drive. Such control devices are provided for detecting the height position of the lifting device in order to pick up and support parts of any kind, in particular on different level surfaces, for example in a stack. In particular, pneumatic, hydraulic and electrical lifting drives can be controlled. The sensing element is usually provided as a sensing plunger that is moved when it hits an object to be grasped and when it is separated from the lifting device. This ensures in particular that the falling of an object and the reaching of an emergency stop state can be detected. A switching point of the sliding path is also usually used to trigger an adapted creeping motion when the lifting device approaches an object to be grasped.

A known, commonly used device comprises a mechanical metal tube plunger, which runs in a guide and is provided at its upper end with a switching flag formed by a metal tube. Several inductively operating initiators are positioned along the sliding path of the switching flag, their height position and their adjustment. When the switching flag passes the respective initiator, an associated function is triggered by means of an electrical control, which controls the lifting drive. The known device has a number of disadvantages. It comprises a plurality of relatively massive components, in particular the metal tube switching flags and the inductive initiators, which can only be arranged in very limited numbers and, due to their dimensions, only at relatively large distances from one another. This leads to problems, particularly with plunger movements at high speed. In order to reliably carry out a switching process when passing the initiator, the metal tube switching flag must be relatively long. This makes adjustment processes and

-possibilities are made considerably more difficult or limited. A relatively long metal tube switching flag and/or minimum distances that must be observed often lead to malfunctions and consequently increase the susceptibility to failure. The known device is also subject to relatively high mechanical wear, which is caused in particular by wear on the tappet guide.

This also significantly affects the reliability and speed of operation. Due to the relatively long and therefore heavy metal tube switching flags, relatively small differences in height cannot be detected, so that the known device cannot be satisfactorily adapted and optimized for use on objects with different material thicknesses.

In contrast, the invention is based on the object of creating a control device for the lifting of a lifting device that acts on objects, which is to be improved in terms of the setting and operating options as well as the functional reliability, the design and the adaptability.

According to the invention, these objectives are achieved in conjunction with the features of the device mentioned at the beginning in that the measuring device is equipped with a measuring section corresponding to the effective maximum sliding path of the probe element, which continuously records the sliding positions of the probe element over its area, and in that an electronic setting and evaluation circuit is connected to the measuring device, by means of which at least one group of switching points corresponding to predeterminable, desired sliding positions can be set for controlling the lifting drive. By means of the continuously, evenly measured distance in conjunction with the setting/evaluation circuit, practically every sliding position of the probe element can be recorded both on a very small and a relatively large sliding distance, whereby the setting/evaluation circuit is provided in order to assign a plurality of electronic markings to the measuring section as desired, which form switching points for controlling the lifting drive. As a result of the continuous distance measurement, switching points can be placed practically as closely as desired, in as large a number as desired and even overlapping. The desired or selected switching points are assigned switching functions using conventional electronic means. In this way, switching sequences and controls can be carried out using electronic means alone, namely the programming of the electronic setting/evaluation circuit, while avoiding mechanical settings. Conventional mechanical settings and adjustments are no longer necessary. The positioning accuracy of the electronic switching points is particularly high, so that special adjustment work during operation is not necessary.

Operation is eliminated. The control device can be exchanged quickly and easily for replacement or repair, whereby the setting and program data of the replacement device can be transferred precisely and easily to the replaced device. The switching time required to initiate creeping travel, particularly in high-speed operation, can be freely set in every area of the measuring section by selecting an adapted sequence of electronic switching points that can be set practically as close together as desired. In addition, the device according to the invention is characterized by small component dimensions, which lead to a light-weight arrangement and, as a result, low-wear and smooth-running for the sliding parts. The constant path detection results in real-value detection, which can be used to adjust the lifting drive depending on the path of the lifting device in order to adapt to the type and location of the object to be transported. Since such a process can be carried out at high speed thanks to the measuring arrangement according to the invention, cycle times are significantly reduced in long-term operation. Specifying and setting the switching points using the electronic setting and evaluation device also provides special security against accidental manipulation and adjustment. It should also be pointed out that the control device according to the invention can be used in gripping and lifting devices of various types and for picking up or supporting parts of very different dimensions due to the elimination of conventionally solid and heavy components and due to universal, precise and reproducible electronic settings. In particular, the scanning can be carried out very sensitively and on particularly soft, deformable and/or damage-sensitive material surfaces or parts. In old systems, the device according to the invention can be easily retrofitted, in particular without interfering with the existing drive control. By using lifting devices equipped with the control device according to the invention, the operation of production or processing systems, which should be operated in three-shift operation if possible, can be utilized considerably better. Overall, the device according to the invention contributes significantly to increasing operational reliability, increasing the number of units produced, converting to other products and reducing maintenance work, whereby in particular cycle times and set-up times are shortened, maintenance work is avoided, downtimes are increased and operating costs are reduced.

In a particularly advantageous embodiment, the measuring device is designed as an electronic device with a sensor that is arranged along the entire sliding path of the

The sensing element detects the sliding positions continuously and without contact in such a way that it exerts a physical influence on the electronic measuring device by means of a magnetic field. This makes it particularly easy and practical to achieve that a part that influences the measuring device and is connected to the sensing element can be made very small and largely independent of the sliding speed and switching point distances.

The sensing element can be designed particularly conveniently and advantageously as a plunger sensing element in the form of a pin-like thin rod. This is particularly light in weight and allows very precise local sensing, particularly on soft surfaces.

The probe element is expediently arranged with an associated measuring sensor on a freely movable, easily moving carriage, which is held so as to be slidable along the measuring section in a sliding guide preferably arranged on the measuring device.

It is particularly advantageous to make the preferably pin-like sensing element flexible in the direction transverse to its extension against spring-elastic restoring force. It can be expediently formed by a tension spring with its windings lying against one another, for example by a commercially available V2A tension spring, but also by other flexible materials such as hard rubber or suitable plastics. Such a flexible sensing element moves to the side when it hits an obstacle from the side, so that it is protected against mechanical destruction.

A particularly advantageous and preferred embodiment of the invention is that the measuring device comprises an ultrasonic measuring device with a magnet that influences the travel time of an ultrasonic wave, where the magnet forms the measuring sensor of the probe element and is mounted so that it can slide along the measuring path. Such an ultrasonic distance measuring device, which is available as such as a commercially available electronic component, allows the control device according to the invention to be designed in a particularly simple manner with contactless, continuous measurement.

The subclaims are directed to the above-mentioned and further expedient and advantageous embodiments of the invention, and particularly expedient and advantageous embodiments or possibilities of the inventions are explained in the following description of the invention.

The embodiments shown in the schematic drawing are described in more detail. They show

Fig. 1 to 3 in schematic side view a with an inventive

lifting device equipped with a control device in

starting position (Fig. 1), approach position (Fig. 2) and gripping position (Fig. 3) and

Fig. 4 in schematic plan view the measuring device with probe element

in the embodiment of a device according to the invention.

A lifting device shown in Fig. 1 to 3 comprises a lifting drive 4 in the form of an electric motor, which is fixedly arranged on a machine frame (not shown), and a lifting device 3 which can be moved back and forth in the vertical direction with the lifting device. This has a support 32 which extends long in the vertical direction, which is held in a guide (not shown) and to which the lifting drive 4 engages with conventional mechanical engagement means. The support 32 is rigidly connected at its lower end to a horizontally extending portal support beam 33.

A gripping device 31 is arranged at each end of the support beam 33. In the exemplary embodiment, the gripping element 31 is formed by a pneumatically operated bellows-like suction cup, which is held against the support beam 33 in an ejecting manner against spring force. By lowering the lifting device 3, the two gripping elements 31 grip flat objects lying in the stack 5, which are kept ready on a pallet 6. In the exemplary embodiment, these are carpet mats 51 in the form of panels or tiles, which are to be removed from the stack 5 one after the other as the stack height decreases. Instead of the suction cup grippers, other grippers such as magnetic or clamp grippers can be provided.

A control device 1 according to the invention is arranged on the support beam 33. This comprises a distance measuring device 11 extending parallel to the carrier 32 in the vertical lifting direction, which is arranged in a fixed position on the support beam 33, a setting and evaluation circuit device 12 electrically connected to the device 11 and a control device 13 electrically connected to this and to the lifting drive 4.

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As can be seen from Fig. 4, the measuring device 11 has a cuboid-shaped, vertically extending rod housing 17. On a vertically extending longitudinal side of the rod housing 17 extends a sliding guide 14, shown only in dashed lines in Figs. 1 to 3, in the form of a U-shaped rail, which is open in the vertical direction with a continuous longitudinal slot. A measuring carriage 15 engages in the rail guide 14, which comprises a sliding element 151 held captive in the rail 14. For example, it is a loose and freely slidable plate that supports the carriage body. At the lower end of the housing 17 facing the stack 5, the rail guide 14 is closed with a base 141, which holds the carriage 15 in its lowest position.

The upper end of a vertically extending probe element 2 in the form of a pin-like thin rod 21 is firmly connected to the slide 15. The pin rod 21 is expediently formed by a flexible helical spring with adjacent turns, so that the rod is stiff in the axial direction but can flexibly deviate in the transverse direction. It is particularly expedient for the rod 21 to be provided with a spring-elastic element ensuring the flexibility mentioned only in the area of the connection point with the slide 15.

The rod 21 forms a plunger probe which, in the raised state of the lifting device 3 shown in Fig. 1, projects below a horizontal plane 30 determined by the gripping surfaces of the gripping elements 31. As a result, the gripping elements 31 and the probe element 2 are arranged and held relative to one another in such a way that the probe head 22 of the probe element 2 comes into contact with the object 51 before the gripping elements 31 come into gripping connection with the mat 51.

The path measuring device 11 has a measuring section 110 that runs along the vertical length of the rail guide 14. It forms the effective maximum sliding path of the probe element 2, over which the slide 15 can be lifted from its lower position in Fig. 1 to a maximum upper position under weight. In a particularly preferred embodiment, the measuring device 11 is formed by an electronic magnetic ultrasonic wave measuring device, which is available as such as a commercially available measuring device. A magnet 16 (not shown in detail) that works as a measuring sensor is embedded in the measuring slide 15. Within the measuring device

An ultrasonic wave is generated in the housing 17, the travel time of which is changed depending on the position of the magnet 16. As a result, the travel time changes of the ultrasonic wave represent the positions of the measuring carriage 15 along the measuring section 110. In this way, the current position of the carriage 15 and thus of the probe element 2 is recorded continuously, i.e. evenly, but also continuously.

The setting and evaluation circuit 12 is equipped with a display and keyboard, although this is not shown. The circuit 12 is set and monitored for operation of the device using these usual display and control elements. The circuit 12 comprises setting and evaluation electronics equipped with storage means and a microprocessor. Just a few, but also several hundred, path switching data can be stored in the form of switching points. For example, it is easily possible to assign three hundred path switching points to a measuring section 110 with a length of 10 cm, which can be stored using assigned programs that can be stored using the circuit 12. For example, according to the invention it is particularly possible to provide a variety of programs from one program with, for example, 300 switching points to 15 programs with 20 switching points. The continuous path measurement results in an electrical comparison of the measured position with the set switching point positions, which are activated if they match.

The setting and evaluation circuit 12 can also conveniently form the direct control for the motor drive and/or elements not shown, such as valves or the like. The setting and evaluation circuit is conveniently equipped with circuit and program elements that carry out error and fault detection and evaluation. Thus, with the measuring arrangement according to the invention, it is easily possible to provide, for example, error messages when settings exceed the measuring range and to carry out fault messages and, if necessary, process interruptions when the probe element 2 is not working properly, e.g. due to a faulty sensor 16 and/or electrical connection faults.

Using Fig. 1 to 3, the exemplary embodiment describes the operation with a group of essentially four switching points I to IV. Each switching point is determined by its electronically preset height position along the measuring section 110.

In Fig. 1, the lifting device 3 is in the raised starting position at a distance Al from the level of the uppermost mat 51 to be removed from the stack 5. The probe element measuring carriage 15 assumes the lower stop position, which is assigned a switching point I. In this switching state, which is specified and evaluated by the electronic control and evaluation circuit 12 to control the drive 4, the lifting device 3 is moved downwards at maximum speed.

After traveling the distance a1, the sensing element 2 hits the mat 51 with its sensing head 22, so that it is lifted when the lifting device 3 continues to move downwards until the measuring carriage 15 reaches the position shown in Fig. 2, which is assigned to the switching point Π. In this state, the suction cups of the grippers 31 may already have touched the surface of the mat 51. When the switching point Π is reached, the lifting device 3 starts to creep in order to establish the suction connection to the mat 51 with increasing braking in interaction with the 31 suction grippers retreating against the springs 310. The portal beam 33 is then at a distance A2 from the mat surface and at a distance B2 from the stationary drive device. It is particularly advantageous that instead of the switching point II, a switching path II can be provided, which is formed by a sequence of switching points, in particular a switch-on point and a switch-off point. This creates a switching point that responds reliably even when the carriage 15 is traveling at high speed.

During creep travel, the portal beam 33 traverses the section A2 - A3, whereby the sensing element carriage 15 reaches the position shown in Fig. 3, which is determined by the electronic switching point HI. When this switching point is reached, a program is triggered that switches off the drive 4 through the circuits 12, 13, so that the device is in a stop position in which the grippers 31 firmly grip the mat 51 by completely establishing the suction connection. As can also be seen from Fig. 3, a position above the switching point λΠ is determined by a further switching point IV, which is assigned the function of an emergency stop. If the stop position λΠ is exceeded due to a defect, an emergency shutdown is triggered when the switching point IV becomes effective.

Starting from the gripping position shown in Fig. 3, the drive 4 is reversed by its drive control so that the lifting device 3 lifts the mat 51 from the stack 5. The

The lifting device can then be moved laterally in the direction V in the conventional manner, in order to convey the mat 51 into a production or processing facility and deposit it there.

When the lifting device 3 with the mat 51 is lifted from the stack 5, the gripper springs 310 can be relaxed again while maintaining the suction connection, whereby the sensing element slide 15 reaches a position below the switching point EE. If the mat falls off the grippers 31 due to an irregularity, the downward movement of the sensing element 2 is released and the measuring slide 15 then reaches the starting position of Fig. 1. In this state, by activating the switching point I depending on the operating position of the lifting device, it can be switched off with a fault message or a repeated stroke can be triggered to pick up the fallen mat.

To bring the lifting device λ or the mat 51 closer to a storage area to be picked up, e.g. a conveyor belt, the control device 1 is prepared and set so that the storage process again takes place at a crawling speed with a decreasing speed until it comes to a standstill, whereby the suction grippers 31 are then switched to ineffective. These processes are also initiated and ended with preset, assigned switching points along the path 110 of the measuring device 11, whereby each electronic switching point in conjunction with further specified parameters triggers or ends an associated control program for the drive control that is loaded into the device 1. It should be noted here that the lifting drive is also controlled by standard direct measurements on the drive motor that are not described here, whereby the lifting device is moved in particular to fixed, specified positions. Although such functions can in principle also be carried out by the control device according to the invention, this essentially concerns the drive control by tactile contact of the sensing element with the object to be conveyed.

Of course, a lifting device equipped with the control device according to the invention can also be used, for example, to remove objects from a level of constant height, e.g. a conveyor belt. It is important that the sliding path of the sensing element can be assigned to practically any number of switching points using simple and tamper-proof setting means in the desired arrangement and density or switching point length, whereby the activation of the switching points triggers individual programs, for example fifteen in number, which can be stored in the electronic device, for the drive control.

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It can be seen that the lifting device equipped with the control device according to the invention can be individually adjusted and used for a variety of applications.

Claims (13)

Expectations: 1. Device (1) for controlling the relative stroke of a lifting device (3) acting on objects (51), comprising a measuring device (11) arranged in a fixed position on the lifting device (3), an electrical control device (13) connected thereto and a sensing element (2) arranged so as to be movable relative to the measuring device (11) and which moves as a result of touch contact (11) with a respective object (51), wherein a plurality of sliding positions of the sensing element (2) are assigned presettable switching points of the measuring device (11) for controlling the lifting drive (4), characterized in that the measuring device (11) is equipped with a measuring section (110) corresponding to the effective maximum sliding path of the sensing element (2) and continuously detecting the sliding positions of the sensing element over its area, and in that an electronic setting and evaluation circuit (12) is connected to the measuring device (11), by means of which at least one group of predeterminable switching points (I-IV) corresponding to desired sliding positions can be set for controlling the lifting drive (4). 2. Device according to claim 1, characterized in that the measuring device (11) is formed by an electronic measuring device with a measuring sensor (16) arranged on the probe element, which acts electronically and thus contactlessly on the measuring device (11) for measuring detection. 3. Device according to claim 2, characterized in that the measuring device (11) comprises an ultrasonic measuring device with a magnet which acts on the travel time of an ultrasonic wave and forms the measuring sensor (16). 4. Device according to one of claims 1 to 3, characterized in that the pushbutton element (2) is designed as a plunger button in the form of a pin-like rod (21). 5. Device according to one of claims 1 to 4, characterized in that the sensing element (2) consists of lightweight material. 6. Device according to one of claims 1 to 5, characterized in that the measuring device (11) has a vertically extending measuring section (110) and the probe element (2) is mounted so as to be eludingly movable under weight. 7. Device according to one of claims 1 to 6, characterized in that the probe element (2) is flexible in the direction transverse to its longitudinal extension against spring-elastic restoring force. 8. Device according to one of claims 1 to 7, characterized in that the probe element (2) is arranged on a carriage (15) provided with a measuring sensor (16) which is held so as to be slidable along the measuring section (110) in a sliding guide (14) preferably arranged on the measuring device (11). 9. Device according to one of claims 1 to 8, characterized in that the lifting device (3) comprises at least one gripping element (31) which receives objects (51) for lifting and releases them for depositing. 10. Device according to one of claims 1 to 9, characterized in that at least one element (31) of the lifting device (3) engaging the object (51) and the sensing element (2) are arranged and held relative to one another in such a way that the sensing contact of the sensing element (2) with the object (51) which triggers the sliding movement takes place before the engaging element (31) comes into operative connection with the object (51). 11. Device according to one of claims 1 to 10, characterized in that at least one element (31) of the lifting device (3) engaging the object (51) and the sensing element (2) are arranged and held relative to one another in such a way that when the operative connection between the engaging element (31) and the object (51) is eliminated, the sliding position of the sensing element (2) changes. 12. Device according to one of claims 1 to 11, characterized in that the objects (51) are stackable parts which can be removed in succession with at least one gripping element (31) of the lifting device (3) from a stack (5) which thereby decreases in size and/or can be deposited in a stack (5) which thereby increases in size. 13. Device according to one of claims 1 to 12, characterized in that the setting and evaluation circuit (12) with circuit and/or pro- program elements that carry out error and/or fault detection and evaluation.