EP3000767A1

EP3000767A1 - Load-lifting device comprising an intermediate rotary rolling element elastically connected to the main body of the jack

Info

Publication number: EP3000767A1
Application number: EP14801403.8A
Authority: EP
Inventors: Antonio Martinez Martinez
Original assignee: Melchor Gabilondo SA
Current assignee: Melchor Gabilondo SA
Priority date: 2013-05-20
Filing date: 2014-04-23
Publication date: 2016-03-30
Also published as: ES2531423A1; EP3000767A4; WO2014188031A1; ES2531423B1

Abstract

A load-lifting device, comprising a main body (2), which comprises at least one rear rolling element (7), located in a rear zone (8) of the device and which can be actuated by the user in order to manoeuvre the device; at least one front rolling element (10) located in a front zone (11) of the device closer to the force applicator (5) than the rear zone (8); an intermediate rotary rolling element (12), located between the rear zone (8) and the front zone (11) of the device and elastically connected to the main body (2), the centre of gravity of the device being disposed behind the intermediate rotary rolling element (12) such that, when loaded, all of the rolling elements (7, 10, 12) rest on the floor, while, when not loaded, the front rolling elements (10) do not rest on the floor, thereby improving the manoeuvrability of the device.

Description

FIELD OF APPLICATION

The invention relates to a load-lifting device, for example a trolley jack of the type used to help lift vehicles or other heavy objects.

STATE OF THE ART

In the industrial state of the art, many load-lifting devices for lifting heavy objects, for example vehicles, are known. Some such devices are jacks (trolley, bottle, etc.), which lift a load pushing it from below and cranes, which lift a load pulling it from above. In some cases, the load-lifting devices have wheels in order to move with respect to the floor.
For example, trolley jacks are devices commonly used in car repair garages and other mechanical work environments, which enable the heavy objects, such as vehicles, to be lifted. A trolley jack generally comprises a main body, with respect to which some type of lifting element is movably disposed that, duly actuated by means of a hydraulic system or similar, is capable of raising itself, exerting sufficient force underneath the vehicle or heavy object to cause the lifting thereof. Examples of lifting elements are articulated lifting arms, telescopic mechanisms capable of extending vertically or at an inclined angle and, in any case, with a vertical upward component, etc. Additionally, trolley jacks comprise actuating means so that the user can actuate the hydraulic system or similar and the consequent ascent of the lifting element. Similarly, the jack comprises actuation means for enabling the controlled descent of the lifting element, wherein said descent must be carried out in a controlled manner, as the lifting element generally descends when loaded, i.e. while bearing the weight of the vehicle and, therefore, avoiding imbalances, tipping or falls is vital for guaranteeing safety.
Known trolley jacks are capable of moving by means of wheels, rollers or other rolling elements comprised in the main body. Given that the main body is generally disposed very close to the floor and has a relatively low height, jacks usually comprise a lever that projects upwards from the main body to provide the user with a gripping zone for pulling or pushing the jack from one place to another, or for turning the trolley around.
As regards the distribution of the wheels on the jack, a known solution consists of disposing two rotary wheels in the rear zone of the jack (the zone closest to the lever and, therefore, the user) and two fixed wheels in its front zone. Another known solution consists of the jack also having one additional fixed wheel placed on a lifting element in the form of a folding arm, wherein said additional fixed wheel only rests on the floor when the arm is not raised. In this case, when the lifting element ascends, the additional fixed wheel ascends together with said lifting element and the jack then rests on the two remaining fixed wheels and on the two rotary wheels. However, if the lifting element is not raised, the fixed wheel rests on the floor. In this second scenario, the additional fixed wheel, resting on the floor, makes it possible for a force applicator of the vehicle, i.e. a point or surface of the lifting element that exerts a lifting force on the vehicle, to follow the same angle as the lever, thereby improving manoeuvrability with respect to the previous solution without an additional fixed wheel.
Trolley jacks are devices that can be quite heavy. For example, a jack capable of lifting 2 tonnes may weigh approximately 45 kg; a jack capable of lifting 6 tonnes may weigh up to 81 kg.
Due the heavy weight of some trolley jacks, in practice it is not always easy to move or turn a jack around, despite having wheels and even an additional fixed wheel in the lifting element. The complication of the rotation can be observed in the fact that, in current trolley jacks, it is necessary to greatly rotate the lever to achieve a rotation of a certain magnitude of the front end of the jack, which is where the point of the lifting element destined for vertically pushing the vehicle is located. If the jack is very heavy, causing the rotation of the lever requires a significant effort and therefore entails risks for the user, who must usually repeat this task.
The invention is particularly aimed at designing a trolley jack that simplifies and facilitates the rotation thereof, reducing the effort that must be made by the user. This is aimed at improving the manoeuvrability of the jack to facilitate the positioning thereof, for example to help the user to position the jack appropriately with respect to the vehicle before proceeding to lift it.
In addition, the invention is generally aimed at achieving a load-lifting device which, being provided with wheels or rolling elements for moving along the floor, has improved manoeuvrability with respect to conventional rolling load-lifting devices.

BRIEF DESCRIPTION OF THE INVENTION

The subject matter of the invention is a load-lifting device comprising a main body with respect to which a lifting element is capable of ascending or descending to lift a heavy object, wherein said lifting element comprises a force applicator capable of exerting an upward force on the object. The main body can rest and move along the floor by means of rolling elements. A particular feature of the device according to the invention is that it comprises at least one rear rolling element located in rear zone of the device which can be actuated by the user in order to manoeuvre the device; at least one front rolling element, located in a front zone of the device closer to the force applicator than the rear zone; and an intermediate rotating rolling element. The intermediate rotating rolling element is connected to the main body by means of an elastic element. Said elastic element tends to cause a separation of the intermediate rotating rolling element with respect to the main body until all the rolling elements (front, rear and intermediate rotating elements) are not on the same plane. In addition, said elastic element is capable of deforming itself until the rolling elements are on the same plane. The intermediate rotating rolling element is located between the rear zone and the front zone. Also according to the invention, the proportion of mass of the device distributed between the intermediate rotating rolling element and the rear rolling element is greater than the proportion of mass distributed between the intermediate rotating rolling element and the front rolling element. That is, the centre of gravity is behind the intermediate rotating rolling element.
The device according to the invention works as follows. When not loaded, i.e. with the force applicator not exerting force on the object, the elastic element separates the intermediate rotating rolling element sufficiently so that the rolling elements of the device are not on the same plane. Consequently, as a consequence of the position of the centre of gravity and of the action of the force of gravity, the rear rolling elements and the intermediate rotating rolling element rest on the floor, whilst the front rolling elements remain in the air. However, when loaded, wherein the lifting element exerts an upward force on a heavy object, consequently receiving the corresponding force of reaction of the heavy object, the elastic element is flexed sufficiently so that all the rolling elements are located on the same plane and, therefore, the front rolling elements rest on the floor.
In this way, the device according to the invention has the following advantages. On the one hand, having an intermediate rotating rolling element closer to the rear zone of the device (a zone that can be actuated by the user in order to manoeuvre the device) than the front rolling elements, added to the fact that when not loaded the front rolling elements do not rest on the floor, endows the device with great manoeuvrability. Manoeuvrability is understood to be the maximisation of the rotation of the front zone of the device, where the force applicator or zone of the lifting element that pushes the heavy object, for a same rotation angle of the rear zone of the device, is usually found, where the actuation lever or other actuation means which can be actuated by the user is disposed. This reduces the effort that must be made by the user, as in order to perform the same rotation of the force applicator the user must rotate the lever or other actuation means less, compared to conventional devices. On the other hand, the fact that when loaded the front rolling elements rest on the floor makes it possible to endow the device with great resistance, since said front rolling elements, particularly if they are fixed, may be designed with a high capacity to support the weight of the load of the device. In turn, the intermediate rotating rolling element only has to provide manoeuvrability and it will not have to bear heavy weights, since when loaded the weight is borne to a greater extent by the front rolling elements.

BRIEF DESCRIPTION OF THE FIGURES

The details of the invention can be observed in the accompanying figures, which do not aim to limit the scope of the invention:

Figure 1 shows a perspective view of an embodiment of a device in accordance with the invention, in this case in the form of a trolley jack;
Figure 2 shows a side view of the jack of Figure 1 when not loaded or idle;
Figure 3 shows an expanded cross-sectional front view in accordance with the cross-section plane A-A illustrated in Figure 2;
Figure 4 shows a side view of the jack of Figure 1 under a loaded condition;
Figure 5 shows an expanded cross-sectional front view in accordance with the cross-section plane B-B illustrated in Figure 4; and
Figures 6, 7 and 8 show schematic elevation views of the state of the art and of the jack according to the invention represented in the preceding figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a perspective view of an embodiment of a load-lifting device in accordance with the invention. In the embodiment represented, the load-lifting device is a jack (1) of the type known as a trolley jack. As can be observed in the figure, the jack (1) comprises a main body (2) with respect to which a lifting element (3), intended for exerting a force on a heavy object to cause the lifting thereof and also intended for sustaining the heavy object during lowering thereof, is capable of ascending or descending. In the embodiment of the figure, the lifting element (3) is a lifting arm capable of folding with respect to the main body (2), as schematically indicated by an arrow (4). The lifting element (3) has a force applicator (5) at its end, said force applicator precisely being the zone responsible for exerting the upward force on the object to cause the lifting thereof. In the embodiment represented, the force applicator (5) is a circular flat surface intended for coming into contact with the underbody of a vehicle or with a lower surface of the object to be lifted. The jack (1) has been represented resting on a floor (6). The main body (2) can move with respect to said floor (6) by means of different rolling elements. More specifically, the jack (1) comprises at least one rear rolling element (7) located in a rear zone (8) of the jack (1). The rear zone (8) of the jack (1) is the zone that can be actuated by the user in order to manoeuvre the jack (1), specifically actuating a handle (9a) of an actuation lever (9). In this particular case, the jack (1) comprises two rear rolling elements (7) in the form of fixed wheels, i.e. two wheels whose rotation axis does not change direction. In addition, the jack (1) comprises at least one front rolling element (10) located in a front zone (11) of the device closer to the force applicator (5) than the rear zone (8). In this case, the front rolling element (10) is a single cylinder or roller that is fixed, i.e. whose rotation axis does not change direction. The jack (1) also comprises an intermediate rotating rolling element (12). In the embodiment represented, the intermediate rotating rolling element (12) is a wheel which is capable of rotating on itself according to a central rotation axis (14) in order to roll with respect to the floor (6). The intermediate rotating rolling element (12) is also capable of rotating with respect to a vertical rotation axis (14), causing the rotation axis (13) to have a variable direction. In addition, the intermediate rotating rolling element (12) is fixed elastically to the main body (2), said elastic connection enabling the vertical position of the intermediate rotating rolling element (12) to vary. Elastic connection is understood to be that the intermediate rotating rolling element (12) is fixed to the main body (2) by means of an elastic element (16).
Also in accordance with the invention, the proportion of mass of the jack (1) distributed between the intermediate rotating rolling element (12) and the rear rolling elements (7) is greater than the proportion of mass distributed between the intermediate rotating rolling element (12) and the front rolling element (10). That is, the centre of gravity of the jack (1), when not loaded, is located behind the intermediate rotating rolling element (12), between the intermediate rotating rolling element (12) and the rear zone (8) of the jack (1).
Figure 2 shows a schematic side view of the jack (1) of Figure 1 in a situation wherein the lifting element (3) is disposed folded against the main body (2) and wherein the jack (1) is not loaded, i.e. not exerting a force on an object. In this situation, as can be observed, the lowest points of the rolling elements (7, 11, 12) are not disposed on the same plane, but rather the lowest point of the intermediate rotating rolling element (12) is located below an imaginary plane (15) that joins the lowest points of the rear rolling elements (7) and of the front rolling element (10). In this situation, due to the fact that the centre of gravity of the jack (1) is located behind the intermediate rotating rolling element (12), between the intermediate rotating rolling element (12) and the rear zone (8), the intermediate rotating rolling element (12) and the rear rolling elements (7) rest on the floor (6) while the front rolling element (10) remains in the air. Therefore, in an unloaded situation only the rear rolling elements (7) and the intermediate rotating rolling element (12) are actuated, achieving maximum manoeuvrability, as explained below.
Figure 3 shows a front cross-sectional view of the jack (1) of the preceding figure, wherein it can be clearly observed that the intermediate rotating rolling element (12) is disposed fixed to the main body (2) by means of an elastic element (16), which in this case has the shape of a band extending between two inner walls (2a, 2b) of the main body (2). The intermediate rotating rolling element (12) is disposed fixed to the central zone of said band and is capable of varying its height in accordance with the deformation of the band.
Figure 4 shows the jack (1) of Figure 2 when loaded, i.e. in a situation wherein the lifting element (3) is exerting a force on a heavy object (17), schematically represented as an irregular polygon and, consequently, the object (17) exerts a reaction force (F) on the lifting element (3). The lifting element (3) is shown in its lowest position, without yet having begun to rotate in an upward direction as the arrow (4) indicates. Under this load situation, the reaction force (F) on the lifting element (3) is transferred to the main body (2), due to being the lifting element (3) fixed thereto. Due to the fact that the intermediate rotating rolling element (12) is disposed resting on the floor (6) and the fact that there is an elastic connection between the intermediate rotating rolling element (12) and the main body (2) which enables a relative vertical movement between the two, the reaction force (F) applied to the main body (2) causes the main body (2) to descend with respect to the intermediate rotating rolling element (12) while the elastic element (16) is flexed. A point is reached wherein the elastic element (16) is flexed sufficiently for the front rolling element (10) to rest on the floor, as can be observed in the figure. In this way, when loaded the front rolling element (10) bears the weight of the object (17) rather than the intermediate rotating rolling element (12), which is less capable of bearing weight due to being rotary.
Figure 5 shows a front cross-sectional view of the jack (1) of the preceding figure, wherein it can be clearly observed that the elastic element (16) has become deformed, enabling the descent of the main body (2) with respect to the intermediate rotating rolling element (12), which is disposed resting on the floor (6).
The elastic element (16) is configured such that it exerts an elastic force that tends to cause the descent of the intermediate rotating rolling element (12) with respect to the main body (2) until the lowest points of the rolling elements (7, 10, 12) are not on the same plane. That is, it tends to return the jack (1) to the idle position of Figure 2, wherein the lowest point of the intermediate rotating rolling element (12) rests on the floor while the lowest point of the front rolling element (10) is in the air. Therefore, when not loaded, the jack (1) automatically returns to said idle position.
Figures 6, 7 and 8 show schematic elevation views of two jacks known in the state of the art and of the jack (1) according to the invention represented in the preceding figures, with the aim of illustrating the improved manoeuvrability achieved with the jack of the present invention. Figure 6 shows a conventional jack (100) equipped with two rotating rear wheels (107) in its rear zone (108), two fixed front wheels (110) in its front zone (111) and an actuation lever (109) disposed in its rear zone (108). When a user rotates the actuation lever (109) pushing a handle (109a) thereof towards the left or towards the right, the rear wheels (107), due to being rotary, rotate freely, while the front wheels (110), due to being fixed, do not rotate freely. Consequently, the pivot point (150) of this first conventional jack is disposed between the front wheels (110), which are fixed and equidistant therebetween, in front of the force applicator (105) (zone of the jack (1) intended for exerting force on the object to be lifted). Therefore, when the user rotates the handle (109a) of the actuation lever (109) describing an arc (A1) such as the one illustrated in the figure, it causes the practically null rotation of the front zone (111) and a very small rotation of the force applicator (105), indicated by the arc (B1). That is, the user must greatly rotate the rear zone (108) of the jack (100) to achieve a very small rotation of the front zone (111) and the force applicator (105), thereby requiring a large effort. Figure 7 shows another conventional jack (200), in this case equipped with two rotary rear wheels (207) in its rear zone (208), two fixed front wheels (210) in its front zone (211) and one intermediate fixed wheel (212). In this conventional second jack (200), the intermediate fixed wheel (212), due to being fixed, serves as a pivot point (250) of the jack. Therefore, a rotation arc (A2) similar to that of the rotation arc (A1) of the preceding figure causes the force applicator (205) to describe an arc (B2) greater than the arc (B1) of the preceding figure. This is equivalent to saying that the conventional jack (200) of this figure requires the user to make a greater effort to rotate the front zone (211) thereof compared to the conventional jack (100) of the preceding figure and, consequently, is more manoeuvrable. However, figure 8 shows the jack according to the invention, equipped with two rear wheels or rolling elements (7) in its rear zone (8), a front roller or rolling element (10) in its front zone (11) and an intermediate wheel or rotating rolling element (12). When not loaded, the front rolling element (10) does not rest on the floor, due to which the pivot point (50) of the jack is disposed in the zone of the rear rolling elements (7), due to being fixed and the intermediate rotating rolling element (12) being rotary. Specifically, the pivot point (50) is disposed between the rear rolling elements (7) and equidistant therebetween, very close to the actuation lever (9). The actuation lever (9) is represented in a more forward position compared to the actuation levers (109, 209) of the two preceding figures, but if it had been represented disposed in the same manner, its handle (9a) would be positioned at the point represented in the present figure. Therefore, if a user were to rotate the handle (9a) describing an even smaller arc (A3) than the arcs (A1, A2) of the preceding figures, the front zone (11) would be rotated and, in particular, the force applicator (5) would describe an arc (B3) considerably larger than in the two preceding figures. That is, the manoeuvrability achieved by the jack (1) of the invention is very high, since it would be sufficient for the user to slightly rotate the rear zone (8) of the jack in order to greatly rotate the front zone (11), where the force applicator (5) is located.
In the embodiment represented, as can be observed in figure 4, when loaded the lowest points of all the rolling elements (7, 10, 12) are disposed on the same plane, such that all the rolling elements (7, 10, 12) rest on the floor (6). In this situation wherein all the rolling elements (7, 10, 12) are resting on the floor (6), the weight of the jack (1) and of the object (17) or load is preferably borne by the rear rolling elements (7) and the front rolling element (10), and not by the intermediate rotating rolling element (12), even though the latter is in contact with the floor (6).
As mentioned earlier, in the embodiment represented the elastic element (16) is a band connected to the main body (2) and whereto the intermediate rotating rolling element is fixed (12). Alternatively, the elastic element (16) may be a spring or damper connected to the main body (2) and whereto the intermediate rotating rolling element (12) is fixed. Other embodiments along these lines are not ruled out.
In the embodiment represented, the intermediate rotating rolling element (12) is disposed approximately in the centre of the main body, seen from above. In alternative embodiments, the intermediate rotating rolling element (12) in accordance with the invention can be found in other points of the main body (2) at a certain distance from the centre and disposed between the rear rolling elements (7) and the front rolling elements (10).
In accordance with the invention, both the front rolling elements and the rear rolling elements may be fixed -as in the embodiment represented in the figures- or rotary. Fixed is understood to mean that their rotation axis does not change direction. Rotary is understood to mean that their rotation axis may change direction.
The fact that the rear rolling elements are fixed, as in the embodiment of the figures, has certain advantages that can be observed in the jack (1) of the figures. On the one hand, the resulting jack (1) may be narrower. On the other, the rear rolling elements (7) may be large and consequently cause the jack (1) to be much more pleasant and easy to handle.
In the embodiment represented, the force applicator (5) is a circular flat surface intended for coming into contact with the underbody of a vehicle or with a lower surface of the object to be lifted. The invention envisages different force applicators, capable of pushing the object or load upwards (for example, a piston shaft) or capable of pulling on the object from above (for example, a hook or claw).

Claims

A load-lifting device comprising a main body (2) with respect to which a lifting element (3) is capable of ascending or descending to lift a heavy object (17), wherein said lifting element (3) comprises a force applicator (5) capable of exerting an upward force on the object (17), wherein the main body (2) can rest on and move along a floor (6) by means of rolling elements, characterised in that it comprises:
- at least one rear rolling element (7) located at a rear zone (8) of the device which can be actuated by the user in order to manoeuvre the device;

- at least one front rolling element (10), located in a front zone (11) of the device closer to the force applicator (5) than the rear zone (8);

- an intermediate rotating rolling element (12) located between the rear zone (8) and the front zone (11) of the device and connected to the main body (2) by means of an elastic element (16), wherein said elastic element (16) tends to cause a separation of the intermediate rotating rolling element (12) with respect to the main body (2) until the rolling elements (7, 8, 9) are not on the same plane and wherein the elastic element (16) is capable of being deforming until the rolling elements (7, 8, 9) are on the same plane; and wherein

- the proportion of mass of the device distributed between the intermediate rotating rolling element (12) and the rear rolling element (7) is greater than the proportion of mass distributed between the intermediate rotating rolling element (12) and the front rolling element (10).
The device, according to claim 1, characterised in that the rear rolling elements (7) are fixed.
The device, according to claim 1, characterised in that the rear rolling elements (7) are rotary.
The device, according to claim 1, characterised in that the front rolling elements (10) are fixed.
The device, according to claim 1, characterised in that the front rolling elements (10) are rotary.
The device, according to claim 1, characterised in that the elastic element (16) is a band connected to the main body (2) and whereto the intermediate rotating rolling element (12) is fixed.
The device, according to claim 1, characterised in that the elastic element (16) is a spring connected to the main body (2) and whereto the intermediate rotating rolling element (12) is fixed.
The device, according to claim 1, characterised in that the elastic element (16) is a damper connected to the main body (2) and whereto the intermediate rotating rolling element (12) is fixed.
The device, according to claim 1, characterised in that one or more of the rolling elements is a wheel.
The device, according to claim 1, characterised in that one or more of the rolling elements is a ball.
The device, according to claim 1, characterised in that one or more of the rolling elements is a roller.