LIFT DEVICE

Abstract

 Lift device (1) for a forklift (2), with a first frame (3) extending between a lower end (31) and an upper end (32) and a second frame (4) extending between a lower end (41) and an upper end (42), wherein said second frame (4) is slidably arranged on said first frame (3) by way of at least two pairs of bearings (5a, 5b), and wherein one pair (5a) of said at least two pairs of bearings (5a, 5b) is arranged on said upper end (32) of said first frame (3) and one pair (5b) of said at least two pairs of bearings (5a, 5b) is arranged in a lower region of said second frame (4) nearby said lower end (41), and with driving means (11) arranged to drive said sliding motion of said second frame (4) relative to said first frame (3), and with a fork carriage (6) being supported by said second frame (4), wherein there is at least one additional pair of bearings (5c) being provided at said lower region of said second frame (4).

Description

[0001] The invention concerns a lift device with the features of the preamble of claim 1 and a forklift having such a lift device.

[0002] A lift device and a forklift of such kind are well known in the art. The problem with such lift devices and forklifts is that in order to increase lifting height of the fork carriage one has to increase total height of the first frame or use more frames nested into each other.

[0003] The purpose of the invention is to provide a lift device and a forklift having such a lift device in which an increased lifting height of the fork carriage is being achieved without increasing total height of the first frame or using more frames nested into each other.

[0004] This is being achieved by a lift device with the features of claim 1 and a forklift having such a lift device. Embodiments of the invention are defined in the dependent claims.

[0005] The distance between the pair of bearings of the first frame and the pair of bearings of the second frame decreases as the second frame moves upwards towards the upper end of the second frame. For a desired maximum lift height (the state in which the second frame and possible further frames slidingly arranged on the second frame is/are in its/their uppermost position(s) relative to the first frame) the minimum distance between the pair of bearings being provided at the first and second frame in the uppermost state of the second frame with respect to the first frame is a major limiting factor for longitudinal and lateral strength of the lifting device.

[0006] The invention provides that there is at least one additional pair of bearings being provided at said lower region of said second frame. By providing at least one extra pair of bearings at the lower region of the second frame the aforementioned distance between the pair of bearings of the first frame and the pair of bearings of the second frame is no longer a limiting factor because now the distance between the pair of bearings of the first frame and the extra pair of bearings of the second frame can meet the requirement regarding longitudinal and lateral strength of the lifting device.
In other words, the pair of bearings of the second frame already provided in the prior art can move closer to the pair of bearings of the first frame since the necessary minimum distance is now being measured between the pair of bearings of the first frame and the extra pair of bearings of the second frame.

[0007] The overall height of the lift device in the lowered or collapsed position of the second frame relative to the first frame is smaller than in the prior art for the same lifting height of the fork carriage.

[0008] It can be of advantage if the length of the first frame between the lower end and the upper end is smaller than the length of the second frame between the lower end and the upper end. Since there is provided at least one additional pair of bearings at the lower end region of the second frame, the first frame and the second frame need not be of the same length.

[0009] Furthermore, in a state in which one pair of the at least two pairs of bearings arranged at the lower region of the second frame has exited channels arranged in the first frame beyond the lower end of the first frame, the other pair of the at least two pairs of bearings arranged at the lower region of the second frame remains in the channels. Since there are at least two pairs of bearings at the lower end region of the second frame, one pair can exit the first frame while longitudinal and lateral strength of the lifting device can be maintained. In other words, when one pair of bearings has exited the channels, the other adjoining pair of bearings can remain in the channels and continue to contribute to the stability of the lifting device.

[0010] It can be of advantage if at least one pair of the pair of bearings is of a rotational type bearing, preferably a roller bearing type or a ball bearing type or a needle bearing type or a plain bearing type. It can also be of advantage if at least one pair of the pair of bearings is of a linear type bearing, preferably a sliding block type bearing. Channels for the bearings to run in can be formed in the first and/or second frame.

[0011] It can further be of advantage if said one pair of bearings arranged in a lower region of said second frame nearby said lower end is of a linear type bearing. Furthermore, it can be of advantage if said one additional pair of bearings being provided at said lower region of said second frame is of a linear type bearing.

[0012] More specifically, it can be of advantage if said one pair of bearings arranged in a lower region of said second frame nearby said lower end and said one additional pair of bearings being provided at said lower region of said second frame are connected to one another via a further pair of additional bearings, wherein said further pair of additional bearings is of a linear type bearing. Preferably, the aforementioned pairs of bearings can be formed integrally with one another.

[0013] Furthermore, it can be of advantage if at least said one pair of bearings arranged in a lower region of said second frame nearby said lower end and said one additional pair of bearings being provided at said lower region of said second frame and said further pair of additional bearings are of a sliding block type bearing. An integral or one piece construction of said bearings can be greatly facilitated by providing the bearings in form of a sliding block type bearing.

[0014] As already mentioned, protection is also sought for a forklift having a lift device as described. A lift device as described above can be built with a reduced overall height of the first frame. A reduced overall build height of the lift device can be achieved, thus lowering the center of gravity of the lift device while still providing the same lift height as for example a conventional lift device. A reduced overall height of such a lift device can contribute to the reduction of weight and an increase of the stability of a forklift having such a lift device due to the lower center of gravity of the forklift.

[0015] Such a forklift can be of a truck-mounted type. A lift device as described above can be of particular advantage for use with the truck mounted forklift, since ease of mounting and vertical clearance height of a mounted forklift can be optimized.

[0016] Embodiments of the invention are shown in the figures, wherein:

Fig. 1

shows a side view and a perspective view of an embodiment of the lift device for a forklift,

Fig. 2

shows a side view of the lift device in a fully collapsed (left side) and a fully extended (right side) state,

Fig. 3

shows a side view of the lift device in the various states of extension,

Fig. 4

shows a forklift having a lift device,

Fig. 5

shows a side view of a further embodiment of the lift device in a fully collapsed (left side) and a fully extended (right side) state, and

Fig. 6

shows a side view of a further embodiment of the lift device in a fully collapsed (left side) and a fully extended (right side) state.

[0017] Figure 1 shows a side view and a perspective view of an embodiment of the lift device 1 for a forklift 2 (also see figure 4). The lifting device has a first frame 3 with the lower end 31 and an upper end 32. A second frame 4 with a lower end 41 and an upper end 42 is nested into and slidably arranged on said first frame 3 and can - within certain boundaries dictated by stability requirements - be linearly moved relative to the first frame 3. A fork carriage 6 with mounted pair of forks 10 is supported (either in a fixed or movable manner) by the second frame 4. A pair of bearings 5a arranged on the upper end 32 of the first frame 3 and two pairs of bearings 5b, 5c arranged in a lower region of the second frame 4 are provided as guidance means for the relative motion of the first frame 3 and the second frame 4. One pair of bearings 5b of the two pairs of bearings 5b, 5c arranged in a lower region of the second frame 4 is arranged on the lower end 41 of the second frame 4. In order to contribute to the longitudinal and lateral strength of the lifting device 1, the bearings 5a arranged on the upper end 32 of the first frame 3 run on a rib 9 provided on the first frame 4 and the bearings 5b, 5c arranged in the lower region of the second frame 4 run in channels 8 provided in the first frame 3. The running surfaces (ribs 9) of the bearings 5a arranged on the upper end 32 of the first frame 3 could of course also be provided in the form of a channel or channels provided on the first frame 4. In the embodiment of the lift device 1 as shown in figure 1, driving means 11 (see figure 4) to drive the sliding motion of the second frame 4 relative to the first frame 3 are omitted for better visibility of the drawing.

[0018] As shown in the figures, the bearings 5a, 5b, 5c are of a rotational type bearing, such as a roller bearing type or a ball bearing type or a needle bearing type or a plain bearing type. Other types of bearings, especially a linear type bearings such as sliding block type bearings, can also be employed.

[0019] As shown in figure 1, the lifting device 1 is in the fully extended state in which the first frame 3 is in its uppermost position relative to the first frame 3. The distance d between the pair of bearings 5a on the upper end 32 of the first frame 3 and the pair of bearings 5b on the lower end 41 of the second frame is - with respect to stability requirements - at a minimum allowable value. It should be noted that the distance between the pair of bearings 5a on the upper end 32 of the first frame 3 and the pair of bearings 5c nearby the lower end 41 of the second frame 4 (the one above the pair of bearings 5b on the lower end 41 of the second frame 4) is below a minimum allowable value if these were the only pairs of bearings provided on the second frame 4.

[0020] Figure 2 shows a side view of the lift device 1 in a fully collapsed (left side) and a fully extended (right side) state. As can be seen from the side view of the lifting device 1 in its fully collapsed or retracted state, the length of the first frame 3 between its lower end 31 and its upper end 32 is smaller than the length of the second frame 4 between its lower end 41 and its upper end 42. In the fully collapsed state of the lift device 1 one pair of the two pairs of bearings 5b, 5c arranged at the lower region of the second frame 4 - namely the pair of bearings 5b arranged at the lower end 41 of the second frame 4 - has exited the channels 8 arranged in the first frame 3 beyond the lower end 31 of the first frame 3. The other pair of the two pairs of bearings 5c arranged at the lower region of the second frame 4 remains in the channels 8, thus still contributing to the longitudinal and lateral strength of the lifting device 1. It should be noted that a lift device without the additional pair of the bearings 5c arranged at the lower region the second frame 4 could not be safely retracted to a position as shown in figure 2, since at least one pair of bearings 5b, 5c arranged at the lower region of the second frame 4 must remain inside the channels 8 in order to fulfill stability requirements of the lift device 1.

[0021] Figure 3 shows a side view of the lift device 1 in a fully collapsed state (leftmost illustration of lift device 1), a partially extended state (middle illustration of lift device 1) and a further extended state (rightmost illustration of lift device 1). In the fully collapsed state of the lift device 1 the pair of bearings 5b arranged at the lower end 41 of the second frame 4 has exited the channels 8 arranged in the first frame 3 beyond the lower end 31 of the first frame 3. The other pair of the two pairs of bearings 5c arranged at the lower region of the second frame 4 is spaced apart from the pair of bearings 5b arranged at the lower end 41 of the second frame 4 by a distance x and remains in the channels 8 provided in the first frame 3. That middle lustration of the lift device 1 shows that if device 1 in partially extended state in which the second frame 4 has traveled a small distance relative to the first frame 3. The pair of bearings 5b arranged at the lower end 41 of the second frame 4 is about to enter the channels 8 arranged in the first frame 3. The rightmost illustration of the lift device 1 shows the lift device 1 in a further extended state in which the second frame 4 has traveled relative to the first frame 3 by a distance x.

[0022] Due to the provision of the additional pair of bearings 5c of the lift device 1 provided at the lower region of the second frame 4, which in the embodiment shown in figures 1, 2 and 3 is arranged at the lower end 41 of the second frame 4 and is spaced apart from the pair of bearings 5b arranged in the lower region of said second frame 4 by a certain distance x, the amount of available travel (and thus lift height) of the second frame 4 relative to the first frame 3 can be extended farther in comparison to a conventional lift device (with a first frame of the same length) without said additional pair of bearings 5c.

[0023] Conversely, due to the provision of said additional pair of bearings 5c of the lift device 1 provided at the lower region of the second frame 4, which is spaced apart from the pair of bearings 5b arranged in the lower region of said second frame 4 by a certain distance x, the lift device 1 can offer the same amount of travel of the second frame 4 relative to the first frame 3 like a conventional lift device, but with a reduced overall height of the first frame 3. A reduced overall build height of the lift device 1 can thus be achieved.

[0024] Figure 4 shows a forklift 2 having a lift device 1, which as shown is in a partially extended state. In the embodiment of the lift device 1 as shown in figure 4, driving means 11 to drive the sliding motion of the second frame 4 relative to the first frame are shown. The forklift 1 can be of a truck-mounted type. A lift device 1 with a reduced overall build height can be of particular advantage for use with the truck mounted forklift 2, since vertical clearance height of a mounted forklift 2 can thus be optimized.

[0025] Figure 5 shows a further embodiment of the lift device 1 which generally corresponds to the embodiment of the lift device 1 as shown in figure 2, with the difference that the one pair of bearings 5b arranged in a lower region of the second frame 4 nearby the lower end 41 and the one additional pair of bearings 5c being provided at the lower region of the second frame 4 are of a linear type bearing - more specifically, of a sliding block type bearing - and are connected to one another via a further pair of additional bearings 5d, wherein the further pair of additional bearings 5d is also of a linear type bearing - more specifically, of a sliding block type bearing. The pairs of bearings 5b, 5c spaced apart by a distance x as shown in the embodiment of the lift device 1 in figure 2 have thus been replaced by said sliding block type bearings 5b, 5c, 5d with a combined length of at least said distance x. It should be noted that the further pair of additional bearings 5d is not absolutely necessary.

[0026] As before, in the fully collapsed state of the lift device 1 (illustration of lift device 1 to the left), one pair of the two pairs of sliding block type bearings arranged at the lower region of the second frame 4 - namely the pair of sliding block type bearings 5b arranged at the lower end 41 of the second frame 4 - has exited the channels 8 arranged in the first frame 3 beyond the lower end 31 of the first frame 3. The other pair 5c of the two pairs of sliding block type bearings 5b, 5c arranged at the lower region of the second frame 4 remains in the channels 8, thus still contributing to the longitudinal and lateral strength of the lifting device 1.

[0027] In the lustration of the lift device 1 to the right of figure 5, the lifting device 1 is in the fully extended state in which the first frame 3 is in its uppermost position relative to the first frame 3. The distance d between the pair of bearings 5a on the upper end 32 of the first frame 3 - which in this embodiment are provided in the form of a rotational type bearing - and the pair of sliding block type bearings 5b on the lower end 41 of the second frame is - with respect to stability requirements - at a minimum allowable value. It should be noted that the distance between the pair of bearings 5a on the upper end 32 of the first frame 3 and the pair of sliding block type bearings 5c nearby the lower end 41 of the second frame 4 (the one above the further pair of additional bearings 5d and the pair of sliding block type bearings 5b on the lower end 41 of the second frame 4) is below a minimum allowable value if these were the only pairs of bearings provided on the second frame 4. The pair of bearings 5a on the upper end 32 of the first frame 3 may of course also be provided in the form of a linear type bearing, for example in the form of a sliding block type bearing.

[0028] Figure 6 shows a still further embodiment of the lift device 1, which generally corresponds to the embodiment of the lift device 1 as shown in figure 5, with the difference that the one pair of bearings 5b arranged in a lower end region of said second frame 4, the one additional pair of bearings 5c being provided at the lower end region of the second frame 4 and the further pair of additional bearings 5d connecting the two are formed integrally with one another. More specifically, the aforementioned pairs of bearings 5b, 5c, 5d are formed by a pair of single, elongate sliding block type bearings. The pairs of bearings 5b, 5c spaced apart by a distance x as shown in the embodiment of the lift device 1 in figure 2 have thus been replaced by said pair of single, elongate sliding block type bearings with a length of at least said distance x.

List of reference numerals:

[0029] 

1

lift device

2

forklift

3

first frame
31 lower end of first frame
32 upper end of first frame

4

second frame
41 lower end of second frame
42 upper end of second frame

5a

bearing

5b

bearing

5c

bearing

5d

bearing

6

fork carriage

8

channel in the first frame

9

rib on second frame

10

fork

d

distance

x

distance

Claims

1. Lift device (1) for a forklift (2), with a first frame (3) extending between a lower end (31) and an upper end (32) and a second frame (4) extending between a lower end (41) and an upper end (42), wherein said second frame (4) is slidably arranged on said first frame (3) by way of at least two pairs of bearings (5a, 5b), and wherein one pair (5a) of said at least two pairs of bearings (5a, 5b) is arranged on said upper end (32) of said first frame (3) and one pair (5b) of said at least two pairs of bearings (5a, 5b) is arranged in a lower region of said second frame (4) nearby said lower end (41), and with driving means (11) arranged to drive said sliding motion of said second frame (4) relative to said first frame (3), and with a fork carriage (6) being supported by said second frame (4), characterized in that there is at least one additional pair of bearings (5c) being provided at said lower region of said second frame (4).

2. Lift device according to claim 1, wherein the length of said first frame (3) between said lower end (31) and said upper end (32) is smaller than the length of said second frame (4) between said lower end (41) and said upper end (42).

3. Lift device according to the preceding claim, wherein in a state in which one pair (5b) of said at least two pairs of bearings (5b, 5c) arranged at said lower region of said second frame (4) has exited channels (8) arranged in said first frame (3) beyond said lower end (31) of said first frame (3), the other pair (5c) of said at least two pairs of bearings (5b, 5c) arranged at said lower region of said second frame (4) remains in said channels (8).

4. Lift device according to at least one of the preceding claims, wherein at least one pair of said pair of bearings (5a, 5b, 5c) is of a rotational type bearing, preferably a roller bearing type or a ball bearing type or a needle bearing type or a plain bearing type.

5. Lift device according to at least one of the preceding claims, wherein at least one pair of said pair of bearings (5a, 5b, 5c) is of a linear type bearing, preferably a sliding block type bearing.

6. Lift device according to the preceding claim, wherein said one pair of bearings (5b) arranged in a lower region of said second frame (4) nearby said lower end (41) is of a linear type bearing.

7. Lift device according to one of the two preceding claims, wherein said one additional pair of bearings (5c) being provided at said lower region of said second frame (4) is of a linear type bearing.

8. Lift device according to the two preceding claims, wherein said one pair of bearings (5b) arranged in a lower region of said second frame (4) nearby said lower end (41) and said one additional pair of bearings (5c) being provided at said lower region of said second frame (4) are connected to one another via a further pair of additional bearings (5d), wherein said further pair of additional bearings (5d) is of a linear type bearing, and wherein preferably said one pair of bearings (5b) arranged in a lower end region of said second frame (4), said one additional pair of bearings (5c) being provided at said lower end region of said second frame (4) and said further pair of additional bearings (5d) are formed integrally with one another.

9. Lift device according to at least one of claims 5 to 8, wherein at least said one pair of bearings (5b) arranged in a lower region of said second frame (4) nearby said lower end (41), said one additional pair of bearings (5c) being provided at said lower region of said second frame (4) and said further pair of additional bearings (5d) are of a sliding block type bearing.

10. Forklift (2), having a lift device (1) according to at least one of the preceding claims.

11. Forklift according to the preceding claim, wherein said forklift (2) is a truck-mounted forklift (2).

Drawing