DE29606489U1 - Boom for a lifting device - Google Patents

Description

2-15.006 EN

Zasche Fördertechnik GmbH Gewerbestrasse 23 86720 Nördlingen

Boom for a lifting device

The invention relates to a boom for a lifting device, which is formed from an inner arm part, which is pivotably mounted at one end about a vertical pivot pin, and which is connected at the other end by means of a joint with a vertical pivot axis to an outer arm part, which carries a load-carrying device at its free end - directly or with the interposition of further components.

Such booms are often used in small lifting devices, especially in hand-held manipulators. Because the outer arm can be swiveled almost 360° around the joint that connects it to the inner arm, the load-carrying device in this design covers a very large area.

However, this design has the disadvantage that if the outer arm deviates by an angle of maximum 90° from the longitudinal extension of the inner arm, the latter undergoes a torsional deformation under the influence of the load carried by the load-carrying device, which leads to the outer arm being inclined downwards by a certain amount, whereby the

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Axis of the joint connecting the two arms deviates from the vertical by a corresponding angle. If the load is to be moved from this position to another position in which both arms extend in the same direction, this means that the load must be moved from a low level to a higher level with additional effort. Conversely, the outer arm always tends to move from the extended position to the position bent at 90° because, by natural law, it seeks the position of least potential energy. This has the disadvantage that if the operator lets go of the load, it will move out of the extended position in an unsupervised moment and may hit objects or people standing in the way, damaging or injuring them.

This problem has been known for a long time and various ways have been tried to avoid these disadvantages. For example, attempts have been made to reduce the torsional deformation of the inner arm section by strengthening it. Since torsional deformation cannot be completely avoided, the problem can be reduced but not completely eliminated. There is also the disadvantage that the force required to move the load must be increased due to the increased mass of the boom.

In order to prevent the load from moving spontaneously from the extended position to the bent position, another proposal is to provide a constantly acting brake on the joint that connects the two partial arms. This way, the load can be prevented from moving spontaneously, but additional force is required when moving the load back from the bent position to the extended position in order to overcome the braking force.

In continuation of this idea, it has already been suggested that this brake can be switched off. The brake is activated, for example, by the operator holding a handle to move the load, in the manner of a

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Dead man's switch is switched off so that the braking force does not have to be overcome when moving the load. If, however, the operator lets go of the handle, the brake is automatically switched on and the load is held securely in its current position. This is an advantage over the previously described design, but there is still the disadvantage that when moving the load from the angled to the extended position, it - as with the other designs described - has to be brought from a low to a higher position with additional force.

Finally, it has already been suggested that the joint connecting the two arms should be adjusted so that when the two arms are in the inserted position, its axis deviates from the vertical by the same amount that it deviates in the bent position under the influence of a certain load. However, this idea, which at first seems compelling, only brings a partial improvement, and in some cases even a deterioration, compared to the original starting state. First of all, this system can only function properly if the fixed inclination of the joint axis corresponds exactly to the inclination of this axis in the bent position. Since the latter inclination of the joint axis depends on the size of the load acting on the load-bearing device, it can actually only coincide with the previously fixed inclination when the two arms are in the extended position purely by chance. If, on the other hand, the attached load is somewhat larger, then it will move automatically from the extended position to the angled position, but if it is smaller, then it will move automatically from the angled position to the extended position. And a very particular disadvantage arises with this design when the outer arm is moved from the extended position to a position swiveled by 180°, in which the two arms are on top of each other. In this position, the outer arm would be raised by such an amount that it would move automatically from here to the extended position.

In summary, it must be said that although a whole series of solutions have been proposed, none of them are really satisfactory

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could.

The invention is based on the object of avoiding the disadvantages described in ¹ and of creating a solution with the least possible design effort, in which the load remains stationary in any position of the outer arm part and can also be moved from any position of the outer arm part with a constant low force.

The invention achieves this object in that parts of the inner arm part or of the joint in a plane containing the bearing pin and the joint are designed to be elastically flexible in such a way that, under the influence of a load carried by the load-bearing means, a deviation of the pivot axis of the joint from the vertical occurs which corresponds at least approximately to the deviation of this pivot axis from the vertical which occurs as a result of the torsional deformation of the inner arm part when it is at an angle of 90° to the outer arm part. It is only necessary to design the elastic flexibility in such a way that, under the influence of a load, it allows a deviation of the joint axis from the vertical to the same extent as the torsional deformation of the inner arm part caused by the same load.

A possible structural design can be achieved in that the joint connecting the two partial arms has two pivot bearings arranged at an axial distance from one another, which have at least one outer part surrounding a pin, whereby at least the outer part of one pivot bearing is mounted in an elongated hole in a housing surrounding it, and whereby the elongated hole extends in the direction of the longitudinal axis of the inner partial arm and corresponds in the transverse direction to the external dimension of the outer part, while in the longitudinal direction it exceeds this and whereby the cavity between the outer part and the elongated hole is filled with an elastically flexible material. This design makes it possible for the outer part to move in the elongated hole in the extended position of the two partial arms under the effect of a load when the flexible material used is elastically deformed, whereby the longitudinal axis of the joint has an inclination relative to the

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Vertical. With the correct dimensioning and design of the elastically flexible material, this inclination of the joint axis in the extended position of the two partial arms will correspond to the inclination of the joint axis that it experiences in the 90° position as a result of the torsional deformation of the inner partial arm.

In the small lifting devices mentioned above, especially in hand-held manipulators, a design is often used for the boom in which the inner arm section has a push rod arranged above or below it, and in which the arm section and the push rod are connected at both ends by means of joints with horizontal axes, on the one hand to a support head on the sleeve surrounding the pivot pin and on the other hand to a housing surrounding the joint. This design is referred to as a parallelogram boom. With such a boom, the desired goal can be achieved in a simple manner by integrating an elastically flexible element into the push rod. Under the influence of a load, the elastically flexible element can be deformed, which leads to an elongation or shortening of the push rod, whereby the axis of the joint connecting the two arms experiences an inclination relative to the vertical.

The elastically flexible element can be formed, for example, by two compression springs that are inserted into a longitudinal bore of the push rod and are supported there with their opposite ends on projections in the bore, while their ends facing each other rest on a collar of a bolt that is longitudinally displaceable in the longitudinal bore. If a load acts on the load-bearing device when the two partial arms are in the extended position, one compression spring is loaded and compressed by a certain amount, which results in an extension of the upper or a shortening of the lower push rod. If, on the other hand, the outer partial arm is swiveled back by 180° from this position, the other compression spring is compressed, which leads to a shortening of the upper or an extension of the lower push rod. In both cases,

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This ensures that the deviation of the longitudinal axis of the joint connecting the two arms in the two positions described will be just as large as in the positions bent at 90°.

When using the parallelogram boom mentioned above, another possibility for solving the problem arises in that the joints with horizontal axes on the push rod are formed by bearing bolts that engage in the eyes surrounding them, with a bushing made of elastically flexible material being inserted between the bolt and the eye on at least one joint. With the correct choice of material and the correct dimensioning of this bushing, it can be achieved, as previously described, that the longitudinal axis of the joint connecting the partial arms experiences the correct deviation from the vertical in the extended position of the two partial arms.

The elastically flexible elements can be made of a polymeric material, in particular a thermoplastic.

The drawings show embodiments of the invention. They show:

Fig. 1 a side view of a lifting device,

Fig. 2 is a plan view of the lifting device according to Fig. 1,

Fig. 3 a longitudinal section through the two arms of the lifting device

connecting joint,

Fig. 4 is a cross-section along line IV-IV of Fig. 3,

Fig. 5 is a side view of a lifting device modified from Fig. 1,

Fig. 6 a longitudinal section through the joint connecting the two partial arms,

Fig. 7 is a cross-section along line VII-VII of Fig. 6 and

Fig. 8 shows a modified variant compared to Fig. 7.

In Fig. 1, a sleeve 3 is pivotably mounted on a pivot pin 1 at the upper end of a column 2, to which an inner arm part 4 is firmly connected. The outer arm part 4 is connected to the free end of this arm part 4 by means of a joint 5.

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Partial arm 6 is pivotally mounted. This has a guide 7 at its free end for the vertically movable mounting of the telescopic rod 8, which has a load hook 9 at its lower end. A lifting drive 10 is provided for the up and down movement of the telescopic rod 8, which is connected to the telescopic rod by means of a cable 11.

The top view of this lifting device shown in Fig. 2 shows that the inner arm section 4 can be pivoted around the pivot pin 3 so that the joint 5 describes the circular arc 12 shown in dashed lines. The outer arm section 6 can also be pivoted around the joint 5, with the telescopic rod 8 describing the circular arc 13 shown in dashed lines. The outer arm section 6 can assume the extreme positions indicated by the letters A, B, C and D.

In positions A and C, in which the longitudinal axes of the arms 4 and 6 run parallel to each other, the inner arm 4 is only subjected to bending stress. In positions B and D, the inner arm 4 is also subjected to torsional stress. This means that in these positions B and D, the free end of the outer arm 6 and thus also the load attached to the load hook sinks to a lower level than in positions A and C. This has the unpleasant consequence that if the operator releases the load in positions A or C, it will move by itself to either position B or D. If this happens unattended, it can lead to accidents or damage to people or objects that are in the swivel range of the outer arm 6. In addition, if the load is to be swivelled from position B or D to one of the positions A or C, it must be lifted from a lower to a higher level, which requires additional effort.

In Fig. 3 and 4, a solution is shown that eliminates these disadvantages. At the free end of the inner arm part 4, a housing 14 is connected to it, in which a pin 15, which is connected to the outer arm part 6, is pivotally mounted. For this purpose, the inner rings are mounted on the pin 15.

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16 and 17 of two plain bearings located at an axial distance from each other. These are fixed to the pin 15 by spacer sleeves 18 and 19 and a snap ring 20.

The inner ring 17, together with the outer ring 21, forms a joint bearing with spherical sliding surfaces, which allows a pivoting movement of the pin 15. An outer part 22, which - as shown in Fig. 4 - has a square outer contour, works together with the inner ring 16. This outer part 22 is inserted into a long hole 23 of the housing 14, the dimensions of which are selected such that the outer part has a displacement path in the direction of the longitudinal axis of the inner arm part 4, while it is guided without play in the transverse direction. The spaces remaining on both sides of the outer part 22 opposite the long hole 23 are filled with an elastically flexible material 24.

If a force acts on the inner arm part 6 due to a load attached to the load hook 9, this leads to the pin 15 being inclined by a certain amount relative to the vertical due to deformation of the elastically flexible material 24. The dimensions and the elasticity of the material 24 must be selected so that the inclination of the pin 15 in the position A shown is the same as that experienced by the pin 15 in positions B or D as a result of the torsional deformation of the inner arm part 4. This ensures that the same conditions prevail in all positions of the outer arm part 6, in particular that the load to be moved always remains at the same height and can therefore neither move out of a position taken on its own nor require additional force if it is to be moved from an extreme position (B or D) to another position (A or C).

Fig. 5 shows a variant of a lifting device in which a column 25 carries at its upper end a sleeve 27 which is pivotally mounted on it about a pivot pin 50 and to which a support head 26 is connected at its upper end. The inner arm part 29 is articulated to the support head 26 by means of a joint 28 with a horizontal axis, which is connected at its other end by means of the joint 30 with

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the housing 31. Parallel to the inner arm part 29 and above it is arranged a push rod 32, which is also connected by joints 33 and 34 on the one hand to the support head 26 and on the other hand to the housing 31.

The sleeve 27 has a cantilevered bracket 35 which carries a fluid cylinder 36, whose piston rod 37 engages the inner arm part 29. By actuating the fluid cylinder 36, the parallelogram arm containing the inner arm part 29 and the push rod 32, and thus the housing 31, can be raised or lowered.

In the housing 31, for example, the outer arm part 38, which carries the load hook 39 at its angled end, can be pivotally mounted in a similar manner as shown in Figs. 3 and 4.

The conditions shown in Fig. 2 are also the same for this variant of a lifting device. Their negative effects can therefore be remedied in the same way as described there, for example by designing the joint in the housing 31 in the same way as shown in Figs. 3 and 4.

However, this variant of a lifting device also allows for other options to compensate for the disadvantages. In Fig. 6, which shows a longitudinal section through the housing 31, the bearing of the pin 40, which is connected to the outer arm part 38, is shown. The usual plain bearing used there is self-explanatory.

From Fig. 7, which shows a cross section along line VIi-VlI of Fig. 6, it can be seen that the bolt 34 is surrounded by a bushing 41 made of an elastically flexible material, which is inserted into an eye 42 of the push rod 32. When the outer arm part 38 is loaded, the bushing 41 can give way elastically, whereby an inclination of the pin 40 relative to the vertical is achieved.

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Finally, Fig. 8 shows a further variant in which a head part 43 is mounted on the pin 34, into which a bolt 44 is screwed, which has a collar 45 approximately in its middle. This bolt engages in a longitudinally displaceable manner in a bore 46 of the push rod 32, in which two compression springs 47 are housed, which are attached to the collar with their mutually facing ends.

45 and with their other ends on one side on a hole in the

46 inserted snap ring 48 and on the other hand on a pressure piece 49 closing the bore 46.

If a force is applied to the outer arm part 38, this will result in the right compression spring 47, which is supported on the collar 45 and the pressure piece 49, being compressed, whereby the pin 40 is inclined relative to the vertical. If the outer arm part is pivoted from position A shown here to position C, the situation is reversed in that the compression spring 47 shown on the left is then loaded, whereby a similar inclination of the pin 40 is achieved.

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Reference symbol I is

1 pivot pin

2 pillar

3 Sleeve

4 inner arm

5 Joint

6 outer arm

7 Leadership

8 Telescopic rod

9 load hooks

10 Lifting drive

11 Rope

12 circular arcs

13 circular arcs

14 Housing

15 cones

16 Inner ring

17 Inner ring

18 Spacer sleeve

19 Distance sleeve

20 Snap ring

21 Outer ring

22 Outdoor part

23 Long hole

24 elastically flexible material

25 Column

26 Support head

27 Sleeve

28 Joint

29 inner arm

30 joint

31 Housing

32 Push rod

33 Joint

34 Joint

35 Console

36 fluid cylinders

37 Piston rod

38 outer arm

39 load hooks

40 cones

41 rifle

42 Eye

43 Headboard

44 bolts

45 fret

46 Bore

47 compression springs

48 Snap ring

49 Pressure piece

50 pivot pins

Claims (6)

2-15.006 DE Zasche Fördertechnik GmbH Gewerbestraße 23 86720 Nördlingen Protection claims 1. Boom for a lifting device, which is formed from an inner partial arm (4, 29) which is pivotably mounted at one end about a vertical pivot pin (1, 50) and which is connected at the other end by means of a joint (5) with a vertical pivot axis to an outer partial arm (6, 38) which carries a load-bearing means (9, 39) at its free end directly or with the interposition of further components, characterized in that parts of the inner partial arm (4, 29) or of the joint (5) are designed to be elastically flexible in a plane which contains the pivot pin (1) and the joint (5) in such a way that, under the action of a load carried by the load-bearing means (9, 39), a deviation of the longitudinal axis of the joint (5) from the vertical results which at least approximately corresponds to the deviation of this longitudinal axis from the vertical which occurs as a result of the torsional deformation of the inner partial arm (4, 29) when it is at an angle of 90° to the outer part arm (6, 38). 2. Boom according to claim 1, characterized in that the joint (5) connecting the two partial arms (4, 6) has two pivot bearings (16, 17; 21, 22) arranged at an axial distance from one another, which have at least one, one 2-15.006 EN - 2 - Pin (15) surrounding an outer part (22), wherein at least the outer part (22) of one pivot bearing is mounted in an elongated hole (23) of a housing (14) surrounding it, and wherein the elongated hole (23) extends in the direction of the longitudinal axis of the inner partial arm (4) and in the transverse direction corresponds to the external dimension of the outer part (22), while in the longitudinal direction it exceeds this, and wherein the cavity between the outer part (22) and the elongated hole (23) is filled with an elastically flexible material (24). 3. Boom according to claim 1, in which the inner partial arm (29) has a push rod (32) arranged above or below and parallel to it, and wherein the partial arm (29) and the push rod (32) are connected at their two ends by means of joints (28, 30; 33, 34) with horizontal axes on the one hand to a support head (26) on a sleeve (27) surrounding the pivot pin and on the other hand to a housing (31) surrounding the joint, characterized in that an elastically flexible element (41, 47) is integrated into the push rod (32). 4. Boom according to claim 3, characterized in that the elastically flexible element is formed by two compression springs (47) which are inserted into a longitudinal bore (46) of the push rod (32) and are supported there with their opposite ends on projections (48, 49) of the bore (46), while their mutually facing ends rest on a collar (45) of a bolt (44) mounted longitudinally displaceably in the longitudinal bore (46). 5. Boom according to claim 3, characterized in that the joints with horizontal axes on the push rod are formed by bearing bolts (34) which engage in eyes (42) surrounding them, with a bushing (41) made of elastically flexible material being inserted at least on one joint between the bolt (34) and the eye (42). 6. Boom according to claim 2, 3 or 5, characterized in that the elastically flexible material is a polymeric material, in particular a thermoplastic material.