EP0157073A1

EP0157073A1 - Gripping member for jack

Info

Publication number: EP0157073A1
Application number: EP84850356A
Authority: EP
Inventors: Hans Wahlgren
Original assignee: Kaller Konsult AB
Current assignee: Kaller Konsult AB
Priority date: 1983-11-25
Filing date: 1984-11-14
Publication date: 1985-10-09
Also published as: SE8306533D0; NO844684L; NO159526C; DE3463752D1; EP0157073B1; NO159526B; SE449608B; SE8306533L; ATE27256T1

Abstract

Gripper for moving heavy loads, including two hydraulic cylinders (60, 61) intended for being anchored to a support point at one end, and with their other end to be pivotably connected to a movable part (1). Two opposing cuneiform jaws (19 and 20) for gripping the load (55) between them are movably arranged on the movable part in association with pivotable rockers (6 and 7) with guide surfaces (17 and 18) for forcing or releasing the jaws against or away from the load in response to thrust or withdrawal of the rams (68, 69) of the hydraulic cylinders. The movable part is a flat base plate (1).

Description

The invention relates to a gripper for moving heavy loads. Grippers of this kind are known and include at least one hydraulic cylinder, which at one end is intended to be anchored at a support point, and at its other end is pivotably connected to a movable part, there being arranged at the movable part opposing cuneiform jaws for gripping the load between themselves in the movable part, there being seatings with guide surfaces for urging the jaws to, and away from, the load in response to the thrust or withdrawal of the hydraulic cylinder ram. The loads in question here are in order of magnitude of tens of tonnes.
A disadvantage with the known gripper is that they cannot directly grip the load which is to be moved, and each gripper requires a separate pull rod, in which the load is anchored and around which the gripper grips. Under the action of at least one hydraulic cylinder the gripper then moves the pull rod with short distances corresponding to the stroke of the hydraulic cylinders, and the pull rod thus pulls the load after it. Another disadvantage with the known gripper is that they do not afford satisfactory gripping of elongate loads, e.g. beams or girders of varying width, e.g. such as taper or are conical along their length. The known grippers require a pull rod with a constant cross-section along its length. Another disadvantage with the known gripper is that hey are mounted in a cradle for taking up angular variations in the load, e.g. such as occur when the free end of a beam in a horizontal position sways as it is moved by the gripper, or when a load lifted vertically upwards by the gripper starts to swing. Such a cradle requires complicated means for anchoring the cradle and thereby the gripper at a fixed point, e.g. a foundation. Furthermore, the grippers in the art do not allow moving an elongate load which forms an angle to the longitudinal axis of the gripper.
The present invention has the object of achieving a gripper of the kind discussed in the introduction, which is not burdened with the above-mentioned disadvantages. The gripper in accordance with the invention shall thus be able directly to grip the load which is to be moved, and thereby make unnecessary the use of separate pull rods or steel ropes with which the load is anchored. The inventive gripper shall further be able to grip loads having varying cross-section along their length. Futhermore, and perhaps most important, the inventive gripper shall be able to accommodate angular variations in the load, thereby avoinding the need of a separate cradle, thus enabling the conventinal hydraulic cylinders associated with the gripper to be attached directly to a substructure in the case where the gripper is stationary and moves a load. The gripper can be fastened directly to the load in the case where the gripper moves along a beam or some other stationary member while pushing or pulling the load in front of or after itself. Similarly with the known grippers, the gripper in accordance with the invention shall permit movement of the load both vertically and horizontally. As just implied, the gripper shall be able to pull itself forward on a stationary substructure, e.g. a rail, by gripping it while moving the load. In this case, a slab of TEFLON is preferably placed between the gripper and the stationary substructure, e.g. the rail, and the whole unit, TEFLON slab and gripper, will then serve as a bearing between the load carried by the gripper and the substructure, whereby the need of separate bearing means, e.g. conventional rollers, is avoided to a large extent.
Different embodiments of the invention will now be described below in conjunction with the accompanying drawings, on which

Figure 1 is a plan view of the gripper in accordance with the invention,
Figure 2 is a side view of the gripper in Fig. 4 along the line II-II,
Figure 3 is a side view of the gripper in Fig. 4 along the line III-III,
Figure 4 is a plan view of a known gripper,
Figure 5 is a plan view of the inventive gripper when moving a load in a horizontal direction,
Figure 6 is a side view of the gripper illustrated in Fig. 5,
Figure 7 is a simplified plan view of a double gripper arrangement in accordance with the invention, intended for moving loads in a vertical direction,
Figures 8-11 illustrate in plan view from above a plurality of different attitudes for the jaws and rockers for moving beams of different types.

The inventive gripper illustrated in Figure 1 includes a movable part in the form of a flat rectangular base plate 1 with two lugs 2, 3 to which hydraulic cylinders are pivotably attached with the aid of pins 4, 5. Two seatings or rockers 6, 7 are pivotably attached to the base plate 1, such that they are opposite each other and symmetrical about a center line 8. The rockers 6 and 7 are pivotably mounted in the base plate by pivot pins 9 and 10, which are a shrink fit in the rockers and extend through the base plate 1, on the underside of which they are retained with the aid of retaining plates 11 and 12 and bolts 13 and 14, threaded in the respective pin 9 and 10.
Each rocker 6 and 7 is a plate configured substantially as a right-angular triangle with a cross portion 15 and 16 instead of its acute angle, integral with the rest of the plate and at right angles to the hypotenuse of the triangle. The hypotenuse forms a guide surface 17 and 18 for a wedging jaw 19 and 20. Each jaw is a flat plate in the form of a truncated, substantially right-angular triangle with its hypotenuse provided with serrations 21 and 22. The points of the serrations are directed in the direction of trabel for the unillustrated load, this direction being indicated by the arrow 23 in Figure 1. The (geometrical) adjacent side of each jaw 19 and 20 forms a surface engaging against the respective guide surface 17 and 18. Each jaw 19 and 20 is glidable along the respective guide surface 17 and 18, under the guidance of a guide rod 24 and 25 extending with clearance through holes 26 and 27 in the cross portion 15 and 16. Each guide pin 24 and 25 is threaded into the (geometrical) opposite side 28 and 29 of the jaw 19 and 20. A compression spring 30 and 31 is biased to thrust the respective jaw in a direction counter to that of the arrow 23. The movement of the jaws in said direction is limited by adjustment nuts 32 and 33, which are screwed onto the respective threaded guide rod 24 and 25. Each rod is provided with a cross handle 34 and 35. To limit the movement of each jaw 19 and 20 in the direction of the arrows 36 and 37 there are set screws 38, 39 threaded into holes 40 and 41 in the cross portion 15 and 16 of the rockers 6 and 7.
As is most clearly apparent from Figure 3, the pivot pin 10 is a shrink fit in a hole 43 through the rocker 7. The pin 10, non-rotatably attached to the rocker 7, passes with clearance through a hole 45 in the base plate 1, as previously mentioned. The same applies to the pivot pin 9 which is a shrink fit in a hole 42 through the rocker 6. The pin 9 passes with clearance through a schematically illustrated hole 44 in the base plate. Each rocker with associated jaw is covered by a protective plate 46 and 47 to form a jaw housing.
The function of a known gripper is explained with the aid of Figure 4. The known gripper 48 includes two pairs of jaws 49, 50 alternatingly gripping a pull rod 51, and by unillustrated jacks thrusting the pull rod short distance in the direction of the arrow 52. The gripper 48 is pivotably mounted in a cradle 53, and the pivot point is schematically illustrated at 54. A schematically illustrated beam 55 is to be moved in a direction of the arrow 52 by the gripper. The pull rod 51 is attached to the beam in the schematically illustrated manner for this purpose. The cradle 54 is rigidly anchored in a substructure 56. As mentioned in the introduction, the known gripper only permits gripping a rod or a cable 51 of constant cross-section, and thus the gripper does not allow gripping the beam 55 itself. The beam 55 now has to be turned to the position illustrated by dashed lines,for example as a result of the beam being a structural member in abridge with a highway curving in the same direction. This means that the gripper 48 must also be turned in the cradle 53 round the pivot pin 54 so that the pull rod 51 will not collapse due to non-uniform load distribution. However, it is not sufficient that the gripper 48 turns a corresponding angle. The attachment of the pull rod 51 must also be moved from the fixed point 57 to the fixed point 58. It is thus clear that the known gripper 48 cannot allow moving a load, e.g. a beam, in a direction forming an angle to the longitudinal axis of the gripper. Such movement of a load is possible with the gripper in accordance with the invention, since the jaws 5 and 7 turn a corresponding angle about the pivot pins 9 and 10, while retaining the load between them, and the unillustrated hydraulic cylinders can maintain their anchorage and continue to thrust or pull the base plate 1 in the direction of the arrow 23, or its reverse direction.
Different applications of the inventive gripper will now be described in conjunction with Figures 5-11. Figures 5 and 6 illustrate the inventive gripper 59, which is anchored to a cradle 62 with the aid of two hydraulic cylinders 60, 61 forming the stationary part of the gripper, the cradle resting on two supports 63, 64 such as girders resting on bridge columns. The gripper is to move a beam 65 in the direction of the arrow 66 towards a support not illustrated on the drawing, which is at a distance corresponding to the length of the beam 65 from the support 64. As will be seen from Figures 5 and 6, the width and depth of the beam changes at a portion 67.
The inventive gripper 59 performs a forward advancing movement of the beam 65 by the hydraulic cylinders 60, 61 thrusting out their rams 68, 69 with the aid of unillustrated conventional means, the rams being pivotably mounted in the lugs 2, 3 of the base plate 1. The other ends of the hydraulic cylinders are anchored on the stationary cradle 62. The base plate 1 is moved by the thrusting movement from the position illustrated in Figure 6 by full lines to the one illustrated by dashed lines. The jaws 19, 20 are forced against the lower flange on the beam 65 as the result of the slopin guide surfaces 17, 18 until the engagement is sufficiently strong for the beam finally to accompany the movement of the base plate 1. The amount of movement is dependent on the stroke of the hydraulic cylinders and may be about 25 mm. When the fully thrust-out position of the rams has been achieved, they are given a withdrawal movement with the aid of the already-mentioned conventional means. The jaws relinquish their grip on the lower flange and move realtive the rockers 6, 7 against the bias of the compression springs 30, 31 until they abut against the set screws 38, 39, which have been pre-set so that there is no risk of the guide rods 24, 25 becoming damaged. During this movement the serrations 21, 22 glide along the beam. If the load has a section which is conical, e.g. one such as the portion 67, the jaws will turn during the withdrawal movement of the hydraulic cylinders and orient themselves such that their serrations 21, 22 engage against the conical section. It is also clear that if the section of the load is such that one edge is straight while the other is inclined towards it, then only one of the two rockers 6, 7 will pivot.
It is obvious that adjustment to different load widths can take place by exchanging the base plate 1 for one having a distance between the holes 44, 45 which is greater or less than the one shown, to allow gripping wider or narrower loads, as well as the respective lengths of the jaws and guide surfaces 17, 18 also allowing adjustment of the gripper to different load widths.
Figures 5 and 6 illustrate movement of a load by a gripper with a fixed anchoreage. It is also possible directly to attach the gripper to the load such as to move both gripper and load, either horizontally or vertically. A gripper arrangement with these properties is obtained by conventionally arranging two gripper base plates and their details in tandem and with hydraulic cylinders 60 and 61 between them, as illustated in Figure 7. The units comprising base plate 1 with details, 60 and 61 are in accordance with those already illustrated, and an additional unit I' corresponding to the gripper illustrated in Figure 1 is connected to the hydraulic cylinders. The serrations in the first-mentioned unit face the same way as the serrations in the additional unit 1'. With the aid of conventional means the tandem-connected gripping arrangement is controlled to move in the direction of the arrow 70 such that when the hydraulic cylinders thrust, the jaws 19', 20' in the unit 1' glide along the tractional bar 71, schematically illustrated by dashed lines in the Figure, while the jaws in the first-mentioned unit are in firm engagement with the tractional bar. The hydraulic cylinders 60, 61 then draw in their rams, whereon the jaws in the first-mentioned unit relinquish their grip, while the jaws in the unit 1' maintain a firm engagement with the tractional bar 71. If the tandem arrangement illustrated in Figure 7 is used for moving loads horizontally, the load is suitably placed on the unit 1'. A slab of TEFLON 72 is suitably placed between the base plate and the fractional bar 71 as a friction-decreasing means. The unit 1' carrying the load will then serve as a bearing between the load and tractional bar. The tandem-connected arrangement illusrated in Figure 7 can also climb vertically along a tractional bar, rail, beam or other unit while lifting the load below it.
Since each of the rockers in the inventive gripper is mounted on a pivot pin, and since there is no other mechanical link between the rockers, these can pivot in mutual independence in the manner illustrated in Figures 8-11. Although extremely exaggreated, it is illustrated in Figure 8 how both rockers may incline to the chain-dotted center line C of the base plate when advancing a beam, the width of which changes in the manner illustrated by dashed lines in the Figure. Figure 9 illustrates how the left-hand jaw housing by itself is at an angle to the center line C, while the right-hand housing is parallel to the center line when advancing a beam, the width of which changes in the manner illustrated by dashed lines in the Figure. Figure 10 ilustrates how both jaw housings are inclined in the same direction relative the center line C in advancing a beam which forms an angle to the center line C of the base plate.
Figure 11 illustrates the case occurring when the two hydraulic cylinders do not move the same distance during an advancing movement of the gripper, the base plate being on the skew but the housings turning relative the base plate while retaining their engagement with the load as it is advanced.
For adjusting the gripper to different load widths the base plate 1 may be exchanged for a base plate having a distance between the pivot pins 9, 10 appropriate to the width of the object to be gripped.

Claims

1. A gripper for moving heavy loads, including at least one hydraulic cylinder (60, 61) with one end intended for anchoring to a support point and its other end pivotably connected to a movable part (1) in the form of a flat base plate, there being coneiform gripping jaws (19, 20) arranged on the base plate for gripping the load (55) between them, rockers (6, 7) arranged on the base plate (1) and having sloping guide surfaces (17, 18) against which the jaws glide for being forced against or released from the load on thrust or withdrawal, respectibely,of the hydraulic cylinder ram (68, 69), characterized in that each rocker (6 and 7) is pivotably mounted on the base plate (1) by a pivot pin (9 and 10), the jaws thus being turnable independent of each other realtive the base plate.

2. Gripper as claimed in claim 1, characterized in that each pivot pin (9 and 10) is rigidly attached to the respective rocker (6 and 7) and extends with clearance through a hole (42 and 43) in the base plate (1).

3. Gripper as claimed in claim 1, characterized in that the base plate (1) is exchangeable for one having a distance between the pivot pins (9, 10) differing by a predetermined amount from the corresponding distance for another base plate, for adjusting the gripper to different load widths.

4. Gripper as claimed in claim 1, characterized in that each rocker (6 and 7) has the form of a flat plate configurated substantially as a right-angular triangle, having instead of its acute angle an extended cross portion (15 and 16) with two through bores, one intended to accommodate with clearance a guide rod (24 and 25) extending parallel to the hypotenuse of the triangle, and attached to the respective jaw (19 and 20), the rod being spring-biased and guiding the movement of the jaw along the guide surface (17 and 18) of the rocker, the other bore being adapted for accommodating a set screw (38 and 39) for limiting the movement of the jaw when the rams (68, 69) of the cylinder are withdrawn.

5. Gripper as claimed in claim 1, characterized in that each jaw (19 and 20) has the form of a flat plate configurated substantially as a right-angular triangle, the hypotenuse of which is provided with serrations (21 and 22) intended to engage against the load, the (geometrical) adjacent side of the triangle being intended to glide along the inclined guide surface (17 and 18) of the rocker (6 and 7).