GB2030256A

GB2030256A - Lock and release load lifting device

Info

Publication number: GB2030256A
Application number: GB7926315A
Authority: GB
Original assignee: PRAT J
Current assignee: PRAT J
Priority date: 1978-07-27
Filing date: 1979-07-27
Publication date: 1980-04-02
Also published as: DE2930599A1; FR2431987B1; IT7912684A0; FR2431987A1; IT1124137B

Abstract

A load lifting tongs device comprises two spaced frames 1, 2 carrying tongs 10 and interconnected by a "pull-push" type lock and release mechanism which includes a ratchet detent 13 on a slide 12 cooperating with a stop 24 on a runner 19 slideable in the slide. Each time the tongs are lowered, and the bottom frame 2 engages a load or sets down a load, the ratchet detent 13 is turned through part of a revolution by the stop 24 and on alternate lifts the ratchet detent 13 engages in a hole 23 on the runner 19 to hold the tongs 10 open. <IMAGE>

Description

SPECIFICATION Lever mechanism for engaging and releasing a load The present invention relates to a lever mechanism for engaging and releasing a load automatically, so that it can be manoeuvered without danger by one man, the automation being obtained by simple and purely mechanical means.

According to the invention, there is provided a lever mechanism comprising an upper frame and a lower frame connected by levers having members for engaging a load when the spacing of the two frames reaches a first value, referred to as engagement spacing, and an arrangement which prevents the frames, when their spacing increases to a second value, referred to as intermediate spacing, less than the first value from moving further apart if they have not immediately before come together to a third spacing value less than the intermediate value, referred to as releasing spacing.

The mechanism preferably includes a means to prevent the spacing of the frames from becoming less than the releasing spacing.

There is also provided an engaging member for a ratchet suitable for use in a lever mechanism according to the invention, comprising a hollow body having one aperture therein having two parallel edges and a stop extending into the body parallel to the edges.

There is further provided an engaging member comprising a ratchet, suitable for use in a lever mechanism according to the invention, wherein the ratchet is mounted on the inside of a hollow body having an aperture therein, a part of the ratchet projecting from the body through said aperture at least in some positions of the ratchet.

In the accompanying drawings: Figures 1 to 4 are plan views of an embodiment of a mechanism according to the invention in four successive operating positions.

Figures 5 to 8 are partial sectional views on an enlarged scale, illustrating the positions of the cogging member and corresponding respectively to Figures 1 to 4, and Figure 9 represents an intermediate position between Figures 7 and 8.

Figures 10 and 11 are partial perspective views of the parts constituting said arrangement.

A lever mechanism intended to pick up a load C having four lugs E comprises a rectangular upper frame 1 and a rectangular lower frame 2 of smaller dimensions than the upper frame. Four holes 4 are provided in the two longest front and rear faces 3 of the frame 1 in the vicinity of the ends of the faces.

Each hole 4 receives one end of a lever 5 whose other end is hinged to the front or rear face 6 of the frame 2 in the vicinity of a corner thereof corresponding to the corner where the hole 4 is situated.

Hinged at an intermediate point 7 of each lever 5 is a lever 8, one end of which is hinged at an intermediate point 9 of the face 3, while the other end carries a hooking bar 10 serving as a gripping member for engaging the lugs E. Engagement of the bars 10 with the lugs E is assisted by the provision of guide plates 11 on the levers 8. A parallelepiped slide member 12 (Figure 10) provided on the frame 1 extends downwardly from the centre of the frame 1. The slide member 12 has a ratchet 13 mounted rotatably on a horizontal pin 14 perpendicular to the faces 3 and 6 in a hollow body 15 provided with an aperture. The ratchet 13 has two V-shaped notches. One wall 18 of each of the notches is parallel to one wall of the other notch. One of the walls 18 forming the notch is longer than the other wall of the same notch.When the ratchet 13 turns, the free ends of the walls 18 project from the body 15 through the aperture 16. Engaged into the slide 12 at the bottom there slides a parallelepiped runner 19 (Figure 11) which is provided on the frame 2 and which comprises a hollow body 20 having an aperture 21 with a lower edge 22 and an upper edge 23 parallel to the pin 14. The lower edge 22 is at the same level as a stop 24 which is parallel thereto and which serves as a catch for the ratchet 13. The distance between the edge 22 and the stop 24 is less than the largest dimension of the ratchet 13. The edge 22 and the stop 24 are equidistant on either side from the vertical plane passing through the pin 14.

A hook 25 is provided on the frame 1 and enables it to be suspended on a pulley-block P.

The lever mechanism functions in the following manner: In the position of Figure 1, the upper edge 23 of the aperture 21 is situated at the bottom of one of the notches of the ratchet 13 and prevents the ratchet from turning. The frame 2 is suspended on the frame 1 by the runner 19. The spacing between the frame 1 and the frame 2 is intermediate. This spacing cannot increase, since the engagement between the ratchet 13 and the edge 23 prevents any relative translatory separating movement of the runner 19 and the slide 12.

However, the runner 19 can penetrate further into the slide 12. This is what happens (Figure 2) when the frame 2 comes in contact with the upper face of the load C to be lifted. When the runner 19 has engaged sufficiently in the slide 12, the stop 24 which serves as a catch causes the ratchet 13 to turn anticlockwise, so that the ratchet 13 exceeds the position of rotation in which the edge 23 which is removed from the ratchet 13 due to the coming together of the runner 19 and of the slide 12 enters the notch. The rotation of the ratchet 13 is stopped by the lower edge 22 which serves as a stop. The runner 19 can no longer penetrate further into the slide 12.

In this position of maximum proximity, referred to as releasing spacing, because since the ratchet 13 has turned and has gone beyond the edge 23 a considerable spacing larger than the intermediate spacing is permitted, the moving ends of each pair of levers 5, 8 have approached one another and moved away from the centre of the lever mechanism as defined by the vertical plane of symmetry passing through the centres of the faces 3, 6 of the frames.

The bars 10 have passed round the lugs E and are at a certain distance therefrom.

The frame 1 is then raised via the pulley-block P.

The runner 19 tends to emerge from the slide 12. It is prevented from so doing when the spacing between the frames 1 and 2 reaches a certain value, referred to as engagement spacing, for which the bars 10 lift the load C by the lugs E (Figure 3).

During this separating movement the upper edge 23 of the aperture 21 has turned the ratchet 13 by pushing it via the long inactive face and has rotated it into the position illustrated in Figure 7.

The load C is then transported. The pulley-block P is lowered in the desired position of the load. The assembly of lever mechanism and load C descends until the load C is supported by a fixed support. The frames 1 and 2 begin to approach one another The bars 10 leave the lugs E. During this coming together the stop 24 causes the ratchet 13 to turn by engaging one of the ends of the tip of a notch (Figure 9) and penetrates as far as the bottom of this notch by sliding on a face 18. When the stop 24 is at the bottom of the notch (Figure 8) the ratchet 13 no longer turns.

The runner 19 cannot penetrate further into the slide 12. The frames 1 and 2 no longer approach one another. When the frame 1 is raised by pulling via the pulley-block P, the runner 19 partly emerges from the slide 12 until the intermediate spacing is reached, whereupon the edge 23 penetrates to the bottom of the other notch of the ratchet 13. The position of Figure 1 is regained.

Claims

1. A lever mechanism comprising an upper frame and a lower frame connected by levers having members for engaging a load when the spacing of the two frames reaches a first value, referred to as engagement spacing, and an arrangement which prevents the frames, when their spacing increases to a second value, referred to as intermediate spacing, less than the first value, from moving further apart if they have not immediately before come together to a third spacing value less than the intermediate value, referred to as releasing spacing.

2. A mechanism according to claim 1, further comprising means to prevent the spacing of the frames from becoming less than said releasing spacing.

3. A mechanism according to claim 1 or 2, wherein said arrangement comprises a runner provided on the lower frame and mounted so as to be slideable in a slide provided on the upper frame, and a ratchet mounted on the slide adapted to engage the runner.

4. A mechanism according to claim 3 when appendantto claim 2, wherein the means to prevent the spacing of the frames from becoming less than the releasing spacing comprises a stop which is situated on the other side of the portion of the runner which engages the ratchet in relation to the axis of the ratchet and which prevents the ratchet from turning at the releasing spacing.

5. A mechanism according to claims 3 or 4, wherein the ratchet has two notches and the runner comprises an engaging portion preventing the ratchet from turning at the intermediate spacing.

6. A mechanism according to claim 5, compris ing an aperture in a face of.the runner, the upper edge of the aperture constituting said engaging por tion.

7. A mechanism according to claim 6 when appendantto claim 5, wherein the ratchet has only two V-shaped notches, one of the walls of each notch being parallel to one of the walls of the other notch.

8. Engaging member for a ratchet, suitable for use in a lever mechanism according to any of claims 1 to 7, comprising a hollow body having an aperture therein having two parallel edges and a stop extending into the body parallel to the edges.

9. Engaging member comprising a ratchet, suitable for use in a lever mechanism according to any of claims 1 to 7, wherein the ratchet is mounted on the inside of a hollow body having an aperture therein, a part of the ratchet projecting from the body through said aperture at least in some positions of the ratchet.

10. A lever mechanism substantially as herein described with reference to the accompanying drawings.