GB2291616A - Crimping tool - Google Patents

Abstract

A crimping tool has a pair of dies closeable together under the action of a cam driven by a lever operated ratchet and pawl mechanism. A first handle 10 is integral with a main body 12 and a fixed jaw 14. A second handle 16 is pivoted to the main body. A second jaw is provided on a sliding plate 18 and is guided by pins 20, 22 running in slots 24, 26. Movement of the second handle turns a ratchet wheel 34, and attached arm 32, unidirectionally with the aid of pawls 36, 38. A cam follower 30 on plate 18 engages a cam surface comprising cam lobes 46, 48, 50, 52 on a cam 32. The movable jaw is forced towards the fixed jaw under successive operation of lever handle 16. The cam may have one or more cam lobes over its surface, each of varying profile. <IMAGE>

Description

CRIMPING TOOLS This invention relates to crimping tools of the kind comprising a pair of dies which are relatively moved for example to crimp a terminal to a wire.

A simple and conventional tool for the purpose comprises a pliers like mechanism in which the handles are moved together to close the jaws together. The difficulty with this is that the pressure required at different stages of the crimping operation is different.

Thus, to close the jaws towards the workpiece requires little or no effort. To close the jaws further so as possibly to close the sheet metal upon the wire before tulle wire is contacted requires more effort, and to complete the crimp when the sheet metal is forced into tight gripping contact with the wire requires high pressure. It is also disadvantageous to have the jaws pivotally moved together and accurate crimping requires the jaws to remain in parallel planes as they are closed.

It is also known, in another pivoted jaw arrangement in (P 1593401 to provide a crimping jaw which is ratchet operated, so that a hand lever can be moved repeatedly in the losing direction, with te ratchet holding tlie jaws between successive operating strokes. This may enable the mechanical advantage to l)e selected so that particularly high pressure can be achieved , but this means that a large number of working strokes may be required in the earlier part of the crimping cycle simply to tal:e up the clearance before the operation properly begins.

EP 0058375 uses a toggle linkage having the centre l)oint nf the toggle acting as a cam follower and the ends F that toggle connected jy further links to a pair of jaws which are guided for parallel movement and closing As the linkage is cam is placed the ends of the linkage separate, i.e. the toggle straightens, and so the machanical advantage changes, albeit to, a relatively small amount, during the closing movement.However, there are a particularly large number of parts and the sliding surfaces absorbing power in this mechanism which makes it relatively inefficient.

GB 1062491 provides a different mechanism to the same effect where the cam displaces what is effectively a piston and cylinder mechanism bodily for mere die closing and then displaces the piston relative to the cylinder for the final part of the crimping operation, against relatively high spring pressure.

The object of the present invention is to provide improvements.

According to the invention a crimping device comprises a fixed die and a moveable die guided for sliding towards and away from the fixed die, a lever associated with a ratchet and pawls mechanism whereby the ratchet may be turned unidirectionally by a series of lever strokes, a cam fast with tlie ratchet and having a least one cam lobe extending angularly over the same angle as a plurality of ratchet teeth, said moveable die being displaceable by a cam, whereby angular displacement of the cam lobe to effect one complete cycle of reciprocation of the moveable die is effected by a multiplicity of lever strokes, and the mechanical advantage (lever movement: die movement ratio) depends solely upon the cam contour.

In a tool according to the invention, the effort applied to the lever is translated substantially directly to the crimping operation without substantial frictional 1 osses.

The dies may be interchangeable to suit different tpr-nljnals and the lilce to be crimped, and interchange of different cams with tulle same ratchets map provide for .different Riser requirements.

A presently preferred embodiment of the invention is now more particularly described with reference to the accompanying drawing wherein the sole view is a somewhat diagrammatical elevation of a crimping tool according to the invention.

Turning now to the drawing, the tool shown therein has a first handle 10 made integral with the main body section 12 and a first jaw 14. A second handle 16 is pivoted on the main body. A second jaw is provided on a sliding plate 18 guided for parallel movement by pins 20, 22 running in slots 24, 26.

Poth jaws may form crimping dies, or more usually and as illustrated, detachable and replaceable dies 26, 28 will be used enabling one tool to be employed with different crimping dies.

The plate carries a cam follower or roller 30 engaging cam 32 which (in this instance) is fast with ratchet wheel 34, both being journalled on the main body.

Tlie angular positions of the ratchet and cam are controlled by a pair of pawls 36, 38 both of which are spring loaded.

Pawl 38 is effective between pivoted lever handle 16 and the ratchet wheel, so that when the handle moves in the direction of arrow A it turns the ratchet likewise, t in the reverse direction of movement of the handle, reverse direction of movement of the ratchet is prevented l)y tloe pawl 36. Pawl 38 runs across the ratchet teeth in that reverse movement of the handle.Pawl 36 is prilla r Ii y intended to ensure that the ratchet wheel turns c,nly in the clockwise direction, but both pawls can be maiorall y released if required, in order to enable the jaws to lie opened part-way through an operational cycle.

Tulle cam in this embodiment has four recesses, one of which i shown embracing the roller 30, and the others 4 , 42 and 44 are equi-spaced about the cam. between each two recesses is a cam lobe 46-52.

Since there are four lobes equi-spaced, it will be appreciated that the cam turns through about 900 between registration of one recess with the roller 30 and registration of the next recess with the roller 30. The relationship of handle angular movement to ratchet and cam angular movement is 1:1 in this embodiment, so that the handle needs to move a like total distance of 900 in the arrow A direction to cause such progression. This may be accomplished by way of for example two 450 strokes, or one 600 stroke and a smaller stroke, or any other combination limited only by the available angular movement of the handle and the angular spacing of the ratchet teeth. Finer teeth, i.e. a greater number of teeth on the ratchet, enable smaller movements to be possible.

The cam lobes 46-52 are of different height (radial dimension from the axis of the ratchet wheel) and so are, or may be, the recesses including 40-44.

Effectively the die 26 is displaced in the direction of arrow B, progressively and successively by cam lobes, as each in turn is brought into operative relationship and used. In general it is usually preferred for the first lobe to effect take up a free space, that is close the dies on to the as yet undeformed terminal, for the second lobe to close the terminal on the cable which may involve a movement of e.g. only half the distance of that accomplished by the first lobe, for the third lobe to effect the required crimping and the fourth lobe basically repeat the third lobe operation or possibly close the terminal for a final minute amount. At the conclusion of the fourth lobe operation the roller has returned to the first recess and so the dies will be returned or will be free to return to the illustrated and maximum separation position. If desired a spring may return them to that position.

The mechanical advantage between the ratchet and die is dependant upon the cam profile or in other words the lever displacement of the plate 18 for unit angular movement of the handle. The result is that a small displacement can be achieved by the full 90 cam movement in the final stroke, corresponding to a high pressure final crimping operation, whilst enabling the large displacement in the earlier stroke.

If a smaller number of cam lobes is desired, for example in light duty operations where two strokes may be sufficient to close and crimp, the first and third lobes and recesses may be identical, and the second and fourth different but also identical to one another. Effectively the device would then perform two crimping operations for a complete revolution of the cam. Alternatively the device could have less, or more lobes.

In one possibility a lever is movable e.g. through 90 degrees to move the cam to take roller 30 from one recess to the next and perform the whole operation in this 90 degree movement. In the pivot part of this movement, e.g. 30 degrees angle, the cam surface is steep, to induce jaw closing against little resistance, in a second e.g. 30 degree movement the angle is shallower to close the jaws a smaller extent to fold the sheet metal of a terminal about the wire of a cable, and the last 30 degree of the movement the crimp is completed and the jaws re-opened for a new cycle of operations.

To perform the same cycle but with a plurality of short lever strokes, the ratchet may be employed. The number of strokes will depend upon the number of teeth of the ratchet wheel 34 and/or the lever handle could be connected to the ratchet wheel by a gear reduction train so that each complete stroke of the handle corresponds to only a small number or even only a single ratchet tooth.

It will be appreciated that the multi-lobe cam of the drawing can take either of two forms, namely 1) Each cam lobe is identical and hence each is used to complete a single crimping operation.

2) Each cam lobe is different from the next one, so that each contributes towards a part of the crimping operation: in this case the recesses between lobes serve little useful purpose, in fact resulting in a degree of separation of the jaws/dies.

In a different possibility a cam may have only one recess in the 360 degree so that the cam turns through a complete revolution to effect a single crimping operation.

Claims (10)

1. A crimping device comprising a fixed die and a moveable die guided for sliding towards and away from the fixed die, a lever associated with a ratchet and pawls mechanism whereby the ratchet may be turned unidirectionally by a series of lever strokes, a cam fast with the ratchet and having a least one cam lobe extending angularly over the same angle as a plurality of ratchet teeth, said moveable die being displaceable by a cam, whereby angular displacement of the cam lobe to effect one complete cycle of reciprocation of the moveable die is effected by a multiplicity of lever strokes, and the mechanical advantage (lever movement: die movement ratio) depends solely upon the cam contour.

2. A device as claimed in Claim 1 wherein a first pawl is arranged to hold the ratchet against reverse rotation and a second pawl is effective between the lever and the ratchet for forward rotation.

3. A device as claimed in Claim 1 or Claim 2 wherein a plurality of cam lobes are provided each arranged to effect a complete and like die reciprocation.

4. A device as claimed in Claim 3 wherein a recess is provided between each two adjacent lobes, and the moveable die is spring urged to an open position, whereby upon completion of the crimp the lobe moves past the cam follower which enters the recess to reopen the dies automatically.

5. A device as claimed in any preceding claim wherein the multiplicity of lever strokes per lobe is at least three strokes.

6. A device as claimed in Claim 5 wherein the ratchet is provided with a least four times as many ratchet teeth as the number of lobes on the cam.

7. A device as claimed in Claim 3 wherein the ratchet and cam are fast with one another.

8. A device as claimed in Claim 3 wherein the ratchet is connected to the cam by a gear train.

9. A device as claimed in Claim 4 wherein the cam has four successive cam portions.

10. A crimping device substantially as described.