GB2193673A

GB2193673A - Linked compound shears

Info

Publication number: GB2193673A
Application number: GB08619571A
Authority: GB
Inventors: George Marsden Macdonald
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-08-12
Filing date: 1986-08-12
Publication date: 1988-02-17
Also published as: GB8619571D0

Abstract

Shears comprise compound levers which are not hinged together at a common axle but have their own separate axles 6 which are separated from one another by the length of a link 7, that is in tension during operation and through the ends of which pass these separate axles. The pressure-exerting axles 4 of the compound levers do not just act at a single point near the ends of the scissor levers but act successively at a series of points 5 near the end of each scissor lever thus enabling the closing of the scissor jaws to be divided into a series of steps, each step corresponding to a full opening and full closing of the compound levers. The separation of the axles allows of an improved operation of the levers whose angular sweep now lies equally on either side of the line upon which maximum leverage occurs thus raising the magnitude of the minimum leverage of the compound levers. <IMAGE>

Description

SPECIFICATION Linked compound shears Technical field Hand tools that are operated by a pair of hinged levers which are brought together in the act of operation.

Background art Hand operated shears have their operating pressures increased by using a second pair of levers, the compound levers, to apply pressure to the scissor levers. The compound levers however up to the present time have had a common axle and this greatly limits the usefulness of the tool.

Disclosure of the invention The object of the invention is to provide a pair of compound cutting shears in which the angle of sweep of the scissor jaws does not suffer the limitation imposed by the use of a common axle for the compound levers. Principally the invention comprises a pair of compound shears whose compound levers have their own separate end axles (herein called link axles) which are separated from one another by the length of a rod or link through the two opposite ends of which these separate axles pass and which takes the tension that results from the closing action of the compound levers. The other axles of the compound levers (the pressure axles) apply pressure to the ends of the scissor levers. An operation of the compound levers from fully open to fully closed will close the scissor levers only a small amount.The compound levers are then reopened and the pressure axle moved along to the next axle seat of which there is a series. Successive operations of the compound levers take the scissor levers right through their full angular sweep. It can be appreciated that when a complete compound lever operation closes the scissor jaws fractionally instead of totally, the closing force on the scissor jaws is thereby greatly increased.

A useful feature of the invention is that the compound levers have an angular sweep that is bisected by the centre line of the link axle instead of the angular sweep coming to an end on this line as in existing types. This causes the minimum leverage to increase from L times cosine 6 to L times the cosine of half 8. where L is the lever length and 0 is the total angular sweep of the compound lever.

This is made possible only by the presence of the link member. It is obvious that the cutting jaws can be replaced by limbs that are capable of tasks other than shearing. An example would be limbs that can hold the two halves of a hole punch or the male and female parts of a press tool since it is possible to design great operating pressure into this invention.

Brief description of drawing The drawing in Fig. 1/1 shows a pair of multi-stroke linked compound shears in a position ready to commence the first of a series of fractional closures of the scissor jaws. The side view shows the slotted form of the end of the compound lever 3 into which fits the end of the important link member 7. It also shows the slotted form of the end of the scissor lever 2 into which fits the end of the compound lever 3. This is also shown by comparing the cutaway part of the left hand scissor lever 2 with the right hand scissor lever. In the ends of the scissor levers 2 are shown the series of supports 5 that take the pressure axles 4 of the compound levers.The closed position of the compound levers is shown in dotted form, and this shows that the levers can be on either side of the lines that pass through their link axles and which are parallel to the centre line of the whole drawing. This is shown as line 8 in Fig. 1/1.

Preferred embodiment This is shown in Fig. 1/1. The cutting jaws or scissor blades 1 are operated by the closing of the scissor levers 2, these being closed in a step by step fashion by the compound lever arms 3. The end of each compound lever 3 fits inside a slot cut in the end of the scissor lever 2. On either side of this slot (note the cutaway shown on the left hand scissor lever 2 and also in the side view) is cut a series of pairs of axle seats 5 in which successively rests the pressure axle 4 of the compound lever. The ends of the two compound lever arms 3 are slotted so as to admit the two ends of the link member 7 through which pass the two link axles 6. The pressure axle 4 is at first located on the precut line 8.

It is brought onto the post-cut line 9 by the full closure of compound lever 3. These levers are shown fully open in full line form and fully closed in dotted line form in Fig. 1/1. At this dotted line stage the second axle seat of the series of seats 5 has reached the pre-cut line 8 where it is ready to receive the pressure axle 4 of the compound lever 3. This axle is placed in the axle seat by the re-opening of compound levers 3. This re-opening of the compound levers 3 is accompanied by forward pressure against the material being cut.

This assists the pressure axle 4 in moving into the next axle seat of the series 5 of axle seats.

Exploitation of invention Since these multi-stroke linked shears can exert great cutting force, a motorist carrying one in the boot or trunk of his car could assist in the rescue of a traffic accident victim by cutting him free if he was trapped in his vehicle. At present very expensive power driven shears are used for this purpose. There are long armed shears on the market and the purposes for which they are intended can be achieved by the much smaller and therefore more convenient multi-stroke linked compound shears since these have greater leverage than the long armed shears whose arm length has to be kept within the limits of convenience.

Another possibility would result from re-placing the cutting jaws by limbs that can hold the male and female parts of a press tool.

This is reasonable since great operating pressure can be designed into this tool.

Claims

1. Compound shears in which the end axle of the two compound lever arms is not common to both levers but in which the levers have their own end axles, these being separated by the length of a link through the two opposite ends of which the two axles pass and which takes the tension imposed by the closing of the levers.

2. Compound shears as claimed in claim 1 in which during compound lever operation the levers can be on either side of the line that passes through the compound lever pressure axle and which is also parallel to the centre line of the shears.

2. Common shears as claimed in claim 1 with a series of axle supports cut in the ends of the two scissor levers for successively supporting the pressure axles of the two compound levers.

3. Compound shears as claimed in claims 1 and 2 in which during compound lever operation the levers can be on either side of the line that passes through the compound lever pressure axle and which is also parallel to the centre line of the shears.

CLAIMS Amendments to the claims have been filled, and have the following effect: Claims 1-3 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. Compound shears in which the end axle of the two compound lever arms is not common to both levers but in which these levers have their own end axles, these being separated by the length of a link through the two opposite ends of which the two axles pass and which takes the tension imposed by the closing of the levers, and in which the pressure axles of the two compound levers can be moved, one at a time, into each of a series of axle seats cut in the scissor levers, this being done by the re-opening of the compound lever arms.