WO1994020265A1

WO1994020265A1 - Rapid jaw adjustment for hand tools

Info

Publication number: WO1994020265A1
Application number: PCT/SE1994/000209
Authority: WO
Inventors: Ragnar STÅHLE
Original assignee: Fast Industriprodukter Hb
Priority date: 1993-03-12
Filing date: 1994-03-12
Publication date: 1994-09-15
Also published as: SE9300822D0

Abstract

The present invention relates to a hand tool that utilises a pair of jaws (3 and 4) to receive a workpiece (17) between them, said means comprising a handle (1) and a bar (2) fixed to the handle, on which bar one jaw (3) can be displaced and locked in optional position by means of the 'drawer effect' and one jaw (4) journalled pivotably in the handle (1) which is operated with the aid of a lever link (6, 7) supported by an abutment (12, 38) in the handle (1), said hand tool comprising a means to effect movement, said means comprising a lever (18) that can be operated with the same hand as is holding the tool in order to move the jaw displaceable along the bar.

Description

RAPID JAW ADJUSTMENT FOR HAND TOOLS

FIELD OF THE INVENTION

The invention relates to hand tools that utilise a pair of jaws to receive a • workpiece between them, said means comprising a handle and a bar fixed to the handle, on which bar one jaw can be displaced and locked in optional position by means of the "drawer effect" and one jaw journalled pivotably in the handle, which is operated with the aid of a lever link supported by an abutment in the handle.

BACKGROUND OF THE INVENTION

Pliers operated by lever links have become increasingly popular since they provide high clamping force and are lockable. The basic model consists of one jaw fixed to the handle and one jaw influenced by a lever link and being pivotably journalled in the handle. The jaw gap is usually set with the aid of a rear adjustment screw screwed into the handle and constituting an abutment for the lever part of the lever link. This adjustment is time- consuming and complicated since a testing procedure is often required before the desired clamping force is achieved. Another drawback is that both hands must be used during the adjustment procedure. Yet another drawback is that the jaws can only occasionally be made to assume a parallel position, which is desirable in order to be able to grip the workpiece without it turning.

Many attempts have been made to solve the problem of obtaining simple one-handed operation of lever-link operated pliers. Solutions proposed earlier are often based on replacing the rear adjustment screw in the handle by some type of mechanism that locks the rear limb of the lever link in the desired position by means of a wedge action, such as in US 2,499,210, US 2,531,285, US 2,661,648, US 2,751,801, US 3,104,571, US 4,275,623, for instance. Due to their complicated structure and the need for narrow manufacturing tolerances, these and similar pliers are difficult to % manufacture, easily subject to faults, and have not been used to any great

^Λ extent. As far as is known, the only exception is described in SE 194,750.

However, this tool is inconvenient to use since it must be held at the very outermost part during operation and its use has therefore not spread to any great extent.

A completely new type of solution for achieving rapid displacement of the jaw operated by the lever link to initial engagement with the workpiece is described in EP application 86, 420,238,7. The jaw is displaceable along a longitudinal groove in which, due to its non-circular form, the axis of pivot is clamped in the desired position when the lever link is tensioned. A serious drawback with these pliers is that they cannot be used to turn a workpiece since in that case the grip is released.

Yet another solution to the problem is described in SE application 90 023,66- 4. Here the rear adjustment screw has been provided with a thread having several inlets. The aim is to increase the pitch of the thread so that the screw need not be turned so many times in order to set the desired gap and clamping force. The improvement is only marginal since adjustment must always be performed when workpieces of different thicknesses are used and, as with the basic version, this requires the use of both hands.

The main reason for using lever-link operated pliers with one jaw displaceable along a straight bar is to increase the working area. The jaw can be locked in optional position on the bar by means of the "drawer effect".

Two types of this tool are known, differing from each other in the manner of adjusting the clamping force. The first type is provided with a rear abutment consisting of an adjusting screw for setting the clamping force as in US 4,850,254, for instance. This type of tool is used by moving the adjustable jaw along the bar to initial engagement with the workpiece and then opening the other jaw with the aid of the rear adjusting screw so that a suitable clamping force is obtained. This is necessary since the working angle of the lever-link joint is far too large to enable the final pressure to be exerted. Finally, the operating handle of the lever link is pressed to its lower locked position. This procedure is complicated, time-consuming and requires the use of both hands. Another drawback is that it is only occasionally possible to get the jaws to assume a parallel position. The best known tool of the other type is manufactured by Bessey. This type of tool is provided with an adjusting screw on the operating handle of the lever link for adjustment of the working angle of the lever link and thus also pre-setting of the desired clamping force. The adjustable jaw is moved along the bar to initial engagement with the workpiece, and the operating handle of the lever link is then pressed to its lower locked position without the need for any adjustment of the position of the other jaw. However, this tool also has the drawback that both hands must be used to adjust the jaw movable along the bar. Another drawback is that the angle of rest of the pivotable jaw alters upon adjustment of the clamping force. The parallelity must therefore always be adjusted when setting the clamping force, this being effected with a rear abutment for the lever link, consisting of an adjusting screw. Yet another drawback is that the tool becomes more complicated since two adjusting screws are necessary.

EP A2 0 058 349 describes a variant of the above-mentioned Bessey pliers, designed for performing various types of machining on the workpiece. The jaws are thus provided with machining elements such as knives. To enable step-wise cutting of thick workpieces the jaw displaceable along the bar is provided with a spring element drawing the jaw towards the workpiece. Said jaw comprises a rearwardly directed protuberance with the aid of which the jaw can be moved along the bar. However, this protuberance cannot be operated with the hand that is holding the tool and both hands must therefore be used for adjusting the movable jaw in this case also.

SUMMARY OF THE INVENTION

The primary object of the present invention is to obtain a means for hand tools utilising a pair of jaws to receive a workpiece, enabling the jaw gap to be rapidly and easily set in optional position with the hand that is holding the tool.

Another object of the present invention is to obtain a simple arrangement permitting the set clamping force to be maintained irrespective of the thickness of the workpiece, so that no adjustment need be performed for different thicknesses of workpiece. An additional object is to obtain a means permitting the set jaw angle to be maintained irrespective of the thickness of the workpiece and the clamping force set, so that parallel jaws can be obtained without previous adjustment.

These objectives are achieved with a means that utilises a pair of jaws to receive a workpiece between them, said means comprising a handle and a bar fixed to the handle, on which bar one jaw can be displaced and locked in optional position by means of the "drawer effect" and one jaw journalled pivotably in the handle which is operated with the aid of a lever link supported by an abutment in the handle, said means comprising a member to effect movement, provided with a lever that can be operated with the same hand as is holding the tool, in order to move the jaw displaceable along the bar.

Although the invention is described in the following primarily with reference to pliers operated by a lever link and having a clamping function, it is understood that the invention also relates to all other types of tools operated by a lever link and provided with a bar on which a jaw can be displaced and locked in optional position by means of the "drawer effect", such as pliers with various jaw embodiments for machining the workpiece. The invention also relates to all versions of lever links, such as lever links comprising varying numbers of levers and various types of opening means.

The invention will be described more fully in the following with reference to the accompanying drawings, which are thus intended to explain and not restrict the invention, in which:

Figure 1 is a side view, partly in section, of pliers operated by lever link with a member to effect movement for displacement of the jaw movable along the bar, and with a stop member for the pivotably movable jaw.

Figure 2 illustrates a horizontal section of the pliers according to Figure 1, showing the bar and the jaw displaceable thereon, as well as the member effecting its movement. Figure 3 is a side view of the pliers according to Figure 1, in locked position.

Figures 4, 5, 6, 7 and 8 are partial views of the tool with various embodiments of the member to effect movement for displacement of the jaw along the bar.

Figure 9 is a partial view of a tool with a curved bar and a member to effect movement for displacement of the jaw along the bar.

Figure 10 is a partial view of pliers operated by a lever link, with an alternative setting mechanism for the clamping force and a member to effect movement for displacement of the jaw along the bar.

Figure 11 is a partial view of pliers operated by a lever link, with a fixed abutment for the rear part of the lever link and with a member to effect movement for displacement of the jaw along the bar.

Figure 12 is a view, partially in section, of pliers with an adjustable stop member for the pivotably movable jaw and with a member to effect movement for displacement of the jaw along the bar.

Figure 13 is a partial view of pliers operated by a lever link, with a stop member for the pivotably movable jaw and with a member to effect movement for displacement of the jaw along the bar, and also with a counter member.

Figures 14, 15, and 16 are side views of different examples of pliers operated by a lever link, that utilise the invention.

The means according to Figure 1 is a preferred embodiment of the invention comprising a handle 1 in the shape of a U-section. A bar 2 is fixed to the handle. The bar may be made in one piece with the handle or may constitute a separate part which is bolted, welded or permanently fixed to the handle in some other way. A jaw 3 is provided with a channel into which the bar 2 is inserted. The jaw is displaceable along the bar and lockable in optional position. Locking is achieved by means of the "drawer effect" when the jaw is subjected to a turning action upon contact with the workpiece, so that the jaw is wedged by friction between its clamping surfaces 31, 32 and the bar. Downward movement of the jaw 3 is restricted by a pin 16 protruding from the rod 2. A second jaw 4 is pivotably journalled in the forward flanges of the handle 1 at a joint 5. The jaw 4 is influenced via the joint 8 of a lever link consisting of the operating handle 6 and lever 7 which are connected by the joint 9. The operating handle 6 is in the form of a U- section and an opening member 10 is journalled at the joint 11 in the rear part of the U-section's flanges. The rear end of the lever 7 rests against an abutment 12 in the form of an adjusting screw screwed into the rear of the handle 1, by means of which the clamping force is set. A compression spring 13 prevents unintentional turning of the abutment 12. A tension spring 14 is attached by one end to the rear portion of the handle 1 and by its other end to a hole 41 in the jaw 4. The spring 14 thus turns the jaw 4 towards a stop member 15 applied in the handle 1. This stop member may be a pin or a flap bent in from the handle 1. The stop member may also consist of a part on the jaw 4 projecting rearwardly or downwardly and resting against the handle 1 in its stop position. Furthermore, the stop member may be fixed in the rod 2 or other part that, together with the stop member, restricts turning of the jaw 4 in relation to the handle 1. This stop member 15 determines the angle of rest of the jaw 4 and enables parallelity between the clamping surfaces of the jaws 3 and 4, irrespective of the thickness of the workpiece 17. Thanks to the stop member 15 the angle of rest of the jaw 4 remains unaffected during pre-adjustment of the clamping force with the abutment 12, as can be seen from the following: Turning the abutment 12 in the direction of the arrow I will result in the rear part of the lever 7 moving backwards and the operating handle 6 being moved due to the action of the joint 9, from its upper position, indicated in broken lines, in the direction of the arrow II. The working angle of the lever link thus decreases and the value of the pre-set clamping force will be lower. The stop member 15 prevents the joint 8 from being pulled back during this procedure, and therefore the angle of rest of the jaw 4 is not affected. If the abutment 12 is turned in the other direction, the rear end of the lever 7 is moved forward and the operating handle 6 is moved up due to the action of the joint 9. The working angle of the lever link thus increases and the value of the pre-set clamping force becomes higher. The tension spring 14 prevents the joint 8 from being pushed forward during this procedure and the angle of rest of the jaw 4 thus remains unaffected.

The pliers are provided with a member to effect movement for operation of the jaw 3, this member comprising a lever 18 and a wheel 19 journalled in the lever 18 on a shaft 20. The lever 18 is preferably in the form of a U- section, the bottom of which has been removed at the front end and the rear part being provided with depressions for the fingers. The lever 18 is pivotably journalled in the jaw 3 via the forward part of its flanges, preferably on a level with the centre line of the bar 2, with the aid of pivots 23. The lever 18 is also provided with a pin 21 for the receipt of a tension spring 22, said spring running through a recess in the bottom of the handle 1 and fixed at its other end in the hole 41 of the jaw 4. When the lever 18 is pressed against the handle 1, the lever 18 swings around the shaft 20, whereupon the forward part of the lever 18 is moved away from the handle. The lever 18 thus provides leverage to move the jaw 3 out from the handle, thereby opening the pliers to receive a workpiece. This movement of the jaw occurs without any tendency to wedging since the displacement occurs almost or entirely without torque via the pivots 23 on a level with the centre line of the bar 2. When the jaw has been moved from the handle, out from its position of rest indicated by broken lines in the drawing, the shaft 20 is moved closer to the bar 2. This is possible since the wheel 19 is journalled on the shaft 20. The wheel 19 thus rolls along the lower side of the handle 1. In its lowermost position the jaw 3 is stopped by the pin 16, the latter preferably being located behind the centre line of the bar 2. This location in relation to the pivots 23 allows the jaw 3 to turn to its maximal opening dimension in the end position. When the lever 18 is released its forward part is moved in towards the handle due to the influence of the spring 22 and the jaw 3 is thus also moved towards the handle without any tendency to wedging, as will be understood from the above paragraph. The spring 22 thus has the double function of moving the jaw 3 in towards the handle 1, and also of pressing the lever 18 towards the handle 1. Figure 3 shows the pliers according to Figure 1 with a workpiece 17 clamped between the jaws. The workpiece 17 is inserted between the jaws once the jaw 3 has been opened by pressing the lever 18 towards the handle 1. The lever 18 is then released and the spring 22 draws the jaw 3 towards the workpiece. The jaw 3 is thus influenced by a turning torque that wedges it against the bar 2 in desired initial engagement with the workpiece. Finally, the operating handle 6 is pressed against the handle 1 in the direction of the arrow III, the workpiece thus being locked with considerable force by the lever-link action. The lever link is opened in known manner by pressing the opening member 10 against the handle 1. The jaws are then opened by pressing the lever 18 against the handle and the workpiece can be removed.

The tool is operated by one hand. Since the lever 18 is located in the forward end of the tool, near its centre of gravity and, upon operation, is pressed towards the handle, it can be controlled with the first and long fingers of the hand that is holding the tool. The tool is well balanced and can be conveniently handled in any position. A workpiece is gripped and locked extremely quickly. Other important advantages of the invention are that predetermined clamping force and parallel jaws are maintained regardless of the thickness of the workpiece.

Figures 4, 5, 6, 7 and 8 show different embodiments of members to effect movement for displacement of the movable jaw along the bar. All these embodiments have in common that they comprise a lever 18 which, when operated, is pressed towards the handle 1 in the direction of the arrow V. The lever 18 thus provides leverage to move the jaw 3 along the bar 2 in the direction of the arrow VI. As before, the lever 18 is in the form of a U- section with both flanges facing the handle 1, and is influenced by a tension spring 22 that endeavours to move the lever 18, and thus also the jaw 3, in towards the handle. The members to effect movement are also characterised in that they comprise an element that is pivotably journalled in the jaw 3 on a level with the centre line of the bar 2. Figure 4 shows an embodiment in which both flanges of the lever 18 are pivotably journalled in the handle 1 by means of a through-running shaft 20. At the forward end of the flanges the lever 18 is provided with two facing pivots 23, pivotable and displaceable in slits 25 in the jaw 3. When the lever 18 is pressed towards the handle 1 in the direction of the arrow V, the pivots 23 are pushed out from the handle 1 whereupon the jaw 3 is displaced along the bar 2 in the direction of the arrow VI. The pivots 23 thus slide along the slits 25. Alternatively the shaft 20 may be journalled on an arm protruding downwardly from the handle 1, thereby enabling a larger working area.

Figure 5 shows an embodiment in which the lever 18 is pivotably journalled in the handle 1 by means of a through-running shaft 20. The lever 18 is provided in both flanges with through-slits 26. The jaw 3 is provided with outwardly directed pivots that are pivotably and displaceably journalled in the slits 26. When the lever 18 is pressed towards the handle 1 in the direction of the arrow V, the slits 26 are moved out from the handle 1, whereupon the jaw 3 is displaced along the bar 2 in the direction of the arrow VI. The pivots 23 then slide along the slits 26.

Figure 6 shows an embodiment in which both flanges of the lever 18 are pivotably and displaceably journalled in a slit 27 in the handle 1 with a through-running shaft 20. The jaw 3 is provided with outwardly directed pivots (23) pivotably journalled in the forward part of the lever 18. When the lever 18 is pressed towards the handle 1 in the direction of the arrow V, the pivots 23 are moved out from the handle 1, whereupon the jaw 3 is displaced along the bar 2 in the direction of the arrow VI. The shaft 20 thus slides along the slit 27. Naturally the shaft 20 may slide directly along the lower side of the handle, but in that case the shaft 20 is preferably replaced by a convex sliding path with large radius towards the handle, suitably made out of some low-friction material.

The embodiments described in Figures 4, 5 and 6 require low friction between the slits and the pivots 23 and shaft 20, respectively. These may possibly be provided with wheels running in the slits. Figure 7 shows an embodiment in which the lever 18 is journalled via both flanges in the levers 28 with the shaft 20. At its other end the lever 18, as previously, is journalled in the jaw 3 with pivots 23. The levers 28 are journalled at their upper ends in the handle 1 by means of the shaft 29. If the shafts 20, 29 and pivots 23 are suitably located, the jaw 3 will be displaced along the bar 2 in the direction of the arrow VI when the lever 18 is pressed towards the handle 1 in the direction of the arrow V.

Figure 8 shows an embodiment in which the lever 18 is pivotably journalled in the handle 1 by means of a through-running shaft 20. The upper ends of the pressure bars 36 are pivotably journalled by means of pivots 37 in the forward flanges of the lever 18. At their lower ends the bars 36 are pivotably journalled in the jaw 3 with pivots 23. When the lever 18 is pressed towards the handle 1 in the direction of the arrow V the pivots 37 describe a circular movement. The distance between the pivots and the centre line of the bar 2 will then vary. This variation is taken up by the pressure bars 36 which are then turned at the same time as they move the jaw 3 in the direction of the arrow VI.

A number of different arrangements for displacement of the jaw 3 along the bar 2 with the aid of a lever 18 that can be operated with the same hand as that holding the tool have been described above. However, other embodiments obvious to one skilled in the art in the form of arrangements with cables, wires, tapes, pressure rods, drawbars and levers, deflection pulleys or toothed wheels, or racks, are feasible and are deemed to lie within the scope of the invention as defined in the following claims.

The member to effect movement preferably comprises a spring, this spring acting in the direction of the other jaw. However, a member to effect movement is possible that has no spring, or that has a spring acting in a direction away from the other jaw. In the latter case the movable jaw is moved by the operator along the bar to initial engagement with a workpiece via a lever or a handle. If the operating handle of the lever link functions as a counter support, the spring of the lever link must be much stronger than the spring of the member to effect movement, so that the lever link is not tensioned until the adjustable jaw is in initial engagement, without clearance, with the workpiece.

Figure 9 shows an embodiment in which the jaw 3 is operated as previously in accordance with Figure 1 but along a curved bar 2, suitably curved backwards from the jaws. The backward curvature of the bar causes the jaw 3 to be turned at the same time as it is displaced downwardly along the bar. This entails a considerable increase in the working area of the tool without the operating distance of the lever 18 being increased. The tool can thus be operated as conveniently as before but with a larger working area. The drawback is that the jaws are no longer parallel.

Figure 10 shows an embodiment of lever-link operated pliers in which the jaw displaceable along the bar is displaceable as before with the aid of some form of member effecting movement, but without stop members to the pivotably movable jaw. According to this embodiment the clamping force is set by means of an adjusting screw 24 on the operating handle 6 allowing adjustment of the working angle of the lever link. When the adjusting screw 24 is turned in the direction of the arrow I the forward extension of the lever 7 is pressed down and the operating handle 6 is thus moved from its upper position, indicated by broken lines, in the direction of the arrow II. The pre-set value of the clamping force thus decreases. However, this adjustment affects the angle of rest of the jaw 4. If the jaws are to be parallel, therefore, the angle of rest of the jaw 4 must be adjusted each time the clamping force is altered. This is achieved in that the abutment 12 consists of an adjusting screw, with the aid of which the entire lever link can be moved forwards or backwards in relation to the handle. The angle of rest of the jaw 4 is then influenced by the joint 8 and can be adjusted. Both the adjusting screws 12 and 24 are provided with compression springs 13 and 30, respectively, in order to prevent unintentional turning.

If parallel jaws are not absolutely necessary, the tool according to Figure 10 can be simplified. This can be done in accordance with Figure 11 by replacing the adjusting screw 12 by a fixed abutment in the handle 1, in the form of a shaft 38 on which the limb 7 of the lever link is pivotably journalled.

Figure 12 shows an embodiment in which the jaw 3 is operated as previously in accordance with the embodiment in Figure 1 but in which the angle of rest of the jaw 4 is adjustable. This may be desirable in order to reduce tolerance requirements during manufacture and to enable compensation of the change in angle occurring upon wear of the clamping surfaces on the jaws 3 and 4 and the bar 2. In this embodiment the jaw 4 is extended rearwardly and an adjusting screw 33 is screwed into its extension where it constitutes the stop member which encounters the handle and thus determines the angle of rest of the jaw 4. A compression spring 34 prevents unintentional turning of the adjusting screw 33. This arrangement allows the angle of rest, and thus also the parallelity of the jaws, to be adjusted with accuracy.

Figure 13 shows an embodiment in which the jaw 3 is operated as before in accordance with Figure 1 but in which the jaw 4 is provided with a rearward protuberance 35. This extension is designed as a counter surface when the lever 18 is pressed towards the handle 1. This may be a advantage if the spring 14 is relatively so weak that the lever link tends to be tensioned when the lever 18 is operated with the operating handle 6 as counter surface. This may occur when handling heavy tools. The embodiment described here prevents this since the extension 35 offers support for the hand when the lever 18 is operated with an operating force X. The extension 35 is thus affected by a downwardly directed counter force X. The jaw 4 is thus pressed towards the stop member 15, which is desirable. The lever link, on the other hand, remains unaffected. Of course it is also possible to achieve a similar function using a portion extending upwardly from the handle 1.

Figures 14, 15 and 16 show different modifications of the lever-link operated pliers utilising the invention. In these embodiments the spring 22 is so strong that it is able to pull the jaw 4 towards the stop member concealed in the handle 1. In this case spring 14 may be omitted. Figure 14 shows gripping pliers with parallel jaws. Figure 15 shows gripping pliers with a curved bar, thereby offering a large working area. Figure 16 shows a C-clamp with curved bar. Since the centre of gravity of the jaw 3 is in this case far away from the bar 2 there is a risk of tendencies to wedging when the jaw 3 faces down. This is avoided by a torsional spring 39 to press the jaw 3 towards the jaw 4. The torsional spring is turned around the pivots 23 and its arms rest against the jaw 3 and the lever 18.

Claims

1. A hand tool that utilises a pair of jaws (3 and 4) to receive a workpiece (17) between them, said means comprising a handle (1) and a bar (2) fixed to the handle, on which bar (2) one jaw (3) can be displaced and locked in optional position by means of the "drawer effect" and one jaw (4) journalled pivotably in the handle (1) which is operated with the aid of a lever link (6, 7) supported by an abutment (12, 38) in the handle (1), characterised in that the jaw (3) displaceable on the bar co¬ operates with a means to effect movement, said means comprising a lever (18) that can be operated with the same hand as is holding the tool.

2. A hand tool as claimed in claim 1, characterised in that the means to effect movement comprises an element (18; 36) that is pivotably journalled in the jaw (3).

3. A hand tool as claimed in claim 2, characterised in that the element (18; 36) that is pivotably journalled in the jaw (3) is connected to the jaw (3) between the clamping surfaces (31) and (32) of the bar (2), preferably on a level with the centre line of the bar (2).

4. A hand tool as claimed in claim 1, 2 or 3, characterised in that the lever (18) is journalled in a wheel (19) able to roll on an edge at an angle to the bar (2).

5. A hand tool as claimed in claim 1, 2, 3 or 4, characterised in that the bar (2) is curved.

6. A hand tool as claimed in claim 1, 2, 3, 4 or 5, characterised in th t the pivotably journalled jaw (4) co-operates with a stop member (15; 33) restricting movement in the direction of the clamping action. A hand tool as claimed in claim 6, characterised in that the stop member (33) restricting movement is adjustable so that the angle of rest of said other jaw (4) can be set at a desired constant position.

A hand tool as claimed in claim 1, 2, 3, 4, 5, 6 or 7, characterised in that the pivotably journalled jaw (4) is provided with a rearwardly directed protuberance (35).

A hand tool as claimed in claim 1, 2, 3, 4, 5, 6, 7 or 8, characterised in that the bar (2) is provided with a pin (16) located behind the centre line of the bar.