GB2160140A - Cutting tool - Google Patents

Abstract

A pair of shears comprise pivotally connected blade members 12', 14' having extended offset cutting surfaces 70', 72' with respect to pivot bosses to permit the cutting of irregular shapes. The pivot bosses and the cutting surfaces are adapted for removal of material therefrom to permit resharpening of the offset shears while maintaining the effect of the cutting surfaces 70', 72'. The shanks of the blade members 12', 14' are also provided with wire cutting means 88', 90', preferably a pinch cutter capable of to being a stop for limiting rotation of the first and second blade members 12', 14'. Also provided is an improved handle configuration with toggle means providing greater cutting power. <IMAGE>

Description

SPECIFICATION Cutting tool The present invention relates to improved hand operated offset shears which can be used for cutting sheet metal or similar material in either a straight line or in a right or left hand direction, including circle cuts down to an opposing circle of about 5 to 7 cm in diameter.

When sheet metal or similar material is cut with conventional shears, one or both edges of the cut sheet material may interfere with the body of the shears, making it difficult to advance the shears into the sheet material and distorting the cut edges. This interference is greatest when cutting irregular shapes, particularly sharp curves and especially small circles. Accordingly, conventional shears are often supplied in mirror image configurations particularly adapted for either left-hand or right-hand turning cuts. Also, when conventional shears are used to cut thick, tough or stiff material, the sheet material may tend to slide away from the blades as they are closed, decreasing the efficiency of the cutting. Further, conventional shears may require long handles and substantial force to be exerted by the operator in order to cut many sheet materials.

As shown in U.S. Patent Specification No.

2,264,840, one approach to decreasing the interference of the cut sheet material with the body of the shears is to offset the cutting surfaces with respect to the shank portions of the shears such that the cut sheet material passes to one side of the shank portions. Also mentioned therein is the practice of extending the cutting blades laterally approximately at right angles to the place of operation of the shanks. This configuration facilitates advancement of the shears into the sheet material by reducing the extent to which the cut sheet material must be spread vertically to pass above and below the lower blades, thereby decreasing the tendency of the sheet material to slide away from the cutting surfaces. More recently, a link arrangement as shown in U.S. Patent No. 3,587,183, has been proposed to reduce the force required by the operator to cut heavy sheet materials.

As with conventional shears, most available offset shears can be used only in cutting curves either in the left-hand or right-hand direction, thus requiring other offset shears having a mirror image configuration when curves must be made in the other direction. Also, the laterally extending blades of available offset shears must be carefully ground and aligned during manufacture and, generally cannot be conveniently reground if they become dull or damaged. Abuse of the blades by cutting wire or similar materials may render the shears useless for cutting sheet material. Accordingly, a need exists for improved offset shears which can be easily resharpened if the blades become dull or damaged, and which embodies a pinch or shear type wire cutter.Further, there is a need for an improved handle and toggle arrangement or configuration making the offset shears more powerful and convenient to use when cutting heaving sheet material.

In applicant's earlier U.S. Patent application No.

386049, a pinch type cutter is employed where part of the upper blade member serves as an anvil and a portion of the lower blade member serves as a chisel for the wire cutter. With such an arrangement a "relief" formed at the base of the cutter elements, due to the manufacturing processes involved, requires wire that is to be cut to be specifically positioned substantially centrally in the cutter.

Should, for example, a small diameter wire be positioned at the base of the cutter, the "relief" in effect precludes the wire from being cut by the chisel and anvil. This "relief" is created as a result of the various grinding operations or passes required in order to grind the opposite faces of the chisel.

Also, in the formation of the chisel of this cutter the grinding passes generally create a broad Vshaped chisel having an angle between the sides thereof of about 70 degrees. such an angular chisel configuration, although adequate for most applications, requires more difficult manufacturing processes to fabricate resulting in considerably higher product cost. It also requires higher pressures and forces to cut wire as the chisel has a broader cutting angle and wire of smaller and even larger gauges can easily become snagged or trapped at the base of the cutter in the "relief" area. Such an occurence then makes it difficult to cut the wire and one must manually reposition the wire centrally so that the chisel cuts or pinches across the full width of the wire trapped squarely between the anvil and the full face width of the chisel.

Another disadvantage of applicant's earlier proposal is the fact that the lower blade member, although offset, does not provide adequate clearance so that very small opposing diameter circle cuts cannot be made. This deficiency makes it necessary to fabricate and stock both left and right hand cutters as neither offset shears is considered truly universal type of shears capable of cutting in any direction, that is, straight, right-hand and left-hand.

It should be recognized that for most applications, cutting arcs, curves, or circles down to at least about 5 to 7 cm in diameter would satisfy most field requirements of the tool.

It is therefore an object of the present invention to provide universal offset shears which can cut sheet material in both left-hand and right-hand curves, as well as in very small diameter circles, without being impeded by interference of the cut material with the body of the shears.

It is a furtherobject of the present invention to provide universal offset shears of increased power and in which the cutting surfaces may be conveniently and economically resharpened if the cutting surfaces become dull or damaged, and resharpening of the chisel of the wire cutter can be done by a single grinding pass with the boss of its blade member.

It is a further object of the present invention to provide universal offset shears having either pinch or shearing means for cutting wire and the like, thereby eliminating the need for a second tool and reducing the abuse of the sheet material cutting surfaces of the offset blade members.

It is a further object of the present invention to provide universal offset shears having substantially increased power due to a toggle arrangement which provides greater force action to the central toggle pivot of a dual linkíthree pivot toggle linkage because of the general linearity of the toggle pivot points when the offset shears is in closed position.

It is still a further object of the present invention to provide universal offset shears having handles with a toggle linking arrangement of considerably greater power which can more easily be grapsed when the shears are in the open position and more easily forced to the closed position.

It is yet another object of the present invention to provide universal offset shears having either a pinch or shear type cutter, with the anvil portion of the pinch cutter on the upper blade member and the chisel on the lower blade member regardless of the type of cutter which is employed.

It is yet another object of the present invention to provide universal offset shears having a chisel which can be sharpened in a single grinding pass with the boss of its blade member, and which cuts across the full width of the anvil.

The present invention is directed to improvement in hand operated all-way shears or snips with full width wire cutting means for cutting sheet material and wire or other rod-like materials.

According to an aspect of this invention, first and second blade members have pivot bosses through which a pivot means pivotably connects the blade members for rotation about an axis perpendicular to the pivot bosses. The respective blade members have first and second cutting surfaces which are offset with respect to the plane of the respective pivot bosses. Upon rotation of the blade members about the pivot means, the first and second cutting surfaces are moveable between an open position and a closed position for cutting sheet material therebetween. The pivot bosses and the cutting surfaces are adapted for removal of material therefrom so as to provide resharpened cutting surfaces while maintaining the offsets between the respective pivot bosses and the cutting surfaces.At the same time of resharpening the chisel of the wire cutter, a pivot boss is also ground down to the desired size. The offsets of the cutting surfaces with respect to the pivot bosses is a minimum of about .250' to .375' so as to permit previously cut mate rial to pass the blade members without interference and to permit the cutting of very small diameter opposing circle cuts.

According to another aspect of this invention, first and second blade members are pivotably connected through shank portions, one of the shank portions being provided with a recess substantially in the plane of the sheet material to be cut. The respective blade members have first and second cutting surfaces which are provided with extended offsets with respect to the shank portions and which are movable upon rotation between an open position and a closed position for cutting the sheet material therebetween. A cut edge of the cut sheet material is receivable in the recess so as to permit cutting of the sheet material along both left-hand and right-hand curves. As a result, the offset snips of the present invention are "universal", truly eliminating the need for separate right-hand and lefthand snips when irregular cuts are required.

According to another aspect of this invention, the handles are pivotable to provide particularly favorable toggle leverage throughout the cutting stroke, whereby the center toggle point about which the forces are generated to achieve powerful locking of the tool is accomplished by positioning same substanially in line just about shy of the "over center" toggle position with the pivot bolts providing the articulated movement of the blade members with respect to the handles. Other aspects of the invention include an improved integral cutting means suitable for cutting wire and an integral locking means for maintaining the cutting blades in the closed position.The invention will be described further, with reference the accompanying drawings, in which; Figure 7 is a side elevational view of a preferred embodiment of the offset shears of the present invention shown in the open position and with portions broken away; Figure 2 is a side elevational view of the offset shears of Figure 1 shown locked in the closed or cutting position and with portions borken away; Figure 3 is a sectional view of the offset shears of Figures 1 and 2 taken alon the line 3-3 of Figure 2; Figure 4 is a side elevational view of the upper cutting blade of the offset shears of Figures 1 to 3; Figure 5 is a sectional view of the upper cutting blade of the offset shears of Figures 1 to 3 taken along the line 5-5 of Figure 4; Figure 6 is a sectional view of the upper cutting blade of the offset shears of Figures 1 to 3 taken along the line 6-6 of Figure 4;; Figure 7 is a side elevational view of the lower cutting blade of the offset shears of Figures 1 to 3; Figure 8 is a sectional view of the lower cutting blade of the offset shears of Figures 1 to 3 taken along the line 8-8 of Figure 7; Figure 9 is a sectional view of the lower cutting blade of the offset shears of Figures 1 to 3 taken along the line 9-9 of Figure 7; and Figure 10a and lab are fragmentary top views of opposing shearing blades of typical shear type cutters which may, if desired, be employed in lieu of the pinch cutter.

A preferred embodiment of the universal offset shears or cutting tool of the invention having an improved wire cutter is indicated generally in the Figures by reference number 10'. The shears 10' include upper and lower blade members 12' and 14', respectively which are pivotably moveable about a main pivot bolt 16' by upper and lower handles, indicated generally by the numerals 18' and 20', respectively. Movement of the blade members 12' and 14' between the open position shown in Figure 1 and the closed position shown in Figure 2 effects cutting a sheet material work piece 22' or a wire workpiece 24' positioned between the blade member 12' and 14', as shown in Figure 1.

The handles 18' and 20' are pivotably moveable about a handle pivot bolt 26' located intermediately of the ends of the handles 18' and 20'. the rear-ward portions 28' and 30' of the respective handles 18' and 20' are covered with upper and lower hand grips 32' and 34', respectively. Preferably, the hand grips 32' and 34' are formed by dipping or molding so as to include outwardly projecting ear portions 36' and 38', respectively, to prevent the hand of the operator from sliding forward during use of the cutting tool 10'.

The handles 18' and 20' extend forward from the handle pivot bolt 26' and away from each other for pivotable mounting to the blade members 12' and 14' at pivot bolts 40' and 42', respectively. In the open position shown in Figure 1, an acute angle is, preferably, formed between an imaginary line joining the pivot bolts 26' and 40' and an imaginary line joining the pivot bolts 26' and 42'. Such an acute angle is in the order of about 70 degrees.

However, in the closed position, the angle between the two imaginery lines is preferably increased to about 115 to 120 degrees preferably 117 degrees resulting in a substantially more powerful grip due to the shallower toggle "linkage" and the general linearality of the toggle pivot points when the offset shears are in a closed position. With the pivot bolts 40' and 42' closer to the handle pivot bolt 26', the latter is much more closer to dead centre where power is maximum for the toggle rnechanism. Thus, in this invention, the distance between the handle pivot bolt 26' and the pivot bolts 40' and 42' is about 1/4 inch (0.62 cm) less than in the earlier proposal which results in improved offset shears of considerably greater power.In the closed position, the two opposite equal angles of the triangular "over-centre" type toggle mechanism form angles with the further imaginary line joining pivot bolts 40' and 42' of the order of about 30 degrees to about 33 degrees. Preferably, the handles 18' and 20' have a U-shaped cross-section, as shown in Figure 3, formed by laterally spaced side portions 44' and 46' joined by a web portion 48'. An omega spring 50', held in place by the handle pivot bolt 26', engages the web portion 48' of the handles 18' and 20' to bias the cutting shears 10' into the open position. Other biasing means could also be employed with this embodiment of the invention. Although not essential to the operation of the cutting shears 10', a centering sleeve 51' is provided to substantially extend the cylce life of the omega spring 50'.

In the open position, the upper blade member 12' extends upward and rearward from the main pivot bolt 16' to a pivotable mounting upon the pivot bolt 40' as shown in Figure 1. The lower blade member 14' extends rearward from the main pivot bolt 16' to a pivotable mounting upon the pivot bolt 42'. In response to the closing of the handles 18' and 20', the pivot bolts 40' and 42' are rotated about the handle pivot bolt 26', thereby spreading the rearward portions 54' and 56' of the blade members 12' and 14'. As illustrated in Figure 3, the rear-ward portions 54' and 56' have sufficient thickness to be closely received by the side portion 44' and 46' of the handles 18' and 20' so as to maintain alignment of the upper and lower cutting blades 12' and 14'.Adjustment of the play between the side portions 44' and 46' and the rearward portions 54' and 56' is provided by adjustment nuts 58' upon the pivot bolts 40' and 42'.

The main pivot bolt 16' is threaded into a hole 60' in the shank portion 62' of the upper blade member 12' and forms a sliding fit with a hole 64' within the shank portion 66' of the lower blade member 14'. A lock nut 68 is locked against the shank portion 62' to maintain the adjusted length of the main pivot bolt 16. Cutting surfaces 70' and 72' of the cutting blades 12' and 14', respectively, are within a plane substantially parallel to but offset laterally from the adjoining shank portions 62' and 66' of the respective blade members, as shown in Figure 4. It will be noted that the offset is extended sufficiently to easily permit a cut portion of the sheet material workpiece 22' to pass to the side of the shank portion 66', but more importantly, to enable the improved tool to cut down to an opposing circle of about 2.0' to 2,5' (5 to 7 cm) in diameter.This arrangement permits one to cut sheet metal for most jobs with a single tool as the "super" extended offset blades enable not only straight line cuts, but also sharp curves in either left or right hand directions.

The cutting surfaces 70' and 72' are also similarly curved in side elevation with like radii, as shown in Figure 4 and 7, so as to prevent convex cutting surfaces to the workpiece. Also, the forward portions 84' and 86' of the respective blade members 12' and 14' extend laterally nearly perpendicular to the shank portions 62' and 66'.

Preferably, the blade members 12' and 14' are hollow ground along the surfaces 78' and 80', respectively, to ensure that the upper and lower cutting surfaces 70' and 72' have a uniform width in side elevation while providing for resharpening of the blade members, as described below. The rearward portion of the lower cutting surface 72' is provided with a relief 82' to facilitate grinding of the cutting surface 72' and to ensure smooth sliding engagement of the cutting surfaces 70' and 72' during cutting. The forward portions 84' and 86' are curved inward as shown in Figures 6 and 9 to form convex surfaces. This configuration of the forward portions 84' and 86' provides sufficient strength for the cutting surfaces 70' and 72' while permitting the cutting shears 10' to be manoeuvered for cutting when space is limited.

Cutting of the wire workpiece 24' is provided by engagement of an anvil portion 88' formed upon the lower blade member 14' by a chisel or wedge portion 90' formed upon the upper blade member 12'. The placement of the anvil portion 88' and the wedge portion 90' is such that their engagement provides a stop to limit rotation of the blade members when the cutting shears 10' are in the closed position shown in Figure 2. The wedge portion 90' serves as a chisel to sever a wire, rod, small bar or the like placed upon the anvil portion 88' when the cutting shears 10' are moved from the open position shown in Figure 1 to the closed position in Figure 2. It will be appreciated that the opposed cutting surfaces cut wire by means of pinch cutting which is preferable to other cutting means, such as shear cutting, as a separate limit stop is not required.With shear cutting surfaces in the form of "scissor-like" cutting blades between portions of the opposite blade members, the shears would also require a pair of mating abutments 89 and 91 (limit stop) betwen the handle blades for limiting rotation of the blade members (as best shown in phantom in Figures 1 and 2). Such a limit stop is necessary in each of the embodiments of Figures 10a and 10b where shear type wire cutters are substituted for pinch type wire cutters. With a shear type cutter of Figure 10a employed, the anvil portion 88' is simply ground down to clear the cutting blade or chisel 90' and movement of the chisel 90' (shown in phantom) past the opposing shear edge 93' cuts the wire (also shown in phantom).In Figure 10b the opposing shear edge 93' is outwardly offset as the sharp cutting edge of the shear blade or chisel 90' is disposed at an angle opposite to that of the chisel 90' shown in Figure 10a.

With either a pinch cutter or the shears type cutter, no relief is required at the base of the cutter elements as the chisel or knife edges are all sharpened by grinding across the full face of the cutter elements. With the shears of the invention, only a single grinding pass need be made to form either type of cutter as the cutters are formed by grinding an angled or beveled edge from a straight edge.

Thus, such a knife edge or sheer blade formed thereby can be substantially smaller in angle size and therefore considerably more sharpe than a more conventional blunt V-shaped angled pinch cutter. For example, approximately a 70 degree angle is provided in the chisel of the previously known shears whereas in the preferred embodiment here an angle of a out 40 degrees to about 60 degrees is satisfactory. It is believed that considerably less friction is generated during cutting with the small angled cutter of the present invention as compared to the earlier pinch cutter. In such cases, the blade members are inherently made of stronger steels in order to maintain a sharp cutting edge or edges. Preferably, an angle of about 50 degrees has been found to be suitable for the practice of the invention.It should also be appreciated that with a blunt angle of 70 degrees for the previously known V-shaped pinch cutter, greater forces are required to pinch or cut wire as the wider wedge-shaped chisel is believed to generate considerably more frictional resistance to cutting.

It will be appreciated that with the full face width cutters of the present invention, very small wires can be easily cut as there is no "relief" at the base of any cutter. Thus, the small wire can be positioned anywhere along the cutting edge or anvil, be it the pinch or shears type, without any fear that the small wire will be hung-up in a "relief" at the base of the cutter or anvil and either not be cut or incompletely cut. With such situations, one must then accurately reposition the wire in the centre of the cutter in order to recut the wire in another spot, of finish the incomplete cut at the same spot, or to recut as close to the first attempt as one could conceivably achieve without the aid of any special tools to accurately align the cutter up for a "second" bite at the wire.

It is an important feature of the present invention that the cutting surfaces 70' and 72' may be reground to renew worn or damaged cutting surfaces. Referring to Figure 3, it will be apparent that grinding back either the upper cutting surface 70' or the lower cutting surface 72' would normally be expected to result in a lateral space between the cutting surfaces 70' and 72',, thereby precluding shearing of the sheet material workpiece 22'. The offset of the cutting surface 70' with respect to the shank portion 62' is decreased by such grinding, and the offset of the cutting surface 72' with respect to the shank portion 66' is increased by such grinding. For this reason as noted hereinbefore, commercially available offset shears cannot be conveniently resharpened once they become dull or damaged.

Resharpening of the cutting shears 10' of the present invention is facilitated by pivot bosses, indicated generally by the numerals 92' and 94', upon the adjacent surfaces of the shank portions 62' and 66', respectively. The pivot bosses 92' and 94' are flat projections above the surface of the shank portions 62' and 66' perpendicular to the main pivot bolt 16'.The pivot boss 92' in the illustrated embodiment is of particular configuration in that it includes a portion 96' generally concentric with the main pivot bolt 16' and a generally slender rectangular upward portion 97, as shown in Figure 4. Pivot boss 94' includes a generally circular portion 100' concentric with the main pivot bolt 16' and a generally upwardlly extending portion 101, as indicated in Figure 7.The pivot bosses 92' and 94' provide improved bearing surfaces between the blade members 12' and 14' while maintaining alignment of the cutting surfaces 70' and 72'. The upward portions 97 and 101 also respectively reinforce the strength of the anvil portion 88' as well as the chisel 90' itself.

In the cutting shears 10', the offset of the cutting surfaces bosses 70' and 72' is determined by the location of the pivot bosses 92' and 94'. As a result, resharpening of the cutting shears 10' can be provided by grinding both the cutting surfaces 70' and 72' and the respective pivot bosses 92' and 94' (and their upward portions 97 and 101 as well). It will be appreciated that no change in the offset of the upper cutting surface 70' will occur if equal thicknesses of material are ground from the upper cutting surface 70' and the pivot boss 92'. Similarly, no change in the offset of the lower cutting surface 72' will occur if equal thicknesses of material are ground from the lower cutting surfaces 72' and the pivot boss 94'. Thus, either or both of the blade members 12' and 14' may be resharpened as is periodically required during normal use without producing a lateral space between the cutting sur faces 70' and 72'.

Resharpening of the respective blade members is further simplified because no curved surfaces require regrinding. The upper and lower cutting surfaces 70' and 72' are ground in a plane which is substantially parallel to the respective pivot bosses 92' and 94'. The pivot bosses 92' and 94' may be machined first to provide reference surfaces for the grinding of the surfaces 70' and 72'. The hollow ground portions 78' and 80' of the respective blade members 12' and 14' eliminate the need to grind any other surfaces during resharpening. It has been found that sufficient regrinding capability is provided if the height of the pivot bosses 92' and 94' above the adjacent shank portions 62' and 66'is 1/32 of an inch (about 0.08 cm).The articulation of the blade members 12' and 14' with respect to the handles 18' and 20' permits the cutting surfaces 70' and 72' to be positioned in a grinding fixture with the pivot bolts 26', 40' and 42' in place, only the main pivot bolt 16' having been removed.

As noted hereinbefore, the cutting of the sheet material workpiece 22' is enhanced if the upper and lower cutting surfaces 70' and 72' are not exactly parallel with respect to the pivot bosses 92' and 94' but, instead, are angled slightly so as to establish progressive interference as the blade members are closed. Although various amounts of interference may be used with similar effect, applicant prefers an angle of approximately 15 minutes on each of the cutting surfaces 70' and 72' so as to established a total interference of approximately one-half a degree. This interference forces the blades tightly together during the latter part of the cutting stroke to ensure a shearing action; and the angle and offset desired is formed when the blade members 12' and 14' are initially ground or subsequently reground to effect resharpening.

Suitable locking means which can be engaged manually to prevent the cutting shears 10' from opening from the closed position is shown in Figure 2. The pivot bolt 40' is formed with a shoulder portion between the shank portion and the head portion. A lock strap 104' is pivotably mounted upon the pivot bolt 42' outside the laterally spaced side portions 44' and 46' of the upper and lower handles 18' and 20'. The free end of the lock strap 104' is notched in a side portion thereof so as to form a hook surface 106'. The lock strap 104' is moveable manually between the pivot bolt 40' and the handle pivot bolt 26' from a first position shown in Figure 1 which permits operation of the cutting shears 10' to a second position shown in Figure 2 which locks the cutting shears 10' in the closed position.In the second position, the hook surface 106' of the free end of the lock strap 104' is rotated into engagement with the shoulder portion of the pivot bolt 40' such that the lock strap 104' is held in compression by the omega spring 50'. The lock strap 104' may conveniently be released or engaged by the operator's thumb to permit onehand operation.

Although the cutting surfaces 70' and 72' of the blade members 12' and 14' are considerably offset from the pivot bosses so as to provide universal offset shears capable of cutting small opposing cir cles of the order of about a.0' to 2.5' (5 to 7 cm) diameters, a triangular notch or recess 110' may still be provided in the shank portion 66' of the lower blade member 14' in line with the path of the cut sheet material workpiece 22' passing above the forward portion 86' of the lower blade member 14'. The recess 110' aids in permitting the cutting shears 10' to cut right-hand as well as left-hand turning cuts.

It will be appreciated that the cutting shears shown can cut equally as well in a right-hand as a left-hand turning cut, e.g. in case where a small circle or sharp curve is experienced in the opposite direction from the tool's normal orientation. This eliminates for all intents and purposes the need for separate cutting shears particularly adapted for right-hand turning cuts.

Another feature of the cutting shears 10' is that the handles 18' and 20' are particularly convenient and adapted for applying force throughout the range of motion of the cutting blades 12' and 14'.

Unlike conventional offset shears, the handle pivot bolt 26' is disposed close to the hand grips 32' and 34', but at the same time it is about 1/4 inch (0.62cm) closer to the pivot bolts 40' and 42' as compared to the previously proposed shears. As a result, the angle formed between the hand grips 32' and 34' when the cutting shears 10' are in the open position shown in Figure 1 is greater than that of previously known shears. With the pivot bolts 40' and 42' disposed closer to the pivot bolt 26', the angle between "imaginery toggle links" between the pivot bolt 26' and each of said pivot bolts 40' and 42' is preferably in the order of about 115 degrees to about 120 degrees, and more preferably about 117 degrees with the shears in a closed position.With such construction, a more powerful shears is achieved inasmuch as the centre point of the three piece "toggle" linkage arrangement more closely approaches dead centre where the three pivot points would form a straight line (maximum power).

In the open position, the forward portions of the hand grips 32' and 34' are spaced apart to permit the handles 18' and 20' to be spanned by the operator's hand adjacent to ear portions 36' and 38' for maximum leverage. The lower hand 20' is configured such that the open position of the lower hand grip 34' does not interfere with a work-bench upon which the sheet material workpiece 22' is placed for cutting. As the upper and lower blade members 12' and 14' are moved toward the closed position shown in Figure 2, the more rearward portions of the upper and lower hand grips 32' and 34' are progressively, ideally spaced apart for maximum leverage.

Of course, it should be understood that various changes and modifications to the preferred embodiments described above will be apparent to those skilled in the art. For example, rivets or other pivot means may be employed in place of the four bolts without effecting the operation of the cutting shears. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting and that variations are possible within the scope of the claims.

Claims (9)

1. Universal offset shears for cutting wire and for cutting sheet metal or the like in substantially any direction comprising upper and lower blade members having, respectively, flat first and second pivot bosses and first and second cutting surfaces offset with respect to the plane of said first and second pivot bosses, and pivot means pivotably connecting the upper and lower blade members for rotation about an axis perpendicular to the first and second pivot bosses by opposite handle means pivoting the upper and lower blade members about the pivot means such that the first and second cutting surfaces are movable between an open position and a closed position for cutting sheet metal therebetween, characterised in that an upwardly extending portion of the first pivot boss forms a beveled chisel edge of a wire cutter and an upwardly extending portion on the lower blade member serving as an opposing wire cutter surface to the chisel edge, in that the opposing surface of said cutter covers or matches the full face width of the chisel edge so that pinching and snagging of the wire during cutting is precluded, in that both pivot bosses and the cutting surfaces are adapted for removal of materials therefrom for resharpening the cutting surfaces while maintaining the offsets therebetween with the first and second pivot bosses serving as reference surfaces to facilitate resharpening of the offset shears and in that the offset shears are capable of small opposing circle cuts down to at least 2.0' to 2.5' (5 to 7 cm) in diameter.

2. Universal offset shears as claimed in claim 1, wherein the upwardly extending portion of the first pivot boss is an anvil, and the wire cutter is a pinch-type cutter with the anvil and the chisel serving simultaneously as a stop to limit the travel of the first and second cutting surfaces of the upper and lower blade members.

3. Universal offset shears as claimed in claim 1, wherein the upwardly extending portion of the first pivot boss forms an opposing shear edge resembling the chisel which will shear past the opposing shear edge of the chisel, wherby the wire cutter is ahear-type cutter.

4. Universal offset shears as claimed in claim 3, including mating abutments on the opposite handle means for providing a stop to limit the travel of the first and second cutting surfaces of the upper and lower blade members.

5. Universal offset shears as claimed in any preceding claims, wherein the chisel is an angled knife-like edge of about 40 degrees to about 60 degrees.

6. Universal offset shears as claimed in any preceding claim, wherein the chisel has an angled knife-like edge of about 50 degrees.

7. Universal offset shears as claimed in any preceding claim, wherein the opposite handle means include a pivot joint therebetween and pivot connections with the upper and lower blade members, so that a three point toggle linkage is formed between the opposite handle means and the blade members and the pivot joint angle formed by the pivot joint and each of the pivot connections when the blade members are in a closed position is about 115 degrees to about 120 degrees, whereby greater power is achieved by the offset shears due to the pivot joint approaching dead centre between the pivot connections.

8. Universal offset shears as claimed in any preceding claim, wherein the pivot angle is about 117 degrees.

9. Universal offset shears for cutting wire and for cutting sheet metal or the like in substantially any direction substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 9, or in Figure 10a or in Figure 10b of the accompanying drawings.