BACKGROUND OF THE INVENTION Manually operated shears employing reciprocating jaw blades are commonly used to cut sheet materials. Such shears include Tinsman's snips which are manually actuated and can cut both clockwise and anticlockwise curves (hereinafter referred to as left handed and right handed curves). However, the shearing blades of Tinsman's snip are symmetrically pivoted together and have the disadvantage of trailing sheared sheet edges impeding operation of the snips and possibly resulting in cutting the hands of the user.

Another form of hand operated manually actuated shear, commonly known as aviation snips, have inclined handles and an offset shearing plane so that the operation of the shears is not impeded by trailing sheared sheet edges. A limitation of such snips is that a separate tool is required to cut right and left handed curves.

Manually actuated shears are not generally ideally suited for shearing long sheet lengths as they may cause arm or wrist strain especially when cutting thick steel sheeting.

Powered hand operated shears have been developed for both ease of use and to alleviate the problems associated with arm or wrist strain. One form of powered hand held shear uses a guillotine action between a fixed anvil and a moveable shearing blade. However, when shearing a curved line

the resulting sheared edges are usually jagged as there is no means of adjusting the stroke of shearing blades.

Another form of powered hand operated shear is known as a nibbler which consists of two spaced anvil sections and a pivotal shearing jaw located between the anvil sections. Such nibblers are disclosed in U.S. patent specifications: 4173069 and 2934822. The shearing action of a Nibbler results in the removal of a strip of sheeting having the thickness of the shearing jaw. This is not always acceptable as material is wasted and the shearing turning circle is limited by the thickness of the strip. Generally speaking, none of the above prior art hand held shears whether powered or hand operated are suited for cutting undulating corrugated sheet metal of the type typically used on roofing, fences and other structures. This is because of the co- action between relatively long straight shearing edges and a curved surface which gives rise to deformations in the resulting edges.

This problem may be minimised to some degree with manually actuated shears which permit the use of a short shearing stroke adjacent the free ends of the shearing jaws. However, this is inefficient and is generally impractical for powered shears in which the reciprocating shearing stroke is of a constant length.

Another problem with prior art hand operated shears is that their shearing action does not assist in drawing the sheeting towards the shearing edges. Accordingly, the user must move the shearing edges in the cutting direction which can lead to user fatigue, inaccuracies or errors in shearing. A further problem with prior art hand operated shears is that reciprocation of the jaw and anvil does not provide a continuous shearing action.

As a result, if a user of such shears loses concentration, or is unskilled in their use, unwanted cuts and distortions in the sheared edges can result.

SUMMARY OF THE INVENTION It is an aim of the invention to provide a shearing assembly for sheet material having restricted flexibility which overcomes or alleviates at least one of the problems associated with prior art.

According to one form of the invention there is provided a shearing assembly for shearing sheet material having restricted flexibility including: a body having rotatably mounted thereto about a primary axis a primary cutting member for operative coupling with a drive means, the primary cutting member having a cutting member shearing edge; an anvil means having an anvil shearing edge for co-acting with the primary cutting member shearing edge to provide a shearing action in a shearing plane; and an arm suspending said anvil member from said body member, wherein, the arm allows the assembly to shear both left handed and right handed curves in the sheet. The arm may be characterised whereby when the assembly is shearing the sheet and is positioned such that the shearing plane is vertical, one sheared edge of the sheet passes directly below a section of the arm and a corresponding other sheared edge of the sheet passes directly above a section of the arm.

Preferably, the arm has resilient properties.

Suitably, the arm may be integral with or attached to the anvil. Preferably, the primary cutting member is a primary shearing roller wherein the cutting member shearing edge is a continuous annular edge thereof.

Suitably, the anvil means includes an anvil shearing roller, wherein the anvil shearing edge is a continuous annular edge thereof, the anvil shearing roller being rotatable about an anvil axis. Suitably, the assembly is further characterised in that, when shearing the sheet, a circumferential surface of the primary shearing roller frictionally contacts the sheet thereby assisting in relative movement between the sheet and the assembly. Preferably, the assembly is further characterised in that, when shearing the sheet, a circumferential surface of the anvil shearing roller frictionally contacts the sheet thereby assisting in relative movement between the sheet and the assembly. There may be an primary gripping roller, rotatably associated with the primary shearing roller and rotatable about the primary axis, said primary gripping roller having a circumferential gripping surface positioned to provide a first sandwiching grip with the circumferential surface of the anvil shearing roller thereby gripping the sheet.

Preferably, the primary gripping roller has a smaller diameter than that of the primary shearing roller. Suitably, there may be an anvil gripping roller rotatably associated with the anvil mounting member and rotatable about the anvil axis, the anvil gripping roller having a circumferential gripping surface positioned to provide a second sandwiching grip with the circumferential surface of the primary shearing roller thereby gripping the sheet.

Preferably, the anvil gripping roller has a smaller diameter than that of the anvil shearing roller. The gripping means may be teeth, knurled contours, or a resilient surface.

Preferably, at least one of the surfaces

providing the first sandwiching grip taper along the axial length thereof.

Preferably, at least one of the surfaces providing the second sandwiching grip taper along the axial length thereof.

Suitably, adjacent radial surfaces of both the primary shearing roller and anvil shearing roller have an annular recess adjacent the shearing edges thereof. Preferably, the primary roller shearing edge is in a first plane which is at an angle to a second plane in which the anvil shearing edge is aligned.

Suitably, when the assembly is positioned such that the shearing plane is vertical, the first plane is at an angle to both the vertical and horizontal planes.

Preferably, the shearing edges abut at a position forward, relative to the operative direction, of both the anvil axis and primary axis. Preferably, the anvil axis is positioned forward relative to the operative direction, of the primary axis.

Suitably, the resilient properties of the arm are such that upon gripping the sheet, the position and angle of the abutment of the shearing edges is altered.

Preferably, the resilient properties of the arm are such that when the sheet is released from gripping, the position and angle of the abutting shearing edges is altered thereby providing a self sharpening thereof.

The said assembly may be powered by any suitable drive means.

Preferably, the assembly is operatively coupled to the drive means. wherein, in use, the assembly may pivot relative to the drive means to compensate for

undulations in sheeting.

Suitably, there are pivot limiting means for limiting the pivoted movement of the assembly relative to the drive means. Suitably, the assembly is operatively coupled to the drive means by an even number of Cogs rotatably mounted in the assembly.

BRIEF DESCRIPTION OF DRAWINGS In order that the invention may be readily understood and put into practical effect, reference will now be made to preferred embodiments illustrated in the accompanying drawings in which:

FIG 1 is a partially exploded perspective view of an assembly of a first embodiment of the invention;

FIG 2 is an assembled front view of FIG 1 ; FIG 3 is an assembled side view of FIG 1 ; FIG 4 is an assembled rear view of FIG 1 when shearing sheet material; FIG 5 is an exploded front view of an arm and anvil roller assembly of FIG 1 ;

FIG 6 is an exploded side view of FIG 5; FIG 7 is an unassembled side view of a body of the assembly of FIG 1 ; FIG 8 is an exploded rear view of the body and associated cogs arrangement of FIG 1 ;

FIG 9 is a side view of the cog arrangement of FIG 8;

FIG 10 is a side view of FIG 1 illustrating pivotal movement when shearing sheet material;

FIG 11 illustrates primary and anvil shearing rollers of FIG 1 ;

FIG 12 is a cross sectional view through P-P' of the primary and anvil shearing rollers of FIG 3;

FIG 13 illustrates the primary and anvil shearing rollers FIG 1, when shearing a sheet;

FIG 14 is a partially exploded perspective view of a second preferred embodiment of the invention;

FIG 15 is a rear view of FIG 12; and FIG 16 illustrates an alternative cog arrangement to that of FIG 9.

DETAILED DESCRIPTION

Referring to FIG 1 there is illustrated a hand operated shearing assembly 1 which includes a body 2 having a rotatably mounted primary shearing roller 8, a primary gripping roller 9, and an arm 4 mounting an anvil means 3 to body 2. A housing 5 is attachable to body 2 by screws 6 in apertures 7a and engaging threaded holes 7b. When attached to body 2, housing 5 rotatably mounts one end of a shaft 10 to body 2. Primary shearing roller 8 and an primary gripping roller 9 are either integrally formed with or mounted to shaft 10 and the other end of shaft 10 is rotatably mounted to body 2 (refer to FIG 8). This allows rotation of primary shearing roller 8 and primary gripping roller

9 about a common primary axis PA.

Anvil member 3 includes an anvil shearing roller 11 and an anvil gripping roller 12 mounted on a shaft 13 which is rotatably mounted to anvil to clamping members 26, 27 about an anvil axis AA.

The assembly 1 is pivotally mounted to a casing 14 the mounting being by operative coupling of shaft 10 to a drive means, such as a motor housed in casing 14. A hollow handle 15 is formed in casing 14 to which an electric switch 16 is attached. Switch 16 controls the supply of electric power to the motor and wires to the switch are located in hollow handle 15.

A pin 17 extends from casing 14 and through an arcuate slot 18 in body 2 which limits pivotal movement of assembly 1 with respect to casing 14.

Referring to FIGS 2 to 6, arm 4 has

resilient properties and is made from chrome steel and more specifically chrome vanadium. Arm 4 is mounted to body 2 by screws 19 located in apertures 20 of an arm flange 21 and engaging a respective thread in apertures 22 in body 2.

Shaft 13 is rotatably mounted on bearings 28 and 29 located in respective clamping members 26 and 27 which are clamped together by screws 65 passing through apertures 23 and 30 aligned with threaded holes 25 and 31 in clamping member 27.

The clamping of members 26 and 27 mounts anvil member 3 to arm 4 in which one of screws 55 passes through aligned aperture 23 of clamping member 26, an aperture 24 adjacent an end of arm 4 and engages threaded hole 25. When mounted, arm 4 is clamped in a recess 24a formed in clamping member 27, thereby restricting movement of anvil member 3 relative to arm 4.

When mounted to arm 4, anvil member 3 is suspended from body member 2. An anvil shearing roller shearing edge 32 which is a continuos annular edge of anvil shearing roller 11 is positioned to co- act with primary shearing roller shearing edge 33 which is a continuous annular edge of primary shearing roller 8.

Arm 4 is shaped and positioned relative to rollers 8, 9, 11 and 12 such that it allows assembly 1 to cut both left and right handed curves. As specifically illustrated in FIGS 3 to 5, a shearing plane SP defined by the co-acting shearing edges 32, 33 is positioned vertically. Accordingly, when shearing a sheet one sheared edge of a sheet section, illustrated by letter A, extends rearwardly and directly under a section 60 of arm 4. The other sheared sheet edge, illustrated by letter B, extends rearwardly and directly above a section 61 of arm 4. This configuration of arm 4 allows the assembly 1 to

shear both left and right handed curves, full circles and any sheet width. When rollers 8, 11 are at rest or are not shearing a sheet, shearing edges 32, 33 abut at resting position R. When shearing the sheet, the resilience of arm 4 allows the anvil axis AA to move relative to the primary axis PA, thereby the location of the abutment of shearing edges 32, 33 moves for example to position S.

Further, resting position R and shearing position S are positioned forward, relative to the operative direction of anvil axis AA and primary axis PA.

As shown in FIGS 7 to 9 body member 2 includes two bearing housing members 34 and 35 which house bearings 36, 37, 38, 39 and 40 in respective bearing housings 41, 42, 43, 44 and 45.

Housing members 34 and 35 are attached together by four countersunk screws 46a in apertures 46 and engaging aligned threaded apertures 47. A Cog 48 is mounted to a shaft 53 which is rotatably mounted to body member 2 at housed bearings 36 and 38. Cog 48 engages cog 49 which is mounted to a shaft 49a which is rotatably mounted to body member 2 at housed bearings 37 and 39. A Cog 50 is mounted to shaft 10 which is rotatably mounted to body member 2 at housed bearing 40 and a bearing 51 housed in a bearing housing 52 of housing member 5. Cog 50 engages cog 49 and attached to the same shaft 10 as cog 50 are primary shearing roller 8 and primary gripping roller 9.

Shaft 53 extends through housing 34 and is operatively coupled to a drive means or motor driven shaft enclosed in casing 14. Hence, rollers 8, 9 are operatively coupled to the motor driven shaft in which assembly 1 is mounted to the motor driven shaft by shaft 53.

As shown in FIG 10, assembly 1 pivots about

an axis of shaft 53, with respect to the casing 14 illustrated by the phantom outline. This is useful, for example, when cutting undulating or corrugated sheeting identified by letter C as assembly 1 can pivot relative to the motor driven shaft to compensate for undulations without the need for the user to adjust casing 14.

FIGS 11 to 13 illustrate the arrangement of primary and anvil rollers 8, 9, 11 and 12. Primary rollers 8 and 9 and shaft 10 are preferably turned or formed from a single metal rod in which roller 9 is of a smaller diameter than roller 8. Similarly anvil rollers 11 and 12 and shaft 13 are also preferably turned or formed from a single metal rod in which roller 12 is of a smaller diameter than roller 11. Rollers 8, 9, 11 and 12 are hardened and may be formed from tool steel .

As shown, a circumferential surface 54, of primary gripping roller 9, tapers along its axial length. Similarly, a circumferential surface 55, of anvil shearing roller 11 , also tapers along its axial length. Circumferential surfaces 54 and 55 are at an angle to each other, the angle decreasing when the sheet is sandwiched therebetween. A circumferential surface 56 of primary shearing roller 8, is parallel to primary axis PA and circumferential surface 57, of anvil gripping roller

12, is tapered along its axial length. Circumferential surface 54 has a gripping means in the form of a knurled surface cut therein.

Adjacent radial surfaces of rollers 8, 11 have annular recess 61 , 62 adjacent their respective shearing edges 32, 33. Shearing edge 32 is in a first plane which is at an angle to a second plane P2 to which the anvil shearing edge 33 is aligned. In this embodiment the first plane is the shearing plane SP.

As illustrated in the shearing plane SP is

positioned vertically and plane P2 is at an angle to the shearing plane SP. Plane P2 is also at an angle to the horizontal plane HP and therefore shearing edges 32, 33 toe in as they meet at resting position R which is forward of axes AA and PA.

In use, a user actuates switch 16 which supplied power to the motor which turns shaft 53. As a result, engaged cogs 48, 49 and 50 rotate thereby shaft 10, primary shearing roller 8 and primary gripping roller 9 rotate. Further, due to the abutment of surfaces 54 and 55, anvil shearing roller 11 and anvil gripping roller also rotate.

When rollers 8, 9, 11 and 12 contact a sheet edge their rotation pulls the sheet therebetween due to friction. Accordingly, the sheet prises open surfaces 54 and 55 which has the effect of reducing the gap between surfaces 56 and 57 which non parallel asis AA and PA rotate relative to each other. This provides a mechanism in which the sheet is sheared by the coaction of rotating shearing edges 32 and 33 and provides a constant shearing action whilst the rollers grip and sandwich the sheet which assists in providing relative movement between the sheet and assembly 1.

The prising of surfaces 54 and 55 and gap reduction of 56 and 57 has the effect of resiliently gripping the sheet wherein the resilient gripping results from the resilient properties of arm 4. This allows for varying thicknesses of sheeting to be sheared. In furthermore, the movement of the abutting position from the shearing position S to the resting position R alters the angle between the abutting shearing edges 32 and 33. As a result this provides a self sharpening of the edges whilst freely rotating.

Referring to FIGS 12 and 13, a second embodiment is illustrated in which the anvil mounting member, of the first preferred embodiment, is replaced with a shearing member (anvil) 58 having a shearing

edge 59 for co-acting with shearing edge 32 to provide a constant shearing action. Gripping roller 54 assists in providing relative movement between a sheet being sheared and the anvil 59. Arm 4 is configured to allow both left and right handed sheared curves in which one sheared edge, of sheet section A, extends rearwardly and under arm 4. The other sheared edge, of sheet section B, extends rearwardly above anvil 58. The shearing action and configuration of both embodiments is suited to cutting undulating or corrugated sheeting as there are no straight shearing edges contacting curved surfaces. Accordingly, deformations in the cut edge are eliminated or significantly reduced. The invention is also suited to shear sharp undulations and corners.

As illustrated in FIG 3, the position of anvil axis AA is positioned further forward than that of primary axis PA, the position being relative to the operative direction of assembly 1. This has the advantage of allowing the assembly to automatically pivot relative to the drive means which therefore allows for compensation for undulations in sheeting.

As illustrated in FIG 16, an additional cog 48a may be included between cogs 48 and 49 such that the primary roller is operatively coupled to the drive means by an even number of cogs. This has the advantage of assisting in automatic compensation when shearing undulations in sheeting in which before the assembly contacts the sheeting it is at its maximum forward pivotal position. This position is illustrated in FIG 10.

Although the invention has been described with reference to preferred embodiments, it is to be understood that the invention is not limited to the specific embodiments as herein described.