GB2040793A - Cutting tool - Google Patents

Abstract

In a cutting tool for scoring incisions on tiles and glass panes comprising a rotatable cutting wheel 23 on a handle 2, the problem of providing an inexpensive means for rotatably mounting the wheel is solved by a stub axle in the form of a half shear 22 produced in a mounting plate 19 of ductile material at one end of the handle 2. The half shear is at a position so that part of the cutting wheel circumference projects beyond the mounting plate 19. Means for preventing the wheel from unintentionally coming off the end of the half shear stub axle 22 may comprise a retaining member 24 pivoted to the plate 19 for limited swinging motion. In the case of a tile cutter, a second handle 1 carries a winged jaw 9 for co-operating with the mounting plate 19 to break a tile along a scoreline previously cut with the wheel 23. <IMAGE>

Description

SPECIFICATION Cutting tool The invention relates to a cutting tool comprising a blade in the form of a rotatable wheel for making incisions in work-pieces and has particular reference and application, but is not restricted, to a tile cutter for scoring linear incisions into tiles and glass panes.

The problem encountered with conventional such cutting tools is, inter alia, the provision of an inexpensive means for rotatably mounting the cutting wheel. The wheel should not markedly wobble in use and yet be readily replaceable by the user when worn. In its preferred form, the invention aims to solve both aspects of this problem.

According to the invention, a cutting tool comprises a handle and a blade in the form of an axially apertured cutting wheel rotatably supported on a stub axle upstanding from a mounting plate at one end of the handle, the stub axle being in the form of a half shear produced in the mounting plate at a position so that part of the cutting wheel circumference projects beyond the mounting plate and means being provided for preventing the wheel from unintentionally coming off the end of the axle.

In explanation, a half shear is a projection formed in a ductile material by a press comprising a die and a slug disposed on opposite sides of the material.

The slug enters the die as the press is closed and thereby also causes the material to flow and form an integral projection, the shape of the projection being determined by the complementary shapes of the slug and die and the extend of entry of the slug into the die being limited so that the projection does not become detached from the material in which it is formed.

It has been found that, despite its cheap production, a half shear stub axle provides an excellent bearing for the cutting wheel because its length and diameter can be very accurately controlled in the press. Hitherto, it has been conventional to machine the stub axle to be integral with an unapertured cutting wheel or to machine the mounting plate to provide an integral axle, but these are much more expensive constructions. So are those involving separately made axles.

The ductile mounting plate material is preferably sheet or plate steel which may have a thickness of, say, 3mm. Such a thickness is not only suitable from the point of view of producing the half shear stub axle but it also permits the entire handle to be made as a pressing from the same material and of the same thickness, thereby avoiding the need for securing a separately made mounting plate to the handle. Of course in this case it will be desirable to surround part of the handle with a covering sleeve or hollow grip for protecting the hand of the user.

The use of a half shear stub axle in accordance with the invention need not present difficulties in preventing the wheel from coming off the end of the axle unintentionally because, according to a preferred refinement, a retainer member is pivoted to the mounting plate for swinging motion between an operative position at which it overlies some of the wheel and an inoperative position at which one entire side of the wheel is exposed to enable the wheel to be withdrawn from the axle. If, as is preferred, the stub axle is substantially no longer than the thickness of the cutting wheel, the retaining member can, without having to be slotted to receive the axle, be disposed closely adjacent to the said one side of the wheel in its operative position and prevent axial displacement of the wheel that would lead to inaccurate cutting.

Preferably, the retaining member is screwconnected to the mounting plate, the screw serving as the pivot for the retaining member and passing freely through the mounting plate. The advantage of this is that, when the screw is turned in the loosening direction, frictional forces will automatically cause the retaining member to be swung to its inoperative position. Conversely, when the screw is then turned in the tightening direction, the retaining member is automatically swung back to its operative position. It is also preferred to provide positive stops for limiting the pivotal motion of the retaining member.The stops can be formed by two different sides of a single abutment on the retaining member positioned to abut an edge of the mounting plate with one side in the inoperative position of the retaining member and the same edge with the other side in the operative position of the retaining member.

The efficiency and accuracy of cutting is primarily dependent on a flawless cutting edge on the wheel but, although cutting wheels are increasingly made of tungsten carbide which is more expensive and, despite its hardness even more susceptible to damage than other steels, no-one has hitherto thought of suitable means for protecting the wheel. This problem is even more acute in the case of a dual or multi-purpose hand tool where there is every chance of additional damage occuring to the wheel or hands of the user whilst the tool is being used for a function other than cutting with the wheel.

In one form of the invention, therefore, a shield is provided for the said projecting part of the cutting wheel circumference. The shield can be hinged to the retaining member by one end, which is bifurcated, and be a releasable snap fit on the retaining member with its other end. Desirably, the retaining member is also provided with a lubricating hole which is in registry with the half shear stub axle when the retaining member is in its operative position. To facilitate the flow of lubricant through the hole, the free end of the half shear is preferably slightly domed.

Yet another desirable optional feature of the invention is that non-confronting faces of the mounting plate and wheel retainer are flat, smooth and preferably also parallel to each other. This facilitates use of the tool by running it along a straight edge or rule for cutting straight lines.

The invention is particularly useful for incorporation in a so-called tile or glass cutter which, in addition to the wheel for first scoring a line in a tile or glass pane workpiece, is provided with means for breaking the workpiece along the scoreline in a subsequent operation. In the case of such a tile or glass cutter, the invention provides for a pair of pivoted handles, one of which terminates at its operative end in the aforementioned mounting plate with the upstanding end in the aforementioned mounting plate with the upstanding half shear stub axle.The operative end of the other handle is provided with a jaw defining a recess aligned with the mounting plate so that, when the workpiece is placed between the mounting plate and jaw with the scoreline approximately in registry with the mounting plate opposite the recess and the handles are then squeezed, the workpiece will break along the scoreline.

Other advantageous features will become apparent from the following description of an example of the invention with reference to the accompanying drawings, wherein:- Figure 1 is an exploded perspective view of a tile cutter; Figure 2 is an elevation of one side of the Figure 1 cutter; Figure 3 is a simplified plan view thereof; Figure 4 is a sectional elevation taken on the line IV-IV in Figure 2; Figures 5 and 6 are respectively an elevation of the other side and a front elevation; Figure 7 is a simplified enlarged composite side elevation of the jaws, and Figures 8 and 9 are enlarged fragmentary side elevations of one of the jaws showing a wheel retainer and shield in respectively different posi tions.

The illustrated tile cutter comprises two handles 1, 2 made as pressings from 3 mm sheet or plate metal such as steel and each provided with a plastics sleeve or hand grip 3 for protecting the hands of the user. The handles intersect near one end (the operative end) and are pivotally interconnected by a steel rivet held in place by the rivet head 4 at one end of the shank and an internally serrated corrugated washer 6 pushed over the other end of the shank. At its operative end, the handle 1 terminates in an integral plate 7 having an aperture 8 and carries a jaw 9 which is bifurcated at one end and has oblique cheeks 11 at the other end. The bifurcations 12 are apertured at 13 so that, when the plate 7 is inserted between them with the apertures 8 and 13 in registry, a hollow split peg 14 known as a Spirol pin can be sprung into the holes to hold the jaw 9 on the plate 7.The edge of the plate 7 is provided with a flat 16 which co-operates with the root 17 of the bifurcations to prevent rotation of the jaw, as will be particularly evident from Figure 5.

By reason of their relative inclination, the cheeks 11 of the jaw 9 define a recess which is enlarged by a transverse central channel 18. After the jaw 9 has been assembles with the plate 7, its channel 18 is disposed in alignment with a mounting plate 19 integral with the handle 2 at its operative end. In use, a scored workpiece such as a tile 21 (Figure 7) is positioned between the mounting plate 19 and jaw 9 so that the scoreline is approximately in registry with the mounting plate but faces the jaw 9. When the handles are squeezed, the plate 19 and jaw 9 co-operate to break the tile along the scoreline. To achieve this, it is not essential for the tile to be accurately located with the scoreline exactly parallel to the channel axis, nor for the mounting plate 19 to have a knife edge for acting on the tile.Further, the channel 18 is not essential, the recess or hollow defined by the cheeks 11 being sufficient to enable the tile to fracture under the action of two side forces exerted in one direction by the ends 20 of of the cheeks and a central force in the opposite direction exerted by the mounting plate.

Indeed, instead of inclined cheeks, the jaw 9 may have a flat face, the recess being defined by a projecting rib (not shown) at each end 20. Alternatively, the recess can be defined by the face of the jaw being concave between its ends 20.

By appropriately shaping the mounting plate, the composite representation of Figure 7 shows that variously thick workpieces can be accommodated between it and the jaw 9; the maximum thickness is about 12.5 mm. The jaw 9 is positioned so that the edges (or ribs) at the ends 20 of the cheeks 11 are inclined to point to the rivet head 4, as is shown in Figure 2.

The mounting plate 19 is formed in accordance with the invention with an upstanding half shear 22 having a domed tip. This half shear serves as a stub axle for rotatably supporting an axially apertured tungsten carbide cutting wheel 23 which, in the case here in question, is to be used to score the tile 21 as a preliminary operation.

The half shear stub axle is located at a position so that part of the cutting wheel circumference projects beyond the mounting plate. The length of the stub axle is preferably substantially no greater than the wheel thickness, as is shown in Figure 4. It can be shorter, provided that there is sufficient length for properly supporting the wheel 23. If the stub axle is made longer than the wheel is thick, a retaining member 24 for the wheel 23 needs to be provided with a hole for receiving the excess axle length and, since the retaining member is preferably pivotable, such a hole would have to be in the form of a slot, as will become apparent hereinafter.

For the purpose of keeping the cutting wheel 23 on the axle except when it is to be removed intentionally for replacement, the retaining member 24 is stepped on one face to form a boss 25 by which it rests on the mounting plate 19 and has a recess in which the wheel 23 is received with just sufficient clearance to enable it to turn. This is best shown in Figure 4. The retaining member is pivoted to the mounting plate by a cheese head screw 26 which passes freely through a hole 27 in the mounting plate and a hole 28 in the retaining member to enage a polygonal nut 29 seated in a complementary countersunk receptacle 31 of the retaining member.

The retaining member can be swung from the operative position of Figure 8, where it overlies most of one side of the wheel 23, to the inoperative position of Figure 9, at which the entire side of the cutting wheel is exposed to enable it to be withdrawn from the stub axle 22. This swinging motion is effected automatically simply by loosening the pivot screw 26 with a screwdriver and the retaining member is automatically swung back when the screw is tightened. To limit swinging of the retaining member between the operative and inoperative positions, the retaining member is provided with a single abutment 32 projecting from its boss. One side of the abutment strikes an edge of the mounting plate 19 in one limiting position and another side strikes the same edge in the other limiting position, as shown in Figures 8 and 9.

To protect the part of the cutting wheel circumference that projects beyond the mounting plate 19, a transparent shield 33 is hinged to the retaining member. The shield has slightly converging apertured legs which straddle the retaining member and are sprung into engagement with pivot pins 34 provided on opposite sides of the retaining member.

To expose the cutting wheel for replacement or use, the shield 33 is swung open as shown in Figures 2 and 9. For storage, or when the tool is being used to break a tile, the shield 33 can be snapped into the closed position in that a lip 36 on the shield engages behind a shoulder 37 on the retaining member 24, as shown in Figures 5 and 8.

For efficient turning and also for cutting, the wheel 23 can be lubricated through an oil hole 38 provided in the retaining member at a position where it is in registry with the half shear stub axle 22 when the retaining member is in its operative position. The domed tip of the stub axle 22 ensures that the oil hole is not completely obstructed.

It will be noted especially from Figure 4, that the non-confronting outer faces of the mounting plate 19 and wheel retainer 24 are flat, smooth and parallel to facilitate the ruling of scorelines or other incisions by running either face along a straight edge.

It will be evident that the aforementioned pivot screw 26 for the retaining member 24 is not essential. In an alternative construction, it is replaced by a pivot pin formed on the retaining member and swaged over at its end, or by a rivet.

Claims (16)

1. A cutting tool comprising a handle and a blade in the form of an axially apertured cutting wheel rotatably mounted on a stub axle upstanding from a mounting plate at one end of the handle, the stub axle being in the form of a half shear produced in the mounting plate at a position so that part of the cutting wheel circumference projects beyond the mounting plate and means being provided for preventing the wheel from unintentionally coming off the end of the axle.

2. Atool according to claim 1, wherein the mounting plate is in one piece with the handle in the form of a metal pressing.

3. Atool according to claim 2, including a covering sleeve or hollow grip around part of the handle.

4. Atool according to any preceding claim, including a retaining member pivoted to the mounting plate for swinging motion between an operative position at which it overlies some of the wheel and an inoperative position at which one entire side of the wheel is exposed to enable the wheel to be withdrawn from the axle.

5. Atool according to claim 4, wherein the stub axle is substantially no longer than the thickness of the cutting wheel.

6. Atool according to claim 4 or claim 5, wherein the retaining member is screw-connected to the mounting plate, the screw serving as the pivot for the retaining member.

7. Atool according to any of claims 4 to 6, wherein the swinging motion of the retaining member is limited at the inoperative and operative positions by an abutment on the retaining member striking an edge of the mounting plate.

8. A tool according to any preceding claim, including a shield for the projecting part of the cutting wheel circumference.

9. A tool according to claim 8 when appended to claim 4, wherein the shield is hinged to the retaining member.

10. A tool according to claim 9, wherein the shield is a snap fit behind a shoulder on the retaining member when the shield is closed over the cutting wheel.

11. A tool according to any one of claims 4 to 10, wherein the retaining member is provided with a lubricating hole in registry with the stub axle when the retaining member is in its operative position.

12. Atool according to claim 11, wherein the free end of the stub axle is domed.

13. Atool according to any one of claims 4 to 12, wherein non-confronting faces of the mounting plate and wheel retainer are flat and smooth.

14. Atool according to any preceding claim in the form of a tile or glass cutter, including a further handle pivoted to the first-mentioned handle and means on the handles for breaking a tile or glass workpiece along a previously scored line when the handles are squeezed.

15. A tool according to claim 14, wherein the breaking means comprise the said mounting plate and a jaw on the further handle, the jaw defining a recess aligned with the mounting plate.

16. A cutting tool substantially as hereinbefore described with reference to the accompanying drawings.