A SAFETY KNIFE OR CUTTER

Abstract: A knife or cutter comprises a body (1) suitable to be gripped manually, a blade (2) projecting from the body (1), a guard plate (6) adjacent to the blade (2) and facing the cutting element thereof, and an attachment member (7) attaching the guard plate (6) to the body (1), the attachment member adjacent to its attachment to the guard plate being thin and being forward of the blade and aligned therewith, such that when material to be cut is introduced between the body and the guard plate, and pressure is applied on the body, the cutting element presses the material to be cut against the guard plate. The attachment member is preferably flexible. A groove (10) or slot is provided in the guard plate (6), aligned with the blade (2). Various forms of attachment member are described and illustrated. A knife is also described having a replaceable blade unit (14) comprising a multipoint blade (17) not rotatable mounted inside a housing, the blade being rotatable between rest positions in which all of the parts (18) of the blade are within the housing and cutting positions in which one of the points of the blade projects from the housing and extends outside the body.

Description: Title of the Invention A SAFETY KNIFE OR CUTTER Technical Field This invention relates to a knife or cutter with a safety shield assembly. The knife or cutting tool is intended for many uses in cutting materials, particularly sheet materials such as paper, fabric, cardboard, plastic, film, floor coverings and the like and is generally of the type used in manual cutting tasks, "Do-It-Yourself" or home improvements work or by craftworkers. Hereinafter in this description and claims the word "knife" is used to include a cutter or cutting tool. -Known knives of this type are usually provided with very sharp blades, which give rise to two different problems. Firstly when cutting a material on a table or other substrate, the blade tends to cut down into the substrate, causing damage to it. Secondly, a sharp blade when projecting from a knife can cause injury if it encounters a hand or other part of the body of the user or of another person. It is an object of the invention to overcome these problems. French Patent 2639574 Longet et a l describes a safety cutter having a slidable cover to hide the blade and a heel which is located under the material to be cut, the heel being joined to the main body of the cutter by a thin and tapered body part which permits the passage of the cut material. The slidable cover has a foot, and the material to be cut is inserted between this foot and the heel of the tool. However in order to accommodate materials of different thickness it is necessary to relocate the slidable cover, and there is no way of pressing the blade onto the material to be cut against a firm backing. The blade does not have an exposed point and the cutting edge is angled such that cutting is effected from beneath the material to be cut which would make it difficult to cut on a line. The heel is of substantial thickness and would not easily slide between a sheet material (such as paper) and a table, workbench or other substrate on which the material is laid. US Patent 4 167810 Gilbert describes a cutting tool for sheet material, especially for opening cardboard cartons, which has a guide member of bent wire fixed to its handle for keeping the blade in cutting engagement with the sheet material and away from the contents of the carton. One arm of the guide member is above the blade tip so as to keep the blade from disengagement from the sheet material. Another arm of the guide member is below the tip of the blade for preventing cans or other carton contents from being cut by the blade. The guide member restricts access to the blade cutting edge, which is said to provide a measure of protection for the user, especially the user's finger. However there is nothing to prevent the blade tip being pushed through the guide member, so that this tool could not be safeJy used on a table top or other sensitive substrate, and the tip could then come into contact with part of the user's body. Also, a single wire, pressed down onto a table or other sensitive substrate, could cause damage thereto. Disclosure of the Invention The present invention provides a knife comprising a body, a blade having a cutting element projecting from the body, a guard plate adjacent to the blade and facing the cutting element thereof, and an attachment member for attaching the guard plate to the knife, the attachment member adjacent to its attachment to the guard plate being thin and being forward of the blade and aligned therewith, such that when material to be cut is introduced between the body and the guard plate, and pressure is applied on the body, the cutting element presses the material to be cut against the guard plate. Normally the cutting element has a point or tip at an end thereof. Such a cutting element is called a "pointed cutting element". Preferably the attachment member is flexible and more particularly is a spring member. Alternatively, flexibility may be provided by a hinged joint, suitably at or adjacent to the attachment point to the guard plate, the hinged joint preferably having a limited amount of pivotal movement. Flexibility allows a gap between the blade and the guard plate to be closed when pressure is applied on the blade. It also facilitates use of the knife at a variety of angles to the substrate. Flexibility also allows paper fragments to be cleared from the blade point between cuts e.g. by "snapping" the guard plate away from the point and dislodging the paper fragments. In a preferred embodiment, a groove or slot is provided in the guard plate, aligned with the blade. Although the blade presses the material to be cut against the guard plate, the blade tip should not reach the base of the groove in order to minimize wear on the blade tip. The groove or slot may be short, suitably extending for less than 25% of the length of the guard plate, as it only needs to be long enough to receive the point of the blade. Preferably the attachment member is a thin strip suitably having a thickness (perpendicular to the blade) not more than 5 times, more preferably not more than 2.5 times, the thickness of the blade. The attachment member should be thin enough to permit easy passage of it along the cut made in the material by the blade. If desired the spring member may comprise a substantially rigid upper portion, e.g. having a V-shaped cross section with the apex of the V facing the blade, and a lower spring portion adjacent to its attachment to the guard plate. The guard plate suitably comprises a rigid abrasion resistant plastics material. It should be readily slidable on a smooth substrate surface and it may be described as a "skid". The guard plate suitably is of generally triangular shape, tapering rearwardly. It preferably has a width of at least 0.5cm, more suitably a width in the range 1 to 2 cm at it widest point e.g. the base of the triangle. Other preferred features of the invention are defined iϊl " the ~ claims. According to another aspect, the present application provides a knife comprising a body and a replaceable blade unit which fits inside the body, wherein the blade unit comprises a housing and a multi-point blade rotatably mounted inside the housing, the blade being rotatable between rest positions in which all the points of the blade are within the housing and cutting positions in which one of the points of the blade projects from the housing and extends outside the body. Preferably the blade is rotatable by means of a spindle which carries a knob outside the body and which has a portion engageable with the blade inside the housing. In the preferred embodiment the spindle carries a locking mechanism, for retaining the blade in either a rest position or a cuttjng position, the locking mechanism being releasable by axial retraction of the spindle. In a further aspect, the present invention provides a blade unit for a knife, comprising a housing and a multi-point blade rotatably mounted inside the housing, the blade being rotatable between rest positions in which all of the points of the blade are within the housing and cutting positions in which one of the points of the blade projects from the housing. Preferably the blade has four points. Most preferably the blade has a generally square configuration with indentations in the four sides. The blade may be star-shaped. In the preferred embodiment, the housing has one dimension slightly greater than the diagonal distance between opposed points on the blade and a second dimension at right angles thereto which is less than the said distance but slightly greater than the length of a side of the blade. Brief Description of Drawings The invention is illustrated in the accompanying drawings, in which: Figure 1 is a pictorial view of a first embodiment of a knife according to the invention. Figure 2 is a side elevation of the knife of figure 1. Figure 3 is a top plan view of the knife of Figures 1 and 2. Figure 4 is a detailed pictorial view of the guard plate and spring member. Figure 5 is a pictorial view of a second embodiment of a knife according to the invention. Figure 6 is an elevation of the knife of Figure 5 from one side. Figure 7 is an elevation from the other side of the knife of Figure 5 and 6, showing a flap open. Figure 8 is an exploded projection of the knife of Figures 5 to 7. Figure 9 is a side elevation of a multi-point blade for the knife of Figures 5 to 8. Figure 10 is a projection of the multi-point blade. Figure 11 is a projection of a box housing for holding the blade. Figure 12a and 12b is a pair of projections showing the blade inside the box unit in two different orientations, the rest position (a) and the cutting position (b). Figure 13 is a pictorial view of a shield assembly from above. Figure 14 is a view similar to Figure 10 of an alternative blade. Figure 15 is an exploded view of a third embodiment of a knife according to the invention. Figure 16 is an elevation on the centre line of one variant of a knife of the third embodiment. Figure 17 is a similar elevation of a second variant. Figure 18 is a similar elevation of a third variant. Figure 19 is a similar elevation of a fourth variant. Figure 20 is a similar elevation of a fifth variant. Figure 21 is a similar elevation of a sixth variant. Figure 22 is an exploded view of a fourth embodiment of a knife according to the invention. Figure 23 is an elevation on the centre line of one variant of a knife of the fourth embodiment. Figure 24a is an elevation of a metal part for the variant of Figure 23. Figure 24b and 2c are elevations of alternative metal parts. Figure 25 is an elevation similar to Figure 23 of a second variant. Figure 26 is an elevation of a blade for the variant of Figure 25. Figure 27 is an exploded view of a fifth embodiment of a knife according to the invention. Figure 28 is an elevation on the centre line of one variant of the fifth embodiment. Figure 29 is a similar elevation of a second variant. Figure 30 is a similar elevation of a third variant. Figure 31 is an elevation of a metal part for the variant of Figure 30. Figure 32 is an exploded view of a sixth embodiment of a knife according to the invention. Figure 33 is an enlarged view of a shield assembly for the embodiment of Figure 32. Figure 34 is an elevation on the centre line of the embodiment of Figure 32. Figure 35 is a pictorial view of an alternative version of the embodiment of Figure 1. Modes for carrying out the invention Where similar features appear in the various embodiments, the same reference numerals are used or are understood. As shown in Figures 1 - 3, a knife according to the invention comprises a body 1 suitable to be gripped manually, a blade 2 projecting from the body, and a shield assembly 3 adjacent to the blade. The body 1 and blade 2 may be similar to those of a conventional "trimmer" knife such as is sold under the Trade Mark STANLEY. The blade 2 may suitably be housed in replaceable manner inside the body 1, with one triangular portion o the ~ bTade projecting from the ~ bτjdy. The triangular portion has a sharp point 4 and a cutting edge 5 which extends generally parallel to the longitudinal direction of the body. The shield assembly comprises a guard plate 6 and a thin spring member 7 by which the guard plate 6 is attached to the body 1. The spring member 7 suitably comprises a thin strip of metal which is anchored at the top end 8 to the body. A free portion 9 of the strip extends downwardly in front of the body on the vertical mid-line of the body and thus is aligned with the blade. At its bottom end the spring member is fixed to the guard plate 6 suitably of plastics material. The guard plate lies underneath the point 4 and cutting edge 5 of the blade, which provides the pointed cutting element of the blade. In the rest position of the spring member 7, there is a gap "a" between the blade 2 and the guard plate 6 (see Figure 2). As shown in the drawings, the guard plate has the shape of an isosceles triangle -with the apex pointing rearwardly. However the guard plate may -if desired have at least one edge parallel to the longitudinal direction of the body so that the guard plate can be moved along a straight edge such as a ruler when the knife is being used. As shown in the drawings, the guard plate is a thin plate with parallel top and bottom surfaces and a thickness of the order of 0.5 - 1.5 mm. However it may if desired have converging top and bottom surfaces reducing from a thickness of 3-3.5mm at the front edge (where it is attached to the spring member) down to a minimal thickness e.g. 0.25 mm at the trailing edge or apex. The guard plate preferably has a groove 10 in its top surface, aligned with the blade 2. During cutting the blade enters the groove but the blade point 4 should not reach the base of the groove so that it is kept sharp. Optionally, the shield assembly includes a nose 11, suitably of transparent plastics material, which encases the front of the body and protects the spring member. The nose 11 does not extend downwardly as far as the point 4 of the blade. The spring member 7 may be anchored by its upper limb 8 in the nose ' ll, to the body 1. In use, the body is gripped by hand and the guard plate 6 is placed on a table, work bench or other smooth substrate surface. An edge of the material to be cut is introduced between the guard plate 6 and the body 1. Pressure is then applied on the body, the spring member 7 flexes and the point 4 of the blade is pressed against the guard plate 6. The knife is pulled rearwardly, causing the blade to cut the material which is trapped against the guard plate, with the groove 10 (if present) defining a line on which the material is not supported so that the blade can more easily cut through it. As the knife is drawn rearwardly, the guard plate slides on the substrate surface, the spring member 7 enters the cut formed in the material, and the material passes on either side of the spring member. The guard plate protects the table (or other substrate surface) from-being cut by the knife. When the knife is not in use, the guard plate shields the blade and prevents accidental damage or injury being caused by the exposed blade. If desired, a roller 12 may be mounted in the underneath surface of the body 1, above the rear portion of the guard plate 6 to facilitate movement of the knife over the material to be cut, the material being pressed against the guard plate by the roller and to restrict the depth of entry of the blade point into the groove 10. The roller may be formed in two parts with a mid-axial gap so that it does not interfere with the blade. Alternatively the roller may be replaced by roller bearing(s). The roller or roller bearing(s) may be spring-mounted in the body. The nose 11 suitably has a pair of internal walls (not shown) which extend longitudinally on either side of the spring member 7 to restrict possible movement of it out of alignment with the blade. The spring member 7 may be anchored in the nose 11 rather than directly onto the body. The shield assembly comprising the nose 11, spring member 7 and guard plate 6 may be made and supplied as an accessory to existing knives, with suitable means being provided for securing the assembly to the knife e.g. the nose 11 may be extended rearwardly as far as assembly screw holes in the body of the knife (see Figure 15 below, holes 43 and 44) and a pair of corresponding holes may be provided in the extended nose so that a screw used for assembling the knife body can also be employed to secure the shield assembly. As shown in Figures 5 to 14, a second embodiment of a knife according to the invention comprises a handle 2 adapted to be gripped manually and a body 1 which houses a blade unit 14. The body has a shield assembly 3 similar to that described in relation to Figures 1 to 4. The shield assembly comprises a guard plate 6 and a spring member 7 by which the guard plate is attached to the body 1. The spring member comprises a thin strip of metal which is anchored at the top end 8 to the body. A free portion 9 of the strip extends downwardly at the front of the body, inside a nose portion 11 which encloses the front of the body and protects the spring member. The free portion 9 of the strip is on the vertical mid-line of the body and thus is aligned with the blade (described below). It is preferably formed of a strip of metal bent into a V-shaped cross section, with the ridge pointing rearwardly. At its bottom end the spring member is fixed to the guard plate 6 which extends underneath the blade. As shown in the drawings, the guard plate has the shape of an isosceles triangle with the apex pointing rearwardly. However the guard plate may if desired have at least one edge parallel to the longitudinal direction of the body so that the guard plate can be moved along a straight edge such as a ruler when the knife is being used. The guard plate suitably comprises a rigid abrasion-resistant plastics material. It should be readily slidable on a smooth substrate surface and it may be described as a "skid". It has converging top and bottom surfaces reducing from a thickness of 3 to 3.5mm at the front edge (where it is attached to the spring member) down to a minimal thickness e.g. 0.25mm at the trailing edge or apex. The guard plate has a groove 10 in its top surface (or a slot extending through the guard plate) aligned with the ~ bladeτ During cutting the blade enters the groove but the blade point should not reach the base of the groove so that it is kept sharp. A roller 12 is mounted at the rear of the body, above the apex of the guard plate, to facilitate movement of the knife over material to be cut, the material being pressed against the guard plate by the roller, and to restrict the depth of entry of the blade point into the groove 10. Alternatively the roller may be replaced by roller bearing(s). The roller or roller bearing(s) may be spring mounted in the body. The body has a flap 13 in one side wall. As illustrated, this flap 13 is hinged at the top of the body 1. However it may alternatively be slidable relative to the body. A blade unit 14 may be installed inside the body via the opening 15 in the side wall 26 which is revealed by moving the flap 13. The blade unit comprises a hollow box 16 which houses the multi-point blade 17. As shown the blade has four points 18 each with cutting edges 19, 20 leading to the point. The blade resembles a square with slightly indented edges. The blade 17 is rotatably mounted in the box 16, e.g. by means of annular ribs (not shown) which project axially from the blade around the central hole 22 and fit slidably inside corresponding annular ribs (not shown) on the inside of the side walls of the box. Figure 8 shows a divider wall inside the body 1, against which the blade unit 14 buts. Slots to accommodate the spring member 7 and a recess to accommodate the top end 8 of the spring member are also shown in Figure 8. The box 16 has a generally rectangular cross section, with a width slightly greater than the diagonal span of the blade from point to point, but with a height less than this diagonal span but greater than the length of a side of the blade. The blade is mounted in the box with its centre spaced from the top of the box by a distance slightly greater than one half of the diagonal span of the blade, and spaced from the bottom of the box by a distance less than one half of the diagonal span of the blade. Thus the blade can be turned from the position of Figure 12a, in which the blade is entirely housed inside the box (with its sides parallel to the edges of the box), to the position of Figure 12b in which one point 18 of the blade projects downwardly from the box through a slot 21 in the base thereof. The blade point 18 extends below the bottom edge of the body 1 into a position in which it can cut material between the body 1 and the guard plate 6 (see Figure 6). The blade 17 has a central hole 22 which as illustrated is hexagonal but which could be square or another non-circular shape or could have grooves to receive splines. The hexagonal hole 22 co-operates with a hexagonal portion of a spindle 23 which extends through the body and carries a knurled knob 33 outside the body, beside one side wall 24. If the hole 22 is other than hexagonal, the cooperating portion of the spindle 23 has a complementary shape. The spindle is rotatable in round apertures 25 in the side walls 24,26. Mounted on the spindle, inside the side wall 24, is a spring 27 and a locking member 28 comprising a disc with two diametrically opposed pins 29 projecting therefrom parallel to the spindle. These pins enter into a pair of holes 30 in one side wall 24 of the box 16 which has a circular array of eight holes 30 spaced equiangularly. The locking member 28 has a hexagonal hole 31 which is mounted on the spindle 23 to be rotatable therewith, retained by a ring 32, which may suitably be a rubber 0-ring. The pins 29 can enter into any pair of the holes 30 to retain the spindle 23 and thus the blade 17 in a particular orientation. For example in the orientation of Figure 12a, the pins 29 would be engaged in holes 30a, while in the orientation of Figure 8b, the pins would be in holes 30b. In either position, the pins (which are held by the holes 30 in the side wall 24 of the box 16) lock the spindle and thus the blade 17 against rotation, so that in the orientation of Figure 12b one blade point 18 can be used for cutting while in the orientation of Figure 12a the blade is safely stowed inside the box. The box can only be inserted into or removed from the body with the blade in the position of Figure 12a. This is also the position of the blade when the blade unit is packaged for supply to the consumer. To rotate the blade from one position to the next, the user pulls the knob 33 in an axial direction to withdraw the pins 29 from the holes 30 in the side wall 24. The spring 27 is compressed between the box 16 and side wall 24. The user then rotates the knob by one eighth of a revolution and the blade 17 is turned accordingly from the position of Figure 12a to that of Figure 12b (or vice versa). The pins 29 then enter into the next pair of holes 30, urged by the spring 27. The blade 17 can be turned progressively so that each of the cutting edges 19 on the four points of the blade are used. When these have become blunt, the blade unit 14 can be removed from the body 1 via the opening 15 and can be reinserted in the reversed position, so that the cutting edges 20 on the points of the blade are used for cutting. A ratchet mechanism may be incorporated if desired, to restrict rotation of the spindle to one direction and to ensure that it stops in each of the eight chosen positions (Figures 12a and 12b). If desired, a pair of small rollers or feet, preferably spring-mounted, may be provided alongside or ahead of the blade point to press the material being cut against the guard plate. Instead of having a rectangular cross section, the blade unit 14 could be circular with a diameter slightly greater than the diagonal span of the blade but with one segment cut away so that a blade tip 18 protrudes (as in Figure 12b). In either case, the blade unit should be shaped to fit neatly inside the hollow body 1, so that it does not move inside the body during use. If desired, the flap 13 could be omitted and one side wall of the blade unit 14 could fill the opening 15 in the side wall 26 of the body. In use, the knob 33 is rotated to bring a blade point 18 to the position of Figure 12b. The handle 2 is then gripped by hand and the guard plate 6 is placed on a table, work bench or other smooth substrate surface. An edge of the material to be cut is introduced between the guard plate 6 and the body 1. Pressure is then appl ed on the body, the spring member 7 flexes and the point 18 of the blade is pressed towards the guard plate 6. The knife is pulled rearwardly, causing the blade to cut the material which is trapped against the guard plate, with the groove 10 defining a line on which the material is not supported so that the blade can more easily cut through it. As the knife is drawn rearwardly, the spring member 7 enters the cut formed in the material, and the material passes on either side of the V-shaped spring member. The guard plate protects the table (or other substrate surface) from being cut by the knife. When the knife is not in use but the blade has not been rotated to the position of Figure 12a, the guard plate shields the blade point and prevents accidental damage or injury being caused by the exposed blade. The knives of the invention are particularly useful for cutting paper. As the knife is not adapted for sharpening pencils, a conventional pencil sharpener may be incorporated into the body e.g. at the end of the handle remote from the blade. Figure 14 shows an alternative form of multiple-use blade which is similar to that of Figure 9 except that the blade tips 18 have been omitted. Each cutting edge 19 is spaced from the opposed cutting edge 20 by a flat portion 35 which defines a point where it meets each of the cutting edges 19, 20. Thus the use of cutting edge 19 does not blunt the point on cutting edge 20. Figure 15 shows a third embodiment which is based on a knife body of conventional type which is divisible into two parts 40, 41 on the longitudinal centre line, and a standard blade 42 which is retained between the two body parts when the body is assembled and held together by a screw through holes 43, 44 in conventional manner. The body part 40 has a boss 45 which has a bore therein, with its axis transverse to the longitudinal centre line. A groove is cut in each body part 40, 41, extending from the front edge to the boss 45. The guard plate 46 has a longitudinal bore 47 in its front edge and a short groove or slot 48 in its top surface, connected with the bore. The groove or slot extends only for a minor part of the length of the guard plate, as it is only required to receive the point 4 of the blade. A spring member 49 comprises a rear arm 50 adapted to be received between the body parts 40, 41 in the mating pair of grooves described above, with a finger 51 at right angles to the rear arm 50, adapted to be received in the hollow boss 45. The spring member has a coil portion 52 extending forwardly and upwardly, below which there is an inclined portion 53 which is displaced sidewardly so that the main limb 54 of the spring member is aligned with the arm 50 (and thus is aligned with the blade 42) when the unit is assembled. At the lower end of the main limb 54, the spring member has a foot portion 55 which enters into the bore 57 in the guard plate 46 and is secured therein. Figure 16 shows the embodiment of Figure 15 in the assembled position., The guard plate 46 mounted on the spring member 49 can flex into-alternative positions which are shown in dotted outline, so that the knife can be used at a variety of angles to a substrate. The point of the blade 42 enters into the central slot 48 of the guard plate 46 so that the point is enclosed therein. This embodiment uses a standard blade, which moves relative to the anvil or guard plate 46, ensuring firm contact at the cutting point. The spring action allows paper fragments which may accumulate at the blade point to be cleared after each cutting action. The blade engagement in the anvil slot centres the blade on the spring limb 54, so that it can pass through the paper (or other material being cut). The closeness of the spring limb 54 to the cutting point allows a tight cutting radius, if the knife is being used for making curved cuts. Figure 17 shows a variant on the embodiment of Figure 15 and 16, in which the arm 50a of the spring member is longer so that the coil 52 and the limb 54 are spaced in front of the blade 42. The cutting point of the blade is nevertheless engaged in the slot 48 in the anvil 46. Figure 18 shows another variant on the embodiment of Figures 15 and 16, in which the coil portion 52a of the spring is directed rearwardly and downwardly so that the two coils of the spring can embrace the front edge 56 of the standard blade 42. This puts the coil in a less exposed position, and maintains the limb 54 in alignment with the blade. The guard plate 46 can flex as in the variants of Figures 16 and 17 to allow paper fragments to be cleared. Figure 19 shows a further variant on the embodiment of Figure 16, in which the coil portion 52b of the spring is located about half way down the limb 54, which is formed as two inclined portions so that the coil is offset in front of the edge 56 of the blade. The two coils of the spring 52b embrace the front edge 56 of the blade to a minor extent. The offset spring allows flexing and vertical collapse of the assembly i.e. the guard plate 46 moves up to the blade in a parallel movement. Figure 20 shows a further variant on the embodiment of Figure 18, in which the arm 50a of the spring member extends downwardly and rearwardly from the coil 52a, alongside the front edge of the body, and the finger 51 is received in a hole A in the blade. Two holes A are provided in the blade to allow both points to be used. Figure 21 shows a further variant on the embodiment of Figure 18, in which the guard plate 46 does not have a central slot 48, so that the point of the blade 42 acts against the top surface of the guard plate 46. The embodiments of Figures 18 to 21 are particularly suitable for use with a shielding nose such as shown in Figures 1 to 3. The coil embracing the blade is sufficient to retaining centering. Figure 22 shows a fourth embodiment in which the body parts do not require modification, but a special blade 62 of reduced height is used. This blade has a notch 63 in its top edge. The attachment member 64 is formed as a pressed metal part which comprises a retaining portion 65, and two inclined limb portions 66, 67 joined at an elbow 68. _ The _ τetϊtπtng portion 65 has the shape of the upper part of a conventional blade, with a notch 69 in its upper surface in the appropriate position for the seating notch of a conventional blade. On its lower edge, the retaining portion 65 has a projection 70 which mates with the notch 63 on the blade 62. Thus the retaining portion 65 and the blade 62, when assembled together, occupy the space of a conventional blade inside the assembled body portions 40, 41. The upper limb 66 is inclined forwardly and downwardly from the retaining portion 65 and the lower limb 67 is inclined rearwardly and downwardly therefrom. The lower limb 67 fits into the bore 47 in the guard plate 46, which also has a central slot 48. The guard plate can be replaced by pulling it off the lower limb 67 and pushing a fresh guard plate 46 into position. The assembled position of this embodiment is shown in Figure 23. The metal part is shown in elevation in Figure 24. Although this embodiment may lack the flexibility of the preceding embodiments, it is particularly suitable for cutting cardboard or shrink wrap film where the problem of accumulated paper fragments at the blade tip is not encountered. The metal part may, if desired, be made of spring steel and flexibility may be provided at the elbow 68. Figure 24b shows an alternative version of the metal part in which the lower limb 67 has been twisted through 90° at the elbow 68, so as to allow for flexibility and also to arrange the lower limb 67 with smaller dimension (i.e. the thickness of the metal) in the plane of the guard plate 46. This has the advantage that the aperture 47 can have a reduced height and the thickness of the guard plate 46 can be reduced, as compared to Figure 22. Figure 24c shows a further alternative version of the metal part in which a spring or concertina region is provided in the upper limb 66 so that flexibility is achieved in the attachment member. This feature may be used along or in combination with the feature of Figure 24b. In another embodiment, a pressed metal retaining bar 65 is combined with a spring member as in one of the embodiffients ' Of " Figures 15 to 21 i.e. the limb 50 and finger 51 of the spring member are replaced by the retaining portion 65, the two elements being welded or otherwise secured together. Figure 25 shows a further variant which utilizes a custom-made blade 72 which resembles a type of blade already commercially available. The blade 72 is of conventional height and fits into the body parts in conventional manner. It has two limbs depending downwardly and inwardly from an elbow on its front and rear edges. These limbs form the same function as the lower limb 67 in the embodiment of Figure 22, and can be pushed into the bore 47 in guard plate 46. The blade 72 has a cutting edge which is generally parallel to the limb 73 and terminates in a cutting point 74. The guard plate 46 is replaceable. Figure 27 shows a further embodiment which is similar to that of Figures 22 to 24, utilizing a blade 62 of reduced height. The shield assembly comprises a blade retaining part 65 with a limb 76 inclined downwardly and forwardly therefrom. The guard plate 80 comprises a part of the metal part which has been folded at right angles to the limb 76. A removeable plastic cover 81 can be slid onto the guard plate 80. Figure 28 shows the assembly without the plastic cover 81, while Figure 29 shows the plastic cover in position. A space 77 is provided between the limb 76 and the guard plate 80. The plastic cover 81 has a slot 78 which partly accommodates the limb 76 and partly extends over the space 77, so that the blade point can enter into this part of the slot. Figures 30 and 31 show an alternative form of the metal part. The limb 76a is indented and the guard plate 80a has an edge 83 which (before folding) lies in the indented region, leaving a space 82 between the limb 76a and the edge 83. The guard plate 80a also has a slot 84 on its centre line. When the guard plate 80a is folded so that it is at right angles to the limb 76a (as shown in Figure 27) the slot 84 is aligned with the limb 76a. It therefore allows the blade point to enter into this slot. Figures 32 to 34 show a further embodiment, in which the shield assembly is formed as a moulded plastics unit which is mounted on a special blade 92 having holes 93 therein. The assembly 85 comprises a flexible loop portion 86 with a plate portion 87 inclined downwardly and rearwardly therefrom, with a channel-shaped flange 88 at the free end thereof. A stud 89 projects tranversely from the plate 87. The loop portion 86 is extended downwardly and forwardly into a thin limb 90 which is of similar thickness to a blade. A guard plate 91 extends rearwardly from the base of the limb portion 90. The shield assembly can be snapped onto a blade 92, with the plate portion 87 alongside the blade and the stud 89 entering through one of a pair of holes 93 in the blade. Part of the cutting edge of the blade is housed in the flange 88. The assembly flexes about the loop portion 86, so that the guard plate can be snapped back after cutting to clear away debris. Figure 35 shows an alternative version of the embodiment of Figures 1 to 4 in which the shield assembly 3a includes a nose 111 which is extended rearwardly around the body 1 to the region where a screw 112 is used to secure two parts 113 and 14 of the body together. This screw 112 also passes through holes in the nose 111 to retain the shield assembly 3a in position on the knife. The spring member 7 is anchored by its top limb 8 in the nose 111. The shield assembly 3a may be sold as an accessory for conventional knives. Industrial Applicability The invention provides new knives and accessories therefor which are suitable for manufacture and sale to the general public and to workers in the building and craft trades and the like.

Claims: CLAIMS 1. A knife comprising a body (1, 40-41, 113-114), a blade (2, 17, 42, 62, 72) having a cutting element (4-5) projecting from the body, a guard plate (6, 46, 80-81, 80a, 91) adjacent to the blade and facing the cutting element thereof, and an attachment member (7, 49, 64, 85) for attaching the guard plate to the knife, the attachment member adjacent to its attachment to the guard plate being thin and being forward of the blade and aligned therewith, such that when material to be cut is introduced between the body and the guard plate, and pressure is applied on the body, the cutting element presses the material to be cut against the guard plate. 2. A knife according to claim 1 wherein the attachment member (7, 49, 64, 85) is flexible. 3. A knife according to claim 1 or 2 wherein the attachment member (7, 49, 64, 85) is a spring member. 4. A knife according to any of the preceding claims wherein a groove or slot (10, 48, 84) is provided in the guard plate, aligned with the blade. 5. A knife according to any of the preceding claims wherein the attachment member (7, 49, 64, 85) adjacent to its attachment to the guard plate (6, 46, 80-81, 80a, 91) is a thin strip having a thickness (perpendicular to the blade) not more than 5 times the thickness of the blade. 6. A knife according to any of the preceding claims having a roller (12) or roller bearing mounted in the underneath surface of the body, above the rear portion of the guard plate. 7. A knife according to any of the preceding claims having a shield assembly which includes a nose (11, 111) which encases the front of the body and protects the attachment member but does not extend downwardly as far as the point of the blade. 8. A knife according to claim 3 wherein the spring member (49) includes two coils (52, 52a), preferably parallel. 9. A knife according to claim 8 wherein the two coils (52, 52a) at least partially embrace the blade (42) between them. 10. A knife according to any of the preceding claims wherein the attachment member (7, 49, 64, 85) attaches the guard plate (6, 46, 80, 80a) to the body. 11. A knife according to any of claims 1 to 9 wherein the attachment member (49, 64, 85) attaches the guard plate (46, 91) to the blade (42). 12. A knife according to claim 1 wherein the attachment member includes a bar (65) seatable in part of a space in the body which conventionally receives a blade. 13. A knife according to claim 12 wherein the attachment member (64) is a pressed metal part. 14. A knife according to claim 13 wherein the attachment member (64) and guard plate (80) are integrally formed, and the guard plate is folded generally at right angles to the plane of the attachment member. 15. -A knife according to claim 1 wherein the attachment member (73) is an integral part of the blade (72). 16. A knife according to claim 1 wherein the attachment member (85) and the guard plate (91) are integrally moulded in plastics material. 17. A shield assembly for a knife which comprises a body (1, 40-41, 113-114) and a blade (2, 17, 42, 62, 72) having a cutting element (4-5) projecting from the body, said shield assembly comprising a guard plate (6, 46, 80-81, 80a, 91) to be placed adjacent to the blade and facing the cutting element thereof, and an attachment member (7, 49, 64, 85) for attaching the guard plate to the knife, the attachment member adjacent to its attachment to the guard plate being thin and being locatable forward of the blade and aligned therewith, such that when material to be cut is introduced between the body and the guard plate, and pressure is applied on the body, the cutting element presses the material to be cut against the guard plate. 18. A shield assembly according to claim 17 which includes a nose (11, 111) for encasing the front of the body and protecting the attachment member. 19. A knife comprising a body and a replaceable blade unit (85) which fits inside the body (1), wherein the blade unit comprises a housing (16) and a multi-point blade (17) rotatably mounted inside the housing, the blade being rotatable between rest positions in which all of the points (18) of the blade are within the housing and cutting positions in which one of the points of the blade projects from the housing and extends outside the body. 20. A knife according to claim 19 wherein the blade is rotatable by means of a spindle (23) which carries a knob (33) outside the body and which has a portion engageable with the blade inside the housing. 21. A knife according to claim 20 wherein the spindle carries a locking mechanism (28) for retaining the blade in either a rest position or a cutting position, the locking mechanism being releasable by axial retraction of the spindle (23). 22. A blade unit for a knife comprising a housing (16) and a multi-point blade rotatably mounted inside the housing, the blade (17) being rotatable between rest positions in which all of the points (18) of the blade are within the housing and cutting positions in which one of the points of the blade projects from the housing.

Inventors: HOOD OLIVER, LANE THOMAS ANTHONY, HOOD, OLIVER, LANE, THOMAS, ANTHONY
Applicants: HOOD OLIVER, LANE THOMAS ANTHONY, HOOD, OLIVER, LANE, THOMAS, ANTHONY
Application year: 1995
Main classification: B26B5
IPC codes: B26B5, B26B25