Saw blade and saw assembly

Abstract: A saw blade assembly comprises a laminated structure of three side-by-side parallel strips, one two or all of which may have spaced teeth formed along one edge. Where only one strip has teeth, it is sandwiched between the two other strips and the teeth are of triangular shape when seen in plan and are bevelled on both edges to produce pointed tooth tips. Where two strips have teeth, the strips are arranged one on each side of a centre strip. Again, the teeth are of triangular shape when seen in side elevation and are contoured to form pointed tips. The roots of the teeth on one strip are spaced laterally from the roots of the teeth on the other strip because of the presence of the centre strip. In another form, each strip has teeth along one edge, the assembly thereby providing three parallel, side-by-side rows of teeth. The teeth are of triangular shape when seen in side elevation and are contoured to form pointed tips.

Description: This invention relates to saw blades and saw blade assemblies and has particular although not exclusive reference to saw blades and assemblies for power saws. U.S. Patent Specification No. 2,784,751 describes a power saw with a saw blade comprising a three-piece laminated assembly. The laminations are of strip form with saw teeth along one edge thereof, each tooth being contoured to form a chisel edge at its tip. The centre strip is of reduced top-to-bottom dimension as compared with the outer strips thereby providing a longitudinal groove along the upper edge of the assembly in which locates the edge of a blade support and guide. The assembly will not cut certain materials satisfactorily. U.S. Specification No. 810,530 describes a saw blade with deep concave cuts or gullets located between groups of teeth. Each set comprises combined rake and cutting teeth, the sides of which next to the gullet are approximately straight and at right angles to the cutting edge of the blade. The other sides of the rake and cutting teeth are inclined. Between the inclined sides of each pair of rake teeth in each group is a triangular cutting tooth whose sides are sharpened. The cutting teeth are set inwardly and outwardly alternately. U.S. Specification No. 4,423,553 describes a hand saw with a blade along whose lower edge is provided a plurality of alternately splayed main and auxiliary cutting teeth. The exposed sides of the cutting teeth are tapered to a sharp edge. U.S. specification 1 537 980 describes a saw blade assembly comprises a laminated structure having two parallel side-by-side outer strips each having formed along one edge thereof a row of spaced teeth extending longitudinally of the assembly, wherein the roots of the teeth in one of the rows are spaced laterally from the roots of the teeth in the other row by a centre, parallel-edged, toothless spacer strip extending longitudinally between the two outer strips and fixed thereto, which centre strip does not project beyond a base line joining the roots of the teeth in the rows. According to the present invention, a saw blade assembly comprising a laminated structure having two parallel side-by-side outer strips each having formed along one edge thereof a row of spaced teeth extending longitudinally of the assembly, and wherein the roots of the teeth in one of the rows are spaced laterally from the roots of the teeth in the other row by a centre, parallel-edged, spacer strip extending longitudinally between the two outer strips and fixed thereto, which centre strip does not project beyond a base line joining the roots of the teeth in the rows is characterised in that the spacer strip is toothless, the lower longitudinal extending face of the facer strip being a flat plane. At least some of the teeth in each row of the above saw blade assembly may be set outwardly. In one embodiment of the invention, every tooth in both rows is set outwardly. In another embodiment, the remaining teeth in both rows are set inwardly. Each tooth may be of triangular form when seen in side elevation and contoured to provide a pointed tooth tip. Each tooth may be bevelled on at least one edge to provide the pointed tip. Some at least of the teeth may be bevelled on both edges to provide the pointed tip. The bevelling may be on one face of the tooth. Some of the teeth may have a bevel or bevels on the inside face of the tooth while others may have a bevel on the outside face. In one embodiment, the teeth in both rows have a bevel or bevels on their inside faces. In another embodiment, alternate teeth in each row have a bevel or bevels on their inner faces, the remaining teeth having a bevel or bevels on their outside faces. The teeth in each row may be arranged in pairs along the length of the assembly, each pair being separated from the next pair by a distance greater than that between the teeth of a pair. One tooth of a pair may be bevelled on its inside face and set outwardly while the other tooth of the pair is bevelled on its outside face and set inwardly. The teeth of one row may lie centrally of the spaces between the teeth of the other row. The assembly may be of a laminar structure comprising two parallel, side-by-side outer strips having rows of spaced saw teeth extending longitudinally of the assembly, the roots of the teeth in one row being spaced laterally from the roots of the teeth in the other row, each tooth being of triangular shape when seen in side elevation and being bevelled on at least one edge to produce a pointed tip, alternate teeth in both rows being bevelled on one tooth face, the remaining teeth being bevelled on the other tooth face, the teeth in each row being arranged in pairs, each pair in a row being separated from the next pair in the same row by a distance greater than that between the teeth of a pair. The inner strip may be dimensioned to provide a longitudinal guide groove between the outer strips. Alternatively, the inner strip may be dimensioned to provide a longitudinal guide projecting from the outer strips. The assembly may have a tooth in at least one of the rows closely adjacent the forward end of the assembly. Alternatively, both rows may have teeth closely adjacent the forward end of the assembly. The invention also comprises a power saw comprising a support for supporting and guiding a saw blade or assembly, a saw blade or assembly mounted upon the support, and a drive for reciprocating the blade or assembly relatively to the support, and in which the assembly is as defined. The support may comprise a longitudinal guide surface located in the longitudinal channel of a saw blade assembly of laminar construction. The support may be of laminar construction and may comprise side-by-side members of which the inner member provides a guide surface along which the saw blade reciprocates. Alternatively, the laminar construction of the support may comprise two side-by-side members contoured to provide a channel along the length of the support in which the saw blade or assembly reciprocates. The laminar construction may alternatively comprise side-by-side members contoured to provide a longitudinal channel along the length of the support in which the saw blade or assembly reciprocates. In another form, the laminar construction of the support comprises two side-by-side members, the longitudinal edge of one of which forms a tongue along which the saw blade or assembly reciprocates. By way of example only, embodiments of the invention will now be described in greater detail with reference to the accompanying drawings of which: Fig. 1 is a side view in diagrammatic form only of a power saw with a housing part removed to reveal internal mechanism, certain other components also being removed, Fig. 2 is a part section on the line II-II of Fig. 1, Fig. 3 is a part section on the line III-III of Fig. 1, Figs. 4, 5, 6 and 7 are explanatory diagrams of alternative forms of support for saw blades/assemblies, Fig. 8 is a side view of a first embodiment of a saw blade assembly, Fig. 9 is an end view in the direction of arrow A in Fig. 8 and on a larger scale, Fig. 10 is a side view on a larger scale of part of the embodiment of Fig. 8, Fig. 11 is a side view of a second embodiment, Fig. 12 is an end view in the direction of arrow B in Fig. 11 on a larger scale, Fig. 13 is a side view on a larger scale of part of the embodiment of Fig. 11, Fig. 14 is a side view of a third embodiment, Fig. 15 is an end view in the direction of arrow C on Fig. 14 and on a larger scale, Fig. 16 is a side view on a larger scale of the part of the third embodiment, Fig. 17 is a side view of a fourth embodiment, Fig. 18 is an end view in the direction of arrow D of Fig. 17 and on a larger scale, Fig. 19 is a side view on a larger scale of a part of the fourth embodiment, Fig. 20 is a side view of a fifth embodiment, Fig. 21 is an end view in the direction of arrow E in Fig. 20 on an enlarged scale, Fig. 22 is a side view on a larger scale of a part of the fifth embodiment, Figs. 1, 2 and 3 show a power saw for use with the blade assemblies described below. The saw comprises a housing 10 of clam shell construction that provides a handle 11 and has a forwardly projecting blade support strip 12. The housing may also have a second handle adjacent the strip 12. The support 12 extends into the housing 10 and is secured in position at points 13. The housing accommodates an electric driving motor 14 with an output shaft 15 whose lower end (as seen in Fig. 1) is formed as a pinion 16 meshing with a gear wheel 17 rotatably mounted upon a shaft 18 supported in the upper wall of a housing 19 formed between the clam shells. Secured to the gear wheel 17 is a disc 20 from which extends a driving pin 21 located towards the edge of the disc. The pin 21 engages a transverse slot 22 in an elongate drive member 23 mounted in bearings 24 for longitudinal reciprocatory movement. The forward end of drive member 23 carries a clamp 24 by means of which a reduced width portion of a saw blade assembly can be secured to the member. Energisation of motor 14 is controlled by a trigger-operated switch 26 located in handle 11, the necessary electrical connections being omitted from Fig. 1 for the sake of clarity. Although not so shown in Fig. 1, the lower edge 27 of the support 12 is contoured as a guide surface for the saw blade assembly and provides a channel in which locates the upper part of a blade assembly or alternatively, a tongue of the assembly. Energisation of the motor 14 results in rapid to and fro movement of the drive member 23 as indicated by the limits in Fig. 3 and of the saw blade. A suitable speed of movement is about 3300 blade strokes per minute with an amplitude of about 40 mm. The amplitude is related to the tooth pitch of the saw blade and preferably the pitch should not exceed about 70%-85% of the amplitude of movement of the blade. It is not essential that the saw blade assembly be guided by the blade support in the manner described above. For example, the guide groove may be formed by adopting a laminar construction for the blade support. Fig. 4 shows such a laminar construction. Outer blade support members 28 are secured to an inner blade support 29 and extend downwardly beyond the latter to create a guide groove 30. Alternatively, and as shown in Fig. 5, the blade support may comprise only two laminar members 31, 32 formed along their lower edges to create a guide channel 33. The laminated form of blade support may also be used to create a guide edge that locates in a gap of the saw blade assembly described below. Such a form is shown in Fig. 6. Fig. 7 shows a somewhat different form of blade support comprising two laminates, one of which 34 is upset along its lower edge as indicated at 35 to provide a longitudinal tongue located centrally of the other laminate 36. It will be understood that the set of the teeth of the saw blade assembly must be sufficient to exceed slightly the maximum overall thickness of the blade support irrespective of the precise form of the latter. The saw blade assembly shown in Figs. 8-10 comprises a laminated structure formed of two outer strips 41, 42 formed with teeth 43, 44 respectively along their lower (as viewed in Fig. 8) edges. The right-hand (as viewed in Fig. 8) end portions of the strips 41, 42 are of a reduced depth as compared with the remainder of the strips and as indicated at 45. There are no teeth along the lower edge of the reduced depth portions. The outer strips 41, 42 are separated by an inner strip 46 whose depth is considerably less than that of the major parts of the strips 41, 42 and slightly less than the depth of the portions 45. The inner strip 46 is so located that its lower edge (as seen in Figs. 8 and 9) is level with the roots of the teeth 43, 44 thus forming a longitudinal gap 47 between the upper parts of the strips 41, 42. There is thus formed a saw blade assembly in which the roots of the teeth 43, 44 are spaced from one another laterally by the gap 47 equal to the thickness of the inner strip 46. The teeth 43, 44 are of triangular form when seen in side elevation as in Fig. 8, the bases of the triangles forming the roots of the teeth. The teeth are arranged in pairs on each strip and the sloping edges are bevelled on their facing sides as indicated at 48 to form points at the tips of the teeth. Thus, the extreme left-hand tooth 49 shown in Fig. 10 is the first of the teeth 44. The next tooth 50 is the first of the teeth 43 and is bevelled on its outside face, the next tooth 51 is the second of the teeth 43 and is bevelled on its inside face. The next tooth 52 is second of the teeth 44 and is bevelled on its inside face whilst the next tooth 53 is the third of the teeth 44 and so on. The bevels taper towards the edges of the teeth as can be seen from Fig. 10. Pairs of teeth on one strip locate centrally of the space between pairs of teeth on the other strip, the teeth being equal-spaced along the length of the assembly. That is to say, the distance between each pair of teeth is greater than that between the teeth of a pair. Alternate ones of the teeth 43 are set outwardly as indicated at 54 in Fig. 9 whilst the others are set inwardly as indicated at 55. In similar manner, alternate teeth of teeth 44 are also set outwardly as indicated at 56 in Fig. 9, the remaining teeth being set inwardly as indicated at 57. Thus, in each pair of teeth, one tooth is bevelled on its inside face and set outwardly while the other tooth of the pair is bevelled on its outside face and set inwardly. The outward sets are sufficient to ensure that the tooth points lie externally of the faces of the outer strips 41, 42 as can be seen from Fig. 9 and externally of the faces of a support as will be described below. In the form of blade assembly of the form shown in Figs. 8, 9 and 10, the strips are of a thickness of about 0.7 mm and of a depth, as measured from the upper edge to the tooth points, of about 20 mm. The depth of each tooth as measured from root to point is about 5.0 mm. The depth of the slot 47 is about 6.0 mm. The pitch of the teeth 43, 44 is about 24.0 mm. The first tooth of the teeth 43 lies at the left-hand end of strip 41 while the first tooth of teeth 44 is spaced from the left-hand end of strip 42 to give the tooth locations referred to above. At the other ends of the strips 41, 42, the extreme right-hand tooth is one of teeth 44. The included tip angle at the tooth point is about 42°. The distance between adjacent teeth when the assembly is viewed from the side is about 6.0 mm. The tooth configuration of the assembly shown in Figs. 8, 9, 10 is suitable for general wood-cutting operations in timber and may also be used to cut other materials. The saw blade assembly shown in Figs. 11, 12 and 13 is generally similar to that shown in Figs. 8, 9 and 10 and similar references are used. In the assembly of Figs. 11, 12 and 13, the teeth are arranged singly and each tooth on one strip lies centrally of the gap between adjacent teeth on the other strip. Further, all the teeth are bevelled on their inside faces to produce pointed tips, the outside faces being plain. Additionally, all teeth on both strips are set outwardly as indicated at 58, 59 in Fig. 12, sufficiently to ensure that the tooth points lie externally of the outer strips and of the support as will be described below. Thus, referring to Fig. 13, tooth 60 is the first of the teeth 44 and is bevelled at 48 on its inner face-that face visible in Fig. 13. Tooth 61 is the first of the teeth 43 and is also bevelled on its inner face (not visible). Tooth 62 is the second of the teeth 44, the bevelling 48 on the inner face being visible in Fig. 13. Tooth 63 is the second of the teeth 43 and is bevelled on its inner face (not visible), and so on. The materials and dimensions of the assembly shown in Figs. 11-13 are the same as those of the assembly of Figs. 8-10 except that the tooth pitch is about 12.0 mm. The embodiment of Figs. 11-13 is particularly suitable for cross cutting timber. The saw blade assembly shown in Figs. 14-16 is suitable for fine cutting. In construction, it is similar to the embodiments already described but the tooth configuration is different. Again, similar references are used as in Figs. 11-13. Teeth on the same strip are alternately bevelled on inner and outer faces and set inwardly and outwardly. Thus, and as seen in Fig. 16, tooth 64 is the first tooth of teeth 43 and is bevelled at 48 on its outer face - the one visible in Fig. 16. Tooth 65 is the first tooth of teeth 44 and is bevelled at 48 on its inner face (also visible in Fig. 16). Tooth 66 is the second tooth of teeth 43 and is bevelled on its inner face (not visible). Tooth 67 is the second tooth of teeth 44 and is bevelled on its outer face (not visible). In all cases, the non-bevelled faces are plain. Alternate ones of teeth 43 and of teeth 44 are set outwardly, the remainder being set inwardly. The setting can be seen in Fig. 15 and the outwards setting ensuring that the tooth points lie outside the outer strips and of the support as will be described below. Each tooth of teeth 43 lies centrally of the gap between adjacent teeth of teeth 44 and vice versa. The depth (i.e. the dimension from tooth root to tooth point) is about 5.0 mm and the tooth pitch is about 12.0 mm. The included angle and the point of the teeth is about 36°. Otherwise the dimensions of the blade assembly of Figs. 14-16 are identical with those of the assembly of Figs. 8-10 except that the spacing between successive teeth when the assembly is seen in side elevation is about 3.0 mm. The saw blade assembly shown in Figs. 17-19 is particularly suitable for coarse rip cutting. The general construction of the assembly shown in Figs. 17-19 is similar to that of the assembly shown in Figs. 8-10 and similar references are used but the tooth contour and tooth pitch are different. The teeth are arranged in pairs on each strip, the teeth of a pair being bevelled alternately on inner and outer faces on one edge only. The teeth of a pair are also set alternately inwardly and outwardly, the outward setting being as described above. Thus, tooth 68 shown in Fig. 19 is the first of teeth 43 and is bevelled at 69 along the left-hand side only of the tooth on the inner face thereof - the face visible in Fig. 19. Tooth 70 is the second of teeth 43 and is bevelled along edge 71 on the inner face - the face not visible - thereof. Tooth 72 is the first of teeth 44 and is bevelled at 73 along the right-hand side only of the tooth on the inner face - the face visible in Fig. 19. Tooth 74 is the second of the teeth 44 and is bevelled along edge 75 on the inner face - the face not visible - of the tooth and so on. In each case, the bevelling is such as to produce a pointed tip on the tooth. As can be seen from Figs. 17 and 19, the non-bevelled edge of each tooth is inclined more steeply to the lower edge of the respective strip than is the bevelled edge, the inclination being slightly different for each tooth of a pair. In addition, the included angles at tooth tips are slightly different for each tooth of a pair. Approximate value of the angles just referred to are given on Fig. 19. The tooth pitch is about 22 mm and each pair of teeth on one strip lies centrally of the gap between the pairs of teeth on the other strip, the arrangement producing a series of equal-spaced teeth along the length of the assembly. The distance between the teeth of each pair is about 8.00 mm while the distance from a tooth point to the upper edge of the assembly is about 20.0 mm. The tooth height from tip to root is about 7 mm. The general construction of the assembly shown in Figs. 20-22 is similar to that shown in Figs. 8-10. Outer strips 41, 42 with teeth 43, 44 along their lower edges (as seen in the drawings) are separated by an inner strip 46 dimensioned to leave a longitudinal gap 47 between the upper parts of the outer strips 41, 42. The teeth on the strips 41, 42 are arranged in pairs and are arranged so that a pair on one strip lies centrally of the space between a pair on the other strip and so that seen in side view the teeth are equal-spaced along the length of the assembly. The teeth are of triangular form when seen in side view and both edges of the triangle are bevelled to produce a pointed tip. In each pair of teeth, one is bevelled on its inside face and is set outwardly while the other tooth of the pair is bevelled on its outside face and is set inwardly. The other sides of the teeth are plain. Thus, the first tooth 44a as seen in Fig. 22 is bevelled on its outside face (not visible) and is set inwardly. The second tooth 43a is bevelled at 48 on both edges on its outside face, i.e. the face visible in Fig. 22, and is set inwardly. The next tooth 43b is bevelled on its inside face (not visible) and is set outwardly. Teeth 43a and 43b form the first pair of the teeth 43. The next succeeding tooth 44b is bevelled on its inside face (that visible in Fig. 22) and is set outwardly. The next succeeding tooth 44c forms a pair with tooth 44b and is bevelled on its inside face (not visible) and is set outwardly. The tooth pattern then repeats. The tooth pitch of the embodiment of Figs. 20-22 is about 36.0 mm while the apex angle of the teeth is about 40°. The dimensions are otherwise similar to those of the embodiment of Figs. 8-10. The teeth are however more widely spaced, the distance between successive teeth when the assembly is seen in side view is about 6 mm. In all the embodiments described above with reference to Figs. 8-22, the strips 41, 42 and 46 are of a high carbon steel for example a 1.0% carbon steel. Other materials may be used provided they can be secured by spot welding if that method is to be used. Fabrication may comprise stamping from flat strip after which the bevels may be formed by grinding. The offsetting of the teeth is carried out in the conventional manner. The laminated construction described is preferred, the laminations being secured together by spot welding along the length of the assembly. The spot welds are sufficiently close to eliminate any risk of the strips separating between the welds. Other methods of securing the strips together may be used, for example, they may be secured together by means of an industrial adhesive. It is not essential that the strips all be of the same thickness nor that a laminated construction be used. Fabrication from a one-piece strip may be used but this is expensive. Alternatively, the inner strip may be formed from thickened portions on the adjacent faces of the outer strips. The strips are relatively thin as compared, for example, with a jig-saw blade, the strength of the assembly being derived at least in part from the laminated construction and in part by the use of a blade assembly support and guide. In alternative forms of the embodiments described above, smaller tooth spacing or pitches may be used such that there is a slight overlap of tooth roots along the length of the assembly. The blade assemblies described above with reference to Figs. 8-22 are suitable for use in a power saw as described above, the end portions 45 being clamped to a reciprocating drive member in the drive mechanism of the saw. The assemblies are also suitable for use in a manual saw which may be a bow saw and which may incorporate a support and guide for the assembly as described below and a handle by which the saw is held and operated. The gap between the roots of the teeth 43, 44 provides a space in which saw dust and chips can accumulate during use and this increases efficiency of cut. In addition, the location of a tooth closely adjacent the extreme left-hand or forward end of a strip allows the blade assembly to be used for "blind cutting", i.e. a cut made into the surface of work piece and which does not start at an edge thereof. If desired, each of the rows may have a tooth closely adjacent the extreme left-hand or forward end of the respective strip. The set of the outwardly set teeth is such that the points of these teeth clear the thickness of the support guide of the power saw, i.e. they produce a saw cut of slightly greater width than the thickness of the support. Energisation of the motor 40 described above results in rapid to and fro movement of the drive member 49 as indicated by the limits in Fig. 3 and of the saw blade assembly. A suitable speed of movement is about 3300 blade assembly strokes per minute with an amplitude of about 40 mm. The amplitude is related to the tooth pitch of the saw blade assembly and preferably the pitch should not exceed about 70%-85% of the amplitude of movement of the assembly. It is not essential that the saw blade assembly be guided by the blade support in the manner described above. For example, the saw blade assembly may incorporate an inner strip that projects upwardly beyond the outer strips 41, 42 in a manner as shown in Fig. 4 and locate in a guide groove in the blade support. The guide groove may be machined into a single piece blade support but can be created by adopting a laminar construction for the blade support similar to that shown above in Fig. 6. Outer blade support members are secured to an inner blade support member and extend downwardly beyond the latter to create a guide groove. Alternatively, the blade support may incorporate only two laminar members formed along their lower edges to create a guide groove. A somewhat different form of blade support may comprise two laminates, one of which is upset along its lower edge to provide a longitudinal tongue located centrally of the other laminate. The general arrangement is similar to that shown in Fig. 7 above. The set of the outwardly set teeth is such that the points of the teeth clear the thickness of the support guide of the power saw, i.e. they produce a saw cut of slightly greater width than the thickness of the support guide. It will be appreciated that other forms of drive than that described above may be used to reciprocate the saw blade assembly.

Claims: A saw blade assembly comprising a laminated structure having two parallel side-by-side outer strips (41, 42) each having formed along one edge thereof a row of spaced teeth (43, 44) extending longitudinally of the assembly, and wherein the roots of the teeth (43) in one of the rows are spaced laterally from the roots of the teeth (44) in the other row by a centre, parallel-edged, spacer strip (46) extending longitudinally between the two outer strips and fixed thereto, which centre strip (46) does not project beyond a base line joining the roots of the teeth (43, 44) in the rows characterised in that the spacer strip is toothless, the lower longitudinal extending face of the facer strip being a flat plane. An assembly as claimed in Claim 1 characterised in that some at least of the teeth in each row are set outwardly with respect to the structure. An assembly as claimed in Claim 2, wherein every tooth (43, 44) in both rows is set outwardly. An assembly as claimed in Claim 2, wherein the remaining teeth in the rows are set inwardly with respect to the structure. An assembly as claimed in any one of the preceding claims, wherein each tooth (43, 44) is of triangular form when seen in side elevation and contoured (48, 48) to form a pointed tooth tip. An assembly as claimed in Claim 5, wherein each tooth is bevelled on at least one edge (48) to form the pointed tip. An assembly as claimed in Claim 6, wherein some teeth have a bevel or bevels (48) on the outside face of the tooth. An assembly as claimed in Claim 6, wherein alternate teeth (51 ...) in each row (43, 44) have a bevel or bevels on their inner faces, the remaining teeth (50 ...) in the row having a bevel or bevels (48) on their outside faces. An assembly as claimed in Claim 1, wherein the teeth (50, 51: 52, 53) in each row (43, 44) are arranged in pairs (50, 51: 52, 53) along the length of the assembly, each pair (50, 51) being separated from the next pair by a distance greater than that between the teeth of a pair. An assembly as claimed in Claim 9, wherein one tooth in a pair of teeth is bevelled on its inside face and set outwardly, the other tooth in the pair of teeth being bevelled on its outside face and set inwardly. An assembly as claimed in Claim 10, wherein the inner strip (46) is dimensioned to provide a longitudinal guide for the assembly. A saw blade assembly according to any one of Claims 1 to 11, comprising a laminated structure wherein the structure comprises two parallel, side-by-side outer strips having rows of spaced teeth extending longitudinally of the assembly, the roots of the teeth in one row being spaced laterally from the roots of the teeth in th other row by an inner spacer strip (46) extending longitudinally between the two outer strips and fixed thereto which inner strip does not extend beyond the roots of the teeth in the rows, each tooth being of triangular shape when seen in side elevation and being bevelled on at least one edge to produce a pointed tip, alternate teeth in both rows being bevelled on one tooth face, the remaining teeth being bevelled on the other tooth face, the teeth in each row being arranged in pairs, each pair in a row being separated from the next pair in the same row by a distance greater than that between the teeth of a pair. An assembly as claimed in any one of claims 1-11, wherein the teeth (43, 44) of each outer strip (41, 42) are equi-spaced along the length of the strip. A power saw comprising a support (12) for supporting and guiding a saw blade assembly and a drive (14,15,16,17 ....23) for reciprocating the assembly characterised in that the saw blade assembly comprises an assembly as claimed in any one of the preceding claims. A power saw as claimed in claim 14, wherein the support comprises a longitudinal guide surface (29) located in a longitudinal channel of the saw blade assembly. A power saw as claimed in Claim 14 or 15, wherein the support is of laminar construction (28, 29). A power saw as claimed in Claim 16, wherein the support comprises side-by-side members (38, 29) an inner one (29) of which provides a guide surface along which the saw blade assembly reciprocates. A power saw as claimed in Claim 16, wherein the support comprises two side-by-side members (31) contoured to provide a channel (33) along the length of the support and in which the saw blade assembly reciprocates. A power saw as claimed in Claim 16, wherein the support comprises two side-by-side members (34, 36), the longitudinal edge (35) of one of which forms a tongue along which the saw assembly reciprocates.

Inventors: STONES KEVIN, WOOTTON MALCOLM JAMES, STONES, KEVIN, WOOTTON, MALCOLM JAMES
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1986
Main classification: B27B33
IPC codes: B23D61