GB2177344A

GB2177344A - Saws

Info

Publication number: GB2177344A
Application number: GB08616000A
Authority: GB
Inventors: Tai-Her Yang
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-07-01
Filing date: 1986-07-01
Publication date: 1987-01-21
Also published as: GB8616000D0; GB8516633D0

Abstract

A saw 20 comprising an elongate toothed blade 22 has teeth 23 extending from one end 22a and facing the other end, and a set of teeth 24 extending from the other end and facing the end 22a. An untoothed edge or neutral tooth 25 may be located between the sets of teeth 23 and 24. The teeth may be of gradually varying pitch or may comprise groups of teeth, the teeth of each group having a constant pitch. <IMAGE>

Description

SPECIFICATION A saw This invention relates to a saw such as a handsaw.

Fig.1 shows a conventional handsaw 10 which comprises a handle 11 and toothed blade 12. The blade 12 has teeth of constant pitch facing the tip of the saw 13.

Fig.2 illustrates the velocity-time relationship of the blade 2 during a cutting cycle. Inspection of Fig.2 shows that the velocity of the handsaw blade 12 changes non-linearly with respect to time.

Fig.3 shows a portion of a conventional reciprocating saw blade 15 provided with gaps 16 between adjacent groups of teeth 17 which assist the removal of sawdust from the cut.

The uniformly toothed blades described above have several disadvantages.

First, such blades are inefficient as in use the velocity of the blade varies non-linearly with respect to time whereas the cutting performance of the blade is optimal at one particular speed only for a given tooth pitch.

Generally teeth of a relatively large pitch are more efficient at high speeds than teeth of a small pitch and vice versa.

Second, during a cutting cycle such blades cut only whilst moving in one direction, i.e. in the direction in which the teeth are facing.

Third, handsaws having an elongate flexible uniformly toothed blade tend to flex unduly when the tip of the blade remote from the handle is in contact with the work at the onset of a cutting stroke. This flexure may result in the saw slipping laterally on the work. That particular disadvantage has been partially overcome by providing a rigid spine along the top edge of the blade, as for example in a tenon saw, to enhance the stiffness of the blade.

However, such spines cannot be applied to saws such as rip or cross-cut saws.

It is an object of the present invention to reduce the foregoing disadvantages.

According to one aspect of the invention there is provided a handsaw having an elongate blade and cutting teeth disposed along an edge thereof, in which a first set of teeth extending from a first end of the blade to a position substantially half way along the blade face the second end to cut a workpiece when the blade is moved in one direction and a second set of teeth extending from the second end to a position substantially half way along the blade face the first end to cut the workpice when the blade is moved in the opposite direction.

The handsaw may have a handle at one end.

The handsaw may have a neutral tooth adjacent the middle of the blade between the first and second sets of teeth which will cut in either direction, or there may be an untoothed edge adjacent the middle of the blade between said sets of teeth.

The teeth of a handsaw blade in accordance with the invention may be of varying pitch. It is preferred that the pitch of the teeth adjacent the ends of the blade is smaller than the pitch of the teeth adjacent the middle of the blade. The teeth may be arranged in groups along the length of the blade in which the teeth in a group have the same pitch.

According to another aspect of the invention there is provided a saw having an elongate blade the teeth being of varying pitch.

In either aspect the pitch of the teeth adjacent the ends of the blade may be smaller than the pitch of the teeth adjacent the middle of the blade.

The teeth may be arranged in groups, the teeth in a group having a constant pitch. In such a case, the teeth in groups adjacent the ends of the blade may have a smaller pitch than teeth in groups adjacent the middle of the blade.

In one embodiment teeth having a relatively smaller pitch are disposed adjacent the ends and middle of the blade and relatively larger pitched teeth are disposed between the teeth of smaller pitch.

Handsaws and blades in accordance with the invention will now be described with reference to the further figures in which: Fig.4 shows a handsaw having a blade in accordance with the invention.

Fig.5 shows a blade in accordance with the invention partly cut away.

Fig.6 shows an alternative blade in accordance with the invention.

Fig.7 shows a handsaw of the keyhole (or ox-tail) type, having a blade in accordance with the invention.

Fig.8 shows a handsaw of the hacksaw type having a blade in accordance with the invention.

Fig.9 shows a handsaw of the bucksaw type having a blade in accordance with the invention.

Figs.10-14 show handsaws having blades in accordance with the invention.

Fig. 15 shows a handsaw of the keyhold (or ox-tail) type having an alternative blade in accordance with the invention.

The handsaw 20 shown in Fig.4 comprises handle 21 and an elongate toothed blade 22 with tip 22a. A set of teeth 23 extending from the tip 22a to a position adjacent the middle of the blade face the handle 21 and a set of teeth 24 extending from the handle 21 to a position adjacent the middle of the blade face the tip 22a. A neutral tooth 25 is located between the sets of teeth 23 and 24 and will cut when the saw is used in either direction.

The pitch of teeth 23 decreases gradually towards the tip 22a. The pitch of teeth 24 decreases gradually towards the handle 21.

The handsaw 22 shown in Fig.4 has a num ber of advantages over conventional hand saws. In use, because the teeth 23 adjacent the tip 22a face the handle 21 they will slip over the work when commencing a forward cutting stroke and will not snag the work causing the blade to move laterally as was a problem with conventional handsaws. Ad ditionally, because the teeth 23 face the handle the blade will initially slip over the work during The handsaw 22 shown in Fig.4 has a number of advantages over conventional handsaws. In use, because the teeth 23 adja cent the tip 22a face the handle 21 they will slip over the work when commencing a for ward cutting stroke and will not snag the work causing the blade to move laterally as was a problem with conventional handsaws.

Additionally, because the teeth 23 face the handle the blade will initially slip over the work during a forward cutting stroke allowing the user to achieve a high-blade velocity before the teeth 24 cut the workpiece. The converse is true for the teeth 24 during a rearward cutting stroke. This enhances the efficiency of the cutting action. Furthermore, the pitch of the teeth along the blade varies to provide the optimum tooth pitch throughout the cutting cycle. It will also be appreciated that during a rearward cutting stroke the rearwardly facing teeth 23 will bite into the workpiece keeping the blade in tension and avoiding the lateral slipping of the blade which is common with conventional saws. Another advantage of handsaws in accordance with the invention is that in use the worker experiences equal forward and backward forces.Thus saws in accordance with the invention are considerably smoother in operation than conventional saws which minimises worker fatigue.

Fig.5 illustrates a blade 30 suitable for use with a hacksaw. The blade is provided with teeth 31 which are arranged similarly to the teeth of the handsaw 22 shown in Fig.24.

Fig.6 illustrates an alternative hacksaw blade 34 in which the teeth 35 arranged on one edge thereof, are disposed in groups of varying pitch (generally designated as A, B, C), the teeth within one group having a constant pitch. As apparent from Fig.6 the pitch increases step-wise towards the middle of the blade.

The keyhole (or ox-tail) type saw 40, shown in Fig.7 has a blade 41 with teeth arranged substantially the same as the teeth 31 on blade 22 shown in Fig.4.

Fig.8 shows a hacksaw 44 equipped with the hacksaw blade 30 shown in Fig.5.

Fig.9 shows a bucksaw 46 equipped with a blade 47 which is similar to the previously described blade 30.

Fig. 10 shows a handsaw 48 which differs from the saw 20 shown in Fig.4 in that the teeth 50 disposed along one edge of its blade 52 are of uniform pitch and an untoothed edge 51 is defined between the sets of teeth.

Fig. 11 shows a handsaw 54 having teeth arranged along one edge of its blade 55 like the handsaw 20 shown in Fig.4.

Fig. 12 shows a handsaw 56 in which the teeth 57 are arranged in groups D, E, F, G.

The teeth in each group are of uniform pitch and the pitch of the teeth increase stepwise towards the middle of the blade.

Fig.13 shows a handsaw 58 having teeth which vary in pitch along the length of the blade such that small pitch teeth 60 are disposed at the ends and middle of the blade 59 and large pitch teeth 61 are disposed between the teeth 60.

Fig.14 shows a handsaw 64 similar to that shown in Fig.13 except that the teeth 65 are disposed in groups along the length of its blade. As before, the teeth in each group are of uniform pitch.

The keyhole saw 68 shown in Fig.15 has teeth 69 of uniform pitch. The teeth 70 adjacent handle 71 face the tip 72 of the blade; the teeth 73 adjacent tip 72 face the handle 71.

The saws shown in Figs. 11 to 15 have an untoothed edge 51 between the forwardly and rearwardly facing teeth as in Fig.10.

Claims

1. A handsaw having an elongate blade and cutting teeth disposed along an edge thereof, in which teeth adjacent a first end face the second end to cut a workpiece when the blade is moved in one direction and teeth adjacent the second end face the first end to cut the workpiece when the blade is moved in the opposite direction.

2. A handsaw according to Claim 1 in which the blade has a handle at one end.

3. A handsaw according to Claim 1 or 2 which has a neutral tooth adjacent the middle of the blade.

4. A handsaw according to Claims 1 or 2 which has an untoothed edge adjacent the middle of the blade.

5. A handsaw according to any preceding claim in which the teeth are of varying pitch.

6. A handsaw according to Claim 5 in which the pitch of the teeth adjacent the ends of the blade is smaller than the pitch of the teeth adjacent the middle of the blade.

7. A handsaw according to Claim 5 or 6 in which the teeth are arranged in groups, the teeth in a group having a constant pitch.

8. A handsaw according to Claim 7 in which the teeth in groups adjacent the end, of the blade have a smaller pitch than teeth in groups adjacent the middle of the blade.

9. A handsaw according to any preceding claim in which teeth having a relatively smaller pitch are disposed adjacent the ends and middle of the blade and relatively larger pitched teeth are disposed between the teeth of smal ler pitch.

10. A saw having an elongate blade and cutting teeth disposed along an edge thereof, in which teeth adjacent a first end face the second end to cut a workpiece when the blade is moved in one direction and teeth adjacent the second end face the first end to cut the workpiece when the blade is moved in the opposite direction, the teeth being of varying pitch.

11. A saw according to Claim 10 in which the pitch of the teeth adjacent the ends of the blade is smaller than the pitch of the teeth adjacent the middle of the blade.

12. A saw according to Claim 10 or 11 in which the teeth are arranged in groups, the teeth in a group having a constant pitch.

13. A saw according to Claim 12 in which the teeth in groups adjacent the ends of the blade have a smaller pitch than teeth in groups adjacent the middle of the blade.

14. A saw according to any of the preceding claims in which teeth having a relatively smaller pitch are disposed adjacent the ends and middle of the blade and relatively larger pitched teeth are disposed between the teeth of smaller pitch.

15. A saw according to any of Claims 10 to 14 which has a neutral tooth adjacent the middle of the blade.

16. A saw according to any of Claims 10 to 14 which has an untoothed edge adjacent the middle of the blade.

17. A handsaw constructed and arranged substantially as described herein with reference to any of Figs. 4 to 15 of the accompanying drawings.