WO1993001751A1

WO1993001751A1 - Saw blades

Info

Publication number: WO1993001751A1
Application number: PCT/GB1992/001281
Authority: WO
Inventors: Neville Rupert Mason Kay; Eric Clive Brookes
Original assignee: Hallamshire Surgical Saws Limited
Priority date: 1991-07-16
Filing date: 1992-07-14
Publication date: 1993-02-04
Also published as: GB9115362D0

Abstract

A surgical saw blade has two sets of teeth (12A, 12B) each tooth in profile having a front face (21) generally perpendicular to the direction of movement of the teeth, a back face (22) at between 30° and 40° to the front face, and an end face (23) at between 60° and 90° to the front face, with the front faces (21) in one set of teeth (12A) facing away from the front faces (21) in the other set of teeth (12B), and with curved roots (24) between adjacent back and front faces (22, 21) in each set of teeth and (24X) between the back faces of the adjacent pair of teeth (16A, 16B) from both sets (12A, 12B), whereby, while one set of teeth is cutting, the other set is facilitating clearance of swarf.

Description

SAW BLADES

This invention relates to saw blades, more particularly

- but not exclusively - for surgical or other bone saws of the type in which the blade is pivoted near one end and has teeth across the other end. the blade being oscillated through a small angle or reciprocated at high speed by a powered instrument, e.g., as used for orthopaedic surgery.

Human (or animal) bones are classed as "wet" or "dry" depending on their age and/or health, which influences the cleanness of the cut, clearance of swarf, and - to some extent

- the useful life of the blade.

Conventional bone saw blades are. made from stainless steel sheet (or thin plate) and have teeth of isosceles triangular form or similar in the plane of the sheet. Because of the oscillation through only a small angle, the teeth can be regarded as effectively reciprocating over a relatively short distance, so that swarf clearance is a problem. It is known, however, to provide a "set" on the teeth - as is usual with wood-working and metal-cutting saw blades - but this results in a wider cut and, more seriously, damage to the teeth and/or damage to metal templates or jigs, e.g., as used in total knee replacement procedures.

One object of the present invention is to provide oscillatory or reciprocatory saw blades with teeth formations that alleviate the aforementioned disadvantages.

According to the present invention, an oscillatory or reciprocatory saw blade is formed with at least two sets of teeth, each tooth in profile having a front face generally perpendicular to the direction of movement of the teeth, a o o back face at between 30 and 40 to the front face, and an end o o face at between 60 and 90 to the front face, with the front faces in one set of teeth facing away from the front faces in the other set of teeth, and with curved roots between adjacent back and front faces in each set of teeth and between the back faces of the adjacent pair of teeth from both sets. Thus, while one set of teeth is cutting, the other set is facilitating clearance of swarf.

Each set of teeth may consist of only two teeth, but more likely to be three, four or five teeth depending on the blade width, and the pair of adjacent teeth from both sets may merge to a lesser or greater extent, with corresponding variation of the depth of the root between these teeth (preferably a lesser depth) as compared with the depth of the roots between adjacent teeth in each set.

The root between adjacent teeth in each set is preferably radiussed tangentially to the respective front and back faces , to promote a smooth flow of swarf down the front face of the one tooth and out along the back face of the adjacent tooth.

In general, for ease of forming the teeth by grinding, punching or laser-cutting, the faces of the teeth will be perpendicular to the sides of the blade. However, it may prove advantageous for certain purposes for the teeth to be o inclined to the sides of the blade (e.g., at 30 to the perpendicular), as may be formed by grinding, e.g., after punching or laser-cutting; and the teeth may be inclined the same way in both sets or they may have the opposite inclination in one set from the other.

Again, while in general the enhanced clearance of swarf allows the teeth to lie wholly between the planes of the sides of the blade, it may be advantageous for certain purposes for the teeth to be "set" to provide side clearance.

Blades in accordance with the invention may be made from stainless steel sheet (or thin plate),^' and may be provided with narrow slits extending from the roots, to suppress harmful and/or noisesome vibrations. Alternatively, the blades may be made from suitable plastics or a ceramic material or from "hardmetal". The durability of the points of the teeth may be such that any one surgical bone saw blade has a practical life no greater than the duration of a single operation, so that for hygenic reasons it cannot be used again on a different patient.

The sides of stainless steel blades are preferably bead-blasted, and an equivalent matt finish provided on the sides of plastics, ceramic or "hardmetal" blades, to avoid distracting reflections when in use.

Preferred and optional features of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a front elevation of a surgical saw blade in accordance with the invention, shown actual size;

Figure 2 is a fragmentary elevation of the teeth of the blade of Figure 1, shown ten times actual size; Figure 3 is a further enlargement of two teeth from the left hand side of Figure 2, indicating the principal dimensions and angles;

Figure 4 is a fragmentary plan of the two teeth of

Figure 3;

Figure 5 is a fragmentary elevation showing an optional feature of the invention on the same scale as Figure

2;

Figure 6 is a plan of the teeth of Figure 5; Figures 7 and 8 correspond to Figure 6 but show two further optional features; and

Figure 9 corresponds to Figure 3 but shows yet another optional feature.

The surgical saw blade 10 shown in Figure 1 has a broader portion 11 at one end provided with two sets of teeth 12A, 12B (which will be described in more detail with reference to Figures 2 to 4), and a slot 13 and three holes 14 within a substantially circular portion 15 at the other end for engagement in a powered instrument (not shown) capable of oscillating the blade 10 at high speed through a small angle. It is to be understood that the portion 15 and its slot 13 and holes 14 are by way of example only, as being suitable for one particular make of powered instrument, and that various other formations can be utilized to suit other particular makes of powered instruments.

The formation of the teeth can be seen more clearly in Figure 2 and their dimensions and angles are indicated in Figure 3. Each tooth 16A, 17A etc, 16B, 17B etc, in each set 12A, 12B has a front face 21 generally perpendicular to the direction of movement of the teeth, a back face 22 at an o o angle ό between 30 and 40 to the front face, and an end face

Λ O O

23 at an angle^ between 60 'and 90 to the front face, with the front faces in one set 12A facing away from the front faces in the other set 12B, and with curved roots 24 between adjacent back and front faces 21, 22 in each set and between the back faces of the adjacent pair of teeth 16A, 16B from both sets.

Thus, while one set of teeth is cutting, the other set is facilitating clearance of swarf a smooth flow of which is promoted down the front face 21 of one tooth and out along the back face 22 of the adjacent tooth by having the root 24 therebetween radiussed tangentially to the respective front and back faces.

The root 24X between the back faces of the adjacent pair of teeth 16A, 16B from both sets has a lesser depth compared with the depth of the roots 24 between adjacent teeth in each set (to such an extent that the back faces 22 of those teeth 16A, 16B are nearly non-exist_* .t), so that the distance between the front faces 21 of those teeth 16A, 16B is substantially the same as the pitch P between adjacent teeth in each set 12A, 12B.

Preferred features of an oscillatory bone saw blade in accordance with the invention will now be described with particular reference to Figures 2 to 4, which blade is formed by laser-cutting from stainless steel having a thickness T of 0.60 m with a radius AR (see Figure 1) from the axis to the tips of the teeth of 74.00 mm, there being five teeth in each of the two sets 12A, 12B, with a pitch P in each set of 1.40 mm between front faces having a depth D of 0.60 mm, with roots

24 of 0.40 mm radius R blending tangentially into the adjacent front and back faces 21, 22 (and 24X into the back faces of the adjacent pair of teeth 16A, 16B from both sets), with the o back faces 22 at an angle o of 30 to the front faces 21, and o with end faces 23 of 0.20 mm length at an angle^ of 80 to the front faces, and all the faces being perpendicular to the sides 25X, 25T of the blade and lying wholly between the planes of the sides of the blades (see particularly Figure 4).

The distance between the front faces 21 of the teeth 16A, 16B is 1.50 mm.

Various optional features will now be described with reference to Figures 5 to 9.

In Figures 5 and 6 there are three teeth 16A, 17A, 18A and 16B, 17B, 18B in each set 12A, 12B having similar features to the corresponding teeth in Figures 2 to 4, but all the teeth are inclined the same way to the sides 25X, 25Y of the o blade at 30 to the perpendicular, while m Figure 7 the teeth

16B, 17B, 18B are similarly inclined the opposite way to the teeth 16A, 17A, 18A.

In Fiσure 8, again with three teeth in each set, the teeth 17A, 16B, 13B are "set" one way (i.e., slightly beyond the side 25X of the blade) while the teeth 18A, 16A, 17B are

•ι_setιι _{the ot}h_er way (i.e. slightly beyond the side 25Y of the blade) to afford added clearance. In Figure 9 narrow slits 26 (0.010 mm wide) extend from the roots 24 in line with the back faces 22 of the teeth, to supress harmful and/or noisesome vibrations.

Claims

1. An oscillatory or reciprocatory saw blade formed with at least two sets of teeth, each tooth in profile having a front face generally perpendicular to the direction of o o movement of the teeth, a back face at between 30 and 40 to o o the front face, and an end face at between 60 and 90 to the front face, with the front faces in one set of teeth facing away from the front faces in the other set of teeth, and with curved roots between adjacent- back and front faces in each set of teeth and between the back faces of the adjacent pair of teeth from both sets.

2. A saw blade as in Claim 1, wherein the root between adjacent teeth in each set is radiussed tangentially to the respective front and back faces.

3. A saw blade as in Claim 1 or Claim 2, wherein the faces of the teeth are perpendicular to the sides of the blade.

4. A saw blade as in Claim 1 or Claim 2, wherein the teeth are inclined to the sides of the blade.

5. A saw blade as in Claim 4, wherein the teeth are inclined the same way in both sets.

6. A saw blade as in Claim 4, wherein the teeth have the opposite inclination in one set from the other.

7. A saw blade as in any one of the preceding Claims, wherein the teeth lie wholly between the planes of the sides of the blade.

8. A saw blade as in any one of Claims 1 to 6, wherein the teeth are "set" to provide side clearance.

9. A saw blade as in any one of the preceding Claims made from stainless steel sheet.

10. A saw blade as in Claim 9, wherein narrow slits extend from the roots.

11. A saw blade as in Claim 9 or Claim 10, wherein the sides of the blade are bead-blasted to a matt finish.

12. A saw blade as in any one of Claims 1 to 8 made from plastics or ceramic material or from "hardmetal".

13. A saw blade as in Claim 12, wherein the sides of the blade are provided with a matt finish.

14. A saw blade as in Claim 1 and having sets of teeth substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.

15. A saw blade as in Claim 14 modified as in Figures 5 and 6 or any one of Figures 7, 8 and 9 of the accompanying drawings.