GB2386333A

GB2386333A - Apparatus for the manufacture of bandsaw blades or the like

Info

Publication number: GB2386333A
Application number: GB0206213A
Authority: GB
Inventors: Ian Michael Bufton
Original assignee: SOAG MACHINERY Ltd
Current assignee: SOAG MACHINERY Ltd
Priority date: 2002-03-15
Filing date: 2002-03-15
Publication date: 2003-09-17
Anticipated expiration: 2022-03-15
Also published as: GB2386333B; GB0206213D0

Abstract

Apparatus for the manufacture of bandsaw blades by cutting teeth in a plurality of blanks stacked side by side with a grinding wheel arranged at a rake angle and having a transverse cutting path extending in the stack width direction. The apparatus may also include a stack support structure with a registration element, and retractable registration hammers to align the blanks at the cutting location in order to minimise bending stresses. The profile of teeth formed by the grinding wheel may be varied by reciprocating the grinding wheel in a blank length direction.

Description

METHOD AND APPARATUS FOR THE MANUFACTURE OF BANDSAW

BLADES AND OTHER ELONGATED TOOTH ELEMENTS

This invention relates to a method and an apparatus for the manufacture of bandsaw blades and other elongated tooth elements by cutting teeth with a grinding wheel.

Bandsaw blades are consumed in large quantities within a variety of 5 manufacturing and processing operations. It is, accordingly, desirable for apparatus to be available which capable of manufacturing bandsaw blades with a high throughput.

A conventional technique for the manufacture of bandsaw blades involves the clamping of a stack of perhaps up to 20 strip blanks at a time and the 10 repeated plunging of a grinding wheel into the stack at repeated distances along the length of the stack. In this approach, the number of blanks that can be accommodated in one stack is limited (as will be described in more detail later in this specification) by the radius of the cutting wheel. This limit on a number of

blanks within one stack, considerably restricts the throughput of the machine.

15 It is also the case that the geometry of the cutting wheel in the prior art

arrangement and the way that it is plunged into the stack of blanks, can produce variations in tooth profile, from one blank to the next in the stack. This lack of uniformity within the manufacture of band saw blades can significantly reduce the efficiency of the eventual bandsaw operation.

20 It is an object of certain aspects of the present invention to provide an improved method and apparatus for the manufacture of bandsaw blades and other elongated tooth elements which is capable of higher throughput.

Accordingly, the present invention consists in one aspect in an apparatus for the manufacture of bandsaw blades and other elongate toothed elements by 25 cutting teeth in a blank which extends in a blank length direction with the cut teeth extending in a tooth direction orthogonal to the blank length direction, the apparatus comprising a stack support structure for supporting a stack of parallel blanks stacked side-by-side in a stack width direction orthogonal to the blank length direction and to the tooth direction; a grinding wheel mounted for driven 30 rotation about a grinding wheel axis which lies in a plane containing the blank

length direction and the tooth direction and is inclined at a rake angle to the blank length direction; a cutting drive for effecting relative movement between the grinding wheel and the stack in a cutting path extending in the stack width direction to cut a set of teeth in the respective blanks of the stack; and an 5 indexing drive for effecting relative movement between the grinding wheel and the stack in an indexing path extending in the blank direction.

By arranging for the cutting path of the grinding wheel to extend in the stack width direction, the variability in tooth profile across the stack width is considerably reduced, if not removed. It is possible to form considerably larger 10 stacks than with the described prior art approach. The further advantage is

secured in that the variability in tooth profile from one blade to the next, is significantly reduced.

To ensure accurate formation of teeth, it is necessary for the blanks to be aligned with high accuracy prior to the cutting operation. Prior art arrangements

15 have suggested the use of clamps alongside the grinding wheel which served to register or align the blanks. In order to avoid interference with the grinding wheel, these clamps are necessarily spaced apart. They, accordingly, have a tendency to impose unwanted bending stresses on the blanks and on the apparatus itself.

It is an object of another aspect of the present invention to provide for 20 registration of cutting blanks in a way which does not impose unnecessary stress.

Accordingly, the present invention consists in another aspect in an apparatus for the manufacture of bandsaw blades and other elongate toothed elements by cutting teeth in a blank which extends in a blank length direction with the cut teeth extending in a tooth direction orthogonal to the blank length 25 direction, the apparatus comprising a stack support structure for supporting a stack of parallel blanks stacked side-by-side in a stack width direction orthogonal to the blank length direction and to the tooth direction; a grinding wheel mounted at a grinding location and movable relative to the stack in a cutting path to cut a set of teeth in the respective blanks of the stack; a grinding clamp actuable to 30 clamp the blanks at the grinding location; a registration element serving to register the blanks in the tooth direction at the grinding location and one or more registration hammers located at the grinding location, the registration hammers being actuable within the cutting path to urge the blanks toward the registration element and retractable from the cutting path to permit cutting of teeth by the

grinding wheel.

As the registration hammer is located at the grinding location, it serves to urge the blanks into registration with minimum stress on the blanks and on the overall structure. Interference with the grinding wheel is then avoided by retraction 5 of the registration hammer from the cutting path.

Further preferred embodiments utilise a combination of some or all of the features described in the aforementioned embodiments.

An embodiment will now be described by way of an example with reference to the accompanying drawings in which: 10 Figure 1 shows a partially machined blank stack and local reference directions Figure 2 is an end view of a simple plunge grinding wheel engaged with a blank stack Figure 3 shows an end view of a grinding apparatus and a blank stack 15 according to an embodiment of the present invention.

Figure 4 shows schematically a side view of a grinding apparatus and a blank stack according to an embodiment of the present invention.

Figure 5 is an enlarged view of possible wheelforms and tooth profiles.

Figure 6 is a schematic diagram to illustrate the effects of reciprocating the 20 grinding wheel.

Figure 7 is a simplified view of an apparatus arranged to manufacture bandsaw blades according to an embodiment of the present invention Figure 8 is a simplified view of a vice assembly according to a preferred embodiment of the present invention.

25 Referring to Figure 1, there is shown a partially machined blank stack. The individual blade blanks 102 are stacked side by side in a stack width direction 104 to form a stack which extends in a blank length direction 106, with the cut teeth extending in a tooth direction 108.

In Figure 2, a simple plunge cutting grinding wheel 202 is shown engaged 30 in a blank stack 204 according to a prior art arrangement. The blanks in the

central region 206 of the stack will be cut approximately square, and to approximately the same depth in the tooth direction, indicated by numeral 208.

On account of the curvature of the grinding wheel however, blanks located near the ends of the stack in regions 210 will be cut obliquely, and to a lesser depth,

with the maximum deviation in cutting depth 212 occurring at the extreme blanks 214 and 216. in this way it can be seen that for a simple plunge cutting device, there is a limit to the stack width dimension which can be cut uniformly, for a given radius of grinding wheel.

5 Figure 3 shows an end view of a grinding wheel 302 and a blank stack 304 according to an embodiment of the present invention. The grinding wheel 302 can be traversed along a cutting path (illustrated by numeral 304) extending in the stack width direction. This traversing movement allows the grinding wheel, to make an oblique cut of constant depth across the whole blank stack, and thus a 10 wider blank stack can be used than would otherwise have been possible to manufacture a substantially uniform set of toothed blades for a given radius of grinding wheel.

Figure 4 shows a side profile of a grinding wheel 402, drive means 404 and a blank stack 406 according to an embodiment of the present invention. The drive 15 means 404 rotates the grinding wheel 402 about its axis 408, which is inclined at a rake angle (indicated by numeral 410) to the blank length direction 412. The grinding wheel can be traversed relative to the blank stack along a path 414 in the tooth direction, as part of a return mechanism for example, and along a path in the blank length direction 416 for example in an indexing movement.

20 The grinding wheel 402 is of frusto-conical form so that, with its axis 408 inclined to the blank length direction 412, the grinding surface 420 is presented generally parallel to the surface of the blank stack 406. The orientation of the grinding wheel 402 and its paths of movement facilitate the use of a continuous grinding wheel dresser as shown schematically at 403.

25 Figure 5a shows a standard wheelform with cutting surface profile 502 extending substantially along the whole wheelform, for cutting a set of teeth into a blank stack in a single pass.

Figure 5b shows a modified wheelform wherein protruding cutting surfaces 504 are interleaved with spacing sections 506, whereby only one face of each 30 tooth is formed in a single pass. In order to complete the set of teeth, the grinding wheel must be indexed by approximately half of the tooth pitch 508 in the blade length direction, and another cutting pass made. This method allows the teeth to be cut more sharply than the internal dimensions of the grinding wheel.

Figure 5c shows one possible tooth profile which may be cut using

apparatus according to the present invention. On account of the shape of the grinding wheel and the rake angle of its axis, the leading edge of the teeth can be cut at an attacking angle indicated by numeral 510 Figure 6 illustrates how the tooth profile cut by a given grinding wheel may 5 be varied using relative reciprocation between the grinding wheel and the blank stack in the blank length direction 602. On account of this reciprocation, each protruding cutting surface 604 effectively sweeps a greater area 606 (shown broken line) during a cuffing pass. The size of the teeth cut may be varied according to the amplitude of vibration of the grinding wheel, and in this way the 10 tooth profile may be varied for each cutting pass thus producing, using a single grinding wheel, bandsaw blades with varying tooth profiles. This method of reciprocation may be used for a wide range of wheelforms. A smaller amplitude reciprocation may be useful in removing burr or flash, without substantially modifying the tooth profiles.

15 Referring now to Figure 7, an elongate blank stack 702 extends between two end clamps 704, 706. Located between end clamps 704, 706, is a vice assembly 708, through which blank stack 702 also passes. Vice assembly 708 is slidably mounted to a vice bed 710 via rails 712. A grinding wheel 714 and associated drive apparatus 716 are located adjacent to the vice assembly 708.

20 The grinding wheel 714 can be traversed in both the tooth direction 718 and in the stack width direction 720. Teeth are cut along the length of an elongate blank by performing the following sequence of operations: The blank stack is constrained locally by the vice assembly while the grinding wheel performs a downwards cutting pass through the edge of the blanks 25 to be machined. The end clamps then close on the blank stack to constrain it while the vice assembly releases from the stack and indexes along the vice bed in the blank length direction. The vice then closes, constraining the blank at the next section to be machined. The end clamps are released, and the vice returns to its initial position on the vice bed, advancing the blank stack as it does so. The 30 grinding wheel then travels along a return path, moving around the blank stack to its initial position above the stack, ready to perform another downwards cutting pass. In this way the blank stack remains constrained by either the vice assembly or the end clamps at all times during continuous machining.

As described previously, the blank stack may be reciprocated in the blank

length direction relative to the grinding wheel during the cutting pass, in order to achieve a desired tooth profile. In this case it is ensured that the end clamps are not engaged during the cutting pass. Also as mentioned, the amplitude of vibration may be varied from one cutting pass to the next, to achieve a variable 5 tooth profile along the blank length.

Figure 8, which is a simplified view of a vice assembly, shows a channel defined by a base block 802, a registration plate 804, and a top jaw 806 moveable along a vertical clamp cylinder 810. Two packing or registration hammers 812, 814 are rotatably and slidably mounted to the base block via two 10 shafts 816, and when not active, can be 'parked' in housings 818. Hammer 812 is shown in the active position, and hammer 814 is shown parked. The housings 816 are sufficiently deep to allow the parked hammers to be retracted fully behind the front face 818 of the base block 802.

A blank stack can be fed through the above mentioned channel, and when activated, the packing hammers move to the active position and force the blank stack into alignment against the back plate 804. The hammers may act directly on the region of the blank stack to be machined, since they can subsequently be retracted, out of the way, to the parked position. In use, the packing hammers are engaged after the vice assembly has indexed along the blank length direction, 20 before the vice is closed on the stack. Thus any misalignment in the tooth direction of one or more of the blanks in the stack occurring during the motion of the vice relative to the stack can be corrected, and the stack realigned, before the vice re- engages.

It will be understood that the order or direction of many of the process 25 types described above can be easily altered.

Whilst the example has been taken of bandsaw blade manufacture, it will be understood that the invention will find application in the manufacture of other forms of blades or other toothed elements such as gear racks. The invention has 33 been described by way of example only and a wide variety of further modifications are possible without departing from the scope of the appended claims.

Claims

1. Apparatus for the manufacture of bandsaw blades and other elongate toothed elements by cutting teeth in a blank which extends in a blank length direction with the cut teeth extending in a tooth direction orthogonal to the blank length direction, the apparatus comprising a stack support structure for supporting a stack of parallel blanks stacked side-by-side in a stack width direction orthogonal to the blank length direction and to the tooth direction; a grinding wheel mounted for driven rotation about a grinding wheel axis which lies in a plane containing the blank length direction and the tooth direction and is inclined at a rake angle to the blank length direction; a cutting drive for effecting relative movement between the grinding wheel and the stack in a cutting path extending in the stack width direction to cut a set of teeth in the respective blanks of the stack; and an indexing drive for effecting relative movement between the grinding wheel and the stack in an indexing path extending in the blank direction.

2. Apparatus according to Claim 1, wherein the grinding wheel is of frusto-

conical form so as to present in said plane a cutting profile which is generally parallel with the blank length direction.

3. Apparatus according to Claim 1 or Claim 2, wherein there is further provided a grinding wheel dresser serving to provide substantially continuous dressing of the grinding wheel.

4. Apparatus according to Claim 1, wherein there is further provided a reciprocating drive for effecting relative reciprocation between the grinding wheel and the stack along a reciprocation path extending a distance in the blank length direction which is small compared with the extent of each tooth in the blank length direction.

5. Apparatus according to any previous claim, wherein the stack support

structure comprises a central vice assembly, slidable in the blank length direction, and one or more end clamps through which the elongate blank stack passes; said end clamps capable of constraining the blank stack in the blank length direction during relative indexing movement between the vice assembly and the stack.

6. Apparatus according to any previous claim, further comprising registration means acting on the blanks at the grinding location and capable of aligning the blanks in the tooth direction.

7. A method of manufacturing bandsaw blades and other elongate toothed elements by cutting teeth in a blank which extends in a blank length direction with the cut teeth extending in a tooth direction orthogonal to the blank length direction, the method comprising the steps of forming a stack of parallel blanks stacked side-by-side in a stack width direction orthogonal to the blank length direction and to the tooth direction; effecting relative movement between the stack and a grinding wheel in a cutting path extending in the stack width direction to cut a set of teeth in the respective blanks of the stack, the grinding wheel being orientated to present a tooth cutting profile which is raked with respect to the blank length direction; and effecting relative movement between the grinding wheel and the stack in an indexing path extending in the blank direction to present fresh blank portions for the cutting of successive sets of teeth.

8. A method according to Claim 7, comprising the further step of dressing the grinding wheel for the cutting of each set of teeth.

9. A method according to Claim 7 or Claim 8, wherein the stack is indexed in the blade length direction according to the following steps: constraining the blank stack by clamping at a location remote from the grinding wheel; indexing a central clamping means in the blank length direction; clamping the stack with the central clamping means, constraining the stack

relative to the central clamping means at a fresh blank portion; releasing the blan.k stack from said remote clamping; returning the central clamping means in the blank length direction, thus advancing the blank stack simultaneously.

10. A method according to any one of Claims 7 to 9, further comprising aligning the blanks at the grinding location in the tooth direction, prior to each cutting pass of the grinding wheel.

11. Apparatus for the manufacture of bandsaw blades and other elongate toothed elements by cutting teeth in a blank which extends in a blank length direction with the cut teeth extending in a tooth direction orthogonal to the blank length direction, the apparatus comprising a stack support structure for supporting a stack of parallel blanks stacked side-by-

side in a stack width direction orthogonal to the blank length direction and to the tooth direction; a grinding wheel mounted at a grinding location and movable relative to the stack in a cutting path to cut a set of teeth in the respective blanks of the stack; a grinding clamp actuable to clamp the blanks at the grinding location; a registration element serving to register the blanks in the tooth direction at the grinding location and one or more registration hammers located at the grinding location, the registration hammers being actuable within the cutting path to urge the blanks toward the registration element and retractable from the cutting path to permit cutting of teeth by the grinding wheel.

12. Apparatus according to Claim 11, wherein said one or more registration hammers are mounted slidably in the tooth direction and rotatably about an axis in the tooth direction to allow both tamping of the stack and retraction from the cutting path.

13. Apparatus according to Claim 1 1 or Claim 12, wherein said one or more registration hammers, when not in use, are fully retractable behind the plane swept by the leading edge of the grinding wheel during a cutting pass, in a direction away from the grinding wheel.

14. Apparatus according to any one of Claims 1 1 to 13, comprising two registration hammers.