GB2577692A - Method of production line teeth grinding of machine knives, machine used for implementing said method - Google Patents

Abstract

Grinding multiple equally spaced teeth in one pass on a blank metal strip for producing machine knives comprises clamping the blank metal strip in a first movable clamp, the indexing clamp, which is then advanced over a pre-programmed distance toward a datum stop and then closing a second clamp, the vice clamp, to fix the blank into position so that a grinding tool can pass over the work to produce multiple teeth in one pass, after which the indexing clamp releases the work and returns to its pre-programmed position to clamp a fresh part of the work and the vice clamp opens to allow the fresh part of the work to be moved into the correct position for grinding. A retractable datum cylinder may register the exact position of the blank strip for grinding. The grinding tool may be a multi wheel pack cutting between 6 and 50 teeth simultaneously. The blank may be a metal strip unrolled from a coil and recoiled after grinding.

Description

Method of production line teeth grinding of machine knives machine used for implementing said method.

Producing machine knives is a laborious process and takes up a lot of production time.

Moreover, these knives need to be highly accurate and with good control of the tooth pitch so that the blade can deliver a clean and regular cut.

Existing strip based knife production machinery starts with coils of sometimes pre-punched blank metal strip of spring steel -depending on what material the finished blade will have to cut -which is fed into a grinding machine.

The blank advances along a machine bed in a vertical position at more or less precise intervals, in a stepped manner so that the blank moves a distance of one tooth pitch with each step.

For each movement the machine advances the grinding wheel towards the work to grind the tooth and retracts it after completing the grind.

The indexing is normally done by a finger which pulls or pushes the blank forward for a predetermined distance, which determines the space between two neighbouring teeth or by press feeder.

Given the number of stops & starts, this is necessarily a slow and inaccurate process, exacerbated by frequent stops for resetting the grinding wheel.

The inventors set themselves the task of speeding this process up considerably by reducing the number of stops & starts and by increasing the rate of grinding.

To this end, they developed a process which starts with a blank presented substantially lying flat, close to horizontal, thus improving the ease of clamping it and of releasing it in a controlled manner.

The angle at which the blank is presented depends on the desired angle of the resulting cutting edge of the knife, which typically could be between 10 and 60 degrees to the horizontal.

In contrast to known methods, this inventive method achieves high efficiency by grinding several, up to 50 teeth, at a time before pausing for the blank to be pushed forward for the next grind position.

The blank may come coiled or in flat strips of more or less any desired length. Since the customer does not always want pre-cut machine knives, the preferred method is a coil to coil one, where the blank stock coil is mounted onto the machine, the blank fed through two successive clamps, either side of the machine bed, and recoiled at the other end of the machine.

In between the two clamps the blank is ground to produce the teeth by the grinding wheel in one or more passes, depending on the complexity of the grinding action. In the preferred process, the grinding is done in one single pass for each indexing step.

One of the two clamps, as mentioned above, is the vice clamp, which clamp holds the blank in the desired place, properly lined up with the grinding wheel.

The other clamp is the indexing clamp, which when closed will move the blank a pre-set distance for the next pass of the grinding wheel.

An alternative way of achieving accurate indexing is by moving the machine bed the required distance by means of a ball screw.

Statement of the invention

A method for grinding multiple equally spaced teeth in one index under a grinding tool on a machine tool comprising an angled machine bed, the method comprising the steps of clamping blank metal strip in a first movable clamp, the indexing clamp, which clamp then is advanced over a pre-programmed distance toward a datum stop and a second clamp, the vice clamp, which second clamp closes to fix the blank into position so that said grinding tool can pass over the work to produce the teeth, where after said indexing damp releases the work and returns to its pre-programmed position to close over a fresh part of the work, whereupon said vice clamp opens to allow said fresh piece of work being moved into the correct position for grinding.

The method will now be described with reference to the accompanying flow chart.

Not all the items described are shown on the flow chart, for ease of identification and to avoid the chart becoming overcrowded.

Stage 1 A coil of blank strip of suitable material is mounted on the machine and clamped by the index clamp. The index clamp is mounted on the machine bed in movable manner and will be driven by a linear actuator, itself controlled by the control unit consisting of a computer with a suitable program.

Stage 2 The index clamp is advanced toward the vice clamp along the product flow axis by means of the actuator over a distance determined by the computer program in the control unit.

Stage 3 The exact position of the blank strip in the grinding axis is determined and registered by a datum cylinder which enables that exact same position to be reproduced for the next cycle.

Stage 4 The vice clamp is closed holding the work in position ready for the grinding part of the process.

Stage 5 The datum cylinder is retracted and the grinding tool is lowered onto the work piece.

Stage 6 The grinding action finished the grinding tool retracts and the index clamp opens and returns to the cycle start position.

Stage 7 The index clamp closes on the fresh part of the work and the vice clamp opens.

Stage 8 The actuator advances the index clamp towards the open vice clamp up to the previously established datum position.

Stage 9 Vice clamp closes, index clamp opens and the actuator retracts and the process repeats from stage 6.

At stage 9 the flow chart illustrates the relative positions of various important elements of the machine enabling the execution of the method steps.

The block diagram shows two balers, one at each end of the machine bed, carrying the blank coil at the start end and the worked coil at the exit end of the machine.

The arrows show the direction of travel of the metal strip -the work blank -with the possibility of the index clamp of moving toward the vice clamp.

The grinding tool is shown positioned above the vice damp, from which position it can be lowered onto the work to do the grinding and lifted again after the grinding process is finished.

Claims (14)

1. Claims.1. A method for grinding multiple equally spaced teeth in one pass under a grinding tool on a machine tool comprising an angled machine bed, the method comprising the steps of clamping blank metal strip in a first movable clamp, the indexing clamp, which clamp then is advanced over a pre-programmed distance toward a datum stop and a second clamp, the vice clamp, which second clamp closes to fix the blank into position so that said grinding tool can pass over the work to produce the teeth, where after said indexing clamp releases the work and returns to its pre-programmed position to close over a fresh part of the work, whereupon said vice clamp opens to allow said fresh piece of work being moved into the correct position for grinding.
2. 2. A method for grinding multiple equally spaced teeth according to claim 1 whereby the position of the pre-programmed stop is determined by a suitable computer program.
3. 3. A method for grinding multiple equally spaced teeth according to claims 1 and 2 whereby said movement of said strip is achieved by a linear actuator.
4. 4. A method for grinding multiple equally spaced teeth according to claim I whereby said movement is achieved by moving the machine bed the required distance by means of a ball screw.
5. 5. A method for grinding multiple equally spaced teeth according to claim 2 whereby said strip advances over a distance sufficient for cutting 6 to 50 teeth in each grinding pass.
6. 6. A method for grinding multiple equally spaced teeth according to claim 3 whereby said linear actuator is controlled by said suitable computer program.
7. 7. A method for grinding multiple equally spaced teeth according to claim 1 whereby both said clamps are operated and controlled by said same suitable computer program.
8. 8. A method for grinding multiple equally spaced teeth according to claim 6 whereby said clamps are operated mechanically or hydraulically.
9. 9. A method for grinding multiple equally spaced teeth according to claim 1 whereby the grinding process is also controlled by said suitable computer program.
10. 10. A method for grinding multiple equally spaced teeth according to claim 1 whereby said grinding tool consists of a multi wheel pack, capable of grinding several teeth simultaneously.
11. 11. A method for grinding multiple equally spaced teeth according to any or all previous claims whereby the blank strip is supplied in coiled form, which coils are unrolled at the point of machining and recoiled after exiting the process.
12. 12. A method for grinding multiple equally spaced teeth according to claim 7 whereby said blank strip is presented lying generally flat, at between 10 and 60 degrees to the horizontal, on said machine bed and the grinding tool being lowered onto the blank strip for the production of the teeth.
13. 13. Machine for implementing the method elaborated in claims Ito 10
14. 14. Machine knife produced by means of the method according to claims 1 to 10 and on the machine according to claim I I.