GB2231821A

GB2231821A - Producing watch casings

Info

Publication number: GB2231821A
Application number: GB8910121A
Authority: GB
Inventors: Sin-Bun Wong
Original assignee: WONG SIN BUN
Current assignee: WONG SIN BUN
Priority date: 1989-05-03
Filing date: 1989-05-03
Publication date: 1990-11-28
Anticipated expiration: 2009-05-03
Also published as: GB2231821B; GB8910121D0

Abstract

A watch case is formed from a solid body (12) of rock, stone or precious stone by ultrasonic machining. A support (16) connected to a vibration unit carries a head-piece (18) which acts on the block (13) in the presence of steel cutting particles and water. Each side of the block (13) is subjected to a separate machining step to form the watch case. <IMAGE>

Description

PROCESS FOR PRODUCING WATCH CASINGS The present invention relates to a process for producing watch casings from solid bodies of, for example, rock, stone or precious stone.

Conventional processes for producing rock or stone watch casings include lathe cutting, machine milling, machine shaping and hand carving. Hand carving is time consuming, labour intensive and does not provide a uniform standard of manufacture, whereas the other processes are not able conveniently to produce watch casings having shapes or patterns which are other than rectangular or circular.

The present invention seeks to provide a process for producing such watch casings, which process being capable of producing oddly shaped or patterned watch casings.

According to the invention, there is provided a process for producing a watch casing, which process comprises forming the watch casing from a solid body by ultrasonic drilling.

Prferably, the solid body is of rock or stone material.

It is preferred that the watch casing is produced by two ultrasonic drilling steps applied respectively to opposite sides of the solid body.

In a preferred embodiment, the ultrasonic drilling is carried out at a frequency in the region of 18-20kHz.

Other preferred and/or optional features of the invention will be apparent from the following description and the accompanying claims 5 to 7.

The invention also provides a watch casing which is produced by the process described above.

The invention further provides a watch including a watch case which is produced by the process described above.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows apparatus including an ultrasonic drilling machine for use in an embodiment of a process in accordance with the invention; Figures 2A to 2D are fragmentary partially sectional views of a part of the ultrasonic drilling machine of Figure 1, at various stages of the process; and Figure 3 is a sectional side view of a watch casing produced by the ultrasonic drilling machine of Figure 1 by means of the process.

Referring now to Figure 1 of the drawings, there is shown apparatus including an ultrasonic drilling machine 10 for use in an embodiment of a process in accordance with the invention. In this process a watch casing 11 (Figure 3) is produced by ultrasonic drilling from a tile 12 of hard and brittle material Ultrasonic drilling machines are generally known in the art, and they are generally used for forming decorative surface profiles on hard and brittle material surfaces.

The ultrasonic drilling machine 10 includes a control unit 13, a workpiece supporting platform 14, and a vibration unit 15 having a cutting head-piece support 16. The vibration unit 15 contains a plurality of tuning forks (not shown) which are connected directly to the cutting head-piece support 16, and are arranged to be energised by receiving a control signal from the control unit 13 to vibrate at an ultrasonic frequency of, in this particular embodiment, 18.8kHz. A cutting head-piece 18 is mounted on the support 16 by, say, welding. The vibration unit 15 is vertically slidable along a vertical rail 17, so that the vertical distance between the cutting head-piece 18 and the platform 14 can be adjusted. The workpiece supporting platform 14 is located in a basin 19 in which an inlet pipe 20 for steel cutting particles and a water inlet pipe 21 are provided, as hereinafter described.

Referring also to Figures 2A to 2D and Figure 3, the production of the watch casing 11 requires, in this instance, two ultrasonic cutting steps for respectively front and rear sides lla and llb. Accordingly, two cutting head-pieces 18 are required which are made of steel and whose cutting surfaces are formed complementary to the desired shape of the front and rear side lla and llb of the watch casing 11, respectively.

Figure 2A to 2D show the formation of the front side lla of the watch casing 11 in progression. The tile 12 is slightly thicker than the watch casing 11 and is placed on the workpiece supporting platform 14. The vibration unit 15 is moved downwards to bring the cutting head-piece 18 sufficiently close to the tile 12, as shown in Figure 2A. The workpiece supporting platform 14 is then lifted upwards to bring the tile 12 into contact with the cutting head-piece 18 (Figure 2B), and is biassed upwards by a pivoted weight (not shown) so as to provide a sufficient cutting force for the cutting head-piece 18.

The ultrasonic drilling machine 10 is switched on, and the cutting head-piece 18 vibrates at the frequency of 18.8kHz. At the same time cutting particles and water are introduced via the respective inlet pipes 20 and 21, both being directed to the interface between the cutting head-piece 18 and the tile 12. The cutting head-piece 18 vibrates both vertically and horizontally and therefore momentarily loses contact with the tile 12. This momentarily leaves a gap, whose size depends on the amplitude of vibration of the cutting head-piece 18 being just sufficiently large for the steel particles to be delivered by the water and to enter the gap between the cutting head-piece 18 and the tile 12, and for such particles to cut into the tile 12 when repeatedly urged by the cutting head-piece 18 against the tile 12.

The cutting head-piece 18 in combination with the steel particles acts as an abrasive head which cuts into the tile by scratching and grinding (as shown in Figure 2C), and eventually forms the front side lla of the watch casing 11 on the tile 12 (as shown in Figure 2D).

Superfluous steel particles and water are collected by the basin 19 and are then recycled for continuous use.

The rear side llb of the watch casing 11 is formed by another ultrasonic drilling step applied to the other side of the tile 12 by means of another cutting head-piece whose cutting surface has a shape complementary to that desired for said rear side.

To ensure that the rear side llb of the watch casing 11 is cut on the same centre as the front side lla, guide holes (not shown) are formed in unused peripheral portion 12' of the tile 12 during the first drilling step. The peripheral portion 12' is eventually cut away at the end of the second drilling step.

In this particular embodiment, steel particles of fineness index no. 100 is used, and is found to provide an acceptably smooth watch casing surface.

The finished watch casing 11 has a dial recess 22a, a watch-movement compartment 22b, and a central hole 22c connecting the recess 22a and the compartment 22b for a driving shaft of the musical movement. On the bottom of the watch-arm compartment 22a raised five-minute indicia (not shown) are formed which cannot conveniently be formed by known processes.

The invention has been described by way of example only, and various modifications and/or alterations may be made without departing from the scope of the invention.

Claims

1. A process for producing a watch case, which process comprises forming the watch casing from a solid body by ultrasonic drilling.

2. A process according to claim 1, wherein said solid body is of rock or stone material.

3. A process according to claim 1 or 2, wherein the watch casing is produced by a separate ultrasonic drilling step applied to each major side of said solid body.

4. A process according to claim 1, 2 or 3, wherein the ultrasonic drilling is carried out at a frequency in the range of 18kHz to 20kHz.

5. A process according to any one of the proceding claims, wherein the rock body is in the form of a tile.

6. A process for providing a watch case, substantially as hereinbefore.

7. A watch casing which is produced by a process as claimed in any one of the prceding claims.

8. A watch including a watch casing as claimed in claim 7.

9. A watch according to claim 8 and comprising a wrist watch.

10. The features hereinbefore disclosed, or their equivalents, in any novel selection.