WO2008032152A1

WO2008032152A1 - High-speed rotary diamond cutting machine

Info

Publication number: WO2008032152A1
Application number: PCT/IB2007/002423
Authority: WO
Inventors: Carl Helmuth Deckert
Original assignee: Scheffer, Cornelius; Wegner, Emile
Priority date: 2006-09-11
Filing date: 2007-08-23
Publication date: 2008-03-20

Abstract

A rotary diamond cutting machine (1) is provided comprising a base (2) supporting a rotatable driven shaft (4) by way of at least one bearing (5) and wherein the shaft has a flange assembly (8) for mounting a working disc (9) thereto so as to be driven in unison with the shaft. The shaft is collinear with a rotor (10, 18) of a prime mover that is to impart rotary motive power to operatively drive the shaft and is either secured directly to the driven shaft will coupled thereto by way of a coupling, typically a magnetic coupling. The rotor may be a fluid, typically air, driven turbine (10) in which instance it preferably has an endless series of pockets (11) formed in an outer cylindrical surface thereof and into which a jet of compressed air can be directed. Alternatively, the rotor (18) may be that of an induction or brushless electric motor. Preferably, the machine has a single central bearing (5) that is conveniently an air bearing.

Description

HIGH-SPEED ROTARY DIAMOND CUTTING MACHINE

FIELD OF THE INVENTION

This invention relates to a high-speed rotary diamond cutting machine which term is intended to include both sawing machines used for dividing a rough diamond into two or more parts and polishing machines used for polishing facets on a stone during the composite cutting procedure.

It will be understood that the expression diamond cutting machine, as well as the term diamond, are used herein for the purpose of communicating the area of technology concerned. Accordingly, these terms are not to be interpreted as limiting the scope of this invention in any way. Thus, machines with which this invention is concerned may be used for the purpose of cutting any other appropriate precious or semiprecious gemstones as well as very hard items such as industrial elements, in particular, industrial diamonds.

BACKGROUND TO THE INVENTION

Diamond sawing machines that are presently used for the purpose of dividing a rough diamond into two or more parts fall basically into two different categories, namely, the traditional rotary sawing machines, and state-of-the- art laser cutting machines.

Traditional rotary sawing machines that have been used for more than a hundred years employ a thin phosphor bronze disc firmly clamped between two metal flanges on a high-speed driven shaft. The phosphor bronze disc is impregnated with diamond dust as a cutting agent and the centrifugal force holds the otherwise relatively flexible disc in an effectively rigid condition. Little technological advancement, if any, has been made over the years. This sawing machine, whilst being relatively inexpensive, suffers from a number of disadvantages. Firstly, these rotary sawing machines generally have a belt drive that is in turn driven by an electric motor by way of a drive shaft that is typically common to a number of aligned sawing machines, typically of the order of about five. The belt drive limits the speed at which the disc can be driven and this in turn results in the disc deviating on occasions from the required path with a consequent increase in loss of diamond. Typically, rotational speeds that can be achieved utilising such a belt drive mechanism is about 7500 rpm.

Furthermore, the arrangement of a belt drive in the conventional manner is a source of vibration that is often unacceptable. Considerable cost is invariably involved in avoiding such vibration, typically by the provision of concrete tables on which the cutting machines are mounted.

Also, in the event that a hard spot or change in cleavage planes in the crystalline structure is encountered in a diamond being cut, the disc may jam thereby possibly resulting in a burning out of the drive motor with resultant downtime and maintenance being necessary. In any event, in any instance in which the disc jams, which is generally occasioned by a deviation from the desired path in which the disc is required to cut, the direction of rotation of disc is usually reversed in order to combat the relevant hard spot or change in crystalline structure.

On the other hand, state-of-the-art laser cutting machines are extremely costly when compared to the cost of the rotary sawing machines. Added to this is the disadvantage that, where flaws are present, the heat generated by the laser can cause further damage to the diamond being cut, this being particularly relevant in the case of industrial quality diamonds. Heavy losses can result. Also, in the case of the prior art, completely separate polishing machines having relatively large diameter horizontal polishing discs are employed for polishing facets on a diamond following sawing and bruting thereof.

OBJECT OF THE INVENTION

It is an object of this invention to provide a high-speed rotary diamond cutting machine that can be operated at higher rotational speeds, or with less vibration, or both.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a rotary diamond cutting machine comprising a base supporting a rotatable driven shaft by way of at least one bearing and wherein the shaft has a flange assembly for mounting a working disc thereto so as to be driven in unison with the shaft, the diamond cutting machine being characterised in that a rotor of a prime mover that is to impart rotary motive power to the driven shaft is arranged coaxially with the driven shaft and is coupled thereto either directly or by way of an in line coupling.

Further features of the invention provide for the rotor to be selected from a fluid driven turbine and windings of an induction or brushless electric motor; for the driven shaft to be generally horizontal in the operative orientation; for the diamond cutting machine to have a single central bearing in which instance the flange assembly for mounting a working disc thereto is positioned on one side thereof and the rotor on the other side thereof and wherein the rotor and may optionally be secured directly to the drive shaft; in the alternative for the rotor to be coupled to the driven shaft by way of a coupling, in particular a magnetic coupling in which instance the rotor has its own bearing; for the bearing supporting the driven shaft to be an air bearing; and, in the instance that the rotor is a turbine, for the turbine to be an air turbine adapted to be operated by means of compressed air and preferably being of the type in which an endless series of pockets is formed in an outer cylindrical surface of the turbine and into which a jet of compressed air can be directed, the turbine conveniently having the general nature of a Terry turbine.

The working disc, for cutting purposes, will generally be a phosphor bronze disc of the type commonly used in the art. However, it is envisaged that the working disc could be a polishing disc presenting a cylindrical peripheral surface that can be used for polishing purposes. In the instance that a flat facet is to be polished on a stone, the stone itself will be supported in a rotatable manner so that a flat face can be polished using a straight line of contact with the cylindrical surface. However, the cylindrical surface provides an additional facility for polishing arcuate surfaces on a stone as well.

Of course, in small operations, the same cutting machine can be used selectively for both purposes simply by exchanging the phosphor bronze cutting disc for a polishing wheel, and vice versa, as may be required.

It is envisaged that by use of a suitable air bearing and rotor combination extremely high speeds of rotation can be achieved that are upwards of 10,000 rpm and it is envisaged will easily be in the range of 15,000 rpm to 20,000 rpm and possibly even higher. It is envisaged that the use of such high speeds of rotation will obviate, at least to a large extent, the difficulties occasioned by encountering a hard spot or change in cleavage planes in the crystalline structure of a diamond. Also, an arrangement according to this invention should have no, or no significant, vibration associated with it.

It is accordingly also envisaged that it may well be possible for the cutting machine to have a single direction of rotation in the event that jamming is substantially obviated by the use of such high speeds of rotation. However, it is also within the scope of this invention that the rotor be provided with a facility for enabling it to be driven selectively in either angular direction and, in the event that the rotor is a turbine having an endless series of pockets, as indicated above, two oppositely directed juxtaposed series of pockets could be provided in a cylindrical surface thereof.

In the alternative, in the event that the rotor is that of an electric motor, it is envisaged that modern-day high speed electronic switching will enable satisfactorily high speeds of rotation to be achieved without the use of any of the conventional gearing achieved using large and small diameter pulleys, for example.

In order that the invention may be more fully understood two slightly different embodiments thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a perspective view from one side of one embodiment of diamond cutting machine according to the invention with the turbine in exploded relationship relative thereto for illustrative purposes;

Figure 2 is a perspective view from the opposite side thereof;

Figure 3 is a front elevation thereof with the turbine housing and associated nozzles removed for illustrative purposes;

Figure 4 is an end elevation of the machine;

Figure 5 is an enlarged sectional elevation thereof; W

Figure 6 is a plan view thereof;

Figure 7 is a view similar to Figure 3 illustrating a turbine that has two oppositely directed series of pockets to enable reversible rotation to be applied thereto;

Figure 8 is a sectional schematic elevation similar to Figure 5 of a second embodiment of the invention in which the prime mover is an electric motor; and,

Figure 9 is a sectional schematic elevation similar to Figure 5 of a second embodiment of the invention in which a coupling is interposed between the prime mover and the driven shaft.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention illustrated in Figures 1 to 6, a rotary diamond cutting machine, generally indicated by numeral (1), comprises a base (2) having a baseplate (3) for securing it to a worktop or the like. The base supports a horizontal rotatable driven shaft (4) by way of a single air bearing (5) that is of generally elongate shape so as to provide required stability to the driven shaft when it is rotated at high-speed. The air bearing is operatively fed with air under pressure by way of a plurality of radially and axially spaced air inlets (6) communicating with an air reservoir (7) formed5 within the base.

One end of the shaft has a flange assembly (8) for mounting a working disc (9), in this instance a phosphor bronze cutting disc. 0 The other end of the shaft has a turbine (10) secured to it. In tests conducted to date a Terry type of turbine has been employed although it appears that alternative turbine types may provide better results. The turbine has an endless series of pockets (11) formed in its outer cylindrical surface that are to receive a jet of compressed air that emanates from constricted nozzles (12) formed in a turbine cover (13). In this embodiment of the invention there are two diametrically opposite constricted nozzles (12) that are fed by way of inlets (15) provided in the turbine cover. The turbine may be coated with it special hardened coating of a suitable type.

An air inlet (16) to the base supplies compressed air to the air reservoir (7).

The entire flange assembly, turbine, and shaft are thus rotatable in unison, in use, relative to the base and turbine cover.

As indicated above, it is envisaged that speeds of rotation that are upwards of 10,000 rpm and more typically in the range of 15,000 rpm to 20,000 rpm will easily be achieved utilising a machine as described above. As indicated, at such speeds it may well not be necessary to provide for the direction of rotation to be reversible.

However, in the event that reversibility is required, for any reason, the turbine may be provided with two oppositely directed endless series of pockets (17) in an outer cylindrical surface thereof, as illustrated in Figure 7.

As indicated above, it is envisaged that the working disc could be replaced by a polishing disc to provide for polishing facilities utilising a single machine.

In a second embodiment of the invention that is illustrated in Figure 8, the arrangement is substantially identical to that described above except that the turbine and cover are replaced by components including windings of an induction or brushless electric motor that create a rotor (18) of an electric motor and that forms its part of the rotatable shaft assembly and a stator (19) that is fixed to the baseplate (20) and that includes cooperating windings of an induction or brushless electric motor. By employing suitable electronic switching means indicated by numeral (21) it is envisaged that high rotational speeds will be achieved thereby resulting in the advantages indicated above.

In both of the embodiments of the invention described above, the rotor is directly secured to the driven shaft. However, it is within the scope of this invention, that a coupling (22) can be interposed between the rotor (23) and the driven shaft (24), as illustrated in Figure 9. Such a coupling is preferably a non-contact coupling such as a magnetic coupling that utilizes permanent magnets, electromagnets, or magnetism created by any Eddy currents. However, it is also envisaged, that certain types of fluid couplings may operate effectively.

It will be understood that numerous variations may be made to the embodiments of the invention described above without departing from the scope hereof. In particular, it is envisaged that the turbine could be hydraulically driven although it is appreciated that a source of suitable hydraulic fluid under pressure may be considerably more costly than a source of compressed air.

Claims

CLAIMS:

1. A rotary diamond cutting machine (1) comprising a base (2) supporting a rotatable driven shaft (4) by way of at least one bearing (5) and wherein the shaft has a flange assembly (8) for mounting a working disc

(9) thereto so as to be driven in unison with the shaft, the diamond cutting machine being characterised in that a rotor (10, 18,23) of a prime mover that is to impart rotary motive power to the driven shaft is arranged coaxially with the driven shaft and is coupled thereto either directly or by way of an in line coupling (22).

2. A rotary diamond cutting machine as claimed in claim 1 in which the rotor is a fluid driven turbine (10).

3. A rotary diamond cutting machine as claimed in claim 2 in which the turbine is an air turbine adapted to be operated by means of compressed air.

4. A rotary diamond cutting machine as claimed in claim 3 in which of the type in which the turbine has an endless series of pockets (11) formed in an outer cylindrical surface thereof and into which a jet of compressed air can be directed.

5. A rotary diamond cutting machine as claimed in claim 1 in which the rotor (18) is that of an induction or brushless electric motor.

6. A rotary diamond cutting machine as claimed in any one of the preceding claims in which for the driven shaft is generally horizontal in the operative orientation.

7. A rotary diamond cutting machine as claimed in any one of the preceding claims in which the diamond cutting machine has a single central bearing (5) in which instance the flange assembly for mounting a working disc thereto is positioned on one side thereof and the rotor on the other side thereof.

8. A rotary diamond cutting machine as claimed in claim 7 in which the bearing is an air bearing.

9. A rotary diamond cutting machine as claimed in any one of the preceding claims in which the rotor is secured directly to the driven shaft.

10. A rotary diamond cutting machine as claimed in any one of claims 1 to 8 in which a coupling (22) is interposed between the rotor and driven shaft.

11. A rotary diamond cutting machine as claimed in claim 10 in which the coupling is a magnetic coupling.

12. A rotary diamond cutting machine as claimed in any one of the preceding claims in which the working disc is selected, optionally interchangeably, from a phosphor bronze cutting disc and a polishing wheel.

13. A rotary diamond cutting machine as claimed in any one of the preceding claims in which the operative speed of rotation of the shaft is in excess of 10,000 rpm.