IL103227A - Cleaving press for rough gemstones - Google Patents

Description

CLEAVING PRESS FQR ROUGH GEMSTONES The present invention relates to a press for cleaving rough gemstones .

More particularly, the invention is concerned with providing an electrically powered mechanically operated short-stroke press for use in lapidary plants.

Gems tones are produced from roughs, sometimes known as rocks or slabs. Such roughs may be divided into smaller pieces by the use of various appliances, including a disk saw, an abrasive band, a hammer, cutter pliers having hardened jaws, a laser beam or by a press. Roughs having existing cracks are particularly suited for cleaving by use of a press, as the rough will be divided by expansion of the crack if the rough is properly oriented in the press, thus producing two or more smaller pieces not marred by this major fault.

A method for cleaving gemstones by the use of a small device arranged to provide a percussion blow on the stone resting on an anvil is described in Israel Patent No. 60228 to Gersan . This device has not been accepted for general use in the industry, as those with experience in gemstone cleaving prefer to apply a steady, if higher force to the rough. The present invention applies only to the cleaving method where a high force is to be slowly applied.

It is generally accepted that the press force needed for handling a variety of roughs should not be less than 10 tons. However, of the many types of press available having this capacity, none are well suited to the particular requirements of stone cleaving in lapidary p lan ts . for example from the SHOHAM Company in Tel Aviv, but even this inadequate force capacity is achieved by the use of a very large diameter air cylinder which would be difficult to operate from the small air compressors found in lapidary plants. Furthermore, it is to be noted that many such plants have no supply of compressed air at al 1.

Regarding electrically powered presses, two types are widely used -the mechanical type and the hydraulic type. In the mechanical type a continuously running electric motor drives a flywheel, the latter being connected by means of a clutch to the ram mechanism when a press stroke is required. The hydraulic . type has an oil pump continuously driven by an electric motor, and high pressure oil is routed by means of control valves to a hydraulic cylinder when a press stroke is required. Both types have been developed mainly for processing metals and plastics, and are usually arranged to provide a long stroke for executing processes such as extrusion or metal drawing. The cleaving of gem stones demands only a short stroke. However, these presses are usually large, and produce more noise than can be tolerated in the typical lapidary plant. The primary sources of noise in the mechanical type are the components affected by the shock of clutch engagement, while in the hydraulic type most of the noise comes from pulsations in the oil pump.

Manually powered presses operated hydrau 1 ica 1 ly are available in the required capacity. These are equipped with a long operating handle and therefore require considerable space, which is in surprisingly short supply in many lapidary plants. Furthermore, the considerable muscular effort needed to operate the press is a distracting factor for the user whose efforts should be concentrated on obtaining the best possible results from the valuable material being processed. Also, many users prefer using a valve or pushbutton instead of the bodily exercise provided by a manually powered press.

An important consideration is that the above mentioned prior-art presses, with the exception of the manually-powered type, will exert their full rated pressing force, or more, on any solid workpiece inserted in the press. For example, a 10 ton press wherein is inserted a solid steel block may well exert 13 tons force thereon. With regard to the cleaving of gemstones, it is desirable that the user have some control over the maximum force exerted, in order to avoid damaging a valuable rough, particularly one that has not been inserted into the press in its best orientation . In the case of the manually powered press, the user is able to control to an approximate extent the force exerted, but precise control requires of the user considerable skill and experience.

It is therefore one of the objects of the present invention to obviate the disadvantages of prior-art presses and to provide a short stroke electrically powered press for cleaving gemstones suitable for carrying out this operation in the typical lapidary plant.

This the present invention achieves by providing a short-stroke electrically driven mechanically operated press for cleaving gems tone roughs, comprising a press frame adapted for operation when resting on a worktable, and provided with support means for a rough gemstone, and provided with guide means for a vertic l-axis ram; a vertical-a s ram slidably suspended by said guide means between an upper and a lower position; a mechanism for exerting a downward force of at least 6 tons on said ram over a stroke of at least 1 centimeter and provided with means for returning said ram to its upper position; a reversible direction intermittently operatable electric motor attached to said press frame; and speed reduction drive means connecting the electric motor to said mechanism.

In a specially preferred embodiment, the press is further provided with an overload sensing device arranged to reverse motor rotation in response to press overload, and there is provided means readily accessible to the user to adjust the press force setting at which motor reversal occurs.

It is to be noted that the press of the present invention, unlike typical metal-processing presses, will be used intermittently and not continuously. Therefore the extra heat generated in the motor as a result of direction reversal will be dissipitated by the natural heat transfer processes while the motor is at rest.

The press of the present invention is preferably operated by a cam mechanism or by an equivalent eccenter. Unlike the power screw and its associated nut, the cam or eccenter is a simple machine element and is easily built to reliably transmit a high force with minimum maintenace. The cam mechanism is referred to in the description of the present invention as it has a number of advantages over the eccenter; for example, the cam mechanism is not limited to the sine-wave velocity produced by the eccenter, but may be arranged to provide a more constant velocity after initial acceleration.

It is also to be noted that the toggle mechanism found on many presses is inappropriate for the cleaving of gem stone roughs. The toggle mechanism provides a high force at the end of its stroke but a low force at its beginning. However the requirement for a high force when cleaving gemstone roughs may occur at any part of the stroke, depending mainly on the vacant space between the punch and the rough before the press operates. For example, if the rough is very close to the cleaving punch when starting, a high force will be required near the beginning of the press stroke.

While the invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood, it is stressed that the particulars shown and described are by way of example and for purposes of illustrative discussion only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the devices and their elements in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how several forms of the invention may be embodied in practice.

In the drawings: FIG. 1 shows a perspective view of a preferred embodiment of the press according to the invention; FIG. S is a fragmented front elevation showing support pads arranged on a turntable; FIG. 3 is a front elevation of the lower extremity of the ram and associated cleaving punches; FIG. is a side elevation showing the joystick switch; FIG. 5 is a perspective view of an enclosure for the working area of the press incorporating a safety device; and FIG. 6 is a side view of a user-adjustable overload prevention device for the press of the present invention.

There is seen in FIG. 1 a short-stroke electrically driven mechanically operated press 10. By short-stroke is meant a stroke of between one and three centimeters, this being adequate for cleaving gemstone roughs, in conjunction with means which are provided for supporting the top surface of the rough near the lowest point of the cleaving punch.

A small press frame 12, adapted for operation of the press when resting on a worktable 1 , comprises a bed table 16, at least two support pillars 18 and an upper member 20 supporting ram guides 22. By small the reference is to a worktable connected to pillars 18 not more than approximately 0 centimeters apart. Such a dimension is possible for the purpose of cleaving rough gemstones, as the largest dimension of the object to be handled will not exceed a few centimeters. The advantage gained is not only in the obvious observation that a smaller frame will require proportionally less material in its manufacture than a large frame. Less obvious is the fact that a smaller frame can carry a required load using thinner section material than can a larger frame, as the bending moments which must be resisted by the frame when the press is in use are smaller in a smaller frame than in a larger frame.

Any metal block of appropriate height provided with parallel upper and lower faces 26, 28 resting on the bed table 16, may be used as a support pad 2 for a gemstone rough 30. It is even possible to use the bed table 16 itself for this purpose. I t is however preferable that there be provided a plurality of interchangeable support pads 24 having different heights for the support of gemstone roughs 30 of varying sizes. There is further advantage in the upper face 26 being concave to provide better support for the rough 30.

A vertical-axis ram 32 is slidably suspended between an upper and a lower position 34, 36 by ram guides 22 attached to the upper member 20.

Also attached to the upper member 20 is a mechanism 38 for exerting a downward force of at least 6 tons on the ram 32 over a stroke of at least 1 centimeter.

The drawing shows a mechanism 3B comprising of a revolvably driven shaft 40, a plate cam 2 rigidly attached to the shaft 40 and provided with an edge 44 configured to apply a downward force on the ram 32.

The shaft 40 is revolvably supported in bearings 46 attached to the press guides 22 or to the frame 12.

The mechanism 38 is also provided with means such as a tension spring 48 connecting the ram 32 to the frame 12 for returning the ram 32 to its upper position 34.

A reversible direction intermittently operatable electric motor 50 is attached to the press frame 16. A three-phase induction motor rated between 0.5 to 1 horsepower is suitable.

Speed reduction drive means 52 connect the motor 50 to the mechanism 38. Typically means 52 comprise a 4:1 speed reducing belt drive 54 and a 50:1 worm reducer 56. Such an arrangement connected to a 1400 r.p.m. motor 50 will drive the shaft 40 at about 7 r.p.m. As only half a revolution of the shaft 40 is required to provide the downward stroke of the ram 32, the rough 30 can be split in approximately 4 seconds.

Control means 58 are provided to start and stop- the motor 50 and to change its direction of rotation. As is known, 3 phase motors are easily reversed by a suitable contactor 60 exchanging any 2 phases. An upper limit switch 62 is arranged to stop the motor 50 as the ram 32 nears its upper position 34, and a lower switch 64 is arranged to reverse motor rotation as the ram nears its lower position 36. A "GO" pushbutton 66 is used to initiate the press downward stroke.

Additional control elements will be described with reference to FIG. 4.

FIG. 2 shows a plurality of support pads 2 attached to a turntable 68 which is arranged so that any pad 4 may conveniently be positioned by the user directly under the ram center. The pads 24 have different heights so that the user is able to select a pad 24 in accordance with the rough 30 to be split. A large rough will require a low pad 2 1 and a small rough a high pad 24h. Thereby the upper surface of any size rough can be positioned to be in close proximity to the ram 32 or to a punch held thereby.

The turntable 68 is attachable to the bed table 16. A spr ing- loaded detent 70 is advantageous for fast location of any desired pad 24 under the ram centre.

There is seen in FIG. 3 a preferred embodiment of the lower extremity 72 of the ram 32 which is arranged to accept any one of a plurality of different cleaving punches 74. The extremity 72 is provided with holding means 76 such as a spring clip 78 for retaining a punch 74 in the ram 32. The user can remove and replace any punch 74 quickly by pulling out the punch 74, and does not require the use of a tool. The drawing shows examples of a flat head punch 74 and several wedge head punches 74a, 74b, 74c.

FIG. 4 shows a further preferred component of the motor control means 58.

A three-position joystick switch 80 is connected to the motor control contactors 60, thus enabling the user to cause the motor to drive in either ^direction or to stop. The joystick switch 80 replaces the simple "GO" pushbutton 66. The joystick switch 80 is particularly advantageous in stopping descent of the ram 32 immediately after a rough 30 has been split and in order to prevent damage to the remaining fragments.

There is seen in FIG. 5 an enclosure 82 substantially surrounding the working area of the press and configured to retain stone fragments therein. A suitable material for the enclosure 82 is transparent polycarbonate sheet.

A loading door 84 is provided in the enclosure 82. In a preferred embodiment of the press, an interlock safety switch 86 is fitted to be activated by the door 84. Closure of the door 8 completes an electric circuit, arranged so that the ram 32 cannot be operated downwards unless the door 84 is closed.

FIG. 6 shows an overload sensing device 88 arranged to reverse motor rotation in response to press overload.

The support pillars 18 are provided with at least one dished washer 90 held in compression between the support pillar nut 92 and the upper member 20. A proximity switch 94 supported by an extension 95 of the pillar 18 is held a short distance away from the upper face of the member 20. A high press force causes temporary flattening of the washer 90 and a reduction of the distance between the proximity switch 94 and the member 20. This causes activation of the switch 94 which is wired to activate the motor reversal contactor 60, seen in FIG. 1, thus causing the press ram to rise and preventing overload, and allows the washer 90 to resume its dished configuration.

With regard to the dished washer 90, it is to be noted that this item in the required capacity is commercially available as standard from several manufacturers, for example from C. BAUER Welzheim, Germany, who offer a 100 millimeter outside diameter disk 6 m"m thick which deflects 1.8 m"m under a force of 5100 kilograms.

It is highly advantageous to provide the user with conveniently

Claims (11)

adjustable means to limit press force according to the user's estimate of the desirable cleaving force to be applied to a particular rough. Accordingly in a preferred embodiment the overload sensing device 88 is provided with means readily accessible to the user to adjust the press force setting at which motor reversal occurs. This is easily achieved by mounting the switch 9 on the pillar extension 95 in a manner allowing some adjustment of its distance from the member SO. A lever handle 96 attached to a shaft 98 provided with a non-circular body 100 rigidly attached thereto may be used to change the position of the switch 94. A dial 10S adjacent to the handle 96 enables the user to choose any desired force setting. Levers 104 and 106 and a return spring 108 are shown supporting the switch 9 . While the particular embodiments of the invention have been described, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and. not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. WHAT IS CLAIMED IS:

1. A short-stroke electrically driven mechanically operated press for cleaving gemstone roughs, comprising: a press frame adapted for operation when resting on a worktable, and provided with support means for a rough gemstone, and provided with guide means for a vertical-axis ram; a vertical-axis ram slidably suspended by said guide means between an upper and a lower position; a mechanism for exerting a downward force of at least 6 tons on said ram over a stroke of at least 1 centimeter and provided with means for returning said ram to said upper position; a reversible direction intermittently operatable electric motor attached to said press frame; and speed reduction drive means connecting said electric motor to said mechanism.

2. The short-stroke electrically driven mechanically operated press as claimed in claim 1, wherein said mechanism comprises a revolvably driven shaft, a plate cam rigidly attached to said shaft and provided with an edge configured to apply a force on said ram, said shaft being supported in bearings attached to said press frame.

3. The short-stroke electrically driven mechanically operated press as claimed in claim 1, further provided with a plurality of interchangeable support pads having different heights for the support of gemstone roughs of varying sizes.

4. The short-stroke electrically driven mechanically operated press as claimed in claim 3, wherein said support pads are attached to a turntable arranged so that any of said support pads may conveniently be positioned by the user directly under the ram center.

5. The short-stroke electrically driven mechanically operated press as claimed in claim 1, further provided with a plurality of different cleaving punches, the lower extremity of the ram being provided with holding means for , said punches enabling the user to remove and replace any punch quickly without the use of a tool.

6. The short-stroke electrically driven mechanically operated press as claimed in claim 1, further provided with control means to start and stop said motor and to change its direction of rotation.

7. The short-stroke electrically driven mechanically operated press as claimed in claim 6, wherein said control means include a three-pos tion joystick switch enabling the user to cause the motor to drive in either direction or to stop.

8. The short-stroke electrically driven mechanically operated press as claimed in claim 1, further provided with an enclosure substantially surrounding the working area and configured to retain stone fragments therein.

9. The short-stroke electrically driven mechanically operated press as claimed in claim Θ, wherein a loading door is provided in said enclosure, and where an interlock safety switch prevents press operation unless said door is closed.

10. The short-stroke electrically driven mechanically operated press as claimed in claim 1, further provided with an overload sensing device arranged to reverse motor rotation in response to press over load .

11. The short-stroke electrically driven mechanically operated press as claimed in claim 10, wherein said overload sensing device is provided with means readily accessible to the user to adjust the press force setting at which motor reversal occurs. IS. A short-stroke electrically driven mechanically operated press for cleaving gemstone roughs, substantially as described hereinbefore and with reference to the accompanying drawings. Signed by the applicant: Yaakov Feust