US3525324A - Machines for sawing samples of brittle materials - Google Patents

Description

United States Patent Inventors Jean Roger Bonnel'oy Montrouge, France;

Bertrand Alain Dreyfus, Sevres, France Appl. No. 646,392 Filed June 15, 1967 Patented Aug. 25, 1970 Assignee PhotocircuitsCorporation Glen Cove, New York a corporation of New York by mesne assignments. Priority Dec. 27, 1966 France No. 88,986

MACHINESFOR SAWING SAMPLES OF BRITTLE MATERIALS 4 Claims, 5 Drawing Figs.

Int. Cl. B28d l/08 Field of Search 51/263,

[56] References Cited UNITED STATES PATENTS 637,121 111/1899 Huseby 5 l/263X FOREIGN PATENTS 717,874 11/1954 Great liritain 125/16 Primary Examiner- Harold D. Whitehead Attorney-Kemon, Palmer and Estabrook ABSTRACT: In a machine for sawing samples of brittle materials which acts by rubbing the samples with an array of metal wires against which they are placed while driven in an al e t later l me ep wi eiza ztaaw um Said array being made from a wire which is wound several times over wire-guides having multiple grooves, the abrasive medium is placed within a tank wherein at least part of one of the said wire-guides is immersed whereby the said abrasive medium is continuously homogenized while being carried by the very turns of the array up to a sawing location in the machine.

Patented Aug 25, 1970 3,525,324

Patented Aug. 25, 1970 Sheet MACHINES FOR SAWING SAMPLES OF BRITTLE MATERIALS CROSS-REFERENCES TO RELATED PATENT AND APPLICATION A machine for sawing samples of brittle materials of the kind with which the present invention is concerned is shown in U.S. Pat. No. 3,155,087 dated Nov. 3, 1964 and an improvement of a machine of this same kind is disclosed in co-pending application Ser. No. 604,810 filed Dec. 27, 1966 in the names of the same applicants as the present application.

Reference may be made to said patent for a complete description of the control system of the wire array and reference may be made to said application for patent for a description of the wireguides which may advantageously be used in the embodiments of machines according to the present invention.

BRIEF SUMMARY OF THE INVENTION In known machines, the abrasive medium is made from a mixture of an abrasive powder for instance silicone carbide powder with a carrier liquid such for instance as a machinery oil of appropriate viscosity. Such a mixture should be as homogeneous as possible at the working point or points, and further its quantity should be as constant as possible for optimum results in cutting of the samples.

Up to now, it has been conventional to provide such a mixture within a vat separated from the machine proper, to ensure stirring of the mixture in said vat for homogenization, and to transfer the mixture from the vat to the working place of the machine by means of a duct between said vat and a location just above the place where the samples are sawed. Obviously the output or flow from said vat ought to be such that there always is a quantity of the mixture on the sample in excess of the quantity of the material of said sample removed by the wire array.

In such prior art arrangements the results deteriorated as soon as the volume of the powder within the carrier liquid reached or exceeded the volume of the liquid. When the ratio is higher than unity, a sedimentation is very quick to occur in the duct connecting the vat and the sawing location in the machine, which results in an irregular feeding with a nonhomogeneous mixture during a working period and consequently, defects of the cutting were unavoidable. Applicants have now discovered that, in order to suitably increase the speed of cutting and concomitantly ensure good surface conditions of the walls of the cuts of the samples, the ratio of the volume of abrasive powder in the liquid must be at least equal to and preferably higher than unity. Such a condition has proven valid for all reasonable values of pressure between the sample and the wire array.

In order to obviate the drawbacks, of the prior art, it is provided according to the present invention to embody the homogenization vat within the sawing machine and to submerge at least part of a wire-guide of the wire array within the vat so that the wire-guide simultaneously contributes to the displacement of the said wire array and to the homogenization of the abrasive mixture.

According to a'further feature of the invention, it is provided to arrange part of the wall of the vat sufficiently near to said wire-guide that on part of the circumference of the wire-guide, there exists in the vat a close and relatively narrow portion wherein the mixture is formed essentially into a lamination in order to achieve better homogenization of the mixture.

As taught in the aforementioned patent, the wire array is driven in an alternating or reciprocating motion from the wireguides, at least one of which is periodically rotated in opposite directionsrEach displacement of the array in each direction of reciprocation is of constant amplitude. It is not at all imperative in a machine according to the present invention that the wire-guide is totally submerged within the mixture in the vat nor that the sample applied against the wire array is submerged within the vat, as the wire array will act as a mixture carrier straight from the vat to the sample by providing, when wanted, an amplitude of displacement of the wire array in its reciprocating motion such that part of the array passing through the mixture and consequently carrying an amount of said mixture over its wire turns reaches the location of the sample machined in the device.

It should be noted that, by the use of this invention, a substantial reduction of overall consumed quantity of the abrasive mixture is achieved since that part of the abrasive mixture brought from the vat to the sample will return to the vat, partly with the wire array and partly by falling down from the sample location within the vat. The same is true when the sample is also located within the vat. Actually, in any case, the quantity of mixture provided in the vat for a sawing operation will circulate in a closed pathwithout any appreciable loss.

DRAWINGS FIG. 1 shows a conventional arrangement of a wire array and wire-guides therefor in a sawing machine of the type to which this invention is directed;

FIG. 2 shows a front view and FIG. 3 shows a side view of a sawing machine embodying the present invention;

FIGS. 4 and 5 respectively show alternative embodiments of the present invention.

DETAILED DESCRIPTION Referring to the drawings, and more particularly to FIG. 1, it is shown that in a conventional machine, the wire array is often made with three wire-guides, l, 2 and 3, one of which is the driving member for the reciprocating motion of the array. The wire-guides l and 2 define a horizontal plane for the array 4 and the wire-guide 3 is positioned beneath said plane. Each wire-guide is provided with the same number of grooves, and it will be appreciated that the number shown on thedrawing has been reduced for the sake of clarity. The wire shown for instance enters the array at 5 and exits at 6 after being spiralled around the wire-guides from grooves to grooves of these members. Means, not shown but conventional in the prior art, ensure the constant renewing of the wire throughout said array and simultaneously the reciprocating motion of the wire in the array from periodic reversal of the direction of rotation of the driven one of the wire-guides. The wire is uniformly stretched along the complete length thereof. In accordance with the present invention the amplitude of displacement of the wire will be so chosen that it will ensure a displacement of the wire in each turn of the array which is at least equal to the sum of the horizontal length and one lateral length of the array. Preferably, the amplitude will be so adjusted that for each alternate stroke, the turns of the wire in the array will make a complete travel throughout the array. As shown in FIG. 2, at some place along the horizontal part of the array,the sample 9, carried by a base, is pressed against the array at a constant value of pressure in the direction of the arrow 8 during each sawing operation; such an arrangement being quite conventional in sawing machines of this kind.

A vat 10 is provided on the front wall of the framework 14 of the machine. The front wall of the vat extends, for instance, up to a level 11 higher than that of the wire-guide 3 which is located within the vat. The rear wall of the vat may be made, as shown, from the wall of the framework, the axle of the wireguide 3 passing through said wall by means of a liquidtight arrangement. The lateral wall of the vat is secured to'the' framework 14. Said lateral wall is shown as comprising a substantially semi-cylindrical bottom portion, extended on both sides by slanting portions such as 12 and 13 reaching a higher level than the level of the horizontal plane of the wire array. The axis of the semi-cylindrical part of the vat is so shifted with respect to the axis of the wire-guide 3 that, between the bottom of the vat and the lower part of the wire-guide, the. distance, as shown at 15, is reduced in order to form a lamina-- tion of the abrasive mixture which partly fills the vat.

lllustratively, and assuming wire-guides of about 40 mm in diameter, the spacing between the axes of the wire-guides l and 2 may be of the order of 80 mm and the vertical distance between the axis of the wire-guide 3 and the plane of the horizontal array may be about lOO mm. The radius of the semicylindrical part of the vat may be of the order of 40 mm with a relative shift by mm between its axis and the axis of the wire-guide 3. Of course, such dimensions and shapes may be varied without departing from the spirit and scope of the invention.

When the wire-guides rotate, for instance at a speed of about 600 r.p.m. and, for instance also, during one second in one direction of rotation and one second in the other direction of rotation, alternately, the abrasive mixture is stirred by the wire-guide and duly homogenized within the area 15 of the vat. Simultaneously, part of the mixture is carried by the turns of the wire array according to a path indicated in FIG. 2 for one of the directions of rotation, to a mirror path for the other one of said directions of rotation. The interrupted lines in FIG. 2 substantially define the movements within the mixture and the limits of that part of the mixture carried by the wire array. A first part of the mixture circulates around the wire-guide 3; at 16 a cumulative mass of abrasive mixture occurs on the portions of the wire turns in their upward movement, hence at 17 the presence of a substantial part of said mixture and its carrying to the level of the horizontal part of the array, including the place where the sample is being machined. Most of said mixture falls down to the vat and the remaining part is brought back to the vat through the path 19 and mixed again with the part remaining in the vat at 20. The abrasive mixture actually presents a sufficient viscosity for such an operation, as the ratio of the abrasive powder in the carrier liquid is atleast equal to and preferably higher than unity, usually of the order of 1.5. With such an appropriate choice of the viscocity and speed of rotation, applicants have, for instance, obtained the carrying of nearly three-quarters of the mixture in the vat up to the place where the sample was sawed, during one complete hour of operation. The volume of the vat, and of the abrasive mixture, however, are not critical. It is sufficient that the volume of the abrasive mixture be such that the quality of the sawing is preserved during a complete operation, which means that the volume of abrasive mixture must be substantially higher than the quantity of the material which, during the operation, passes as a fine material powder into the said mixture.

In FIG. 3, it must be considered that one side of the vat, including one lateral wall, has been removed from the drawing.

In FIG. 4, the invention is disclosed as applied to a machine wherein the wire array is defined by four wire-guides, l-2 for the upper horizontal part of the array, 33-43 for the lower horizontal part thereof. The vat is shaped with portions of restricted volume near the lower wire-guides, as shown at 31 in order to insure homogenization of the abrasive mixture. In FIG. 5, the invention is disclosed as applied to a machine using only one pair of wire-guides l-2. The vat is similar to that of FIG. 4, but for its height. These two further examples are in no way restrictive, and any modification of the vat for adjusting to a special arrangement of the wire-guides in any machine will be apparent from such examples including the one of FIGS. 23.

In FIGS. 4 and 5, further, arrows indicate several possibilities for the location of the samples to saw. The dot line arrows refer to samples pressed against the wire array from the outside of the array; the full line arrows refer to samples pressed against the wire array from the outside of said array. Whereas, at each location defined by such arrows, only one sample may be sawed, several samples may be simultaneously sawed at distinct locations, up to four in the arrangement of FIG. 4, two in the arrangement of FIG. 5 (and similarly, FIG. 2 may admit the sawing of three samples at the same time). The lower wall of the vat may, as shown in FIGS. 4 and 5, be shaped for admitting samples to be sawn at such places, if desired; said shaped portion is shown at 32. It is immaterial that, durin a sawing operation, the sample is or 18 not submerged within 516 abrasive mixture.

We claim:

1. A machine for sawing samples of brittle materials by rubbing said samples with an array of a metal wire against which they are pressed, in the presence of an abrasive mixture of an abrasive powder mixed with a liquid carrier, said wire array being defined by multiple groove wire-guides and driven, from one at least of said wire-guides, in a reciprocating motion with respect to said samples, wherein said machine includes a vat of an abrasive mixture having a volume of abrasive at least equal to the volume of liquid, and in which vat and mixture at least a part of one of said wire-guides is submerged to supply said mixture to said wires.

2. Machine according to claim 1, wherein a wall of said vat is arranged near the lower part of said one wire-guide to define therewith a restricted height volume wherein a lamination of the mixture occurs during the alternate rotations of said one wire-guide.

3. Machine according to claim 2, wherein part at least of the samples are submerged within said mixture.

4. Machine according to claim 2, wherein at least part of the samples are above the abrasive mixture and the amplitude of the stroke of the turns of the wire array in its reciprocating motion carries part ofthe homogenized viscous abrasive mixture up to the location of such samples.

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