Lapping Machine Having Pressure Plates, The Temperature Of Which Is Controlled By A Coolant

Abstract

A lapping machine having one or more hollow pressure plates through which a coolant, such as water, is continuously circulated, during the lapping of work, to maintain a constant temperature of the lapping surfaces of the machine to avoid heating of the work or the means, such as wax or the like, which may be employed for holding the work in position beneath the pressure plate.

Description

Lapping machines heretofore known in the prior art include a rotatable lapping table on which work is confined within work-holding rings during the lapping operation. Within such work-holding rings are arranged pressure plates which bear the work in lapping relation with respect to the lap surface of the lapping table. In some cases the work is of relatively thin material, such as for example, silicone discs. Such discs are generally removably adhesively attached to the underside of the pressure plate by means of wax or other material to prevent the discs from shifting about between the pressure plate and the lapping table and becoming dislodged from proper lapping position beneath the pressure plate during the lapping operation.

Applicants' invention contemplates circulating through each of the pressure plates a liquid coolant, such as water, thereby to maintain a proper temperature during the lapping operation.

The preferred form of construction of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a fragmentary vertical sectional detail view of the invention;

FIG. 2 is an enlarged vertical sectional detail view of a fixture embodied in the invention;

FIG. 3 is a fragmentary vertical sectional detail view illustrating a modified form of construction;

FIG. 4 is an enlarged sectional detail view taken substantially on line 4-4 of FIG. 3;

FIG. 5 is a modified embodiment of the invention.

Referring more specifically to FIGS. 1 and 2 showing one embodiment of our invention, 10 indicates a rotatable lapping table of a lapping machine. A work-holding ring 11 is mounted on the table 10. Within the work-holding ring 11 is a pressure plate 12. Attached to this pressure plate 12 is a bearing housing 13.

Arranged in the bearing housing 13 are a bearing 14 and a ring 15 attached to a sleeve 16. The sleeve 16 is attached to a stationary spindle 17 which is carried by a horizontal arm (not shown) of the lapping machine.

The spindle 17 is held against rotation while the pressure plate 12 under the action of the lapping table 10 is caused to rotate about the sleeve 16. The work to be lapped is disposed between the bottom surface 18 of the pressure plate 12 and the top surface 19 of the lapping table 10. The pressure plate 12 in the present instance is of hollow construction to provide a chamber 20. Centrally formed in the top wall 21 of the pressure plate 12, is a thread-bearing opening 22 in which is threaded the nipple 23 of a rotatable conduit 24 of a fixture 25.

The conduit 24 is mounted within the casing 26 of the fixture 25 through roller bearings 27, the latter facilitating free rotation of the conduit 24. A split ring 28 serves to support the rotatable conduit 24 within the casing 26. The upper end portion of the conduit 24 has a counterbore 29 formed therein which receives the lower end portion of a stabilizing tube 30 having a tapered upper end portion 31 projecting into a bore 32 formed in the casing 26. The stabilizing tube 30 is provided with slotted lateral arms 30' which receive the lower end portions 33 of pins 34 fixed into adjacent wall portions of the casing 26, to hold the tube 30 against rotation by the rotatable action of the conduit 24.

Projecting into the bore 32 and surrounding the tapered end portion 31 is a resilient seal 35 normally urged into sealing position by a spring 36 disposed between the seal 35 and a plug 37 threaded into the outer end portion 38 of the tubular casing 26. The spring 36 is under compression and urges the seal 35 into sealing relation with respect to the tapered end portion 31. Threaded into the plug 37 is an elbow 37' to one end of which is threaded an inlet pipe 39.

Communicating with the bore 40 of the elbow 37' is one end portion of a tube 41, sealed within the cap 37 at a point indicated at 42. This tube 41 extends downwardly through the bore 43 of the rotatable conduit 24.

The tube 41 terminates a short distance above the top surface of the bottom of the pressure plate 12, as indicated at 44. The tube 41 is of a diameter smaller than the diameter of the bore 43 for the purposes which will be hereinafter made clear. An outlet pipe 45 is threaded into the casing 26 and communicates with the bore 32.

In operation, the lapping table 10 is rotated in a manner well known in the art and frictionally induces rotation to both the work-holding ring 11 and the pressure plate 12. Rotation of the pressure plate 12 will impart rotation to the conduit 24 relative to the stationary casing 26.

During this operation, a coolant, such as water, is admitted through the inlet pipe 39 to flow through the tube 41 into the pressure plate 12, circulating therein before passing out through the bore 43 and thence out through the outlet pipe 45. This flow of water from its source may be under its normal flowing pressure or, if desired, the flow may be under pressure by any suitable means. The main purpose is to continuously circulate the coolant through the pressure plate 12 to maintain a constant temperature and cool the lapping surfaces of the lapping machine, particularly that of the pressure plate.

Referring to FIGS. 3 and 4 showing a modified form of construction, a fixture 25' similar to the fixture 25 shown in FIG. 1, is employed. The work-holding ring 11', pressure plate 12', and lapping table 10' are substantially the same as their counterparts shown in FIG. 1.

In FIGS. 3 and 4, in lieu of the elbow 37' shown in FIG. 1, we thread into the bore 32' a cap 46 which has inner and outer bores 47 and 48 of different diameters, respectively. In the bore 48 is seated a flange-bearing ring 49 which projects as at 50 into the end portion of a flexible pipe 51, preferably formed of suitable plastic. The end of the pipe 51 is sealed about the ring 49 by a rubber seal 52 embracing the lower end portion of the pipe 51 as seen in FIG. 4, and compressed into sealing position with respect to the pipe 51 by a compression nut 53 threaded into the bore 47 of the cap 46. The pipe 51 projects through an L-shaped passage 54 formed in the spindle 17', which like the spindle 17 shown in FIG. 1, is fixedly held in position by a supporting arm (not shown).

A second plastic pipe 55 of a smaller diameter than the pipe 51 is passed through the latter and extends down into the bore 32' of the fixture 25'. Like the tube 41, the pipe 55 terminates just short of the inner surface of the bottom wall of the pressure plate 12'. In the form shown in FIGS. 3 and 4, the coolant is admitted to the pressure plate 12' through the pipe 55, circulates through the pressure plate, and then passes therefrom through the pipe 51, thus completing circulation of the coolant through the pressure pate. The result is the same as that in connection with the arrangement shown in FIG. 1, namely, maintaining a cool temperature of the lapping surfaces.

The pressure plate 12' comprises a plurality of vertically extending posts 56 which are connected to the pressure plate 12' and support a plate 57 to which the spindle 17' is attached by means of a bearing structure 59 and split ring 60. The pipes 51 and 55 extend, as shown in FIG. 4, through this plate 57 and spindle 17'.

By forming the pipes 51 and 55 of plastic or other flexible material, such pipes permit any limited variable movement between the fixtures 25' and the spindle 17'.

In FIG. 5, we have illustrated a further embodiment of our invention which is a modified form of construction over that shown in FIGS. 1 and 3 in the following respects:

The pressure plate 61 (FIG. 5) comprises two separable interfitting parts: a pressure pad 62 and a work-holding fixture 63. The pressure pad 62 is of substantially the same structure as the pressure plates 12 and 12', FIGS. 1 and 3, respectively, and has associated therewith the fixture 25 for circulating water through the pressure pad 62 during the lapping operation. The primary function of the work-holding fixture 63 is to have removably secured thereto, on the bottom side 64 thereof, the work 65 which is to be lapped. The work 65 may be in the form of relatively thin discs, such as silicone discs or the like, and may be secured to the bottom side of the work-holding fixture 63 by means of wax or the like.

Unless the pressure pad 62 and work-holding fixture 63 are maintained at a proper temperature, the wax which holds the work to the under surface of the work-holding fixture 63 during the lapping operation, will melt and, as a result, the work will shift about the surface or be ejected therefrom during the lapping operation. This melting of the wax and consequent detachment of the work 65 from the work-holding fixture 63 is prevented by cooling the lapping surfaces through the medium of the coolant circulated through the pressure pad.

In this form of construction, the work-holding ring 11 and 11' (FIGS. 1 and 3 respectively) is omitted due to the fact that the work is maintained in position by being adhesively secured to the work-holding fixture by means of wax or the like; otherwise the construction shown in FIG. 5 is the same as that shown in FIG. 1.

After the work has been effectively lapped, the pressure pad 62 is separated from the work-holding fixture 63. When this has been accomplished, the work-holding fixture 63 is then lifted from the lapping plate to remove the lapped work therefrom.

While we have illustrated and described the preferred form of construction for carrying our invention into effect, this is capable of variation and modification without departing from the spirit of the invention. We therefore do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of such variations and modifications as come within the scope of the appended claims.

Claims

We claim:

1. An improvement in a lapping machine having a lapping table, the improvement comprising:

a. a pressure plate positioned on said table and hollowed to provide an enclosed coolant-circulating chamber; and

b. a fixture attached to and carried by said pressure plate and including means for circulating a coolant through said chamber comprising inlet means for delivering said coolant to said chamber and outlet means for said coolant from said chamber.

2. The improvement defined in claim 1 wherein said means for delivering the coolant to said chamber and the outlet means for said coolant comprises conduits having portions thereof in telescopically spaced relation with respect to each other within said fixture.

3. The improvement defined in claim 1 wherein said fixture comprises a stationary casing and a tubular portion axially rotatable with respect to said casing and means for connecting the rotatable tubular portion to said pressure plate.

4. An improvement in a lapping machine having a lapping table, the improvement comprising:

a. a pressure plate hollowed to provide a chamber and positioned upon said table;

b. a fixture having a nonrotatable tubular casing and a rotatable conduit rotatable relative to and supported by said casing;

c. a coolant supply pipe carried by said casing and having a tube extending therethrough in spaced relation with respect to the rotatable tubular conduit;

d. an outlet pipe for the coolant communicating with the casing;

e. means for connecting the rotatable conduit to the pressure plate for rotation therewith; and

f. said rotatable conduit extending into said pressure plate and terminating short of the inner surface of the bottom wall thereof.

5. In a polishing machine having a framework, an abrading wheel assembly mounted on the framework on a vertical axis, means for rotating the abrading wheel assembly, at least one vertical spindle assembly supported from the framework above the abrading wheel assembly, a generally horizontal load plate unit having a circular continuous uninterrupted lower surface concentric of the longitudinal axis of said spindle assembly and adapted to receive at least one workpiece at the lower surface thereof for engagement with said abrading wheel assembly, and means establishing interengagement between said spindle assembly and said load plate unit, the improvement comprising said load plate unit having a central opening in the upper surface thereof, said load plate unit having fluid passageway means communicating with said central opening, and said spindle assembly having fluid transmission means communicating with said central opening.