US2424544A - Art of grinding annular surfaces - Google Patents

Description

July 29, 1947. J. w. ALSDORF ART OF GRINDING ANNUL'AR SURFACES Filed March 25, 1944 4 Sheets-Sheet l July 29,1947. J. w. ALSDOYRF. 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 25, 1944 4 Sheets-Sheet 2 July 29, 1947. J. ALSDORF 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 23, 1944 4 Sheets-Sheet 3 July 29, 1947. J. w. AL'SDORF 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 25. 1944 4 sheets-shet 4 Patented July 29, 1947 ART OF. GRINDING ANNULAR SURFACES James W. Alsdorf, Winnetka, Ill., assignor, by

mesne assignments, to Cory Corporation, a corporation of Delaware Application March 23, 1944, Serial No. 527,744

This invention which relates generally to the grinding of annular surfaces is concerned both with an apparatus and a method therefor. In particular the herein disclosed apparatus and method have special utility in the grinding of an annular sealing surface upon the upper bowl of a vacuum coffee brewer which is commonly produced from boro silicate glass. Problems encountered in the grinding of such objects include (1) the high degree of precision that is required, (2) the extremely hard nature of the work that is to be treated, and attainment of (3) speed and uniformity in each operation so that the cost may be held to a minimum.

With the aim of attaining these and other bjectives, I have devised a simple and inexpensive apparatus for carrying out this invention, a suggestive embodiment being illustrated in the drawings in the manner following:

Figure 1 is a view in horizontal section, taken on line l l of Fig. 2, showing in plan the relationship of the several grinding wheels, also the drives therefor; Figs. 2 and 3 are vertical sections, taken on line 2-2 of Fig. 1, showing the work holding means in different positions; Fig. 4 is a detail in section, taken on line 4-4 of Fig. 2; Fig. 5 is a detail in elevation, taken from line 5-5 of Fig. 2; Fig. 6 is a detail in section, taken on 5 Claims. (01. 51-431) line 6-5 of Fig. 2; and Fig. '7 which is an inverted view in plan of the upper bowl of a coffee brewer shows the annular surface on which grinding is performed.

As shown, the apparatus comprises a bed 5 supported upon legs 6, with a pair of motors 1 and 8 disposed opposite adjacent sides of the bed at points therebelow. Resting upon the bed is a pan 9 having in its bottom a more or less central opening and three other grouped-about openings through all of which, and the bed as' well, are extended certain vertical shafts as will now be explained. The central shaft l5 which is splined for axial movement relative to a driving pulley it near its lower end extends upwardly through a suitable bearing I! having a flange l8 which overlies the bed to rest thereupon. In like manner the remaining three shafts 20, 2|, and 22 which are disposed substantially equidistant from each other and from the central shaft, are each extended vertically through lower bearings 23 affixed to the bed and through upper bearings 24 which rest on the pan bottom, these three shafts carrying at their lower ends pulleys 25 at elevations which are desirably staggered. Belts 26 extending over these several pulleys 25 and a multiple pulley 2'! on the shaft motor 75 provide a power transmission which will produce a concurrent unidirectional rotation of all three shafts 2|], 2|, and 22. Between the pulley It on the central shaft and the other motor 8 there is also a transmission belt 28 whereby to drive this shaft independently of the others both as to speed and direction of rotation.

Afiixed to one side of the bed is a bracket 29 provided with a vertical guideway 36 wherein is slidably supported a framework comprising a post 3| from which is extended a tension adjusting device for holding the work under axial pressure in a rotating chuck. As shown, this device includes a fixed lateral arm 32 in pivotal connection with one end of a link 33 whose opposite end is pivotally joined to an adjusting lever 34 extending in a generally horizontal direction over the pan. The framework also comprises a second fixed arm 35 which extends laterally from the post to overlie the pan substantially in line with the central shaft [5, this arm being provided with a bearing 36 through which a vertical thrust rod 31 is slidably supported. This rod which is coaxial with the shaft l5 extends upwardly to support thereon a fixed collar 38 receiving thrust from the lower end of a compression spring 39 which is coiled around the rod, the upper spring end engaging with a collar 49 that is pivotally joined at 4| to a yoke 42 upon the lever 34 (see Fig. 4). A fixed bracket arm 43 also forming part of the framework is extended laterally from the post 3] at a point near its upper end and carries a top bearing 44 for the thrust rod 31, and just above this bearing the rod may be fitted with a stop collar 45 by which to limit its downward movements.

Extending upwardly from the fixed arm 35 proximate to the pressure rod is a bar 46 carrying a bearing 41 wherein is rookably mounted a shaft 48 operable by a crank pin 49. A grooved 'eccentric wheel 59' is carried fast upon this handle pin from the eccentric wh'eel, whenever the lever is to be swung upwardly to the position indicated by the dotted lines in Fig. 3, the pivotal connection 4! between the yoke 42 and adjusting lever being slidable, as required, for this purpose. In any such upward movement the spring 39 contributes an assisting force. Desirably the eccentric is rotated preliminarily to the dotted line position of Fig. 3 so as to minimize the manual force, counter to that of the spring, require for disengagement of the handle pin, and conversely, upon return downward swinging movement of the lever, the eccentric should remain in this same position until after re-engagement of the handle pin with the eccentric has been effected. The spring will then be under tension, but not so much as after the eccentric has been rocked to the full line position of Figs. 2 and 3.

Returning now to the axially movable, power driven central shaft I5 whose upper end is extended through the bearing l1 and pan bottom, I provide also an upper bearing therefor which comprises an arm 55 extending fixedly from the framework post 3| and formed at its outer end into an elongated cup 56 for accommodation of roller bearings 5'! rotatably supporting a chuck which may comprise a hollow cylindrical head 58 that is carried fast on the upper end of the shaft with a thrust collar 58 affixed thereto in engagement with the bottom end of the cup. Above the cup the head is formed with a flange 60 from which depends a skirt 6| in overlapping relation to the upper edge of the cup, whereby to prevent ingress of grit or foreign matter to its interior.

At its top the head is formed with a cylindrical boss 62 around which is a shell 63 extending upwardly therebeyond to confine in place a resilient or yielding seat 64 having a central opening in communication with the interior of the head. Between the cup bottom and pan bottom I may extend an extensible boot 65 having one end affixed to each whereby to prevent ingress of grit or foreign matter to the lower bearing IT. The parts just described, viz. the head 58, shell 63 and seat 84, constitute the principal elements forming the chuck wherein the object is supported.

The post 3| which has capacity for limited vertical sliding movements in the guideway of its supporting bracket is in pivotal connection at 10 with a control lever H which is fulcrumed at 12 upon the upper end of a link 13 having a pivotal connection at 14 with the bracket 29. Near one lever end beyond its fulcrum point is a weight 15, the lever through its opposite end region being somewhat laterally offset (see Fig. 6) to clear a head 16 which is mounted at the lower end of the thrust rod 31 for free rotation thereon. In the path of movement of the control lever is the trigger I! (or other actuating element) of a micro-switch 18 in electrical connection 19 with the motor 8 by which the shaft I5 is driven, the arrangement being such that with such downward movement of the control lever H, counter to the force exerted by its weight 15, the switch will be closed to cause rotation of the central shaft and the head supported thereby, and with each upward movement of the control lever to produce a cessation of such rotation.

Typical of the .work upon which grinding may advantageously be performed with the apparatus herein disclosed is the upper bowl for a vacuum coffee brewer. Such an object may take the form of a bowl 88 having on its bottom a raised annulus 8| to the inside of which the bowl walls continue on downwardly to provide a hollow base forming a well 82 whose bottom, in the center region, is downwardly flared at 83 to join with a depending hollow stem 84 (see Fig. '7). The annulus of such an upper bowl is rested upon the seat of a complementary lower bowl when the coffee brewer is assembled for operation. Such an annulus and the seat whereon it is rested sh'ould cooperate to establish an effective seal between them independently of any extraneous means, and to accomplish this the contacting surfaces are ground and then lapped to the degree of precision necessary for attainment of this objective. The grinding operation may be expeditiously and accurately performed by positioning the work upon the head 53 with its stem extending down into the interior thereof. The base or bottom of the bowl well will then rest upon the resilient seat 64 whose central opening is flared in conformity with the flare 83 of the bowl bottom whereby to center the work accurately in place. Inside the bowl is then placed a cylindrical block 85 of wood or the like, the bottom end of this block being formed with an axial boss which enters slightly into the well. In this way the block is centered within the bowl so as to bear evenly and continuously at every peripheral point directly over the annulus which is to be ground.

The top end of this block extends to a point about even with the top of the bowl so as to receive engagement from a head block 86 which is supported upon the underface of the rod head 16. With such an arrangement of parts, the Work, after being coaxially fitted into the head seat 64, is pressure held thereon and thereby positively locked thereto so as to rotate therewith in response to downward movement of the control lever H which also produces a like movement of the post 3|; and in this latter movement the entire tension adjusting device also participates so that the thrust rod 31 is advanced toward the work to exert thereon a yielding force whereby to hold the work firmly against the chuck seat.

When the work i positioned in the chuck for rotation therewith, the raised annulus 8| will lie just beyond the periphery of the shell 63 in a position of exposure for engagement concurrently with flat annular grinding surfaces 98 which are extended slightly above the top surfaces of grinding wheels 9| of disk form (three being the number shown) mounted respectively upon the shafts 20, 2| and 22 to be driven thereby. Adjacent each grinding wheel is a holder 92 for containing a supply of finely divided abrasive material in a pasty mass upon which water may drip from a valve pipe 93 to assure a more or less continuous feed of the abrasvie material to the several grinding surfaces which engage the work when performing a grinding operation upon its raised annulus.

During operation of the machine the three grinding wheel will remain continuously in motion, say at about 700 R. P. M., rotating preferably all in the same direction. The spacing and grouping of these wheels (see Fig. 1) is such that each presents only a small arc of its grinding surface in contact with the work annulus to be operated upon, yet the combined areas thereof are a substantial part of the work annulus. When the work is to be placed in the chuck, which is then motionless, the parts will occupy positions as indicated in Fig, 3, the tension lever 34 being raised to its uppermost position (shown in dotted lines) to permit lifting of the thrust rod 3! in response to expansion of the spring 39. The'rod head 16 and head block 85 are then moved away from the chuck .a distance sufficient for placement of the work therein. The next step is to apply pressure axially of the work to hold it firmly in its seat Withinthe chuck. This involves a down pull on the tension lever to the point of positioning its handle pin :l beneath the eccentric wheel so that the spring 3.9 may be placed under compression to exert its force against the thrust rod ti; and if the eccentric wheel be thereafter rotated to anopposite position the tension of this spring, and in consequence th pressure exerted thereby, will be substantially in creased.

Up to this point the post 3i, together with all the mechanism supported thereby, is sustained in an upper position by the counter weight I5 on the control lever ll. The last step is to depress the free end of this lever thereby (1) closing the switch 18 to start operation of the motor 8 and rotation of the chuck (at a speed of perhaps 400 R. P. M.) with the work positioned therein, and (2) lowering the work, while pressure-held c0- axially in the revolving chuck, to a position of concurrent engagement with the coplanar grinding surfaces of the three wheels 2!], 2|, and 22. During the ensuing few moments, while the work is maintained against these grinding surfaces in response to pressure exerted by the control lever, a grinding operation takes place. The annulus of the work is uniformly and accurately treated at every point in consequence of its rotation at a relatively slow speed in a direction counter to the somewhat faster movement of the coplanar grinding surfaces. This grinding operation is assisted by a slow, more or less steady, feed of fine abrasive material which is placed between the contacting surfaces. A brief time is sufficient to perform the desired grinding after which the control lever is raised, the spring pressure is released, and the work is removed from the chuck which is then at a standstill.

It will be noted that the present mechanism utilizes (l) a chuck which is axially movable to advance the work, while rotating, toward and from the relatively rotating coplanar grinding surfaces, and (2) a tension adjusting device by which to hold the work with a yielding pressure against its yielding seat in the chuck. This is advantageous inasmuch as the work is of a fragile nature and should be adequately protected against jars and shocks at every stage of the grinding operation. Not only is the work positioned against a seat that is yieldable within the chuck, but it is held against this seat in response to a yieldable thrust forcethat is axially directed and maintained constant regardless of the relative axial positions of the chuck and grinding wheels.

I claim:

1. For grinding an annular surface upon an object, an apparatus which comprises a group of closely spaced wheels having parallel axes and co-planar grinding surfaces, a chuck for the ob ject rotatable about an axis parallel with those of the grinding wheels, a framework including a mounting wherein the chuck is fixedly held, a support wherein the framework is held for sliding movement in a direction parallel to the chuck axis, a thrust rod coaxial with the chuck having freely rotatable means engageable with the object, means carried by the framework supporting the thrust rod for movement axially of itself, tension means urging the rod axially toward the object, driving means for rotating the grinding wheels, other driving means for the chuck including a pair of axially slidable transmission elements, and means for imparting sliding movements to the framework whereby to advance the chuck-supported object toward and from the grinding wheels without affecting the force of the tension means urging the rod toward the object.

2. For grinding an annular surface upon an object, an apparatus which comprises a group of closely spaced wheels having parallel axes and co-planar grinding surfaces, a chuck for the object rotatable about an axis parallel with those of the grinding wheels, a framework including a mounting wherein the chuck is fixedly held, a support wherein the framework is held for sliding movement in a direction parallel to the chuck axis, a thrust rod coaxial with the chuck having freely rotatable means engageable with the object, means carried by the framework supporting the thrust rod for movement axially of itself, driving means for rotating the grinding wheels, other driving means for the chuck including a pair of axially slidable transmission elements, and means for imparting sliding movements to the framework whereby to advance the chuck-supported object toward and from the grinding wheels.

3. For grinding an annular surface upon an object, an apparatus which comprises a group of closely spaced wheels having parallel axes and co-planar grinding surfaces, a chuck for the object rotatable about an axis parallel with those of the grinding wheels, a framework including a mounting wherein the chuck is fixedly held, a support wherein the framework is held for sliding movement in a direction parallel to the chuck axis, a thrust rod coaxial with the chuck having freely rotatable means engageable with the object, means carried by the framework supporting the thrust rod for movement axially of itself, driving means for rotating the grinding wheels, other driving means for the chuck, and means for imparting sliding movements to the framework whereby to advance the chuck-supported object toward and from the grinding wheels.

4. For grinding an annular surface on an object, an apparatus comprising a main frame having a vertical guide, a vertically slidable frame mounted in the guide, a vertical motor actuated shaft journaled in the slidable frame and carried by the same and provided at its upper end with a chuck, a vertical thrust rod journaled in the slidable frame co-axially with said shaft and mounted for both sliding and rotary movement, and provided at its lower end with means cooperating with said chuck for gripping an object to be ground, closely spaced coplanar grinding wheels grouped around said shaft in position for grinding the object held between the chuck and the thrust rod, means for locking the thrust rod in engagement with said object, and operating means for raising and lowering the slidable frame to carry the object into and out of engagement with the grinding wheels.

5. For grinding an annular surface on an object, an apparatus comprising a main frame having a vertical guide, a vertically slidable frame mounted in the guide, a vertical shaft journaled in the slidable frame and carried by the same, and provided at its upper end with a chuck, a vertical thrust rod journaled in the slidable frame co-axially with said shaft and mounted for both slidable and rotary movement and provided at its lower end with means co-operating with said chuck for gripping an object to be ground, close- 1y spaced coplanar grinding wheels grouped 5 around said shaft in position for grinding an object held between the chuck and the thrust rod, a locking device mounted on the slidable frame for holding the thrust rod in engagement with said object, said locking device being provided with yieldable means engaging the thrust rod for exerting a predetermined pressure on said object, and. operating means for raising and lowering the slidable frame to carry the object into and out of engagement with the grinding wheels while the object is held between the chuck and the thrust rod.

JAMES W. ALSDORF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,973,150 Morgan Sept. 11, 1934 492,095 Medart Feb. 21, 1893 493,294 Procunier Mar. 14, 1893 95,341 Harper Sept, 28, 1869 1,799,109 Lyne Mar. 31, 1931 1,084,529 Bentzon et a1. Jan. 13, 1914 1,575,311 Bentzon Mar. 2, 1926 2,226,782 Sandberg Dec. 31, 1940 975,408 Fry Nov. 15, 1910 386,738 Christie July 24, 1888 737,811 Altenbaugh Sept. 1, 1903 1,607,292 Miller Nov. 16, 1926

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