Method of and apparatus for lapping shoulders

April 28, 1959 _E. _F. katzke 2,883,802

METHOD OF AND APPARATUS FOR LAPPING SHOULDERS

Filed Sept. 24, 1956 2 Sheets-Sheet 1

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April 28, 1959 e. f. katzke 2,883,802

METHOD OF AND APPARATUS FOR LAPPING SHOULDERS

Filed Sept. 24, 1956 2 Sheets-Sheet 2

<img file="US2883802A_D0002.tif" />

United States Patent Office _PaleBted J’⁸2⁸gS

2,883,802

METHOD OF AND APPARATUS FOR LAPPING SHOULDERS

Ernest F. Katzke, Des Plaines, Ill,, assignor to Crane Packing Company, Morton Grove., Hl., a corporation of Illinois

Application September 24, 1956, Serial No. 611,495

Claims. (Cl. 51—125)

The present invention relates to lapping machines and methods and more particularly to apparatus for lapping a flat annular shoulder on an .object where the shoulder is spaced from the opposite ends of the object, as well as to a method which, when carried out on the object undergoing lapping, will result in the maintenance of a properly and accurately dressed lap surface on the machine which performs the lapping operation.

Heretofore, the automatic lapping of such shoulders, as distinguished from hand lapping operations, has been carried out by means of a flat rotating lap surface, utilizing one or the other of two more or less basic lapping methods. Either the lap surface is provided with a central axial opening which receives the protruding end of the object undergoing lapping so that the shoulder which is to be lapped rests on the lap surface at the rim of the opening, or the lap surface is formed with an annular groove therein of sufficient depth to completely receive the protruding end of the object with the shoulder to be lapped resting on the lap surface in the edge regions of the groove and straddling the latter. The latter method is disclosed in U.S. Patent No. 2,597,382, issued to Raymond G. Roshong on May 20, 1952. In either case, relative rotation or movement is set up between the lap surface and article to create the necessary abrading effect. In the former instance, the same unvarying abrading area of the lap surface is presented to the shoulder, resulting in rapid grooving of the lap surface so that it is necessary to remove and refinish the lap surface at short intervals. On the other hand however, substantially all of the surface area of the shoulder undergoing lapping is presented .simultaneously to the lap surface during the entire lapping cycle so that efficient lapping of the shoulder takes place. In the latter instance, a continuous presentation of a new or different abrading area is presented to the shoulder and the arrangement makes possible the use of so-called conditioning or wear rings to maintain the lap surface in its original or flat condition in accordance with the principles set forth in the reissue patent to Bullard, No. Re. 23,937, dated February 8, 1955 for Lapping Machine. However, with this latter method only a small fraction of the surface area of the shoulder undergoing lapping is engaged by the lap surface at any given instant and thus the lapping cycle is unduly prolonged. Furthermore, although this latter method is admirably adapted for use in connection with small objects, where the shoulders to be lapped have a large mean diameter, the width of the groove required to accommodate the protruding portions of the articles necessitates the use of a lap surface of large diameter and the provision of a lap plate having such a large diameter is costly..

It is accordingly an object of this invention to provide a method of lapping shouldered objects which combines the advantageous features of each of the above outlined methods of lapping shoulders on articles while, at the same time, overcoming the limitations that are attendant thereon.

As a more specific object this invention has within its purview a shoulder lapping method wherein, the type of lap surface liltilized in connection with the first described method is employed for actual lapping operations upon the shoulder undergoing lapping while the conditioning or wear ring principle utilized in connection with the second described method is employed for conditioning the lap surface.

A further object of this invention is the provision of apparatus for carrying out the foregoing methods and specifically, the provision of an annular lap surface associated with a single lap plate which continuously dresses one side of an annular lap while the opposite side thereof is lapping a shouldered article. Such conditioning operation taking place and being effected on one annular lap surface associated with a single lap plate simultaneously with the use of another annular lap surface on the same lap plate for actual lapping operations on the shoulder undergoing lapping. By such an arrangement, a relatively small diameter lap plate may be employed for shoulder lapping operations while additionally no time is lost in the partial dismantling operations which are attendant upon lap plate removal and refinishing operations.

These and other objects of this invention will become apparent from the following detailed description when taken together with the accompanying two sheets of drawings showing a preferred embodiment of the invention and a minor modification thereof.

In these drawings:

Fig. 1 is a fragmentary perspective view of a lapping machine constructed in accordance with the principles of the present invention and, .for illustrative purposes, shown lapping of the bolting flange associated with the cylinder assembly of an aircraft engine.

Fig. 2 is a plan view of a reversible annular lap plate employed in connection with the invention.

Fig. 3 is a plan view of the portion of the machine shown in Fig. 1.

Fig. 4 is an enlarged sectional view taken substantially along the vertical plane indicated by the line 4—4 of Fig. Land

Fig. 5 is a fragmentary sectional view similar to Fig. 4 showing a slightly modified form of reversible lap plate operatively applied to the aircraft cylinder bolting flange.

Referring now to the drawings for a detailed description of the invention and in particular to Figs. 1 and 3, a portion of a lapping machine framework 10 is shown, the portion illustrated being in the form of a generally rectangular casing providing a table top 12 and depending sides 14 within which all of the operative lap plate driving instrumentalities including the motor, reduction gearing, etc. (not shown) are enclosed. The table top 12 is formed with an opening 16 in which there is mounted for rotation about a vertical axis a lap plate 18 having an annular flat lap surface 20 defined by inner and outer peripheral edges 22 and 24, respectively. The lap plate 18 projects slightly above the level of the table top 12 so that the annular lap surface 20 is disposed slightly above the plane of the table top 12.

For convenience of description the lapping region immediately above the lap plate 18 may be divided into three sectors and in one of these sectors there is disposed a wear ring 26 which rests loosely by gravity on the lap surface 20 and overhangs both the inner and outer peripheral edges 22 and 24 thereof, respectively. The.wear ring 26 is provided with a flat annular abrading surface 28 on its underneath side which has an abrading effect on the lap surface 20, and means are provided whereby the radial position of the ring 26 may be adjusted to bring the surface 20 to the desired degree of flatness from ft condition of concavity or a condition of convexity .in a manner which has been made clear in the above men2,883,803 iioned reissue patent to Bullard. The ring 26 also serves to remove from the lap surface 20 any surface irregularities or scratches which may be present therein.

Still referring to Figs. 1 and 3, the means whereby the radial position Of the wear ring 26 may be varied is similar to that shown in the above mentioned patent to Roshong and comprises a so-called roller bar construction including a yoke member 30 adjustably located relative to frame 10 by a pin-and-slot connection 32 and clamped by a bolt assembly 34 to a horizontally disposed generally arcuate face plate 36, the latter being held above the table top 12 by anchoring studs 38 and spacer rings 40. The free ends of the yoke arms carry antifriction rollers 42 which engage the outer cylindrical surface of wear ring 26 and restrain the ring against revolution about the axis of the rotating lap surface 20 while at the same time permitting the ring to rotate freely about its own axis due to its frictional contact with the lap plate, all in a manner clearly set forth in the Roshong patent.

Referring now to Figs. 1 and 4, the lap surface 20, which hereinafter will be referred to as the primary lap surface, is adapted to receive thereon one or more annular lap plates 44, two such plates being shown in Fig. 4, each of which is in the form of a ring having annular secondary lap surfaces 46 formed on opposite sides thereof. Surfaces 46 are designed for use in lapping the annular shoulder of an object when the shoulder is offset from an end of the object in such a manner that the protruding end requires a clearance space before the shoulder may be positioned against the lap surface. For illustrative purposes herein the object to be lapped by each secondary lap plate 44 is shown as being in the form of a cylinder assembly for aircraft engines wherein the cylinder body 50 is formed with a radially extending continuous annular bolting flange 52 providing the shoulder 53 which it is desired to lap and having a series of bolt holes 54 extending therethrough and arranged in spaced relation therearound. The lower part 55 of cylinder 50 extends downwardly from the inner regions of the bolting flange 52 and precludes accommodation of the shoulder 53 on conventional flat lap plates having continuous or uninterrupted flat circular lap surfaces.

Each secondary lap plate 44 is formed with a cylindrical outer surface 56 around which there extends a ring gear 57 having radially disposed teeth 58 thereon. The gear 57 may be press-fitted, shrunk, welded or otherwise secured to cylindrical surface 56 approximately mid-way between the respective planes of the two flat secondary lapping surfaces. The lap plate 44 is formed with a central axial opening 60 therethrough defining a cylindrical bore or wall 62 the diameter of which is slightly larger than the external diameter of the lower part 55 on the cylinder body 50 so that when the plate 44 is resting on the upwardly facing lap surface 20 of the primary lap plate, with either secondary lap surface 46 in lapping engagement with the surface 20, the part 55 may be received in the bore 62 which provides a clearance for it so that the annular shoulder 53 on the bolting flange 52 may seat on the other or upwardly presented secondary lap surface and make intimate lapping contact in the immediate vicinity of the inner peripheral region thereof.

As best seen in Fig. 3, the central region of the primary lap plate 20 is formed with a shallow circular well 64 which defines the inner periphery 22 of the lap surface 20. The drive shaft 66 for lap plate 18 projects upwardly through said plate and well above the level of the lap surface 20 and has affixed thereto a central hub gear 68 having a series of radial teeth 70 thereon designed for meshing engagement with the teeth 58 provided on the ring gears 57 associated with the secondary lap plates 44. The mean height of the hub gear 68 above the plane of the primary lap surface 20 is substantially equal to the mean height of the ring gear 57 of each lap plate 44 regardless of which lap surface 46 thereof is resting upon the primary lap surface 20. The secondary lap plates 44 are symmetrical with respect to a plane extending transversely and centrally through the same and they are therefore reversible on the primary lap surface so that whichever lap surface is presented upwardly, that surface is positioned for lapping operations on the cylinder shoulder 53 while the opposite lap surface is presented downwardly and in contact with the primary lap surface so that it may be abraded by the latter and brought to a condition of flatness, all in a manner and for a purpose that will be made clear presently.

The various secondary lap plates 44, when operatively resting on the rotating primary lap surface 20, are held against revolution about the axis of the latter surface, as well as being held in such positions that their respective ring gears 57 mesh with the central hub gear 68, by means of roller bar assemblies similar to that already described in connection with the wear ring 26 and similarly designated in the drawings. It is to be noted that the overall height of the various roller bar assemblies including the yokes 30 and rollers 42 is less than the mean height of the ring gears 57 above the primary lap surface 20 so that there will be no interference with the operation of the rollers 42 which bear against the outside cylindrical surface 56 of the secondary lap plates 44 when the machine is in operation.

As shown in Figs. 1 and 3, the entire weight of the cylinder assemblies 50 is supported on the secondary lap plates 44 at the regions where the shoulders 53 of the bolting flanges 52 engage the inner peripheral regions of the plates. In order to create relative movement for lapping purposes between each assembly 50 and the secondary lap plate 44 on which it rests, a rod 72 has one end thereof pivotally secured to a standard 74 mounted on the upper face of the plate 36, the said one end of rod 72 being vertically slidable on and rotatable about a stud 75 which projects upwardly from the standard. The eleva» tion of the rod 72 above plate 36 is determined by a series of spacer collars 76 telescopically received over stud 75. A compression spring 78 encircles the stud and bears downwardly at one end on the rod, the other end reacting against a tension-adjusting nut 80 threadedly received on the upper end of the stud. The free end of the rod 72 carries a pin 82, the lower end of which is adapted to extend into one of the bolt holes 54 provided in the bolting flange 52 so that the rod extends approximately tangentially of the bolting flange 52 and supplies the countertorque or reaction force necessary to hold the bolting flange 52 against rotation with the secondary lap plate 44 on which it is supported.

As shown in Fig. 1, the machine is provided with a storage and agitator tank assembly 9® for the grit and the vehicle in which it is suspended the grit and vehicle comprising the abrading compound for the lapping operation. This abrading compound is fed through an aperture under the control of a solenoid-actuated valve mechanism designated in its entirety at 92 and travels by gravity along a thin rod or wire 94, the free end of which may make contact with a surface of the wear ring 26 to deposit the compound thereon whence it flows onto the lap surface 20 and become distributed thereover in the manner set forth in the above-mentioned patent to Bullard.

In the operation of the machine and according to the method of the present invention, with the various machine parts in the position in which they are shown in Fig. 1, and with the cylinder assemblies 5® in position on the secondary lap surfaces 46, rotation of the primary lap plate 18 and its drive gear 68 in a counter-clockwise direction as indicated by the arrow will cause the secondary lap plates 44 to be positively driven in a clockwise direction as likewise indicated by arrows. The wear ring 26, however, which receives its motivating torque by induced rotation picked up from frictional contact with the primary lap surface 20, will rotate in a counter-clockwise direction and thus perform its intended lap dressing function as previously described.

Since the cylinder assemblies 50 are held stationary,

2,8 5 the counter-clockwise rotation of their respective secondary lap plates will supply the necessary relative rotation between the two parts, and lapping of the shoulder 53 of the bolting flange 52 of each assembly will take place. It is obvious that continued and protracted lapping of the shoulder 53 of each cylinder assembly 50 will have an abrading effect on the primary lap surface 46 tending to cut or wear aa annular groove on that portion of the surface which is in contact with the shoulder. Thus, according to the present method, during any given lapping cycle as defined above, it is necessary that the lap plate 44 be reversed by turning the same upside down on the primary lap surface 20 and causing the underneath side of the plate, which has been freshly conditioned by virtue of its contact with the surface 20, to be directed upwardly and presented to the shoulder 53. Such reversal of each secondary lap plate 44 may be resorted to several times during each lapping cycle, that is, during the lapping of a single shoulder, the frequency of reversal depending, of course, upon the character and hardness of the surface undergoing lapping as well as upon the character of the lapping compound employed on the secondary lap surface 46.

The lapping compound used upon the secondary lap surfaces 46 is spread evenly over the upper surface of each lap plate 44 utilizing either a brush or a spatula for the purpose. A paste type of compound is preferred and, each time a reversal of the lap plate is made as described above, a fresh application of the abrasive compound is resorted to.

Reversal of secondary lap plates 44 is accomplished preferably by shutting down the machine to stop all rotation of the primary and secondary laps, and then removing cylinders 50 after raising rods 72 against the action of springs and then rotating the raised rods clear Of the plates 44. Said plates 44 may then be raised from lap surface 20, turned over, and then replaced on surface 20 with the teeth of gear 57 meshing with the teeth of gear 68. Cylinders 50 are then replaced on plates 44, pins 82 of rods 72 are placed in the bolt holes 54 and the machine is restarted.

It is to be noted from an inspection of Fig. 3 that the character of the teeth 70 on the hub gear 68 and the teeth 58 on the ring gears 57 is such that these gears are capable of various degrees of mesh. By such an arrangement, limited radial shifting of the secondary lap plates 44 is made possible utilizing the roller bar yokes 30 to effect the adjustment.

The annular configuration of secondary laps 44 may result, in the event of the need of a large opening 62 therein for the reception of a correspondingly large diameter protruding portion of a shouldered article, in the secondary laps approximating in size and shape the wear ring 26, and hence the secondary laps 44 may, under such circumstances, serve to condition primary lap surface 20 55 as to contour even while lap surface 20 is removing the groove formed in the secondary lap surface by the shouldered article. In such event, the wear ring 26 inay be dispensed with and the capacity of primary lap 18 may be increased by substituting for wear ring 26 an θθ additional secondary lap 44.

In accordance with conventional practice, the various lap surfaces 20 and 46 may be radially grooved as indicated at 100 to facilitate distribution and drainage of the abrading compound as well as to improve the lapping ¢5 Characteristics of the lap plates.

In Fig. 5 is shown a slightly modified form of secondary lap plate 144 which is capable of use in connection with the primary lap plate 18 and in substantially the same manner in which the lap plate 44 is used. Because of the γθ similarities between the lap plates 44 and 144, corresponding parts have been given similar reference numerals but of a higher order. Thus the ring gear is given the numeral 157, the central Opening in lap plate 144 is numbered 160 and the wall defining the opening 160 is 75

83,802 numbered 162. It is understood that the application, use and removal of secondary lap plates 144 from primary lap plate 18 are identical with those relating to lap plates 44. In lap plate 144 the peripheral regions have 5 been relieved on both sides as indicated at 101. The Overall weight of the lap plate 144 is lessened by this expedient and, additionally, during the lapping cycle the primary lap plate 18 is relieved of the burden of removing much excess material on the secondary lap plate 10 which is not subject to any abrading action by the shoulder 53 and which, as a consequence, is itself not worn.

It has been found that shoulders such as the shoulder 53 having bolt holes or other voids formed therein have a tendency for excess lapping to take place in the annuls lar regions of both laps occupied by the bolt holes or other voids, and it is believed that such a condition is the result of abrasive particles building up within the bolt holes themselves and exerting an undue abrading effect on the rim portions of these holes while compara20 tively starving the remaining portions of the lap surfaces. Another and perhaps additional cause for such excessive wear may, it is believed, be caused by oversize particles of abrasive making minute chips on the edge of the bolt hole rims as they slide under the shoulder initially 25 and before they are reduced in size by their abrasive action. In any event, it has been found that by drilling a series of holes through the lap plate as indicated at 103, with the holes preferably being the same in number and diameter as the number and diameter of the bolt holes 30 formed in the shoulder undergoing lapping, the excessive accumulation of abrasive is drained from the surface of the lap plate and the condition is remedied. The holes 103 are, of course, effective in this manner when the lap plate 144 is reversed.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. Only insofar 40 as the invention has particularly been pointed out in the accompanying claims is the same to be limited.