US3526057A

US3526057A - Art of precision surface abrading

Info

Publication number: US3526057A
Application number: US705505A
Authority: US
Inventors: Arthur J Hackman Jr
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-02-14
Filing date: 1968-02-14
Publication date: 1970-09-01
Anticipated expiration: 1987-09-01

Description

p 1, 19% A. J. HACKMAN, JR 3,526,057

ART OF PRECISION SURFACE ABRADING Filed Feb. 14, 1968 H/S A TTORNEY United States Patent 3,526,057 ART OF PRECISION SURFACE ABRADING Arthur J. Hackman, Jr., Grosse Pointe, Mich., assignor of one-half to Genevieve I. Hanseom (formerly Genevieve I. Magnuson), and one-half to Genevieve I. Hanscom, Robert Magnuson, and Lois J. Thomson (formerly Lois J. Duggan) as trustees of the estate of Roy M. Magnuson Filed Feb. 14, 1968, Ser. No. 705,505 Int. 'Cl. B24b 27/00 US. Cl. 51-1 12 Claims ABSTRACT OF THE DISCLOSURE Lap size changing means are provided comprising an axially tapered lap holding part which is capable of radially expanding or contracting, said lap holding part having means to hold in axially fast relationship to itself a lap which is capable of radially expanding or contracting with said lap holding part, means for moving an axially tapered arbor in respect to the axial taper on said lap holding part to radially expand or contract said lap holding part, means for maintaining said lap holding part axially stationary during its radial expansion or contraction so that said lap radially expands or contracts with said lap holding part without changing the relative axial position of said lap in respect to a workpart said lap is abrading, whereby the radial expansion or contraction of said lap can be accomplished while said lap is in the process of abrading said workpart.

My invention relates to the art of precision surface abrading by which is meant that art which is capable of producing finishes on metal workparts including geometries thereof to tolerances in the millionths of an inch.

In this art a lap and workpart are held in concentric frictional engagement and moved relative to each other so that the lap carries out a precision surface abrading operation on a surface of the workpart. Such relative movement comprises either relative rotation or relative axial reciprocation and wherever possible the two together simultaneously. Such relative axial reciprocation is preferably cyclic and oppositely equal and uniform in extent and speed. This type of relative axial reciprocation simultaneously with such relative rotation of a lap and workpart is best accomplished by the means and method disclosed in my US. Pat. 3,247,622 issued Apr. 26, 1966. (See also my copending application Ser. No. 544,940 now US. Pat. 3,462,887 issued Aug. 26,1969.) In each of these cases the precision surface abrading operation must be stopped periodically at intervals whenever the lap and the workpart become loose by reason of metal removal from said workpart. The radial dimensions of the lap must be changed to bring the lap surface into tight frictional engagement with the workpart surface, i.e. so that the lap exerts sufiicient pressure on the workpart to abrade the same, and this is accomplished during interruption of such precision surface abrading operation but while the lap and workpart are held in concentric frictional engagement with each other to prevent overchanging the radial dimensions of the lap. Following such radially changing in size of the lap the precision surface abrading operation is repeated until the lap surface needs to be made tight again with the workpart surface whereupon the precision surface abrading operation is again interrupted. The foregoing procedure of alternately carrying out a precision surface abrading operation and radially changing the size of the lap is continued until the workpart is finished to the desired dimensions including roundness, straightness and surface finish.

Patented Sept. 1, 1970 I have devised means and method which eliminate the foregoing procedure and obviate the need to interrupt the precision surface abrading operation in order to radially change the size of the lap to bring its lap surface into tight frictional engagement with the workpart surface. The provision of .such means and method by which the lap may be dimensionally changed radially while it is carrying out a precision surface abrading operation on the workpart is the principal object of my invention. Such object and the advantages of my invention will become apparent during the course of the following description taken in conjunction with the accompanying drawings in which:

FIGS.= l to 10 are views of lap size changing means and method embodying my invention; FIGS. 1 to 8 being views of a lap size changing internally and externally tapered hollow sleeve shown in operative relation with an helically slotted internally tapered lap and an extenrally tapered arbor; and FIGS. 9 and 10 being views of machine parts for changing the relative axial positions of said sleeve and arbor and hence of said lap while said lap is carrying out a precision surface abrading operation on a workpart.

Referring to the drawings in greater detail, 12 designates .the tapered arbor, the free end of which is uniformly tapered. A cylindrical enlargement having a transverse bore 14 therethrough is provided on the rear end of the arbor 12 which enlargement has formed thereon inwardly of the rear face thereof a threaded aperture 15. The purpose of the bore 14 and aperture 15 will appear later. The tapered free end of the arbor 12 carries the size changing hollow sleeve which is designated 16. The sleeve 16 has an annular body to the free end of which is uniformly double tapered corresponding to the taper on the arbor 12, i.e. it is provided with both an internal taper and an external taper of the same direction. A cylindrical enlargement, the purpose of which will appear, is provided on the rear end of the sleeve .16. The double tapered free end of the sleeve 16 is provided with a through-slot construction through its annular wall so that it will change its dimensions radially in accordance with its relative axial position on the arbor 12. In the instance the free end of the sleeve 16 is split axially by four circumferentially equally spaced through slots 18 which extend logitudinally over the greater part of the length of the free end of the sleeve 16. The free end of the sleeve 16 carries an internal lap 20 having an annular body, the external surface of which is cylindrical or straight for lapping internal surfaces of workparts. The lap 20 is of the smooth surfaced type which employe a free abrasive compound as mentioned in said US. Pat. 3,247,622 and in said application S.N. 544,940 now US. Pat. 3,462,887 issued Aug. 26, 196 9. The lap 20 may be provided with different forms on its external surface other than the cylindrical or straight form shown. Such external surface of the lap 20 carries a diamond pattern of degrees phase shifted helical grooves 21 to render more effective its lapping action with such free abrasive compound. In spite of such patterned external surface the lap 20 is still characterized as a smooth surfaced lap as shown and described in said prior US. Pat. 3,247,622 in contrast to a diamond abrasive coated lap as shown and described in said prior co-pending application S.N. 544,940 now US. Pat. 3,462,887 issued Aug. 26, 1969. The internal surface of the lap 20 is tapered corresponding to the taper on the arbor 12. The body of the lap 20 has a through-slot construction through its annular wall preferably extending the length of the lap which, in the instance, is in the form of a helical slot 22 spiraling about 360 degrees from one end of the lap to the other. The lap 20 may be straight slotted in certain instances.

Shifting of the axial position of the arbor 12 in respect to the sleeve 16 changes the radial dimensions of the sleeve 16 and hence of the lap as no relative movement occurs between the lap 20 and the sleeve 16. As the arbor 12 is shifted axially within the sleeve 16 from the position shown in FIG. 1 to that in FIG. 2 it carries to lap 20 therewith and the radial dimensions of the latter are increased. As the arbor 12 is axially shifted within the sleeve 16 from the position shown in FIG. 2 to that in FIG. 1 the radial dimensions of the lap 20 decrease. Axial shifting of the arbor 12 within the sleeve 16 automatically while the lap 20 is carrying out a precision surface abrading operation on a workpart may be accomplished, eg, via the machine parts shown in FIGS. 9 and 10. In these figures parts of a precision surface abrading machine, such as the abrading machine described and claimed in my said US. Pat. 3,2A7,622, are shown in which W is a workpart carried on a workholder (not shown), such as the workholder 105 shown in said Pat. 3,247,622 (the workholder 105 must be modified as explained hereinafter), and supported for cyclic axial reciprocation in the tailstock 18 of said abrading machine. The headstock of said abrading machine is designated 23 in these figures and supports via bearings 25 a rotatably driven shaft 24 which carries the arbor 12 so that the sleeve 16 and the lap 20 on the free end thereof rotates within the cyclicly axially reciprocating workpart W. The shaft 24 is provided with a bore 26 which extends inwardly therein from its rear in which bore 26 the arbor 12 is slidably supported via the enlargement on the rear end thereof. The arbor 12 is movably axially of the shaft 24 by a double acting hydraulically or pneumatically operated ram 28 the front end of which is provided with a threaded stud 29 threadably engaged in the aperture 15. Rotary drive from the shaft 24 to the arbor 12 is transmitted by a rod 30 which extends through the bore 14 in the enlargement on the rear end of said arbor 12 and into diameterically disposed through-slots 32 in the annular portion of the shaft 24 surrounding the bore 26. The rod 30 moves in the slots 32 while it transmits such rotary drive while the arbor 12 is being moved by the ram 28 axially in respect to the shaft 24. The front end of the shaft 24 captures the sleeve 16 against axial movement relative thereto via a bore 34 in which the enlargement on the rear end of the sleeve .16 is disposed and via a washer 33 and a cover plate 35 which is bolted by fasteners 36 to the front end of the shaft 24. The lap 20 may be removed from the sleeve 16 as often as desired to change laps but the sleeve 16 cannot be removed from the arbor 12 without unfastening the cover plate 35 and removing the washer 33. The rotary drive applied to the arbor 12 is transmitted to the sleeve 16 by virtue of its frictional engagement with said sleeve 16. (The sleeve 16 is free to rotate in respect to the shaft 24 which feature is utilized in the event the lap 20 becomes too tight and does not rotate in respect to the Workpart W which event will hold the sleeve 16 fast causing the arbor 12 to slip inside the sleeve 16.) The sleeve 16 in turn rotatably drives the lap 20 by virtue of the frictional engagement of the latter with said sleeve 16. While the lap 20 is carrying out a precision surface abrading operation on the workpart W its radial dimensions may be increased by movement of the ram 28 (and hence of the arbor .12 and the lap 20) axially and outwardly of the shaft 24 in the direction from the position shown in FIG. 9 to that in FIG. 10. Movement of the ram 28 whether actuated by pneumatic or hydraulic power must be under manual control for the operator of the lapping machine to feel the tightness of the lap 20 within the workpart W. Such increase of the radial dimensions of the lap 20 is accomplished periodically during such abrading operation while the workpart W is cyclically reciprocated over the lap 20 and in such increments as to compensate for the amount of metal removal from the internal bore of the workpart W to insure that the lap 20 exerts sufficient pressure on the workpart W to abrade the same. The workholder for the workpart W must be modified from the workholder shown in said US. Pat. 3,247,622 to eliminate the bushing in its barrel 122 so that the arbor 12 can project through such barrel 122 without any interference. With the means and method described there is no need to stop the lapping machine to adjust the size of the lap as had to be done heretofore every 5 seconds or so. Now the lap is initially expanded by axially moving the arbor 12 in respect to the sleeve 16 until the lap 20 is tight within the bore of the workpart W. The lapping machine is then started and the lap 20 is expanded periodically every 2 or 3 seconds or so to maintain the lap 20 in tight frictional engagement with the workpart W while the machine is operating and while the lap 20 is carrying out a precision surface abrading operation on the workpart W. The lapping machine is then stopped: (a) at the end of the predetermined lapping time if the workpart W is a production workpart on which a time cycle has been worked out; or (b) after a predetermined amount of lap expansion if the lapping machine is equipped with an indicator to determine the relative axial position of the lap 20 and the arbor 12; or (c) if the lapping machine is not so equipped, to gage the workpart W. In the case of the ram 28 its axial position relative to the shaft 24 (and hence the axial position of the lap 20 and the sleeve 16 relative to the arbor 12) can be indicated by suitable indicator means (not shown) in which case the lap 20 may be expanded every 20 millionths of an inch or so of expansion in diameter while the lap 20 is rapidly rotating within the cyclicly reciprocating workpart W carrying out a precision surface abrading operation on the latter. If a handwheel similar to the handwheel 29 in said US. Pat. 3,247,622 were employed in lieu of the ram 28 to axially move the arbor 12 relative to the shaft 24, and to the sleeve .16 the indicator 35 shown in said US. Pat. 3,247,- 622 could be used without much modification to indicate the amount of lap expansion.

It will thus be seen that there has been provided by my present invention lap size changing means and method in which the advantages hereinabove set forth together with many other thoroughly practical advantages have been successfully achieved. While a preferred embodiment of my invention has been shown and described it is to be understood that variations and changes may be resorted to without departing from the spirit of my invention as defined by the appended claims. For example, my invention may be applied by the principles herein taught to radially change the dimensions of an external lap while it is carrying out a precision surface abrading operation on a workpart.

What is claimed is:

1. In the art of precision surface abrading, lap size changing means comprising an axially tapered lap holding part which is capable of radially expanding or contracting, said lap holding part having means to hold in axially fast relationship to itself a lap which is capable of radially expanding or contracting with said lap holding part, an axially tapered arbor means for moving said axially tapered arbor in respect to the axial taper on said lap holding part to radially expanding or contract said lap holding part, means for maintaining said lap holding part axially stationary during its radial expansion or contraction so that said lap radially expands or contracts with said lap holding part without changing the relative axial position of said lap in respect to a workpart said lap is abrading, whereby the radial expansion or contraction of said lap can be accomplished while said lap is in the process of abrading said workpart.

2. Lap size changing means as claimed in claim 1 in which said lap holding part is doubly axially tapered and said lap is held axially fast in respect to said lap holding part by the other axial taper thereon than the one used to radially expand or contract said lap holding part.

3. Lap size changing means as claimed in claim 2 in which said lap holding part is both internally and externally axially tapered and is radially expanded or contracted via its internal taper and holds said lap axially fast via its external taper.

4. Lap size changing means as claimed in claim 3 in which said lap holding part has such an annular wall thickness as to be in form a sleeve, said sleeve being longitudinally slotted inwardly from its front end and having holding means on its rear end by which it can be held axially stationary during its radial expansion or contraction.

5. Lap size changing means as claimed in claim 1 further comprising means for applying a rotatable driving force to said arbor to rotatably drive said lap holding part and said lap held thereby.

6. In the art of precision surface abrading, lap size changing means comprising a lap holding part which is both internally and externally axially tapered and is capable of being radially expanded or contracted via one of said tapers, said lap holding part capable of holding in axially fast relationship thereto via the other of said tapers a lap capable of radially expanding or contracting with said lap holding part, said lap holding part having means by which it can be held axially stationary while it is being radially expanded or contracted so that said lap .does not change its axial position in relationship to the workpart it is abrading whereby the radial expansion or contraction of said lap can be accomplished while said lap is in the process of abrading said workpart.

7. Lap size changing means as claimed in claim 6 in which said lap holding part is radially expanded or contracted via its internal taper and holds said lap axially fast via its external taper.

8. Lap size changing means as claimed in claim 7 in which said lap holding part has such an annular wall thickness as to be in form a sleeve, said sleeve being longitudinally slotted inwardly from its front end and having holding means on its rear end by which it can be held axially stationary during its radial expansion or contraction.

9. In the art of precision surface abrading, lap size changing method comprising holding a lap in axially fast relationship to an axially tapered lap holding part, axially moving an axially tapered arbor in respect to the axial taper on said lap holding part to radially expand or contract said lap holding part while maintaining said lap holding part axially stationary so that said lap radially expands or contracts with said lap holding part lap holding part axially stationary so that said lap in respect to a workpart said lap is abrading, whereby the radial expansion or contraction of said lap can be accomplished while said lap is in the process of abrading said workpart.

10. Lap size changing method as claimed in claim 9 in which said lap is held axially fast in respect to said lap holding part by an axial taper on said lap holding part by an axial taper on said lap holding part other than the one used to radially expand or contract said lap holding part.

11. Lap size changing method as claimed in claim 10 in which said lap holding part is radially expanded or contracted via an internal taper thereon and in which said lap is held axially fast on said lap holding part via an external taper thereon.

12. Lap size changing method as claimed in claim 11 in which a rotatable driving force is applied to said arbor to rotatably drive said lap holding part and said lap held thereby.

References Cited UNITED STATES PATENTS 1,583,010 5/1926 Richardson 51-1 2,044,474 6/1936 Groetchen 51-1 2,767,676 10/1956 Johnson et al. 269-481 3,247,622 4/1966 Hackman 51--l65 OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 51-72 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,526,057 September 1, 1970 Arthur J. Hackman, Jr.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column Column 2, line 49, "employe" should read employs line 3, line 31, "movably" should read moveable Column 4, 60, after "arbor" insert a comma; line 62, "expanding" should read expand Column 6, line 8, "lap holding part axially stationary so that" should read without changing the relative axial position of line 17, cancel "by an axial taper on said lap holding part".

Signed and sealed this 16th day of March 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer