US3916581A

US3916581A - Method for dressing grinding wheels

Info

Publication number: US3916581A
Application number: US419997A
Authority: US
Inventors: Francis L Messier
Original assignee: Warner and Swasey Co
Current assignee: Western Atlas Inc
Priority date: 1973-11-29
Filing date: 1973-11-29
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04

Abstract

An improved method for dressing the periphery of a grinding wheel having a circular main surface which extends transversely to a circular shoulder. To dress the main surface of the grinding wheel, an axially extending surface on a first dressing wheel is moved into engagement with the main surface of the grinding wheel. To dress the shoulder surface, an axially extending surface on a second dressing wheel is moved into engagement with the shoulder surface of the grinding wheel. The two dressing wheels are mounted on a common carriage or slide which is moved relative to the grinding wheel by a three-position motor assembly. The three-position motor assembly and dressing wheel slide are both mounted on a base slide which is moved toward and away from the grinding wheel by another motor. The two dressing wheels are mounted for rotation about transversely extending axes and are positioned relative to each other in such a manner that when the first dressing wheel is in engagement with the main surface of the grinding wheel, the second dressing wheel is spaced from the shoulder surface of the grinding wheel. Similarly, when the second dressing wheel is in engagement with the shoulder surface of the grinding wheel, the first dressing wheel is spaced from the main surface of the grinding wheel.

Description

United States Patent Messier Nov. 4, 1975 METHOD FOR DRESSING GRINDING [57] ABSTRACT WHEELS An improved method for dressing the periphery of a [75] Inventor: Francis L. Me sie Worcester, grinding wheel having a circular main surface which Mass. extends transversely to a circular shoulder. To dress the main surface of the 'ndin wheel, an axiall ex- [73] Asslgnee: The Warner swasey Company tending surface on a first d ressi g wheel is moved into Cleveland Ohm engagement with the main surface of the grinding [22] Filed: Nov. 29, 1973 wheel. To dress the shoulder surface, an axially extendin surface on a second dressin wheel is moved [21] Appl' 419997 into eigagement with the shoulde surface of the grinding wheel. The two dressing wheels are mounted [52] US. Cl. 51/283; 125/11 CD on a common c g or slide which is moved relative [51] Int. Cl. B24B 1/00 t the g n ng e l y a thr -p sition m tor ass m- [58] Field of Search 125/11 R, 11 CD; 51/5, y- The three-position m r em y n r ing 51/105 SP 283 wheel slide are both mounted on a base slide which is moved toward and away from the grinding wheel by [56] References Cit d another motor. The two dressing wheels are mounted UNITED STATES PATENTS for rotation about transversely extending axes and are 3 407 800 10/1968 Home 125,11 R positioned relative to each other in such a manner that 3553893 H1971 Sta 51 /5 D when the first dressing wheel s in engagement with 3:581:730 6/1971 Boyd "fig CD the main surface :of the grinding wheel, the second 3,678,916 7,1972 Fujii 125,11 CD dressing wheel IS spaced from the shoulder surface of 3,633,385 8/1972 Kikuchi N 125/11 CD the grinding wheel. Similarly, when the second dress- 3,747,5s4 7 1973 Kikuchi 125/11 co ing wheel is in engagement with the shoulder surface 3,822,689 7/1974 Oshima 125/11 DF X of the grinding wheel, the first dressing wheel is Primary ExaminerHarold D. Whitehead spaced from the main surface of the grinding wheel.

5 Claim, 12 Drawing Figures U.S. Patent Nov. 4, 1975 Sheet 1 of4 3 ,916,581

US. Patent Nov. 4, 1975 Sheet 2 of4 3,916,581

WMQ

US. Patent Nov. 4, 1975 Sheet 3 of4 3,916,581

as 26 9o FTE. 5

U.S. Patent Nov. 4, 1975 Sheet4 0f4 3,916,581

METHOD FOR DRESSING GRINDING WHEELS BACKGROUND OF THE INVENTION This invention relates to an improved method and apparatus for dressing the periphery of a grinding wheel having a circular main surface and a circular shoulder surface which extends transversely to the main surface.

Grinding wheels which are utilized to finish parts 0 utilized to finish a radially extending surface on the part.

A known dressing wheel having a cylindrical surface is utilized to dress the main surface of'the grinding wheel. A radially extending surface of the known dressing wheel is utilized to dress the shoulder surface of the grinding wheel. The relatively large contact area between, the shoulder surface of the grinding wheel and the radially extending surface of the dressing wheel requires the application of relatively large forces to dress the wheel. In an effort to oyercome the problems resulting from the utilization of such a dressing wheel, it has been suggested to utilize a dressing wheel which is rotatable upon an axis which is different from the axis about which the workpiece is rotated and which has frustro-conical dressing surfaces in the manner disclosed in U.S. Pat. No. 3,526,058.

SUMMARY OF THE PRESENT INVENTION The present invention provides an improved method for dressing the periphery of a grinding wheel having a circular main surface and a circular shoulder surface extending transversely to the main surface by utilizing different dressing wheels to dress these two surfaces. Thus, a first or main dressing wheel is utilized to dress the main surface of the grinding wheel. -A second or shoulder dressing wheel is utilized to dress a shoulder surface of the grinding wheel. By utilizing separate dressing wheels to dress the surfaces of the grinding wheel, the contact area between each of the surfaces of the grinding wheel and the two dressing wheels is minimized to tend to optimize the finish obtained on the surfaces of the grinding wheel with the application of relatively low forces to the dressing wheels.

The two dressing wheels may be mounted on a common slide or carriage and rotated about transversely extending axes. The common carriage is advantageously moved by a three-position motor assembly. Upon operation of this motor assembly from a retracted condition to a first extended condition the main or first grinding wheel is moved axially alonga path extending parallel to the main surface of the grinding wheel. Upon operation of the'motor assembly to a second extended position, an axially extending outer surface of the second or shoulder dressing wheel is moved radially into engagement with the shoulder surface of the grinding wheel.

Accordingly, it is an object of this invention to provide a new and improved method for dressing the periphery of a grinding wheel having a circular main surface and acircular shoulder surface by engaging the main surface of the grinding wheel with a first dressing 2 wheel and engaging the shoulder surface of the grinding wheel with a second dressing wheel.

. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and features of the present invention will become more apparent upon a v consideration of the following description taken in con:

nection with the accompanying drawings wherein:

FIG. 1 is a plan view of a grinding machine having a wheel dressing arrangement which is constructed and operated in accordance with the present invention, a main dressing wheel being shown in engagement with a main surface of the grinding wheel;

FIG. 2 is an elevational view, taken generally along.

the line 2-2 of FIG. 1, and illustrating the relationship between a shoulder dressing wheel, the main dressing wheel, and a carriage or slide on which the dressing wheels are rotatably mounted; FIG. 3 is an enlarged, partially schematized illustration depicting the relationship between a three-position motor assembly and control valves for effecting operation of the motor assembly to move the dressing wheel slide, the motor assembly being shown in a retracted condition;

FIG. 4 is an illustration of the motor assembly of FIG. 3 in a partially extended condition in which the main dressing wheel engages the main surface of the grinding wheel; 7 FIG. 5 is an illustration of the motor assembly of FIGS. 3 and 4 in a fully extended condition in which the shoulder dressing wheel engages a shoulder surface of the grinding wheel;

FIG. 6 is a schematic illustration depicting the relationship between the main and shoulder dressing wheels when they are in an initial retracted condition; FIG. 7 is a schematic illustration of the dressing of the main surface of the grinding wheel; FIG. 8 is a schematic illustration depicting the relationship between the main dressing wheel and the grinding wheel at the end of a wiping stroke across the main surface of the grinding wheel;

FIG. 9 is a schematic illustration depicting the mai and shoulder dressing wheels in the retracted condition after completion of the wiping stroke;

FIG. 10 is a schematic illustration depicting the dressing of the shoulder surface of the grinding wheel; FIG. 11 is a schematic illustration depicting the main and shoulder dressing wheels in the retracted condition upon completion of a dressing operation; and,

FIG. 12 is a schematic illustration of control circuitry associated with the motor assembly and control apparatus of FIG. 3.

DESCRIPTION OF ONE SPECIFIC PREFERRED EMBODIMENT OF THE INVENTION A grinding machine 20 is illustrated in FIG. I and includes a wheel dressing apparatus 22 which is constructed and operated in accordance with the present invention to dress a main surface 24 and shoulder surface 26 of a grinding wheel 28. The wheel dressing apparatus 22 includes a first or main dressing wheel 32 which is utilized to dress the main surface 24 of the grinding wheel 28 and a second orshoulder dressing wheel 34 which is utilized to dress the shoulder surface 26 of the grinding wheel. The two

dressing wheels

32 and 34 are rotatably mounted on a common slide or carriage 38 which is movable relative to a base slide 40 by a three-position motor assembly 42. The base slide 3 40 is movable relative to a base or bed 44 of the grinding machine by a piston and cylinder type motor 46 (illustrated schematically in FIG. 1) to position

dressing wheels

32 and 34 along a path extending perpendicular to an axis 48 of rotation of the grinding wheel 28.

When the transversely extending main and

shoulder surfaces

24 and 26 of the grinding wheel 28 are to be dressed, the main surface is dressed by the wheel 32 before the shoulder surface is dressed by the wheel 34. To dress the main surface 24, the main dressing wheel 32 is moved from the retracted position of FIG. 6 to the operating position of FIG. 7 under the combined influence of the three-position motor assembly 42 and the base slide motor 46. The base slide motor 46 is activated to move the dressing wheel 32 sidewardly toward the grinding wheel 28. contemporaneously therewith, the three-position motor assembly 42 is operated from the initial or retracted condition of FIG. 3 to the partially extended condition of FIGS. 1 and 4 to shift the wheel slide 38 and move the main dressing wheel 32 axially relative to the main or face surface 24 of the grinding wheel 28.

Before a cylindrical outer surface 52 of the dressing wheel 32 is moved into engagement with the main surface '24 of the grinding wheel 28, the dressing wheel 32 is brought up to a predetermined rotational speed by a drive arrangement which includes a sheave 56 which is driven by suitable belts 58. Of course, the grinding wheel 28 is also rotated about its central axis 48 by a suitable drive arrangement. As the grinding wheel 28 and main dressing wheel 32 are rotated, the main surface 24 of the grinding wheel is dressed in a known manner. It should be noted that the shoulder dressing wheel 32 is spaced from the shoulder surface 26 of the grinding wheel 28 while the main surface 24 is to be dressed.

When the main surface 24 of the grinding wheel 28 has been dressed to a desired surface finish, the motor assembly 42 is operated to shift the dressing wheel 32 axially from the position shown in FIG. 7 to the position shown in FIG. 8 to wipe the main surface 24 of the dressing wheel 28. This is accomplished by operating the motor assembly 42 from the partially extended condition of FIG. 4 to the retracted condition of FIG. 3. As this occurs the dressing wheel slide 38 (FIG. 1) is shifted along a path extending parallel to the main surface 24 of the grinding wheel 28 to move the cylindrical outer surface 52 of the dressing wheel 32 axially along the main surface of the grinding wheel to thereby wipe the main surface of the grinding wheel in a known manner.

Once the main surface 24 of the grinding wheel 26 has been dressed, the shoulder surface 26 of the grinding wheel is dressed by the dressing wheel 34. Upon completion of the wiping stroke of the main dressing wheel 32, the main dressing wheel and shoulder dressing wheel 34 are shifted from the positions shown in FIG. 8 to the retracted positions of FIG. 9. This is accomplished by operating the base slide motor 46 (FIG. 1) to move the base slide 40 and the dressing wheel slide 38 away from the grinding wheel 28. As this occurs, the shoulder dressing wheel 34 is moved into radial alignment with the shoulder surface 26 of the grinding wheel 28 (see FIG. 9).

The three-position motor assembly 42 is then operated from the retracted condition to FIG. 3 to a second operating or fully extended condition of FIG. 5. This moves the shoulder dressing wheel 34 radially toward the shoulder surface 26 along the path extending perpendicular to the shoulder surface 26. As this occurs, a cylindrical outer surface 64 on the shoulder dressing wheel 34 moves into abutting engagement with the shoulder surface 26 on the grinding wheel 28.,It should be noted that the main dressing wheel 32 is spaced apart from the grinding wheel 28 and is disposed axially to the left (as viewed in FIGS. 611) of the main surface grinding position of FIG. 7 when the shoulder dressing wheel 34 engages the grinding wheel.

The shoulder grinding wheel 34 is rotated by a fluid motor 68 (see FIGS. 1 and 2) about an axis 70 which extends perpendicular to and intersects an axis 72 of the main dressing wheel 34 (FIG. 7). The motor 68 accelerates the dressing wheel 34 to a predetermined speed before it is brought into engagement with the shoulder surface 26 of the grinding wheel 28. The fluid motor 68 continues to rotate the dressing wheel 34 about its axis 70 at the desired wheel dressing speed simultaneously with rotation of the grinding wheel 28 about its central axis 48 to dress the shoulder surface 26 of the grinding wheel 28 in a known manner.

Once the shoulder surface 26 of the grinding wheel 28 has been dressed to the desired surface finish, the three-position motor assembly 42 is operated from the fully extended condition of FIG. 5 to the retracted condition of FIG. 3 to move the shoulder dressing wheel 34 to the retracted position of FIG. 11. At this time the shoulder dressing wheel 34 and main dressing wheel 32 are both in the fully retracted or initial condition of FIG. 6 and are spaced apart from the grinding wheel 28; Therefore, the dressing

wheels

32 and 34 will not interfere with normal operation of the grinding wheel 28. Although the main surface 24 of the grinding wheel 28 has been shown as having a larger surface area than the shoulder 26, it is contemplated that under certain circumstances the shoulder 26 may have a greater surface area than the main surface 24. Depending upon the configuration of the parts to be finished by the grinding machine 20, the grinding

surfaces

24 and 26 could 'have a configuration other than the illustrated frustro-conical configuration and could have an angle of intersection other than the illustrated right angle. It is also contemplated that under certain circumstances it' may-be desirable to simultaneously dress both the main surface 24 and shoulder surface 26 of the grinding wheel 28 with the two dressing

wheels

32 and 34 rather than dressing them sequentially in the manner illustrated schematically in FIGS. 6-11.

The three-position motor assembly 42 includes a cylinder assembly 74 (see FIG. 3) which defines an operating chamber 76 having a relatively large diameter main portion 78 and a relatively small diameter secondary portion 80. A pair of

pistons

82 and 84 are fixedly interconnected at a threaded connection 88 and cooperate with a movable third piston 90. The fixed

piston elements

82 and 84 are connected with the wheel slide 38' by a suitable connection 94 and an outer'end of 'a piston rod 96.

When the motor assembly 42 is in the retracted condition of FIG. 3, an annular stop portion 100 of the piston 82 is disposed in abutting engagement with an annular end face 102 of the movable piston 90. An end surface 104 of the movable piston is disposed in abutting engagement with a circular end wall 106 of the cylinder assembly 74. Passages 108 connect a circular recess 1 10 within the movable piston 90 with a passage 112 extending through the cylinder assembly 74. It

should be noted that when the motor assembly 42 is in the retracted condition of FIG. 3, an annular end surface 114 on the piston 84 is spaced from an annular inner surface 116 of the movable piston 90.

To operate the motor assembly 42 from the retracted condition of FIG. 3 to the partially extended condition of FIG. 4, a solenoid SI-IA (see FIG. 3) is energized to shift a valve spool 120 toward the right (as viewed in FIG. 3). This movement of the valve spool 120 ports fluid under pressure through a valve passage 122 to a passage 124 through the cylinder 74 to a pressure chamber 126 formed between the

piston elements

82 and 90. The application of fluid pressure against an annular operating or end surface 130 on the piston 82 causes the piston to move leftwardly from the position shown in FIG. 3 to the position shown in FIG. 4. It-

should be noted that the fluid pressure in the chamber 126 is also applied against the end face 102 of the movable piston 90 to press the movable piston firmly against the end surface 106 of the cylinder assembly 74. Therefore, when the annular end surface 114 of the piston element 84 engages the surface 116 on the piston 90, movement of the piston 82 from the position shown in FIG. 4 is blocked. The cooperation between the movable piston 90 and the piston element 84 enables the motor assembly 42 to accurately position the wheel slide 38 with the main dressing wheel 32 in the position illustrated in FIGS. 1 and 7 to enable the dressing wheel 32 to dress the main surface 24 of the grinding wheel 28.

When the motor assembly 42 is to be operated from the partially extended condition of FIG. 4 to the retracted condition of FIG. 3 to thereby move the dressing wheel 32 through a wipe stroke, a solenoid SHB is energized to shift the valve spool 120 toward the left (as viewed in FIG. 3). This causes fluid under pressure to be ported through a valve passage 134 and a passage 136 of the cylinder assembly 74 to an operating chamber 138. The application of fluid pressure against an annular end face 140 of the piston 82 moves the piston toward the right from the position shown in FIG. 4 to the position shown in FIG. 3. It should be noted that at this time the chamber 1 is connected to drain through a valve spool 144 and that the chamber 126 is connected to drain through the valve spool 120.

When the motor assembly 42 is to be operated from the retracted condition of FIG. 3 to the fully extended condition of FIG. 5, a solenoid 8HB is energized to move the valve spool 144 toward the left (as viewed in FIG. 3). This ports fluid pressure through a valve passage l46 to the operating chamber 1 10. At this time the solenoids 511A and SHB are deenergized so that the operating

chambers

126 and 138 are connected with drain or reservoir through passages in the valve spool 120. Therefore, the relatively high fluid pressure in the chamber 110 causes the movable piston 90, piston 84 and piston 82 to move leftwardly (as viewed in FIG. 3) until the end face 102 of the piston 90 engages an annular stop surface 150 formed on a cylindrical wall of the cylinder assembly 74 (see FIG. 5). The fluid pressure in the operating chamber 110 causes the piston 84 to continue moving until the surface 114' on the piston element 84 engages the surface 116 on the piston 90. At this time the motor assembly 42 is in the fully extended condition of FIG. 5 and the shoulder dressing wheel 34 is in the postion shown .in FIG. 10. It should be noted that the stop' surface 150 accurately locates the movable piston 90 and that the engagement between the 6

surface

114 and 116 on the pistons and 84 function to accurately position the dressing wheel slide 38 for a shoulder dressing operation.

When the shoulder surface 26 of the grinding wheel 28 has been dressed, the motor assembly 42 is operated from the fully extended condition of FIG. 5 to the retracted condition of FIG. 3 to move the dressing wheel 34 from the position shown in FIG. 10 to the position shown in FIG. 11. To accomplish this, the solenoid 8118 is deenergized and the valve spool 144 is moved toward the right (as viewed in FIG. 3) under the influence of a biasing spring 156 to connect the operating chamber with drain. The solenoid SHB is then energized to connect the operating chamber 138 with high pressure line 158 which is supplied with fluid under pressure from a pump 160 driven by a motor 162. The relatively high fluid pressure in the chamber 136 moves the piston 82 toward the right (as viewed in FIG. 5) to bring the stop portion 1 10 of the piston into abutting engagement with the movable piston 90. Continued rightward movement of the piston 82 moves the movable piston 90 away from the annular stop surface 150 to the position shown in FIG. 3. The solenoid SHB is then deenergized and biasing

springs

166 and 168 center the valve spool 120 so that both of the operating

chambers

126 and 138 are connected with drain.

Control circuitry 174 for effecting operation of the wheel dressing apparatus 22 through a dressing cycle is illustrated schematically in FIG. 12. When a wheel dressing cycle is to be undertaken, the motor assembly 42 and associated control valves are in the condition shown in FIG. 3. In addition, the base slide motor 46 is retracted as shown in FIG. 3 so that the main and

shoulder dressing wheels

32 and 34 are in the position illustrated schematically in FIG. 6. A switch 176 is closed to energize a motor 178 for driving the sheave 56 (FIG. 1) and main dressing wheel 32.

When a start button 180 (FIG. 12) is depressed to initiate the beginning of a wheel dressing cycle, a relay 182 is energized. Energization of the relay 182 closes holding contacts 184 to maintain the relay in an energized condition even though the start 180 is released. Energization of the relay 182 effects operation of a valve 186 (FIG. 3) to port fluid under pressure through a valve passage 190 to the head end of the base slide motor 46. This extends the motor 46 to move the base slide 40 toward the grinding wheel 28 along a path extending perpendicular to the axis of rotation of the grinding wheel. Thus, upon enerigzation of the relay 182, its normally open contacts 194 are closed to energize a 4H3 solenoid and shift the valve spool 186 toward the left (as viewed in FIG. 3).

In addition to effecting operation of the base slide motor 46, energization of the relay 182 (FIG. 12) causes its normally open contacts 196 to close and effect energization of the SHA solenoid. Energization of the 511A solenoid causes the valve spool 120 to be shifted toward the right (as viewed in FIG. 3) to port fluid under pressure to the operating chamber 126. This fluid pressure causes the piston 82 to move from the retracted position of FIG. 3 to the partially extended position of FIG. 4 in the manner previously explained. The combined operation of the three-position motor assembly 42 and the base slide motor 46 results in movement of the main dressing wheel 32 from the retracted position of FIG. 6 to the operating position of FIG. 7 in which the dressing wheel 32 is effective to dress the main surface 24 of the grinding wheel 28 in a 7 known manner.

When the main dressing wheel 32 is to be moved through a wipe stroke from the position shown in FIG. 7 to the position shown in FIG. 8, a wipe button 200 (FIG. 12) is manually actuated to energize a relay 202 and initiate operation of a timer 204. Actuation of the relay 202 closes its normally open holding contacts 206. Simultaneously therewith, normally closed contacts 208 of the relay 202 are opened to deenergize the solenoid SHA. Normally open contacts 212 of the relay 202 are closed to energize the solenoid SHB.

Energization of the solenoid SHB causes the valve spool 120 to shift to the left from the position shown in FIG. 3 to port fluid under pressure to the operating chamber 138. The fluid pressure in the operating chamber 138 is applied against the end face 140 of the piston 82 to move the piston fromm the partially extended position of FIG. 4 to the retracted position of FIG. 3. This movement of the piston 82 is parallel to the main surface 24 and the axis of rotation 72 of the main dressing wheel 32. The movement of the piston 82 is transmitted to the dressing wheel slide 38 through the connection 94 to move the main dressing wheel 32 across the main surface 24 of the grinding wheel 28 with a wiping action.

The timer 204 times out after the elapse of a sufficient period of timem to enable the main dressing wheel 32 to move through the wiping stroke. When this occurs, normally

closed timer contacts

216 and 218 and 220 (FIG. 12) are opened. Opening of the timer contacts 216 deenergizes the 4HB solenoid to enable a biasing spring 224 (see FIG. 3) to shift the valve spool 186 back to the position shown in FIG. 3 in which fluid is ported to the rod end of the base slide motor 46 to retract the slide motor. This moves the base slide 40 away from the grinding wheel 28 to shift the dressing

wheels

32 and 34 to the positions illustrated schematically in FIG. 9.

Opening of the timer contacts 218 and 220 interrupts the circuit for energizing the relay 202 and the solenoid SHB. Deenergization of the solenoid H8 allows the biasing springs 166 and 168 to shift the valve spool to the neutral position of FIG. 3. This connects the operating

chamber

126 and 138 of the now retracted motor assembly 42 with drain. If the shoulder surface is not to be dressed, a stop button 225 can be actuated at this time to interrupt the wheel dressing operation.

Assuming that the shoulder surface 26 is to be dressed, a shoulder grind button 228 is closed. This completes a circuit for energizing the 811B relay to effect a shifting of the valve spool 144 toward the left (as viewed in FIG. 3). This movement of the valve spool 144 ports fluid under pressure to the operating chamber 110 and effcts operation of the motor assembly 42 to the fully extended condition of FIG. 5. As the motor assembly 42 is extended, the shoulder dressing wheel 34 is moved radially toward the shoulder surface 26 along a path extending perpendicular to the shoulder surface and parallel to the main surface 24. It should be noted that upon previous actuation of the start switch 180 and energization of the relay 182, contacts 232 of the relay 182 are closed to effect energization of a 9118 solenoid (FIG. 3).

The previous energization of the 911B solenoid shifted a valve spool 236 toward the left (as viewed in FIG. 3) against the influence of a biasing spring 238 to connect the dressing wheel drive motor 68 with fluid under pressure through a valve passage 240. The motor 68 quickly brings the shoulder dressing wheel 34 up to speed. Therefore as the motor assembly 42 is operated from the retracted condition of FIG. 3 to the extended condition of FIG. 5, the rotating dressing wheel 34 is brought into engagement with the shoulder surface 26 on the rotating grinding wheel 28. When the shoulder surface 26 has been dressed, the shoulder grind button 228 is released and the solenoid 811B is deenergized. This enables a biasing spring 156 to shift the valve spool 144 back to the position shown in FIG. 3 in which the chamber is connected with drain.

After the main and shoulder surfaces 24 and 26 on the grinding wheel 28 have been dressed, the stop button 225 is actuated. Actuation of the stop button 225 interrupts the circuit for energizing the relay 182 so that its normally open holding contacts 184 are opened. In addition, contacts 232 of the relay 182 are open to deenergize the solenoid 911B so that the valve spool 236 is returned to the position illustrated in FIG. 3 by the biasing spring 238. This interrupts the flow of fluid to the motor 68 and rotation of the shoulder dressing wheel 34.

As the stop button 225 is actuated, a circuit to energize a relay 254 is completed. Energization of the relay 254 closes its contacts 256 to complete a circuit for energizing SHB solenoid. Energization of the SHB solenoid causes the valve spool to be shifted to the left (as viewed in FIG. 3) to port fluid under pressure to the operating chamber 138. This causes the motor assembly 142 to be returned to the retracted condition of FIG. 3. In addition, operation of the relay 254 activates a reset circuit (not shown) for the timer 204 to reset it for the next dressing operation. When the stop button 225 is released, the circuit for energizing the relay 254 is opened and the circuitry 174 is in condition for the next dressing operation.

The control circuitry 174 has been simplified in FIG. 12 in order to avoid prolixity of description. It is contemplated that the actual control circuitry utilized with the wheel dressing apparatus 22 will include suitable interlocks and other cirduit refinements. It should also be understood that if desired timers, similar to the timer 204, can be provided for the wipe cycles and the shoulder grind cycles. If desired, suitable gauges and surface condition detecting devices of a known construction could be utilized in association with the wheel dressing apparatus 22 to facilitate dressing the grinding wheel 28 to a predetermined finished condition.

m view of the foregoing description, it can be seen that wheel dressing apparatus 22 includes a main deresing wheel 32 for dressing a main surface 24 of the grinding wheel 28 and a shoulder dressing wheel 34 for dressing the shoulder surface 26 of the grinding wheel 28. The two dressing

wheels

32 and 34 are mounted on a common slide 38 which is moved under the combined influence of the base slide motor 46 and three-position motor assembly 42. The three-psotti motor assembly 42 enables the dressing wheel slide 38 to be accurately positioned with the dressing

wheels

32 and 34 in either the retracted position of FIG. 6, the main surface grinding position of FIG. 7, or the shoulder surface grinding position of FIG. 10.

.

wheels

32 and 34 have

cylindrical surfaces

52 and 64 which are utilized to dress the main and shoulder surfaces 24 and 26 of the grinding wheel 28, the area of contact between the dressing wheels and the surfaces of the grinding wheel 28 are minimized with a resulting enhancing of the finish on the dressed grinding wheel 28 and a minimizing of the pressure which must be applied against the dressing

wheels

32 and 34 to dress the grinding wheel.

Having described a specific preferred embodiment of the invention the following is claimed:

1. A method of dressing the periphery of a rotatable grinding wheel having a circular main surface which extends at an acute angle to the axis of rotation of the grinding wheel and a circular shoulder surface extending transversely to the main surface, said method comprising the steps of rotating the grinding wheel, moving a first rotatable dressing wheel into engagement with the main surface of the rotating grinding wheel, said step of moving the first dressing wheel into engagement with the main surface of grinding wheel includes the step of moving the first dressing wheel along a first path which intersects the main surface on the grinding wheel, said first path extending substantially perpendicular to the axis of rotation of the grinding wheel and at an acute angle to the axis of rotation of the first dressing wheel to provide for engagement of the first dressing wheel with the main surface of the grinding wheel as the first dressing wheel is moved along the first path, rotating the first dressing wheel about a first axis extending generally parallel to the main surface of the grinding wheel when the first dressing wheel is in engagement with the main surface of the grinding wheel, moving the first dressing whee] away from the main surface of the grinding wheel after the main surface has been dressed, moving a second dressing wheel into engagement with the shoulder surface of the rotating grinding wheel after performing said step of moving the first dressing wheel away from the main surface of the grinding wheel, said step of moving the second dressing wheel into engagement with the shoulder surface of the grinding wheel including the step of moving the second dressing wheel along a second path extending transversely to the-first path, rotating the second dressing wheel about a second axis extending generally parallel to the shoulder surface of the grinding wheel and transversely to said first axis when the second dressing wheel is in engagement with the shoulder surface of the grinding wheel, and moving the second dressing wheel away from the shoulder surface of the grinding wheel after the shoulder surface of the grinding wheel has been dressed.

2. A method as set forth in claim 1 further including the step of wiping the main surface of the grinding wheel by moving'the first dressing wheel axially along a path extending parallel to the main surface of the grinding wheel.

3. A method as set forth in claim 1 wherein said step of moving the first dressing wheel into engagement with the main surface of the grinding wheel includes moving the first dressing wheel through a first distance along said first axis and said step of moving the second dressing wheel into engagement with the shoulder surface of the grinding wheel includes moving the first dressing wheel through a second distance along said first axis, said second distance being greater than said first distance.

4. A method as set forth in claim 1 wherein said step of moving the first dressing wheel into engagement with the main surface of the grinding wheel includes moving the first dressing wheel radially along the first path and said step of moving the second dressing wheel into engagement the shoulder surface of the grinding wheel includes moving the second dressing wheel radially along the second path.

5. A method as set forth in claim 1 wherein said step of moving the first dressing wheel along the first path includes the step of moving the second dressing wheel along the first pa'th with the first dressing wheel, said step of moving the second dressing wheel along the second path includes the step of moving the first dressing wheel along the second path with the second dressing wheel.

Claims

1. A method of dressing the periphery of a rotatable grinding wheel having a circular main surface which extends at an acute angle to the axis of rotation of the grinding wheel and a circular shoulder surface extending transversely to the main surface, said method comprising the steps of rotating the grinding wheel, moving a first rotatable dressing wheel into engagement with the main surface of the rotating grinding wheel, said step of moving the first dressing wheel into engagement with the main surface of grinding wheel includes the step of moving the first dressing wheel along a first path which intersects the main surface on the grinding wheel, said first path extending substantially perpendicular to the axis of rotation of the grinding wheel and at an acute angle to the axis of rotation of the first dressing wheel to provide for engagement of the first dressing wheel with the main surface of the grinding wheel as the first dressing wheel is moved along the first path, rotating the first dressing wheel about a first axis extending generally parallel to the main surface of the grinding wheel when the first dressing wheel is in engagement with the main surface of the grinding wheel, moving the first dressing wheel away from the main surface of the grinding wheel after the main surface has been dressed, moving a second dressing wheel into engagement with the shoulder surface of the rotating grinding wheel after performing said step of moving the first dressing wheel away from the main surface of the grinding wheel, said step of moving the second dressing wheel into engagement with the shoulder surface of the grinding wheel including the step of moving the second dressing wheel along a second path extending transversely to the first path, rotating the second dressing wheel about a second axis extending generally parallel to the shoulder surface of the grinding wheel and transversely to said first axis when the second dressing wheel is in engagement with the shoulder surface of the grinding wheel, and moving the second dressing wheel away from the shoulder surface of the grinding wheel after the shoulder surface of the grinding wheel has been dressed.

2. A method as set forth in claim 1 further including the step of wiping the main surface of the grinding wheel by moving the first dressing wheel axially along a path extending parallel to the main surface of the grinding wheel.

4. A method as set forth in claim 1 wherein said step of moving the first dressing wheel into engagement with the main surface of the grinding wheel includes moving the first dressing wheel radially along the first path and said step of moving the second dressing wheel into engagement with the shoulder surface of the grinding wheel includes moving the second dressing wheel radially along the second path.

5. A method as set forth in claim 1 wherein said step of moving the first dressing wheel along the first path includes the step of moving the second dressing wheel along the first path with the first dressing wheel, said step of moving the second dressing wheel along the second path includes the step of moving the first dressing wheel along the second path with the second dressing wheel.