US1987812A

US1987812A - Grinder dressing machine

Info

Publication number: US1987812A
Application number: US654173A
Authority: US
Inventors: Frans O Albertson
Original assignee: Albertson and Co Inc
Current assignee: Albertson and Co Inc
Priority date: 1932-11-21
Filing date: 1933-01-30
Publication date: 1935-01-15
Anticipated expiration: 1952-01-15

Description

" F. O. ALBERTSON GRINDER DRESS ING MACHINE Jan. 15, 1935.

3 Sheets-Sheet 3 Original Filed Nov. 21, 1932 Jzdezalr jztazs Qfllberfiazz -Q a M $2M Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE Albcrtson & Company, 1110;, Sioux City, Iowa, a corporation of Iowa Original application November 21', 1932, Serial No. 643,584. Divided and thisappIication January 30, 1933, Serial No. 654,173

6 Claims.

The present invention relates to apparatus for dressing grinding stones which are primarily used for grinding valve seats and particularly adapted for the reconstruction and. repair of the valve seats of internal combustion engines.

The" present application is a division of my prior application, Serial No. 643,584, filed November 21, 1932, on a Method and apparatus for grinding valve seats, and the present application relates to the dressing apparatus per se disclosed in that prior application.

The present dressing apparatus is peculiarly adapted to dress grinding stones of the type employed upon the grinding apparatus disclosed in my prior application, and the present dressing apparatus is adapted to compensate for the divergence in angularity which is caused by the tilting of the stone on the tool holder in the grinding machine of said prior applications. Therefore, the characteristics of the grinding stone and tool holder which are used both .for grinding and dressing operations will be explained in connection with the present dressing apparatus.

The grinding machines of the prior art either have the grinding stone brought into engagement with the entire periphery of the valve seat at one time or they include complicated devices for both rotating the grinding wheel and revolving" the grinding wheel in an orbit to engage all parts of the valve seat with a grinding wheel which is of a smaller diameter. A full seat contact between the grinding wheel and the valve seat results in the clogging or loading of the wheel with the material which is ground "from the seat, and this causes a change of the contour of the stone and results in the grooving of the valve seat.

The grinding stones are also apt to be broken when the stone engages the entire periphery at once, and serious injury may result when the grinding stone, which is rotating at a high rate of speed, is broken and its pieces are thrown on from the machine.

The devices of the prior art which are adapted to revolve the grinding stone in an orbit, as well as rotate the grinding stone, are very complicated and expensive, and such devices cannot be brought within the means of ordinary garage owners on account of the expensive mechanism and machine work required to produce the complicated grinding tool.

One of the objects of the invention is the provision of an improved method of reconstructing valve seats by means of which the extremely hard seats of stellite, tungsten steel, or other hardened alloys can be ground quickly and uniformly to produce a finished seat, with a minimum amount of labor. The tendency in construction of valve seats for internal combustion engines is toward the use of seats of harder material, which cannot be satisfactorily worked by means of ordinary metal cutting tools.

Another object of the invention is the provision of an improved dressing apparatus which is adapted to produce a grinding stone of predetermined angularity and to compensate for the change in angularity which is produced by the tilting of the stone on the tool holder during the grin-ding operation.

Another object of the invention is the provision of an improved stone dressing apparatus which is adapted to dress the grinding stone away from the valve seat so that none of the particles of the grinding wheel fall on the seat or in the engine.

Another object of the invention is the provision of an improved dressing tool structure which is capable of producing either a relatively smooth dressed grinding wheel finish or a relatively rough grinding wheel finish, the latter being capable of use for fast cutting operations.

Another object of the invention is the provision of an improved dressing tool structure adapted to be adjusted for dressing-grinding stones of different thickness, diiierent ahgularity, and capable of economical manufacture.

Another object of the invention isthe provision of an improved dressing tool whichis simple in construction, sturdy and capable of mass production so that the invention may be brought within the means of a vast number of users who may practice the present grinding and dressing methods and utilize the tool as described here- Other objects and advantages of the invention will be apparent from the following description and from the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings, of which there are three sheets:

Fig. l is a side elevational view of the dressing apparatus, showing a part of the motor driver, which is disclosed in detail in my prior application;

Fig. 2 is a full size fragmentary elevational view of the adjustable support for the grinding stone, showing the angular relation between the grinding surfaces on the stone and the direction of movement of the dressing member;

Fig. 3 is a vertical sectional view of the tool holder and grinding stone, taken on the axis of the valve stem guide, showing a valve stem pilot in elevation and the valve in section;

Fig. 4 is a fragmentary elevational view in partial section, showing the details of construction of the adjustable support for the grinding stone on the dressing tool and also the structure of the dressing pilot;

Fig. 5 is a top plan view of the dressing tool, with the grinding wheel removed, showing parts of the diamond supporting plunger in elevation and parts of the clamping member in elevation;

Fig. 6 is a sectional view taken on the plane of the line 6-6 of Fig. 5, showing the details of construction of the angularly adjustable support for the plunger guide and of the diamond supporting screw;

Fig. 7 is a fragmentary sectional view taken on the plane of the line 7-7 of Fig. 5, looking in the direction of the arrows, showing the details of the construction of the diamond supporting screw and the friction device for holding it in any predetermined adjusted position; and

Fig. 8 is a side elevational view of the dressing tool taken from the side opposite from that of Fig. 1;

Fig. 9 is a bottom plan view of the grinding wheel;

Fig. 10 is a side elevational view of the grinding wheel with a valve seat, during the grinding operation, with a diagram to show the angular relations between the position of the grinding wheel during the grinding operation and during the dressing operation.

Referring to Fig. 1, the complete assembly of dressing apparatus preferably includes a motor driver 20, a tool holder 21, a grinding wheel 22,

and the dressing tool carried by the base 170.

The motor driver preferably comprises a series wound commutator motor having suitable speed increasing gearing and provided with an axially projecting drive shaft 76. The gear ratio is particularly adapted to drive the drive shaft at such a rotative speed that the grinding wheels of predetermined size are driven at a predetermined speed. The same driver 20 is also used for driving the grinding wheel or stone during the dressing operation at a high rate of speed, and it is found that grinding wheels of this type may be more effectively dressed when driven at rates of speed for dressing which are comvmensurate with the same rates of speed used in grinding.

It has been found that in order to obtain a proper grinding action with grinding wheels of this type the wheel must have a minimum speed of 3500 linear feet per minute and a maximum of 6,000 linear feet per minute at the grinding surface. The electric motor, for example, may have a speed of 3600 revolutions per minute, and in order to provide for grinding wheels of the various predetermined sizes, I prefer to provide a 6,000 R. P. M. driver and a 9,000 R. P. M. driver, the latter being used for smaller wheels.

The drive shaft 76 is preferably provided with a connection sleeve 82 having a frusto-conical or tapered bore 84 for receiving the driven end of the tool holder shaft, which is of complementary shape.

Sleeve 82 is also provided with a pair of grooves or slots 85 extending longitudinally into the end f the sleeve and located diametrically opposite to each other, having the grooves 85 substantially semi-circular at 86 to receive the rounded pin 87 carried by the tapered end 88 of the tool holder shaft.

Referring to Fig. 3, this is a vertical sectional view through the tool holder, which is shown in section in connection with the grinding stone and valve stem pilot in the grinding operation for the purpose of explaining the results which are desired and the characteristics of the stone which result from the dressing operation.

The pilot 23 is provided with a substantially cylindrical upper part 100, which may be provided with an aperture 101 to receive a pin for manipulating the pilot and shoving it in or pulling it out of wedging engagement with the guide 26.

The tool holder 21 is also provided with a tubular metal member 102 having an elongated and accurately machined bore 103 for slidably and rotatably receiving the cylindrical portion 100 of the pilot 23.

The tubular member 102 is preferably provided with the reduced end portions 104, 105, each of which is slightly tapered to efiect a close frictional fit with the

inner race rings

106, 107 of the self-aligning ball bearings. The ball bearings also comprise the

balls

108, 109, and the

outer race rings

110, 111. Each of the outer race rings is preferably spun over at one end and at the inner corner 112 to secure an oil seal ring 113 to the bearing. Appropriate packings 114 prevent the lubricant from leaking out of the bearings beyond the oil seal 113.

Metal plates

115, 116 slidably mounted on the tubular member 102 are located below the upper ball bearing and above the lower ball bearing, to confine the lubricant between the races. As lubricant is not required in the annular space 117, a spacer sleeve 118 is located in the tool holder casing 119 between the

plates

115, 116 to hold the plates in proper position against the ball bearings.

The tool holder casing 119 comprises a tubular metal member, such as a steel member, which is provided with a cylindrical bore 120 adapted to receive the

outer races

110, 111 and the spacer sleeve 118.

The lower end of the tool holder casing 119 is provided with an annular inwardly extending flange 121 forming an annular shoulder 122 against which the lower ball bearing rests, and the lower end of the tool holder casing 119 is provided with a reduced tubular boss 123 for supporting a grinding wheel. The tubular boss 123 has a bore 124 of suificient size to provide a clearance between the walls of the bore 124 and the tapered pilot 23, since the tool holder is to be guided on the pilot by the sleeve 102 and the ball bearings at each end of the sleeve.

The tubular boss 123 is provided with threads 125 for receiving the threads on the inside of a metal hub 126 which supports the grinding wheel 127 of carborundum or other solid abrasive material.

The grinding wheels may comprise either rough stones for cutting or relatively smooth stones for finishing work. In some cases, a single stone of suitable quality and texture may be suitably dressed to accomplish both results, the rough dressing being used for cutting, and the smooth dressing for finishing.

The lower end of the tool holder 21 is provided with a fiat annular surface 128 which extends at right angles to the axis of the tool holder, and it is also provided with a cylindrical surface 129 serving as a guide for receiving the cylindrical flange 130 on a collar 131.

This collar will be called the Dress-Grind collar, and its function and structure will be described in detail hereinafter. The collar comprises the cylindrical fiange 130 slidably fitting upon a cylindrical part 129 of the tool holder body 119, and the collar comprises an end plate 132 which tapers in thickness from the left side toward the right, as shown in Fig. 3. The end plate 130 has an enlarged bore 133 which may be threaded so that the Dress-Grind collar can be threaded over the threads 125, but it is loosely supported at the unthreaded part 134 between the threads 125 and the fiat end 128 of the tool holder. This arrangement permits the convenient assembly of the collar and the removal of the collar, and it also permits the collar to take its proper position on the end of the tool holder, but the collar does not fall off the tool holder, due to the threads 125, and the parts of the tool holder are thus permanently assembled together in such manner that no part is apt to be lost.

The grinding wheel 127 comprises the metal hub 126, previously described, and the grinding Wheel body of abrasive material, which is preferably provided with a flat top 135, a cylindrical outer surface 136, and a frusto-conical grinding surface 137. The bottom 138 of the grinding wheel may be fiat or take any appropriate shape. The cylindrical surface 136 of the grinding wheel is merely present on account of a desire to make the grinding wheel of sufficient thickness so that it may be dressed and used over again for a longer period of time until the stone becomes too thin. As the stone is dressed and used up, the length of the cylindrical surface 136 will diminish, and the stone will become thinner in a vertical direction.

On the small stones it is unnecessary to provide a guard, as the speed at which the stones are rotated is not sufficient to cause any danger, but, if desired, a guard may be provided on all stones,

1 and particularly upon the stones of larger diameter.

The guard comprises a stamped steel cup having a fiat end portion 139 and having a downwardly extending cylindrical border flange 140 encasing the end and a part of the periphery of the stone. The guard may be secured to the hub 126 by spinning over the upper edge of the hub outside the body 29 of the guard.

A fiber washer 141 is preferably interposed between the Dress-Grind collar 131 and the end of the tool holder so as to facilitate the unscrewing of the grinding wheel from the tool holder, as the metal surfaces otherwise become screwed together so tightly that difficulty is encountered in taking the grinding wheel off again.

The complete assembly preferably includes a helical coil spring 142 which is interposed between the upper end of the valve stem guide 143 and the lower end of the tool holder.

It was found that the friction of the tubular boss 123 against the coil spring 142 at the high rates of speed used was so great as to heat the spring and draw the temper from the spring and also melt the sulphur in the grinding wheel. In order to prevent this friction, the tool holder is preferably provided with a thrust sleeve 144 having a: bore 145 of suflicient size to receive the cylindrical part 100 of the pilot, and having an annular flange 146 engaging the end 147 of the guide sleeve 102.

The thrust sleevei44 is preferably split longitudinally to permit it to be sprung together, and

the flange 146 is sufiiciently narrow so that when the split end is sprung together it will pass through the bore 124. The flange 146, however, retains the sleeve in the bore 124 when the spring is removed. The thrust sleeve 144 has a clearance with the bore 124 in the tubular boss 123, and the thrust sleeve extends outward beyond the grinding wheel into engagement with a sheet metal cup shaped member 148.

The cup shaped member 148 provides a seat for the upper end of the spring 142. Springs of. various length should beused, depending upon the distance from the end 143 of the valve stem guide to the valve seat 149. For instance, the top of the spring should be about three-fourths to one inch above the valve seat when the tool holder is removed, to provide suilicient compression for lifting the grinding wheel off the seat. Several lifting springs of diiferent lengths are included as regular equipment.

In the operation of the device, the pilot stem 23 is, of course, fixed in the guide 26. The guide sleeve 102 is slidably mounted upon the pilot stem and could rotate, out the friction between the guide sleeve 102 and the pilot is greater than the friction between the inner and outer races of the ball bearings. Therefore, the guide sleeve 102' does not rotate.

There is no friction between the grinding wheel and the spring when the thrust sleeve 144 is utilized. The heating of the spring is thereby avoided and the temper of the spring is not drawn.

Referring to the Dress-Grind collar 131 (Fig. 3), it will be noted that in Fig. 1 one side of the collar bears the notation Dress on the cylindrical flange 130. The collar bears the notation Grind on the opposite side of the collar from the word Dress, and the cylindrical casing 119 of the tool holder has a mark and the indicia zero, to be used with these notations.

These indicia are used for setting the collar for the dressing or grinding operations respectively and the theory and operation of these elements will be described in detail hereinafter.

It should also be noted that the threads 125 are sufficiently loose with respect to the hub 126 so that the position of the grinding wheel 127 is determined by the tapered thickness of the body 132 of the Dress-Grind collar 131; that is, the plate 132 being thicker at one side than the other, the grinding wheel 127 engages plate 13 and is secured against the plate by the threads 125 in a tilted position, so that the grinding wheel engages the seat 149 at one side, as shown in Fig. 3, but only comes into close proximity to the seat at the other side of the grinding wheel.

The looseness of the threads 125 permits this tilting of the grinding wheel on the tool holder.

The upper end of the tool holder body 119 is provided with threads 150 which may be right hand threads, and the tool holder cap 151 may be provided with threads 152 in a left hand di rection'. Connecting sleeve 153 is provided with complementary threads and threaded into the casing 119 and the cap 151.

Connecting sleeve 153 is provided with an inwardly extending collar flange 154 forming a seat for a relatively heavy coil spring 155. At its other end the coil spring 155 is seatedagainst a flat steel plate 156, slidably mounted in a bore 157 in a universal joint sleeve 158. The cap 151' comprises. a cylindrical member having an inwardly extending annular flange 159 provided with a bore 160 having a curved surface for engagement with the ball 161. The cap is also adapted to receive the universal joint sleeve 158, which comprises a hardened steel tubular memher, having four axially extending slots 162 located ninety degrees apart.

The lower end of the universal joint sleeve 158 is provided with axially extending slots 163 for receiving the axially projecting ridges 164 carried by the connectingsleeve 153. Slots and ridges 163, 164 provide a driving connection between the sleeves 158 and 153. A driving connection is provided between the ball 161 and the sleeve 158 by four transversely outwardly projecting cylindrical steel pins 165 engaging in the slots 162.

The slots 162 are of sufiicient length so that the pins 165 may move upward and downward in the slots as the ball 161 rotates in the socket provided in the end of the cap 151. Ball 161 is preferably provided with a threaded bore 166 for receiving the reduced threaded end 167 of the ball shank. The ball shank is tapered at 88 for reception in the drive sleeve of the motor driver, and is provided with a transverse pin 8'7 to be received in the groove 85 of the motor driver shaft. The motor driver, therefore, rotates the shank 88 and. ball 161, and with it sleeve 158, sleeve 153, cap 151, casing 119, and grinding wheel 127.

The guide sleeve 102 and pilot, with the inner races of the ball bearings, do not rotate, and the self-aligning ball bearings provide a very smooth 4 rotating action for the grinding wheel, resulting in a uniform grinding action on all parts of the periphery of the valve seat 149.

As it is practically impossible to hold the motor driver 20 axially above the tool holder 21, the universal joint provided by the ball 161, cap 151, and sleeve 158 permits the driving of the tool holder by the motor driver, although the motor driver is not held in direct axial relation to the tool holder.

During the driving, the tool holder is guided by the pilot 23, irrespective of the position of the motor. However, it is found that direct mechanical shocks are transmitted to the grinding wheel 22 (Fig. 1) from the motor 20 on account of the action of the universal joint, unless some form of resilient connection is used, and the compression spring 155 in the universal joint eliminates the shock which would otherwise be caused by the universal joint.

The use of this spring gives a smooth drive for the grinding wheel and tool holder and facilitates the grinding and finishing of the valves with greater uniformity and a better finish. The shocks caused by the use of the universal joint are not transmitted to the grinding wheel when the spring 155 is utilized, but are absorbed by the spring.

In order to operate satisfactorily at the high rates of speed contemplated for both the grinding and dressing operations, the tool holder must be perfectly balanced and provided with the selfaligning ball bearings, as described, as the tool holders of the prior art could not be operated at such a rate of speed. The shock absorbing spring 155 is of great importance and advantage in both the grinding and the dressing operations.

Referring to Fig. 2, this is a full size elevational view of the grinding stone during the dressing operation, and it will be observed that the Dress- Grind collar has been turned to the dress position. The dash lines in Fig. 2 indicate elements of a cone having its axis in the axis of the tool holder and dressing pilot.

Referring to Fig. 3, this view shows the tool holder and grinding wheel in the grinding position, and the Dress-Grind collar 131 has been turned so that the word Grind appears under the mark zero.

The right side of the grinding wheel is accomplishing the grinding action, as evidenced by the dark mark 168 on the frusto-conical surface of the grinding wheel, and the grinding wheel 22 does not come into contact with the valve seat at the side 169, as shown by the space between the wheel and the seat at 169, this clearance being, however, exaggerated for the purpose of illustration. The grinding wheel is, however, sufficiently close to the seat so that the irregular abrasive formations on the wheel cause currents of air which blow off the grindings, and the wheel is self-cleaning. This self-cleaning action enables the grinding of the more finished seat and a more uniform grinding action, because the seat is actually ground to conform to the surface of the grinding wheel and is not marred by the presence of grindings between the wheel and the seat.

The present grinding wheel is preferably dressed apart from the valve seat 149 so that the abrasive which is dressed off the wheel does not fall on the valve seat. For this purpose I prefer to use a dressing tool of the type described.

The dressing tool comprises a supporting base 170 which is provided with a laterally projecting flange 171 at the bottom, having a fiat bottom 172 upon which the dressing tool stands. The base 170 has an upwardly projecting flange which is provided with an arcuate formation 1'73, the peripheral surface 174 of which (Fig. 5) serves as a dial for indicating the adjustment of the dressing tool for valves of different sizes.

Referring to Fig. 5, the curved surface 174 is provided with markings for valve seats of fortyfive degrees, thirty degrees, fifteen degrees, and ninety degrees, but the dressing tool may be adapted to dress stones of any particular angularity. The arcuate surface 174 is curved with respect to the center of a bore 175 (Fig. 6) which communicates with a counterbore 176.

The bore 175 rotatably receives a screw bolt 177 having a reduced threaded portion 178 which is threaded home into a threaded bore 1'79 in the pivoted guide arm 180. The counterbore 176 has a compression spring 181 seated at one end of the counterbore, and the opposite end engages below the head 182 of the screw bolt 177. Spring 181 is under initial compression, and it draws the fiat surface 183 of pivoted guide lever against the fiat ground surface 184 on the standard 185. Spring 181 and surfaces 183, 184 thus provide a friction device for holding the pivoted guide lever 180 in any predetermined position and facilitate its adjustment and support while it is being clamped in position.

The guide lever 180 is provided with a knife edge 186 located at a suitable radial distance from the screw bolt 177 so that the knife edge 186 slides along the curved surface 1'74 adjacent the angle marks shown in Fig. 8. The knife edge 186 serves as a pointer to be located adjacent the appropriate angular markings of Fig. 5. Guide lever 180 is also provided with a threaded bore 187 which receives the reduced threaded end 188 of a stud bolt, which is also threaded at its other end 189.

The guide lever has a transversely extending slot 190 adapted to receive the end of a sheet metal bracket 191, the bracket also having another flange 192 at right angles and provided with an aperture 193 for passing the threaded end of the bolt 189.

The end of the flange 192 engages the surface 194 on the opposite side of the arcuate dial 174 and may be used to clamp the guide lever 180 in any predetermined angular position. A threaded clamping member 195 is provided with a threaded bore for receiving the threaded end 189 of the stud bolt and with a transverse pin 196 for engagement with the fingers. The member 195 may be threaded home on the end 189 to clamp the flange 192 against the surface 194 after the guide lever 180 is located in a predetermined angular position.

The guide lever 180 (Fig. is provided at its upper end with a laterally projecting lug 197 having a bore 198 which extends substantially parallel to the surface 136. The guide lever 180 is also provided with substantially

parallel fiat surfaces

199, 200 carried by the sides of a laterally projecting rib 201 and providing guide surfaces for a plunger 202. The plunger 202 comprises a substantially cylindrical rod slidably engaging in the bore 198 and provided with an enlarged cylindrical member 203.

The cylindrical head 203 is provided with a substantially rectangular slot 204, the sides of which slidably engage the

flat surfaces

199, 200 on the guide lever 180 and prevent the plunger from rotating. The head 203 is provided with a reduced portion 204 adapted to provide a support for a casing 205 which engages the outside of the reduced portion 204 and is arranged flush with the head 203. Casing 205 comprises a tubular metal member which is formed with a longitudinally extending slot 206 adapted to pass a rib 201 on the guide lever 180. The end of the casing 205 is closed by a metal cap 207 having a reduced cylindrical portion 208 which; is a close frictional fit in the end of the tube 205.

Cap 207 is provided with a curved outer surface 209 for engaging in the palm of the hand when the dressing tool plunger 202 is actuated during the dressing operation. The cap 207 is also provided with a bore 210 for receiving a screw bolt 211 which is threaded into a bore in the end of the plunger 202. The head of the screw bolt 211 is disposed in a counterbore 212. Screw bolt 211 is thus adapted to clamp the sleeve 205 between the head 203 and the cap 207 to assemble these parts.

A helical coil spring 213 is compressed between the upper end of the lug 197 and the bottom of the cap 207 and urges the plunger 202 toward the right in Fig. 5.

The head 203 provides an adjustable support for a threaded bolt 214 having a knurled head 215. The bolt 214 is mounted in a threaded bore 216 which extends diagonally across the head 203. The plunger 202 is provided with a longitudinally extending bore 217 for slidably receiving a piston plunger 218 which is spring pressed by helical coil spring 219. The piston 218 engages the side surface of the bolt 214 and tends to hold it in any predetermined adjusted position byvirtue of the friction between the bolt 214 and piston 218.

Bolt 214 is provided with a pointed end 220 within which is set a pointed dressing member 221 of harder material than the grinding wheel itself. Such a dressing member may consist of a diamond or some other relatively hard cutting stone. The end of the bolt 214 is spun over a setting of brass for the diamond 221, confining it in the end of the bolt.

Referring to Fig. 4, this view illustrates the dressing pilot, which is supported upon the base 170. Base 170 is provided with a substantially horizontal platform or flange 222 having a threaded bore 223.

The flange 222 supports a dressing pilot 224, the upper portion of which is of substantially the same shape and size asthe upper portion 100 of the pilot 23. At its lower end the dressing pilot 224 is provided with an enlarged cylindrical portion 225 and with a reduced threaded portion 226 which is threaded into the bore 223. The cylindrical portion 225 is adapted to slidably receive a tubular supporting member. The upper end is provided with an inwardly'extending radial flange 228 and a bore 229. The bore 229 is adapted to receive the dressing pilot 224, and the tubular member 227 is adjustably mounted on the cylindrical part 225 to support the grinding wheel 22 at the desired height.

For this purpose, the sleeve 227 is provided with a spiral slot 230 which engages the complementary end 231 of a threaded screw bolt 232 having a knurled head 233. The screw bolt 232 is adjustably supported in a threaded bore 234 in a standard 235, the lower reduced end 236 of which is mounted in a bore 237. The standard 235 is secured in place by a set screw 238. A washer 239 is interposed between the hub of the grinding wheel and the end 228 of the supporting sleeve 227 to positively prevent engagement of the grinding wheel with the sleeve 227 and permit the grinding wheel to rotate more freely. This washer should be oiled frequently so as to permit the grinding wheel to rotate freely during the dressing operation.

The manipulation of the dressing tool is illustrated in Figs. 1, 2 and 4. The supporting sleeve 227 is lifted manually by rotating the sleeve and secured in place by means of the set screw 233 engaging in spiral slot 230, with the grinding wheel at the proper height. The grinding wheel 22 is, of course, mounted onthe tool holder 21 and adapted to rotate with the tool holder on the dressing pilot 224.

The motor driver is again used to drive the grinding wheel at a proper speed during the dressing operation. The diamond supporting screw 214 is adjusted so that when the plunger 202 is pushed downward the diamond 221 will engage the grinding wheel 22 and take a very light out oif the surface of the grinding wheel. In order to providea surface on the grinding wheel which is desirable for fast cutting, the plunger 202 should be pushed down rapidly, but in order to provide a relatively smooth finish on the grinding wheel for finishing, the plunger 202 should be pushed down very slowly while the grinding wheel is rotated by the motor driver 20.

It is necessary to understand the manipulation of the grinding wheel during the grinding operation in order to dress the grinding wheel properly.

Referring to Figs. 2 and 3, these figures illustrate the action of the grinding wheel during the dressing and the grinding operation. It has already been explained that the grinding wheel may be supported on the tool holder 21, with its frusto-. conical surfaces slightly tilted with respect to the axis of the tool holder, which, of course, also corresponds to the axis of the pilot. When the grinding wheel 22 is placed upon the tool holder 21 for a dressing operation, the Dress-Grind collar should .be turned to the position of Fig.

2, and the grinding wheel 22 threaded home upon the tubular lug 123. The dressing operation is then carried out, as previously described, on the apparatus of Fig. l, and the frusto-conical surface 137 of the grinding wheel will be made accurately frusto-conical as indicated by the lines 239, 240, drawn from the axis of the dressing pilot. Even though the grinding wheel has its upper flat surface 127 tilted with respect to the axis of the tool holder 21, the surface 137 which is produced by the use of the diamond dressing tool is accurately frusto-conical because the diamond is moved along an element of a cone, the axis of which is the axis of the dressing pilot, and the body of the stone is rotated about the axis of the dressing pilot.

The surface 137 is, therefore, accurately frusto-conical and whether it is relatively rough for fast cutting or relatively smooth for finishing work, will depend upon the manipulation of the dressing plunger.

When the dressing plunger is moved down fast during the rotation of the grinding wheel, it may be assumed that the diamond will cut off a part of the grinding wheel surface corresponding to a spiral path, and it might leave parts of the abrasive surface between this spiral path. When the diamond supporting plunger is pushed down slowly during the fast rotation of the grinding wheel, and care is taken that the diamond strikes every part of the grinding surface of the grinding wheel, this surface will be dressed to a substantially smooth frusto-conical finish, as the diamond will have an opportunity to take off all parts of the abrasive surface which it can touch.

When the wheel is to be used for grinding, the grinding wheel 22 and tool holder 21 are removed from the dressing tool, and the Dress-Grind collar 131 is loosened by turning the grinding wheel 22 in a counterclockwise direction and loosening its hub 126 on the threads 125. The Dress-Grind collar is turned one-hundred and eighty degrees from the position of Fig. 1 to that of Fig. 3, until the word Grind is under the pointer bearing the indicia zero.

Referring to Fig. 2, it will be observed that the thick part 241 of the Dress-Grind collar 131 is located at the left side, and referring to Fig. 3, it will be noted that the thick part 241 of the Dress- Grind collar is located at the right side when the stone is in position for grinding.

In other words, the thickness of the plate between the grinding wheel and the end of the tool holder tapers from left to right in Fig. 2 and from right to left in Fig. 3. If the grinding wheel is tilted upward toward the right in Fig. 2, it will be tilted downward toward the right in Fig. 3. As a result-of this, the side of the grinding wheel which is toward the right in Fig. 3 comes in contact with the valve seat, but the side 169 of the grinding wheel in Fig. 3 does not engage the valve seat.

Referring to Fig. 10, the angular relation of the parts is best illustrated by the diagram shown between the proportions of the taper on the spacing plate of the Dress-Grind collar may be varied, and I do not wish to limit myself to any particular taper. This taper is preferably made such that the grinding wheel engages only at one side over substantially one-third of the grinding periphery of the wheel, and the taper is preferably such that the other part of the grinding wheel is located in close proximity to the seat so as to efi'ect cleaning action by virtue of its proximity and by virtue of the air current caused by such proximity.

For example, in one embodiment of the invention the taper in the spacing plate of the Dress- Grind collar is such that the angle between the upper and lower surfaces of the Dress-Grind collar diverges two-tenths of a degree from the parallel. This divergence is exaggerated in the diagram shown in Fig. 10. The grinding wheel would, therefore, be tilted two-tenths of a degree toward the left in Fig. 2, and two-tenths of a degree toward the right in Fig. 3. The change in tilt of the grinding wheel from the dress position to the grind position would be the sum of these two angles, or four-tenths of one degree, or approximately one-half degree.

In other embodiments of the invention, the tilt may amount to several degrees, but it is preferred to keep the tilt as low as possible in order to keep the non-contacting parts of the grinding wheel in close proximity to the surface of the valve. The minimum of tilt permissible is that which accomplishes a suitable dispersement of the cuttings and self-cleaning of the grinding wheel.

Since the grinding wheel is tilted on the tool holder between the time when the wheel is dressed and the wheel is used for grinding, it will be observed that if the dressing tool had its angular markings for any particular angle so disposed that the plunger would move at that angle to the dressing pilot, the angularity of the grinding wheel would not be correct when it is later tilted on the tool holder. In other words, if the diamond supporting plunger were accurately held at fortyfive degrees, and the grinding wheel 22 were tilted a half degree to the left, in Fig. 2, then the angularity of the frusto-conical surface 137 would be forty-five degrees and one-half instead of forty-five degrees.

In a similar manner, if the tilt amounted to three degrees toward the left, the angularity of the tool would be forty-eight degrees, whereas a forty-five degree grinding action is desired.

In order to compensate for this action, the markings on the dressing tool of forty-five degrees are preferably not located to hold the plunger at exactly forty-five degrees to the dressing pilot. Each of the angular degree markings is located to hold the dressing diamond plunger at a predetermined angle which will so dress the grinding wheel that the grinding wheel will produce a finished seat of the predetermined angularity desired.

The grinding wheel is not dressed at the angularity desired for the seat, but at such an angularity that when the grinding wheel is tilted that element of the grinding wheel which engages the seat 149 at the right side in Fig. 3 is located at the angle desired.

The dressing tool is thereby adapted to compensate by means of its adjustments and indications for the tilt, which is later accomplished by means of the Dress-Grind collar in the grinding operation. The fact that this Dress-Grind collar also may tilt the grinding wheel in the opposite direction prior to the dressing action does not effect the accuracy of the dressing of the wheel, but merely makes the tilt twice as much as could otherwise be accomplished, since the wheel is moved from a position where it is tilted toward the left to a position where it is tilted toward the right.

An understanding of the method of finishing valve seats with this apparatus is necessary to a Cir complete understanding of the advantages of the dmessing tool. The method of finishing valve seats or reconstructing valve seats may be carried out by the apparatus described, and is preferably practiced as follows:

A recess is first cut in the seat of the valve in the engine block, the recess being adapted to receive a new valve seat ring of tungsten steel, stellite, or some other hardened alloy better adapted to withstand the. heat and impact to which valve seats are now subjected. The ring is secured in place by close frictional engagement with the walls of the recess or by spinning over the metal of the engine block above the ring. The tool holder may then be provided with a rough grinding wheel which is placed upon the tool holder with the Dress-Grind collar in the dressing position of Fig. 2.

The tool holder and grinding wheel are placed upon the dressing pilot and the tool holder is rotated at a high rate of speed within the range specified, while the diamond dressing tool is moved across the face of the grinding wheel in a direction which corresponds to the angle of the valve seat desired, plus or minus the amount of tilt caused by the Dress-Grind collar.

If the same stone is to be used for both the dressing and grinding operations, the diamond is moved quickly across the surface of the grinding wheel to produce a relatively rough and fast cutting wheel. The wheel is then loosened from the tool holder, and the Dress-Grind spacing .collar turned one-hundred and eighty degrees, after which the wheel is again tightened on the tool holder and, by virtue of the taper of the spacing plate between the grinding wheel and the tool holder end, the wheel has been tilted a predetermined number of degrees equal to the degrees for which the dressing tool is compensated.

The tool holder is then placed upon the pilot, which has previously been fixedly secured in the valve stem guide in centered relation, and the grinding wheel is supported above the valve seat by means of the compression spring. The motor driver is applied to the upper end of the tool holder, and while the motor is operating at a high rate of speed within the range described, the motor and tool holder are pressed down lightly until the grinding wheel engages the seat.

The grinding wheel should not be pressed so hard that the speed of the wheel and the motor is slowed up, but a very light pressure should be used, and as the grinding wheel rotates, the tool holder, wheel and motor should be moved up and down frequently in the same manner as that used in lapping in a valve. The grinding wheel will then come into initial engagement with the seat at different points rotatively of the seat, and the random engagement between the grinding Wheel and the seat will give a more uniform action and permit more finished grinding of the seat than a continuous grinding action.

The rotation of the grinding wheel tilted with respect to the seat causes only one side of the wheel to grind the seat, and the other side of the wheel aids in dispersing the cuttings from the seat and the wheel by virtue of its close proximity to the seat.

The same grinding wheel may then again be dressed to a finished surface, and applied to the seat in the same manner to produce a finished seat, or a relatively smooth stone may be dressed and used in the same manner to produce a finished seat. The fast cutting or rough grinding wheel need only be used where there is a a great deal of material to be cut away from the seat, as, for example, when a new valve seat ring is used which does not have a frusto-conical seat formed upon it.

In brief, the method of finishing the seat comprises the rotation of a grinding wheel of frustoconical form while passing a dressing element across the frusto-conical surface of the grinding wheel at an angle which is equal to the angle of the seat desired plus or minus a predetermined angular tilt, thereby dressing the wheel to an angularity which does not correspond to that of the seat desired; then tilting the grinding wheel with to its axis of rotation and applying the grinding wheel to the seat in such a manner that only one side of the grinding wheel touches the the tilt being the predetermined amount for which compensation has been made in the dressing operation.

It will thus be observed that I have invented an improved method, an improved grinding tool assembly, an improved tool holder, an improved dressing tool, an improved grinding wheel, and other apparatus for the purpose of grinding valve seats of internal combustion engines.

The present grinding apparatus is admirably adapted to handle valve seats of particularly hard alloys and to produce a finished valve seat without necessity for any hand lapping operations. very fast and yet smooth and uniform, as the tiltof the wheel effects a dispersion of the cuttings and prevents the loading or clogging of the wheel so that the ground seat corresponds closely to the shape of the accurately dressed grinding wheel.

The use of the spring mounted universal joint prevents the transmission of shocks from the 1miversal joint and motor to the grinding Wheel, and also makes for a smoother grinding action of the wheel. 'The spring mounted universal joint also clients a more uniform dressing action and enables the dressing tool to form a stone which is accurately frusto-conical and capable of producing finished valve seats.

The present results are all accomplished by means of a very simple type of apparatus, which does not require but a single drive shaft and the valve seat grinder is much more simple than the devices of the prior art, so that it may be brought within the reach of a large number of users.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details or" construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a dressing tool for grinding wheels for valve seats, the combination of a supporting pilot with a tool holder adapted to be rotatably mounted on said pilot, said tool holder supporting said grinding wheel, means carried by said dressing tool for dressing the surface of a grinding wheel, adjustable means for supporting said grinding wheel at a predetermined elevation with respect to said dressing means, said adjustable means comprising a supporting sleeve having a spiralled slot for holding said sleeve at a predetermined elevation.

2. A dressing tool for valve seat grinding wheels comprising a supporting base, a dressing The grinding action of the tilted wheel is pilot carried by said base, a guide lever pivotally mounted on said base and capable of adjustment to any of a plurality of angular positions with respect to said dressing pilot, an arcuate flange carried by said base adjacent said guide lever, a dressing member movably mounted on said guide lever and guided thereby, and resilient means for adjustably and frictionally supporting said guide lever in any of a plurality of angular positions with respect to said flange, comprising a resilient member carried by a bolt pivotally supporting said guide lever, said resilient member being compressed between the head of said bolt and said base to draw said guide lever into frictional engagement with a part of said base.

3. A dressing tool for valve seat grinding wheels comprising a supporting base, a dressing pilot carried by said base, a guide lever pivotally mounted on said base and capable of adjustment to any of a plurality of angular positions with respect to said dressing pilot, an arcuate flange carried by said base adjacent said guide lever, a dressing member movably mounted on said guide lever and guided thereby, resilient means for adjustably and frictionally supporting said guide lever in any of a plurality of angular positions with respect to said flange, and means for clamping said guide lever in predetermined position while held by said resilient means, comprising a threaded member carried by said guide lever, a bracket engaged by said threaded member on said guide lever, said bracket engaging a flange on said base to clamp said guide lever in predetermined position.

4. In a dressing tool for grinding stones, the combination of means for rotatably supporting a grinding stone comprising a base, a guide lever pivotally mounted on said base, said guide lever having a pair or" guide surfaces and a bore, a plunger slidably mounted in said bore and having complementary surfaces engaging said guide surfaces, a dressing member carried by said plunger and adapted to be moved across the surface of said grinding wheel by said plunger while said grinding Wheel rotates, said dressing member consisting of a hard dressing stone adjustably mounted in a screw extending transversely to said plunger, and friction means resiliently urged into engagement with said screw for holding said screw in predetermined adjusted position.

5. In a dressing tool for grinding stones, the combination of a base having an upwardly extending standard provided with a horizontal supporting flange, a pilot member fixedly mounted in said supporting flange, a sleeve carried by the lower part of said pilot and having a spiral slot, said sleeve being adapted to support the grinding stone at predetermined elevations, an adjustable threaded member carried by said standard and engaging in said spiral slot for securing said sleeve at predetermined elevations, and a plunger mounted on said standard and having a dressing member, said plunger being adapted to move at an angle across the face of a grinding stone to dress the grinding stone when the grinding stone is rotating on said pilot.

6. In a dressing tool for grinding stones, the combination of a base having an upwardly extending standard provided with a horizontal supporting flange, a pilot member fixedly mounted in said supporting flange, a sleeve carried by the lower part of said pilot and having a spiral slot, said sleeve being adapted to support the grinding stone at predetermined elevations, an adjustable threaded member carried by said standard and engaging in said spiral slot for securing said sleeve at predetermined elevations, and a plunger mounted on said standard and having a dressing member, said plunger being adapted to move at an angle across the face of a grinding stone to dress the grinding stone when the grinding stone is rotating on said pilot, said dressing member being supported upon a threaded member adjustably mounted transversely to said plunger, and spring actuated friction means in said plunger engaging said threaded member to hold said threaded member in any predetermined adjustment.

FRANS O. ALBERTSON.