US2294493A - Apparatus for wheel dressing - Google Patents

Description

p 1 J.YC. WILSON 2,294,493

APPARATUS FOR WHEEL ,DRESSING Filed Aug. 28, 1 940 5 Sheets-Sheet l Sept. 1, 1942. J. c.'wu -soN 2,294,493 0 APPARATUS FOR WHEEL DRESSING I v Filed Aug. 28, 1940 5 Sheets-Sheet 2 -J I 25 6 A4 INVENTOE Jam c.wu.so-,

W 37 Y ATTORNEYS Sept. 1, 1942. J, WILSON. 2,294,493

APPARATUS FOR WHEEL DRESSING Filed Aug.- 28, 1940 5 Sheets-Sheet 3 ATTORNEYS Sept. 1942- J. c. WILSON 2,294,493

APPARATUS FOR WHEEL DRESSING Filed Au 28, 1940 I s Sheets-Sheej I I I LE 2/ i5 lrivaHTolz JOHN C. WILSON M ATTORNEYS Sept: 1, 1942.

J. c. WILSON APPARATUS FOR WHEEL DRESSING Filed Au 28, 1940 5 Sheets-Sheet 5 Patented Sept. '1, 1942 I s. PATENT. OFFICE APPARATUS FOR WHEEL DRESSING John O. Wilson, Springfield; Ohio, assignor to- The Thompson Grinder 00., Springfield, Ohio, a corporation of Ohio Application August 28, 1940, Serial No. 354,556

17 Claims. (Cl. 125-11) The present invention relates to grinding machines, and more particularly to a dresser attachment for the machine.

In the fabrication of machine tools and machine elements, particularly for aircraft engine and similar production, it is often necessary to provide a grinding wheel which has an abrading surface of irregular configuration. For example, this surface may be formed by a wheel having a portion of its thickness of one diameter and another portion of another diameter, the periphery being terminated at the edge of the wheel in a rounded surface. This shape is set forth merely by way of example since there is-a multitudinous number of grinding wheels having different shapes employed in this highly specialized art.

In order to assure extreme accuracy of the grinding operation in quantity production, it is necessary that the grinding wheel be dressed from time to time, and that the dressing operation be performed in such a manner that the wheel will have the same peripheral shape after being dressed that it had before the dressing operation. dressed by hand tool provided with a diamond nib, particularly .those wheels of complicated shape, so that the accuracy with which the dressing operation was performed would vary since it depended solely on the experience and skill of the dressing operator.

The primary object of the present invention is to provide a dresser tool attachment forv a grinding wheel in which the tool accurately follows the initial shape of the grinding wheel periphery, regardless of the number or character Heretofore, wheels were usually A more general object is to ,provide an inexpensive dresser tool mechanism in which the tool is caused to pass and accurately follow the entire grinding periphery of the wheel, first in one direction and then in the opposite direction,

regardless of the intricacy of shape of the wheel.

The above objects are attained, in brief, by securing the dresser tool to a follower which is caused to pass over a cam having a shape which corresponds accurately with the shape of the grinding wheel, and in order to cause the tool to dress the rounded terminating edge oredges of the wheel the dresser tool, follower and cam are rotated as a unit in a circle, the center of which corresponds with the center of the round peripheral portion of the wheel. All of the various movements of the dresser tool, follower and cam are made frictionless by the use of ball bearings, and ample adjustment through wedge-shaped gibs is provided in order to take up the wear. The invention will be better understood when the specification is perused in connection with the accompanying drawings.

In the drawings:

Figure l is an elevational assembly view looking toward the side of the grinding wheel, and showing the improved dresser attachment which forms the subject of this invention. 1

Figure 2 is a sectional view taken along the line 2-2 in Figure l, but showing the dresser tool in elevation. In this figure the diamond nib is Just starting to dress the nearer edge of the grinding wheel.

Figure 3 is a view similar to Figure 2, but showing the nib at a position on the wheel just before it proceeds around the rounded edge of of the irregularities of that shape, so that the dressed wheel has exactly the same configuration after the dressing operation as it had before.

Another object is to provide an attachment,

as explained above, in which the tool not only follows all of the irregularities of the external periphery of the wheel surface but also follows a rounded edge provided on the wheel.

Another object is to provide a dresser tool mechanism in which the path over which the dresser tool is moved can be readily changed to movements of the tool can be constrained to a predetermined path corresponding to thedesired shape of the grinding wheel.

Figure 5 is a sectional view taken along the line 5--5 in Figure 1, looking intlie' direction of the arrows.

shows the cam and follower in a position removed ninety degrees after the diamond nib has been caused to follow the rounded edge of the grinding wheel.

Figure 8 is a perspective diagrammatic view A screw 3'! abuts. The latter is threaded through v nib to dress the periphery of the wheel. The work table of the grinding machine'is illustrated in Figure l by the reference character I. The apparatus to be described, with the exception of the source of pressure-fluid, is carried on a base 2 bolted as at 3 to the table l. The grinding wheel is illustrated at 4, and has as a typical shape a large diameter portion 5 which merges over curved sections into a smaller diameter portion 3 (Figure 8), and is terminated at the left-hand edge by a rounded portion I, the radius center being indicated at 8. a

The dressing tool 3 may comprise the usual form of diamond nib secured in any suitable manner to a round shoulder portion 10, which is provided with a shaft H. The latter is slidably supported in the end of a follower rod I2, and is secured at any desired position with respect to the rod by means of a thumb screw l3 (Figure 2) The shank !4 of the thumb screw passes through an opening in a cap l5 which is secured to the follower l2, this cap having a downwardly extending sleeve portion I6 of somewhat'larger diameter. This sleeve-like portion slidably fits over an upwardly extending hub member L], which is provided atthe'bottom with an outwardly extending flange member l8 and ribbed at each side as indicated at l9. To the left-hand end of the flange member l8, as seen'in Figure 2, there is screwed, as indicatedat 20, a downwardly extending cover plate 2| provided with a slot 2 i, the purpose of which will be explained hereinafter. V

The lower end of the follower l2 terminates in a portion 22 having straight tapered sides, preferably giving a line efiect (instead of a point) at its lowermost edge. The tapered portion carries a shoulder 23 which fits snugly but slidably within a bore 24 formed in the hub member l1. There'is a compression spring 25 contained within the annular space between the bore 24 and the follower I2, this spring bearing at one end against a counterbore surface 26' and the shoulder 23. The purpose of this spring is to-urge the follower I 2 downwardly against a cam surface indicated at 21, which has a configuration exactly the same as that of the portions 5 and 3 (Figure 8) of the grinding wheel. The cam 21 has a length apprbxil'nately the same as the thickness of the grinding wheel, measured from the, center 8 (Figure 8) to the right-hand edge of the wheel. The cam 21 is carried on a relatively long base member 28,'which is provided at each side with longitudinally extending V-shaped grooves 29 lowed-out portion 4|.

be controlled by means of a wedge-shaped gib 33, which forces the left-hand rail (Figure 1) against its set of ball bearings as a screw 34 is v turned (see also Figure 6).

The left-hand end of the basemember 28, as seen in Figure 2, is provided with a cut-back shouldered portion 33 against which the stop a splitcollar 38 (Figure 6) the tightness of which can be adjusted by a screw 39. This collar is screwedlas indicated at 40 (Figure 2), or secured in any suitable manner to the base 2. The latteris provided with a hollowed-out portion 4|, of

dish-like configuration, the radius of which coincides with the center 8 of the rounded edge of the grinding wheel. The purpose of thi hollowed-out portion will be explained hereinafter.

Resting on the base 2 at the end opposite thecam 21, there is a plate 42 having an inner tapered surface 43, this'plate being slidably adjustable with respect to the base 2 by means of a screw 44 which is carried by a bracket 45. The latter preferably is secured to the base 2 by means of screws 46. The screw 44 is preferably provided with any suitable form of locknut mechanism indicated at 41. There is a tapered surface or edge provided at the right-hand end of the base member 28, as seen in Figure 2, which corresponds with the taper 43 of the plate 42. A fiat bar 48 with an inner tapered edge backed away from the edge 43 may be screwed, as indicated at 49, to the plate 42. The taper 43 of the plate 42 and the corresponding taper of the base member 28 preferably form a continuation (with slight modification) of the curvature of thehol- It is apparent that the purpose of the screws 31 and 44 is to adjust the longitudinal position of the cam 21 (Figure 2) in order to accurately align the cam surface with the corresponding surface of the grinding wheel 4. The screw 44, in addition, adjusts the base member 28 which carries the cam in the vertical plane.

In accordance with the present invention the lowermostpoint or edge of the follower I2 is caused to ride up on the cam surface 21 when it is desired to dress the wheel, and-the attachment which has previously. been bolted to the grinding machine table, has been brought into dressing position. The mechanism for performing this function has been shown in simplified form in Figure 8. The hub member I! is provided with a webbed crank 50, this crank terminating in an shroud member 55 is preferably secured to the ball bearings 30 by the respective rails 32 may barrel casting 56 in any suitable manner. At each end of the barrel casting 56 there is provided a. rollerrace 58 (Figure 1), the rollers of which are indicated at 59. The inner portion of each race is secured to the main shaft 52 of the attachment and serves rotatably to support the latter.

The shaft '52 is provided with a shoulder which is contained within a chamber formed in thershroud member 55 and bears against the inner surface of the member in order to prevent any undue longitudinal movement of the shaft. At approximately the midpoint of the barrel ,90 and a common inlet pressure pipe 9|.

casting 56 the shaft 52 is provided with a pinion 6|, keyed to the shaft, as indicated at 6|, this pinion being adapted to mesh with a toothed rack indicated at 62. As seen in Figure4, the toothed portion of the rack may constitute a any stationary part of the frame. A .compresblock which is carried on a support member 69,

to which it is secured preferably by means of on'e or more dowels 64 and screws 65. The support member 69 is provided at its Opposite sides with wedge-shaped surfaces, indicated at 66 (Figure 1) to form a dove-tail slide member. This member is adapted to slide within a wedge-shaped groove formed in an upstanding frame member '61, which constitutes an integral portion of the base 2. The frame member 61, is provided at each side at the top with a notched-out portion which receives a rail 68. Each rail is provided with a V-shaped groove 69, which receives ball bearings 10. These bearings are held in place and adapted to rotate along a V-shaped groove 7| 'formed in a rail I2, which is provided with an extension E3 on each side of the arch portion 51 of the barrel casting 56.

The left-hand end of the dove-tail slide member 63 (Figure 4) is provided with a downwardly extending projection I4 which is secured, as by a nut 15, to a shaft I6 on which is mounted a piston H. The latter is adapted to reciprocate within a cylinder 18, which is secured in any suitable manner to the frame member 67 and is provided at the top with a flat surface 79 on which the dove-tail slide member 63 is adapted to slide. The right-hand end of the cylinder 19 (Figure 4) is closed by an integral portion 80, the left-hand end being closed by a closure member 8| secured in any suitable manner to the cylinder walls within a countersunk opening 82. The shaft I6 is adapted to slide through the closure member M. The latter contains any suitable form of packing gland to prevent the escape of fluid from the interior of the cylinder. It is evidentthat as the piston 11 moves to the left (Figure 4) the slide member 63 is also caused to move to the left, carrying with it the rack 62 and causing the shaft 52 to be rotated clockwise, as seen in Figure 4.

In order to take up the wear at the tapered surfaces 66 there may be provided a tapered gi-b 82 (Figure l), the position of which may bead- Justed by a screw 83, as is well known in the art. There is a similar tapered gib 64 provided at the back of one of the rails I2, and adjusted in position by the screw 85 to eliminate the effect of wear at the ball bearings I0. There is a pair of upstanding projections or brackets 86 secured to the left-hand end of the cylinder 18, or any other portion of the main frame, by screws 86', these brackets being positioned on opposite sides of the dove-tail slide 63 (Figure 1). Each bracket is split at the top adjustably to receive a knurl headed screw 81, which is held fixedly in place by a tightening screw 88. The purpose of the screws 81 will be explained presently.

For controlling the movement of the piston I7 within the cylinder l8, there is provided a pilot valve 89 of any suitable and well known type, having a pair of alternately operative outlet pipes From the extreme ends of the pilot valve there is taken a pair of exhaust pipes 92, leading to a common exhaust 93. The pipe 9| is connected to a source of pressure fluid, preferably oil, The double-acting piston within the valve carries a reciprocating shaft 94 on which is fixedly mountsion spring 98 is positioned between one leg of the bracket 91 and the inside surface of the collar. 96. The other leg of the bracket 91 is provided with a boss 99 which serves as a bearin for a shaft i 00, which is provided at one end with a rotary latch member I0| and at the other end with an upstanding trip lever I02.

The arrangement is such that when the collar 95 is pulled to the left (Figure 8) the collar 96 loads the spring 99, permitting the right-hand side of the collar 96 to strike the left-hand side of thelatch IOI and forcing the latch to rotate in the clockwise direction, carrying with it the trip lever I02. The movement of the collar 95 also moves the shaft 94 to the left'together with the piston within the valve 69, and permitting pressure fluid from the pipe ill to enter the cylinder and to pass upwardly through the pipe 90. The pressure fluid flows through the pipe 90 and does work within the cylinder I6, as will be explained more in detail hereinafter, and afterwards is exhausted back through the pipe 90, and through the valve 89 to the pipe 92 when the shaft 94 is moved inwardly toward the valve 89. This inward movement of the shaft is caused by tripping of the lever I02, as will be explained hereinafter, which causes the latch IOI to release itself from the collar 96 and permitting the latter to be moved to the right, due to the urge of the spring 99. Under these circumstances pressure fluid will pass through the pipe 9|,

through the left-hand outlet pipe 90 (Figure 8) and to the ppposite end of the cylinder 79 to perform work therein. 0n exhaust the fluid returnsby the left-hand pipe 90, through the valve 69 and the left-hand pipe 92 to the exhaust 99. Thus pressurefi-uid is caused to flow through the right-hand pipe 90 by pulling the collar 95 to the left, and is caused to fiow through the lefthand pipe 90 when the trip lever I02 is moved to the right.

The shaft 52 is provided at its nearer end, as

" seen in Figure 8, with a shoe I03 which has a ed a pair of collars 95, 96. The shaft or rod 94 general circular shape but is provided with a flattened surface I04 at its bottom side. There is an outwardly extending web I05 secured to the shoe, which has a bottom surface I06 in line with the flattened surface I04. As will be seen in Figure 5, the shoe I03 is keyed to the shaft as indicated at I 01. The flattened surfaces I04,. I06 rest on the top surface of a builtip template, generally designated I08. This template is formed of two side members I09 having a rectangular configuration, and each provided with a circular notch H0. The side plates I08 are separated from one another by intervening blocks III at each end of the template, these blocks being secured to the side plates preferably by dowel pins I IZ and screws II3 (Figure 5). The entire assembly I09 rests on and is secured to a plate -II4 by screws H4. This plate, in turn, is supported on a tapered gib II5 which separates the plate H4 from an 'L-shaped bracket member I I6. The latter may be secured to the frame member 61 by means of screws Ill.

The position of the gib 'I I5 may be adjusted with and I06 formed on the shoe.

Complete description of the operation Assume that it is desired to dress the surfaces 5, 6, also the rounded end portion 1 of the grinding wheel 4; assume further that the diamond nib 9 is in the approximate position shown in Figure 8. The collar 95 is pulled to the left, as explained hereinbefore, causing pressure fluid to pass through the right-hand pipe 90 and to enter the cylinder 18 to the right of the piston 11 (Figure 4). The latter is then caused to move to the left, carrying with it the shaft 16, which as explained hereinbefore, is connected with the left-hand end of the dove-tail slide 63. The teeth of the rack 62 are thus caused to move to the left (Figures 4 and 8), which would normally cause the shaft 52 to rotate in the clockwise direction.

The shoe portion I03 of the shaft 52 has a flattened surface at the bottom which bears against the flat surface of the template I08, and precludes any rotation of the shaft 52. Thus the only movement which the rack 62 can communicate to the shaft 52 through the gear BI is a longitudinal movement parallel to the upper surface of the template I08. It is apparent that the shaft 52 carries with it not only the barrel casting 56, since there is no relative motion at the roller bearings 59, but also the crank 50 which supports the diamond nib 9 through the hub I'I.

It has been explained that the-cam 21 has the same configuration at the top surface 'as the shape of the grinding wheel periphery. Consequently, as the hub I1 is caused to move to the left the tapered end' portion 22 of the follower I2 rides over the cam surface so that there is a movement upward of the follower to correspond with the cam contour and against the compressing action-of the spring 24. Thus the diamond nib 9 is caused to dress the periphery of the grinding wheel 4 to a shape determined by the shape of the cam 21. This operation continues as long as the shaft 52 is caused to move longitudinally over the template I08, assuming that pressure fluid is being'continually admitted through the pipe 9|, the right-hand pipe 90 and to the right of the piston 11 (Figure 4).

It has been pointed out that the dovetail slide as is mounted on ball bearings 10 so that little or no friction is encountered, except for the rotative urge exercised by the rack on the pinion and which is forestalled by the flat surfaces I04 This action continues until the end of the barrel casting 56 nearer the screw 81 actually contacts the screw. For contact purposes there may be-provided a pair of buttons II9 opposite thescrews or adjustable stops 81. Consequently, as the barrel casting continues to move to the left the contact members II9 will strike the stops 81, which prevents further longitudinal movement of the casting 56 and the contained shaft 52. The stop 81 is adjusted at such a point that when contact is made with the member II9 the diamond nib 9 will be directly under the center point 8 of the grinding wheel, as shown in Figure 3. The shaft 52 is so arranged that its axis at this moment exactly coincides with the center point 8, and this feature has also been shown' in Figure 3. The slot 2I"is sufiiciently large to permit the head of the screw 31 to pass through the same in order that the hub member I1 and its contained follower can move to the right all of the .at I20 (Figure 8), will have reached the righthand edge of the notch 0. Consequently, assuming that the rack 62 continues to move to the left, the circular portion of the shoe I03 will now be in such a position with respect to the notch IIO that the pinion BI is permitted to rotate clockwise at least through a predetermined arc,-

depending on the peripheral length of the notch IIO. It was pointed out that the barrel casting 56 has been brought to a stop by the screw 81 so that the only movement which the shaft 52 can have is one of rotation, this rotary efiort being effected at the roller bearings 59. This rotational movement of the shaft carries with it the crank 50, also the hub I1, the flange member I8 and the cam 21. The cam 21 and the base member 28 are effectively held to the flange member I8 during this upward rotation of these elements by means of the ball bearings 30 which ride in the rails 32, secured respectively to each of these elements. It has been pointed out that the base 2 is hollowed-out at 4| so as to provide clearance for the lower left-hand end of the base member 28 on which the cam 21 is supported.

The elements which move as a result of the rotation of the shaft 52 are shown in their upwardly extended positions in Figure 7. It will be noted that these elements have moved through approximately 90 degrees, carrying with them the diamond nib 9 which is caused to dress the rounded surface 1 of the grinding wheel. In order to insure accuracy in the size of the radius of this rounded surface-not only must the axis of the shaft 52 exactly coincide with the center point 8 when the shaft will have reached the position at which the barrel casting 56 abuts the adjustable stop 81, but also the curvature of the circular notch .0 must have a center which also coincides with the center point 8. As the shaft 52 rotates clockwise (Figure 8) in order that the diamond nib 9 will generate an arc corresponding to the curved surface 1, the dog 54, which is secured to the enlarged portion 5I of the shaft, is caused to move downwardly and to strike the trip lever I02. The fact that the dog moves in such a path is indicated in Figure 8 by the dotdash line I02.

It has been explained that as the lever I02 is moved upwardly (Figure 8) the latch IIJ'I releases the collar 96, thus unloading the spring 98 and causing the shaft or rod 94 to move to the right.

This movement changes the position of the piston I in the pilot valve 89 in such a way that pressure fluid from the pipe 9| is now admitted to the left-hand outgoing pipe 90 (Figure 8), causing the piston 11 in the main cylinder to move to the right (Figure 4) Pressure fluid to the right of the piston 11 now finds ready access to the exhaust through the right-hand pipe 90, the valve 89 and. the right-hand pipe 92 to the exhaust pipe 93. Thus the rack 62 is caused to move to the right and the shaft 52 is rotated counterclockwise. The dog 9 is caused to move away from the trip lever I02, but the latter is biased by a spring I2I (Figure 2) which holds it in the 2,294,493 forward position until the collar 95 is again moved to the left, as explained hereinbefore.

The shaft 52 is therefore caused to rotate counter-clockwise through a 90-degree angle while the circular portion of the shoe I03 is contained within the circular notch IIO. When the nib has reached the point directly below the center point 8 (Figures 3 and 8), further movement to the right of the rack 62 will cause the shaft 52 to move only in the longitudinal direction, due to the fact that the edge I22 of the -shoe will have reached the edge I23 of the circular notch, thus preventing any further rotation. The shaft, together with the crank 50 and the hub I I, will thereupon be given a longitudinal movement, and the diamond nib will describe a vertical movement corresponding to the shape of the cam 2.1. When the nib has reached the nearer edge of the grinding wheel 4, as seen in Figure 8, the right-hand end of the shaft I6 will have contacted the wall 80 of the cylinder 18, and suiiicient back'pressure will be built up to'the left of the piston as might cause a relief valve (not shown) to operate and to prevent further pressure fluid from being delivered to the pipe 9|.

From the foregoing it is evident that I have disclosed a dressing tool attachment in which the diamond nib 9 is caused to move over the irregular surface of a grinding wheel, and then to follow that surface over a rounded edge, finally causing the nib to retrace its movement over the same path. Thus the wheel is dressed twice, the

diamond nib moving in two directions and automatically coming to a stop when the nib has reached one end of its travel in order to reverse its path of movement, and coming to a permanent stop on conclusion of the complete dressing excursion. It is apparent that the cam 21 may be provided with any shape or contour to accommodate the most intricate configuration that the periphery of the wheel may take, and that the dressing tool will faithfully follow the path determined by the cam. Inasmuch as the rack 62 is given a constant velocity of movement in the longitudinal direction, the diamond nib is caused to dress the wheel at a constant speed regardless of the intricacies of the irregularity of shape which tend to give to the dressed surface its optimum grinding quality as determined by the dressing speed. g

It will be understood that I desire to comprehend within. my invention such modifications as come within the scope of the claims.

Having thus fully described by invention, what I claim as new and desire to secure by Letters 7 Patent, is:

1. A grinding machine attachment for causing a dressing tool to be moved over a grinding wheel which has an irregular periphery terminating in a rounded edge, said attachment comprising a cam and a follower to which the dressing tool is attached, said cam having a.configuration which corresponds to that of the wheel periphery, means for drawing said follower across the cam in order to cause the dressing tool to dress the periphery of the wheel, and means for moving said cam and follower over a path corresponding to the rounded edge of the wheel to continue the dressing function of said tool.

2. A grinding machine attachment for causing a dressing tool to be moved over a grinding wheel which has an irregular periphery terminating in a rounded edge, said attachment comprising a cam and a follower to'which the dressing tool is attached, said cam having a configuration which corresponds to that of the wheel periphery, means for maintaining the cam stationary and for moving the follower across the cam in order to cause the dressing tool to dress the pe riphery-of the wheel, and means for moving both the cam and the tool through a circular path in order to cause the tool to pass over the rounded edge of the wheel to continue its dressing function.

3. A dressing attachment for a grinding wheel which has a rounded edge, said attachment comprising a dressing tool secured to a rod slidably carried on a base including a cam means for moving said rod-with respect to said base to pause the tool to dress the periphery of the wheel,

and means for moving the rod, base and cam as a unit to cause the tool to dress the rounded edge of the wheel.

4. A dressing attachment for a grinding wheel which has a rounded edge, said attachment comprising a dressing tool secured to a slidable member mounted on a base, means for moving the slidable member and base as a unit from one edge of the wheel toward the rounded edge and simultaneously moving the slidable member with respect to the base to accommodate irregularities in the periphery of the wheel surface, means for terminating the further movement of the slidable member and base in a direction along the periphery of the Wheel, and means for moving the slidable member and base as a unit about the rounded edge of the wheel, said dressing tool being in contact with the wheel during all of the movements of the slidable member whereby the periphery of the wheel including the rounded edge is dressed.

5. A ,grinding machine attachment for causing a dressing tool to be moved over a grinding wheel surface terminating in a rounded edge, said attachment comprising a cam and follower to which. the dressing tool is secured, said follower being secured to a crank terminating in a shaft, a pinion on said shaft meshingwith a rack, means for moving the rack and pinion as a unit in the direction of the length of the rack to cause the dressing tool to be moved over the periphery of the grinding wheel, and means for moving the pinion with respect to the rack to rotate said shaft whereby the dressing tool is moved over the rounded edge of the grinding I wheel.

tool to be moved over the periphery of the grinding wheel, and means for moving the pinion with respect to the rack to rotate said shaft whereby the dressing tool is moved over the rounded edge of the grinding wheel.

7. A grinding machine attachment for causing a dressing tool to be moved over an irregular grinding wheel surface terminating in a rounded edge, said attachment comprising a cam and follower to which the dressing tool is secured, said follower being secured to a crank terminating in a shaft, a pinion on said shaft meshing with a rack, means for moving the rack and pinion as a unit in the direction of the length moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said means comprising a shaft, a crank mounted thereon and carrying the dressing tool, said shaft and crank being adapted to move as a unit in a direction across the wheel periphery to cause said tool to dress the outer portion of the wheel periphery, means for restraining the shaft and crank from rotation during the period of time that the tool'is moving across the outer portion of said periphery, said shaft and crank beingthen adapted to rotate through an angle determined by the length of arc of the rounded edge ofthe wheel.

9. A dressing attachment for a grinding wheel which has a rounded edge, said attachment comprising a dressing tool secured to a rod slidably carried on a sleeve through which the rod extends to rest on a cam, means for moving the sleeve in a direction along the length of the cam whereby. the rod is caused to trace the shape of the cam in terms of a corresponding movement of the dressing tool along the periphery of the wheel, and means for moving the sleeve and contained rod, also the cam around an arc corresponding to the curvature of the dressing tool around the rounded edge of thewheel, whereby the outer periphery of the wheel is dressed in accordance with the configuration of the cam surface and the rounded edge of the round surface of said shoe being adapted to rotate in a circular notch in said template at the termination of the movement over the flat surface of the template.

12. A grinding'machine attachment for causing a dressing tool to be moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over-the rounded edge of the wheel, said means including a shaft-carrying a crank at one end and a shoe at the other end, said dressing tool being mounted on said crank, said shoe having a cylindrical portion provided with a fiat surface and resting on a template having a fiat horizontal surface terminating in a circular notch, means for moving the shoe along the fiat surface of the template in order to cause the shoe,

shaft, crank and dressing tool to move in a horizontal plane until the shoe reaches said notch,

and means for rotating the shaft, crank and dressing tool when .the cylindrical portion of the shoe fits itself within the circular notch of the template whereby the dressing tool is moved first in a horizontal direction and then in a circular path to dress the outer periphery of the grinding wheel and its rounded edge. t

13. A grinding machine attachment for cans-- ing a dressing tool to be moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said means including a shaft carrying a wheel is dressed to a shape determined by the curved path through which the dressing tool is moved.

10. A grinding machine attachment for causing a dressing tool to be-moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said means including a shaft and a crank mounted thereon carrying the dressing tool, a pinion secured to said shaft and adapted to be actuated by a rack, means for moving the rack while preventing rotation of the shaft whereby the shaft, crank and dressing tool are moved as a unit in a horizontal direction across the periphcrank at one end and a shoe at the other end, said dressing tool being mounted on said crank, a pinion secured to the shaft intermediate the crank and shoe, a rack for actuating the pinion, said shoe having a cylindrical portion provided with a flat surface and resting on a template having a fiat horizontal surface which terminates in a cirery of the wheel, said rotation-preventing means wheel and then over the rounded edge of the wheel,

said means including a shaft and a crank mounted thereon carrying the dressing tool, a pinion secured to said shaft and adapted to be actuated by a rack, means for moving the rack while preventing rotation of the shaft whereby the shaft, crank and dressing tool are moved as a unit in a horizontal direction across the periphery of the cular notch, means for moving said rack in a horizontal direction in order to move the shoe along the flat surface of the template thus causing the shoe, shaft, crank and dressing tool to move in a horizontal plane until the. shoe reaches said notch, said rack being adapted to be moved further in order to cause the shaft, crank and dressing tool to be rotated when the cylindrical portion of the shoe fits itself within the cir-' cular notch of the template, and means for reversing the direction of travel of the rack in order to cause the shaft, crank and" dressing tool to rotate in the opposite direction and later to cause the shaft, crank and dressing tool to'move in the horizontal plane in the opposite direction, whereby the dressing tool is moved first in the horizontal direction and then in a circular path to dress the outer periphery of the grinding wheel and its rounded edge and later the dressing tool is caused to retrace these two paths but in the opposite direction.

14. A grinding machine attachment for causing a dressing tool to be moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said rotation-preventing means being renwheel, said means including a shaft carrying a pinion, and means including a template on which the shoe rests for preventing rotation of the shaft as the rack is moved whereby the movement of the rack is translated to the shaft as the planar movement normal to the axis of the shaft 50 as to carry the dressing tool over the outside periphery of the wheel.

15. A grindingmachine attachment for causing a dressing tool to be moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said means including a shaft carrying a crank at one end and a shoe at the other end, said dressing tool being mounted on said crank, a pinion secured to the shaft intermediate the crank and the shoe, a rack for actuating said pinion, and means including a template on which the shoe rests for preventing rotation of the shaft as the rack is moved whereby the movement of the rack is translated to the shaft as the planar movement normal to the axis of the shaft so as to carry the dressing tool over the outside periphery of the wheel, said template having a shape such that at the termination of the planar movement the shoe is permitted to rotate in response to further movement of the rack in order to cause the dressing tool to move over the rounded edge of the wheel.

16. A grinding machine attachment for causing a dressing tool to be moved over a grinding wheel surface which has a rounded edge, means for moving said tool over the periphery of the wheel and then over the rounded edge of the wheel, said means including a shaft carrying a crank at one end and a shoe at the other end, said dressing toolbeing mounted on said crank, a pinion secured to the shaft intermediate the crank and the shoe, a rack for actuating said pinion, means including a template on which the shoe rests for preventing rotation of the shaft as the rack is moved whereby the movement of the rack is translated to the shaft as the planar movement normal to the axis of the shaft so as to carry the dressing tool over the outside periphery of the wheel, said template having a shape such that at the termination of the planar' movement the shoe is permitted to rotate in response to further movement of the rack in order to cause the dressing tool to move over the rounded edge of the wheel, and means for reversing the movement of the rack when the dressing tool has reached the end of the rounded edge of the wheel whereby the dressing tool is caused to retrace its path over the rounded edge of the wheel and then over the outside periphery of the wheel in order to dress the wheel twice.

17. A grinding machine attachment for causing a. dressing tool to be moved over a grinding -wheel surface which has a rounded edge, means for moving said tool over .the periphery of the wheel and then over the rounded edge of the wheel, said means including a shaft carrying a crank at one end and a shoe at the other end,

said dressing tool being mounted on said crank,

a pinion secured to the shaft intermediate the crank and the shoe, a rack for actuating said pinion, means including a template on which the shoe rests for preventing rotation of the shaft as the rack is moved whereby the movement of the rack is translated to the shaft as the planar movement normal to the axis of the shaft so as to carry the dressing tool over the outside periphery of the wheel, said template having a shape such that at the termination of the planar movement the shoe is permitted to rotate in response to further movement of the rack in'order to cause thedressing tool to move over the rounded edge of the wheel, means for reversing the movement of the rack when the dressing tool has reached the end of the rounded edge of the wheel whereby the dressing tool is caused to retrace its path over the rounded edge ofthe wheel and then over the outside periphery of the wheel in order to dress the wheel twice, and a doubleacting fluid cylinder for actuating the rack first in one direction and then in the other direction, the direction of the pressure fluid admitted to said cylinder being controlled by a pilot valve which in turn is controlled by a dog secured to the shaft and operating in response to a predetermined rotation of the shaft to reverse the operation of said pilot valve.

JOHN C. WILSON.

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