US 3299579 A
Description (OCR text may contain errors)
Jan. 24, 1967 v JACQBSON 3,299,579
GRINDING MACHINE Filed Jan. 1'7, 1964 4 Sheets-Sheet 1 FIG.
ALDEN H. JACOBSON INVENTOR.
A. H. JACOBSON Jan. 24, 1967 GRINDING MACHINE 4 SheetsSheet Filed Jan. 17, 1964 FIG. 3
ALDEN H. JACOBSON INVENTOR.
Jan. 24, 1967 H, JAICOVBSON 3,299,579
I GRINDING MACHINE Filed Jan. 17, 1964 4 Sheets-Sheet 5 FIG. 5
ALDEN H. JACOBSON INVENTOR.
Jan. 24, 1967 JACOBSON v 3,299,579
GRINDING MACHINE Filed Jan. 17, 1964 4 Sheets-Sheet 4 ALDEN H. JACOBS ON INVENTOR.
Patented Jan. 24, 1967 3,299,579 GRINDING MACHINE Alden H. Jacobson, Paxton, Mass., assignor to The Heald Machine Company, Worcester, Mass, a corporation of Delaware Filed Jan. 17, 1964, Ser. No. 338,507 Claims. (Cl. 51-115) This invention relates to a grinding machine and, more particularly, to apparatus arranged to finish opposite flat, parallel surfaces of a workpiece by the abrasion process.
In the grinding of parallel, flat surfaces, such as the sides of discs and the ends of bearing races, it is common practice to pass the workpiece between two grinding wheels whose side surfaces are parallel, so that the two surfaces of the workpiece are ground flat and parallel at the same time in one operation. However, in conventional grinding processes, it is common practice to rough grind a surface with an abrasive wheel of a particular hard quality, to subject it to an intermediate grinding with a wheel of intermediate hardness, and then to finish grind it with a soft wheel. With the prior art machines, therefore, it has been necessary to pass the workpiece through approximately three machines before it is finally completed in the last fine grind machine. This not only involves the use of three such grinding machines but also involves a considerable amount of handling in between so that the process becomes quite expensive. Furthermore, it is necessary and, of course, difficult to adjust the three machines so that they remove exactly the right amount of material from the surface to be finished before the workpiece has passed on to the next machine. Furthermore, since the workpiece is introduced at one part of the periphery of the two grinding wheels and leaves the space between the two wheels at another part of their periphery, the surface feet per minute speed of the wheel is fast at the beginning of the grinding cycle, slow in the intermediate part of the grinding cycle, and then fast at the end, so that the quality of the grinding is difficult to control.
These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.-
It is, therefore, an outstanding object of the invention to provide a grinding machine in which various stages of abrasive finishing can be carried out in a single cycle on a single machine.
Another object of this invention is the provision of a flat grinding machine which will perform an abrasive finishing operation on opposite, flat, parallel sides of a workpiece without handling between the rough, intermediate, and finish grinding portions of the cycle.
Another object of the present invention is the provision of a fiat grinding machine for grinding the opposite sides of discs or the ends of bearing races, which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service with a minimum of maintenance.
It is another object of the instant invention to provide a grinding machine which is capable of performing finishing operations on a workpiece between two abrasive wheels, while permitting the workpiece to rotate due to the abrasive action during the roughing and intermediate portions of the cycle, but which restricts the workpiece against rotation during a finishing portion of the cycle.
It is a further object of the invention to provide a grinding machine for finishing opposed flat parallel sides of a workpiece to a high degree of dimensional accuracy and quality of finish.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.
The character of the invention, however, may be best understood by reference to one of its structural forms as illustrated by the accompanying drawings in which:
FIG. 1 is a plan view with portions removed of a grinding machine embodying the principles of the present invention,
FIG. 2 is a vertical sectional View of the invention taken on the line II-II of FIG. 1,
FIG. 3 is a side elevational view of the invention,
FIG. 4 is a front elevational view of the invention,
FIG. 5 is an enlarged plan View of a portion of the invention taken on the line VV of FIG. 3,
FIG. 6 is a vertical sectional view of the taken on the line VIVI of FIG. 5,
FIG. 7 is a vertical sectional view of the taken on the line VII-VII of FIG. 5,
FIG. 8 is a vertical sectional view of the taken on the line VIIIVIII of FIG. 5, and
FIG. 9 is a vertical sectional view of the taken on the line IX--IX of FIG. 5.
Referring first to FIGS. 1, 2, 3, and 4, which best show the general features of the invention, the grinding machine, indicated generally by the reference numeral 10', is shown as having a base 11 on which are mounted two circular abrasive wheels 12 and 13, which are rotatably carried in the base and which are driven by motors 14 and 15, respectively. The base 11 is formed in two parts and is generally L-shaped (as observed from the position of the operator 16 and as shown in FIG. 1) with a tall vertical portion 17 and a table portion 18. The vertical portion 17 is provided with vertical parallel ways 19 and 21 on which are slidably mounted an upper wheelhead 22 on which the wheel 12 is rotata-bly carried and a lower wheelhead 23 in which the lower wheel 13 is rotatably carried. The lower wheelhead carries a hollow spindle 24 having a central circular bore 25 which is larger than the largest workpiece to be ground. As is evident in FIG. 4, at the bottom of a hollow spindle as it emerges from the lower wheelhead 23, is arranged a chute 26 in which is carried an endless belt conveyor 27. Movement of the upper and lower wheelheads 22 and 23 up and down on the ways 19 and 21 is brought about by means of a feed screw 28 driven by a gear motor 29. Mounted at the rear of the base 11 is a coolant pump and motor 31, while at the front of the machine is attached a directcurrent motor-driven dresser 32 which operates to dress the working surfaces 33 and 34 of the wheels 12 and 13, respectively. Mounted on a vertical pivot on the top of the table portion 18 is a feed arm 35.
Referring to FIG. 2, it can be seen that the wheel 12 is made up of three concentric portions 36, 37, and 38. The outer portion 36 uses a roughing grade of abrasive and would be considered a hard wheel; its portion of the working surface 33 is tapered. The intermediate portion 37 uses an intermediate grade of abrasive and hardness, is tapered, and is used for intermediate grinding. The inner or finish portion 38 uses a fine abrasive and a soft wheel quality for finishing the workpiece. Furthermore,
invention invention invention invention its portion of the working surface 33 is flat or radial to the axis of rotation. The wheel 13 is similarly formed with an outer portion, an intermediate portion, and an inner portion which are manufactured with roughing, intermediate, and finish abrasive qualities; of course, the outer and intermediate portions have tapered surfaces, while the inner portion has a flat radial surface.
As is evident in FIG. 3, the machine is provided with hand Wheels 39 and 41 which permit hand adjustment and movement of the upper and lower wheel'heads, respectively, by manual operation. Fastened on the side of the vertical portion 17 of the base is a control box 42 to assist in operating the machine. Located beside the upper wheelhead 22 is a gage 43 showing at all times the position of the wheelhead on the sides or ways. Similarly, a gage 44 is associated with the lower wheelhead 23 and shows its position.
A loading chute 45 is mounted over the table portion 18 outside of the periphery of the wheels 12 and 13. A wheel wear light 46 is mounted at the top of the control box 42. A coolant pipe 47 enters the top of the upper wheelhead 22 concentric with the spindle thereof to provide lubricant for the grinding operation.
FIG. shows a sectional view taken on the line V-V of FIG. 3 and shows the apparatus as looking down on top of the lower wheel 13. The feed arm 35 is pivoted on a vertical shaft 48 located at the rear of the table portion 18 of the base. The feed arm 35 is of a plate-like configuration and is segmental in form. The edge facing the wheel 13 is formed with a generally circular recess 49 which, in the position shown in solid lines, underlies the chute 45 in position to receive a workpiece 51. The recess is provided with hardened metal tungsten carbide blocks 52 and 53 which are arranged so that their surfaces form a right angle and a V, which V is bisected by a tangent to a circle having the axis of the shaft 48 as its center and having a radius equal to the distance from the axis of the shaft 48 to the axis of the workpiece 51. A narrow slot 54 enters the recess 49 and is of a width slightly less than the smallest workpiece to be ground. The feed arm 35 is provided with an oppositely-disposed arm 55 which extends from the diametrically-opposite side of the shaft 48 and is provided with a tangential slot 56. A cap screw 57 passes through the slot 56 into one end of a lever 58. The other end of the lever 58 is connected by a cap screw 59 to a rotatable disc 61 which will be described more fully hereinafter but which is driven by a gear motor 62. Bolted to the lever 58 is a finger 63 carrying at its outer end a cam roller 64. Also pivotally mounted on the vertical shaft 48 is a clamp arm 65 of a segmental configuration having an extending finger 66. The clamp arm is provided with a circular outer peripheral edge 67 which is concentric with the axis of the shaft 48 and which is carried in a guide 68. The clamp arm 65 is also provided with a hardened metal block 69 which is in position to be engaged on occasion by the roller 64. The feed arm 35 is also provided with a concentric circular peripheral edge 71 which is carried in a guide 72 mounted in the upper surface of the table portion 18 of the base.
FIG. 6 shows the equipment associated with the shaft 48 which is fixedly mounted in the base 11. The shaft is provided with a ball bearing 73 by which means it is pivotally mounted a hub 74 on the upper surface of which is mounted the feed arm 35 with its extension or arm 55. On the upper part of the shaft is carried the clamp arm 65 which has a thick portion 75 sloping down into the outboard operative portion which is quite thin and platelike to permit insertion between the two abrasive wheels.
FIG. 7 shows a vertical post 76 which extends upwardly from the table portion 18 of the base and is provided with a laterally-extending guide plate 77 which serves to extend over the surface of the feed arm 35 as it proceeds into position between the abrasive wheels; it, therefore, prevents the workpiece 51 from leaving the recess 49 until the workpiece is well between the abrasive wheels.
FIG. 7 shows particularly well the manner in which the guide 72 embraces and holds in a constrained path the plate-like feed arm 35. A triangular web 78 extends between the upper portion of the post 76 and the guide plate 77 to hold it rigidly in place in cantilever fashion.
As is clearly shown in FIG. 8, the finger 63 is bolted to the upper side of the lever 58 so that its roller is well above the upper surface of the lever; it is then in position to engage the block 65 of the clamp arm 65.
FIG. 9 shows the motor 62 with its output shaft 79 to which is keyed the disc 61. The pivot 59 is spaced from the axis of the shaft '79 and is connected to one end of the lever 58. The other end of the lever is attached by the cap screw 57 through a ball bearing 81 to the arm 55 of the feed arm 35. Clearly evident in this figure are set screws 82 and 83 which locate the cap screw 57 in the slot 56 to permit the adjusting of the position of the feed arm 35.
The operation of the grinding machine It will now be readily understood in view of the above description. The workpieces 51 are stacked vertically one above the other in the chute 45 and pass downwardly by gravity through the chute into the operative part of the machine. At the beginning of a cycle, the feed arm 35 is in the position shown in solid lines in FIG. 5. At that time, a workpiece 51 at the bottom of the stack falls into the recess 49. The motor 62 rotates the disc 61 continuously and, as the disc rotates, it carries the feed arm 35 from the outer position shown into an inward position where the recess 45 overlies the bore 25 in the vertical spindle 24 and it also arrives at an intermediate position such as that shown in dotted lines in FIG. 5. The lever 58 acts as a crank arm and serves, of course, to rotate the feed :arm 35 back and forth between the two extreme positions, i.e., the first position underlying the chute 45 and the second position wherein the recess 49 overlies the bore 25 at which time the workpiece 51 falls downwardly through the spindle. As the feed arm 35 swings clockwise from the position shown in FIG. 5, it passes under the guide plates 77; the workpiece 51 is held in place until the arm carries it well between the two abrasive wheels 12 and 13. As the feed arm continues to rotate counterclockwise, the workpiece is introduced between the wedge-shaped roughing portions 36 of the abrasive wheels. The end surfaces are ground down to the dimensional spacing between the abrasive wheels at the junction between the roughing portion and the intermediate portion. As the feed arm 35 continues to rotate, the workpiece is carried between the intermediate grinding portions 37 and its thickness is further reduced, Finally, the feed arm carries the workpiece through the finish portions 38 and its final dimension and quality of finish is there determined before it is carried outwardly of this innermost zone and falls downwardly through the bore 25 in the spindle 24. Now, as the workpiece is carried through the portions 36 and 37, it is rotated, because of the fact that the forces presented to the workpiece by the inner portions of the wheel are greater than those presented by the outer portions of the wheel. However, it is desirable to cause the workpiece to rotate while it is being rough and intermediate ground to cause even finishing of the surfaces. However, during the finishing operation, it is desirable that the workpiece shall not move. For that reason, as the disc 61 rotates, eventually, the roller 64 and the finger 63 contact the block 69 on the clamping arm 65 and the finger 66 of the clamping arm enters the slot 54 in the opening 49 of the feed arm 35. The finger then strikes the workpiece 51 and forces it back against the blocks 52 and 53, so that the workpiece is clamped in place and is not permitted to rotate. Then, the feed arm 35 and the clamp arm 65 rotate clockwise together, carrying the workpiece with them. Eventually, they reach the position where the workpiece overlies the bore 25 in the spindle 24 and the feed arm 35 begins its counter-clockwise or backward motion. As it does so, the clamp arm 65 remains behind because of the friction in a clutch 84 associated with the clamping arm 65 and the fixed shaft 48 (see FIG. 6). Now, when the feed arm has moved away from the clamp arm 65 a slight distance, the finger 66 no longer presses the workpiece against the blocks 52 and '53- and the workpiece is free to fall down the bore 25. It lands, of course, on the upper surface of the conveyor belt 27 and is carried down the chute 26 to the exterior of the machine. The feed arm 35 continues to move in a counter-clockwise direction until it arrives at its original position where it picks up another workpiece 51 from the bottom of the stack. This bottom workpiece of the stack, incidentally, has, in the meanwhile, rested on the upper surface of the plate-like feed arm 35 while its predecessor was being ground. The arm 35, therefore, serves a dual purpose as a workpiece feeding mechanism and a support for the workpiece during grinding.
In the preferred embodiment of the invention, the abrasive wheels 12 and 13 are 24 inches in diameter. The wheelheads 22 and 23 can be retracted to dressing position either by use of a push button on the control box 42 or by use of hand wheels 39 and 41; they can be advanced to the grinding position in the same manner. In feeding, a graduated handwheel is geared to an ACME feed screw 28. The advance of the slides is measured in increments of /2 of .0001". When power feed is used, there are safety limit switches (not shown) provided to stop the power at the proper time and there .positive mechanical stops are also provided to prevent feed-nut damage. The machine is an entirely mechanical apparatus with no hydraulic or air-operated mechanisms. A coolant tank 85 supplies the coolant wheels through the pipe 47 entering the upper part of the upper wheelhead 22. The machine is automatically stopped when the wheels are worn to a minimum and the wheel wear light 46 comes on. The machine cycle time is controlled by the direct current motor 62 that operates the feed arm 35 through the crank motion consisting of the disc 61 and the lever 58. In the preferred embodiment, the production rate is variable from 60 parts per hour to 2800 parts per hour and is capable of grinding bearing races in sizes from inch in diameter to 3% inch in diameter, the width of the race being variable from of an inch to 5 inches. A
The wheels, of course, are dressed with a taper and a flat, the flat being in the center where the workpiece is to be finished. The taper can be varied, of course, depending on the amount cf stock to be removed. The r.p.m. of the wheels can be varied by making belt-andpulley changes between the motors 14 and 15 and their respective wheelheads 22 and 23. The maximum speed in the preferred embodiment is 1200 r.p.m., producing 7600 surface feet per minute at 24 inch diameter of the wheel. It should be noted that, if the opposed faces of the workpiece are different, the two wheels may have different speeds. The smaller the area of contact the lower the rpm. is a general rule. This situation would exist in the case of the outer races of taper roller bearings.
The dresser 32 is mounted on the machine base and is push button operated. A gear reducer and a direct current motor extends and retracts this unit. The direct current is provided to extend the dresser at slow speed and to retract at fast speed or to vary the dresser rate for finer finish. The dresser has a pivot adjustment calibrated in thousandths; this adjustment is used to dress the taper and the flat on the wheels. Oluster diamonds are used for this operation and there is a hole provided for the cluster diamond to dress the CD. of the wheel, but, of course, this is only used when new wheels are installed to balance, if there is any outside diameter runout.
It is obvious that min-or changes maybe made in the form and construction without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.
The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:
1. A grinding machine for finishing opposite parallel fiat surfaces of a workpiece, comprising (a) abase,
(-b) a spindle rotatably mounted in the base and having a passage therethroug-h capable of receiving workpieces seriatim with their fiat surfaces perpendicular to the axis of the spindle,
(c) a first abrasive wheel mounted on one end of the spindle and having a grinding face generally perpen dicular to the spindle axis,
(d) a second abrasive wheel rotatably mounted on the base and having a grinding face spaced from and in opposition to the grinding face of the first abrasive wheel,
(e) means for driving the abrasive wheels, and
(f) a feed arm movable in a plane between the faces of the wheels to carry the workpiece on a path between the said passage in the spindle and the outer peripheries of the wheels at a controlled rate, whereby the said passage serves as a feed for movement of the workpieces relative to said path.
2. A grinding machine as recited in claim 1, wherein the opposed surfaces of the abrasive wheels are tapered in the radial direction.
3. A grinding machine as recited in claim 1, wherein each abrasive wheel is formed with a plurality of annular concentric zones of differing abrasive qualities.
4. A grinding machine as recited in claim 1, wherein the feed arm is mounted on the base for carrying a workpiece between the opposed faces of the abrasive wheels along a substantially radial line extending between their peripheries and the axis of the hollow spindle.
5. A grinding machine as recited in claim 2, wherein the wheel surfaces are tapered from a relatively large spacing at their peripheries to a relatively small spacing at a position intermediate of the periphery and the center and the surfaces are flat and parallel from the said position to the center.
6. A grinding machine as recited in claim 4, wherein a clamping arm is provided to lock the workpiece against rotation relative to the feed arm during a portion of the movement of the feed arm and workpiece between the wheels.
7. A grinding machine as recited in claim 3, wherein there are three zones, the outermost zone being of rough grinding quality, the next zone being of intermediate grinding quality, and the innermost zone being of finish quality.
8. A grinding machine as recited in claim 7, wherein the outermost and next zones are formed with a slight conical surface to be closest to one another toward the center, and the innermost zones are formed with flat parallel surfaces.
9. A grinding machine as recited in claim 8, wherein a feed arm is provided to carry the workpiece radially from the peripheries of the wheels to the center successively through the zones, the workpiece being held loosely so that it can rotate about an axis parallel to the spindle axis as it passes through the outermost and the next zone, but being restrained against such rotation as it passes through the innermost zone.
10. A grinding machine for finishing flat parallel surfaces of a workpiece, comprising (a) a first and a second abrasive wheel mounted for rotation on a common axis with face surfaces directed toward one another, at least one of the wheels being provided with a central passage large enough to pass a workpiece and (b) a feed arm movable in a plane between the wheels for carrying the workpiece substantially radially between the said face surfaces at a controlled rate, the wheels being formed with concentric zones of differing grinding quality, said passage intersecting the said plane, lying in the path of the arm, and pro- 7 8 viding for feeding movement of the workpiece rela- 2,595,872 5/1952 Morrison 51111.1 tive to said plane. 3,067,551 12/1962 Maginnis 51-289 References Cited by the Examiner FOREIGN TE UNITED STATES PATENTS 5 247,181 8/ 1926 Great Britaln.
910,655 11/1962 Great Britain. 1,640,715 8/1927 Morton 51-114 1,828,663 10/ 1931 Jopp 51--112 HAROLD D. WHITEHEAD, Primary Examiner.