US3024578A

US3024578A - Ball grinder

Info

Publication number: US3024578A
Application number: US70514A
Authority: US
Inventors: Nick M Mushkin
Original assignee: COLUMBIA PLASTICS CORP
Current assignee: COLUMBIA PLASTICS Corp
Priority date: 1960-11-21
Filing date: 1960-11-21
Publication date: 1962-03-13
Anticipated expiration: 1979-03-13

Description

March 13, 1962 N. M. 'MUSHKIN BALL GRINDER 3 Sheets-Sheet 2 Filed NOV. 21, 1960 INVENTOR. Nick M Mush (in March 13, 1962 3 SheetsSheet 5 Filed Nov. 21, 1960 m n k 5 M n y T S 1 40 m t N A I 2d M L N% Y B v T 8 (o 2 B 4* 4. u 8

3,024,578 Patented Mar. 13, 1952 Filed Nov. 21, 1960, Ser. No. 70,514 8 Claims. (Cl. 51-117) This invention relates to a novel machine for grinding the exterior surfaces of spherical balls. The machine was specifically designed to grind bowling balls, which require a smooth surface with a high degree of roundness to insure accuracy and control when used on a bowling alley. However, other applications of this machine may be evident where spherical objects of a substantial size require a machined surface.

It is an object of this invention to provide a machine requiring no adjustment or attendance during the grinding operation. After being initially set, the machine will grind the sphere to the desired diameter and turn itself off. It is another object of this invention to provide a machine which is simpleand economical, having no complicated or expensive parts, but permitting the attainment of a high degree of accuracy in the machined spherical surface.

The invention briefly contemplates a pair of angularly disposed interior conical grinding heads mounted on a supporting framework and adapted to contact the ball or object being ground. One of the heads is to be rotated and the other of said heads is to be idle. The non-driven head is spring biased and pivotally mounted so as to insure full contact of the ball by both grinding surfaces. In order to uniformly grind the ball, the pressure exerted by the ball on each head is continuously varied by an exterior control. Manual and automatic controls are provided for practical purposes.

The invention is fully disclosed in the following specification and the accompanying drawings which illustrate the basic machine and include two alternate mechanisms for effecting the necessary pressure cycle between the ball and the grinding heads. These forms are not exhaustive of the many practical structures embodied in the invention, which is limited only by the annexed claims.

In the drawings:

FIGURE 1 is a front view of a grinding machine constructed according to the present invention, showing the machine in the operation of spherically grinding a bowling ball;

FIGURE 2 is a fragmentary view of the rocking control structure as seen along line 2-2 in FIGURE 1;

FIGURE 3 is an end view of the machine shown in FIGURE 1 taken from the right hand side of FIGURE 1;

FIGURE 4 is an end view of the machine shown in FIGURE 1 taken from the left hand side of FIGURE 1;

FIGURE 5 is an enlarged view of the automatic shutoff switch assembly as seen along line 5-5 in FIGURE 1;

FIGURE 6 is a diagrammatic vertical sectional view taken through the central axes of the grinding heads and showing the ball position in dashed lines;

FIGURE 7 is a front view of a second embodiment of the invention, showing the machine in the operation of spherically grinding a bowling ball, with a portion of the machine frame being broken awa FIGURE 8 is a vertical sectional view taken through the central axis of a grinding head in FIGURE 7 and through its intake hose; and

FIGURE 9 is a somewhat diagrammatic view of the control valve, taken along line 9-9 in FIGURE 7.

The invention is specifically designed to produce fine spherical bowling balls from rough spherical castings.

Before use of the instant machines, one must grind away any flashing or flanges on the casting in order to provide a roughly spherical surface. This ball is then placed in the machine and is automatically ground to the desired spherical radius. The ball can be cooled during the grinding operation by any suitable fluid, which is carried off by splash guards 19 mounted on the frame of the machine.

The first form of this invention is illustrated in FIG- URES 1-6. In this embodiment, the cyclical variation in pressure exerted between the two heads of the grinder is effected by pure mechanical means. The general supporting framework 10 consists of four legs 11 connected by intermediate horizontal braces 12 and top side and

end angle irons

13, 14 respectively. Mounted at the left hand end of framework 10 as seen in FIGURE 1 is a superstructure 15 which is merely an enclosed box made of sheet material and rigidly secured to the frame- Work 10. For convenience, the top 16 of superstructure 15 is set at an angle to the horizontal, in this case the angle is 30 degrees.

A mounting shaft 17 is rotatably journalled by two

bearings

18, 20 fixed to the side wall 21 of superstructure 15. The top bearing 20 is an axial thrust bearing which cooperates with two collars 22 fixed to shaft 17 to absorb axial thrust exerted on the shaft 17. Shaft 17 is also positioned at an angle of 30 degrees to the horizontal and its axis is preferably located in a vertical plane. The shaft 17 is driven at desired speed by means of a large pulley 23 on shaft 17 and a small pulley 24 driven by an electrical motor 25 mounted on the top 16 of superstructure 15. The two

pulleys

23, 24 are drivingly connected by a belt 26.

At the opposite end of shaft 17 is fixed a grinding head 27. The detail of grinding head 27 is seen in FIGURE 6. It consists of a cup-like cylindrical shell 23 which mounts an abrasive conical interior element 30. The abrasive element 30 is replaceable. l't preferably has a conical surface making an angle of 43 degrees with the conical axis. The base of the conical surface is less in diameter than the desired finished diameter of the ball, which is shown in dashed lines and is indicated as 31. The interior conical surface 29 of element 30 extends to the wall of shell 28.

A second superstructure 33 is fixed to framework 10 at the right hand end seen in FIGURE 1. This superstructure 33 has a vertical wall 34 adjacent the inner edge of side angle iron 13 and an angularly positioned plate 35 which is supported by the side angle irons 13 and a vertical brace 39 at the opposite side of the machine. A second grinding head 36, identical to the head 27, is fixed to a second mounting shaft 37 which is a smooth cylindrical shaft slidably and rotatably mounted in a pivot bearing 38 mounted on wall 34. The pivot bearing 38 is positioned to turn about a horizontal axis. The axis of shaft 37 is preferably mounted in a common vertical plane shared by the axis of shaft 17. Shaft 37 also describes a normal angle of 30 degrees to the horizontal.

Shaft 37 has a collar 40, including an enlarged flange 41, mounted on it adjacent to the head 36. A yoke 42 slidably engages collar 40 and is formed with a central leg 43 positioned along a horizontal line parallel to plate 35. A crank arm 44 is pivoted on plate 35 by a pin 45 and has one end loosely connected to leg 43 by means of a threaded nut 46 and an intermediate compression spring 47. The remaining end of arm 44 is fixed to a post 48 pivoted about pin 45. A second crank arm 50 is fixed to post 48 and is provided with a cam follower 51. Cam follower 51 is biased by a spring 49 to ride on the peripheral edge of an eccentric circular cam 52 fixed to a driving shaft 53. Shaft 53 is driven by a suitable low speed motor-transmission unit 54 bolted to the opposite face of plate 35. The shaft 53 extends through an aperture in plate 35. Thus it can be seen that rotation of shaft 53 will cause

crank arms

44 and 50 to pivot about pin 45, thereby pivoting yoke 42 which will impart slight vertical movement to shaft 37 through contact with the collar 40. Since a ball is to be engaged by the conical base of each

head

27, 36, downward motion of shaft 37 may be impossible. In such case, the motion will be absorbed by spring 47. This is the desired action. Cam 52 is positioned as shown in FIGURE 2 so that the highest elevation of shaft 37 from the horizontal is slightly above the 30 degree position shown in FIG- URE 1. As shaft 53 turns, it will continuously vary the pressure exerted on yoke 42 and shaft 37 by the compression spring 47, and will move shaft 37 in a vertical plane about pivot bearing 38.

In order to bias the grinding heads 36 and 27 together, a compression spring 54 surrounds shaft 37 and abuts both flange 41 of collar 40 and the opposing face of bearing 38. Thus the head 36 is continuously urged toward the center of ball 31, where the axes of

shafts

17 and 37 intersect.

The general operation of the machine is extremely simple, yet it is difficult to describe by words or twodimensional examples due to the spherical action of ball 31. Head 36 is free to rotate about the axis of shaft 37, being retarded only by frictional drag. Head 27 is rotated at a moderate rate of speed by motor 25. The compressive force of spring 54 is great enough to insure proper grinding contact, but not of such magnitude as to cause either

head

27 or 36 to grip the surface of ball 31. Thus both

heads

27 and 36 revolve with respect to the adjacent surfaces of ball 31, the motion of head 36 being imparted by slippage transmitted through the medium of ball 31. If the pressures exerted on each

head

27, 36 by ball 31 were of equal magnitude, each head would merely grind an arcuate spherical groove along its slight line of contact with ball 31. However, the slight, continuous variance in pressure distribution by ball 31 on the two

heads

27, 36 results in a continuous shifting of ball 31 about its own axis in a vertical plane, thus insuring even contact of the total spherical area by both

heads

27, 36. In this manner, a smooth spherical surface is formed as the

heads

27, 36 seek the center of the ball 31.

Since this grinding operation is quite slow due to the slight pressures involved, it is advisable to have a machine which can be left unattended during the grinding operation. This is obtained by a second collar 55 on shaft 37 and having a flange 56. Collar 55 is fixed to mounting shaft 37 below the bearing 38. A toggle switch S7 is mounted on the superstructure 33 and has an actuating arm 58 which abuts the upper side of flange 56. The arm 58 is biased against flange 56 by a spring 60 mounted between arm 58 and an extension 61 fixed to the switch housing 62. Collar 55 is positioned on shaft 37 so as to actuate switch 57 when shaft 37 has moved toward the center of ball 31 the finished distance desired. Switch 57 is wired in series with a second control switch 63 in the power circuit for

motors

25, 54. The switch 63 allows manual control of the machine when desired and can override switch 57 during placement of a new ball between

heads

27, 36.

A foot control for withdrawing head 36 during reloading is provided so as to allow the operator to work with both hands free. A second yoke 64 surrounds collar 55 above flange 56. Yoke 64 is pivoted about a horizontal axis by a pin 65 on side angle iron 13. A spring 66 fixed between the lower end of yoke 64 and the adjacent leg 11 biases the yoke 64 upward, away from the flange 56. This movement is limited by a stop 67 fixed to a corner. brace 68 on framework 10. The yoke can be moved into contact with flange 56 by an integral crank arm 70 which is connected by a light rod 71 to a foot pedal 72 pivoted to a rear leg 11, and extending forward of the machine.

When ball 31 is properly ground, switch 57 will stop the machine. To prevent switch 57 from starting the machine during loading, the operator must open manual switch 63. He then can step on the front end of foot pedal 72 to thereby cause yoke 64 to move shaft 37 downwardly. Ball 31 can then be lifted and a new rough ball placed on

heads

27, 36. Release of pedal 72 and closing of switch 63 will then reset the machine for the next grinding operation.

FIGURES 7 to 9 illustrate a second form of the invention. It has been found advisable to utilize a series of grinding machines having different degrees of abrasiveness to finally produce the smooth surfaced balls required for bowling. This second form of the invention has been found to be particularly well adapted for final grinding operations. Since most of the machine is identical to that shown in FIGURES l to 6, only the new or modified parts will be renumbered and explained.

The two heads 27, 36 are mounted on

shafts

17 and 37 respectively by the bearings previously described. The upper end of shaft 37' is supported by a collar 40 which is supported in turn by a yoke 42' slidably mounted for motion perpendicular to plate 35. Thus the angular positions of both heads 27, 36' are fixed with respect to the horizontal. The grinding faces of head 27, 36' are unchanged from the first embodiment. At the center of each head 27', 36' is an air jet nozzle 73 which opens toward the base of the conical abrasive inner surface of element 30'. Nozzle 73 is connected by an axial bore 74 to a diametric bore 75 in shaft 17' or 37 which opens to an annular groove 76 on the outer surface of the shaft. Groove 76 is covered by a packing gland 77 rotatably sealing the exterior surface of the

shaft

17 or 37. Gland 77 is connected by a hose 78 to a control valve 80. Control valve 80 may be of any conventional design by which compressed air will be alternately delivered to each nozzle 73. A diagrammatic view of one such valve is shown in FIGURE 9. The fixed valve housing 81 has a central opening 82 which is connected to a source of compressed air (not shown). Opening 82 connects to two

valve recesses

83, 84 which slidably mount two

valve elements

85, 86 respectively. The

recesses

83, 84 are connected to the two hoses 78 which control the nozzles in

heads

27, 36 respectively. Elements85, 86 are pivotally connected to a control rod 87 pivoted at its center to housing 81. An eccentric cam 91 pivotally engages valve element 86 through a slot 88 by an offset pin 90. Rotation of cam 91 by a motor shaft 89 will thereby alternately open and block air passage to each

head

27, 36.

The remaining parts of the machine are identical to those previously described, including the switch 57 and foot pedal 72. As head 27 is revolved, head 36 will idle, with slippage between each head 27', 36 and the ball 31. The continuously varying cycle of air distributed to the nozzles 73 will cause a shifting pressure distribution between the

heads

27, 36 by ball 31. This will cause one head to slightly move ball 31 so as to shift its position with respect to the grinding heads 27, 36 to thereby promote even spherical grinding of the ball 31.

Other methods of varying the pressure of the ball on the two grinding heads will be evident to one skilled in the art. Any continuously varying cyclical control will be equally effective and should be considered as being embraced by the claims which follow. The invention is not intended to be limited by the preceding disclosure, except as it is defined in the following claims.

Having thus described my invention, I claim:

1. A device adapted to form a spherical exterior surface cn an initially rough spherical object comprising a pair of angularly opposed grinding heads each including a conical interior abrasive surface having a base diameter less than the desired diameter of the finished spherical surface, independent support means respectively operatively connected to each of said grinding heads adapted to maintain the conical axes of said abrasive surfaces in a common plane wherein said axes intersect one another at the center of the desired spherical surface, drive means operatively connected to one of said grinding heads adapted to rotate said one head about the conical axis of its respective abrasive surface and means adapted to vary the pressure distribution of the object between the two grinding heads in a continuously varying repetitious cycle.

2. The device as defined in claim 1 wherein said last named means comprises mechanical drive means operatively connected to one of said grinding heads adapted to oscillate the head in said common vertical plane.

3. The device as defined in claim 1 wherein said last named means comprises a source of compressed gas, means operatively connecting said source to the center of said conical interior abrasive surface of one of said grinding heads, including a valve adapted to cyclicly isolate said source from the grinding head.

4. A device adapted to form a spherical exterior surface on an initially rough spherical object comprising a supporting framework, a pair of opposed grinding heads each including a conical interior abrasive surface having a base diameter less than the desired diameter of the finished spherical surface, a first mounting shaft fixed to one of said heads at the end thereof opposite to the base of its abrasive surface and in alignment with its conical axis, first bearing means, including an axial thrust bearing, mounted on said framework and rotatabiy journalling said first mounting shaft, a second mounting shaft fixed to the remaining one of said heads at the end thereof opposite to the base of its abrasive surface and in alignment with its conical axis, second bearing means mounted on said framework slidably and rotatably journalling said second mounting shaft, said first and second mounting shafts being positioned with their respective axes located in a common plane intersecting one another at the center of the finished spherical surface, said axes forming an angle with one another of less than 180 degrees, drive means mounted on said framework operatively connected to said one head adapted to rotate said one head about its respective conical axis, biasing means operatively connected between said remaining head and said framework adapted to urge said remaining head toward said center aiong its respective conical axes, and means operatively connected to at least one of said heads adapted to vary the pressure distribution of the spherical object between the two abrasive surfaces in a continuously varying repetitious cycle.

5. The device as defined in claim 4 wherein said second bearing means comprises a swivel mounted bearing positioned on said framework with its swivel axis being located perpendicular to said common plane, said last named means comprising a yoke pivotally mounted on said framework and slidably engaging said second mounting shaft at a location remote from said second bearing, and mechanical drive means operatively connected to said yoke adapted to pivotally oscillate said yoke about its pivotal mount on said framework.

6. The device as defined in claim 4 wherein said last named means comprises a pair of air jet nozzles individually centrally mounted in each of said heads in alignment with the conical axes thereof and opening toward the conical base thereof, air supply means, and cyclical valve means connecting said air supply means and said air jet nozzles adapted to cyclicly supply air to one and then the other of said air jet nozzles.

7. The device as defined in claim 4 wherein said driven means comprises an electrical motor, further comprising a collar fixed to said second mounting shaft, a limit switch mounted on said framework adjacent said second mounting shaft, said limit switch being wired in series in the power supply to said electrical motor, and actuating means connected to said limit switch means and engageable with said collar adapted to actuate said limit switch when said actuating means is engaged with said collar.

8. The device as defined in claim 4 further comprising manual means mounted on said framework and operatively connected to said second mounting shaft adapted, when actuated, to move said mounting shaft axiailly against the force of said biasing means.

No references cited.