US2139887A

US2139887A - Grinding device

Info

Publication number: US2139887A
Application number: US128388A
Authority: US
Inventors: Allen I Dunn
Original assignee: Cedar Rapids Engineering Co
Current assignee: IDEAL HORIZONS Inc; Cedar Rapids Engineering Co
Priority date: 1937-03-01
Filing date: 1937-03-01
Publication date: 1938-12-13
Anticipated expiration: 1955-12-13

Description

, Dec. 13, 1938. v A. I. DUNN 2,139,887

' GRINDING DEVICE Filed March 1, 1937 2 Sheets-Sheet 1 INVENTOR.

- ALLEN}. DUN/V ATTORNEY.

Dec. 13, 1938. A. 1. DUNN GRINDING DEVICE 2 vSheets-Sheet 2 Fild March 1, 1937 INVENTOR.

ALLf/V DUN/V BY z W ATTORNEY.

Patented Dec. 13, 1938 UNITE SAFE mass? PATENT OFFlCE Cedar Rapids Engineering Company,

Cedar Rapids, Iowa, a corporation of Iowa Application March 1, 1937, Serial No. 128,388

14 Claims.

My invention relates to valve seat grinding devices and has particular relation to a means for damping vibrations or undesirable oscillatory movements of such valve seat grinding devices. In the art of grinding valve seats it has been found that the guide means originally afforded when the motor was first constructed are not available when refacing of the valve seats becomes necessary. The valve stem guide becomes worn, lop-sided or off the original center line or becomes Warped and the valve seats themselves are subject to warpage. The block itself may, in relieving internal stresses or seasoning as it is called, change the position of the valve seats relative to the valve stem guides or cause the valve seats to assume a new plane or to be warped out of round.

In re-establishing the relative positions of the valve stem guide and valve seat which is neces- 20 sary to secure proper alignment and closing of the valve, it is the usual practice to grind a new seat in the block, the center line of which is established through an approximation of the center line of the valve guide. This is accomplished, in a preferred method of valve seat grinding, by the use of an arbor which fits into the valve stem guide and determines the center on which the new valve seat should be located. In other words, warpage or misalignment of the cylinder block through seasoning destroys the original alignment and the accepted technique in regrinding is to grind the new seat concentric with the center line of the guide.

In facing valve seats it is the usual practice to employ grinding wheels, since many of the valve seats are of hardened steel which cannot be cut by the usual cutting tools. The grinding of these seats is accomplished through the use of high speed grinding devices and the use of high speed wheels is one of the secrets of securing good valve seats by this grinding method. Speeds of 10,000 R. P. M. are ordinarily used. These speeds are so great that a relatively long period of time may be required for the grinding motor to come to a stop.

It is quite apparent that with the high speed devices of this character any minute dynamic unbalance results in vibration and undesirable oscillation of the grinding devices. The grinding Wheel is centered and guided by means of an arbor engaged in the valve stem guide and these valve stem guides, in present practice, are of relatively small diameter on the order of of an inch. Thus the arbor is necessarily light and of very small diameter and is of little assistance in overcoming any dynamic unbalance which may be present in the grinding device. The grinding wheel is driven, in some cases, by means of a flexible connection. This connection itself may be a source of dynamic unbalance through slight whipping. The flexible connection is nec cssary in order that valve seats may be ground which are located underneath or in close proximity to the automobile dash or other obstructions above the motor which it is undesirable to remove. Other drives employ universal joints such as hexagonal heads received in hexagonal sockets permitting some tilting of the grinder motor with reference to the grinding wheel. The flexible connection perhaps permits greater tilting of the motor than other'types.

This problem of dynamic unbalance has been a source of considerable difiiculty over a period of years and none of the drives familiar to the art are free from this difficulty. Many expedients have been tried to overcome it. The only way of meeting this difiiculty known previously to my invention has been to use extreme care in machining and fabricating and assembling the valve grinding devices. Obviously, this requires expensive machining operations, expensive checking and inspecting of the device during manufacture, and frequent servicing after the device has been sold.

After considerable experimentation and thought directed toward endeavoring to solve this problem, I came to the conclusion that dynamic unbalance of the grinder head might be compensated or overcome if a stationary stabilizing element or weight could be applied to the revolving part at the upper end of the head where it was unsupported and where the vibra tion seemed to originate and where it was the Worst. I experimented with various schemes for applying this stabilizing element to this revolving part and finally devised a cylindrical member journaled on a suitable bearing portion of the upper end of the grinder head so that the weight itself could be stationary with respect to the grinder head yet would have a sufficiently close fit with the head to immediately dampen or stabilize the upper end of the head and thus prevent the setting up of undesirable vibrations or oscillations of the grinder head.

In applying a stabilizing element in this manner, a problem arises in preventing the stabilizing element from revolving and at the same time preventing the setting up of any side strain or side pressure tending to bend the arbor and thus cause inaccuracy of the seat being ground. The

connection between the motor and grinder must be fully 'flexible yet the yoke members must prevent the stabilizing element from rotating.

It is a general object of my invention to provide, in a valve seat grinding means, means for eliminating undesirable vibrations or oscillations of the grinder head and minimizing the disturbing effects of dynamic unbalance of the rotating parts of the grinder.

Another object of my invention is to provide a simple reliable means for bringing the rotating parts of a grinding means to a stop.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawings and following specifications, wherein is disclosed a single exemplary embodiment of the invention, with the understanding, however, that such changes may be made therein as fall within the scope of the appended claims, without departing from'the spirit of the invention.

In said drawings:

Figure 1 is a View partly in perspective and partly in section of a grinder including the grinding motor and grinder head, to which a stabilizing element and braking mechanism constructed according to my invention have been applied.

Figure 2 is a fragmentary view of portions of the grinder and showing particularly the braking mechanism of the deviceshown in Figure 1.

Figure 3 is a view, partly in perspectively and partly in section, of the grinder head appearing in Figure 1 but in enlarged relation.

Figure 4 is a plan view of the stabilizing ele- 'ment shown in Figures land 3, and

-Figure 5 is a view in perspective of the stabilizing element shown in Figures 1, 3 and 4..

Valve seat grinding'devices of the type here illustrated are usually comprised of three elements, namely, the driving motor indicated generally at I0, the grinder head indicated generally at II, and a flexible connection indicated at I2, for driving the rotating parts of the head from the motor.

The motor is preferably a high speed motor the rotor of which is adapted to rotate at speeds in the neighborhood of 10,000 E. P. M. Current for the motor is furnished through the electrical connection I3 and controlled by the switch 14.

The shaft I6 of the motor I rotates on the bearings I? and the nose of the motor is elongated as indicated at I8 to afford a cylindrical support for the sleeve like motor nose-piece I9. This nose-piece I9 is, of course, stationary with respect to the motor housing being held stationary by means of the set screw 2|. The nose-piece I9 serves also as a guard extending over a cylindri cal socket or coupling member 22 adapted to serve as a connection between the motor shaft l6 and the flexible connection l2. The motor shaft i3 is preferably engaged to the coupling member 22 by means of threads indicated at 23.

The flexible member I2, in this instance, is

a section of rubber-hose. A positive connection between coupling 22 and the hose I2 is assured by means of a shaft 24 having a threaded shoulder portion as indicated at 25 and a cap member 2?. 'The hose I2 is inserted within the cap member 21 and the threaded portion of shaft is threadedly engaged within the inner wall of the hose I 2. The threaded shoulder portion of the shaft is of substantially greater diameter than the inner diameter of the hose, thus the hose is securely engaged by the pressure exerted between the cap 2? and the threaded portion of shaft 24.

The shaft 24 is in turn securely engaged within the socket member 22 by means of set screw 28. The other end of the hose I2 is adapted to be secured in the cylindricalportion 29 of a grinder head cap 30.

Inasmuch as the grinder motors ordinarily used for this purpose rotate at around 10,000 R. P. M. it takes sometime for a motor to come to rest after use, which results in slowing up of the grinding operation. I have accordingly devised a brake mechanism illustrated in Figures 1 and 2 for quickly stopping the rotation of the motor. In practicing my invention I preferably utilize a ring 3| knurled as indicated at 32 and adapted to rotate on the nosepiece I9 and also to move up and down on the nose piece. The knurled member 3| is pinned by means of set screws 33 to a ring 34 loosely received within the nose I9 and which is adapted to move upward to bear against the flanged portion of the socket 22 to provide a brake for stopping the rotation of the motor. The ring 34 is preferably made of material such as ordinarily used in brake linings and the like. Pressure of the ring 34 against the socket 22 is applied by means of the knurled ring through the agency of the helical grooves'36 in the wall of the nose piece l9. The set screws are loosely received in the ring 3I passing through the grooves 36 and are threadedly engaged with the brake ring 34. Obviously, rotation of the knurled member 3I in a clockwise direction, when viewed from below, causes the knurled member 3i and the ring 34 to move upwardly or in a direction toward the motor III to cause the ring 34 to bear against the flange of the socket 222 to thus apply a braking action to the rotor of the motor.-

The nose piece I9 is cut away at the end thereof to provide a pair of opposed ears 3! and 38, the purpose of which is to prevent a rotation of the stabilizing element 39, as will be hereinafter more particularly explained. The

ears

31 and 38 are curved at the corners on one side as indicated at 4| to permit tilting of the motor II! with reference to he grinding head I l.

The grinder head II includes an outer grinder head shell 42 threaded on to the cap 30. The end of the shell opposite to the motor is closed by means of a shell cap 43 and the shell cap 43 is provided with a cylindrical portion of smaller diameter illustrated at 44 adapted to receive and be engaged within the grinder wheel 46. The grinder head cap 30 and the shell cap 43 act as clamping means for clamping rotating races 41 and 48 in place within the shell. The member 49 acts as a spacing member for holding the races 41 and 48 in proper spaced relationship, and the ball bearings serve as supporting members and bearings for the

stationary races

50 and 52. These stationary races are clamped in place on an inner hollow shaft member 55 by means of an inner shell cap 53, a spacer member 54 and the shoulder 60. The outer shell and the grinder wheel 46 may thus rotate on the bearings 5| and the hollow shaft member 55 may remain stationary. The inner shaft member 55 is adapted to receive an arbor therein indicated at 56. The lower extremity of the arbor 56 is, of course, received within the valve stem guide in the grinding operation and thus the arbor 56 will act as a guide for the grinder Wheel 46. The flexible connector i2 is locked in place within the member 29 by means of a threaded plug member indicated at 5T.

It may be seen by inspection of the drawings of grinder head cap 3%.

stabilizing element provided with a roughly .U -shaped Lip-struck portion indicated at 59 which that the upper portion of the grinder head II is practically unsupported particularly as the the head i i may rotate within the stabilizing element 39 and to assist in eliminating any friction I may provide an anti-friction bearing such as the sleeve 53 which is disposed between the stabilizing element 39 and the cylindrical portion 29 The main portion of the has two opposed faces 6! and 52 adapted to be loosely received in the ears 3? and .38. The upstruck portion 59 is cut away as indicated at 63 to facilitate use of the grinder with the motor at an angle to the grinder head as for instance grinding valves which are below or in close proximity to the dash.

The purpose of the co-acting ears on the motor nose piece and the stabilizing element is, of course, to prevent rotation of the stabilizing element. The inertia of the stabilizing element has been found to be such as to eliminate vibratory or oscillatory movements and any undesirable periodical movements of the grinder head which would tend to interfere with the grinding of a perfect seat.

It is apparent that modifications of my invention may be made by those skilled in the art, but such modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. In a device for grinding valve seats including a motor member, a grinder head and a flexible drive member for connecting the motor and the grinder head, a means for forming a connection between the flexible drive member and the motor member comprising a hollow coupling member, a casing enclosing the coupling member, the casing being formed with two obliquely extending slots in the periphery thereof, a knurled ring slidably engaged in the casing, a braking member within the casing adjacent the coupling member and means for loosely connecting the knurled ring and the braking member through the aforementioned slots, whereby rotation of the knurled ring will cause the braking member to engage the coupling member.

2. In a grinding device including a motor member, a grinder head and a flexible drive member, a means for forming a connection between the flexible drive member and the motor member comprising a hollow coupling member, means for applying a braking action to the rotative members including a braking member adapted to bear against the coupling member, a casing securely engaged to the motor member for retaining the braking member, the casing having two extending bars formed at one portion thereof and a stabilizing member journaled on the grinder head comprising a cylindrical portion and an upstruck U-shaped portion adapted for interfitting connection with the ears of the casing whereby the stabilizing member is restrained from rotating.

3. In a grinding device including a motor member, a rotatable grinder head and a rotating flexible drive connection, a means for preventing undesirable oscillation of the grinder head comprising .a .cylindrical weight member having an upstruck U-shaped portion and journaled on the grinder head, "a coupling means for engaging the flexible drivewith the motor, a means for applyiing braking action to the rotating member and a casing formed with extending ears and engaged to the motor for retaining the braking means, the extending ears of the casing being adapted to .loosely receive the U-shaped portion of the cylindrical member whereby rotation of the cylindrical member is prevented.

4. In a grinder, a grinder head having a central portion thereof adapted to fit on an arbor, a motor flexibly connected to the grinder head for rota ing the grinding wheel, means for stabilizing the grinder head comprising a weight mounted to permit rotation of the grinder head with reference to the weight, and means for preventing rotation :of the weight comprising a universal connection between the motor and the weight.

5. In a grinder, a grinder head and a grinding wheel mounted on the grinder head, means for centering the portion of the grinder head carrying the grinding wheel, and means for stabilizing the portion of the head opposite to the grinder wheel comprising a weight mounted on the head to permit rotation thereof with respect to the weight, a motor for driving the grinding head, the motor having a flexible connection with the head, and means for preventing rotation of the weight comprising a universal joint structure.

5. In combination, a grinder head and a grinding wheel on the head, means for centering the grinder head for rotation thereof, the centering means being associated with one end of the grinder head, a motor for driving the grinder head, so connected to the grinder head that the axis of rotation of the motor may be different than the axis of rotation of the grinder head, and means on the grinder head for minimizing undesirable vibration thereof comprising a weight element journalled on the grinding head, and means operatively engaged with the motor and weight element for preventing the weight element from rotating.

2. In a grinder, a grinder head, means for determining the axis of rotation of the grinder head with respect to the work, and other means for minimizing undesirable vibrations and oscillations of the grinder head comprising a weight journalled on the grinder head, means for preventing the weight from rotating with the head, and a means for driving the grinder head flexibly connected thereto whereby vibrations of the motor are not transmitted to the grinder head and vibrations of the grinder head are not transmitted to the motor.

8. In a grinder, a grinder head and means for supporting the grinder head at one portion thereof for rotation, an additional means for damping out undesirable vibrations at portions of the grinder head other than the portion which is centered comprising a weight element mounted for rotation on the grinder head, and means for holding this last named element stationary with regard to the work, such damping element being independent of the drive means for driving the head, and drive means flexibly connected to the grinder head.

9. In a grinder, a grinding head, an arbor for locating the grinder head with respect to the work, power means for driving the grinder head, flexible means connecting the power means with the grinder head, and a stabilizing element for preventing undesirable oscillation and vibrations of the grinder head comprising a weight rotatably mounted on the grinder head, and means for preventing the weight from rotating With the head.

10. In a grinder, a grinding head, an arbor for locating the grinder head with respect to the work, power means for driving the grinder head, flexible means connecting the power means with the grinder head, a stabilizing element for pre-. venting undesirable oscillation and vibrations of the grinder head comprising a weight rotatably mounted on the grinder head, and means for preventing the weight from rotating.

11. In a grinder, a grinding head, an arbor for locating the grinder head with respect to the work, power means for driving the grinder head, and flexible means connecting the power means with the grinder head, a stabilizing element for preventing undesirable oscillation and vibrations of the grinder head comprising a weight rotatably mounted on the grinder head, and means for preventing the weight from rotating comprising a connection between the weight and the frame of the driving means.

12. In a grinder, including a grinder head,

means received in the work and rotatably received.

in the grinder head for centering the grinder head in rotation, and a motor flexibly connected to the grinder head, a weight journaled on the grinder head, the weight having an upstanding ear portion and the motor having a cooperating ear portion adapted to engage the weight member to prevent it from rotating.

13. In'a grinding mechanism including a motor, a grinder head and a flexible drive connecting the 'motor and grinder head, a means for stabilizing the grinder head during operation thereof comprising a yoked member journaled on the grinder head and another yoked member attached to the motor casing and adapted for interfitting connection with the first named yoke member for keeping said member from rotating, and means for centering the grinder head comprising an arbor received in the work and rotatably received in the grinder head. 7

14;. In a grinding machine for grinding valve seats, an arbor received in the valve stem guide, a grinder head having a hollow shaft member received on the projecting portion of the arbor, outer shell rotatably mounted on the hollow shaft, the outer shell having a grinder wheel at the lower end thereof, a motor for driving the outer shell and grinder wheel, a flexible shaft connecting the motor and outer shell, a weight mounted on the outer shell for rotation with respect thereto, and inter-fitting ears between the frame of the motor and the weight for preventing the Weight from rotating with the shell.

ALLEN I. DUNN.