US 2416886 A
Description (OCR text may contain errors)
March 4, 1947. c. c. STEVENS 2,416,836
SPINDLE MOUNTING AND DRIVING UNIT Filed Sept. 24, 1945 2 Sheets-Sheet l INVENTOQ, CLARENCE C. STEVENS,
H/S A TTO QNEK March 4, 1947. c. c. sTEvENS 2,416,886
SPINDLE MOUNTING AND DRIVING UNIT Filed Sept. 24, 1943 2 Sheets-Sheet 2 1 NVEN TO R.; CLARENCE CSTEVENS,
Patented Mar. 4, 1947 SPINDLE lVIOUNTING AND DRIVING UNIT Clarence C. Stevens, Forestville, Conn, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 24, 1943, Serial No. 503,610
This invention relates to a spindle mounting and driving unit, especially for a high speed grinding wheel, and comprises all of the features of novelty herein disclosed.
To obtain the high quality of ground surfaces required by modern precision antifriction bearings, it is important to have a very smooth running grinding spindle which is free from vibration, chatter, whip and other disturbances which tend to become aggravated at the exceedingly high speed at which such spindles should run. Belt pull has been one undesirable factor in some installations and, to avoid this, it has been a practice to mount a grinding spindle on one set of bearings, a driving spindle or motor shaft on another set of bearings and couplethe spindles together. Difiiculties arise in aligning these spindles and in aligning the coupling with the two spindles. There may be out-of-balance conditions in the coupling, in the wheel spindle or in the motor spindle with its rotor and cooling fan assembly. Any lack of uniformity in the air gap between rotor and stator creates electrical disturbances with resultant vibration and lack of uniformity in the power input. A rough running motor will produce rough work even when used with a smooth running wheel spindle and a rough running spindle will not produce good work no matter how smooth the motor runs. Also the bad conditions are aggravated by the interposed coupling and any misalignment in the units. Another disturbing factor which effects the desired smooth running has been temperature rise due to motor heat and to heat developed at the contact areas between the balls and their races in both the wheel spindle unit and in the motor spindle unit. Lubrication is also a problem.
An object of the invention accordingly is to provide a high speed grinding spindle and drive which will avoid the faul s of prior constructions. The coupling is eliminated by the present oneunit construction wherein a single sturdy spindle of increased strength carries both the grinding wheel and the rotor orv driving means. Temperature rise is minimized by improved andmore copious air circulation as afforded by increased space around the stator between the stator supports and by better dissipation of heat from the spindle housing. Electrical disturbances and mechanical vibrations are minimized by slightly yieldable stator supports which are accurately adjustable to insure a uniform air gap between rotor and stator. A factor of importance is the support of the rotor end of the spindle by astabilizing bearing which is supported by a cushion constructed and arranged so that such bearing can take load and be properly lubricated without applying any bending moment to the spindle, thereby preserving alignment of the spindle and avoiding whip and vibration. The mounting of the fan is such as to minimize any tendency to unbalance the spindle while providing more efficient air circulation and cooling of the whole assembly. To these ends and also to improve generally upon devices of the character indicated, the invention consists in the various matters hereinafter described and claimed. In its broader aspects the invention is not necessarily limited to the specific construction selected for illustrative purposes in the accompanying drawings in which Fig. 1 is a plan view.
Fig. 2 is a vertical central section.
Fig. 3 is a left hand end View.
Fig. 4 is a section taken on line Ll--4 of Fig. 3.
Fig. 5 is an enlarged section of an element of Fig. i.
Fig. 6 is an end View of one of the three stator supports.
Fig. '7 is a sectional view enlarged of a portion of Fig. 2.
Fig. 8 is a right hand end view.
Fig. 9 is a right hand end view of an extension casing,
A spindle 2 is intended to carry a grinding wheel or the like at one end and is journalled in three sets of bearings 4, 6 and 8 while being rotated by a motor whose rotor it is clamped to the spindle. The inner race rings of the bearings 4 are clamped against a shoulder on the spindle by a nut 12. The outer race rings are secured by a cap M which is externally polygonal next to a groove, an inverted U-shaped shield l6 being secured to the cap in surrounding, relation to an inturned flange l8 on the nut to exclude foreign matter. The outer race rings of the two sets of ball bearings 4 and 8 fit in an externally tapered quill or bearing housing a spacer 22 and a washer 24 being interposed. Coil springs 26 between the spacer and the washer urge them apart to preload the bearings. A nut 28 clamps the inner race rings of the bearings 6 and has an inturned flange 39 overlying a groove in a cap 32 which is bolted to the housing. A sheet metal shield 34 encloses the cap to insure against leakage of oil and conducts any such oil to a series of drain holes 35 in the cap from which the oil will go to a groove and a drain hole in the main housing 36.
The main casing 35 has a conical recess to in the opposite direction, the bearing housing can be loosened without any necessity for pounding it axially to drive it out. An oiler M at the rear of the main casing directs oil through suitable ports to an annular groove it in the bearing housing 23 from which (Fig. 4) inclined openings or ports is direct the oil to two pairs of wicks 5b which bear at their upper ends against conical surfaces 52 on the spindle. The conical surfaces deliver small quantities of oil to the bearings. Each wick is carried by a slidable sleeve 54 which is urged upwardly by a coil spring 55 which abuts against a screw plug 58 threaded in the lower end of a guide sleeve 6t. Each guide sleeve is threaded in the bearing housing and has radial ports leading to a space around the corresponding wick.
To prevent a possible building up oi air pressure by the rotating surfaces or by expansion and contraction of the air due to heat which might tend to induce leakage, the pressure in the bearing chamber and outside of it is equalized by a breather. This comprises radial holes 62 in the spacer 22 leading to radial holes 6 3 in the bearing housing, the radial ports being connected by a longitudinal port 66 which communicates by radial ports with a pipe 58 having a strainer or filter to exclude dust.
The stator it of the motor has a flanged enclosing shell l2 of circular form. Three sets of equally spaced vibration absorbing and radially adjustable supports locate the stator concentric with the rotor. These supports are located 120 apart within the casing opposite to similarly located pads or external enlargements 13, one support being at the top as indicated. The, supports are radially deep but narrow circumferentially of the housing so that considerable space exists between them for cooling air. Each support comprises a flanged plate i l having a central tongue it entering a key slot in the stator shell to prevent rotation. Each plate it is bonded to resilient cushioning material '53 such as a block of natural rubber which is also bonded to a plate '86 which enters a longitudinal groove 81 in the main housing. A pair of shouldered screws 82 (Fig. 7) are secured at their ends to each plate 39 and are threaded in internally and externally threaded bushings or differential nuts B l which are slotted across the top. The internal threads are of different pitch from the external ones so that a fine and accurate adjustment of the stator can be eilected to insure its concentricity with the rotor and a consequently uniform air gap. After adjustment, solder may be run into the recesses above the screws to maintain the adjustment. The rubber is under compression and yieldably supports the stator radially and circumferentially against electrical and mechanical reactions so that vibration is damped.
At one end of the main casing 35 (see Fig. 7) 'is bolted an extension casing 9t carrying a conduit 95 for the electric Wiring and having an internal seat 92 which is a spherical segment. Another spherical segment is formed by a plate 9d which is accurately centered in a cylindrical recess 95 r 93. An oil feeder I I8 has a flexible i of the casing and held from rotation by dowel pins 96 which are driven into holes of the casing 90. A nut 98 locks the plate st in a position wherein its spherical segment is concentric with the segment 92. Within the spherical segments is contained a moulded cushion l til of rubber or other plastic material having flow characteristics and vibration absorbing qualities similar to those of processed rubber. The cushion is in the form of a parti-spherical ring or sleeve and surrounds a spherical segment between cylindrical'surfaces on a bearing housing IE2. The
cushion is not wholly confined but can flow or bulge outwardly in the annular space between the spherical segments and into the small clearance spaces at its ends. The bearing housing I632 is permitted a very small self-alignin or lateral centering movement without placing any bending moment on the spindle, the compressed cushion being able to flow like a liquid under pressure so that pressure against the bearing housing remains uniform all around it. The stabilizing bearing 8 will thus support radial load without that load having any tendency to bend or displace the spindle laterally from the axis of rotation which is determined by the preloaded bearings 4 and 6. There is no metal to metal cont-act between the bearing housing and its support and vibrations are absorbed. The spherical form of the cushion helps to insure uniform flow. Natural rubber is a suitable material for the cushion Illii and for the cushions is, its flow characteristics being predictable and reliable as distinguished from most synthetic varieties.
The outer race ring of the stabilizing hearing has a sliding fit in its housing to provide for expansion and contraction of the spindle and the inner race ring is clamped by an internally threaded portion on the extended hub Hi4 of a removable fan which is sleeved on a reduced extension of the spindle 2 and acts as a nut. A removable cap 5% is bolted to the housing Hi2 and has a sleeve portion entering the housing and surrounding the fan hub with a clearance, there being a spiral thread on the fan hub to inhibit leakage of oil. The fan has radial blades ltd cut in its flanged end opposite to an opening in an end plate Ill} bolted to the casing 551. A strainer or filter I I2 for the incoming air is placed in the opening. The cooling air then is driven through four openings H3 in the casing 96, then between the widely spaced stator supports as well as through the air gap between rotor and stator and out through a series of longitudinal ports H4 in that part of the main casing which.
encloses the bearings 4 and 6. Additional air to cool the spindle and rotor may be obtained as indicated in Fig. 2 wherein a short tube its projects forwardly from the fan conducts air to a spindle bore iii having radial exit ports beyond the rotor.
The end'plate IIil has a pair of diametrically opposite hollow bosses H5 and i it around which theair travels to the openings H3 in the casing delivery pipe I26 passing loosely through the upper boss H5 into a hole in the cap I06 where it communicates with aligned ports I22 extending longitudinally through the bearing housing H32 into the bearing chamber at one side of the bearing 8. The cap N36 has a notch I24 at the bottom leading to a port I26 from which a drain pipe I 28 extends down with clearance through the lower boss Iit to the outside of the end plate. The drain pipe and passages also form a. breather to equalize pressure in the bearing chamber. The delivery pipe I20 is composed of flexible material such as synthetic rubber in order that no appreciable force or load will be transmitted to the spindle to disturb its alignment. The conduits are uninterrupted so that oil cannot leak and come in contact with the rubber cushion to damage it.
Servicing of the unit and disassembly is convenient while keeping the bearings protected. The tapered quill or bearing housing 20 will come out endwise with the spindle 2, its bearings 4 and 6 and its rotor III, the rear stabilizing bearing 8 remaining in its housing I02 when released from the spindle by removal of the fan which is accessible through the filter opening.
1. In a spindle mounting and driving unit, a supporting casing, a spindle, bearings in the easing to establish the axis of rotation of the spindle, a driving member on the spindle beyond the bearings, a stabilizing bearing on the spindle beyond the driving member, and means mounted in the supporting casing for enabling the stabilizing bearing to give lateral support to the spindle in all directions equally to avoid any tendency to deflect the spindle from its established axis of rotation.
2. In a spindle mounting and driving unit, a supporting casing, a. spindle, bearings in the casing to establish the axis of rotation of the spindle, a. driving member on the spindle beyond the bearings, a stabilizing bearing on the spindle beyond the driving member, and means for enabling the stabilizing bearing to give lateral support to the spindle in all directions without any tendency to deflect the spindle from its established axis of rotation, said means comprising a compressed cushion supporting the bearing and composed of material capable of flow to equalize the pressure all around the bearing and to dampen vibration.
3. In a spindle mounting and driving unit, a supporting casing, a spindle having a driving member in the casing, bearings in the casing beyond one end of the driving member and fixing the axis of rotation of the spindle, a stabilizing bearing on the spindle beyond the other end of the driving member, and a self-centering support mounted in the supporting casing around the stabilizing bearing.
4. In a spindle mounting and driving unit, a supporting casing, a spindle having a driving member in the casing, bearings in the casing beyond one end of the driving member and fixing the axis of rotation of the spindle, a stabilizing bearing on the spindle beyond the other end of the driving member, a hollow rubber cushion of spherical segment form around the stabilizing bearing, and means for holding the cushion under compression.
5. In a spindle mounting and driving unit, a supporting casing, a spindle having a driving member in the casing, bearings in the casing beyond one end of the driving member and fixing the axis of rotation of the spindle, a stabilizing bearing on the spindle beyond the other end of the driving member, a spherical seat in the casing, and a rubber ring of spherical segment form compressed between the seat and the bearing.
6. In a spindle mounting and driving unit, a supporting casing, a spindle having a driving member in the casing, bearings in the casing beyond one end of the driving member and fixing the axis of rotation of the spindle, a stabilizing bearing on the spindle beyond the other end of the driving member, a bearing housing for the stabilizing bearing, a seat in the casing, and a ring of rubber compressed between the seat and the bearing housing.
7. In a spindle mounting and driving unit, a supporting casing, a spindle having a driving member in the casing, bearings in the casing beyond one end of the drivin member and fixing the axis of rotation of the spindle, a stabilizing bearing on the spindle beyond the other end of the driving member, a bearing housing for the stabilizing bearing and having clearance with the spindle for relative shifting with respect to the spindle, a seat in the supporting casing, and a. cushioning ring of flowable material compressed between the seat and the bearing housing to dampen vibration.
CLARENCE C. STEVENS.
Farrand Apr. 6, 1937 Brittain June 24, 1930 OTHER REFERENCES Product Engineering, Sept. 1933, pages 322-326. (Copy in 308-189 Div. 45,)