US1927655A - Speed control device for grinding machines - Google Patents

Description

Sept. 19,1933. A G, D N HAL 1,927,655

SPEED CONTROL DEVICE FOR GRINDING MACHINES Filed April 10, 1929 2 Sheets-Sheet 1 I 21 I 0 75 mini; 7/ 69 65 I. 1I::: 7o 7 EE Mill 21 22;

ALBERT G.BEI DEN WITNESSES FRANK E. DF\ OWN Mam P 1933. A. G. BELDEN ET AL SPEED CONTROL DEVICE FOR GRINDING MACHINES Filed April 10, 1929 2 Sheets-Sheet 2 0 w m m n 2 .Wvw r I u m w 3 4 5 s m mmw% m i 3 WITNESSES- M72 -w Ww.%

F W ww 0 R an T5 mm h WG w Patented Sept. 19,1933

UNiiED STATES PATENT om-CE 1 SPEED CONTROL DEV-EOE FOR GRINDING l MAcHiNEs Albert G. Belden and Frank E. Drown, Worcesterji. Mass., assi'gncrs to Norton Company, Worcester, Mass, a corporation of Massachusetts Application April 10, 1929. Serial No.;354,023 f 7 Claims. (01.51-166) 3 This invention relates to grinding machines and more particularly to a speed controlling derice for the grinding Wheel in such a machine.

In various typesofgrinding machines, it is desirable in order to obtain the maximum efficiency from the grinding wheel, that the surface or peripheral "speed of the wheel be substantially constant. Floor stands for tool grinding and snagging have been constructed and arranged so that it is POSSlblB to change the speed of the Wheel from a slow to a faster speed as it wears away. 1 This has usually been accomplished either by shifting a driving belt from one cone of a pulley to another cone to step up the speed of the wheel or by means of a variable speed motor which. is arranged so that the operator may turn a rheostat control to vary the speed as desired.

The modern grinding wheel is a high speed tool and is capable of rapid production, but is of a comparatively brittle structure so that a sudden blow on the operative periphery or side face of the wheel, or a too fast rotation of the wheel, is apt to cause a breakage of the wheel and a consequent injury to the work and possible serious injury to the operator. In most of these previous machines, the operator may as desired adjust the speed to increase the surface speed of the wheel. The operators find by experience that a rapidly rotating wheel gives a faster cutting action and, learning this fact, they speed the wheel up as fast as possible to increase their production. Hence it is advisable to provide such a machine with a safety device which prevents the operator from'running the wheel at a speed greater than is found by experience to be safe; and in certain types of grinding machines, such as fioor stands for snagging rough castings and the like, the speed change mecha nism used to permit speedingup of the wheel as it is reduced in diameter should be controlled by a device which prevents the rotative speed of the wheel from being increased until the wheel has worn away a predetermined amount.

the past, due to the development of the high speed wheel. In the past, the wheel structures have permitted rotation of the wheel at a peripheral speed of five to'six thousand feet per minute which was considered a comparatively safe speed. Today, with the new wheel developments, the modern high speed wheels may be rotated at a peripheral speed of nine thousand feet per minute and upwards, depending on the size and type of wheel. It will be'readily aplustrated in the drawings, in which This feature is more important today than in,

that the speed cannot be advanced until" the wheel has worn away a predetermined amount. It is a further object of this invention to'pro vide a suitable speed control mechanism which prevents the operator from replacing a wornout wheel with a new wheel of larger fdiameter without first resetting the speed controlling,

mechanism. I

It is still anotherobject of this invention to provide a grinding machine with a speed changing mechanism which is normally inoperative due to the presenceof a stop' the position of which is controlled by a contact member movable towards and from the operative face of the Wheel. I

It is a still further object of this invention to provide a grinding machine having two grinding wheels with suitable mechanism for controlling the speed of rotation of the wheels which is arranged so that the larger diameter wheel will control the speed.

Other objects will beapparent from the following disclosure.

One embodiment of this invention has been illike reference numerals indicate like parts:

Fig. 1 is a rear perspective view of a motor driven'fioor-stand' having-parts broken away to show the speed control mechanism and showing the parts in position with a new wheel mounted on the spindle; i

Fig. 2-is a fragmentary perspective view partly in' section on an enlarged scale showing the speed control mechanism moved to the fast speedand the wheel guard removed to its rear- Ward position; I 1 I I Fig. 3 is a front elevation of a motor driven floor stand embodying this invention having .taken approximately on the line 4 4 of Fig.

3 showing. the driving mechanism for the grinding wheel spindle; and

Fig. 5 is across sectional view taken substantially on the line 55 of Fig. 3 showing the adjusting and locking mechanism for the wheel 7 a contact member, such as a tool rest, a spark shield or a wheel guard, which is adjustable towards and from the face of the wheel and limit-.

ed in its movement by engagement with the face thereof. This member is connected to actuate a stop which normally prevents adjustment of a speed control device until the wheel .wears away to a predetermined size, In the preferred construction, lan adujstable wheel i 7 other end of the support 41 is adjustable relative guard controls the movemrnt' of a stop which normally prevents thecperator from shifting, a rheostat control connected'to a variable speed motor or a multi-step pulley directly connected to speed up the rotation of the grinding wheel. As illustrated in the drawings, this machine comprises a base 11 which rotatably supports a grinding wheel spindle 12in bearings 13. The grinding wheels 14 and 15 are mounted on the outer ends of the spindle 12 bymeans of clamp ing flanges 16 which support and engage the wheels 14 and 15 and .are'in turnfitted to a reducedtapered portion 1'7 on the spindle 12. 7 Suitable wheel guards 18, and 19 are provided surrounding the grinding wheels 14 and 15 respectively to serve as protective guards in. case the wheelsbreak or to confine the abrasive and metallic g'ritduring the normal operation of the machine. These guards are preferably adjustablysupported on the base of the machine and are provided with removable covers 20 and- 21 which are supported on the guards 18 and 19 respectively by the hinges 23 and 24 so that it may be swung open when it is desired to changethe grinding wheels. Each of the wheel guards is provided with a spark shield 25 which projects downwardly over the front peripheral face of thegrinding wheel.

The grinding wheel spindle 12 may be driven from any suitable source of power, such as a constant speed motor'30 mounted within the base of the machine. It is desirable in afioor stand construction of this type to provide a suitable speed change mechanism so that the speed of the grinding wheel may be advanced as the wheel wears away and thus maintain a 1 9i screw 37 which is arranged to'engage one of the substantially constant surface n speed of the wheel. This is desirable since the grinding wheel of a given structure grinds more eificiently at a given speed and as the wheel is worn away this speed gradually diminishes and the cutting efliciency 0f the wheel is impaired. A suitable speed change driving mechanism may include a driving pulley 31 mounted on the end of the motor shaft and arranged to drive a The pulley 32 is slidably keyed to the spindle 12 by a key 34 and is arranged so that any, one of the steps 32,35 or 36 may be positionedin alignment with the driving pulley 31 on the motor shaft. .The pulley 32 is provided with a-set slots 38, 89 or 40 in spindle 12 to lock the pulley in adjusted position so that one of thesteps 32, 35 or 36 is aligned with the motor pulley 31. This enables the operator to adjust the speed of rotation of'the grinding wheel by removing the driving belt and sliding the pulley 32 to bring the desired step into alignment with the pulley 31.

With this construction, it is desirable to provide a suitable tensioning device for properly tensioning the driving belt in any of thepositions of the .multi-step pulley 32. In the preferred construction, this may comprise a movable mount for the motor which is arranged so that the motor may be adjusted relative to the spindle to increase or decrease the distance between the axis of the motor and the axis of the grinding wheel spindle. A motor support 41 is pivotally supported on the screws 42 and 43 which are fixed relative to the base. The

to the base so that the motor may be swung to properly tension the driving belts 33. A nut 44 is pivotally supported on screws 45 and 46 on the front end of the support 41 and is engaged by an adjusting screw-47 which is screw threaded into the nut 44 and is rotatably supported and held against endwise movement by,

that the operator by turning the readily accessible screw 47 by means of the head 48 may adjust the position of the motor 30 so'as to increase or decrease the distance'between the axis of the motor shaft and the spindle shaft. The operator may shift the driven' pulley 32 on the spindle 12 to align any desired step-of the pulley with the motor driving pulley 31. and then by manipulation of the screw 47 give the driving belt 33 the proper tension.

To attain the principal objects of, this invention, it is desirable to so construct and arrange the mechanism that the operator cannot increase the speed of the-grinding wheel "until the wheel has worn away to a predetermined size. To accomplish this a suitable contact member movable relative to the grinding wheel may be mounted in the projection 51 of each guard and engages a rack bar 54 which is adjacent the way P It will be read- 52 on the base of the machine. ily apparent from this construction, that the operator may apply a wrench toa head 55 and turn the pinion 53 which is in engagement with the raek 54 to adjust the position of the guards 18 and 19 relative to the grinding wheels 14 and 15. By means of this construction, the operator may readjust the wheel guards/to maintain the spark shields 25 in close proximity to the periphery of the grinding wheel.

It is desirable that the wheel guards 18 and 19 be locked rigidly to thebase of the machine during the normal operation of the same. lower portion of the guards 18 and 19 are pro-' videdwith projections 56 which engage slideways 57 on the base-of the machine. The ways To lock the wheelguards l8 and 19 ri idly relative to the base 11, a suitable mechanism; is

The

provided including eye bolts 58 passing through aghole in the slideways 5'7 and engaging elongated slots 59 in theprojections 56 of the wheel guards 18 and 19. The upper end of the .bolts 58. are screw threaded and are provided with nuts 60 engaging the upper surface of the projections 56. A clamping lever 61 is pivotally connected ,to eachof the eye bolts 58 by studs 62 so that the lever may swing relative to the bolt. A cam surface 63 is formed on the upper end of the levers 61 so that'when the operator swings the lever towards theleft, as viewed in Fig; 5, thecarn engages the under surface of the slideway 57 and draws downwardly on the bolt 58 and locks the wheel guard rigidly in engagement with the base 11.

A mechanism having a stop is provided which is actuated by movement of the wheel guard to prevent adjustment .of, the speed change mechanism until the grinding wheel has worn away to a predetermined size. This mechanism may comprise a shaft 65 supported in a bearing 66 on base 11 and having a projecting arm 67 engaging an elongated slot 68 in the guard 18. The other end of the shaft 65 is provided with a member 69 having a stop lug '70 which is positioned in the path of a shoulder '71 on a yoked member '72 which engages the end faces of the pulley 32. It will be readily apparent from this construction that the operator cannot slide the pulley toward the left, as viewed in Fig; '1, to speed up the wheel if the stop lug "i0 is in the path of the shoulder '71 on the yoked member 72.

When the operator readjusts the guard 18 as the wheel wears away, movement of the guard 18 swings the arm 6'7 and rocks the shaft 65 and the stop lug 70. When this movement has been sufficient to swing the stop lug '70 out of the path of the shoulder 71 on the.yoked mem-' ber '72, the operator may shift the pulley on the spindle 12 and thereby increase the speed 'of-the grinding wheel. This sliding movement of the driving pulley 32 may continue until the stop lug '76 contacts with a second shoulder '73 on the yoked member '72, thus permitting the operator to slide the pulley to position the next step 35 into alignment with the motor driving pulley 31. i

The speed of rotation of the grinding wheel cannot be increased further until the wheel has worn away'still more and the guard 18 hasbeen adjusted relative to the wheel, so that the stop lug '70 is rocked out of the path of the shoulder '73 on theyoked member .72. When the lug '70 has been moved out of the path of the shoulder '73, pulley 32 may be adjusted towards the left so that the step 36 is in alignment with the driving pulley 31 on the motor (Fig. 2). V

Due to unequal wheel wearcaused by use of one wheel more than the other, the diameters of the two wheels may not remain constant. The speed control device should preferably be arranged so that the larger diameter wheel controls the wheel speed so as to prevent excessive speed of the larger diameter wheel. To accomplish this a separate shaft '75 is connected to the Wheel guard 19 and it is arranged to control a separate stop. This shaft '75 is supported in a bearing '76 on the base of the machine and it has a projecting arm '77 engaging an elongated slot '78 in the wheel guard 19. The other end of the shaft '75 passes through an aperture in the stop lug '70 and engages an aperture in the'mem ber 69. It will be readily apparent from this cone structi'on, that bearings 66 and "76-.on the b'ase of the machine serve to support theouter ends of the shafts 65 and while the member 69 the inner end of the shaft 75 and serves' as a. support for the inner, end of each shaftwThe which is fixed to the shaft 65 loosely engages yoked member ,-72 is. provided with-projecting webs.80 ;,and 81 having hubs 82 and 83-provided .with holes, loosely engaging the shaft .75 which serves as a support for the outer end of the yoked member 72. ,The inner end of theyoked 4 member engages the end surfaces of the pulley machine with the pulley. 32 when'permittedby the position of the stop lug. A' second'stop lug is fixed on the shaft '75, so that when the wheel guard 19, is adjusted a swinging movement is imparted to the arm 7'7 and the shaft 75' to 1 rock the stop lug 90 relative to the yoked mem ber '73. It will be readily apparent from this construction, that the operator cannot. shift the pulley 32 longitudinally to bring thesecond step 35 into alignment with the driving pulley 31 until both of the stop lugs '70 and 90 have rocked a sufiicientdistance to .clear the shoulder '71 (Fig. 1). If only thestoplug '70 has been re-v moved a sufficient distance,,then the operator cannot slide the pulley 32 endwise on the shaft a sufficient distance to position the step 35 into alignment with the driving pulley 3'1 due to the stop lug 90 contacting .with the shoulder '71. When each of the grinding wheels has, worn away a suflicient amount and the wheelguards 18 and 19 adjusted-so that the shafts 65 and'75 have rocked asufficient amount to remove the stop lugs '70 and 90 from the pathof the shoul- 'der '71, then the pulley 32 and yoked member '72 may be moved longitudinally of the machinetoward the left, as viewed inFigs. 1 and 2, until the stop lug '70 engages the shoulder '73 thereby limiting and preventing further adjustment of the pulley 32. x J

The machine continues in operation at the second speed with the driving belts 33 engaging the step 35 of the pulley 32f until the grinding wheels have worn away a sufficient distance to permit adjustment of the" wheel guards 18 and 19 to swing the shafts 65 and. '75 asufficient amount to rock the stop lugs '701ahd 90 out of the path of the shoulder '73 on the yoked member '72 and permit a furtherv sliding movement of the pulley 32' and yoked member 72 toward the left, as

viewed in Fig. 1, so that the step 36 of the pulley I 32 is in alignment with the driving pulley 31.

When it is time to remove the worn-out wheel and to replace it with a new wheel, it is necessary for the operator to readjust the position of the wheel guard to permit the insertionof a wheel of larger diameter. The wheel must be moved toward the left as view in Figs. 1, 2 and 5 to permit the operator to insert the new wheel 'on the, grinding wheel spindle. The operator recess92 adjacent the shoulder -71 on the yoked member 72; When the pulley 32 has been readjusted into this position, the operator may then readjust the wheelguards 18and 19 totheir initial position and thenmount the new wheels in 'place on the spindle 12.

, A cover 95 is provided toenclose the grinding Iwheel spindle and speed change mechanisms.

This .cover is attached to thebase by suitable tion as illustrated in 'Fig. 1, then as grinding proceedsthe wheelsare wornaway and the operator atintervals adjusts the position of the tion with the peripheries of the wheels 14 and 15." When'this adjustment has been sufficient to rock-both of the independently movable stop lugs and out of the path of the shoulder 71', the operatormay then open the cover and loosen the set screw '37 in the pulley 32, remove the drive belts 33 and slide the pulley 32 longitudinally toward the right as viewed in Fig. 3 to bring the step 35 into alignment with the pulley 31 and then lock the pulley by tightening set screw 37 in groove 39 onthe spindle. The operator must then readjust the position of the motor to tension the driving belt 33 by manipulation of the adjusting screw 47. The cover 95 may then be closed and grinding resumed. This adjustment repositions the yoked member so that the shoulder 73 is in engagement with the stop lug '70 to'prevent further increase of speed until the grinding wheels have worn away to a predetermined but smaller.

diameter.

Grinding may be continued until the wheel guards have been" adjusted a sufiicient amount to swing the stop lugs 70 and 90 from the path of the shoulder 73 and the operatormay then similarly remove the driving belts from thestep 35, slide the pulley 32 longitudinally to position the step '36 in alignment with .the pulley 3'1 and then tension the belt 33 as previously described. This setting of the speed change mechanism continues until the grinding wheel has worn away and must be replaced by a new wheel." Before a new set of wheels may be placed on the machine, the operator must reset the speed change pulley 32 to its initial position 1 A grinding machine comprising a base, a' spindle rotably mounted thereon, a grinding wheel on said spindle, an adjustable wheel guard surrounding said grinding wheel, a driving m'otor in said base, driving connectionsbetween said motor and spindle including a slidable multi-step pulley on said spindle, a multiple step device movable with the pulley means including afstop which cooperates with one step of said device to normally prevent adjustment of said means including a rock shaft controlled by movement of said wheel guard forlmoving the stop away from the step as the wheel guard is adjusted for wheel wear to permitincreasingthe speed of the grinding wheel when the wheel has worn away tola predetermined size. I V

2. A grinding machine comprising a base, "a spindle rotatably mounted thereon, a grinding wheel on said spindle,'a contact member movable relative to the wheel periphery, a change speed driving means to rotate said spindle including a multi-step'pulley slidably mounted on said spindle, a yoked memberengaging the end faces of said pulley, a stop normally preventing movement of said yoked member and said pulley, and connections between said stop and contact member arranged to move said stop when the wheel guard'is adjusted to compensate for, wheel wear which prevents sliding said yoked member and pulley. 1

3. A grinding machine comprising a base, a spindle rotatably mounted thereon, a' grinding. wheel on said spindle, an adjustable wheel'guard surroundingsaid wheel, a change speed driving tions between said stop and wheel guard arranged to move, said stop when the wheelguard is adjusted to compensate for wheel wear which permits said yoked member to slide the pulley and increase the speedof the grinding wheel.

4. A grinding machine comprising a grinding 1 wheel spindle, a grinding wheel on each end thereof, two independently movable contact members, each being movable towards and from the periphery of a wheel and limited in its 1 movement by contact with the wheel, a speed control device for 'regulatingfthe wheel speed which has a movable control member, separate stop devices located in the path of said control member, andseparate connections between each stop device and an associated contact member so arranged as to prevent operation of the I speed control device to increase the wheel speed until both contact members have been moved through predetermined distances wheel centers;

5. A grinding machine comprising a base, a spindle'rotatably mounted thereon, a grinding wheel on each end thereof, means, for rotating the spindle, a contact member movable toward and from the periphery of each wheel and limited inits movement by contact with the wheel, a speed control device for regulating the wheel speed, including a movable control member, and two separate stops independently movable into or out of the path of the control mefnberto prevent or permit movement thereof, each stop being operatively connected to be moved by one of the contact members and said parts being so arranged that both of the stops must be moved through a predetermined distance before the control device may be moved to increase the speed of the wheel.

6. A grinding machine comprising abase, a spindle 'rotatably mounted thereon, a grinding wheel on each end thereof, a contact member movable towards and from the peripheryof each wheel and limited in, its movement by contowards the 25 V tact with the wheel, a speed control device for c pulley to speed up the grinding wheel, and regulating the wheel speedincluding a movable control member, and two separate pivotally mounted stops engageable with said controlspeed control device including a multi-step pulley slidably keyed to said spindle, a yoked member engaging the ends of said pulley and movable therewith, a stepped surface on said yoked member, and two separate pivotally mounted stops engageable with said stepped surface each being operatively connected to be rocked by movement of one of the guards and so arranged that both of the stops must be" rocked clear of a given step before the pulley may be moved to increase the speed of the wheel. I V V ALBERTYG. BELDEN.

FRANK E. DROWN.

Images