US2003495A - Grinding machine - Google Patents

Description

June 4, 1935. RITZ, JR

GRINDING MACHINE Filed April 11, 1950 2 Sheets-Sheet 1 INVENTOR. Mfldg,94.

QMZW ATTORNEYS June 4, 1935. E, RlTZ, JR 2,003,495

GRINDING MACHINE 2 Sheets-Sheet 2 Filed April 11, 1950 ATTORNEY-9 Patented June 4, 1935 UNITED STATES PATENT OFFICE GRINDING MACHINE Application April 11, 1930, Serial No. 443,400

15 Claims.

My invention has to do primarily with driving means for grinding machines, and one of its very important applications is to the drives of high speed grinders which involve special problems.

In modern high speed grinding, the feature of importance is a certain peripheral speed of the grinding wheel. If a slower speed is employed, then the grinding is inemcient, whereas if the optimum speed is very much exceeded there is danger of the wheel exploding. Since peripheral speed of a grinding wheel is not alone a function of the speed of rotation of the shaft to which it is attached, but also has to do with the diameter of the grinding wheel itself, and since due to wear )5 the diameters of the grinding wheels are continually changing, it is necessary for satisfactory commercial operation to provide means for varying the speed of wheels in these grinders.

An object of my invention, therefore, is to provide means for controlling and varying the speed in grinding machines. Since for a given wheel diameter the speed should not be increased for safetys Sake beyond a given point, it is another object of my invention to provide in a grinding machine safety means in connection with the speed change means, whereby too great a speed for any given diameter of grinder wheel is prevented. It is thus also my object to prevent a change of speed in grinding machines when the diameter of the grinding wheel is too large to render such speed change safe. Again, because, as hereinabove pointed out, it is necessary to have the grinding wheels at a certain optimum peripheral speed of which the shaft speed and wheel diameter are functions, in order to attain the utmost efiiciency, it is advisable to regulate the shaft speed very closely to the wheel diameter. A further object of my invention therefore is to provide means for regulating the shaft speed very closely in accordance with the wheel diameter. Still another object of my invention is the provision of means to make such speed regulation substantially compulsory on thepart of the operator.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these spec ifications, I accomplish by that certain construction and arrangement of parts of which I shall now describe a preferred embodiment, reference being had to the drawings which form a part hereof.

In the drawings:

Figure l is an elevation of a single drive shaft grinding machine embodying my invention.

Figure 2 is a section therethrough along the lines AA.

Figure 3 is an elevation of a two-shaft grinder equipped with separate drives.

Figure 4 is a section of Figure 3 along the lines 5 BB.

In solving the problems to which my invention is addressed, I have selected as most preferable a type of drive which permits a gradual change of speed as contrasted with a change of speed by stages. My invention is, however, applicable to other types of drives, and is not restricted to gradual change speed mechanism. In a grinding machine, I provide driving means and a change speed'mechanism connecting the driving means and the driven shaft. Grinding wheels are mounted on the shaft, and these grinding wheels have the ordinary movable guards. As the diameter of the grinding wheel decreases with use, it is not only possible but necessary to move the guards back so that the surface of the wheel may be got at adequately. I couple the actuating devices of my change speed mechanism in the preferred embodiment of my invention to means for moving the guards. Thus as theguards are moved back, the speed may be changed; but so long as the diameter of the wheel prevents the movement of the guard, the speed may not be changed, thus eliminating the possibility of the speed of the driven shaft being increased to a dangerous degree, while the wheel itself remains too large to'permit of sucha speed change. Seeondly, however, since for effective grinding the guards must be moved back as the wheel grows smaller, my coupling of the guard moving means and the change speed operating means enforces a speeding up of the machine as the wheel diminishes in size, thus keeping the grinder always operating at maximum efliciency.

Referringnow to Figure 1, I have shown a grinding machine of standard design having 'a frame or housing I upon which a driven shaft 2 is supported in suitable bearings 3. This shaft, in standard grinders, bears a grinding wheel 4 at either end thereof. Guards 5 surround each wheel, and are mounted so that they may be slid horizontally toward the rear of the machine as the wheel size diminishes, thus enabling the work to be brought into proper relationship with the wheel. To this end, in the form of grinderillus- 50 trated, the guards have brackets 6 which are held to the tops of the bearing housings by bolts, and the brackets are slotted where the bolts pass through to permit the horizontal motion desired. Instead of the bolt I a hand-bolt la, such as constant.

shown in Figure 3 or, some other fastening device may be used, since when the position of the guard has been adjusted, it is advisable to tighten the guard-holding brackets to. prevent the unintended movement thereof.

While my invention is not restricted to the particular type of drive which I shall now describe, I have found this type completely satisfactory. The type chosen comprises for a driving member opposed tapered or conical pulley members, the distance between which may be varied. A relatively stiff belt or equivalent member having sidewise inclined bearing surfaces engages between the two conical members. As these members are brought further apart, the belt rides closer to the shaft upon which they are mounted, thus varying the effective diameter of the driving means. Conversely as the conical members are caused to approach, the effective diameter of the driving means becomes larger, because the belt rides further out on the conical surfaces of the driving member. The driven member may also comprise a similar pair of members having conical surfaces, and there may be interconnecting levers whereby the distance between the conical members upon the driving and driven shafts may be conversely varied. When this is done the distance between the axis of the drive and driven shafts remains It is more economical however, and in some respects preferable, to use but one variable diameter drive or driven member, but in this case the distance between the axes of the shafts must be varied. I shall describe a drive of the latter type. I provide, in the casing of my grinder, a base 8 which is dove-tailed, and which has a secondary base 8a also dove-tailed and arranged to slide with reference to the main base 8 in a direction transverse of the axis of the driven shaft. Upon this supplementary base I mount a motor 9 having a driving shaft ID. A pair of opposed conical members H and I2 are mounted on this shaft, the first one fixedly, and the second longitudinally slidable on the shaft by reason of a collar I3 to which it is attached, but nonrotatable with respect to the shaft because the collar is keyed to the shaft, as will be readily understood. The conical member I2 is urged toward the conical member H by a coiled spring M which surrounds the collar and bears against the member l2 at one end, and at the other against an abutment l5 fastened on the end of the shaft. The grinder or driven shaft 2 bears a pulley l6; and a belt member I! of the type described, engages over the pulley I6 and between the conical members H and I2. It will now be clear that as the distance between the axis of shafts 2 and I0 is increased, the driven speed of shaft 2 will be decreased because the effective driving diameter of parts I I and I2 will be decreased. The converse is also true. The frame of the grinder illustrated in the several figures is wide enough at the base to permit a sufficient horizontal movement of the motor. As the distance between shafts 2 and I0 increases, the belt I1, remaining constant, will effect a separation of the driving members H and I2 against the tension of the coiled spring [4, as will be readily understood. To effect this horizontal motion of my motor, I mount a threaded shaft l8 in suitable supports IS on the base 8 so that it is rotatable with reference thereto, but is incapable of longitudinal movement. This threaded shaft passes through a suitable hole in the dove-tailed portion of the supplementary base 811, which hole is threaded to receive it. It will now be clear that a rotation of the shaft l8 will effect a horizontal movement of the motor 9 on its supplementary base along the base 8, and will thus operate to change the speed.

My guards 5 have operating members to effect their movement. These operating members may take a wide variety of forms, two exemplary forms being shown by me. In Figures 1 and 2, lugs 2| on my guards have extensions passing through slots 22 in the frame of the grinder. If the bolts I or other fasteningmembers la are released, it will be seen that the guards may be moved by means of these lugs, and to this end I bore a hole through the end of the lugs and thread it to receive a threaded shaft 23 mounted in the frame I upon suitable bearing supports 24, so that it can rotate, but cannot be moved longitudinally. As the shaft 23 rotates, the guard moves forward or back, depending upon the direction of rotation. I provide a similar structure for each guard, and have indicated the structure on the righthand side of Figure 1 by numerals 23a and 2 la, which designate parts corresponding to parts 2i and 23 on the left part of Figure 1. Upon the threaded shafts 23 and 23a I mount respective sprocket wheels 24 and 24a, and I interconnect these by a chain or other suitable driving means 25 so that the shafts move togetherand in the same direction, and thus the guards must be moved in unison. Both shafts preferably extend through the frame of the grinder and are fitted with handwheels 28 and 25a, by means of either of which both shafts may be operated.

The shaft 23, however, bears another sprocket 21 which is connected by means of a chain or other suitable driving means 28 to a sprocket 29' which is mounted upon a suitable shaft or stud 20' upon the base 8. The sprocket 28 is non-rotatably connected by means of the shaft 30, or otherwise, to a gear 3! which meshes with a gear 32 on the threaded shaft 20.

The interconnection of the several parts will now be clear, and it will be seen that as either of the handwheels 26 or 26a is rotated, both shafts 23 and 23a rotate in the same direction, and the shaft 26 rotates in an opposed direction. Thus as the guards are moved toward the rear in my machine by the operation of shafts 23 and 23a, the motor is moved forwardly through the operation of shaft 29 in the opposite direction, and the speed of the grinder is thus increased. This will be clear from Figure 2, in which it is shown how the effective diameterof the driving means increases as the motor is moved forwardly. The

factor of safety is subserved because while the wheel diameter remains constant, the guards cannot be moved back, and consequently the speed ratio cannot be changed. The factor of efiiciency is subserved because when the wheel diameter has become substantially smaller, so that the peripheral speed of the wheel is no longer great enough for optimum results, then the guards must be moved back in order that the work may be brought up to the wheels; and the operation of I moving the'guards back automatically effects the proper change of speed. It will be understood that the mechanical movements and driving means which I have shown interconnecting the speed change actuating mechanism and the guard moving mechanism may be varied without departing from the spirit of my invention. It will also be clear for any given type of grinding work, wheel size and the like, the ratio of the parts in the motion transmitting mechanism for effecting movement of the guards and change of speed will be proportioned so that the proper speed for the then size of the wheel will be attained at each guard setting.

In the embodiment shown in Figures 1 and 2 th speed cannot be increased imtil both wheels have been worn away to permit setting back of 'righthand guard which is now free has been moved back. This will be apparent when it is considered that the speed may now be changed by a movement of the lefthand guard, and if the righthand guard is entirely free it may happen that the righthand wheel is too big when the change of speed is effected to stand the increased speed. The righthand guard may be interconnected with the lefthand guard so as to block the latters rearward motion until the former shall also have been moved back, by means shown in Figure l of my copending application for Letters Patent No. 409,400, filed Nov. 2,1929, and this may be done without departing from the spirit of my invention.

However, in single shaft grinders, if one wheel wears away very much faster than the other, it is advisable to replace this wheel with another of the proper diameter, because even if the guard on this wheel is moved back without changing the speed of the grinder shaft, the smaller grinding wheel will not be operating at maximum efficiency because its speed will be too low. Consequently, where it is not desired to use large grinding wheels, and where different types of work are done on each wheel of each machine, it is preferable to provide a two-shaft grinder such as is illustrated in Figures 3 and 4, in which independent grinding shafts 2a and 2b are mounted in suitable bearings, each having its own motor 9a or 91) connected to it by a Variable speed drive as has hereinbefore been explained. To save room it may be necessary to ofiset the motors in this type of machine by raising the base of motor 9a upon a sub-base 8b. I have illustrated in the embodiment of Figures 3 and 4 the same general construction excepting that now the moving means for each guard is directly connected to the actuating means for changing the speed of each drive, the drives being separated, and the handwheels 26b and 260 not being interconnected. Because each grinder shaft has its separate prime mover, the speed of each may be directly changed in proportion to the allowable movement of its guard. In this embodiment the guards are similarly mounted, but each has a rack bar 33 extending through a slot 34 in the frame or housing, and meshing with a worm 35 on the otherwise unthreaded shafts 36 and 36a of the handwheels 26b and 26c. The direction of the spiral teeth on the worm 35 may be made such that as the guard moves back the motor 9a moves forward within the sprocket 31, and the shaft 36 is directly connected by means of chain 28 to a sprocket 39 on the threaded shaft that moves the motor supplementary base.

Various modifications may be made in my invention without departing from the spirit thereof.

Having thus described my invention, what I ent, is:

claim as new and desire to secureby Letters Pat- I. In a grinding mechanism or the like, a driven shaft, a motor, a variable speed transmission interconnecting said motor and said-driven shaft, effective upon a variation of the distance between said motor and said shaft, a grinding wheel on said driven shaft, a guard surrounding said grinding wheel, and means simultaneously to move said guard and said motor.

2. In a grinding machine or the like, a driven shaft and a motor, said motor mounted for movement with respect to said shaft, and variable speed transmission mechanism interconnecting said motor and said shaft, a grinding wheel on said shaft, a guard surrounding said grinding wheel, mechanical means for moving said guard, mechanical means for moving said motor, said last two mentioned means mechanically interconnected, and means for operating both simultaneously.

3. In a grinding machine, a housing and driven shaft in said housing, a grinding wheel on said driven shaft, a guard surrounding said grinding wheel and mounted slidably on said housing, a motor in said housing mounted for sliding therein, a variable change speed transmission interconnecting said motor and said shaft, a shaft arranged to move said guard, a shaft arranged to move said motor and a mechanical interconnecthereto, a variable speed transmission interconmeeting said motor and said grind shaft, a shaft in said frame adapted to move said motor, a chain and sprocket connected between said guard movement shaft and said motor movement shaft whereby as said guard is moved back on said grinding wheel, the distance between said motor and said grind shaft will be decreased, and operating means upon one of said shafts.

5. In a grinding machine or the like, a housing, a grind shaft mounted in said housing, a grinding wheel on said shaft, a guard surrounding said grinding wheel and slidably mounted on said housing, said guard bearing a lug extended through a slot in said housing, a threaded shaft in said housing engaging said lug so as to move said guard, a base in said housing and a supplementary base slidably mounted thereon, a motor on said supplementary base, a variable speed transmission mechanism interconnecting said motor and said grind shaft, a threaded shaft mounted on said base and engaging said supplementary base so as to move said motor, and a chain and sprocket connection between said last mentioned shaft and said shaft for moving said guard.

6. In a grinding machine or the like, a driving shaft, a driven shaft, a driven member on said driven shaft, pulleys on the respective shafts, a belt around said pulleys, one of said pulleys having a surface with which said belt may coact at various distances from the pulley axis, means yielding to hold the belt to coact with areas of said surface at the various distances, and means movable for taking up the slack of the belt, limited in its movement by said driven member.

7. In a grinding machine or the like, a driving shaft, a driven shaft, a driven member on said driven shaft, pulleys onthe'respective shafts, a belt around said pulleys, one of said pulleys having a surface with which said belt may coact at various distances from the pulley axis, means yielding to hold the belt to coact with areas of said surface at the various distances, and means movable to vary the distances between said shafts, limited in its movement by said driven member.

8. In a grinding machine or the like, a driving element, a driven element, an operative connection between said elements, means whereby the ratio of speed transmission by said connection is varied by varying the distance between said elements, and means movable for varying said distance, limited in its movement by said driven member.

9. In combination with a grinding wheel, a motor movable toward and away from said wheel, an operative connection from said motor to said wheel, having its ratio of transmission changed according to the distance between said wheel and said motor, and means movable to vary said distance, limited in its movement according to the diameter of said wheel.

10. In a grinder the combination with a grinding wheel spindle and an element overlying the periphery of a grinding wheel on said spindle and adjustable toward and away from said spindle, of a drive shaft, a change speed driving connection between said spindle and shaft necessitating relative bodily movement between said spindle and shaft for changing speed, a support carrying said drive shaft and adjustable for changing the speed of said driving connection, means for locking said support against movement to change to a higher speed and moveable to release the same, and a connection between said adjustable element and said locking means for operating said locking means to permit a change to a higher speed with movement of said adjustable element toward said spindle. Y

11. In a machine of the character described, a grinding wheel, a motor, driving devices between said motor and wheel adapted to be altered to change the speed of the wheel, said motor being bodily movable to and from said wheel to permit alteration of said devices for difierent speeds, and stop means extending from the motor and co-operationg with the periphery of the wheel so as to be regulated by the size of the wheel to control such movement of the motor.

12. In a machine of the character described, an insertable grinding wheel, a motor, driving devices between said motor and wheel adapted to be altered to change the speed of the wheel, and stop means movable with the motor for positively preventing the insertion of a wheel of given diameter until such driving devices have been altered to impart proper peripheral speed of said wheel.

13. In a machine of the character described, an insertable grinding wheel, a motor, driving devices between said motor and wheel adapted to be altered to change the speed of the wheel, said motor being bodily movable to and from the grinding wheel to permit alteration of said devices for different speeds, and means actuated by such movement of the motor to prevent the insertion of a wheel of given diameter until the motor has been moved to permit the alteration of the driving devices such as to impart a proper peripheral speed to said wheel.

14. In combination with a grinding wheel, a motor movable toward and away from said wheel, an operative connection from said motor to said wheel adapted to have its ratio of transmission changed merely by varying the distance between said wheel and said motor, and means movable to vary said distance, limited in its movement according to the diameter of said wheel.

15. In combination with a grinding wheel, a motor movable toward and away from said wheel, an operative connection from said motor to said wheel adapted to have its ratio of transmission changed merely by varying the distance between said wheel and motor, and stop means cooperating with said wheel to limit the movement of the motor.

EMIL RITZ, JR.

Images