US1387636A - Easy-start driving and reversing mechanism - Google Patents

Description

G. I. ALDEN.

EASY START DRIVING AND REVERSING MECHANISM.

APPLICATION FILED MAR-22.1918.

Patented Aug. 16, 1921.

2 SHEE|S-SHEET I.

GEORGE I. ALDEN G. l. ALDEN.

EASY START DRIVING AND REVERSING MECHANISM.

APPLICATION FILED MAR.22. I918.

' Patented Aug. 16, 1921.

2 SHEE [SSHEET 2- WWW" 1 W UNITED STATES PATENT OFFICE.

GEORGE I. ALDEN, OF WORCESTER, MASSACHUSETTS, ASSIGNOR TO NORTON COM- PANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

EASY-START DRIVING AND REVERSING MECHANISM.

Specification of Letters Patent.

Patented Aug. 16, 1921.

Application filed March 22, 1918. Serial No. 224,073.

To all whom it may concern:

Be it known that I, GEORGE I. ALDEN, a citizen of the United States of'America, residing at Worcester, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Easy-Start Driving'and Reversing Mechanisms, of which the following is a full, clear, and exact specification.

My invention relates to a new and useful mechanical motion embodied in a driving mechanism, and more particularly to a device for starting a load from rest to full speed at a gradually increasing rate and thereafter moving the load at full speed and for reversing and starting the load similarly in the opposite direction. In various types of machinery comprising massive parts which have to be started and stopped at frequent intervals, the speed of the machine is often limited according to the degree of permissible shock which the movable members can stand.

As shown by the'patent to C. H. Norton, No. 1,191,987 of July 25. 1916, a driving mechanism has been devised for starting the table of a grinding machine gradually, which involves a worm adapted to be moved axially like .a rack bar at a gradually increasing rate until the driven worm gear has attained its normal velocity, after which the worm is rotated to continue driving the gear. In such a construction, the worm is stationary during the starting operation and must itself be started abruptly into rotative motion after the table has reached its full speed.

It is accordingly an object of my invention to provide a driving and reversing mechanism embodying a new mechanical movement for reciprocating a machine tool body, such as the table of a grinding machine, without'material shock, and particularly to bring such a body positively but gradually to its normal driving rate by starting a driving member initially into rotation and then giving it a secondary motion adapted to transmit an increasing thrust upon the driven body until the normal speed has been attained.

lVith this and other objects in View, as will appear from the following, disclosure, my invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

In the drawings in which like reference numerals indicate like parts:

Figure 1 is a partial vertical section of a starting and reversing mechanism capable of use in a grinding machine;

Fig. 2 is a. detail view partially in perspective of the cam and the worm driving mechanism;

Fig. 3 is a section through the clutch on the line 33 of Fig. 1;

Fig. 4 is a development of the cam;

Fig. 5 is a section on the line 55 of Fig. 1, showing the cam member and roller engaging therewith;

Fig. 6 is a section on the line 6-6 of Fig. 1, showing means for causing the driving member and the cam member to rotate periodically together;

Fig. 7 is a partial detail section of the cam driver and bearing, showing a slight modification of the device; and

' Fig. 8 is a detail plan view of the brake mechanism shown in Fig. 7.

In the practice of my invention I provide a mechanism for starting a machine from rest to full speed at a gradually increasing rate involving a continuously rotated driving worm, which, while rotating, is caused or permitted, as by means of a cam controlled driving member. to slide axially on its supporting shaft under the reacting force of the driven worm gear, at a rate gradually retarded to zero from that equal to the normal advance of the worm threads, whereby the worm wheel is gradually brought to full speed from its initial state of rest and thereafter rotated uniformly.

As a specific embodiment of my invention I have illustrated in the d :awings a mechanism adapted to accomplish this purpose, comprising a power driven shaft 1, a reversing clutch 2, preferably embodying provisions for permitting a period of rest upon each reverse, a driven shaft 3 suitably supported in bearings 4 and 5. herein diagrammatically shown, a rotatable Worm member 6, having worm threads of any suitable pitch, slidably mounted on the shaft 3 and operatively engaging a worm gear 7 on the shaft 8 adapted to reciprocate the table of a grinding machine. The Worm 6 is rotated by the shaft 3 in the present embodiment by means of an arm keyed to the shaft, and having a face parallel with the worm axis slidably engaging aportion of the worm member.

This arm may take the form of a slotted driving member 9, comprising a hollow cylindrical body portion 10 an end 11 and a tubular extension 12. The portion 10 is concentrically spaced from the extended cylindrical portion 13 of the worm member 6, while the end 11 engages a shoulder 14 on the reduced end 15 of shaft 3. The tubular extension 12 is axially alined with the body portion 13 and rotatively mounted upon the reduced end-of the shaft, to which the member 12 is loosely fastened, to permit of partial relative rotation, by means of a key 16 on the driver 9 fitting in a wide slot 17 on the shaft 3. The worm 6 is driven at a constant rate by the member 9, keyed to the shaft 3 as described, through a pin 20 fixed on the worm cylinder 13 engaging the walls of a slot 21 formed in the cylinder 10 parallel with its axis, this slot being long enough to permit the full intended sliding movement of the worm 6 on the shaft 3.

In order that the worm may be initially moved at a gradually decreasing rate, I provide a cam mechanism, comprising in its preferred form a cam member 22 held sta-' tionary by suitable means during the starting operation and revolving with the worm while the latter is driving at its normal full rate. The worm member 6, for this purpose, carries a cam rider comprising a roller 23 coacting with an obliquely disposed cam surface, such as the slot 24, on the member 22, whereby the rider 23 revolving about the worm axis, travels up the cam and causes the worm to slide axially at a predetermined ratedepending upon the configuration of the cam surface.

In the specific device illustrated, the cam member 22 is of cylindrical shape concentrically located around the driver 9 and provided with a reduced bearing member 25 surrounding the part 12 and rotatable thereon. The extended portion 13 of the worm member 6 has thereon a projection 26, preferably opposite to the pin 20, which carries the roller 23 mounted on a post 27 fixed in the worm member 13 by means of pin 28. The driver 10 is provided with a slot 29 to permit the longitudinal movement of the post and its wheres the worm slides. The cam surface 24 adapted to be engaged by the roller 23, comprises in the present embodiment an obliquely disposed cam slot 24 cut in the outer cam member 22, the opposite walls 30 and 31 of this slot being respectively engaged by the roller 23, on its forward and return trips, wherebyif the cam member 22 is held stationary and the shaft 3 and worm 6 are rotated, the roller is forced to move along one or the other well of the slot and thereby move the worm first one way and then the other on the shaft.

Referring to Fig. 4, which shows a development of a preferred form of cam, the first portion of the cam path is helical or of such shape that at the beginning 32 of travel of the cam roller along surface 30 the longitudinal backward movement of the constantly rotating worm is the same as the normal forward advance of the worm through the Worm wheel teeth, thus holding the worm gear stationary. If this initial part of the curve were continued as represented by the dotted line 33, the worm would slide backward at a uniform rate without moving the worm gear. Also, the far end 34 of the cam path, at the point where the worm has reached its limit of longitudinal motion, is in a plane at right angles to the axis of the shaft and so produces no sliding movement of the worm, whereby the latter operates at its normal velocity as if fixed to the shaft. The curve of the cam slot between the starting and stopping positions 32 and 34 is preferably designed so that the starting of the roller is very gradual and approaches the maximum velocity by gradual steps. While this curve must be designed to correspond with the type of machineto which the device is applied, the theoretically ideal form for the purpose described is that of a gravity curve.

I preferably make the cam slot at its two ends substantially as wide as the diameter of the cam roller 23 so that the roller is in working contact with the curves on opposite sides of the slot. The slot may be lengthened beyond the point where the line is perpendicular to the driving shaft axis, so that the roller may travel beyond the position where it first hits this theoretical stopping place, .or stop a little short of the end of the slot and not bump thereagainst.

The reaction of the worm wheel against the worm gives an end thrust in a direction depending upon the rotation direction of the shaft 3. I may utilize this reacting force of the driven load to hold the cam member 22 stationary during the starting operation but permit movement after the mechanism has reached its normal maximum speed. To this end, I provide for a slight degree of play, permitting longitudinal movement of the shaft 3. Fixed to the Loose friction washers 46 and 47 are located respectively between rings 40 and 42 and r ngs 41 and 43 to assist in taking up frictional wear. It is, therefore, seen that when the shaft 3 is rotated in the direction shown in Fig. 1 by the arrow, the end thrust is transmitted in the direction indicated through the shoulder 14 on the shaft 3, the end piece 11 of the cylinder 10 and the end walls of the cam member 22 to the friction member 42 causing the latter and the rings 40 and 46 to be forced into close frictional contact, thereby retarding or preventing rotation of cam member 22. Due to the fact that the pitch of the cam path in the member 22 is so nearly perpendicular to the axis of the shaft as hereinafter explained, there is little tendency for the outer cam member to be turned by means of the roller engaging the cam. Hence provision need be made for but light frictional engagement between the rings to effectively brake the cam member 22 and hold it from rotation during the traverse of the roller 23 throughout the length of the cam path.

Since this mechanism may be utilized for moving heavy bodies, such as a grinding table, it is desirable in some instances to allow for continuation of rotation of the shaft 3, either under its own momentum or where the pitch of the worm 6 is such as to permit the worm wheel to drive'it in its original direction for a short time after the clutch has been thrown to stop and to reverse the mechanism. For this purpose, I may utilize the construction shown in Figs. 1 and 3, involving a key or lug 50 on the shaft 3 rotatable relative to the clutch member 51 which is mounted on rings 52 sliding on shaft 3. This key 50 is adapted to travel within an enlarged key slot and engage first one shoulder and then the other of the projecting lug 53 on the inner periphery of the sliding clutch member 51, in reverse operations of the shaft 3. The clutch construction is otherwise of the usual type, comprising. as shown, bevel gear wheels 54 and 55, the former keyed to the shaft 1 and the latter rotatably mounted concentrically about the shaft 3, these bevel gears 54 and meshing with another bevel gear 56 similarly mounted adjacent thereto. Clutch teeth 57 are provided on the inner portion of the member 58 connected with the bevel gear 54. Clutch teeth 59 are similarly proidded on the member 60 concentrically arranged within the bevel gear 55 and rotatably mounted on the shaft 3, and teeth 61 and 62 are positioned on the respective ends of the sliding clutch member 51 -to engage the clutch teeth 57 and 59 respectively, depend ing upon the position of the clutch member. Suitable mechanism is, of course, provided for moving this clutch member, but is not here shown.

It will accordingly be seen that when the clutch is thrown to move teeth 62 from the position illustrated into engagement with teeth 59, power is transmitted through the bevel gears 54, 56 and 55 into the sliding clutch member 51 thence to the shaft 3 to rotate it in the opposite direction. Before this rotation can take place in the opposite direction, however, the lug or tooth 53 on the clutch member 51 must travel around until it engages the opposite side of the tooth 50 on the shaft 3, this motion occurring during the necessary interval of time allowed for the whole mechanism, comprising shaft 3, the worm and drive and the machine being operated, to come to rest.

When the clutch is thrown to reverse the mechanism, no power is at first transmitted through shaft 3 to the worm wheel 7 and if the shaft 8 continues to rotate it will now serve as a driving member tending to drive the worm 6. At the same time the thrust in the left-hand direction upon the bearing surface 40 is relieved and the cam member 22 is free to rotate with the worm 6 until the whole mechanism comes'to rest, it being noted that due to this continued rotation due to the driving action of the shaft 8 on the worm wheel 6, the tooth 50 advances in an opposite direction to meet the tooth 53. This interval of time can, of course, be properly adjusted by making the teeth 50 and 53 of the proper widths and otherwise changing the speed and relative sizes of the parts of the mechanism so as to allow suflicient time for the mechanism to stop under its own frictional resistance before the clutch operates in the opposite direction.

I find it desirable to provide a construction insuring that the cam member 22 rotates with the worm 6 and that the roller 23 remains in a correct position for another starting operation and does not advance along the cam path during the interval when the parts are coming to rest, as otherwise the starting portion of the cam would be unused and a shock caused when the worm is started in the opposite direction. For this purpose, I utilize a construction. such as illustrated in Fig. 6 for temporarily fastening the cam member 22 to the drive shaft while the rotating parts are coming to rest.

As illustrated in Figs. 1 and 6, this device may comprise a pin on the reduced portion 15 of the shaft adapted to engage springs 71 and 72 disposed on opposite sldes of a slot 7 3 in the elongated portion 12 of the driving member 9, this slot being wider than the diameter of the pin 70. The key slot 17 in the shaft 15 is somewhat wider than the key 16 in order to allow the necessarv freedom of motion. Disposed within a groove 76 concentrically formed in the cam member 22 are locking grooves 77 and 7 8, the outer edges of which are approached by the motion, if the pin 70 has been holding the spring 71 in contact with the groove 78 by engagement with the projection 80, the pin will retain the parts in this relationship while they are being rotated under the driving action of the shaft 8 and worm gear 7, as permitted by the lost motion in the clutch. When lugs 50 and 53 have come around into engagement, then shaft 3 begins to turn in the opposite direction and, due to the slight play in the key slot 17 for the key 16, the pin travels away from the projection 80, unlocking this spring from the slot 78, and engages the shoulder 79, on the other spring, as shown in Fig. 6. After the key 16 has engaged the wall of the key slot 17, the shaft 3 and the driver 9 then rotate together, without carrying the outer member 22 with them, until the spring 71 has reached the slot 77, whereupon the parts are again forced to travel together. This motion of part 71 around the groove 77 occurs during the same interval as that allotted to the cam roller 23 to ride along the cam path and permit the worm. 6 to retreat under the reactive pressure of the worm gear 7. The operation is similar for traversing the table in the opposite direction.

While the friction disks 40, 41, 42 and 43 are ordinarily adequate for the purpose of holding the cam member 22 stationary during the travel of the roller 23 along the cam path, I may incorporate in the device any suitable type of brake mechanism to hold the cam member 22 stationary. I have illustrated in Fig. 7 a construction involving a brake mechanism which does not utilize the friction disks although, of course, the two may be used together. In the illustrated form, I employ ball bearings for tak-- ing up the end thrust, their construction being of any desired design. For example, as shown, the cam member 22 has two reduced portions 81 and 82, the first concentric with the reduced portion of the driver 9 and the second concentric with and' engaging a reduced portion on the shaft 3. Mounted on the part 82 is a ball thrust bearing of any well known form, such as, for example, rings 83 and 84 concentric about ring 85 and carrying balls 86 therebetween, the whole being mounted in a suitable rim 87 held in the casing 88 by the shoulders 89 and 90 which are adapted to receive the thrust through the ball bearing.

In order to furnish a brake for the outer member 22, I provide any well known construction, such as that illustrated in Fig. 8, which involves two semicircular brake members 91 and 92 hinged together on a pin 93 and adapted to be drawn together by a clamping bolt 9 1 and nuts 95 coacting with the jaws 96 and 97 on the respective brake members. The pin 93 is fixed in the support 5 to prevent rotation of the brake.

The operation of this device is apparent from the above disclosure. If the worm 6 is at the extreme right-hand end of its travel as shown in Fig. 2, and the mechanism is at the beginning of rotation of shaft 3, the cam roller 23 travels along the left-hand cam face 30 of Fig. 2 and the Worm travels to the left. When the roller has reached the horizontal portion of the curve, the sliding motion of the worm has stopped and the worm gear is being driven ,at full speed. During the interval while the worm is sliding, the pin 70 and spring 71 have been traveling around from groove 77 to groove 78 and the cam member 22 is finally brought into rotation with the worm. Upon reversing the clutch, the rotating parts, including worm, gear and cam member, rotate under their own momentum and come gradually to rest while the lugs -50 and 53 in the clutch are traveling to meet each other, after which the cycle is repeated.

By my invention, I have provided a device for gradually starting a heavy body into motion, which is simple in its construction and positive in operation and is easily manufactured and assembled and which permits a given grinding operation to be carried on at more than double the rate heretofore considered the maximum, whereby production is increased, costs of operating decreased and time saved to a material extent.

Having thus described my invention, what I claim and desire to secure, by Letters Patent is 1. A mechanical movement for reciprocat- ,ing a massive body, comprising a driven member adapted to be connected with the body, a screw threaded driving member operatively engaging the driven member and means for rotating said threaded, member in opposite directions for variable periods and, while it is rotating, initially causing a relative secondary motion between it and the driven member to accelerate the reciprocating body gradually and positively to a predetermined normal rate and thereafter permit said rate to be maintained until the direction of traverse is reversed.

2. A machine having a reciprocating member and adriving and reversing mechanism therefor, comprising a shaft rotatable in opposite directions, a longitudinally movable driving worm thereon, a worm gear driven by the worm and driving connections between said shaft and worm effective to rotate said worm continuously between reversals and move it longitudinally during rotation to start the worm gear at a gradually increasing rate and thereafter drive it at a normal rate for an indeterminate period.

3. A machine having a reciprocating member and a driving and reversing mechanism therefor, comprising an axially movable, rotatable worm, a worm gear imparting a resisting force to the worm, driving means to rotate the worm in opposite directions and means for moving the rotating worm axially at a predetermined decreasing rate under the reacting pressure of the gear to rotate the latter at a rate increasing to a normal driving velocity and thereafter preventing axial movement of the worm for an indeterminate time.

4. Amachine having a reciprocating member and a driving and reversing mechanism therefor, comprising a rotatable driving worm, a worm gear operatively connected with the load and driven by the worm. means to start the worm gear gradually and means whereby the load may come gradully to rest under its own momentum without material shock when the mechanism is reversed.

5. A machine having a reciprocating member constituting the load and a driving mechanism therefor, comprising a worm gear arranged to move said member, means including a longitudinally movable, rotatable driving worm to start the load graduall and means whereby the load may come gra ually to rest under its own momentum without material shock.

6. In a driving mechanism, a rotatable, longitudinally movable worm, a worm gear driven thereby, means for giving a gradually decreasing, longitudinal movement to the rotating worm under the reacting pressure of the gear and thereby gradually accelerating the gear to a normal rate, a clutch mechanism for starting and driving said worm at a uniform rate and means permitting the gear to come to rest gradually after the clutch connection has been released.

7 A machine having a reciprocating member and a driving mechanism comprising a shaft, a longitudinally movable, rotatable worm member on the shaft, a worm gear driven by and exerting a reacting pressure against the worm, uniformly rotated driving means slidably engaging the worm member to rotate the same and cam mechanism adapted to control the sliding of the worm and permit a gradual change in rotative movement of the worm gear and to prevent the worm from slidin during an indeterminate period of uni orm rotation of the worm gear.

8. A machine comprising a reciprocating part and a driving and reversing mechanism therefor, comprising a shaft rotatable in opposite directions, a rotatable worm member slidably mounted. thereon, a worm gear driven by the worm, driving means rotated by said shaft and slidably connected with the worm member to rotate it at a uniform rate between reversals and cam mechanism operatively associated with said worm member and adapted to control its sliding movement, under the reacting pressure of the worm gear, and cause the speed of the latter, starting from rest, to be gradually brought to a maximum and thereafter maintained at a uniform rate for an indeterminate period.

9. A machine having a reciprocating table and a driving mechanism therefor, comprising a rotatable, longitudinally movable worm, a worm gear driven thereby and means comprising a cam member, normally stationary during the starting of the table. and a driver for simultaneously rotating the worm and moving it longitudinally relative to the worm gear to start the table gradually and thereafter drive it at normal speed.

10. In a driving mechanism, a driving shaft, a rotatable worm axially slidable thereon. a worm gear driven by the worm, a driver operatively connected to said shaft and longitudinally slidably engaging said worm to rotate the latter at a uniform rate. a cam device comprising a member, normally stationary during the starting of the mechanism, having an obliquely disposed cam path thereon and a rider fixed to said worm and engaging said cam path so that rotation of the shaft permits a definite, predetermined axial motion of the worm on its shaft relative to the gear to start the load gradually and thereafter drive it at a normal rate.

11. In a driving mechanism, a rotatable shaft, a movable cam controlled member rotated thereby, a cam loosely mounted on the shaft and operatively engaging said member to move the same a predetermined distance and means to hold said cam stationary when the shaft is started to rotate and to permit rotation of the cam with the shaft when the cam and member have reached their relative limits of movement.

12. In a driving mechanism, a shaft, an axially slidable Worm rotatable with said shaft, a cam loosely mounted on the shaft and adapted to move the worm axially a predetermined distance when the shaft starts rotating, frictional means to hold the cam stationary during such axial movement of the worm and permitting rotation of the cam with the worm thereafter and means to hold the cam in proper position for further similar movement of the worm.

13. In a driving mechanism, a rotatable, longitudinally movable shaft, a longitudiually movable worm rotated thereby, a Worm gear meshing therewith, cam mechanism controlling the longitudinal movement of the worm, comprising a cam member loosely 56 axis,

mounted on said shaft. and means whereby the end thrust on the shaft caused by the driven gear may hold the cam member from rotating with the shaft during longitudinal movement of the worm.

14. In a driving mechanism, a movable shaft, an axially movable rotatable worm thereon, a worm gear driven thereby, worm driving means and a cam member adapted to cause a gradually decreasing axial movement of the worm mounted on the shaft, frictional means whereby the end thrust of the shaft holds said cam member stationary during starting of the gear and means causing said cam member to revolve with the shaft when the power has been removed and the mechanism is coming gradually to rest.

15. In a driving mechanism, a longitudinally movable shaft, an axially slidable worm rotatable with the shaft, a worm gear driven thereby, a cam rider on the worm, a cam member loosely mounted against a shoulder on the shaft and adapted to engage said rider to move the worm axially when the shaft starts rotating, a support having a fixed friction surface engageable by a similar surface on said cam member, whereby the end thrust transmitted from the worm gear through the shaft and shoulder to the cam member moves the latter into frictional engagement with the support.

16. In a driving mechanism, a driving shaft, a rotatable worm axially slidable thereon, a worm gear meshing with the worm, a driving arm revolved by the shaft and having a face parallel with the axis of the Worm, a pin on the worm engaging said face whereby the worm may be rotated, a cam member having an 'obliquely disposed cam path thereon a rider on the worm adapted to travel along the cam path and means to hold the cam member stationary, whereby the worm may move axially on the shaft while being rotated.

17. In a driving mechanism, a shaft, a worm member loosely mounted on the shaft and having two posts projecting therefrom, a driving member keyed to the shaft and provided with an arm parallel with the shaft said arm slidably engaging one of the posts to rotate the Worm, a cam member loosely mounted on the shaft and having an obliquely disposed cam wall engaged by the other post, means to hold said cam member stationary when the shaft is started to rotate, whereby the rotating worm is moved longitudinally under the guiding action of said cam wall, and means for rotating the cam member with the shaft when a predetermined longitudinal movement of the Worm has been attained.

18. In a driving mechanism, an axially movable driving shaft, a rotatable Worm member axially slidable thereon and havlng two arms projecting therefrom, a worm gear meshing with the worm, a driver revolved by the shaft and slidably engaging one of said arms, a revoluble cam member carried by the shaft and longitudinally movable therewith, said cam member having a cam path engaged by the other arm and adapted to cause a predetermined gradually decreasing axial movement of the worm and a fixed support having a friction surface engageable by a friction surface on the cam member, whereby the end thrust communicated through the shaft to the cam member causes the latter to remain stationary during ac celerationlof the worm gear by axial movement of the Worm.

19. In a driving mechanism, a rotatable. longitudinally movable worm member, a

worm gear driven thereby, a shaft for rotating the worm at a uniform rate, a cam member mounted on the shaft in engagement with said worm member and adapted to cause the worm to move longitudinally at a decreasing rate and start the worm gear gradually, means for holding the cam mem-' ber stationary during such starting operation and permitting the worm to come gradually to rest under its own momentum when thepower is removed and means for rotating the cam member with the worm after uniform speed has been given to the worm gear and when the worm is rotating freely 1n coming to rest.

Signed at \Vorcester, 7 day of March, 1918.

GEORGE I. ALDEN.

Massachusetts, this

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