US2288824A - Speed change mechanism - Google Patents

Description

July 7, 1942.

E. T. 'MEAKIN SPEED CHANGE MECHANISM Filed March 2, 1940 I23 4 Sheets-Sheet l Imvcntor 506/42 ZNEAAl/V WQM HIS (Ittomeg July 7, 1942. E. T. MEAKIN SPEED CHANGE MECHANISM Filed March 2, 1940 4 Sheets-Sheet 2 3nventor 06792 7. MEA/f/N July 7, 1942. E. T. ME

SPEED CHANGE Filed March 2; 1940 III/4 0 I III/Il/IIIIIJ.

207 w /73 A93 A67 hail AKIN MECHANISM 4 Sheets-Sheet 5 um It INVENTCR. EDGAR TIMEAK/N #176- ATTORNEY.

y 1942. E. T. MEAKIN 2,288,824

SPEED CHANGE MECHANISM Filed March 2 1940 4 Sheets-Sheet 4 v 'mmmll l L INVENTOR.

' EDGAR 7: MEA/r/N HIS ATTORNEY.

Patented July 7, 1942 UNITED STATES PATENT OFFICE tfii'flfifin m flm. Application 2, 1940, Serial iNo. 321,925 3 Claims. (Cl. 'Il-125-5) My invention relates to a speed change mechanism for enabling a change in the rotational speed of a driven member with respect to that of the driving member, and more particularly relates to such a mechanism adapted for enabling control of the feeding of moldable material to an extrusion mill or the like.

In an extrusion mill, moldable material is fed to an extrusion chamber where the same is forced through an extrusion die by the application of pressure thereto, such as by means of rollers or the like.

In as much as the desired rate of feed of material to the die chamber depends upon many factors, such as the size of die openings, the character of the material and the proportions of ingredients entering into such material, and the characteristics desired in the extruded product, it becomes apparent that the rate of feed of material must be capable of fine regulation and control within a substantial range of limits.

It is accordingly an object of my invention to provide an improved feed control for extrusion mills or the like; to provide an improved feed control for the feeding of moldable material to an extrusion mill; to provide an improved speed control which may be of general utility but which is particularly applicable in regulating and controlling the feeding of moldable material to an extrusion mill; to provide a speed control for the feed mechanism of an extrusion mill, which shall impart amintermittent movement to such feed mechanism to provide an improved coupling capable of transforming continuous movement of a driving member into intermittent movement of a driven member; and to provide a feed control for an extrusion mill or the like, which will enable an operator to regulate the rate of feed of moldable material in accordance with the many factors which determine the desirable rate of feed for such machine.

Additional objects of my invention will be pointed out in the following description of the same taken in conjunction with the accompanying drawings wherein- Figure 1 is a vertical sectional view, partly in elevation, of a preferred embodiment of my improved speed control shown in combination with a fragmentary illustration of a hopper and screw feed assembly of an extrusion mill or the like.

Figure 2 is a front sectional view of the speed control adjustment end of the mechanism of Figure 1, taken along the line 2-2 of Figure 1.

Figure 3 is a view, in section, taken along line 3-4 of Figure l.

Figure 4 is a view, in section, taken along the line 4-4 of Figure 1, showing the position of internal components during driving engagement.

Figure 5 is a view similar to that of Figure 4, showing the position of the same components when out of driving engagement.

Figure 6 is a view corresponding to that of Figure 1, but depicting a different embodiment of my invention.

Figure 'l is a front elevational view of the embodiment of Figure 6.

Figure 8 is a view, in section, along line 8-8 of Figure 6.

Figure 9 is a view, in section, along line 9-9 of Figure 6.

Figure 10 is a view, in section, along line 10- of Figure 6.

In its broadest aspects, my invention pertains to a speed change coupling between a driving and driven member. The driving member may be a shaft coupled to a source of power, such as a prime mover, while the driven member may be another shaft coupled to a load which it is desired to drive. To one of these members is connected a ratchet, while to the other member there is connected a pawl or a plurality of pawls which are adapted to engage with the ratchet and effect a driving connection betweenthe driving membet and the driven member.

Cam means is provided to eflect such engagement between the pawl and the ratchet, and the speed change is realized by causing the cam means to bring about intermittent engagement in such a manner that the driven member will be connected in driving connection with the driving member for only a portion of each revolution of the driving member. Thus, if the driven member be rotated through an angle of 10 degrees, for example, for each 360 degree rotation of the driving member, then the driven member will make one complete revolution in response to 36 revolutions of the driving member, and a speed reduction ratio of 36 to 1 will be realized. Such speed ratio may be altered by changing the period of driving engagement between the driving member and the driven member during each revolution of the driving member, and this is provided for in my invention, by so designing the cam means as to render it possible to alter the cam surface characteristics, even to the extent of realizing zero revolutions of the driven member during rotation of the driving member, which corresponds to a speed ratio of infinity, and represents a complete stopping of the driven member.

For a more detailed description of my invention, reference will now be made to the afore; mentioned accompanying drawings.

In Figure l of the drawings, I have shown my improved speed control applied to the feed mechanism I of a pellet mill, or.simi1ar type of apparatus (not illustrated), wherein moldable material is to be fed to an extruding die at a desired rate of feed. The feed mechanism comprises a. hopper 3 having a discharge passage 5. The hopper is mounted on a bracket I which in turn is supported upon the framework of the extrusion mill or the like, to which the material in the hopper is to be fed. In this discharge passage is positioned a feed screw 9 having a hollow shaft II in which is fitted and riveted a solid shaft I3 extending through and beyond the bracket I arid terminating in a reduced end section I5.

A ratchet supporting disk I 1 having an integral centrally disposed collar I9, is mounted upon and fixed to the shaft I3 by a. rivet 2| at a point just beyond the bracket. This disk I1 is formed with a peripheral flange 23 into which is fitted a ratchet 25 of ring shape. This ratchet is held in position within the flange 23 by a plurality of machine screws 21 at distributed points about the flange periphery.

On the reduced end section of the shaft I3 is mounted a pair of spaced bearings 29 and 3| respectively. One of these bearings. 3| is positioned in abutment against the shoulder on the shaft I3 formed by the reduced end section, whil the other bearing 29 is positioned adjacent the end of the reduced end section. A hollow drive shaft 33 is rotatably mounted on these spaced bearings, and at the end thereof carries a hub 35 having an integral end flange 31. The hub is keyed to the drive shaft 33. A sprocket 39 surrounds the hub and is bolted to the end flange by means of a plurality of peripherally distributed bolts 4| passing through bushings 42 of rubber or the like mounted in the sprocket, thus providing for a shock absorbing chain drive connection to the hollow drive shaft 33.

At the other end of the drive shaft adjacent the ratchet supporting disk I1, there is fixedly mounted on the shaft, a pawl assembly 43. This assembly includes an assembly cage or housing 45 formed in part by a rectangular end plate 41, one pair of diagonally opposite corners of which, at 49, have been cut off on an angle, while the remaining pair of diagonally opposite corners have been notched out, as at The rectangular end plate 41 is flanged along the remaining portions of its side and end edges to provide integral side and end walls 53 and 55 respectively, and is also provided centrally thereof with an integral collar 51 for mounting on the drive shaft 33, to which it is fixed as by welding or other means.

A cover plate 59 having a shape corresponding to the contour of the end plate 41, has a central I opening, enabling it to fit over the mounting collar 51 and abut the upper edges of the side and 'end walls 53 and 55, and is riveted in its assembled position by a plurality of rivets, including one 6| adjacent each notched corner and one 63 disposed at each end of the housing 45. The location of these rivets has been indicated, for by reason of their respective positions, they are enabled to assume additional functions besides holding the cover plate 59 in position, as will be brought out in the process of continuing the description of the pawl assembly.

Within the housing is disposed a pair of pawls 65. Each pawl constitutes a rectangular bar segment which is positioned longitudinally in sliding, engagement along a side wall 53 of the housing, with the ratchet engaging end thereof in its rest position, normally protruding through a comer opening in the housing at 49, between the wall 53 and the adjacent corner 66 of an end wall 55. The .pawl' is thereby adapted to slide into engagement with the ratchet 25, the adjacent end 66 of end wall acting as an anvil and cooperating with the side wall 53 in guiding the pawl along a linear path to and from the ratchet, as distinguished from an arcuate path. Such linear movement reduces the necessary operating power,

as well as enabling the pawl to maintain an even bearing against the ratchet teeth throughout each period of engagement, thus assuring successful operation with less wear.

The other end of each pawl is provided with an axial bore 61 to receive a pawl spring 69, one end of which is exposed and anchored in a hole 1| formed in one of the aforementioned corner rivets 6|. The spring 69 is designed to urge its associated pawl 65 into engagement with the ratchet ring 25 in the absence of any means which will preclude such engagement between the pawl and the ratchet.

A retracting lever 13 fulcrumed a.t an intermediate point about an end rivet 63 is associated with each pawl by having a tapered end 15 engaging such pawl within a rectangular notch 11 formed in a wall thereof. The other end of such retracting lever protrudes through a notchedout corner of the pawl assembly housing as 'at" 5|. To this end of the lever, there is connected'a stub shaft I9 which carries a pair of aligned -;ball

bearing mounted rollers 8| and 83 respectively. In one of its extreme positions, this lever serves to hold the pawl out of engagement with the ratchet, while in its other extreme position, it"

will permit such engagement under the urging of the pawl spring.

A pair of adjacently disposed cam disks 85 and 81 respectively are provided, each in the plane of one of the aforementioned rollers 8| and 83. These cam disks are each formed with substantially similar cam surfaces, each cam surface including a high surface on an arc portion 89 of one radius, and a low surface on an arc portion 9| of a smaller radius. Together the two cam disks provide a resulting cam surface for engagement by the aligned rollers 8| and 83 whereby the movement of the lever 13 is controlled.

' One of these cam disks 85 is provided with an integral axial mounting sleeve 93 for mounting the same for relative rotation about the drive shaft 33. The sleeve is of a length enabling it to fit between the pawl assembly housing 45 and the hub flange 31.

The second cam disk 81 is also provided with an integral axial mounting sleeve 95, adapting it for mounting about the mounting sleeve 93 of the first cam disk. The mounting sleeve of this second disk terminates in a frontal mounting flange 91 for attachment 'to the inner surface of the front wall 99 of a housing IBI which serves to enclose and protect the pawl, ratchet and cam assemblies already described.

This protective housing is formed of front and rear cylindrical sections I93 and I05 respectively, bolted together along contacting peripheral flanges I01. The housing is mounted with its rear wall I88 bolted to the bracket 1, such rear wall being formed with a rearwardly extending reduced section I09 to accommodate a ball bearing assemblyIII for supporting the shaft I 3.

Upon the end of the mounting sleeve 93 of the first cam disk 85 adjacent the hub flange 31, there is mounted an adjusting bracket I I3 which is fixed to the sleeve by 'a setscrew H5 or other well known means. This bracket extends up and over the front wall 99 of the housing in spaced relationship thereto, and carries at its upper end a locking pin II1 normally urged by a spring 9 into engagement with a toothed sector I2I, mounted on the upper surface of the housing IIII adjacent the front wall. This locking pin has a handle or grip I23 at its upper end, enabling the pin to be manually withdrawn from locking engagement with the toothed sector. This will permit the bracket to be swung through any desired anglec to be subsequently locked in any desired angular position by releasing the locking pin for engagement again with the toothed sector.

The bracket H3 is provided with an opening or window I25 and a pointer I21 extending into the opening and formed integral with the bracket. This pointer is adapted to register with markings on a suitable scale I29, which is mounted on the front wall of the housing, to indicate the angular position of the bracket in terms of speed change characteristics of the mechanism within the housing.

To give significance to the scale readings, the cam disks," and 91 must be properly adjusted. When properly adjusted, the cam surface of the bracket connected disk 95 will be so far out of matching alinement with that of the adjacent cam disk 91 that the resulting surface, upon which the rollers can travel, will represent substantially a complete circle, and this relationship will represent the condition of cam adjustment, when the bracket H3 is at its extreme left position of the scale, as viewed in Figure 2. Any subsequent movement or shift of the adjust ing bracket to the right, will tend to bring the cam surfaces of the disks more and more into matching alinement and expose an increasing portion of the cam surface of smaller radius of both disks to the rollers. The extreme positions of the adjusting bracket, as indicated on the scale, are determined by a stop pin I3I fixed in a face of disk 85 and engaging an arcuate slot I33 in the opposing face of the adjacent cam disk 31, such slot having an angular spread equal to the angle within which the bracket adjustments are to be made.

Lubrication of the spaced bearings 29 and 3I of the hollow drive shaft 33, and the mounting sleeve 93 of the cam disk 85 is provided for by forming an axial bore I35 into the end of the reduced shaft section I5 and connecting the space between the bearings 29 and 3| with this axial bore by a radial connecting bore I31 formed in the shaft. The lubricant entering the space between the bearings 29 and 3I may reach the mounting sleeve 93 of the cam disk through a perforation I39 in the wall of the main drive shaft 33. The admission and retention of lubricant within the shaft and bearing spaces is facilitated by the attachment of a lubrication fitting I to the end of the shaft, and leakage of lubricant past the front end of the mounting sleeve 93 is precluded by the provision of a sealing ring I43 in the sleeve and in frictional contact with the drive shaft. The location of the bore I35 and fitting I4I on the axis of the shaft I5 has the advantage of permitting lubrication during operation, thus avoiding the necessity of a shut down for the purpose.

In explaining the operation of the speed change mechanism as applied to the feed assembly described, we will first assume the adjusting bracket II3 to occupy its extreme left position designated by the word stop in Figure 2, and w will further assume the main drive shaft to be in continuous rotationin response to a chain drive connection to the sprocket 39, as

complete circle. Consequently, as the pawl assembly 43 rotates with the drive shaft 33, the rollers 3I33 will rotate about this surface, holding the levers 13 in retracting position, whereby the pawls will be held or retained out of engagement with the ratchet 25 throughout each entire revolution of the drive shaft. In as much as the pawls cannot eflect any driving engagement with the ratchet under these conditions, the driven shaft, and consequently the feed screw connected thereto, will not rotate.

As the adjusting bracket is shifted angularly to the right (Figure 2), the disk cam 35 will be angularly shifted about a common axis with respect to the cam 81 fixed to the front wall of the housing. The resulting cam surface developed through such relative movement of the cam disks will include a portion of each of the disk cam surfaces of smaller radius, thus enabling each pair of rollers, as they travel over this resulting cam surface, to drop to a position bringing them closer to the axis of the rotating assembly. Such freedom of movement of the rollers will permit the associated pawl spring 69 to urge its pawl into engagement with the ratchet 25, and such engagement will continue so long as the smaller radius portion of the resulting cam surface is being ridden by such rollers. Thus, each pawl will effect engagement with the ratchet during each revolution of the drive shaft, when the roller associated with that particular pawl is riding a low portion of the resulting cam surface, and the driven shaft will accordingly be rotated a portion of a revolution for each full revolution of the drive shaft, such portion being equal to twice the angle through which each pawl rotates the driven shaft. In as much as the period of engagement between the pawl and ratchet may be altered by adjustment of the adjusting bracket, it will readily be apparent that the ratio between the R. P, M. of the drive shaft and that of the driven shaft may be arbitrarily changed through a substantial range merely through adjustment of the adjusting bracket; and accordingly the rate of feed of the moldable material in I the hopper may be adjusted to suit conditions.

previously indicated. When the adjusting bracket is in this position, the resulting cam surface exposed to the rollers will be substantially a to the end of shaft I6I.

In the second embodiment of my invention as illustrated in Figures 6 through 10 inclusive, the speed control mechanism is enclosed within a housing I45 formed of telescoping sections I41 and I49 held together by the bolts I50, with the rear section I49 telescoping within the front section I41 of the housing. The feed mechanism I5I, including the hopper I53 and the discharge passage I55, is bolted to. the rear wall I51 of the housing. The screw feed element I59 in the dis charge passage has a solid shaft I6I axially extending through the housing I49, and is supported within a bearing I63 carried by the rear wall of the housing in .an integral collar I65 formed thereon for the purpose. Within the housing and adjacent the rear wall, a collar I61 k'eyed to the shaft I6I', carries a pair of similar scribed, and may be retained on the ratchet disk "I in similar manner.

The drive shaft I11 fits over the end of the screw shaft I6I in abutment against the collar I61 and is held in position by a collar I68 fixed At the forward end of the drive shaft a sprocket I19 is keyed thereto, enabling a chain drive connection to the drive shaft. At the collar abutting end, the drive shaft is of reduced section, to accommodate the pawl assembly I8I which is keyed thereto for rotation with said shaft.

This assembly includes a relatively narrow, diametrically positioned base plate I83 having an integral mounting collar I85, whereby the same may be keyed to the drive shaft. The ends of the base plate are notched back to the collar at an angle to the radius and in a direction causing the edge end of the notch I81 formed thereby, to trail the collar end during the normal rotation of the pawl assembly I8I, in the direction indicated by the arrow in Figure 10. A pawl I88 is slidably fitted within each of these notches,

and has a ratchet engaging end I9I which is normally urged in the direction of the ratchet I15 by a pawl spring I93 inserted under compression between the pawl I89 and the collar end of the notch. A stub shaft I95 extends laterally from each of the pawls, and is adapted to carry a cam engaging roller I91. Each pawl I89 is retained in position in its associated notch by a pawl retaining plate I99 which is formed with an aligned notch I of less extent, to permit for movement of the stub shaft I95 in accordance with the sliding movement of the pawl, and thereby permit proper operation of the pawls in accordance with the control exercised by the cam means to be described.

In this embodiment, as in the first embodiment described, the movement of the pawls is controlled by a cam surface resulting from the adjustment between two cam surfaces which together cooperate to provide a resulting cam surface against which the pawl rollers ride. The fixed cam element in this embodiment constitutes a flange 203 extending inwardly from the telescoping end of the rear section of the housing, and having a cam surface formed along its inwardly directed edge. v

The adjustable cam element comprises a disk 205 within the housing, adjacent the front wall, and having an integral axial sleeve 201 for mounting about the drive shaft, this disk. being provided with a peripheral cam flange 208 terminating adjacent the cam edge of the fixed cam component 203. v

An adjusting bracket 2 is keyed to the mounting sleeve 201 of the adjustable disk cam 205, and extends up the front wall of the housing in spaced relationship thereto. This bracket is perforated to provide an opening 2I8 at a point opposite the outer circular edge of the front wall, and carries a locking pin 2I5 which is affixed to the front surface of the adjusting bracket and extends through the opening to resiliently engage a toothed sector 2" aflixed to the front wall of the housing around the upper half thereof. The locking pin is formed to provide a finger grip portion 2I9 to release the pin from looking engagement with the toothed sector and permit movement of the adjusting bracket.

The cam surfaces of the cam members, like in the first embodiment, each have a high and low cam surface 22I and 228 respectively, and these cam members are adjusted so that together they provide a substantially circular surface for guidance of the pawl rollers, when the adjusting bracket is at one extreme position indicating total disconnection between the driving end of the speed change mechanism and the feed mechanism.

The operation of the mechanism is quite similar to that of the first embodiment, in that movement of the adjusting bracket 2 will shift one of the cam elements 205 with respect to the other 208 to expose to the rollers varying proportions of the low and high cam surfaces, whereby the pawls may be caused to engage the ratchet I15 and rotate the feed screw I59 for different periods of each revolution of the drive shaft I11, in accordance with the adjustment of the adjusting bracket.

It will be apparent from the above described embodiments of my invention that they fulfill all the objects set forth by me. While I have described these two embodiments in great detail, it is apparent that they are susceptible to changes and variations, without departing from the spirit of my invention, and I accordingly do not desire to be limited in my protection to the details as disclosed and described by me, except as may be necessitated by the prior art and the appended claims.

I claim:

. 1. In combination, a pair of cam surfaces, each including an arc section of a particular radius and an arc section of a different radius, means for supporting said cam surfaces adjacent each other with corresponding arc sections in substantial alinement whereby each cam surface is utilizable in its entirety, means for adjusting one of said cam surfaces with respect to the other about a common axis to reduce the utilizable portion of one of said are sections of each of said cam surfaces to the point of obliteration of such utilizable portion, and means for coupling a driving member and a driven member in accordance with the adjustment of said cam surfaces, said means including a ratchet connected to one of said members and a pawl assembly connected to the other of said members, said pawl assembly comprising an assembly housing having an open corner bounded by a side wall and an end wall of said housing, a pawl in said housing positioned in'sliding engagement along said side wall and having its ratchet engaging end protruding through said comer opening in contact with the adjacent edge-of said end wall.

2. A pawl assembly comprising an assembly housing having an open corner bounded by a side wall and an end wall of said housing, a pawl in said housing positioned in sliding engagement along said side wall and having its ratchet encasing end protruding through said comer opening in contact with the adjacent edge of said end wall.

3. A pawl assembly comprising an assembly housing mounted upon a shaft passing centrally therethrough, said housing having openings facing outwardly away from said shaft, a pair of parallel guide surfaces provided in said housing adjacent each of said openings and offset-with respect to the center of said shaft, a pawl having the general form of a rectangular bar segment positioned for linear sliding movement between said guide surfaces, with its ratchet engageable end facing its associated opening in said housing, and means exerting a continual thrust against the other end of each of said pawls tending to force said pawls through said openings along the path of such linear sliding movement and away from said shaft.

EDGAR T. MEAICIN.

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