US2993569A

US2993569A - Automatic lock for small shafts

Info

Publication number: US2993569A
Application number: US818680A
Authority: US
Inventors: Jr Howard W Cole
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-06-08
Filing date: 1959-06-08
Publication date: 1961-07-25
Anticipated expiration: 1978-07-25

Description

1, WW A 8 [/42 I K t/ll 1M' 86 INVENTOR ATTORNEYS July 25, 1961 Filed June 8, 1959 United States Patent Olilice 2,993,569 Patented July 25., 1961 2,993,569 AUTOMATIC LOCK FOR SMALL SHAFIS Howard W. Cole, Jr., 12 Vale Drive, Mountain Lakes, NJ. Filed June 8, 1959, Ser. No. 818,680 9 Claims. (Cl. 188-1'34) This invention relates to shaft locks of the type wherein a driven connector can be rotated from a driving connector, but rotary force applied to the driven connector cannot be transmitted back to the driving connector.

One successful type of shaft lock employs over-running brakes which have two sets of brake rollers, one set of which jams to prevent rotation of a driven connector in one direction, and the other set of which jams to prevent rotation of the driven connector in the other direction. Such shaft locks are provided with means for releasing the jammed brake rollers when the driving connector is actuated. 'Ihere are motion-transmitting connections between the driving connector and the driven connector with lost motion so that the driving connector will operate the jammed brake rollers to release them before taking up the lost motion between it and the driven connector.

lIt is an object of this invention to provide an improved shaft lock, of the character indicated; and more especially, it is an object of this invention to provide a shaft lock in which opposing reactions are set up to release the locking element, and these opposing reaction forces are exerted on the locking element themselves.

In the most eicient shaft locks of the prior art, it has been the practice to employ blocks or shoes for moving the locking elements of the brake into released positions; and it is an object of this invention to provide a simplified construction which makes the unlocking of blocks or shoes unnecessary by exerting the unlocking or releasing forces directly on the locking elements, or rollers, of the brake.

Another object of the invention is to provide an improved automatic shaft lock, of the character indicated, with means for adjusting the back-lash of the locking elements of the brake, and in one embodiment of the invention, such adjustment is provided for each individual locking element.

One of the advantages of the present invention, with its simplified construction, is the suitability of the invention for shaft locks of.very small size. The use of fewer parts is especially advantageous in very small shaft locks because the parts have to be accurately made and the cost is substantially reduced by having fewer parts.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

FIGURE l is a sectional view, takenon the line 1-1 of FIGURE 2; Y

l FIGURE 2 is a sectional View through an actuator made in accordance with this invention, the section being taken on the line 2 2 of FIGURE 1;

FIGURES 3 and 4 are sectional views taken on the lines 3--3 and 4-4, respectively, of FIGURE 2; and

FIGURE 5 is a view similar to FIGURE 2, but on a reduced scale and showing a modified form of the invention.

The actuator construction shown in the drawing includes a xed frame to which is connected a housing 11. An outer brake element 12 is secured to the housing 11 and is a fixed unit with the frame 10 and the housing '11. The outer brake element 12 is shown as a cylindrical sleeve and its inner surface provides a bearing for a driven connector 14 and for rollers 16 which comprise the locking elements of the brake. These rollers 16 contact with the inner surface of the outer brake element 12 beyond a shoulder 17 of the driven connector 14.

The housing 12 has a cylindrical bearing surface 18 beyond the outer brake element 12, and in the construction shown, the bearing surface 18 is ush with the bearing surface in the brake element 12, but this is not essential, nor is it necessary that these bearing surfaces be cylindrical. They may be tapered or may be zone surfaces of a sphere or have other contours about a longitudinal axis, indicated by the line 20 in FIGURE 2 and by the point 20 in FIGURES l, 3 and 4. The construction illustrated with a continuous cylindrical bearing in the outer brake element 12 and the housing 11 has the advantages of being more economical to manufacture.

A driving connector 22 extends into the housing 11, at the opposite end from the driven connector 14 and this driving connector 22 rotates in the bearing provided by the surface 18. A counter-bore 24 in one end of the driving connector 22 receives a reduced-diameter end of the driven connector 14 and the driving connector 22 is connected with the driven connector 14 by a pin 26 which is rigidly secured to one of the connectors and which passes through an opening in the other connector with clearance to provide lost motion in the connection formed by the pin 26.

`In the construction illustrated, the pin 26 lits tightly in the end of the driven connector 14 and passes loosely through an opening 28 in the end portion of the driving connector 22. Thus the pin 26 transmits rotary motion of the driving connector 22 to the driven connector 14 but with some lost motion at the start of the rotation in either direction for releasingthe locking elements of the brake, as will be more fully explained.

There is an annular groove 30 in the circumference of the driving connector 22 for holding a sealing ring 32. This sealing ring 32 ts into a counter-bore 34 in one end of the housing 11. There ,is a retainer 36 around the driving connector 22 and the counterbore 34; and this retainer 36 is held in place by a snap ring 38 which fits into a circumferential groove 40 in the driving connector 22 just beyond therend face of the housing 11. This snap ring 38 extends radially part way across the end face of the housing 11 and provides a thrust bearing for preventing movement of the driving connector 22, and its connected parts, toward the right in FIGURE 2.

A pin 42 extends through the driven connector 14 just beyond the other end of the housing 11 and extends across the end face of the housing 11 to serve as a thrust bearing for preventing the driven Yconnector 14 and its connected parts from being displaced toward the left in FIGURE 2. This pin 42` also serves to limit the rotation of the mechanism, there being a stud 44 extending from the end face of the housing 11 in the path of the pin 42. This limits rotation of the driven connector 14 to something less than 360. The apparatus illustrated is intended particularly for operating a potentiometer where less than a full circle of movement is desired; but it will be understood that the invention can be applied to other installations where a number of revolutions, or unlimited numbers of revolutions may be desirable; and in such a case no stop, such as the stud 44, would be provided. f

Ihe actuator as shown in the drawing does not show the means by which the driving connector 22 is rotated or the means which are turned by the driven connector 14. It will be understood that the driving connector 22 can b e rotated by a tool, a manually-actuated operator, a motor or any other expedient for imparting rotary motion 3 to the connector 22. It will be further understood that the driven connector 14 can be connected to a potentiometer brush, to a gear, crank arm, or any other expedient for producing 4the motion for which the actuator is used, andfor-holding the actuated part inthe position yto which it isshifted by this motion.

The portion ofthe drivenV connector 14 between the shoulder 17 and-.the end face of the driving connector 22 is of non-circular cross section. 'This non-circular portionofthe driven Yconnector 14 is shown in section on FIGURE l. At its maximum width, the driven connector 14Y has arcuate faces 48 which bear against the cylindrical innerbearing surface of the sleeve 12. and are continuations of the cylindrical surface of the driven connector 14 which rotates in the sleeve or outer brake element 12 as a bearing. However, most of the perimeter of the driven connector 14, at the section shown in FIGURE l, is cut away to provide cam faces 50 with which the locking elements or rollers 16 contact. Y

In the simplied construction illustrated in the drawing, there are only four rollers 116, two for preventing rotation of the driven connector 14 in one direction, and two for preventing its rotation inthe other direction. These rollers 16 ofthe diiferent sets areurged apart by springs 52. Thesesprings-SZ move the rollers 16 in directions to hold them simultaneously incontact with the cylindrical bearing surface of the outer brake element 12 and the face of the particular cam surface 50 which operates against each roller 16.; In the construction illustrated, the cam faces 50 are plane surfaces. They may have other contours depending upon the particular mechanical advantage which the designer wishes to obtain in the operation of the shaft lock, but different mechanical advantages can be obtained by changing the angleof these plane surfaces; and there is a. distinct advantage in the economy of manufacture byemploying plane surfaces for use as the cam faces Whenever the driven connector 14 tends to turn in a clockwise direction in FIGURE 1, the cam face 50 under the upper left-hand roller 16 will jam that roller against the outer brake element 12 whichA is xed, and this prevents rotationof the driven connector 14 in a clockwise direction. The'diametrically opposite roller 16,V that is, the lower right-hand roller in FIGURE l, willbe similarly jammed against the fixed outer brake element 12. Any time that the driven connector 14 tendsto rotate in a counter-clockwise direction, the cam face 50 under-the right-hand roller 16.in FIGURE 1, and the corresponding cam face 50-in contact with the lower leftfhand roller 16, jam these `rollers against the fixed outer brake element 12 and preventY rotation ofthedriven connector 14 in a counter-clockwise direction. Y

When the driven connector 14 tends to move counterclockwise, the movement of the cam faces 50 with respect to the upper'left-hand Yroller 16 and the lower right-hand roller 16 in FIGURE` 1 merely tends to open up a clearance for these rollers 16V between theV cam faces'50 and the bearing surface of the outer brake element 12. Be-

cause the partsr vare so constructed that the maximum spacing of the camV faces 50 from the cylindrical bearing surface of theV outer brake element 12 is slightly greater than the diameters of the rollersV 16, the springs'52 push the rollers 16 along'the cam faces` 50 to locations slightly beyond the region of maximum radial spacing of the cam faces 50 from thi'srinner bearingVv surface of the outer brake element 12. Y p Y Although the lockingV elements or rollers'16 jam to'rprevent movementrof the driven connector 14.whenever that connector starts to rotatein either'direction, they do not y preventY rotationof the driving connector 22,'V nor do Vthey prevent the jdriven connector-14, fromA being rotated by force supplied by the driving connector 22 through the pin 26 to the drivenconnector 14. This result follows' from Ithe Vf actthat whicheverset ofv rollers 16 is'jammed to Vprevent.n,rotation.oftheI driven connector 14` in one direction or the other, this setY of roller-S16 is released by rotation of the driving connector 22 with respect to the driven connector 14 and such relative movement is made possible by the lost motion in the connection provided by the pin 26.

Referring to FIGURE 2, theV left-hand ends of the rollers 16 extend into recesses 56. in the end .face of the driving connector 22. The wallsV of these recesses 56 provide abutment surfaces which contact with .the rollers 16 to move them in a manner which will be more fully described.

The right-hand ends of the rollers 16 extend into recesses 58in the shoulder 16 of the driven connector 14. In the construction illustrated, thelrecesses 56-are tapered, but the recesses 58 Vare cylindrical. When the actuator is properly adjusted, each end of each of the rollers 16 fits loosely in the corresponding socket or recess 56 Gr.58. The ends of the rollersA are thus'free to move in the

socket

56 and 58. They/may rotate or move toa limited extent axially or move into skewed positions, and this combination of movements will be described herein as universal movement with respect to the abutment surfaces provided by the walls of the sockets 56. and 58.

The movement ofthe Arollers 16 with respect to the abutment surfaces provided by the sockets 56. and 58, particularly the skewingmovernent, is necessary in order to obtain the` reaction-unlocking feature of thisinvention. This reaction-unlocking feature makes the actuator operate with the application of less force to theV drivingconnector 22, and it will be best. understoodby description of the specific operation of the actuator.

For example, the actuator maybe considered. as locked bythe upper right-hand and lower left-hand rollers 16 in FIGURE l. Thismeans that the actuator has locked in response to an effort by the driven connector 14 to move counter-clockwise. This effort maybe the lresult of a continuous load on the driven connector 14 which tends to rotate that connector in a counter-clockwise direction in FIGURE 1.

The driving connector may be next rotated in a counter. clockwise direction in FIGURE l; the driving connector 22, being ahead of the plane of section of FIGURE l, but it being understoodthatthe forward ends of the rollers 16, that is,y the endtoward the reader in FIGURE l, are the ones which extend into the recesses 56 (FIGURE 2) of the driving connector 22. VSuch rotationof the driving connector 22 will takeupthe small amountY of lost motion resulting from the loose iit of the roller 16 in the sockets of thedriving connector and vwill'thenY urge Vthe driving connector ends Vof-the roller 16 to` move counterclockwise in FIGURE 1. Y

This force urging thedriving connector `Vends of the rollers 16 .to move `can ,havetwo diierent results. If Veach of the jammed rollersis not too tightly jammed bethe jamming of the roller sbecauseit willhavemoved the roller into a positionVV where the distance betweenthe cam faceand the fixed outerbrake .element 1-2 is ofi-greater Y radial extent.

l thus releasing theactuator.

y From the'aboveldescription, it'will .be apparentthat a Y force supplied tolocked'or jammed rollers 16, by the. driving connector 22', sets up a" reaction Vtending to move the t'nid portion of each roller 16 in one direction and the driven connector end portion of the roller in the opposite direction. Thus, the actuator is released by either moving the mid portion of the roller 16 along its cam face 50 in a direction to release the actuator or moving the driven connector 14 in a direction to give the cam face 50 a motion that releases the actuator.

Operation of the actuator by the driving connector 22 in a direction in which the actuator is not locked by the upper right-hand and lower left-hand rollers 16 in FIG- URE l will skew the rollers slightly until the lost motion of the pin 26 (FIGURE 4) is taken up, and then the driving connector 22 will rotate the driven connector 14 in a clockwise direction so as to move the cam surface 0 (FIGURE l) in the direction which increases the radial clearance between the cam surface and the outer brake element 12 at the location of the upper right-hand and lower left-hand rollers 16 by which the actuator was locked.

Operation of the actuator is dependent upon the proper adjustment of clearance and back-lash of the rollers 16 with respect to the

sockets

56 and 58 into which the ends of the rollers extend. It will be evident that the rollers 16 must have sufficient play for lost motion in the sockets so that they can move into skewed positions. It will also be evident that the rollers 16 must have suflicient play so that the rollers by which the actuator is locked, for example, the upper right-hand and the lower left-hand roller 16 in FIGURE l, so that the motion necessary to release these rollers can take place before the actuator will be locked by the other rollers which resist rotation of the driven connector 14 in the opposite direction. That is, the driven connector 14 must be able to move suiciently to relieve the pressure of the cam faces 50 against the upper right-hand and lower left-hand roller 16 in FIGUR-E 1 before the upper right-hand and lower left-hand rollers lock the driven connector 14. In actual practice, this motion is extremely small and in accurately made actuators it is not a noticeable motion of the driven connector 14 but merely a relieving of the stress in one direction without actually producing rotation of the connector 14. Theoretically, this is a motion of the connector, at least to the extent required internally to change the elastic forces exerted by the material of which the driven connector is made.

If the play or clearance between the roller 16 and the recesses S6 and 58 is too small, then the actuator will never unlock in response to rotation of the driving connector 22, because the roller'16 cannot move suiciently to produce the unlocking action above described. On the other hand, if the clearance of the roller 16 is excessive in the

recesses

56 and 58, the actuator will not unlock because the lost motion of the pin 26 will be taken up before the rollers 16 have made the necessary motions to unlock the actuator; and if this occurs the driving connector 22 will be exerting a rotary force to turn the driven connector 14 in such a way as to cause the actuator to lock against rotation in either direction in the same way as if the rotary force were applied directly to the driven connector 14.

The only reason that the actuator can be turned by the driving connector 22, and cannot be turned by rotary force applied directly to the driven connector 14, is that the driving connector 22, when the parts are properly adjusted,'unlocks the actuator before the play or lost motion of the pin 26 is taken up and thus before rotation is imparted by the driving connector 22 to the driven connector 14 in the same direction as the driving connector is turning.

In the actuator show'n in FIGURES 1-4, the play or back-lash for the rollers 16 is adjusted separately for each individual roller. The structure by which this adjustment is eiected is best shown in FIGURE 2. A rod 64 slides freely through an opening 66 in line with each of the recesses 58. At the end of the opening 66 remote from the recess 58, there is a threaded counterbore 70 which receives a screw 72. This screw 72 is rotated one way or the other to adjust the back-lash of the actuator.

The screw 72 can be used to push the rod 64 to the left in FIGURE 2 to reduce the clearance of the roller 16 in the recess 56. This limits any sliding movement in the recess 58 as well as in the recess 56. Skewing of the roller 16 holds the rod 64 back against the screw 72 land it is not necessary to have any connection between the screw 72 and the rod 64 for pulling the rod 64 toward the right in FIGURE '4 when it is desired to increase the amount of back-lash. It will be understood that all of the rollers 16 have similar adjusting means to that shown for the upper roller 16 in FIGURE 2.

FIGURE 5 shows a modified form of the invention. Corresponding parts in FIGURE 5 are indicated by the same reference characters as in FIGURES 1-4 with a prime appended. The only important difference between the construction shown in FIGURE 5 and that shown in the other gures is in the adjustment of the back-lash of the actuator. Instead of having means for adjusting the clearance and back-lash of each roller individually, the construction shown in FIGURE 5 has means for adjusting the clearance and back-lash for all of the rollers simultaneously. This result is obtained by having the rollers 16' constructed with tapered end portions at both ends of each roller and by having tapered recesses 56' and 58' in the driving connector 22' and the driven connector 14.

Means are provided for moving the entire driven connector 14 axially with respect to the driving connector 22', to reduce the axial distance between the recesses 56' and S8'. These means include a screw 82 which contacts with a shoulder 84 in a counter-bore at one end of a passage 86 through which the screw 82 extends to a threaded opening 88 in the driving connector 22. The diameter of the passage 86 is large enough to permit the screw 82 to rotate freely with respect to the driven connector 14', and when the screw 82 is made with the threaded portion long enough to reach into the passage 86, the threads have no effect on the driven connector 14 because there are no threads in the passage 86.

Rotation of the screw 82 in one direction moves the driven connector 14 toward the driving connector 22', as previously explained; and rotation of the screw 82 in the other direction permits the rollers 16', upon their next Skewing operation, to push the shoulder of the counter-bore to the right against the head of the screw 82 so that in the operation of the actuator the shoulder at the end of the counter-bore 84 is always Ein contact with the head of the screw 82.

Because of the axial movement of the driven connector 14 with respect to the driving connector 22', in the adjustment of the back-lash of the actuator shown in FIGURE 5, it is advantageous to have the pin 26 pass through an opening, corresponding to the opening of FIGURE 4, with the opening slightly elongated so that the lost motion of the actuator between the driving connector 22' and the driven connector 14 is not aiected by the adjustment of the back-lash. Such elongation provides for greater manufacturing tolerance; but if the actuator is made with precision accuracy, the elongation is not necessary because the amount of lost motion between the driving connector 22' and the driven connector 14' can be less when the actuator is adjusted for reduced back-lash.

The preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made, and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. An actuator comprising brake means with inner and outer elements, and rollers between the inner and outer elements, one of said elements havinga circular bearing surface with which the rollers contact, and the otherof-said elementshaving camY surfaces spaced from theccircular bearing, surface and that jam some of the rollers againstV the circular bearing surface when the .elements are moved angularly with respect to one another about the center axis of theV circular bearing surface, the rollers being rangularly spaced from one another about said axis, means for preventing rotation of one of said elements, a drivingconnector at one end of the rollers, a driven connectorat theother end of the rollers, each of the connectors being rotatable about a longitudinal axis substantially coincident with the axis of the circular bearing surface, abutment surfaces on. both of the connectors and adjacent to end .portions of the rollers and extending into the spaces between successive rollers so that movement of the abutment surfaces about said axis causes. movement of `the rollers, the end portions of the rollers having universal movement with respect to theabutment surfaces whereby the rollers can skew into positions at different angles with respect to the center axis of the circularrbearing surface when moved at either end by the abutment surfaces, and a driving connection between the ydriving connector and the driven connector, said driving connection having lost motion therein sucientto causethe driw'ng connector to move the rollers before the lost motion is taken up.

2. The actuator described in claim 1 'and in which the circular bearing surface is cylindrical and the rollers contact with said bearing surface for only a portion' of the axial length of said bearing surface, but the rollers have limited axial movement that changes their region of contact with the cylindrical surface.

3. The actuator described in claim l and in which the driving connector and they driven connector each have a face confronting a corresponding face ofthe other and extending acrossthe ends of the space between the cam surfaces and the circular. bearing surface, and the .rollers are located between the confronting faces of the driving connector andthe driven connector.

4. The actuator described in claim 3 and-in which there are recesses in said confronting faces and the rollers have end portionsY which Aextend into the recesses, the sides of said recesses constituting the abutment surfaces thatare adjacent to the end portions of the rollers.

5. The actuator described in claim V4 and inwhich there are opposing faces on an end portion ofv each roller andthe recess of one of the connectors into which the `end portion of the roller extends, and in which at least one of said opposing faces is tapered, and there are means adjustable toward and from the recesses'in the connector to adjust back-lash of the actuator.

6. The actuatordescribed in claim Sand in which thereare separate means for adjusting each of the rollers to adjust the back-lashof the actuator.V

7."I'hel actuator 'described in claim 5'V and iny which there arecommon means for adjusting all of the rollers simultaneously to adjustthe back-lash of the actuator.

8. The actuator described in claim and `in which all of the rollers have tapered end'portions and all of the recesses inv both ofthe connectors aretapered for receiving the tapered end portions of the rollers.

9. An actuator comprising ,brake means with inner and outer brake elements, rollers between the inner and outer brake elements, the outer brake element having a cylindrical surface -with which the rollers contact, means for holding the outer element in a fxed position, cam surfaces on the inner brake element and with which the rollers cantact, there beinga diiferent cam surface foreach roller and the alternating cam surfaces around the brake means being disposed to thrusttheir rollers outwardly when the inner brake elementis rotated in a different direction asV the inner brake element rotates about a longitudinal axis, a driving connector having a face at one end of the rollers, and a driven connector by which the cam surfaces are carried, the driven connector having a shoulder with a face at the other end of the rollers, both of the connectors being rotatable `about a longitudinal axis, and both of the connectors having confronting faces with sockets into which endl portions of the rollers'extend with some clearance between the end portion of the rollers andthe confronting surfaces of the sockets, whereby therollers have'some lost motion in the sockets and are capable of movinginto a skewed position when one of the confronting end faces rotates with. respect. to the other about said longitudinal axis, and a drivingconnection between the driving connector and the; driven connector, said driving connection having somewhat more lost motion than that of the rollers in the sockets ofthe confronting end faces.

References-Cited in the le of this patent UNITED STATES -PATENTS 814,301 Kunz .Mar. s, 1906 2,458,441 starkey 7.--. Jan. 4, 1949 2,543,840 Fisher Mar. 6, 1951 2,812,044 co1@V Nov. 5, 1957 2,865,479 Hungerford Dec. 23, 1958 2,870,887 C01@ Jan. 27, 1959 FOREIGN PATENTS 863,455 'France Jan. 2,1941