US 3586138 A
Description (OCR text may contain errors)
United States Patent  Inventor Thomas H. Eagle Cape Vincent, NY.
 Appl. No. 882,655
 Filed Dec. 5, 1969 I45] Patented June 22, 1971  Assignee General Signal Corporation Continuation-impart of application Ser. No.
726,766, May 6, i968.
 HYDRAULIC'ALLY OPERATED LOCK 2.873.579 2/1959 Safford 188/265X Primary Examiner-Duane A. Reger Assistant Examiner-John J. McLaughlin Attorney-Dodge and Ostmann ABSTRACT: Fluid pressure operated lock mechanism for reciprocating elements particularly suited for use with hydraulic brake cylinders on railway cars.'The lock mechanism includes a lock which is biased toward lock position and is yieldingly held in both the lock and unlock positions by a detent. One fluid pressure motor overpowers the detent and allows the biasing Spring to move the lock into locking position, and another such motor overpowers the detent and moves the lock to unlock position. The lock itself may be a canting ring adapted to grip the reciprocating element, or a circumferential series of rollers which can be wedged selectively between that element and a camming surface, or a similar group of rollers which act to force the sliding element into engagement with a friction shoe. ln the last mentioned versions, the rollers may be moved out of wedging engagement simultaneously, or they may be unlocked sequentially in groups or individually.
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INVENTOR THOMAS H ENGLE BY i ATTORNEYS PATENTEUJUNZZIH?! 358E138 v sum 3 0F 3 "I II/ ii If INVENTOR THOMAS H. ENGLE BY Q W ATTORNEYS HYDRAULICALILY OPERATED LOCK MECHANISMS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of parent application Ser. No. 726,766, filed May 6, 1968, now US. Pat. No. 3,508,794 and includes the lock mechanisms divided from that application.
BACKGROUND AND SUMMARY OF THE INVENTION Copending application Ser. No. 726,766, mentioned above, discloses several hydraulically operated handbrake and combination handbrake-service brake circuits which require a locking mechanism for the brake cylinder which can be applied and released in response to hydraulic pressure signals. The object of the present invention is to provide a reliable mechanism of this kind.
According to the invention, the locking mechanism includes a lock which is biased toward locking position and is yieldingly held in both the locking and unlocking positions by a detent. The lock is applied by a fluid pressure locking motor which overpowers the detent and allows the biasing means to move the lock to locking position, and is released by a second pressure motor which overpowers the detent and itself moves the lock to unlocking position. In some embodiments, the lock takes the form of a canting ring which, when tilted out of a plane normal to the axis of the brake cylinder, grips the piston rod and prevents its retraction. In other embodiments, intended for use with smaller brake cylinders, the lock takes the form of a circumferential series of rollers which are adapted to be wedged between the piston rod and a stationary inclined cam surface. The series of rollers may surround the piston rod, in which case the radial forces acting on the rod are balanced, or the rollers may all be disposed at one side of the rod and serve to force the rod against a cylindrical friction shoe located at the opposite side. The use of the friction shoe reduces the normal forces acting on the rollers, and thereby reduces the pressure needed to release the lock. Moreover, the shoe gives greater insurance against inadvertent release of the lock under impact loading conditions. In any of the roller embodiments, the release pressure may also be reduced by causing the rollers to be moved to unlock position in sequence, rather than simultaneously.
BRIEF DESCRIPTION OF THE DRAWINGS Several embodiments of the invention are described herein with reference to the accompanying drawings in which:
FIG. 1 is an axial sectional view of one version of the invention which employs a canting ring lock.
FIG. 2 is an axial sectional view of an alternative canting ring type of lock mechanism particularly useful in tread brake units.
FIG. 3 is an axial sectional view of an embodiment employing the wedging roller type of lock.
FIG. 4 is an enlarged sectional view taken on line 4-4 of FIG. 3.
FIG. 5 is an enlarged view of a portion of the mechanism shown in FIG. 3 illustrating a convenient way in which sequential release of the rollers can be effected.
FIG. 6 is a sectional view similar to FIG. 4 showing an alternative form for the cam surface.
FIG. 7 is a sectional view similar to FIGS. 4 and 6 showing how a friction shoe may be incorporated in the lock.
DESCRIPTION OF THE FIG. 1 EMBODIMENT As shown in FIG. 1, the novel lock mechanism 11 is associated with a hydraulic brake cylinder 12 including a working space 13, a single-acting piston 14, and a return spring 15. The lock mechanism comprises a lock ring 16 which encircles piston rod 17 and is arranged to pivot about a fulcrum point 18 between the illustrated unlock position, in which it is normal to and permits substantially free motion of the piston rod,
and a canted, locking position, in which the oblique corners defined by its flared inner peripheral surfaces 19 and 21 frictionally bind the piston rod and prevent its retraction. Lock ring 16 is biased toward the locking position by a spring 22 and is actuated by a pair of opposed fluid pressure motors 23 and 24 which act on it through an actuating member 25. The resistance to flow of oil into and out of motors 23 and 24 and the friction of the movable motor parts tends inherently to maintain lock ring 16 in each of its two positions. However, more positive insurance against inadvertent application or release of the lock is provided by including a detent. In FIG. I, the detent 26 takes the form of a Belleville spring whose inner and outer peripheries are held captive in member 25 and in the casing which encloses lock mechanism 11. In cases where damage to or malfunction of the hydraulic circuit precludes unlock motor 24 from performing its intended function, the lock can be released by turning emergency release screw 27 in a direction that causes it to push ring 16 to the upright position.
While as explained in application Ser. No. 726,766, the hydraulic handbrake circuit can take several different forms, it is assumed herein that it is designed to pressurize working space 13 and motor 23, and vent motor 24, during a handbrake application, and to pressurize motor 24, and vent motor 23 and space 13, during a release. During the initial stage of an application, the pressure in space 13 and motor 23 is relatively low because cylinder 12 need overcome only the relatively small resisting forces associated with take up of slack and brakeshoe clearance. Therefore, initially, Belleville spring 26 holds lock ring 16 in the unlock position and prevents it from dragging on piston rod 17 After the shoes move into contact with the wheels, the resistance encountered by cylinder 12, and consequently the pressure in space 13 and motor 23, will rise. Now, lock motor 23 overpowers detent 26 and retracts member 25, so spring 22 tilts ring 16 to the locking position. Inasmuch as lock 16 prevents only retraction of rod 17, movement of the lock to this position prior to the end of the application cycle will not preclude cylinder 12 from fully applying the brakes.
Once the brakes have been set, ring 16 will keep them in that condition. Therefore, it is immaterial that the pressure in space 13 and in motor 23 may, in time, be dissipated through leakage. Moreover, since lock ring 16 is held in the canted position by spring 22, the lock will not be released by the momentary relaxation in piston rod force which may result from the shocks accompanying impact of another car.
In order to release the handbrake, working space 13 and lock motor 23 are vented, and unlock motor 24 is pressurized. When the pressure in motor 24 becomes sufficient to overcome the binding force existing between lock ring 16 and piston rod 17, this motor overpowers Belleville spring 26 and causes member 25 to move ring 16 to the upright, unlocking position. As a result, the brakes immediately release.
DESCRIPTION OF THE FIG. 2 EMBODIMENT FIG. 2 shows an alternative lock mechanism llla which is considered particularly suitable for use in tread brake units,
such as the one disclosed in copending application Ser. No. 788,775, filed Jan. 3, 1969, now US. Pat. No. 3,576,615 because it minimizes length, which frequently is a critical dimension in this type of brake. The significant parts of the alternative mechanism are identified by the same numerals as their FIG. 1 counterparts, with the postscript a added to avoid confusion, and the construction of this embodiment should be evident from the drawing. However, it might be helpful to mention that the detent 26a in this embodiment comprises several circumferentially spaced balls which are arranged to be received in either one of a pair of peripheral grooves formed in member 25a, and each of which is biased inward by one or more small Belleville springs 28. It also will be noted that the biasing spring 22a reacts between member 25a and lock ring 16a rather than between the lock ring and the casing which encloses the mechanism. Inasmuch as the FIG. 2 lock mechanism operates in the same manner as the mechanism 11 of FIG. 1 and performs the same functions, further description would be superfluous.
DESCRIPTION OF THE EMBODIMENT OF FIGS. 3-7
Although the canting ring type of lock employed in the embodiments of FIGS. 1 and 2 is practical in cases where the piston rod 17 or 17a has a diameter on the order of 2 inches or more, it is not considered practical in the scaled down version needed for substantially smaller rods because of stress and manufacturing tolerance considerations. Therefore, if the piston rod has a diameter of the order of 1 inch or 1% inch, it is recommended that one of the wedging roller types of lock shown in FIGS. 3-7 be used.
Referring to FIG. 3, the mechanism 11b employs a lock in the form of a plurality of uniformly spaced rollers 16b which surround piston rod 17b and are located in a tapered space 30 formed between the rod and an encircling conical cam surface 29. The exact number of rollers employed is not critical, but eight seems ideal. The rollers 16b are held captive in slots 31 formed in actuator member 25b so that their axes are transverse to the longitudinal axis of rod 17b, and are biased in the wedging direction, i.e., toward the small diameter end of space 30, by a spring 22b in the form of an elastic O-ring confined between them and a portion of actuator 25b. Each roller 16b has a central concave portion 32 curved to fit rod 17b, and a pair of convex end lands 33 curved on the same radius as surface 29 at the theoretical plane of contact. This arrangement insures line or surface contact between the rollers and the mating parts 17b and 29, and thus keeps Hertz stresses within tolerable limits.
As in the embodiments of FIGS. 1 and 2, the actuator member 25b of FIG. 3 is equipped with a detent 26b. In this case, however, the detent is in the form of a snap ring carried in a groove formed in the periphery of member 25b and which is adapted to elastically expand into one or the other of a pair of V-grooves located in the surrounding stationary structure. The V-groove which defines the illustrated unlock position is so located that the rollers 16b are positioned in a region of the tapered space 30 where they fit loosely between rod 17b and the cam surface 29. The other V-groove defines the lock position, and it is so located that the rollers 16b are able to wedge themselves between surface 29 and the rod 17b.
When the FIG. 3 mechanism is in use and a handbrake application is initiated, lock motor 231: will overpower detent 26b and shift actuator member 25b to the right to the lock position. Since member 25b acts on the rollers through O-ring spring 22b, the rollers are simultaneously moved toward the narrow end of the tapered space 30 and into wedging relation between piston rod 17b and surface 29. Since the rollers 16b can move relatively to actuator member 25b a limited distance in the longitudinal direction, manufacturing tolerances will neither preclude member 25b from shifting all the way to lock position nor preclude rollers 16b from reaching the wedging position. Once the wedging condition has been established, rod 17b will be locked against retraction, i.e., movement to the right in FIG. 3; consequently, dissipation of the pressure in the brake cylinder or in lock motor 23b will not effect release of the brakes.
As in the case of the other embodiments, the lock mechanism of FIG. 3 can be released by pressurizing motor 24b and venting motor 23b. When the pressure in unlock motor 24b becomes high enough to overcome the wedging forces acting on the rollers 16b, motor 24b will overpower detent 26b and move actuator member 25b to the left. This action causes the walls 34 of slots 31. to push the rollers 16b toward the larger diameter end of tapered space 30, thereby freeing rod 17b and allowing it to retract.
1n the hydraulic handbrake circuits of application Ser. No. 726,766, the pressures required to operate the brake cylinder and the lock and unlock motors are developed by a pump which is driven by a handwheel of the type normally used in a conventional mechanical handbrake. It obviously is desirable that the operating characteristics of the hydraulic handbrake resemble as closely as possible those of its mechanical counterpart, and, therefore, the new scheme should require about the same amount of operator effort. This goal presents no particular problem as far as brake applications are concerned, as long as the parts are properly dimensioned. However, release of the brakes is a different matter. The problem here stems from the fact that the wedging forces applied to the rollers 16b in FIG. 3 normally are quite high. This means that the pressure required to release the lock is high, and that the resistance the crewman encounters in rotating the handwheel in the release direction will be much higher than the resistance he has learned to expect from his experience with mechanical handbrakes. In order to eliminate this disadvantage, it is recommended that the FIG. 3 embodiment be designed to effect sequential release of the rollers either in groups or individually. As shown in FIG. 5, this is accomplished simply by merely providing a longitudinal offset X between the walls 34 of the slots 31 in actuator member 25b. With this arrangement, the maximum force which motor 24b must exert depends upon the wedging force developed on only one or a few of the rollers 16b, and consequently the actuating pressure required to release the lock is materially reduced. In a case where eight rollers were used, it was found that an acceptable force level was achieved by releasing the rollers in two groups of four rollers each. It makes no difference which rollers are in each group, but it is convenient to assign the four rollers at one side of the axis to one group and the balance to the second group. It will be noted that this expedient has no adverse effect upon the wedging capability of the rollers because the slight differences in the longitudinal dimensions of the slots 31 is inherently compensated by nonuniform compression of the O- ring spring 22b around its circumference. In other words, since the degree of compression of the O-ring can vary around its circumference, the axes of rollers 16b will still lie in a common plane normal to the axis of rod 17b when the mechanism is in lock position.
The wedging roller design illustrated in FIGS. 3-5 has proven satisfactory, but its success depends upon the validity of the assumption that the rollers 16b in the actual unit will wedge against that portion of cam surface 29 to which the end lands 33 have been matched. Since manufacturing tolerances can produce changes in the location of the wedging position, it follows that the forces applied to the rollers may not be distributed over the width of each land 33 as uniformly as might be desired. Therefore, it is preferred that, as shown in FIG. 6, the cam surface have a pyramidal shape which presents to each roller 16 a planar cam face 35, and that the rollers have cylindrical end lands 36. This design insures line or surface contact between the rollers and the cam surface regardless of slight variations in the angle of inclination of the cam surface and in the longitudinal position of the plane of contact between the rollers and the cam surface. As a result, more uniform distribution of the wedging forces on the rollers can be realized.
While the sequential release scheme for reducing the actuating pressure required to unlock the wedging roller type of lock is effective, a better approach to this problem is depicted in FIG. 7. This embodiment employs a smaller number of rollers 16d, and all of these are located at one side of the piston rod 17d so that the wedging forces applied to the rod are radially unbalanced. At the opposite side of the rod 17d, the actuating member 25d is cut away to permit insertion of a semicylindrical friction shoe 37 which is carried by the stationary surrounding structure and is adapted to mate with the rod 17d. The shoe 37 is made of a suitable friction material, such as rubber or cast iron. When this lock is applied, the wedging forces applied to rod 17d by the rollers 16d shift the rod laterally into engagement with the shoe 37. Since the coefficient of friction at the rod-shoe interface is much higher than the corresponding coefficient at the roller-rod interface, it
should be evident that the wedging force acting on each roller will be materially smaller than in the case of the other wedging roller embodiments. As a result, the pressure required to move the rollers out of wedging position will be correspondingly lower. Of course, if a further reduction in pressure is desired, these rollers 16d may also be released in sequence. It also is important to note that since the rod-shoe interface has a much greater area than the combined areas of the roller-rod interfaces in FIGS. 3-6, the FIG. 7 version of the lock mechanism affords much greater insurance against unintentional release of the lock under impact conditions.
1. Lock mechanism (eg 11) for a reciprocating element (17) comprising a casing containing said element and a. a lock (16) movable between a locking position in which it prevents motion of said element (17) in one direction of movement and an unlock position in which it permits substantially free motion of the element in either direction;
b. means (222) biasing the lock toward locking position;
c. a detent device (26) associated with the lock and adapted to yieldingly hold it in each of its two positions;
d. a fluid pressure unlock motor (24) arranged to overpower the detent device and shift the lock to unlocking position; and
e. a fluid pressure lock motor (23) arranged to overpower the detent device and allow the biasing means to move the lock to locking position.
2. Lock mechanism (11) as defined in claim 1 in which the biasing means is a spring means (22) reacting between the lock (16) and the casing.
3. Lock mechanism (1 l) as defined in claim 2 in which a. the lock and unlock motors (23, 24) act in opposition to each other on an actuating member (25) arranged to shift the lock (16) to unlocking position; and
b. the detent device is a Belleville washer having inner and outer peripheral portions which are held captive in said member and casing. I
4. Lock mechanism (e.g. 11a) defined in claim 1 in which a. the lock and unlock motors (23a, 24a) act in opposition to each other on an actuating member (250) arranged to shift the lock (16a) to unlocking position; and
b. the biasing means is a spring means (22a) reacting between said member (25a) and the lock and urging the latter to follow movement of the member under the action of the lock motor (23a).
5. Lock mechanism (11a) as defined in claim 4 in which the detent device is a spring biased ball detent (260) comprising cooperating portions carried by the casing and said member (25a).
6. Lock mechanism (e.g. 11) as defined in claim 1 which includes a manually operable mechanical actuator (27) for moving the lock (16) from its locking to its unlocking position.
7. Lock mechanism (e.g. 11b) as defined in claim 1 in which said lock comprises a. a cam surface (29) spaced radially from the element (17b) and defining therewith a space (30) which tapers in the longitudinal direction; and
b. a circumferential series of rollers (16b) positioned within said space and adapted to be moved into and out of wedging relation between the cam surface (29) and said element, 1
c. the rollers (16b) being held captive in positions wherein their axes are transverse to the axis of said element (171:)
- by an actuator (25b) upon which said motors (23b, 24b) act in opposition to each other, but having some freedom to move longitudinally relative to the actuator, and
d. each roller (16b) having a central portion (32) shaped to have line contact with said element, and end portions (33) shaped to have line contact with the cam surface 8. l.oc k mechanism (e.g. 11b) as defined in claim 7 in which the actuator (25b) is adapted to move at least some of the rollers (16b) out of wedging relation in sequence.
9. Lock mechanism (e.g. 11b) as defined in claim 7 in which said biasing means (22b) is an elastic element interposed between the rollers (16b) and a portion of the actuator (25b) and urging the rollers in the direction of the narrow end of said space (30).
10. Lock mechanism (11b) as defined in claim 7 in which a. the cam surface (29) is a conical surface coaxial with said element (17b); and
b. the end portions (33) of the rollers (16b) are curved to fit the conical surface at a point intermediate its ends.
11. Lock mechanism (l'lb) as defined in claim 10 in which said series of rollers (16b) surrounds said element (17b), whereby the radial forces imposed on the element by the rollers are balanced.
12. Lock mechanism (e.g. 110) as defined in claim 7 in which a. the cam surface comprises inclined plane surfaces (35);
b. the end portions (36) of the rollers (16c) are cylindrical.
13. Lock mechanism (11c) as defined in claim 12 in which said'series of rollers (16c) surrounds said element (17c), whereby the radial forces imposed on the element by the rollers are balanced.
14. Lock mechanism (11d) as defined in claim 7 in which the lock also includes a stationary friction shoe (37) adapted to have surface engagement with said element (17d) and located at the opposite side of said element from the rollers (16d), whereby the wedging action of the rollers forces the element into contact with the shoe.
15. Lock mechanism (e.g. 11b) as defined in claim 7 in which a. said series of rollers (16b) surrounds said element (17b);
and b. the biasing means (22b) is an elastic O-ring encircling said element (17b) and reacting between the rollers (16b) and a portion of said actuator (25b).
mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N 3.536.138 Dated June 22 171 lnventofls) Thomas I. Enqle It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Claim 1, line 8 for "222" ree --T.".L
Signed and sealed this 2nd day of November 1971.
EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents