This application is related to co-pending U.S. Ser. No. 10/873,958 entitled “Mechanical Release Of Release Holding Mechanism For Hand Brake”, filed with the U.S. Patent Office on Nov. 17, 2005. Said application being assigned to the assignees of the present invention and disclosure of this co-pending application is hereby incorporated by reference thereto.
The present invention relates, in general, to hand brake assemblies for use on railway type vehicles and, more particularly, this invention relates to a hand brake assembly equipped with a quick release mechanism.
Railway car hand brake mechanisms are well known in the railway art. They usually include a relatively large, rotatable hand wheel disposed in a vertical plane and mounted on a shaft which, through a gear train, can rotate a chain drum to wind up a chain that is secured at its end remote from the chain drum to the brake rigging of the railway car. As the hand wheel is rotated in one direction, the brakes are applied and rotation of the hand wheel shaft in the opposite direction is prevented by a pawl which engages a detent wheel on the hand wheel shaft.
These hand brake mechanisms provide a clutch mechanism for facilitating gradual release of the brake. When a hand wheel is rotated clockwise (as viewed from the front of the unit), such rotation is transmitted directly through a drive shaft, a pinion, a gear, and a winding drum to take up slack of a chain connected to the brake rigging. When resistance is offered by the chain to further rotation of the hand wheel, such resistance, acting back through the drum, the gear, and pinion, causes a nut to be advanced on a threaded portion of the drive shaft to move against a ratchet member which is clamped between respective friction surfaces on the nut and on the drive shaft, thus causing the drive shaft, ratchet, and the nut to rotate as a unit. A pawl prevents rotation of the ratchet in the opposite direction. The hand wheel torque is increased until a state of static equilibrium is reached, or at the point at which the brakes are fully applied, whereupon rotation of the hand wheel is terminated, and the clamped ratchet, by means of the holding pawl, prevents the chain from unwinding.
The clutch mechanism also provides for quick release of the brakes by operating a release handle which effects disengagement of the normally engaged clutch and thereby allows free rotation of the pinion and gear to release the chain load while the nut and ratchet are held stationary by the holding pawl. The brakes may be released by disengaging the pawl from the detent wheel but this causes rapid rotation of the hand wheel and the gears of the gear train. To avoid rapid rotation of the hand wheel, hand brake mechanisms have been devised which are known as “quick release” mechanisms. U.S. Pat. No. 4,368,648 titled “Hand Brake for Railroad Car” teaches such a hand brake having a quick release mechanism. Such quick release mechanism includes a releasable connecting means between the hand wheel shaft and the gear train. When the connecting means is released, the gears of the gear train rotate rapidly, without constraint by the pawl and detent wheel, but the hand wheel remains stationary. The teachings of U.S. Pat. No. 4,368,648 are hereby incorporated into the present application by reference thereto.
It has been found that when a hand brake is released, either by mechanical or pneumatic means, such releasable connecting means between the hand wheel shaft and the gear train do not remain in released position due to the vibration, or other unknown energy generated during train operation. As a result the brakes may be applied unintentionally during railway vehicle motion when the chain of the hand brake does not have enough slack to overcome partial release.
A hand wheel in a handbrake mechanism for a railway car is used to rotate a gear wheel to apply the brakes. Such handbrake having a housing with a back wall and a front wall, with a chain winding drum and a main gear wheel rotatably mounted on a drum shaft thereon. Such hand wheel having a shaft rotatably mounted on the housing having a bearing section at a first end and a hand wheel receiving section on a second end external to such housing. A ratchet wheel is mounted on a hand wheel shaft and rotatable with such hand wheel shaft intermediate the first and second ends thereof. A holding pawl in such housing cooperates with the ratchet wheel so as to prevent reverse rotation thereof. Additionally, a freely rotatable pinion on the hand wheel shaft engages the main gear wheel. The pinion has a radially extending flange cooperating therewith. A quick release mechanism cooperates with the holding pawl to allow reverse rotation of the ratchet wheel for releasing the chain. The hand brake further includes a leaf spring means to substantially engage release lever arm during hand brake application. When the hand brake is released, the release shaft rotates, radially moving the lever arm into engagement with the leaf spring which is attached to the inside of the housing. When the release shaft reaches full release, the load of the leaf spring holds the release shaft in this position until it is mechanically rotated out of position.
It is therefore one of the primary objects of the present invention to provide a hand brake which provides a means to substantially maintain the hand brake in the released position.
It is a further object of the present invention to provide a hand brake which prevents unintentional application of the braking apparatus during the rail car motion around a curve.
It is another object of the present invention to provide a hand brake which prevents wheel sliding on the rail when the rail car is moving at a substantially high speed due to unintentional brake application.
It is still a further object of the present invention to provide a hand brake which provides a more reliable operation.
It is an additional object of the present invention to provide a hand brake having means to substantially maintain the hand brake in the released position which is easily convertible for use with the presently disclosed automatic activation hand brake.
Although a number of objects and advantages of the present invention have been described in some detail above, various additional objects and advantages of the hand brake mechanism of the present invention will become more readily apparent to those persons who are skilled in the art from the following more detailed description of the invention, particularly when such detailed description of the invention is taken in conjunction with both the attached drawing figures and with the appended claims.
The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
Prior to proceeding to the more detailed description of the various embodiments of the present invention, for the sake of clarity and understanding of such invention, it should be noted that identical components having identical functions have been identified with identical reference numerals throughout each of the figures illustrated herein.
A hand brake, generally designated 10, for railroad cars embodying the invention, as shown in
Drive shaft 24 has secured thereon for rotation therewith, at the end adjacent bearing 28, a pinion 30 which engages a gear 32 for rotating a chain drum 34 journaled for rotation in bearings 36 and 38 secured on front plate 16 and back plate 18, respectively, in the lower portion of housing 14. Chain drum 34 engages alternate links of a chain 37 for taking-up the chain.
Also disposed in the upper portion of housing 14 and associated with the driving mechanism, is a clutch and quick release mechanism, generally designated 40, which may best be seen in
An internally splined annular clutch collar 48 is provided with an annular flange 50 and concentrically surrounds the drive shaft 24. The collar 48 engages with an externally splined nut, generally designated 52, attached to threaded portion 25 of such shaft 24. Nut 52 includes a flange 54 with an annular friction surface 56 for making abutting contact with one side of a ratchet wheel 58, the other side of the ratchet wheel 58 being abuttable with a friction surface 57 of a friction plate 59 concentrically secured to shaft 24 adjacent bearing 26.
A clutch and quick release mechanism 40 further comprises a release lever, generally designated 70, best seen in
A force receiving tab portion 86 cooperates with the force transmitting portion 98 of holding pawl 90 and is engaged by the force transmitting tab portion 98 during a brake application cycle. At least one detent retaining means 100, engages detent portion 82 of release lever 70 with the brake in the released and hold condition. In the presently preferred embodiment such at least one detent means 100 is a well known leaf spring, shown in
Alternatively the detent means 100 can be a mechanical, pneumatic, hydraulic or electrical detent means mounted internally or externally of the hand brake housing 14. For example, detent means 100 can comprise a cylinder having a detent portion disposed at the end of the cylinder rod and receiving a fluid pressure signal to extend such rod in order to positively retain the release lever 70 and receiving yet another fluid pressure signal to retract the rod at the beginning of the brake application cycle. Alternatively, the cylinder can be an electrical solenoid having similar interfaces.
Additionally, the leaf spring 100 can be attached to the lever arm 80 and engage a member disposed in a predetermined position within housing 14.
At least one spring means 130 engages release lever portion 78 attached to the pin portion 76 at one end and engages a mounting hook 128 attached to housing 14 at the distal end. In the presently preferred embodiment such at least one spring means 130 is a simple compression spring.
In operation, in order to apply the brakes, hand wheel 22 is rotated counter-clockwise, as viewed in
For providing a gradual release of the brakes, hand wheel 22 is turned counterclockwise slightly to partially loosen nut 52 and thereby reduce the clamping force on ratchet member 58, which is restrained from rotation by holding pawl 90. The initial counterclockwise rotation of hand wheel 22 effects a corresponding rotation of pinion 30 and gear 32, thereby easing the tension on chain 37. Continued counterclockwise rotation of hand wheel 22 effects complete release of the load on chain 37 with gear 32 continuing to rotate until winding drum 35 has taken up all chain slack, that is, the amount of chain that had been taken up during the brake-applying phase of operation. When all chain slack has been taken up, further rotation of gear 32, pinion 30 and nut 52 is terminated with the brakes fully released. Clockwise rotation of hand wheel 22 is limited by a drive shaft pin 60 which projects into a slot 61 formed in nut 52.
A quick release of the brake application is caused by rotating lever 122 of the release handle 120 (which is normally in an applied position) in a counter-clockwise direction, as viewed in
Subsequent engagement of pin portion 76 with the second fork portion 49 of movable cam 44, causes clockwise rotation of such movable cam 44. As noted supra, stationary cam 42 and the movable cam 44 are provided with complementary fast-pitch threads 43, so that as movable cam 44 rotates clockwise, it moves axially outwardly of stationary cam 42, in an upwardly direction as viewed in
Thus, upward axial movement of movable cam 44 causes an axial disengagement of external splines 64 formed on clutch collar 48 from internal splines 65 formed on pinion 30, thereby allowing the pinion 30 and gear 32 to rotate freely for releasing the load on chain 37, while drive shaft 24, nut 52, collar 48, and ratchet 58 are all held stationary by holding pawl 90.
Lever arm portion 80 of the release lever rotates counter-clockwise subsequently with the rotation of release handle 120 with first round portion 84 engaging ramp portion 102 of leaf spring 100 for gradual engagement with leaf spring 120. Upon substantially reaching the end of the rotational travel, detent portion 82, having a predetermined profile substantially equal to predetermined profile of the retaining portion 104 of said leaf spring 100, engages retaining portion 104 for substantial retention of the release lever 70 in the release and hold position. Such retention of release lever 70 prevents its rotating in a clockwise direction toward the applied position and further prevents rotation of the gear 32 and, more particularly, prevents partial release of the chain 37 so that motion of the railway vehicle around the curve will not cause unintended brake application due to the partially released chain 37 not having enough slack to withstand railway vehicle motion.
When the brakes are fully released, the operator allows release handle 120 to return by gravity to the “applied” position from which the brakes may again be applied if desired.
Thus, the present invention has been described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same. It will be understood that variations, modifications, equivalents and substitutions for components of the specifically described embodiments of the invention may be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.
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Number | Date | Country | |
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20050279184 A1 | Dec 2005 | US |