Slack adjuster for railway vehicle brake rigging

The present invention teaches a double-acting compression actuatable slack adjuster to adjust the slack in the brake rigging of a railway vehicle which includes a pair of elongated members movable with respect to each other in a longitudinal direction. A positioning device carrying a pair of opposed abutting surfaces is threadedly engaged with a threaded portion of the elongated rod. Pair of opposite facing abutment surfaces are positioned within the hollow housing. A first urging device is positioned to urge the positioning device into a disengaged position. A second urging device overcomes the force of the first urging device and urges an abutting surface on the positioning device into engagement with an adjacent abutment surface. A first overtravel control device is provided which is activated by a trigger device. A second overtravel control device is provided to prevent jamming condition of the positioning device with one of the abutment surfaces when the elongated rod is fully extended.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is closely related to U.S. Pat. No. 4,662,485 which is assigned to the assignee of the present invention. The disclosure of U.S. Pat. No. 4,662,485 is hereby incorporated by reference thereto.

FIELD OF THE INVENTION

The present invention relates, in general, to a double-acting compression actuable slack adjuster assembly which automatically adjusts the slack in the brake rigging of a railway vehicle and, more particularly, this invention relates to a double-acting compression actuable slack adjuster assembly which includes an overtravel control mechanism preventing irreversible lock-up of the slack adjuster being incorrectly installed and adjusted.

BACKGROUND OF THE INVENTION

As is generally well known, slack adjuster assemblies have been employed to automatically adjust the slack in the brake rigging of a railway vehicle. A particular slack adjuster of a double-acting compression type has been manufactured by the assignee of the present invention and employed in a wide variety of railway applications. Such slack adjuster includes an elongated hollow housing member restrained against rotation and pivotally connectable at a first end thereof to such brake rigging. An elongated rod member, which is restrained against rotation and pivotally connectable at a first end thereof to such brake rigging, is also provided and has at least a threaded portion adjacent a second end thereof. The threaded portion of the rod member extends into and is reciprocally movable within the housing through a second end of the housing. A positioning means, such as a cone lock nut, movable between respective first abutting engagement, disengagement, and second abutting engagement positions is threadably engaged with the threaded portion of the rod member intermediate said ends thereof. The cone lock nut rotates about the threaded portion of the rod member when in the disengaged position thereby changing the length of the slack adjuster assembly by changing the relative longitudinal position between the housing and the rod member. A pair of opposite facing abutment surfaces positioned within a portion of the housing and a pair of opposed abutting surfaces carried by the cone lock nut for engaging respective adjacent abutment surfaces to resist rotation of the cone lock nut about the rod member when the cone lock nut is in one of the respective abutting engagement positions thereby retarding the change in relative longitudinal position between the housing and the rod member are provided. A first urging means is positioned between the cone lock nut and an abutment surface carried by the rod member for urging the cone lock nut into the disengaged position. A second urging means is positioned between the first end of the housing and the cone lock nut for overcoming a force applied by the first urging means and for urging the cone lock nut into the first abutting relationship position. An overtravel control means is positioned to reciprocally move in a longitudinal direction adjacent the first end of the housing and is engageable with the second urging means for reducing the force applied by the second urging means to less than the force applied by the first urging means, thereby allowing the cone lock nut to move to the disengaged position. An overtravel control actuating means is positioned to engage the overtravel control means for actuating the overtravel control means in response to the travel distance of a brake cylinder piston connected to such brake rigging. When the slack adjuster is triggered, the cone lock nut rotates with the sufficient speed and force that the abutting surface carried thereon frictionally engages against the abutment surface of the housing in second abutting relationship position. Such abutment surface is oriented toward the first end of the housing. In normal operation of the slack adjuster when this condition occurs, the second urging means is compressed slightly by the by the higher overtravel spring force and the cone lock nut moves from the second abutting relationship position. However, it has been found that when the slack adjuster is triggered and the elongated rod is allowed to fully extend due to improper adjustment during installation, the speed and inertia of the rotating cone lock nut is sufficient to exert greater than desirable force during contact with the abutment surface of the housing in the second abutting relationship position. Such greater than desirable contact force causes jamming condition, due to friction and, more importantly, causes operation of the slack adjuster to cease. Prior to the present invention, the jamming condition can be only corrected by manually rotating the portion of the housing disposed adjacent the first end thereof.

Therefore, there is a need for an improved slack adjuster which includes an overtravel control mechanism preventing irreversible lock-up of the slack adjuster being incorrectly installed and adjusted.

SUMMARY OF THE INVENTION

This invention provides a double-acting compression actuable slack adjuster to adjust the slack in a railway vehicle brake rigging. The slack adjuster assembly includes an elongated hollow housing member restrained against rotation and pivotally connectable at a first end thereof to such brake rigging. An elongated rod member, restrained against rotation and pivotally connectable at a first end thereof to such brake rigging, is also provided and has at least a threaded portion adjacent a second end thereof. The threaded portion of the rod member extends into and is reciprocally movable within the housing through a second end of the housing. A positioning means movable between respective first abutting engagement, disengagement, and second abutting engagement positions is threadably engaged with the threaded portion of the rod member intermediate the ends thereof. The positioning means rotates about the threaded portion of the rod member when in the disengaged position thereby changing the length of the slack adjuster assembly by changing the relative longitudinal position between the housing and the rod member. A pair of opposite facing abutment surfaces positioned within a portion of the housing and a pair of opposed abutting surfaces carried by the positioning means for engaging respective adjacent abutment surfaces to resist rotation of the positioning means about the rod member when the positioning means is in one of the respective abutting engagement positions thereby retarding the change in relative longitudinal position between the housing and the rod member are provided. A first urging means is positioned between the positioning means and an abutment surface carried by the rod member for urging the positioning means into the disengaged position. A second urging means is positioned between the first end of the housing and the positioning means for overcoming a force applied by the first urging means and for urging the positioning means into the first abutting relationship position. A first overtravel control means is positioned to reciprocally move in a longitudinal direction adjacent the first end of the housing and is engageable with the second urging means for reducing the force applied by the second urging means to less than the force applied by the first urging means, thereby allowing the positioning means to move to the disengaged position. An overtravel control actuating means is positioned to engage the first overtravel control means for actuating the first overtravel control means in response to the travel distance of a brake force applying member connected to such brake rigging. A second overtravel control means is positioned in close proximity to the second end of the elongated hollow cylindrical housing member for reducing a frictional force generated during engagement of the respective abutment and abutting surfaces when the positioning means is in the second abutting engagement position and for preventing a jamming condition between the respective abutment and abutting surfaces when the elongated rod member is fully extended

OBJECTS OF THE INVENTION

It is, therefore, one of the primary objects of the present invention to provide a double-acting compression actuatable slack adjuster assembly to automatically adjust the slack occurring in the brake rigging of a railway vehicle and which can function as a force-transmitting member in such brake rigging.

Another object of the present invention is to provide a double-acting compression actuatable slack adjuster assembly to adjust the slack in a railway vehicle brake rigging which includes an overtravel control mechanism preventing irreversible lock-up of the slack adjuster being incorrectly installed and adjusted.

Yet another object of the present invention is to provide a double-acting compression actuatable slack adjuster assembly to adjust the slack in a railway vehicle brake rigging which includes an overtravel control mechanism that can be triggered in a number of ways from a measured travel distance of the brake cylinder piston rod.

A further object of the present invention is to provide a double-acting compression actuatable slack adjuster assembly which can be installed in the brake rigging of a railway vehicle in either one of two positions thereby permitting not only greater flexibility but also reliability in placement of the trigger mechanism which responds to measured brake cylinder piston rod travel distance.

An additional object of the present invention is to provide a double-acting compression actuatable slack adjuster assembly in which all of the force urging means are always maintained in compression.

In addition to the several objects and advantages of the present invention which have been described with some degree of specificity above, various other objects and advantages of the invention will become more readily apparent to those persons who are skilled in the relevant art, particularly, when such description is taken in conjunction with the attached drawing Figures and with the appended claims.

BRIEF DESCRIPTION OF THE VARIOUS EMBODIMENTS OF THE INVENTION

The structure and use of the present invention will be illustrated in combination with a double-acting compression actuatable slack adjuster assembly, generally designated as10, which is taught in the U.S. Pat. No. 4,662,485 assigned to the assignee of the present invention. The disclosure of U.S. Pat. No. 4,662,485 is incorporated into this document by reference thereto. The double-acting compression actuatable slack adjuster assembly10is installed on a truck-mounted brake rigging, generally designated as2, of a railway vehicle (not shown). The truck-mounted brake rigging illustrated inFIG. 1is of a type as manufactured by the assignee of the present invention under TMX® brand.

Now referring toFIGS. 2-8, the double-acting compression actuatable slack adjuster assembly10includes an elongated hollow housing member, generally designated12. The housing member12is restrained against rotation and is pivotally connectable at a first end14thereof to the brake rigging2of the railway vehicle (not shown) by a first eye portion16having an aperture18formed therethrough.

An elongated rod member, generally designated as20, is positioned for reciprocal movement within the housing member12through a wall23of the second end22of housing member12. Rod member20is restrained against rotation and is pivotally connected at a first end24thereof to the railway vehicle brake rigging2by a rear eye portion26having an aperture28formed therethrough or by a rear portion26′ having a pair of spaced apart apertures28formed therethrough, as best shown inFIG. 7, for accommodating different brake rigging construction corresponding to a capacity of the railway vehicle truck (not shown). The rod member20has a threaded portion30adjacent a second end32thereof. Threaded portion30extends from the second end32of rod member20for a predetermined length and is contained within the housing member12. Also adjacent the second end32of rod member20is a means, such as a collet33, to maintain the rod member20in substantial coaxial alignment with the housing member12. Collet33is held in place by a retainer ring35.

A positioning means, generally designated as34, is threadedly engaged with the threaded portion30of the rod member20intermediate the ends thereof. The positioning means34is movable between respective first abutting engagement, disengagement and second abutting engagement positions. The positioning means34rotates about the threaded portion30of rod member20when in the disengaged position and thereby changes the length of the slack adjuster assembly10by changing the relative longitudinal positions between the housing member12and the rod member20.

A pair of opposite facing abutment surfaces36and38are positioned within a portion of the housing member12intermediate the ends thereof for engagement by a pair of opposed abutting surfaces40and42carried by the positioning means34. Abutment surface36engages abutting surface40in the above-mentioned first abutting engagement position and abutment surface38engages abutting surface42in the second abutting engagement position. During engagement of respective adjacent abutment surfaces, i.e.,36with40or38with42, rotation of the positioning means34about the threaded portion30of rod member20is resisted and thereby retards the change in relative longitudinal position between the housing member12and the rod member20.

A first urging means, preferably a spring44, is positioned between the positioning means34and an abutment surface46, carried by the rod member20, to urge the positioning means34into the above-mentioned disengaged position. It should be understood by those skilled in the art that the first urging means could be a fluid cylinder, such as a pneumatic or hydraulic cylinder (not shown).

A second urging means, preferably a spring48, is positioned between an abutment surface50near the first end14of the housing member12and the positioning means34. As mentioned above, the second urging means could also be a fluid-operated cylinder (not shown). Typically, the second spring48is stronger than the first spring44so as to overcome the force applied by the first spring44and therefore urge the positioning means34to the left, as shown in the drawing, with the consequent engagement of abutment surfaces36and40which is the first abutting relationship position.

A first overtravel control mechanism, generally designated as52, is positioned to reciprocally move in a longitudinal direction adjacent the first end14of the housing member12. Overtravel control means52is engageable with the second spring48in order to reduce the force being applied to such second spring48to an amount which is less than the force being applied by the first spring44. This will allow the positioning means34to move to the disengaged position.

An overtravel actuating means, generally designated as100, is positioned to engage the overtravel control means52in order to activate the overtravel control means52in response to the travel distance of a force applying member5of a brake actuator4of the brake rigging2. In the presently preferred embodiment of the invention, the overtravel actuating means54includes a lever102which is pivotally connected to a bifurcated portion104of the housing member12. Accordingly, an aperture106is formed through each portion104and has axis thereof which is disposed generally vertically when the slack adjuster10is installed in the brake rigging2. The aperture106is aligned with a complimentary aperture108formed through the first end of the lever102. A simple pin110and a cutter pin112, inserted through an aperture (not shown) formed in one end of the pin110, are then used to achieve such pivotal connection. The second end of the lever102extends past the elongated housing member12and has an aperture114which is formed therein and which has axis thereof disposed generally horizontally when the slack adjuster10is installed in the brake rigging2. The aperture114is sized to receive a threaded portion118of the control member116which has a bifurcated portion117axially aligned with the threaded portion118. A pair of nuts130and132are used to attach the second end of the lever102to the control member116. The control member116has an aperture134formed through bifurcated portion117for attachment to the force transmitting linkage6of the brake rigging2. An abutment portion105is formed intermediate the ends of the lever102for engagement with the overtravel control means52. A reference point is established during movement of the force applying member5of the brake actuator4and compression of the spring is triggered by the lever102when this reference point is exceeded.

In the presently preferred embodiment of the invention, the abutment surface46is carried by a first spring seat56secured to rod member20in a permanent fashion such as by welding, and the first spring44is caged between the first spring seat56and the positioning means34. The second spring48is caged between the abutment surface50located at the first end14of the housing member12, and an abutment surface58closely adjacent one end60of the overtravel control means52. The abutment surface58is preferably carried by a second spring seat62. The second spring seat62engages a first ledge portion64(FIG. 5) which extends outwardly from the outer periphery of the overtravel control means52closely adjacent the end60on an opposed side66of spring seat62.

The load rating of the second spring48is greater than the load rating of the first spring44and is preferably in the range of at least between about 2.0 and 3.0 times greater. On the other hand, the free height of the first spring44is greater than the second spring48and preferably it has a free height of at least between about 1.5 and 1.8 times greater free height.

As shown inFIGS. 3,5and6and in accordance with the present embodiment, the positioning means34is a cone lock nut35. Cone lock nut35includes a recessed area68for receiving the end60of overtravel control means52. Cone lock nut35also has an extended and internally threaded portion70which extends into first spring44adjacent one end. Extended portion70provides a greater threaded portion for cone lock nut35and controls somewhat the speed of rotation of such cone lock nut35.

In the presently preferred practice of the invention, a pair of thrust bearings73and75are placed in contact with a respective side of the cone lock nut35to permit free rotation of such cone lock nut35about the threaded portion of rod member20.

As best shown inFIG. 5, the elongated hollow housing member12includes a first housing portion72which houses a portion of the threaded portion30of the rod member20, the overtravel control means52, and the second spring48. The housing member12also includes a second housing portion74which is removably engaged with first housing portion72. Second housing portion74houses a portion of the rod member20including the remaining portion of the threaded portion30of rod member20and the first spring44. The cone lock nut35is positioned substantially at the juncture of first housing portion72and second housing portion74. The first housing portion72carries one of the opposite facing abutment surfaces38, and the second housing portion74carries the other of the opposite facing abutment surfaces36.

The presently preferred housing member12, shown inFIGS. 2-4, includes a first housing portion76which houses a portion of the threaded portion30of rod member20, the overtravel control means52and the second spring48. Housing member12also includes a second housing portion78which houses a portion of the rod member20including the remaining portion of the threaded portion30and the first spring44. A third housing portion80couples the first housing portion76with the second housing portion78. In the housing member12arrangement, shown inFIGS. 2-4, the first housing portion76carries one of the pair of opposite facing abutment surfaces38and the third housing portion80carries the other of the opposite facing abutment surfaces36. The third housing portion80includes a second ledge portion82extending inwardly and facing the second housing portion78.

A sleeve member84having at least one longitudinal guide slot86formed therein is tightly positioned between the second ledge portion82and one end88of the second housing portion78. A third spring seat90is positioned for reciprocal movement intermediate one end92of the first spring44and the thrust bearing73adjacent cone lock nut35. The third spring seat90includes at least one lug portion94which extends in an outwardly direction from the outer periphery of the spring seat90to cooperate with the guide slot86to prevent windup of the first spring44.

In all of the presently preferred embodiments of the invention, the housing member12is cylindrical in shape. An elongated hollow cylindrical portion96is removably engaged intermediate the end14and first housing portion76or72which allows reciprocal movement of the overtravel control means52. There is at least one opening through the wall of the cylindrical portion96to permit the actuating means102to engage the overtravel control means. The eye portion16is formed as a single-piece casting with the cylindrical portion96. Eye portion16allowing such pivotal connection and at the same time restraining the first end14against rotation.

The overtravel control means52includes an elongated hollow cylindrical portion98having the first ledge portion64at one end60positioned between the threaded portion30of the rod member20and the second spring48. A generally solid portion99is secured to the overtravel control cylindrical portion98and is reciprocally movable within the cylindrical portion96connected to end14.

In operation, when it is required to apply brakes, the brake actuator4of the brake rigging2is energized enabling its force applying member5to extend and causing the brake beams7,8to move in a direction “X”. At predetermined travel of the force applying member5, as the brake shoes (not shown) contact the wheel (not shown), the actuating lever102of the overtravel actuating means100which is connected to the force transmitting linkage6of the brake rigging2is activated and “triggers” the slack adjuster10by moving the overtravel control means52in a direction to compress spring48. Any further travel of the force applying member5causes a compression force through the elongated rod member20, at the same time compressing spring48, thereby allowing spring44to move the cone lock nut35from the abutment surface36and further allowing the abutting surface42carried thereon to frictionally engage abutment surface38of housing12and lock-up as a solid rod in compression, causing no changes. In normal operation of the slack adjuster10when this condition occurs, the second spring48is compressed slightly by the by the higher overtravel spring force and the cone lock nut35moves from the second abutting relationship position when the brake application is discontinued and when the brake actuator4is deenergized. However, it has been found that when the slack adjuster10is triggered and the elongated rod member20is allowed to fully extend due to improper adjustment during installation or lack of connection of the second end22to the brake rigging2, the speed and inertia of the rotating cone lock nut35is sufficient to exert greater than desirable force during frictional contact between abutting surface42and the abutment surface38of the housing12in the second abutting relationship position aided by the locking effect of the internally threaded portion70of the cone lock nut35against the threaded portion30of the rod member20. Such greater than desirable contact force causes jamming condition, due to friction and, more importantly, causes operation of the slack adjuster10to cease. Prior to the present invention, the jamming condition can be only corrected by manually rotating the second end22of the slack adjuster10.

To prevent the jamming condition between respective abutting surface42and abutment surface38, the slack adjuster10includes a second overtravel control means, generally designated as120, which is positioned in close proximity to the second end22of the elongated hollow cylindrical housing member12for reducing a frictional force generated during engagement of such abutting surface42and abutment surface38when the cone lock nut35moves into the second abutting position. In the presently preferred embodiment of the invention, the second overtravel means120is at least one resilient member positioned within the elongated hollow cylindrical housing member12and caged between the wall23of the elongated hollow cylindrical housing member12and the first spring seat56. Preferably, as best shown inFIG. 2, such at least one resilient member is an elastomeric disk-like member122having each of a predetermined thickness and a predetermined hardness. The disk-like member122has an aperture124axially formed therein for receiving the elongated rod member20. The presently preferred material of the disk-like member122is thermoplastic elastomer and, more particularly, polyester elastomer such as the one marketed under the trade name “Hytrel” by E.I. Du Pont. If required, such disk-like member122may be secured to the surface126of the first spring seat56, as shown by122′, by way of an adhesive127.

Alternatively, as shown inFIG. 7, the second overtravel means120is at least one coiled spring128positioned within the hollow cylindrical housing member12and caged between the wall23of the elongated hollow cylindrical housing member12and the first spring seat56.

Now, when the elongated rod member20is fully extended, the disk-like member122will compress slightly upon impact with the surface126of the first spring seat56. As the disk-like member122compresses the impact energy is quickly absorbed and is initially stored therewithin, as indicated by reference letter “I” inFIG. 8, thus preventing jamming condition, due to friction, between abutting surface42and abutment surface38. Preferably, the thickness and hardness of the disk-like member122are preselected for specific construction of the slack adjuster to absorb the impact energy just prior to contact between abutting surface42and abutment surface38. After duration of time, the impact energy is released, as indicated by reference letter “R” inFIG. 8, enabling normal operation of the slack adjuster10wherein the first spring44slightly extends the rod member20and the abutting surface42contacts the abutment surface38with the desired friction force preventing jamming condition.

The presently preferred thickness of the disk-like member122for use with the above described slack adjuster10is between about 0.12 inches and about 0.128 inches and the presently preferred hardness is about 40 durometer.

Although the present invention has been shown in terms of employing the slack adjuster10with the truck-mounted brake rigging2ofFIG. 1, it will be apparent to those skilled in the art, that the present invention may be applied to other truck-mounted or car mounted brake riggings.

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.