Air bladder actuator for railroad car retarder

An air bladder actuator for a railroad car retarder utilizes a simplified stroke limiting arrangement that can be used in new actuator construction or applied as a retrofit assembly to an existing air cylinder actuated retarder.

BACKGROUND OF THE INVENTION

The present invention pertains to an air bladder actuated railroad car retarder and, more particularly, to a simplified and low cost internal stroke limiting arrangement for an air bladder cylinder used in the retarder.

Air bladder actuators are well known in the railroad industry and are now commonly used to operate retarders in railroad marshalling yards. One commonly used air bladder is a Firestone AIRSTROKE actuator. The actuator includes a flexible bladder that is secured around the perimeter on opposite ends to a pair of end plates to form an air tight interior. The bladder is inflated and deflated to control its length and stops are used to set the maximum and minimum stroke lengths of the actuator. The stroke limiting arrangement is preferably provided on the interior of the bladder between the end plates.

SUMMARY OF THE INVENTION

In accordance with the present invention, a stroke limiting arrangement is provided on the interior of the bladder that is rugged, yet of low cost. The bladder actuator is capable of use in retrofit applications to replace air cylinders in existing retarders. The retrofit arrangement reuses components of the air cylinder.

DETAILED DESCRIPTION OF THE INVENTION

In retrofitting an air cylinder actuated retarder10of the prior art type shown inFIG. 1, the air cylinder12is removed, but several components are retained, machined as may be necessary, and incorporated into an internal stroke limiting mechanism for an air bladder13(FIG. 3) that replaces the air cylinder12. The air cylinder upper end plate14is cut from the cylinder body15. The upper end plate14includes an integral pivotal clevis mount16which is also retained for use in the retrofit apparatus. The piston rod17of the air cylinder is also retained for reuse, but the piston head18is removed and not reused.

Referring also toFIGS. 4 and 5, the peripheral edge of the upper end plate14is provided with a circular bolt hole pattern20through which bolts extend from the peripheral edge of the air bladder13. The interface between the peripheral edge of the upper end plate and the air bladder13is provided with a suitable seal or sealing material to provide an air-tight interface. An upper mounting ring21is bolted to the lower inside face of the upper end plate14with bolts22inserted through the upper face of the upper end plate14into tapped holes in the upper mounting ring. The upper mounting ring21has a center opening24from which an attached guide rod23extends. As best seen inFIGS. 6 and 7the guide rod is welded at its upper end to the upper mounting ring21. The guide rod23is provided with an axially elongated through slot25to provide a guide and stop function as will be described below. Slot25also vents air to and from the blind bore26in the guide sleeve28described below.

Turning now to the lower end of the stroke control apparatus and referring also toFIGS. 4-6, the piston rod17(no longer acting as such) is provided at its upper end with an axial blind bore26for receipt of the guide rod23. The piston rod17thus becomes a guide sleeve28for axial movement of the guide rod23. The upper end of the guide sleeve28is provided with diametrically opposed holes29for receipt of a cross pin27which guides and, in part, limits the axial movement of the guide rod23within the bore26of the guide sleeve28

A lower mounting ring31is secured to the guide sleeve28formed in the piston rod. The lower end plate32(from the air cylinder12) is bolted to the lower mounting ring31with a circular pattern of bolts33extending upwardly through the end plate32and into tapped holes in the lower mounting ring31. A large diameter cylindrical stop sleeve34is welded or otherwise secured to the upper surface of the lower end plate32on the center axis of the apparatus.

The lower end of the guide sleeve28retains the lower end of the air cylinder piston rod17which is provided with a pair of parallel opposite flats35through which is provided an axially perpendicular bore36for pivotal connection to a suitable clevis or other pivotal mounting arrangement (not shown).

The outer peripheral edge of the lower end plate32is provided with a circular bolt hole pattern37for bolted connection to the lower end of the air bladder13in a manner similar to the upper end described above. The interface, of course, must also provide an air-tight seal. In the arrangement of components described above, the upper end of the stroke control arrangement includes the slotted guide rod23positioned axially in and attached to the upper mounting ring21and thus secured to the upper end plate14. The lower end of the guide and stroke limiting arrangement comprises the guide sleeve28secured to the lower end plate32and lower mounting ring31and a large diameter cylindrical stop sleeve34. The upper and lower portions of the guide arrangement are connected by the cross pin27which can move within the elongated slot25as the air bladder13is pressurized and depressurized to, respectively, extend and retract the air bladder actuator11. More specifically, maximum extension of the actuator by pressurizing the air bladder13is controlled by the cross pin engaging the bottom (lower end) of the guide rod slot25. Retraction of the air bladder13to its compressed state is limited by contact of the upper edge of the stop sleeve34with the underside of the upper end plate14. When this collapsing contact occurs, the cross pin27nests in semi-cylindrical recesses40in the bottom face of the upper mounting ring, but remains spaced slightly from the upper axial end of the slot25. An assembly of the retrofit internal guide and stroke limiting arrangement is shown inFIG. 5without the air bladder13. To reduce friction and facilitate relative axial movement between the guide rod23and the guide sleeve28, a suitable bearing sleeve38is preferably inserted axially into a counterbore41in the blind bore26of the guide sleeve. A manganese bronze/graphite hushing is one suitable type of bearing sleeve38.

InFIG. 8, there is shown an air bladder actuator of the present invention which is newly manufactured, rather than utilizing parts of an air cylinder actuator of the type shown inFIG. 1. In theFIG. 8construction, the upper and lower end plates42and43are of new construction. The upper mounting ring44and the guide rod45are of a unitary construction, machined from a casting or other steel piece. Similarly, the lower mounting ring46and guide sleeve47are also of unitary construction, machined from steel stock or a casting as well. The upper end plate42is bolted directly to the upper mounting ring, as in the previous embodiment. Similarly, the lower end plate43is bolted to the lower mounting ring46that carries the integral guide sleeve47. As in the previously described embodiment, the guide sleeve47carries a bearing sleeve48in a counterbore50.

Otherwise, the air bladder actuator of new construction, shown inFIG. 8, operates identically to the previously described retrofit embodiment.