US2342763A - Reversing valve assembly - Google Patents

Description

Feb. 29. 1944. c. J. SMITH 2,342,763

REVERSING VALVE ASSEMBLY Filed Aug. 6, 1942 29 2g gar $9.1.

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Patented Feb. 29, 1944 REVERSING VALVE ASSEMBLY Clarence J. Smith, Chicago, Ill., assignor to Brake Equipment & Supply (30., Chicago, Ill., a corporation of Illinois Application August 6, 1942, Serial No. 453,877

Claims.

The present invention relates to a reversing piston valve assembly. I

An object of the invention is the provision of means for preventing injury to the ends of the piston valve and particularly to the packing rings adjacent the ends thereof. In many instances over-travel of the piston will cause it to strike the ends of the cylinder, and this constant impact causes the end ring flanges to be hammered down tight upon their respective rings. This objectionable feature is eliminated by the present invention.

Another object is to provide a construction which will permit the piston valve to be easily and quickly removed from the cylinder for repair or replacement.

A further object is the provision of means for effectively connecting the piston valve to its operating rod. Often where a nut and bolt structure is utilized, the nut becomes loose, setting up lost motion between the valve and rod and eventually causing breakage of different elements of the construction. This objectionable feature is also eliminated by the present construction.

With the foregoing and other objects in view, the invention will be more fully described, reference being had to the accompanying drawing, in which:

Figure 1 is a vertical section, showing the reversing piston valve in its uppermost position;

Figure 2 is a view somewhat similar to Figure 1, with the reversing valve near the lower end of its stroke;

Figure 3 is an enlarged detail view of the piston, showing its connection to the reversing valve rod;

Figure 4 is a section taken on the line 4-4 of Figure 3, and

Figure 5 is a section taken on line 5-5 of Figure 1.

Referring now to the drawing and particularly to Figures 1 and 2, there is disclosed a reversing piston valve assembly including a "casing or head ID, a sleeve I I mounted in the casing and comprising the cylinder within which a piston valve I 2 reciprocates. This piston valve is provided with top, bottom, and intermediate piston heads l3, l4 and I5, respectively, for controlling various ports leading to and from the cylinder I l.

The present assembly is particularly adapted for use with steam-driven air compressors as used on railroad locomotives, but only the structure of the reversing piston valve is disclosed, since the compressor construction forms no part of the present invention. Only the ports leading to'and from the cylinder l I and controlled by the heads l3, l4 and I5 are disclosed. In this connection, port or passage It leads to the outer side of the large piston (not shown), while passage ll'leads from the outer side of the large piston. The numeral l8 designates the exhaust passage, while l9 indicates the main steam supply chamber. The piston valve I2 is reciprocated by the usual plate on the steam piston (not shown) which strikes the shoulder 20 on the reversing valve rod 2| to move the reversing piston to its up position shown in Figure 1. Downward movement of, the aforementioned plate strikes the button 22 on the lower end of the rod 20 to move the reversing piston 12 to its lowermost position shown in Figure 2.

During the reciprocation of the piston 12 which usually reverses at about strokes per minute, the rod and valve have to withstand considerable pounding and unless preventative measures are taken, the top and bottomring flanges 23 and 24 are distorted and hammered down tight upon their respective rings 25 and 25. In the present invention, this objectionable feature is eliminated by providing means for preventing the flanges 23 and 24 from directly receiving the impact, if the piston over-travelsand strikes either end wall of the cylinder ll.

Referring to Figure 1, the top end wall of the cylinder comprises a separate valve cap 27. This cap is externally threaded to engage threads formed in the top of the opening in the casing or head I0 within which the sleeve or cylinder It is positioned. As clearly shown in Figures 1 and 2, the cap bears upon the top end of the cylinder l i i" and forces it against the shoulder portion 28 of the casing. However, if desired, the cap may clear the end of the cylinder, the latter in this instance being turned to a press fit in the casing Ill. The inner face of the cap 27 is provided with a centrally disposed boss 29 which is surrounded by an annular groove or recess 30. The boss 29 is of such a diameter thatit will contact the upper end of the piston l2 inwardly of the ring flange 23. Furthermore, the groove or recess 30 is designed to register with the peripheral edge or ring flange 23 of the upper end of the piston, as clearly shown in Figure 1. Thus, if th piston over-travels on itsupward stroke, only the central portion thereof will engage the boss 29 and the top ring flange 23 will register with the annular recess 30. In other words, the impact will be taken by the interior or centrally disposed portion of the upper end of the piston and not by the ring flange 23. Therefore, thefiange 23 will not be distorted or hammered downwardly into its ring 25.

Means are also provided to prevent the distortion or hammering of the lower ring flange 24 into its ring 25. It will be observed that the body of the cylinder or sleeve H is reduced adjacent its lower end by reason of the shoulder 28 and that the extreme end portion thereof rests upon an annular shoulder 3! of the casing or head Ill. An annular opening 32 is also formed in the lower portion of the head inwardly of the shoulder 3| to permit movement of the reversing valve rod 2|. The diameter .of the opening 32 is somewhat larger than that of the rod 2| but is less than that of the piston head l4. In fact, the lower ring flange 24 is located exteriorly of the opening 32. A boss 33 is formed on the lower end of the piston 12 and extends to a point adjacent the inner end of the flange 24, The relative diameters of the opening 32 and boss 33 is such that any over-travel of the piston on its downward movement will result in the boss 33 engaging or contacting the shoulder 3| adjacent its inner annular edge. Thus, similarly to the arrangement at the upper end of the piston, any impact will be taken by the boss 33 interiorly oi the peripheral edge or flange 24, and thereby prevent distortion or hammering of this flange into its ring 26. As a result of the formation of the bosses 29 and 33, injury to the piston flanges and packing rings is prevented, in the event that the piston should over-travel during its operation in the cylinder l I.

Referring to Figure 1, it will be observed that the piston is provided with a centrally disposed passage 34 extending therethrough and normally permitting flow of fluid from one end of the piston to the other. It will be observed that the 7 piston is of relatively small diameter, and that the piston rod does not extend therethrough, so that the opening 34 can be disposed centrally of the piston, as distinguished from that type in which. the piston rod extends through the center of the piston and the fluid passage is laterally offset from the longitudinal axis of the piston, This is of distinct advantage where the compressor is converted from the old slide valve type to the piston type and it becomes essential or desirable to have a small piston. The upper end of this passage is slightly enlarged and tapped to provide a threaded section 35. The threaded area is formed so that a standard-sized bolt (not shown) may be easily screwed into the end of the piston to permit removal of the same for repair or replacement. With this construction, and assuming that it is desired to remove the piston it, it is merely necessary to unscrew the cap 21', crew a standard-sized bolt into the threaded section 35, and pull out the piston from the cylinder H. This arrangement eliminates the necessity of removing the piston by means of a pair of pliers or some other special puller.

The piston rod 2| is subjected to considerable pounding, and should be made of a higher grade of material than is necessary for the piston, so that it is desirable to form the piston and piston rod separately. It is essential, however, that the piston and rod be very securely joined, in order that the shock of operation will not result in separating them. In order to prevent loosening of the rod 21 with respect to the piston H and thus setting up lost motion between these members which would eventually cause breakage of some ofthe parts, the present invention is provided with means for efiectively connecting these members to prevent accidental loosening or unthreading of the rod 2| from the lower end of the piston. Referring particularly to Figures 1 and 3, it will be observed that the lower end of the piston i2 is provided with a reduced section 36 which, on the downward stroke of the piston will enter the aperture 32, there being sufiicient clearance between the wall of the reduced section 33 to permit this, while at the same time the boss 33 on the lower end of the piston will engage the annular shoulder 3| of the casing of head If! and guard against hammering the ring flange 24, thus preventing ring binding. This section is internally threaded and receives the reduced externally threaded end portion 3'! of the rod 2! which closes the lower end'of the fluid pressure passage 34 disposed centrally of the piston. In order to maintain communication with that through passage 34, I provide the reduced section 33 of the piston with the laterally disposed passages 42 disposed just below the lower piston head, as shown in Figures I, 3, and 4. This rod is provided with a shoulder 38 at the bottom of the threaded area, which shoulder contacts the lower end of the reduced section 33 when the rod is screwed into the piston and serves as a firm abutment for the lower end of the reduced section 36 of the piston. The section 33 is provided with aligned openings 38 which are adapted to register with an opening 4i! extending transversely through the threaded end portion 3'! of the rod. After the rod has been screwed into the end section 36 and the holes or openings 39 and 40 aligned, a pin or rivet 4! is inserted in these openings and then enlarged or riveted over the ends of the pin to secure the parts together and prevent unscrewing of the portions 36 and 31. It will be observed that the holding means, that is, the rivet pin 4!, must be disposed so that there will be no interference with the reduced section 36 passing into the opening 32 in the casing, and for this reason the pin rivet 3! is headed down flush with the outer wall of the reduced section 36. This effectively locks the piston :32 and rod 2! together, and prevents loosening of these members and subsequent injury to the different elements of the reversing valve structure.

It is to be understood that the construction shown and described is merely an illustration of the preferred embodiments and that such changes may be made as fall within the purview of one skilled in the art without departing from the spirit of the invention and the scope of the appended claims.

I claim:

1. In a reversing valve assembly, a casing, a

cylinder in said casing having an open end to permit piston removal, a removable valve cap threaded in said casing to close the open end of said cylinder, a piston valve having a longitudinal passage therethrough threaded at its upper and lower ends and movable in said cylinder, a reduced section at the lower end of said piston valve having lateral passages disposed above the threaded lower end of the longitudinal passage and communicating therewith, and a collared and threaded piston rod seated against and engaging the lower threaded end of said longitudinal piston passage.

2. In a reversing valve assembly, a casing, a cylinder in said casing having an open end to permit piston removal, a removable valve cap threaded in said casing to close the open end of said. cylinder, a piston valve having a longitudinal passage therethrough threadedat its upper and lower ends and movable in said cylinder, a reduced section at the lower end of said piston valve having lateral passages disposed above the threaded lower end of the longitudinal passage and communicating therewith, a collared and threaded piston rod seated against and engaging the lower threaded end of said longitudinal piston passage, and a transversely disposed pin positively to lock said reduced piston section and said piston rod together.

3. A piston valve and rod for a reversing valve assembly comprising a piston valve having a longitudinal fluid passage therethrough threaded at its upper and lower ends, a reduced section at the lower end of said piston valve having laterally disposed passages above the lower threaded end of the longitudinal fluid passage and communicating with said longitudinal passage, and a threaded piston rod engaging the threaded lower end of the longitudinal piston valve passage.

4. A piston valve and rod for a reversing valve assembly comprising a piston valve having a lonits upper and lower ends, a reduced section at the lower end of said piston valve having laterally disposed passages above the lower threaded end of the longitudinal fluid passage and communicating with said longitudinal passage, a threaded piston rod engaging the threaded lower end of the longitudinal piston valve passage, and a transversely disposed riveted pin positively to lock the threaded end of said piston rod in place.

CLARENCE J. SMITH.

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