Diaphragm piston valve

A diaphragm piston having a diaphragm between a body and plate. A post integral with and extends from the body through the diaphragm and the plate. A stop is coupled to the post and limits the axial movement of the plate away from the body. A spring seat is coupled to the post. A spring is between the plate and the spring seat. The post includes a first shoulder and the stop engages the first shoulder. The stop includes an orifice shaped to move axially on the post past the first shoulder and rotate about the post and engage the first shoulder. The first shoulder has at least one circumferential recess and the orifice in the stop includes a radial tab smaller than the recess. A first lock prevents rotation between the stop and the post. A second lock is also provided preventing rotation between the plate and post. A unique stem which guides the diaphragm piston in a valve seat is provided.

BACKGROUND AND SUMMARY OF THE INVENTION
 The present invention relates generally to pistons and more specifically,
 to an improved diaphragm piston.
 Diaphragm pistons, for example, for use in a service portion of a rail
 pneumatic brake valve, for example, a DB-60 brake valve available from New
 York Air Brake Corporation, is illustrated in FIGS. 1 and 2. The diaphragm
 piston includes a rubber diaphragm 24 held between a body 20 and a plate
 28 which is secured together by a post 10 having a head 12 and a threaded
 portion 16 which receives a nut 34. A spring 36 is positioned between a
 spring seat 38 and the back side of the plate 28. A retainer 40, secured
 to the post 10 by C-ring 42, acts as a stop for the spring seat 38. A stem
 45 is inserted into and is secured to post 10 by aligning orifices 19 and
 46 and pin 47. Stem 45 is received and guided in a bushing of a valve seat
 (shown in phantom). The stem 45 includes a shoulder 44 which can catch and
 wear the valve seat bushing.
 Other than the rubber diaphragm 24, all of the parts are metal. In that all
 of the parts are metal, the post 10 requires processing to create the
 different areas, including the threading. The number of parts increase the
 expense of the diaphragm piston. Also, there is no mechanism to prevent
 rotation of the elements relative to each other.
 The present invention is a diaphragm piston having a diaphragm between a
 body and plate. A post integral with and extends from the body through the
 diaphragm and the plate. A stop is coupled to the post and limits the
 axial movement of the plate away from the body. A spring seat is coupled
 to the post. A spring is between the plate and the spring seat. The post
 includes a first shoulder and the stop engages the first shoulder. The
 stop includes an orifice shaped to move axially on the post past the first
 shoulder and rotate about the post and engage the first shoulder. The
 first shoulder has at least one circumferential recess and the orifice in
 the stop includes a radial tab smaller than the recess.
 A first lock prevents rotation between the stop and the post. The lock
 includes a recess on both the stop and the plate and a key is inserted in
 the recess when aligned. The spring retains the key in the recess. A
 second lock is also provided preventing rotation between the plate and
 post. The second lock includes at least one pin and a recess, one of which
 is on the plate and one of which is on the body.
 The post includes a second shoulder and the spring seat engages the second
 shoulder. The spring seat includes an orifice shape to move axially on the
 post past the second shoulder and rotate about the post and engage the
 second shoulder. The second shoulder for the spring seat includes a first
 portion having a generally first polygonal shape and a second portion
 having a generally second polygonal shape of more sides than the first
 shape. The orifice in the spring seat is shaped to move axially past the
 first portion of the second shoulder and rotate about the post and engage
 the second portion of the second shoulder. Preferably, the first polygonal
 shape is generally a triangular shape and the second polygonal shape is
 generally an hexagonal shape.
 A unique relationship between the piston guide stem and valve seat is
 provided. A guide is integral with and extends from the body in a
 direction opposite from the direction the post extends from the body. A
 stem is loosely seated in an orifice of the guide. The stem includes a
 uniform diameter, with circumferentially spaced flats, which maintains
 guiding contacts with a bushing of a valve seat over the total travel of
 the piston.
 Whereas the diaphragm is rubber, the body, the plate and the lock that
 prevents rotation between the stop are all made of plastic. The stem,
 spring seat and the spring are made of metal.
 Other objects, advantages and novel features of the present invention will
 become apparent from the following detailed description of the invention
 when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PRIOR ART
 In addition to the previously described portions of the diaphragm piston of
 the prior art of FIGS. 1 and 2 further details will be explained. Post 10
 includes a head 12 forming a shoulder 13 with a body portion 14. A
 threaded portion 16 receives the nut 34. A recess 18 in the post 10
 receives the C-ring 42. The body 20 includes an orifice 22 to receive the
 body portion 14 of the post 10. The diaphragm 24 includes an orifice 26.
 The plate 28 includes an orifice 30 and a recess 32 to receive the spring
 36. The spring seat 38, retainer 40 and C-ring 42 are also shown.
 Post 10 includes a guide 17 with a stem 45 inserted into orifice 11 and
 secured to the post 10 by pin 47. Pin 47 is secured into stem 45 and is
 retained by orifices 19. The stem 45 includes a head 43 and a reduced
 diameter position 48 with a stem-shoulder 44 therebetween. The head 43 is
 the guiding surface in the bushing of a valve seat (shown in phantom in
 FIG. 1). The reduced diameter portion 48 with the bushing defines an air
 passage in the valve seat. Once the head 43 is out of the bushing, there
 is no guiding contact except if the stem 45 moves laterally. In which
 case, the stem-shoulder 44 will catch the top of the valve seat causing
 damage during the valve closing.
 The method of assembly of the prior art includes positioning the diaphragm
 24 between body 20 and plate 28 and inserting the post 10 therethrough.
 The nut 34 is threadably received on thread 16 of post 10, clamping the
 diaphragm 24 between the body 20 and the plate 28. Spring 36 is then
 placed around the post 10 as is spring seat 38 and retainer 40. The spring
 is then depressed until the C-ring 42 is aligned and can be received
 within the recess 18 of the post 10. Stem 45 is then inserted into post 10
 and secured by pin 47.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A diaphragm piston of the present invention is illustrated in FIGS. 3 and
 4. A diaphragm 52 is positioned between a body 50 and a plate 56. A center
 portion 57 of the plate 56 extends through an orifice 54 in the diaphragm
 52. The center portion 57 includes an orifice 58 having both a pair of
 recesses 60 and a third recess 64. The recesses 60 receive pins 62
 extending from the face of the base 50. This prevents rotation of the
 plate 56 relative to the body 50.
 The body 50 also includes an integrally formed post 80. The post 80 has a
 first portion 82 with a rim 84 extending therefrom which forms a first
 shoulder. A pair of circumferential recesses 86 are provided in the rim
 84. A nut 66 includes a center orifice 68 and a pair of radial tabs 70,
 only one of which is shown in FIGS. 3 and 4. The radial tabs 70 are
 aligned and received within the circumferential recesses 86 of the rim 84
 and then rotated 90.degree. such that the radial tabs are received under
 the rim 84 to engage the first shoulder. This locks the plate 56 to the
 body 50 and the diaphragm 52 there between. The nut or stop 66 also
 includes radial recesses 72. When one of the recesses 72 on the nut 66 is
 aligned with the recess 64 in the plate 56, a key 74 is inserted in both
 of the recesses to thereby lock the nut 66 from rotation.
 The diaphragm piston also includes a spring 76 and a spring seat 78 with an
 orifice 79. The post 80 includes a reduced diameter section 88 extending
 from the rim 84. A generally hexagonal portion 92 and a generally
 triangular section 90 formed the end of the post 80. Although a hexagonal
 cross-section 92 and a triangular cross section 90 are shown, both of them
 may be any polygonal shape as long the polygonal shape of 92 has more
 sides than that of 90. The orifice 79 is also a polygonal shape and may
 be, for example, a triangle which would slide past the triangular portion
 90 and when rotated, come to rest against a second shoulder, which is 94
 formed between the hexagonal shape 92 and the triangular shape 90. The
 orifice 79 may be for example, a triangular shape or an irregular
 hexagonal shape.
 After the spring 76 is inserted around the post 80, one end is received in
 the recess 57 of the plate 56. The spring seat 78 is then also inserted
 onto post 80 compressing the spring 76. As discussed previously, the
 spring seat 78 is moved passed the triangular section 90 onto the
 hexagonal section 92. Then it is rotated for example, 60.degree. until the
 body of the spring seat 78 rests against the second shoulder 94. It should
 be noted that the spring 76 also engages the key 74 and retains it in the
 recesses 72 and 64. In the assembled condition, the spring seat 78 will
 come to rest against a base 199.
 The body 50 also includes an integrally formed guide 81 which includes
 orifice 87. The guide 81 has a first shoulder 83 which is for example, a
 triangular shape or an irregular hexagonal shape. The guide 81 also
 includes a reduced diameter section 85. A stem 95 is loosely seated into
 orifice 87. The stem 95 has two or more flats 96 which are
 circumferentially spaced and do not extend axially to the ends of the
 stem. The portions of the stem 95 between the flats 96 are the same
 diameter as the non-flattened head portion 97. Thus, the stem is in
 guiding contact with the bushing of the valve seat 200 as the stem
 operates to raise the valve element 201. The flats provide an air passage
 of the same cross-sectional area as the reduced diameter portion 48 of
 prior art stem 45 of FIGS. 1 and 2. This configuration of stem 95 prevents
 the catching and damage of the prior art stems. The stem 95 may be used by
 itself as a replacement of stem 45 in the prior art diaphragm piston.
 A substantial reduction in costs results from making the base 50 with the
 integral post 80, the plate 56, the nut 66 and the key 74 from plastic.
 These molded products may be made of composite plastics, for example,
 Verton. The diaphragm 52 is rubber and preferably fabric reinforced. The
 spring 76 may be for example, musical wire. The spring seat 78 may be
 steel. The spring 76 and the spring seat 78 may be zinc plated. The stem
 95 may be stainless steel.
 Although the present invention has been described and illustrated in
 detail, it is to be clearly understood that the same is by way of
 illustration and example only, and is not to be taken by way of
 limitation. The spirit and scope of the present invention are to be
 limited only by the terms of the appended claims.