Abstract:
A valve molded entirely of resin includes a valve body having an inner housing, a housing cap fitted in the inner housing, a valve element such as a ball, and a stem coupled to the valve element and actuatable to move the latter for providing selective communication between ports in the inner housing and the housing cap. The valve body is covered with a frame molded of resin and substantially covering the exterior surface of the valve body.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a valve molded entirely of resin and a method of making the same. 
     BACKGROUND OF THE INVENTION 
     Valves having parts made of resin are advantageous in that they can be mass-produced by injection molding, are resistant to corrosion, and inexpensive to construct. 
     One attempt to provide an increased mechanical strength to the body of such a valve has been to increase the thickness of the molded valve parts. However, thick valve parts cannot easily be molded, and their mechanical strength has proven unsatisfactory. When assembling valves, it is necessary to fasten seal rings, gaskets and other parts under a prescribed load. Prior resin-molded valves include a holder ring for reinforcing and holding a resin housing, and a reinforcement metal cover for protecting the resin housing against external shocks and internal fastening stresses. The valves may additionally have a valve cover for pressing and holding an inner valve body or a seal ring, the valve cover being fastened in position by a plurality of fasteners (mostly of metal) such as fastening bolts. 
     The prior resin-molded valves, therefore, require separate members made of metal in most cases for increasing the mechanical strength of the valve parts and fastening them under a prescribed load. These additional components have been an obstacle to efforts to achieve a reduction in the production cost and a full degree of corrosion resistance. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a resin-molded valve which is made up of a reduced number of parts, has a high degree of corrosion resistance and mechanical strength, and can be mass-produced efficiently at a greatly reduced cost. 
     Another object of the present invention is to provide a method of manufacturing valves by molding valve parts of resin in a mold assembly and simultaneously assembling the valve parts therein. 
     According to the present invention, a frame is molded of resin over a valve body and substantially covers the external surface thereof. The valve body is composed of molded parts such as an inner housing, a housing cap fitted in the inner housing, a valve element such as a ball, and a stem coupled to the valve element and actuatable to move the latter for providing selective communication between ports in the inner housing and the housing cap. For the molding operation, the valve body components are first assembled together and inserted in a mold cavity, and then the frame is molded over the valve body, whereupon the valve body is completely assembled by the molded frame. Since the valve of the invention is constructed of molded parts which are assembled together while they are being molded, no separate fastening parts are necessary, and no additional step of fastening the valve components together is required. 
     The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal cross-sectional view of a ball valve according to the present invention; 
     FIG. 2(a) is a longitudinal cross-sectional view of an inner housing of the valve; 
     FIG. 2(b) is a side elevational view of the inner housing shown in FIG. 2(a); 
     FIG. 2(c) is a plan view of the inner housing of FIG. 2(a); 
     FIG. 3(a ) is a longitudinal cross-sectional view of a housing cap of the valve; 
     FIG. 3(b) is a side elevational view of the housing cap shown in FIG. 3(a); 
     FIG. 3(c) is a plan view of the housing of FIG. 3(a); 
     FIG. 4(a) is a longitudinal cross-sectional view of a valve frame; 
     FIG. 4(b) is a side elevational view of the valve frame illustrated in FIG. 4(a); 
     FIG. 4(c) is a plan view of the valve frame of FIG. 4(a); 
     FIG. 5 is a longitudinal cross-sectional view of a tentatively assembled valve body; and 
     FIG. 6 is a view showing a mold assembly for molding the valve according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a valve A according to the present invention comprises a valve element or ball 1 made of resin, a drive shaft or stem 2 made of resin and coupled to the ball 1 for turning the ball 1 through 90° to shut off a fluid flow or control a flow rate, seat rings 3a, 3b made of resin and held against the ball 1 for preventing any fluid flow when the ball 1 is in the shutoff position, an inner housing 4 of resin in which the ball 1 is rotatably disposed, and a housing cap 5 of resin partly fitted in the inner housing 4 and retaining the ball 1 in the inner housing 4. 
     As illustrated in FIGS. 2(a) through 2(c), the inner housing 4 has an outer end port 10, an inner cavity 11 accommodating the ball 1 therein, a boss 12 through which the stem 2 extends, and a recess 13 defined between the outer end port 10 and the inner cavity 11 and receiving therein one of the seat rings 3a. The inner housing 4 also has a plurality of angularly spaced locking recesses 17 defined in an end wall surface of the inner cavity 11 remotely from the recess 13. As shown in FIG. 1, a gland packing 6 is disposed in a recess 12a in the boss 12 and retained therein by a packing holder 7. A thrust washer 8 is located in another recess 12b defined in the boss 12. The gland packing 6, the packing holder 7, and the thrust washer 8 are made of resin. A pair of O-rings 9 made of synthetic rubber are placed in the boss 12 around the stem 2. 
     The housing cap 5 is illustrated in FIGS. 3(a) through 3(c), and has an outer end port 14 and an inner recess 15 formed remotely from the outer end port 14 and receiving the other seat ring 3b. The housing cap 5 includes a circular flange 5a fitted closely in the cavity 11 in the inner housing 4 and having a plurality of angularly spaced locking teeth 18 received respectively in the locking recesses 17 in the inner housing 4. 
     The ball 1, the inner housing 4, the housing cap 5, the stem 2, and the other associated parts are tentatively assembled into a valve body 16 as shown in FIG. 5. The assembled valve body 16 has a peripheral or exterior surface which is almost entirely composed of the peripheral or exterior surfaces of the inner housing 4 and the housing cap 5. 
     As shown in FIG. 1, the assembled valve body 16 is covered with a cover or frame 20 molded of resin. The frame 20 is of a shape complementary to the profile of the valve body 16 as illustrated in FIGS. 4(a) through 4(c), and has end surfaces pressed against the seat rings 3a, 3b and the packing holder 7. 
     The valve according to the present invention is composed of the valve body 16 and the frame 20 fitted thereover. The frame 20 has a central sleeve 20a over which a head cap 22 is fitted with an O-ring 21 of synthetic rubber being interposed therebetween. 
     The valve of the foregoing construction is manufactured in the following manner: 
     The ball 1, the stem 2, the inner housing 4, the housing cap 5, the packing holder 7, and the head cap 22 are individually injection-molded of a suitable resin material. The seat rings 3a, 3b, the gland packing 6, the thrust washer 8, and the O-rings 9, 21 are also separately fabricated. 
     The foregoing components except the head cap 22 and the O-ring 21 are tentatively assembled into the valve body 16, which is then inserted into a cavity in a mold assembly, as shown in FIG. 6, for molding the frame 20. 
     In FIG. 6, the mold assembly is composed of a fixed attachment plate 23, a fixed mold plate 24, a movable mold plate 25, a movable attachment plate 26, a bearing plate 27, a locating ring 28, a sprue bushing 29, a slidable insert 30 which is a cylindrical rod having a diameter less than the inside diameters of the ports 10 and 14 and substantially equal to the inside diameters of the openings through the seats 3a and 3b and the ball 1, a core insert 31, and ejector pins 32. A suitable resin material is then injected into the cavity in the mold in which the valve body 16 is placed, for molding the frame 20 integrally around the valve body 16 under molding pressure and due to resin properties. At the same time, the seat rings 3a, 3b and the packing holder 7 are firmly held in position under holding pressure, so that the valve body 16 is completely assembled at the same time that the frame 20 is molded. 
     Thereafter, the mold frame 20 with the valve body 16 fitted therein is removed from the mold assembly, and the head cap 22 with the O ring 21 placed there is mounted on the sleeve 20a of the frame 20. The valve illustrated in FIG. 1 is now completed. 
     With the valve constructed of the present invention, the frame 20 is securely fitted over the inner housing 4 and the housing cap 5 and serves to reinforce them for an increased mechanical strength. Particularly, the frame 20 provides added rigidly to the inner housing 4 and the housing cap 5 to prevent them from being deformed when their ports 10, 14 are subjected to fastening stresses at the time they are coupled to external pipes and also to protect them against external shocks. 
     According to the method of the invention, the frame 20 is integrally injection-molded around the valve body 16, which has been tentatively assembled and placed in the mold assembly. Upon injection-molding of the frame 20, the seat rings 3a, 3b and the packing holder 7 are fastened under a suitable force due to molding pressure, and the valve body 16 is thus completely assembled within the mold assembly. 
     Therefore, the valve of the invention requires no holding ring, no metal cover, no ball cover, and no fastening bolts which have been essential components of conventional resin-molded valves, and hence needs no operation for fastening such parts. The valve can be constructed of a reduced number of parts, is completely assembled while the components are being molded, and can be mass-produced efficiently through a reduced number of manufacturing steps at a reduced cost. The valve with its parts molded together is of an increased degree of mechnical strength. Since all of the valve parts are of molded resin, the valve is highly resistant to corrosion. 
     Although a certain signal preferred embodiment has been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims. For example, the present invention is equally applicable to other valve types than ball valves, such as needle valves or butterfly valves, for example.