Abstract:
A method of making a pump housing that is net-molded and immediately assumes its final shape and design specification without requiring more than de minimis secondary machining processes. The method utilizes molds and cores configured such that none of the fluid ports of the housing produced using the molds and cores have any intersecting geometry. The net-molded pump housing may also include a cross-tube insert providing flow communication between a fluid inlet port and a pressure relief port.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 13/417,703, filed Mar. 12, 2012, and entitled “Plastic Pump Housing and Manufacture Thereof,” incorporated herein by reference in its entirety. This application also claims priority to U.S. Provisional Application Ser. No. 61/452,304, filed Mar. 14, 2011, and entitled “Plastic Pump Housing and Manufacture Thereof,” incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    This disclosure relates to the field of fluid pump manufacture. More particularly, this disclosure relates to methods for making net-shape molded plastic pump housings by utilizing molds and cores configured such that none of the fluid ports of the housing produced using the molds and cores have any intersecting geometry. 
       BACKGROUND 
       [0003]    To reduce costs associated with the manufacture of positive displacement pumps, especially those of the type used in food applications, it is desirable to utilize materials less expensive than conventional brass and stainless steel materials used to make the pump housing. Plastic materials suitable for use as a pump housing material for food applications typically must be suitable for use in high temperature conditions, which conditions often exceed 300 degrees F. The use of plastics is also advantageous to eliminate sources of lead from the pump system. In food and drinking water applications, this is a very desirable feature. 
         [0004]    Glass filled plastics are often suitable for use in such high temperatures, however, guidelines typically associated with the use of plastics in food applications, such as those set forth by NSF International, typically limit the amount of glass fiber exposed to the surface of wetted parts, such as interior surfaces of the pump housing, to one inch of exposed glass fiber or less. As a practical matter, if significant secondary machining of the plastic part is required, the level of exposed fiber will usually exceed the limit. 
         [0005]    Conventional molds and molding techniques desire improvement in connection with the manufacture of plastic pump housings. Such molds and techniques result in housings requiring significant secondary machining, and thus are unsuited for making housings for food applications. 
         [0006]    Accordingly, what is desired is an improved method of making a plastic housing that is suitable for food applications and, as molded is ready for use and any additional machining needed is de minimis and less than about one square inch of the wetted interior surface is subjected to further machining after being formed by molding. 
       SUMMARY 
       [0007]    The above and other needs are met by a method of making a net molded plastic pump housing having a fluid inlet port, a fluid outlet port, and a pressure relief valve port, each in flow communication with a pump cavity. 
         [0008]    In a method according to the disclosure, the method includes the steps of: providing a first mold having has an interior surface topography configured to correspond in negative to exterior topographies of a first portion of the housing and to correspond in negative to topography associated with the fluid inlet port, the fluid outlet port, and the relief valve port of the housing; providing a second molding having an interior surface topography configured to correspond in negative to exterior topographies of a second portion of the housing; providing a first core having an exterior shape configured to correspond in negative to interior topographies of a proximate portion of the cavity of the housing; and providing a second core having an exterior shape configured to correspond in negative to interior topographies of a distal portion of the cavity of the housing. 
         [0009]    The first and second molds and the first and second cores are configured such that none of the fluid inlet port, the fluid outlet port, or the pressure relief valve port of the housing produced using the molds and cores have any intersecting geometry. 
         [0010]    The first and second molds are assembled facing one another with the first and second cores positioned adjacent one another in an end-to-end relationship within the molds, after which plastic is introduced. After the plastic cures, the molds are pulled opposite one another and the cores are pulled opposite one another and substantially perpendicular to the pull of the molds to yield the net shape molded housing. 
         [0011]    The resulting pump housings do not require secondary machining and may be suitable for food applications. 
         [0012]    Also disclosed is a mold and core system for making a net molded plastic pump housing. 
         [0013]    In another aspect, the present invention provides a method of making a net molded plastic pump housing having a fluid inlet port, a fluid outlet port, and a pressure relief valve port, each in flow communication with a pump cavity. In one embodiment, the method includes the steps of: providing a first mold having has an interior surface topography configured to correspond in negative to exterior topographies of a first portion of the housing and to correspond in negative to topography associated with the fluid inlet port, the fluid outlet port, and the relief valve port of the housing; providing a second mold having an interior surface topography configured to correspond in negative to exterior topographies of a second portion of the housing; providing a first core having an exterior shape configured to correspond in negative to interior topographies of a proximate portion of the cavity of the housing; providing at least a second core having an exterior shape configured to correspond in negative to interior topographies of a distal portion of the cavity of the housing; and providing a cross-tube insert having a hollow, generally cylindrical shape. 
         [0014]    The first and second molds and the first and second cores are configured such that none of the fluid inlet port, the fluid outlet port, or the pressure relief valve port of the housing produced using the molds and cores have any intersecting geometry. Further, the first and second molds are assembled facing one another with the first and second cores positioned adjacent one another in an end-to-end relationship within the mold and the cross-tube insert disposed adjacent the first mold topography associated with the fluid inlet port and the relief valve port of the housing, after which plastic is introduced. After the plastic cures, the molds are pulled opposite one another and the cores are pulled opposite one another and substantially perpendicular to the pull of the molds to yield the net shape molded housing. The cross-tube insert provides flow communication between the fluid inlet port and the relief valve port of the molded housing. 
         [0015]    In another aspect, the present invention provides a mold and core system for making a net molded plastic pump housing having a fluid inlet port, a fluid outlet port, and a pressure relief valve port, each in flow communication with a pump cavity. In an embodiment, the mold and core system includes a first mold having has an interior surface topography configured to correspond in negative to exterior topographies of a first portion of the pump housing and to correspond in negative to topography associated with the fluid inlet port, the fluid outlet port, and the relief valve port of the housing; a second mold having an interior surface topography configured to correspond in negative to exterior topographies of a second portion of the housing; a first core having an exterior shape configured to correspond in negative to interior topographies of a proximate portion of the cavity of the housing; and at least a second core having an exterior shape configured to correspond in negative to interior topographies of a distal portion of the cavity of the housing. 
         [0016]    The first and second molds and the first and second cores are configured such that none of the fluid inlet port, the fluid outlet port, or the pressure relief valve port of the housing produced using the molds and cores have any intersecting geometry. The first and second molds are assembled facing one another with the first and second cores positioned adjacent one another in an end-to-end relationship within the molds and a cross-tube insert is disposed adjacent the first mold topography associated with the fluid inlet port and the relief valve port of the housing, after which plastic is introduced. After the plastic cures, the molds are pulled opposite one another and the cores are pulled opposite one another and substantially perpendicular to the pull of the molds to yield the net shape molded housing. Further, the cross-tube insert provides flow communication between the fluid inlet port and the relief valve port of the molded housing. 
         [0017]    In still another aspect, the present invention provides a net molded plastic pump housing having a proximate portion and a distal portion and an internal cavity within the pump housing. In one embodiment, the pump housing a fluid inlet port, a fluid outlet port, and a pressure relief valve port, each in flow communication with the pump cavity; and a cross-tube insert disposed within the pump housing cavity and in flow communication with the fluid inlet port and the pressure relief valve port. None of the fluid inlet port, the fluid outlet port, or the pressure relief valve port of the housing have any intersecting geometry. Further, the net-mold nature of the housing eliminates the need for more than de minimis secondary machining such that the total glass fiber exposure is maintained at or below 1 in 2  total exposure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Further advantages of the disclosure are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
           [0019]      FIG. 1  is a front perspective view of a pump made according to the disclosure. 
           [0020]      FIG. 2  is a front perspective view of a pump housing made according to the disclosure. 
           [0021]      FIG. 3  is a rear perspective view of the pump housing of  FIG. 2 . 
           [0022]      FIG. 4  is a cross-sectional rear-end view of the pump housing of  FIG. 2 . 
           [0023]      FIG. 5  is a cross-sectional side view of the pump housing of  FIG. 2 . 
           [0024]      FIGS. 6 and 7  are exploded views of molds and cores used to make the housing of  FIG. 2  according to the disclosure. 
           [0025]      FIG. 8  is a front perspective view of another embodiment of a pump made according to the disclosure. 
           [0026]      FIG. 9  is a front perspective view of a pump housing for the pump of  FIG. 8   
           [0027]      FIG. 10  is a rear perspective view of the pump housing of  FIG. 9 . 
           [0028]      FIG. 11  is a cross-sectional rear-end view of the pump housing of  FIG. 9 . 
           [0029]      FIG. 12  is a cross-sectional side view of the pump housing of  FIG. 9 . 
           [0030]      FIG. 13  is an exploded view of molds and cores used to make the housing of  FIG. 9  according to the disclosure, and 
           [0031]      FIG. 14  is an assembled view thereof. 
           [0032]      FIG. 15  is an exploded view showing additional components of the pump. 
           [0033]      FIG. 16  is a front perspective view of another embodiment of a pump housing made according to the disclosure. 
           [0034]      FIG. 17  is a rear perspective view of the pump housing of  FIG. 16 . 
           [0035]      FIG. 18  is a front perspective view of a cross-tube insert made according to the disclosure. 
           [0036]      FIG. 19  is a cross-sectional rear-end view of the pump housing of  FIG. 16 . 
           [0037]      FIG. 20  is a cross-sectional side view of the pump housing of  FIG. 16 . 
           [0038]      FIG. 21  is a cross-sectional top view of the pump housing of  FIG. 16 . 
           [0039]      FIG. 22  is an exploded view of molds and cores used to make the housing of  FIG. 16  according to the disclosure, and 
           [0040]      FIG. 23  is an assembled view thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    The disclosure relates to methods for manufacturing a pumps having a plastic housing that are net-shape molded. Pumps according to the disclosure are particularly suited for pumping water for use in beverages, such as for pumping water in carbonated water systems, for espresso machines, and beer cooling systems. 
         [0042]    As used herein, “net-shape molded” means that after the housing is molded it is substantially ready for use and does not require any further significant machining or shaping or polishing, such as the type typically accomplished using computer numerical controlled (CNC) equipment. That is, the terminology “net-shape molded” as used herein will be understood to mean that the housing as molded is substantially ready for use and any additional machining is de minimis and less than about one square inch of the wetted interior surface is subjected to further machining after being formed by molding. 
         [0043]    Accordingly, as the housing as molded does not require further machining, shaping, polishing, or otherwise treatment to be ready to use, the wetted surfaces are not disturbed so as to expose glass fiber to the wetted surface and render the pump unacceptable for food-grade applications. Thus, such pump housings made of glass filled plastics can be made to meet glass fiber limits such that the total glass fiber exposure is maintained at or below 1 in 2  total exposure. In addition, by avoiding the need for significant further machining or the like, manufacturing costs associated with further treatment are saved. 
         [0044]    With initial reference to  FIGS. 1-7 , in a first embodiment the disclosure relates to a method for manufacturing a pump  10  having a plastic housing  12  that is net-shape molded. The pump  10  is, for example, configured as a positive displacement vane pump having various moving and static pump parts that cooperate with the housing  12 , such as a rear cap, endplate, o-rings, bearings, seals, liner, rotor, vanes, alignment pins, snap rings, shaft, pressure relief valve  14 , port inserts  15  and  16 , washers, inlet strainer, and the like. The pump  10  is coupled, as by bolting or clamping or otherwise connecting to a pump motor, such as an integrated or external electric motor, having an output shaft. 
         [0045]    The pump housing  12  is of one-piece molded plastic construction, and the plastic material may be reinforced with fibers such as glass fibers for added strength and temperature resistance. The housing  12  is configured to include a proximate portion  20  and a distal portion  22 . The proximate portion and the distal portion  22  define the ends of the pump cavity and are sealed as by use of caps, seals, and the like, with the proximate portion  20  adapted to be mounted onto a pump motor. 
         [0046]    The housing  12  also includes three fluid passage ports configured for permitting desired fluid travel during operation of the pump, namely, a fluid inlet port  24  for receiving a fluid at a first pressure, a fluid outlet port  26  for expelling the fluid at a second and greater pressure, and a pressure relief valve port  28  through which fluid and pressure may escape in the event of a pressure exceeding a predetermined level. The housing  12  defines an interior pump cavity  30 , with each of the ports  24 ,  26 , and  28  being in flow communication therewith via port entrances  24   a ,  24   b ,  26   a ,  26   b , and  28   a ,  28   b , associated with the ports  24 ,  26 , and  28 , respectively. 
         [0047]    It has been discovered that in providing a net molded housing, it is advantageous that the molds utilized to make the housing  12  be configured such that none of the fluid passage ports, e.g., the fluid inlet port  24 , the fluid outlet port  26 , and the pressure relief valve port  28 , have intersecting geometry. This configuration of the molds and the pump housing results from the requirement that the housing be net molded and not require more than de minimis finishing, since the ports represent complex structure that, if made with intersecting geometry, would require more than de minimis finishing. 
         [0048]    Accordingly, and with reference now to  FIGS. 6 and 7 , the housing  12  is manufactured utilizing an upper mold  40 , a lower mold  42 , a proximate core  44 , and a distal core  46 . The molds  40  and  42  and the cores  44  and  46  are advantageously configured such that none of the fluid passage ports, e.g., the fluid inlet port  24 , the fluid outlet port  26 , and the pressure relief valve port  28 , of the housing  12  produced using the molds and cores have any intersecting geometry. As part of this, it will be appreciated that the cores  44  and  46  therefore do not pass through any of the fluid passage ports. 
         [0049]    The structure of the molds and cores also facilitate a simplified molding process involving simplification in separating the molds and the cores from the molded housing  12 . In this regard, it will be understood that the molds  40  and  42  are assembled facing one another with the cores  44  and  46  positioned adjacent one another in an end-to-end relationship within the molds  40  and  42 , after which plastic is introduced. After the plastic cures, the molds  40  and  42  are pulled opposite one another, as indicated by the arrows A and B ( FIG. 6 ), and the cores  44  and  46  are pulled opposite one another and substantially perpendicular to the pull of the molds  40  and  42 , as indicated by the arrows C and D ( FIG. 6 ). 
         [0050]    The upper mold  40  has an interior surface topography  50  configured to correspond in negative to exterior topographies of an upper portion of the housing  12  and to correspond in negative to topography associated with the fluid inlet port  24 , the fluid outlet port  26 , and the relief valve port  28 . The lower mold  42  has an interior surface topography  52  configured to correspond in negative to exterior topographies of a lower portion of the housing  12 . The core  44  is solid and has an exterior shape  54  configured to correspond in negative to interior topographies of a proximate portion of the cavity  30  of the housing  12 , which is substantially cylindrical. The core  46  is solid and has an exterior shape  56  configured to correspond in negative to interior topographies of a distal portion of the cavity  30  of the housing  12 , which is a stepped cylindrical profile. The upper mold  40  includes rods  57 ,  58 , and  59  onto which the inserts  14 ,  15 , and  16 , respectively, are slidably received. 
         [0051]    As will be appreciated from the views, all of the portions of the mold  40  corresponding to the fluid inlet port  24 , the fluid outlet port  26 , and the relief valve port  28  terminate at the distal core  46 , and the core  46  does not pass through any of these fluid passage ports of the housing  12 . It has been discovered that this construction and configuration of the molds and cores enables the molds to be made so that the part as molded is ready for use and does not require any further machining or shaping or polishing. That is, the mold surfaces conform to the desired final shape and dimensions, with no further treatment. 
         [0052]    In conjunction with this, it has been discovered that this feature of the mold components enables a simple mold pull procedure in which the upper and lower molds are removed by a first linear pulling motion in which the upper and lower molds are pulled away from one another, and the cores are removed by a second linear pulling motion in which the in which the proximate and distal cores are pulled in opposite directions, with the second linear pulling motion being substantially perpendicular to the first linear pulling motion. 
         [0053]    This method of pulling the molds and the cores, as enabled by the configurations of the molds and the cores, has been observed to avoid the presence of flash, burrs, and other extraneous plastic on the molded part that would require further machining or shaping or polishing. Thus, the housing  12  molded according to the disclosure using the molds  40  and  42 , and the cores  44  and  46  have been observed to be net-shape molded and to conform to the desired final shape and dimensions. 
         [0054]    With reference now to  FIGS. 8-15 , a second embodiment according to the disclosure relates to a method for manufacturing a pump  100  having a plastic housing  102  that is net-shape molded. The housing  102  is substantially identical to the housing  102 , except that it includes a distal bore insert  103  included during the molding. The bore insert  103  is preferably of stainless steel construction and located corresponding to the distal portion  22 ′ of the housing  102 . The insert  103  is preferably threaded. The addition of the insert  103  enables a stronger connection point than the plastic material of the housing and has been observed to provide improved operation including decreased noise during operation of the pump  100  as compared to the pump  10 . 
         [0055]    The housing  102  is made using molds  40 ′ and  42 ′ and cores  44 ′ and  46 ′. The molds  40 ′ and  42 ′ and cores  44 ′ and  46 ′ are substantially identical to the molds  40  and  42  and cores  44  and  46 , except some of the respective topographies are configured where necessary to receive the rear bore insert  103 . That is, the bore insert  103  is provided to provide some of the more complex topography of the housing  102 , such that the interior surfaces of the molds are simplified. In this regard, the various corresponding parts of the housing  102  and the molds  40 ′ and  42 ′, and cores  44 ′ and  46 ′ are referred to with the same numbers as the embodiment of  FIGS. 1-7 , except with a prime designation. 
         [0056]    As shown in  FIG. 15 , the housing  102  is compatible with a variety of internal pump components to yield the pump  100 . For example, as shown, the housing  102  is configured to receive the pressure valve  14 ′ which includes valve insert  50 , valve body  52 , spring  54 , o-ring  56 , relief valve  58 , valve cover  60 , spring  62 , adjusting screw  64 , o-ring  66 , and cap  68 . Other components include ball bearing  70 , seal  72 , rear bearing  74 , rotor  76  having vanes  78  spaced apart by pins  78   a , plastic liner  80 , alignment pin  82 , front bearing  84 , o-ring  86 , plate  88 , and snap-ring  90 . 
         [0057]    With reference now to  FIGS. 16-23 , a further embodiment according to the disclosure relates to a method for manufacturing a pump having a plastic housing  202  that is net-shape molded. The housing  202  is similar to the housing  12 , except that an additional cross-tube insert  92  is incorporated into the housing  202 . The housing  202  may, in some instances, also include a distal bore insert  103 ″ included during the molding. As shown in  FIG. 21 , the cross-tube insert  92  provides flow communication between the pressure relief valve port  28 ″ and the fluid inlet port  24 ″. Thus in the event of an overpressure within the pump, excess fluid is allowed to pass through the pressure relief  28 ″—thereby reducing the excess pressure within the pump—and the excess fluid is recycled back to the fluid inlet port  24 ″. 
         [0058]    As seen in  FIG. 18 , the cross-tube insert  92  is hollow and generally cylindrical in shape, preferably with ends  94  and  96  conformed to the generally cylindrical shape of pressure relief valve port  28 ″ and the fluid inlet port  24 ″. The cross-tube insert may be metallic, but is preferably made from the same plastic material as the remainder of the housing  202 . If the same plastic material is used as for the housing  202 , the material of the cross-tube insert  92  may partially fuse with the plastic of the housing during addition and curing of the plastic for the housing. 
         [0059]    The housing  202  is made using molds  40 ″ and  42 ″ and a plurality of cores as illustrated in  FIGS. 22 and 23 . The molds  40 ″ and  42 ″ are substantially identical to the molds  40  and  42 , except some of the respective topographies are adapted to receive the cross-tube insert  92  adjacent the first mold topography associated with the fluid inlet port and the relief valve port of the housing. Likewise, the cores  44 ″ and  46 ″ are similar to cores  44  and  46 , except that in some instances the distal interior topography of the housing  202  may be provided by a plurality of cores  46 ″ and  48 ″ rather than a single distal core. 
         [0060]    In general, the various corresponding parts of the housing  202  and the molds  40 ″ and  42 ″, and cores  44 ″ and  46 ″ are referred to with the same numbers as the embodiments of  FIGS. 1-7  and  FIGS. 8-15 , except with a double prime designation. 
         [0061]    As with the aforementioned embodiments, the housing  202  is compatible with a variety of internal pump components, such as seals, o-rings, front and rear bearings, a rotor having sliding vanes, an endplate, and a snap-ring. 
         [0062]    The foregoing description of preferred embodiments for this disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.