Patent Publication Number: US-9404484-B2

Title: Diaphragm pump and valve assembly with molded wobble plate

Description:
FIELD OF THE INVENTION 
     The invention relates generally to diaphragm pumps, and more particular to improved cam/bearing assemblies, improved wobble plate/bearing assemblies, and improved valve assemblies for diaphragm pumps. 
     BACKGROUND OF THE INVENTION 
     Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms), and restrict motion of the fluid to the one desired direction by check valves. One type of reciprocating pump is a diaphragm pump. A diaphragm pump is a positive displacement pump that uses a combination of the reciprocating action of a diaphragm, such as a rubber diaphragm, a wobble plate for driving each of a series of pistons formed in the diaphragm, a series of chambers formed on a valve housing for receiving piston structures of the diaphragm, and suitable non-return check valves coupled to the valve housing to ultimately pump a fluid from an inlet port to an outlet port. 
     Diaphragm pumps are commonly used to move relatively small amounts of fluid, such as water from one location to another. Diaphragm pumps can be used, for example to move water into and out of a recreational vehicle, on property, and the like. Typical flow rates for diaphragm pumps are up to ten gallons per minute (GPM) for commercial applications, although diaphragm pumps with greater flow capacities are available for industrial applications. 
     Diaphragm pumps are often driven by motors, gas-powered or electric motors including a drive shaft. A cam and ball bearing assembly interposed between the drive shaft and a wobble plate convert the rotational movement of the drive shaft to the push-pull motion of a series of pistons through the wobble plate. The wobble plate is mechanically coupled to the diaphragm. A nutating action of the diaphragm and wobble plate acts to actuate each piston sequentially into each chamber of the series of chamber defined on the valve plate to push and pull fluid into and out of each chamber. 
     Diaphragm pumps are typically single-acting in which suction during one direction of piston motion pulls fluid from in inlet chamber into a chamber of the valve plate, and during the other direction of the piston motion discharges the fluid from the chamber into an outlet chamber. More specifically, when the volume of a chamber of valve plate is increased (i.e. the piston moving out of or away from the chamber), the pressure in the chamber decreases, and fluid is drawn into the chamber from the inlet chamber in fluid communication with the inlet port to the pump. When the chamber pressure later increases from decreased volume (the piston moving into or down the chamber), the fluid previously drawn into the chamber is forced out of the chamber into an outlet chamber in fluid communication with an outlet port of the pump. Finally, the diaphragm moving up and out of the chamber once again draws fluid into the chamber, completing the cycle. 
     Examples of diaphragm pumps are described in, for example, U.S. Pat. Nos. 5,791,882, 6,048,183, 6,623,245, and 6,840,745 all of which are incorporated herein by reference in their entireties. 
     As discussed above, the wobble plate is operably coupled to the rotating drive shaft of a motor via the cam/bearing assembly. More particularly, the cam is coupled the drive shaft at an inner surface of the cam such that the cam does not rotate with respect to the shaft, but rather with the shaft. The cam also includes an outer annular surface coupled to an inner race of the ball bearing such that the cam does not rotate relative to the inner race of the ball bearing. The wobble plate is coupled to an outer race of the ball bearing such that the wobble plate surrounds the cam/bearing assembly, and the wobble plate does not rotate with respect to the outer race of the ball bearing. 
     During pump operation, particularly continuous duty operation, heat is generated from internal friction in the bearing as well as radiant heat from the motor. The generated heat causes the connections between the cam and bearing, and the wobble plate and bearing to become loose due to different expansion rates of the materials forming each of the cam, bearing, and wobble plates. When the connections become loose, flow performance suffers, such that flow can be reduced in excess of 50% of its capability. More heat from friction is generated after the connections become loose, accelerating the performance decrease and ultimately causing the bearing to fail. 
     Another common mode of failure of either the connections between the cam and bearing or the bearing and wobble plate are caused from the offset positioning of the cam on the drive shaft of the motor. The nutating action then places excessive load on the wobble plate which can dislocate the wobble plate from the bearing and/or the cam. Harmonic oscillations created due to the offset nature of the wobble plate can also cause the bearings to come loose. Similar to above, when the connections become loose, flow performance suffers, such that flow can be reduced in excess of 50% of its capability. 
     One technique for lengthening the durability of a cam/bearing connection  1  and referring to  FIG. 1 , is to press fit a cam  10  made of cast zinc allow into an inner race  14  of a bearing  12  forming an interference fit. Cam  10  can be staked into place for further durability by punching dimples  16  into a face  18  of cam  10  as shown in  FIG. 1 , thus deforming cam  10  to help hold it into bearing  12 . Although staking cam  10  into bearing  12  has improved the durability of the connection, failures are still seen after long continuous duty operation. 
     Regarding a wobble plate/bearing connection  20  as shown in  FIG. 2 , during assembly, a wobble plate  22  made of cast aluminum alloy is heated to 140 degrees Celsius and bearing  12  is pressed into wobble plate  22 . Because wobble plate  22  is machined to tight tolerances, after wobble plate  22  cools and shrinks, there is a tight interference fit between an outer race  28  of bearing  12  and wobble plate  22 . Wobble plate  22  is then staked at  24  to further secure bearing  12  to wobble plate  22  as shown in  FIG. 2 . Further, a plurality of set screws  26  are installed to hold outer race  28  of bearing  12  from rotating inside wobble plate  22 . This technique has greatly reduced or even completely eliminated the loose connection condition between the wobble plate and bearing even after 1000+ hours of continuous duty operation. However, this technique is both expensive and time consuming during assembly. 
     Regarding the check valve and valve housing assembly, inlet and outlet valves positioned on and carried by the valve housing typically found in diaphragm pumps have problems of inconsistent sealing, thereby further reducing the pump operation efficiency. 
     Referring to  FIGS. 3A-4B , a prior art inlet valve  30  includes a central mounting section  32 , such as a post, and a resilient, seal-forming section  34  surrounding an end  36  of post  32 . Central mounting section  32  acts to secure inlet valve  30  within a valve seat  38  of a chamber of the valve housing. Resilient section  34  includes a center section  40  and a peripheral relief zone  42  or lip. Peripheral relief zone  42  acts to form a seal when slightly flexed within valve seat  38  of the valve housing, thereby sealing and restricting fluid communication through the inlet apertures. 
     Referring to  FIGS. 4A-4C , prior art valve is depicted being mounted in a valve seat of a chamber of the valve housing. Referring to  FIG. 4A , a first side  44  of peripheral relief zone  42  is shown in the relaxed position, i.e. how the valve naturally lies prior to being assembled within the valve seat, while a second side  46  is shown in a slightly flexed, sealed position, i.e. when the piston of the diaphragm is moving into the chamber in which the inlet valve is mounted such that fluid flow is restricted or completely prevented. As shown in  FIG. 4C , a first side  44  of peripheral relief zone  42  is again shown in the relaxed position, i.e. how the valve naturally lies prior to being assembled within the valve seat, while a second side  47  is shown in a flexed, or opened position, such that peripheral relief zone  42  is significantly flexed or lifted out of the seat to allow fluid flow. As shown in  FIG. 4A , a cross-section of the peripheral relief zone comprises a stepped portion or a mathematical profile represented by a discrete or discontinuous function. However, this “stepped” design provides minimal flexural relief in that it only seals along an edge of lip  42 , such that an effective sealing area  48  of valve  30  is limited to a thin line (as seen on side  46 ), creating sealing inconsistencies. 
     Referring to  FIGS. 5A-6B , a prior art outlet valve  50  includes a central mounting section  52 , such as a post, and a resilient, seal-forming section  54  surrounding an end of post  52 . Central mounting section  52  acts to secure outlet valve  50  within a valve seat  56  on an exterior side of the valve housing such that outlet valve  50  extends between two chambers of the valve housing. Resilient section  54  includes a center section  58  and a peripheral relief zone or lip  60 . Peripheral relief zone  60  acts to form a seal within the valve housing, thereby sealing and restricting fluid communication from a chamber through the outlet apertures, i.e. when a piston of the diaphragm is moving out of the chamber. 
     Referring to  FIGS. 6A and 6B , prior art outlet valve  50  is depicted being mounted in a valve seat  56  on an exterior of the valve housing such that outlet valve covers outlet apertures of a chamber of the valve housing. A first side  62  of peripheral relief zone  60  is shown in the relaxed position, i.e. how the valve naturally lies prior to being assembled within the valve seat, while a second side  64  is shown in a slightly flexed, sealed position, i.e. such that fluid flow is restricted or completely prevented. This is when the piston of the diaphragm is moving out of the chamber to which outlet valve  50  is mounted. The valve is in an open position when peripheral relief zone  60  is significantly flexed or lifted out of the seat to allow fluid flow. As shown in the figures, a cross-section of peripheral relief zone  60  comprises a stepped portion or a mathematical profile represented by a discrete or discontinuous function. However, this “stepped” design provides minimal flexural relief in that it only seals along an edge of lip  60 , such that an effective sealing area  66  of valve  50  is limited to a thin line (as seen on side  64 ), creating sealing inconsistencies. 
     Furthermore, inconsistencies in the effective sealing area can be created during manufacturing the prior art valves. When molding the prior art valves, the molding die typically includes two halves. Where the two halves meet, there is the potential for flash, which is the material that is squeezed out at the parting line of the two halves. Referring to  FIGS. 5B, 6B , this parting line  68 ,  70  is typically coextensive with the sealing edge of the lip of either the inlet valve or the outlet valve. This can cause an inconsistent sealing edge, and therefore an inconsistent seal. 
     In view of the issues of the prior diaphragm pumps, there remains a need for an improved cam/bearing assembly and an improved bearing/wobble plate assembly for improving the life and efficiency of the pump, without significantly increasing the time, complexity, and cost for manufacturing the pumps. Furthermore, there remains a need for an improved check valve design for improving the effective sealing characteristics of both inlet and outlet valves. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention are directed to an improved diaphragm pump including an improved wobble plate and bearing assembly, an improved cam and bearing assembly, and an improved valve assembly, for increasing the pump reliability, life, and efficiency. In embodiments of the invention, an improved cam and bearing assembly includes a cam injection molded directly into an inner race of a bearing to prevent the cam from pulling away from the bearing. In additional embodiments of the invention, an improved wobble plate and bearing assembly includes a wobble plate injection molded directly onto an outer race of the bearing to prevent the wobble plate from pulling away from the cam and bearing assembly. In yet additional embodiments of the invention, improved inlet and/or outlet check valves include rounded peripheral relief zones that form a band, as opposed to a line, of effective sealing area when in the sealed position within a valve seat that eliminate or reduce sealing inconsistencies and increase sealing efficiencies. 
     In generally, a diaphragm pump according to embodiments of the invention can comprise a pump housing including a front cover and a back cover for housing the pump components. The front cover includes an inlet port, an inlet chamber in fluid communication with the inlet port, an outlet port, and an outlet chamber in fluid communication with the outlet port. The pump includes a motor assembly comprising a motor and a rotatable drive shaft, wherein the rotatable drive shaft extends through the back cover. A cam and bearing assembly is coupled to the drive shaft, and a wobble plate is secured to and fixed relative to an outer race of the bearing. The wobble plate includes a plurality of piston structures that correspond to piston structures of a diaphragm coupled to a face of the wobble plate having the piston structures thereon. The combination of the piston structures and the diaphragm form pistons. 
     A valve assembly is fixed relative to the diaphragm/wobble plate assembly via the housing and includes a plurality of chambers and a plurality of check valves, wherein each chamber is in selective fluid communication with each of the inlet chamber and the outlet chamber of the front cover. The check valves are shiftable between an open position in which the chamber is in fluid communication with one of the inlet chamber and the outlet chamber, and a closed, sealed position in which the chamber is not in fluid communication with one of the inlet and the outlet chamber. 
     The cam and bearing assembly are adapted to convert a rotating motion of the drive shaft to a nutating motion of the wobble plate, such that each piston engages a chamber of the valve assembly in sequential order, thereby forcing fluid into the chamber from the inlet chamber during an intake stroke, and out of the chamber into the outlet chamber during a discharge stroke, the strokes cycling in a reciprocating motion to create a pumping action of the fluid through the pump. 
     In one embodiment of the invention, an improved cam and bearing assembly includes a cam comprising an injected molded plastic cam secured within an inner race of the bearing, such that the cam is fixed relative to the inner race of the bearing, and wherein the cam is coupled to the drive shaft such that it is fixed relative to the drive shaft. An annular wall of the inner race of the bearing includes structure defining one or more notches, wherein the notches and an outer annular wall of the cam are engaged such that the cam is prevented from rotating with respect to the inner race of the bearing. Further, wherein an outer first face and an outer second face of the cam include an annular retaining lip, the annular retaining lip abutting a corresponding outer face of the inner race of the bearing, wherein the retaining lip prevents the cam from lateral movement with respect to the inner race of the bearing. 
     Additionally or alternatively, the wobble plate is injection molded over an outer race of the bearing such that the wobble plate is rotationally and laterally fixed relative to the outer race. In this embodiment, the outer race of the bearing includes structure defining one or more dimples, wherein an inner annular wall of the wobble plate and the dimples are engaged such that the wobble plate is prevented from rotating with respect to the outer race of the bearing. 
     A face of the inner race of the bearing optionally comprises structure defining sockets for positioning and releasably securing the cam and bearing assembly within a wobble plate mold for injection molding of the wobble plate. At least one of a first edge and a second edge of an inner annular wall of the wobble plate includes a retaining lip, and wherein the retaining lip abuts a corresponding outer face of the outer race of the bearing such that is wobble plate is laterally fixed with respect to the outer race of the bearing. 
     An improved wobble plate and bearing assembly according to embodiments of the invention includes a bearing presenting an outer race and an inner race, and a plastic wobble plate presenting a center ring for receiving a bearing within, and a plurality of piston structures extending radially from the center ring, wherein the wobble plate secured to the outer race of the bearing by injection molding such that the wobble plate is fixed in both lateral and rotational movement with respect to the outer race. The bearing includes structure defining one or more dimples, wherein an inner annular wall of the center ring of the wobble plate and the dimples are engaged such that the wobble plate is prevented from rotating with respect to the outer race of the bearing. A face of the inner race of the bearing comprises structure defining sockets for positioning and releasably securing the bearing within a wobble plate mold for injection molding of the wobble plate. 
     In one embodiment, at least one of a first edge and a second edge of an inner annular wall of the center ring of the wobble plate includes a retaining lip. The retaining lip abuts a corresponding outer face of the outer race of the bearing such that is wobble plate is laterally fixed with respect to the outer race of the bearing. 
     The wobble plate and bearing assembly further includes a cam comprising an injected molded plastic is secured within the inner race of the bearing, such that the cam is fixed in both lateral and rotational movement relative to the inner race of the bearing. An annular wall of the inner race of the bearing includes structure defining one or more notches, wherein the notches and an outer annular wall of the cam are engaged such that the cam is prevented from rotating with respect to the inner race of the bearing. Further, at least one of an outer first face and an outer second face of the cam include an annular retaining lip, the annular retaining lip abutting a corresponding outer face of the inner race of the bearing, wherein the retaining lip prevents the cam from lateral movement with respect to the inner race of the bearing. 
     According to some embodiments of the invention, a valve assembly for a diaphragm pump includes a valve housing presenting a first side and a second side, the first side including a plurality of chambers, wherein each chamber includes structure defining an inlet valve seat, plurality of inlet apertures, and a plurality of outlet apertures, and the second side including structure defining a plurality of outlet valve seats. An inlet valve is positioned within an inlet valve seat of each chamber of the plurality of chambers, such that the inlet valve selectively seals the plurality of inlet apertures of the chamber. An outlet valve is positioned in each outlet valve seat of the valve housing such that the outlet valve selectively seals the plurality of outlet apertures of one chamber. 
     Each of the inlet valves and the outlet valves include a mounting portion or post for mounting the valve in a corresponding valve seat, and a resilient portion surrounding an end of the mounting portion, the resilient portion being adapted for selectively sealing corresponding inlet or outlet apertures of a chamber. The resilient portion includes a center section and an outer sealing portion, wherein the outer sealing portion includes a rounded sealing surface such that an effective sealing area of the valve comprises a band, rather than the thin line formed by the prior art valves. 
     In one embodiment, valve housing comprises five chambers, and one inlet valve seat within each chamber. The second side of the valve housing comprises five outlet valve seats, and wherein each outlet valve seat overlaps a portion of two chambers. 
     Each inlet valve seat comprises structure defining a mounting aperture, and wherein the mounting portion of an inlet valve comprises a post, the post forming an interference fit with the mounting aperture to secure the inlet valve within the inlet valve. Each outlet valve seat comprises structure defining a valve mounting recess for receiving a post of an outlet valve. The outlet valve is secured radially (or laterally) by insertion of the post into the valve mounting recess of the outlet valve seat. The outlet valve is then additionally secured axially (or vertically) by a post extending from an inside surface of the outlet chamber of the top cover. 
     The above summary of the invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description that follow more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the present invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is a top perspective sectional view of a cam and bearing assembly according to the prior art. 
         FIG. 2  is a top perspective sectional view of a bearing and wobble plate assembly according to the prior art. 
         FIG. 3A  is a top view of an inlet valve according to the prior art. 
         FIG. 3B  is a cross-sectional view taken at  3 B- 3 B of  FIG. 3A . 
         FIG. 4A  is a cross-sectional view of the inlet valve of  FIG. 3B  in a valve seat. 
         FIG. 4B  is a cross-sectional view of the inlet valve of  FIG. 3B  in a valve seat. 
         FIG. 4C  is a cross-sectional view of the inlet valve of  FIG. 3B  in a valve seat. 
         FIG. 5A  is a top view of an outlet valve according to the prior art. 
         FIG. 5B  is a cross-sectional view taken at  5 B- 5 B of  FIG. 5A . 
         FIG. 6A  is a cross-sectional view of the outlet valve of  FIG. 5B  in a valve seat. 
         FIG. 6B  is a cross-sectional view of the outlet valve of  FIG. 5B  in a valve seat. 
         FIG. 7A  is a diaphragm pump according to an embodiment of the invention. 
         FIG. 7B  is an exploded view of the diaphragm pump according to  FIG. 7A . 
         FIG. 8  is a top perspective view of an interior of a front cover of the diaphragm pump of  FIG. 7A  according to an embodiment of the invention. 
         FIG. 9A  is a top view of a first side of a valve housing according to embodiment of the invention. 
         FIG. 9B  is a top view of a second side of the valve housing of  FIG. 9A . 
         FIG. 10A  is a top view of the first side of the valve housing of  FIG. 9A  with inlet valves mounted therein. 
         FIG. 10B  is a top view of the second side of the valve housing of  FIG. 9B  with outlet valves mounted therein. 
         FIG. 11  is a cross-sectional plan view of the diaphragm pump of  FIGS. 7A and 7B . 
         FIG. 12  is a top perspective sectional view of a cam and bearing assembly according to an embodiment of the invention. 
         FIG. 13  is a top perspective view of a bearing according to an embodiment of the invention. 
         FIG. 14A  is a first half of a cam mold according to an embodiment of the invention. 
         FIG. 14B  is a second half of the cam mold of  FIG. 14A . 
         FIG. 15  is the first half and second half of the cam mold of  FIGS. 14A and 14B  sealed together. 
         FIG. 16  is a top perspective sectional view of a wobble plate and bearing assembly according to an embodiment of the invention. 
         FIG. 17  is a top perspective view of the cam and bearing assembly of  FIG. 12 . 
         FIG. 18A  is a front view of a first half of a wobble plate mold according to an embodiment of the invention. 
         FIG. 18B  is a front view of the first half of the wobble plate mold of  FIG. 18A  with a cam and bearing assembly secured therein. 
         FIG. 19  is the first half and second half of the wobble plate mold of  FIGS. 18A and 18B  sealed together. 
         FIG. 20 a    is a top view of an inlet valve according to an embodiment of the invention. 
         FIG. 20 b    is a cross-sectional view of the inlet valve of  FIG. 20 a    at  20   a - 20   a.    
         FIG. 21 a    is a cross-sectional view of the inlet valve of  FIG. 20 b    in a valve seat. 
         FIG. 21 b    is a cross-sectional view of the inlet valve of  FIG. 20 b    in a valve seat depicting a mold parting line. 
         FIG. 22 a    is a top view of an outlet valve according to an embodiment of the invention. 
         FIG. 22 b    is a cross-sectional view of the outlet valve of  FIG. 22 a    at  22   a - 22   a.    
         FIG. 23 a    is a cross-sectional view of the inlet valve of  FIG. 22 b    in a valve seat. 
         FIG. 23 b    is a cross-sectional view of the inlet valve of  FIG. 22 b    in a valve seat depicting a mold parting line. 
         FIG. 24  is a cross-sectional view of the outlet valve of  FIG. 5A . 
     
    
    
     While the present invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the present invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring to  FIGS. 7A-7B , a diaphragm pump  100  generally comprises a two part casing including a front cover  102  and a back cover  104 , back cover  104  coupled to or housing a motor assembly  106 . Optionally, diaphragm pump  100  can comprise a mounting mechanism  107 , such as a pedestal, legs, or mounting bracket, for securing or positioning diaphragm pump  100  on a surface. 
     Referring to  FIG. 8 , front cover  102  has an inlet port  108  and an outlet port  110 . Inlet port  108  is connectable to an inlet fluid line (not shown) and outlet port  110  is connectable to an outlet fluid line (not shown). Inlet and outlet ports  108 ,  110  are each provided with fittings for connection to the inlet and outlet lines. Inlet port  108  and outlet port  110  each lead to a mutually exclusive inlet chamber  112  and outlet chamber  114 . In one embodiment, an outlet chamber  114  is provided in a central area of front cover  102  and is defined by wall surround  118  in fluid communication with outlet port  110 . Outlet chamber  114  further comprises an inner surface or floor  116 , having one or more posts  113   a - 113   e  extending axially therefrom. Posts  113  are adapted to abut or press against an outer surface of outlet valves seated in a valve assembly positioned adjacent front cover  102 , as described in more detail infra. Generally, the number and location of posts  113  correspond to the number and location of outlet valve seats of the valve assembly. 
     Inlet chamber  112  surrounds outlet chamber  114  and is defined space between wall surround  118  and a sidewall of front cover  102 . Inlet chamber  112  is in fluid communication with inlet port  108 . One of ordinary skill in the art would recognize that alternative configurations are possible so long as the inlet port  108  is in fluid communication with the inlet chamber  112 , the outlet port  110  is in fluid communication with the outlet chamber  114 , and the inlet chamber  112  is separate from the outlet chamber  114  such that the inlet chamber  112  and the outlet chamber  114  are not directly in fluid communication with one another. 
     Motor assembly  106  can comprise, for example, an electric motor (not shown) having a drive shaft  122  that extends through back cover  104 . A cam  124  is coupled to drive shaft  122  of motor assembly  106 , and does not rotate relative to drive shaft  122 , but rather with drive shaft  122 . Cam  124  is then coupled to a wobble plate  128  via a ball bearing  126 . Specifically, cam  124  is coupled directly to an inner race  125  of bearing  126  such that the cam  124  is prevented from rotating relative to inner race  125  of bearing  126 . A cam/bearing assembly  200  is discussed in more detail infra. 
     An outer race  127  of bearing  126  is then coupled directly to wobble plate  128  to form wobble plate/bearing assembly  300  depicted in  FIG. 16 . Specifically, wobble plate  128  comprises structure defining a central boss  130  for receiving cam/bearing assembly  200  therein. The connection between outer race  127  of bearing  126  and wobble plate  128  is such that cam/bearing assembly  200  is stopped from pulling out of wobble plate  128 , and to prevent wobble plate  128  from rotating relative to outer race  127  of bearing  126 . Wobble plate/bearing assembly  300  is described in more detail infra. 
     Wobble plate  128  comprises a plurality of piston sections  132  formed on a first face  131  of wobble plate  128  such that each piston section  132  extends from first face  131  of wobble plate  128 . In one exemplary embodiment of the invention as depicted in  FIG. 16 , wobble plate  128  comprises five piston sections  132   a - 132   e . However, one of ordinary skill in the art would recognize that fewer or more than five piston sections are contemplated. 
     A one-piece diaphragm  134  made from a resilient material, such as rubber, is secured by conventional fastening means (e.g. screws) to first face  131  of wobble plate  128 . Diaphragm  134  can be relatively planar, or can comprise a plurality of piston structures  136  that fit over corresponding piston sections  132  of wobble plate  128 . In one embodiment, piston structures  136  comprise convolutes. 
     A valve assembly  138  is sandwiched between front cover  102  and diaphragm  134 . Valve assembly  138  generally comprises a valve housing  140 , a plurality of inlet valves  142  secured to a first side  141  of valve housing  140 , and a plurality of outlet valves  144  secured to a second, opposite side  143  of valve housing  140 . Referring to  FIG. 9A , first side  141  of valve housing  140  comprises a plurality of chambers  146 , the number of chambers  146  corresponding to the number of piston sections  132  of wobble plate  128 . In one exemplary embodiment of the invention as depicted in the figures, valve housing  140  comprises five chambers  146 . 
     Each chamber  146  includes an upper section  148 , and a lower section  150 . Upper section  148  is preferably rounded, and lower section  150  is preferably tapered such that an outer periphery of each chamber  146  is teardrop- or egg-shaped. However, each chamber  146  can take any other shape desired, including, without limitation, round, rectangular, elongated, or irregular shapes. 
     Upper rounded section  148  comprises structure defining an inlet valve seat  152  for positioning an inlet valve  142  thereon. Inlet valve seat  152  includes a plurality of inlet apertures  154  extending therethrough creating fluid communication between the corresponding chamber  146  and inlet chamber  112  of front cover  102 . Inlet apertures  154  can be any suitable shape, including, but not limited to, round, elongated, or oval-shaped. Upper rounded section  148  further comprises a valve mounting aperture  156  for receiving a central mounting section  158  or post of an inlet valve  142  for securing inlet valve  142  thereto. 
     Inlet valve  142  is preferably positioned within inlet valve seat  152  such that fluid is allowed to enter a corresponding chamber  146  from inlet chamber  112  through inlet apertures  154 , but fluid cannot exit chamber  146  through inlet apertures  154 . More specifically, a peripheral relief zone  160  or lip of inlet valve  142  covers inlet apertures  154  when inlet valve  142  is seated in valve seat  152  of each chamber  146 . Inlet valve  142  is shiftable between an opened position such that peripheral relief zone  160  is significantly flexed or lifted out of the seat to allow fluid flow from inlet chamber  112  to a corresponding chamber  146  of valve housing  140  through inlet apertures  154 , and a sealed position such that fluid flow is restricted or completely prevented through inlet apertures  154  such that there is no fluid communication between inlet chamber  112  and each chamber  146 . The design of inlet valves  142  is described in further detail infra. 
     Second side  143  of valve housing  140  comprises a central output region  158  defined at a periphery by a recessed track  160  corresponding in shape to wall surround  118  of front cover  102  such that wall surround  118  fits in mating relationship with recessed track  160 . In one embodiment of the invention, recessed track  160  comprises a pentagon-shaped track having five sides, corresponding to a pentagon-shaped wall surround  118  defining outlet chamber  114  of front cover  102 . Central output region  158  is surrounded by external surfaces of upper portions  148  of chambers  146  in fluid communication with inlet chamber  112  of front cover  102 . 
     Within central output region  158 , second side  143  of valve housing  140  comprises a plurality of outlet valve seats  162  for positioning an outlet valve  144  thereon. The number of outlet valve seats  162  corresponds with the number of chambers  146 . In one exemplary embodiment shown in  FIG. 9B , second side  143  of valve housing  140  comprises five outlet valve seats  162   a - 162   e . Outlet valve seats  162  are offset from chambers  146  of first side  141  such that each outlet valve seat  162  extends between or straddles two chambers  146 . 
     Outlet valve seat  162  includes a plurality of outlet apertures  164 . Outlet apertures  164  can be any suitable shape, including, but not limited to, round, elongated, or oval-shaped. Each outlet aperture of a plurality of outlet apertures  164  extends through valve housing  140  such that each outlet aperture  164  is in selective fluid communication with a lower portion  150  of a single chamber  146 . 
     Outlet valve seat  162  further comprises structure defining a valve recess  66  for receiving a central mounting section  168  or post of an outlet valve  144  for radially (or laterally) securing outlet valve  144  thereto. In one embodiment, valve recess  66  does not extend entirely through valve housing  140 . Outlet valve  144  is additionally secured axially (or vertically) by abutment with post  113  extending from floor  116  of outlet chamber  114  of front cover  102 , as depicted in  FIG. 24 . 
     Outlet valve  144  is preferably positioned within outlet valve seat  162  such that fluid is allowed to exit a corresponding chamber  146  through outlet apertures  164  to outlet chamber  114  of front cover  102 , but fluid cannot enter the corresponding chamber  146  of valve housing  140  through outlet apertures  164 . More specifically, a peripheral relief zone  170  or lip of outlet valve  144  covers only outlet apertures  164  of an outlet seat  162  in which it is mounted. Outlet valve  144  is shiftable between an opened position such that peripheral relief zone  170  is significantly flexed or lifted out of the seat to allow fluid flow from a corresponding chamber  146  of valve housing  140  through which outlet apertures  164  extend and outlet chamber  114  of front cover  102 , and a sealed position such that fluid flow is restricted or completely prevented through outlet apertures  164  such that there is no fluid communication between the corresponding chamber  146  and the outlet chamber  114 . The design of outlet valves  144  is described in further detail infra. 
     During pump operation, drive shaft  122  of motor assembly  106  rotates. Cam  124  acts as an eccentric, converting rotational movement of drive shaft  122  of motor assembly  106  to push-pull motion of a piston. More specifically, cam  124  creates an offset motion of wobble plate  128  such that a piston section  132  of wobble plate  128  forces a piston structure  136  of diaphragm  134  into and out of a chamber  146  of valve housing  140 . Upper section  148  of each chamber  146  of valve housing  140  is sized to receive a corresponding piston section  132  of wobble plate  128  and piston structure  136  of diaphragm  134 . The combination of piston sections  132  of wobble plate  128 , diaphragm  134 , and the fluid present in chamber  146  create a piston for reciprocating action within chamber  146 , thereby forming a chamber/piston relationship. 
     Fluid is introduced into inlet chamber  112  of front cover  102  via inlet port  108 . During an intake stroke, or retraction of a piston from chamber  146 , a pressure in chamber  146  of valve housing  140  decreases such that inlet valve  142  opens and fluid is forced into chamber  146  from inlet chamber  112  of front cover  102  through inlet apertures  154 . During a discharge stroke, or entry of the piston into chamber  146 , the pressure in chamber  146  increases over a pressure in outlet chamber  114  to force outlet valve  144  open such that fluid is forced out of chamber  146  into outlet chamber  114  of front cover  102  via outlet apertures  164 , and ultimately out of outlet chamber  114  via outlet port  110 . Due to the offset camming action of the cam/bearing assembly  200  and wobble plate  128  relationship, wobble plate  128  is subject to nutating motion, causing reciprocating action of pistons of diaphragm sequentially into and out of chambers  146  of valve housing  140  to provide a pumping action. 
     As discussed in the Background section, a common failure for conventional diaphragm pumps is loosening of the cam in the bearing, and/or the bearing loosening in the wobble plate. This can significantly reduce the operation hours of a pump and/or the flow volume. 
     According to one embodiment of the invention, as depicted in  FIG. 12 , an improved cam/bearing assembly  200  comprises a plastic cam  202  formed directly into inner race  204  of bearing  206  by injection molding. Cam  202  comprises an annular retaining lip  208   a ,  208   b  on both a first face  210  and a second face  212 . First retaining lip  208   a  of first face  210  abuts a first outer face  214   a  of inner race  204  of bearing  206 , and second retaining lip  208   b  abuts a second outer face  214   b  of inner race  204  of bearing  206  to prevent cam  202  from pulling out of bearing  206 . One or more notches  216  are machined into an edge of annular wall  218  of inner race  204  of bearing  206  so that the plastic material of cam  202  flows into notches  216  such that cam  202  is prevented from rotating relative to inner race  204  of bearing  206 . 
     To manufacture cam/bearing assembly  200 , referring to  FIG. 14A-15 , a cam mold  220  having a first half  220   a  and a second half  220   b  is used. First half  220   a  of cam mold  220  includes a recessed portion  222  for positioning and retaining bearing  206  within. Outer race  224  of bearing  206  is used to center bearing  206  in first half  220   a  of mold  220 . Optionally, magnets  226  can be placed within bottom wall  228  and/or annular side wall  230  of recessed portion to aid in retaining bearing  206  within first half  220   a  of mold  220 . First half  220   a  further includes a center post for forming a central bore of cam  202 . Center post  232  can include a rounded section  234  and a flat section  236  to form eccentric central bore of cam  202  for creating nutating action in wobble plate  302 . A plurality of ribs  238  surrounds center post  232  for forming a plurality of apertures  240  in a first face  210  of cam  202 . 
     Second half  220   b  of mold  220  includes a recessed portion  242  for accommodating bearing  206 , and a center recessed section  244  for accommodating center post  232  of first half  220   a  of mold  220 . Center recessed section  244  is of a sufficient depth such that an end of center post  232  abuts center recessed section  244  such that central bore of cam  202  is formed and extends through an entire depth of cam  202 . Second half  220   b  also includes plurality of ribs  246  surrounding center recessed section  244  for forming a plurality of apertures in second face  212  of cam  202 . 
     Once bearing  206  is positioned in first half  220   a  of mold  220 , first and second halves  220   a ,  220   b  of mold  220  are sealed together as shown in  FIG. 15 . Mold halves  220   a ,  220   b  seal on inner race  204  of bearing  206 . An interior space  248  is defined by inner race  204  of bearing  206  including notches  216  formed on annular wall  218  of inner race  204 , center post  232 , and ribs  238 ,  246  of both first and second half  220   b  of mold  220 . Second half  220   b  of mold  220  includes a gate  250  for plastic injection. Molten plastic material is injected into interior space  248  of mold  220  to form cam  202 . Upon cooling of the plastic material, mold  220  halves are unsealed, and cam/bearing assembly  200  is ejected from mold  220 . 
     Referring to  FIGS. 16 and 17 , cam/bearing assembly  200  is used to further create wobble plate/bearing assembly  300 . Wobble plate/bearing assembly  300  comprises cam/bearing assembly  200  described above, and a plastic wobble plate  302  formed around cam/bearing assembly  200  by injection molding. Wobble plate  302  includes an annular ring  304  having a central bore  314  for receiving and retaining cam/bearing assembly  200  therein, structure defining a plurality of apertures  308  extending through annular ring  304 , and a plurality of piston sections  310  extending from annular ring  304 . Each piston section  310  includes a ring section  312  and a central bore  314  for receiving and securing diaphragm  134  thereon. As discussed above, piston section  310   a  drives corresponding piston structure  136  of diaphragm  134  into and out of corresponding chamber  146  of valve housing  140  to form a piston/chamber relationship for reciprocating pumping action. 
     An outer race  224  of bearing  206  of cam/bearing assembly  200  is machined with one or more dimples  316  such that plastic material forming wobble plate  302  flows into dimples  316  to prevent cam/bearing assembly  200  from pulling out of wobble plate  302 , and to prevent wobble plate  302  from rotating relative to outer race  224  of bearing  206 . 
     To manufacture wobble plate/bearing assembly  300 , and referring to  FIGS. 18A-19 , a wobble plate mold  318  having a first half  318   a  and a second half  318   b  is used. First half  318   a  of wobble plate mold  318  includes a recessed portion  320  for positioning and retaining cam/bearing assembly  200  within. Pegs  322  formed on a bottom face  324  of recessed portion  320  correspond with sockets  326  machined on a face of inner race  204  of bearing  206  to form a mating relationship to aid in positioning cam/bearing assembly  200  in center of wobble plate  302 . Recessed portion  320  surrounds and defines a center cavity  328  for isolating cam  202  so that cam  202  does not interfere with the tooling of mold  318 . Optionally, magnets or a magnetic strip  330  can be placed within a portion of bottom wall and/or annular side wall of recessed portion  320  to aid in retaining bearing  206  within first half  318   a  of mold  318 . 
     First half  318   a  further includes a plurality of posts  332  for forming central bore  314  of each piston section  310  of wobble plate  302 . In one embodiment as shown, each post  332  can include a rounded section  334  and a concave section  336 , or any of a variety of shapes to form the desired piston section. One or more ribs  338  are positioned between each piston section  310  for forming a plurality of apertures  308  in ring section  312  of wobble plate  302 . 
     Second half  318   b  of mold  318  includes a recessed portion  340  for accommodating bearing  206 , and a center cavity  328  for isolating cam  202  as described above. 
     Once bearing  206  is positioned in first half  318   a  of mold  318 , first and second halves  318   a ,  318   b  of mold  318  are sealed together as shown in  FIG. 19 . Mold halves seal on outer race  224  of bearing  206 . An interior space  341  is defined by outer race  224  of bearing  206  including dimples formed on outer race  224 , posts, and ribs of first half  318   a  of mold  318 . A depth of recessed portion for bearing  206  is slightly shallower than a depth of interior space such that an inner wall of ring section of wobble plate  302  creates a slight overlap or lip  342  abutting an outer most edge of each face of outer race  224  of bearing  206  to further secure wobble plate  302  to cam/bearing assembly  200 . 
     Second half  318   b  of mold  318  includes a gate  344  for plastic injection for each piston section of wobble plate  302 . Molten plastic material is injected into the interior space  341  of mold  318  to form wobble plate  302 . Upon cooling of the plastic material, mold halves  318   a ,  318   b  are unsealed, and wobble/plate bearing assembly  300  is ejected from mold  318 . 
     As discussed in the Background Section, prior art inlet and outlet valves, as depicted in  FIGS. 3A-6B , have limited effective sealing area when placed in the valve seat of the valve housing  140 . 
     Referring to  FIGS. 20A-21B , an improved inlet valve  142  is depicted. Inlet valve  142  comprises a one-piece construction molded from a suitable material, such as rubber. Inlet valve  142  includes a central mounting section  158 , such as a post, and a resilient, seal-forming section  159  surrounding post  158  at a first end of post  158 . Post  158  further includes a longitudinal middle section  163  having a constant diameter D mi , and a second, opposing end  165  of the post  158  receivable within a bore of a chamber  146  of valve housing  140 . Second opposing end  165  of the post  158  includes a tapered section  167  having a first diameter greater than a constant diameter of middle section, and tapering to a diameter equal to or less than the constant diameter of the middle section. The first diameter thereby creates a shoulder surrounding an end of middle section, for abutment against an opposite side of the valve housing  140  when the post  158  is passed through the bore. This ensures that inlet valve  142  remains in position in valve housing  140  during operation. 
     Referring to  FIGS. 21A and 21B , inlet valve  142  is depicted being mounted in a valve seat  152  of a chamber  146  of the valve housing  140 . Resilient portion  159  includes a center section  169  and a peripheral relief zone  160  or lip. A first edge  160   a  of the peripheral relief zone  160  is shown in the relaxed position, i.e. how the valve naturally lies prior to being assembled within the valve seat, while a second edge  160   b  is shown in the slightly flexed or sealed position, i.e. when the piston of the diaphragm is moving into the chamber  146  in which inlet valve  142  is mounted such that fluid flow is restricted or completely prevented. Inlet valve  142  is in an opened position when peripheral relief zone  160  is significantly flexed such that it is lifted out of valve seat  152  to allow fluid flow from inlet chamber  112  to chamber  146 . 
     Removal of material forming the “stepped” portion in the prior art valve results in a diminishing cross section from central section  169  to peripheral relief zone  160  such that peripheral relief zone  160  includes a rounded or sloped portion  171  on a first side of resilient portion  159 , and having a mathematical or cross-sectional profile comprising a continuous function, and a second rounded or sloped sealing or seating portion  177  on a second side of resilient portion  159 , second seating portion  177  also having a mathematical or cross-sectional profile comprising a continuous function. This rounded or sloped edge surface design slightly flexes to form a band of sealing area, as opposed to a line, thereby creating larger effective sealing area  173  than the prior art inlet valve, reducing sealing inconsistencies. This effective sealing area  173  is bounded by a first circumference  173   a , i.e. a circumference at an innermost radial location where peripheral relief zone  160  makes contact with the valve seat, and a second circumference  173   b , i.e. a circumference at an outermost radial location of peripheral relief zone  160  where the valve makes contact with the valve seat. The circumferential band or ring extending between first and second circumferences  173   a ,  173   b  is effective sealing area  173 . 
     Furthermore, referring to  FIG. 21B , the rounded edge design moves the mold parting line  175  of the mold in manufacturing to a non-critical area of the valve that has no effect on sealing performance, thereby reducing or eliminating further sources of sealing inconsistencies. 
     Referring to  FIGS. 22A-22B , an improved outlet valve  144  is depicted. Outlet valve  144  comprises a one-piece construction molded from a suitable material, such as rubber. Outlet valve  144  includes a central mounting section  168 , such as a post, a resilient, seal-forming section  169  surrounding post  168  at a first end  168   a  of post  168 , and a second post  189 . Post  168  further includes a longitudinal middle section  175  having a constant diameter D mo , and a second, opposing end  168   b  of post  168  receivable within a recess  166  formed in an exterior of valve housing  140 . Middle section  175  of post  168  radially (or laterally) secures outlet valve  144  within recess  166 , and post  113  extending from floor  116  of outlet chamber  114  of top cover  102  abuts or presses against second post  189  of outlet valve  144  to additionally axially (or vertically) secure outlet valve  144  to ensure that outlet valve  144  remains in position in the valve seat  162  during operation of the pump. 
     Optionally, second opposing end  168   b  of post  168  includes a tapered section  179  having a first diameter equal to the constant diameter of middle section  175 , and tapering to a diameter less than the constant diameter of middle section  175 . 
     Referring to  FIGS. 23A, 23B, and 24 , outlet valve  144  is depicted being mounted in a valve seat  162  on an exterior of a chamber  146  of the valve housing  140 . Resilient portion  169  includes a center section  181  and a peripheral relief zone  170  or lip. Lip  170  is shown in the slightly flexed or sealed position, i.e. when the piston of the diaphragm is moving out of the chamber  146  on which the outlet valve  144  is mounted such that fluid flow is restricted or completely prevented. Outlet valve  144  is in an opened position when peripheral relief zone  170  is significantly flexed such that it is lifted out of valve seat  162  to allow fluid flow from chamber  146  to outlet chamber  114 . Removal of an annular section of material forming the “stepped” portion in the prior art valve results in a thinner cross section of material near peripheral relief zone  170 , and includes a rounded edge or sloped seating portion  183  on an interior surface of resilient portion  169 , and having a mathematical or cross-sectional profile comprising a continuous function. This rounded or sloped edge surface design flexes to form a band of sealing area, as opposed to a line, thereby creating larger effective sealing area  185  than the prior art outlet valve, reducing sealing inconsistencies. This effective sealing area  185  is bounded by a first circumference  185   a , i.e. a circumference at an innermost radial location where peripheral relief zone  170  makes contact with the valve seat, and a second circumference  185   b , i.e. a circumference at an outermost radial location of peripheral relief zone  170  where the valve makes contact with the valve seat. The circumferential band or ring extending between first and second circumferences  185   a ,  185   b  is effective sealing area  185 . 
     Furthermore, referring to  FIG. 23B , the rounded edge design moves the mold parting line  187  of the mold in manufacturing to a non-critical area of the valve that has no effect on sealing performance, thereby reducing or eliminating further sources of sealing inconsistencies. 
     The combination of improved inlet and outlet valve designs improves the function and efficiency of the pump because of larger effective sealing areas, and reduced sealing inconsistencies. 
     An improved diaphragm pump according to embodiments of the invention generally includes the cam and bearing assembly and the wobble plate and bearing assembly that can withstand the loads placed thereon, thereby eliminating or reducing the dislocation of either the cam from the bearing, or the wobble plate from the bearing. This acts to increase the pump operating time and reliability from the prior art pumps up to ten times or more. In addition to or alternatively to, the improved design of both the inlet and outlet check valves of the valve housing creates better sealing consistency by increasing the effective sealing area with the valve seat. This also increases the efficiency of the pump because it eliminates or reduces the occurrence of leaks and/or backflow, while maintaining high flow efficiency through the pump. 
     The foregoing descriptions present numerous specific details that provide a thorough understanding of various embodiments of the invention. It will be apparent to one skilled in the art that various embodiments, having been disclosed herein, may be practiced without some or all of these specific details. In other instances, components as are known to those of ordinary skill in the art have not been described in detail herein in order to avoid unnecessarily obscuring the present invention. It is to be understood that even though numerous characteristics and advantages of various embodiments are set forth in the foregoing description, together with details of the structure and function of various embodiments, this disclosure is illustrative only. Other embodiments may be constructed that nevertheless employ the principles and spirit of the present invention. Accordingly, this application is intended to cover any adaptations or variations of the invention. 
     For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.