Abstract:
A positive displacement pump for gases includes a pair of pistons operating out of phase. Each of the pistons is associated with a plurality of rotary inlet valves disposed along the sidewalls of the piston cylinders. A rotary outlet valve is also associated with each piston and includes a rotating valve body disposed transversely across the cylinder head and which rotates in synchronism to open a through, radial port in the member in timed relationship to the piston travel. The positive displacement pump finds particular application heating, cooling and ventilating applications.

Description:
CROSS REFERENCE TO CO-PENDING APPLICATION 
     This patent application is a continuation-in-part of U.S. Pat. Ser. No. 09/239,120 filed Jan. 28, 1999, now U.S. Pat. No. 6,200,111 granted Mar. 13, 2001 which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to positive displacement pumps for gases and more specifically to a positive displacement pump having a pair of pistons operating out of phase and specially configured rotary inlet and outlet valves. 
     Positive displacement pumps for liquids and gases typically include one or more piston and cylinder assemblies and associated inlet and outlet valves which control the flow of pumped fluid into and out of the cylinders. Such pumps are typically capable of relatively high pressure rise operation. A drawback of such positive displacement pumps is that both the inflow and outflow are distinctly pulsatile in character and, especially with high pressure pumps, the flow rates are generally relatively small. 
     Furthermore, the ability to adjust pressure and flow rates with such pumps can be problematic. Typically, of course, flow rates may be adjusted simply by reducing the speed of the pump. However, such a speed reduction to reduce output flow rate is typically accompanied by a reduction in the output pressure as well. 
     It is apparent from the foregoing that a positive displacement pump which addresses the problems of output pulsation and controllable flow characteristics would represent an improvement over currently available devices. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a high volume, positive displacement pump which provides a flow rate having temporal fluctuations which are a smaller fraction of the time mean value than those of conventional positive displacement pumps and is a higher flow rate, smaller pressure rise device than conventional positive displacement pumps. 
     A positive displacement pump for heating, cooling and ventilating applications includes a pair of pistons operating out of phase which provide pumped fluid to a common output. Each of the pistons is associated with an inlet valve array which includes a plurality of rotary inlet valves arranged along opposed, preferably vertical, sidewalls of the cylinders to control the influx of fluid. A rotary outlet valve is also associated with each piston and includes a rotating valve body disposed transversely across the cylinder head which rotates in synchronism to open a through, radial port in the valve body in timed relationship to the piston travel. A drive motor rotates a crankshaft and cams which control actuation of the inlet and outlet valves. The phase relationship between the operation of the inlet and outlet valves and the respective pistons is fixed. The positive displacement pump finds particular application in heating, ventilating and air conditioning (HVAC) apparatus and applications. 
     Thus it is an object of the present invention to provide a high volume, positive displacement pump. 
     It is a further object of the present invention to provide a positive displacement pump suitable for applications in HVAC apparatus. 
     It is a still further object of the present invention to provide a positive displacement pump wherein rotary inlet and outlet valves operate in synchronism with reciprocating pistons. 
     It is a still further object of the present invention to provide a positive displacement pump wherein the phase relationships of the inlet and outlet valves are fixed relative to the reciprocating pistons. 
     Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred and alternate embodiments and appended drawings wherein like reference numbers refer to the same component, element or feature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top, plan view of a positive displacement pump according to the present invention; 
     FIG. 2 is a side, elevational view in partial section of a positive displacement pump according to the present invention taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a fragmentary, sectional view of an inlet valve and a portion of a positive displacement pump according to the present invention taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a fragmentary, sectional view of outlet valves and a portion of a positive displacement pump according to the present invention taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is a full, sectional view of a positive displacement pump according to the present invention taken along line  5 — 5  of FIG. 2; and 
     FIG. 6 is a diagrammatic view of a positive displacement pump in an HVAC application. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now FIGS. 1 and 2, a high volume, positive displacement pump according to the present invention is illustrated and generally designated by the reference number  10 . The positive displacement pump  10  includes a housing  12  which is preferably cast metal and includes various apertures, surfaces and ports which cooperate with other features of the invention. Specifically, the positive displacement pump  10  includes an upper or first piston and cylinder assembly  14 A and a lower or second piston and cylinder  14 B. The upper piston and cylinder assembly  14 A and the lower piston and cylinder assembly  14 B are substantially identical and the upper piston and cylinder assembly  14 A includes a first preferably rectangular piston  16 A disposed within a complementary first rectangular cylinder  18 A defined by a first rectangular cylinder wall  20 A. 
     The piston  16 A includes a first clevis  22 A which receives a connecting rod  24 A which is pinned to the clevis by a retaining pin  26 A. The first connecting rod  24 A is in turn pivotally received on a first eccentric crank  32 A of an first crankshaft  34 A. The first crankshaft  34 A includes a pair of counterbalance members  36 A which receive opposite ends of the crank  32 A. The first crankshaft  34 A is supported for a rotation in a plurality of first bearings  38 A which may be either standard journal bearings or anti-friction devices such as ball bearing assemblies (not illustrated). Secured to the top of the crankshaft  34 A is a first circular cam  42 A. The crankshaft  34 A is driven by a prime mover such as a variable speed electric motor  46  which is supported by and attached to the housing  12  by a mounting yoke  48 . 
     The lower or second piston and cylinder assembly  14 A is in all mechanical respects the same as the upper piston and cylinder assembly  14 A except that it operates 180° out of phase with the first or upper piston and cylinder assembly  14 A. Thus, it includes a second piston  16 B, a second cylinder  18 B, a second cylinder wall  20 B, a second clevis  22 B, a second connecting rod  24 B, a second retaining pin  26 B, a second crank  32 B, a second crankshaft  34 B, second counterbalance members  36 B, second bearings  38 B and a second circular cam  42 B. It will be appreciated that the first crank  32 A and the second crank  32 B are arranged 180° out of phase from one another as illustrated in FIG.  2 . 
     Turning now to FIGS. 1,  2  and  5 , each of the first and second piston and cylinder assemblies  14 A and  14 B includes a respective valve drive assembly  50 A and  50 B. The upper or first valve drive assembly  50 A is disposed on the top of the housing  12  as illustrated in FIG.  1  and the lower or second valve drive assembly  50 B is disposed on the bottom of the housing  12  as illustrated in FIG.  2 . Once again, the upper or first valve drive assembly  50 A and the lower or second valve drive assembly  50 B, but for their locations and the fact that the valves open and close in proper relationship with their associated pistons  16 A and  16 B which are 180° out of phase from one another, are mechanically identical. Hence, only the upper or first valve drive assembly  50 A will be fully described, it being understood that the same description applies to the lower or second valve drive assembly  50 B. 
     The first circular cam  42 A includes a cam profile or track  52 A having a first or high dwell region  54 A coupled to a second or low dwell region  56 A by a relatively steep or rapid rise region  58 A and relatively steep or rapid descent region  60 A. Disposed within the cam track  52  is a cam follower  62 A which is secured to a reciprocating drive member  64 A. The drive member  64 A is supported in a suitable spaced-apart pair of journal or anti-friction bearing assemblies  66 A which are disposed upon the housing  12  and support the member  64 A for reciprocation along its axis. The drive member  64 A is pinned to a drive frame  68 A by a suitable connecting pin  72 A. The drive frame  68 A includes a pair of spaced-apart gear racks  74 A each consisting of a plurality of spur gear teeth along the outer faces of the drive frame  68 A extending parallel to its direction of motion and the drive member  64 A. Engaging the gear racks  74 A on both faces of the drive frame  68 A at multiple locations are a plurality of spur gears  76 A. It will be appreciated that at the bottom of the high volume, positive displacement pump  10  are disposed a second circular cam  42 B having a cam track  52 B as described above, a cam follower  62 B, a reciprocating drive member  64 B, bearing assemblies  66 B and a second drive frame  68 B having spaced apart gear racks (not illustrated). 
     As illustrated in FIGS. 2 and 3, each of the spur gears  76 A is associated with a corresponding spur gear  76 B which is a component of the lower or second valve drive assembly  50 B. Cooperatively, each of the spur gears  76 A and  76 B disposed along each of the drive frames  68 A and  68 B bi-directionally drive and rotate a plurality of rotary valve bodies  80 . Preferably, there are at least eight rotary inlet valve bodies  80 , four on each side of the piston and cylinder assemblies  14 A and  14 B, although more or fewer may be readily utilized in a given positive displacement pump  10 . Each of the rotary inlet valve bodies  80  includes a first pair of preferably rectangular through ports  82 A and a second equal sized pair of rectangular ports  82 B oriented at an angle of 90°to the ports  82 A. Solid portions  84  within the inlet valve body  80  serve to stiffen and strengthen it. The inlet valve bodies  80  are received within circular passageways  86  within the sidewalls  20 A and  20 B of the housing  12  and includes through ports  88 A and  88 B which provides communication from the exterior of the housing  12  into the respective cylinders  18 A and  18 B. 
     The rise region  58 A and the descent region  60 A of the cam track  52  are sized to cause bi-directional translation of the drive frame  60 A sufficient to rotate each of the spur gears  76 A and  76 B exactly  900  such that such rotation bi-directionally rotates each of the valve bodies  80  from a first position wherein the rectangular passageways  82 A in the upper portion of the valve body provide communication to a second position closing off the inlet ports  88  while simultaneously, the rectangular passageways  82 B move from a first position where communication is closed to a second position providing fluid communication to the cylinder  18 B. It will be appreciated that all of the valve bodies  80  rotate in unison to provide the aforementioned fluid flow or communication and inhibition of such fluid flow and that such communication and inhibition is 180° out of phase relative to the two piston and cylinder assemblies  14 A and  14 B. 
     Turning now to FIGS. 1,  2  and  4 , a final pair of upper spur gears  92 A and a final pair of lower spur gears  92 B engage the gear rack  74 A of the drive frame  68 A and the gear rack  74 B of the drive frame  68 B, respectively. The spur gears  92 A and  92 B are identical in size and thus rotational characteristics relative to the spur gears  76 A and  76 B and thus also rotate 90° in response to the reciprocating travel of the drive frames  68 A and  68 B. The spur gears  92 A and  92 B mesh with spur gears  94 A and  94 B, respectively, of the same size and thus effect corresponding rotation thereof. The spur gear  94 A is secured to a stub shaft  96 A which is supported by a journal bearing  98 A. At the end of the stub shaft  96 A opposite the spur gear  94 A is a bevel gear  102 A. The bevel gear  102 A meshes with a second bevel gear  104 A of equal size and is secured to a stub drive shaft  106 A. Accordingly, the stub drive shaft  106 A rotates in synchronism and the same  900  of oscillation as the spur gear  92 A and the spur gears  76 A. The stub shaft  106 A is coupled to or is an extension of a first or upper rotary outlet valve body  110 A. 
     The upper rotary outlet valve body  110 A includes a through rectangular passageway  112 A which extends substantially across the full end face of the piston  16 A. In a first position illustrated in FIG. 2, the upper valve body  110 A, or more properly the rectangular passageway  112 A, provides fluid communication from the interior of the cylinder  18 A to an outlet passageway  114 A and, in a second position, as illustrated with regard to the second rotary outlet valve body  110 B, closes off the outlet passageway  114 B. Once again, the lower piston and cylinder assembly  14 B includes an identical rotary valve body  110 B having a passageway  112 B which communicates with an outlet passageway  114 B. Here, again the difference is only operational in that the valve bodies  110 A and  110 B always rotate out of phase to one another. 
     It should be noted that, as illustrated in FIG. 5, the pistons  16 A and  16 B include labyrinth seals  118  about their peripheries. Such labyrinth seals  118  may take the form of a plurality of adjacent lands and recesses which extend around the pistons  16 A and  16 B. 
     Referring now to FIG. 6, a typical HVAC installation of a high volume, positive displacement pump  10  according to the present invention is illustrated. Attached to the left and right sidewalls of the housing  12  of the pump  10  are ducts or plenums  120  which supply air to the pump  10  in conventional fashion. Attached to the end face of the housing  12  such that the outlet ports  114 A and  114 B merge and communicate with it is an outlet duct  122 . The outlet duct  122  is coupled to, for example, a heat exchanger  124  through which hot or cold media flows in cross-wise or transverse, isolated passageways. Additional plenum or ducting (not illustrated) communicates with an air distribution system in a building, as will be readily understood, and carries the conditioned air thereto. 
     As shown in FIGS. 1 and 2, a positive displacement pump  10  according to the present invention will include an upper piston and cylinder assembly  14 A and a lower piston and cylinder assembly  14 B whose pistons  16 A and  16 B operate 180° out of phase. The two passageways  114 A and  114 B typically deliver fluid to a common outlet. This means that the outflow may be characterized as a d.c. level with a superimposed fluctuation that can be described as (for the first cycle)                  q   net          ∫   0   T       =       q   u            ∫   0     T   /   2              +     q   e            ∫     T   /   2     T                   (   1   )                                
     where T is the reciprocal of the driving frequency (fd) and 
     
       
         ω= f   d /2π.   (2)  
       
     
     Turning then to the operation of the pump, as suggested by equation (1), the upper passageway  114 A will deliver the fluid to be pumped for the time period nT≦t&lt;(2n+1)T/2 and the lower passageway  114 B will deliver fluid during the period (2n+1)T/2≦t&lt;(n+1)T. This delivery is powered by the forward advance of the respective pistons  16 A and  16 B and it is controlled by the angular position (φ) of the rotary outlet valves  110 A and  110 B illustrated in FIG.  1 . 
     It is assumed, for the present discussion, that θ 1 (t) is the linear function: 
     
       
         θ 1 ( t )=ω t    (3)  
       
     
     and that ω=constant. 
     The magnitude of the volume flow rate will be linearly proportional to ω given the condition that the inlet ports  88 A and  88 B are fully filled from the surrounding plenum  120  on each stroke. Given the inertia of the elements involved, the change in flow rate that results from a change in the rotational speed (ω) of the crankshaft  34 A is considered to represent a “slow” change of the operating condition. 
     Industrial Application —HVAC Systems 
     An application for the positive displacement pump  10  is that of air delivery to the heating/cooling coils of an HVAC system. Of concern for such a system is the upstream propagation of flow noise. 
     This concern suggests that the forward (pressurizing) stroke of the pistons  16 A and  16 B be executed relatively faster than the filling (return) stroke. Various mechanical linkages which can execute such drive patterns exist. 
     A concomitant advantage of this mode of operation is that the velocity of air through the heating/cooling coils will be larger than would be the velocity in a symmetric-drive pattern. Specifically, the larger the velocity, the greater will be the momentary heat transfer and the greater will be the time averaged heat transfer for a given area of the heat exchanger  124 . This benefit is in addition to the intrinsic benefit of the positive displacement pump  10  according to the present invention for such heat transfer applications. Specifically, by creating twice the cycle average velocity over one-half of the heat exchanger for one-half of the cycle time, and repeating this behavior for the other one-half of the heat exchanger for one-half of the cycle time, a greater heat transfer will be obtained as enhanced heat transfer will derive from both the larger temperature differences and the larger convection heat transfer properties of the higher speed flow. 
     The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent, however, that methods incorporating modifications and variations will be obvious to one skilled in the art of positive displacement pumps. Inasmuch as the foregoing disclosure presents the best mode contemplated by the inventor for carrying out the invention and is intended to enable any person skilled in the pertinent art to practice this invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.