Patent Publication Number: US-6986640-B2

Title: Motor pump with expansion tank

Description:
FIELD OF THE INVENTION 
     This invention relates to pumps and more particularly to pumps used as part of a closed fluid circuit. 
     BACKGROUND OF THE INVENTION 
     When a fluid is circulated through a closed circuit by means of a pump, it is often necessary to provide a structure or mechanism to accommodate expansion or contraction of the conveyed fluid due to change in temperature which are sufficient to affect the volume of the fluid itself or the capacity of certain components in the circuit. 
     SUMMARY OF THE INVENTION 
     The principal and secondary objects of this invention are to provide a convenient mechanism within a pump to accommodate volumetric variation in the conveyed fluid or other components of a closed fluid circuit and avoid the necessity of providing a structure or mechanism along the fluid circuit to compensate for those variations often caused by change in ambient or internal temperature. 
     These and other objects are achieve by providing within the housing of the pump, a resiliently compressible chamber formed in part by a flexible membrane, which chamber is in contact with, but not accessible to the fluid being conveyed by the pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a first embodiment of a pump with resiliently compressible internal chamber according to the invention; 
         FIG. 2  is a cross-sectional view of a second embodiment of a similar pump; and 
         FIG. 3  is a cross-sectional view of a third embodiment of the pump. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     Referring now to the drawing, there is shown in  FIG. 1 , a spherical pump  1  in which the impeller  2  is secured to the top surface of a hemispherical rotor  3  preferably comprising a permanent magnet. Fluid entering the pump through the inlet  4  is centrifugally directed toward an outlet  5 . An annular stator  6  comprising a soft magnetic yoke  7  and a winding  8  applied to the inner surface of the yoke is separated from the fluid by a watertight septum  9  having a annular portion  10  extending into the air gap  11  between the rotor and the stator. The rotor is immersed in the fluid and supported by a single-ball bearing mounted at the end of a shaft  13  projecting from a medium flat section  14  of the septum, and into an axial cavity  15  in the lower portion of the rotor. 
     A resiliently compressible chamber  16  is positioned against the inside surface of the top wall  17  of the pump enclosure. The chamber comprises a rigid member  18  substantially parallel to the top wall  17  and a circular flexible membrane  19  extending between the periphery of the rigid member  18  and the inside surface of the top wall  17  to form a chamber which is in contact with a fluid-holding area  20  of the pump housing but whose inside  21  is not accessible to the conveyed fluid. An aperture  22  in the inside portion of the wall  17  puts the interior of the chamber in communication with ambient air outside the pump. A series of coil springs  23 ,  24  are compressed between the rigid member  18  and the top wall  17  of the pump enclosure. 
     A plunger  25  inside the chamber has a first end connected to the rigid member  18  and an opposite end having a tip protruding through a window  28  in the top wall of the pump enclosure; whereby the position of the tip  27  provides an approximate indication of the degree of compression or expansion of the chamber. 
     In the second embodiment of the invention  31  illustrated in  FIG. 2 , an annular compressible chamber  32  is formed by a pulley-shaped membrane  33  having both rims  34 ,  35  secured to the inside surface of a lateral wall  36  of the pump housing. A coil spring is coaxially positioned inside the annular chamber  32 . In this particular embodiment, the pump inlet is conveniently positioned coaxially and above the impeller and the propeller is positioned proximal, and axially perpendicularly to the top wall  40  of the enclosure. This second embodiment of the invention allows for a more compact pump housing since a top portion  41  of the impeller is surrounded by the resiliently compressible chamber  32  rather than being located below it as described in connection with the first embodiment of the invention. 
     In the third embodiment of the invention illustrated in  FIG. 3 , a simple barometric bellow  42  is used in a pump similar to the one illustrated in  FIG. 1  in lieu of the resiliently compressible chamber  16 . Such a bellow is commonly found in some types of barometric instruments. 
     While the preferred embodiments of the invention have been described, modifications can be made and other embodiments may be devised without departing from the spirit of the invention and the scope of the appended claims.