Abstract:
A pump for moving a liquid including a rotor rotatable within a housing and slidable relative to the housing between a first axial rotor position during normal pump operation and a second axial rotor position during a pump inoperative condition.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a Continuation of Applicant&#39;s U.S. patent application Ser. No. 11/017,797, filed on Dec. 22, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a pump used for pumping a liquid.  
       BACKGROUND OF THE INVENTION  
       [0003]     Electrically driven helix-type pumps are known. Permanent magnet pumps are also known. For example, a centrifugal blood pump is disclosed in U.S. Pat. No. 5,049,134 and an axial blood pump is disclosed in U.S. Pat. No. 5,692,882. In general, these and other helix pumps rely on friction or fluid dynamic lift to move fluid axially though the pump. That is, although the helix rotates, the liquid is rotationally relatively stationary as it moves axially along the length of the pump. While perhaps suited for pumping blood and other low speed and low pressure application, these devices are unsuitable for other environments, particularly where high speed and high pressures are desired. Room for improvement is therefore available.  
       SUMMARY OF THE INVENTION  
       [0004]     One object of the present invention is to provide an improved pump.  
         [0005]     In accordance with one aspect of the present invention, there is provided a pump having at least one inlet and one outlet for use in a liquid circulation system, the liquid having a dynamic viscosity, the circulation system in use having a back pressure at the pump outlet, the pump comprising a rotary rotor and a stator providing first and second spaced-apart surfaces defining a generally annular passage therebetween, the passage having a central axis and a clearance height, the clearance height being a radial distance from the first surface to the second surface, the rotor in use adapted to rotate at a rotor speed, at least one thread mounted to the first surface and extending helically around the central axis at a thread angle relative to the central axis, the thread having a height above the first surface and a thread width, the thread height less than the clearance height, the thread width together with a thread length providing a thread surface area opposing the second surface, wherein the rotor, in use, rotates at a rotor speed relative to the stator which results in a viscous drag force opposing rotor rotation, said drag force caused by shearing in the liquid between the thread and first surface and the second surface, the viscous drag force having a corresponding viscous drag pressure, wherein the thread height, thread surface area and thread angle are adapted through their sizes and configurations to provide a viscous drag pressure substantially equal to the back pressure, and wherein the clearance height is sized to provide for a non-turbulent liquid flow between the first and second surfaces.  
         [0006]     In another aspect, the present invention provides a method of sizing a pumping system, the system including at least one pump and a circulation network for circulating a liquid having a dynamic viscosity, the circulation system having a back pressure at an outlet of the pump, the pump having a rotary rotor and a stator providing first and second spaced-apart surfaces defining a generally annular passage therebetween, the passage having a central axis and a clearance height, the clearance height being a radial distance from the first surface to the second surface, the rotor in use adapted to rotate at a rotor speed, at least one thread mounted to the first surface and extending helically around the central axis at a thread angle relative to the central axis, the thread having a height above the first surface and a thread width, the method comprising the steps of determining the back pressure for a desired system configuration and a given liquid, dimensioning pump parameters so as to provide a non-turbulent flow in the passage during pump operation, selecting thread dimensions to provide a drug pressure in response to rotor rotation during pump operation, and adjusting at least one of back pressure and a thread dimension to substantially equalize drag pressure and back pressure for a desired rotor speed during pump operation.  
         [0007]     In another aspect, the present invention provides a pump for a liquid, the pump comprising a stator including at least one electric winding adapted, in use, to generate a rotating electromagnetic field, a rotor mounted adjacent the stator for rotation in response to the rotating electromagnetic field, the rotor and stator providing first and second spaced-apart surfaces defining a pumping passage therebetween; and at least one helical thread disposed between the first and second surfaces and mounted to one of said surfaces, the thread having a rounded surface facing the other of said surfaces, wherein the rotor is sized relative to a selected working liquid such that, in use, the rotating rotor is radially supported relative to the stator substantially only by a layer of the liquid maintained between the rotor and stator by rotor rotation. Preferably rotor position is radially maintained substantially by a layer of the liquid between the rounded surface and the other of said surfaces which it faces.  
         [0008]     In another aspect, the present invention provides a pump comprising a housing and a rotor rotatable relative to the housing, the rotor and housing defining at least a first flow path for a pump fluid, the rotor being axially slidable relative to the housing between a first position and a second position, the first position corresponding to a rotor axial position during normal pump operation, the second position corresponding to a rotor axial position during a pump inoperative condition, the rotor in the second position providing a second flow path for the fluid, the second flow path causing a reduced fluid pressure drop relative to the first flow path when the pump is in the inoperative condition. Preferably the second flow path is at least partially provided through the rotor. Preferably the first flow path is provided around the rotor.  
         [0009]     In another aspect, the present invention provides a method of making a pump, comprising the steps of providing a housing, rotor, and at least one wire, winding the wire helically onto the rotor to provide a pumping member on the rotor, and fixing the wire to the rotor.  
         [0010]     In another aspect, the present invention provides a pump for pumping a liquid, the pump comprising a rotor, and a stator, the stator including at least one electrical winding and at least one cooling passage, and a working conduit extending from a pump inlet to a pump outlet, working conduit in liquid communication with the cooling passage at at least a cooling passage inlet, such that in use a portion of the pumped liquid circulates through the cooling passage.  
         [0011]     In another aspect, the present invention provides a pump comprising a rotor and working passage through which fluid is pumped and at least one feedback passage, the feedback passage providing fluid communication between a high pressure region of the pump to an inlet region of the pump. Preferably the feedback passage is provided through the rotor.  
         [0012]     In another aspect, the present invention provides a pump comprising a rotor working passage through which liquid is pumped and at least one feedback passage, the rotor being disposed in the working passage and axially slidable relative thereto, the working passage including a thrust surface against which the rotor is thrust during pump operation, the feedback passage providing liquid communication between a high pressure region of the working passage and the thrust surface such that, in use, a portion of the pressurized liquid is delivered to form a layer of liquid between the rotor and thrust surface.  
         [0013]     In another aspect, the present invention provides an anti-icing system comprising a pump and a circulation network, wherein the pump is configured to generate heat in operation as a result of viscous shear in the pump liquid, the heat being sufficient to provide a pre-selected anti-icing heat load to the liquid.  
         [0014]     Other advantages and features of the present invention will be disclosed with reference to the description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Reference will be now made to the accompanying drawings in which:  
         [0016]      FIG. 1  is a cross-sectional view of a helix pump incorporating one embodiment of the present invention;  
         [0017]      FIG. 2  is an isometric view of the embodiment of  FIG. 1 ;  
         [0018]      FIG. 3A  is an enlarged portion of  FIG. 1 ;  
         [0019]      FIG. 3B  is similar to  FIG. 3A  showing an another embodiment;  
         [0020]      FIG. 3C  is a further enlarged portion of  FIG. 3A , schematically showing some motions and forces involved;  
         [0021]      FIG. 4  is an isometric view of the rotor of  FIG. 1 ;  
         [0022]      FIG. 5  is a schematic illustration of two pumps of the present invention connected in series; and  
         [0023]      FIG. 6  is another embodiment according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Referring to  FIGS. 1, 2  and  4 , a helix pump, generally indicated at numeral  100 , is provided according to one preferred embodiment of the present invention.  
         [0025]     The helix pump  100  includes a cylindrical housing  102  having at one end a working conduit  104 , a pump inlet  106 , and pump outlet  110 . The housing  102 , or at least the working conduit  104  are made of non-metal material, for example, a plastic, ceramic or other electrically non-conductive material, so that eddy currents are not induced by the alternating magnetic field of the stator and rotor system. Preferably, in addition to being non-conductive, the inner wall of conduit  104  is smooth, and not laminated, to thereby provide sealing capability and low friction with the rotor, as will be described further below. Connection means, such as a plurality of annular grooves  108 , are provided on pump inlet  106  for connection with an oil source such as an oil tank (not shown). The end of the working conduit  104  abuts a shoulder (not indicated) of a pump outlet  110  which preferably is positioned co-axially with the housing  102 . The pump outlet  110  is also provided with connection means, such as a plurality of annular grooves  112  for connection to an oil circuit, including, for example, engine parts for lubrication, cooling, etc. Any suitable connection means, such as flanged connection or force-fit connection, etc. may be used. Alternately, where the pump inlet and/or outlet is in direct contact with the working fluid (e.g. if the pump is submerged in a working fluid reservoir, for example), the inlet and/or outlet may have a different suitable arrangement.  
         [0026]     A rotor  114  (cylindrical in this embodiment) is positioned within the working conduit  104 , and includes a preferably relatively thin retaining sleeve  116 , preferably made of a non-magnetic metal material, such as Inconel 718 (registered trade mark of for Inco Limited), titanium or certain non-magnetic stainless steels. The rotor  114  further includes at least one, but preferably a plurality of, permanent magnet(s)  118  within the sleeve  116  in a manner so as to provide a permanent magnet rotor suitable for use in a permanent magnet electric motor. The permanent magnets  118  are preferably retained within the sleeve  116  by a pair of non-magnetic end plates  120 ,  122  and an inner magnetic metal sleeve  124 . A central passage  125  preferably axially extends through the rotor  114 . The rotor  114  is adapted for rotation within the working conduit  104 . The rotor  114  external diameter is sized such that a sufficiently close relationship (discussed below) is defined between the external surface  115  of the rotor  114  and the internal surface (not indicated) of the working conduit  104 , which permits a layer of working fluid (in this case oil) in the clearance between the rotor and the conduit. As will be described further below, the clearance is preferably sized to provide a non-turbulent flow, and more preferably, to provide a substantially laminar flow in the pump. As will also be discussed further below, this is because the primary pumping effect of the invention is achieved through the application of a viscous shear force by thread  123  on the working fluid, which is reacted by the rotor  114  to move the working fluid tangentially and axially through the pump.  
         [0027]     Referring to  FIGS. 3A and 4 , in this embodiment three threads  123  are provided, in this embodiment in the form of wires  126 , each having a thread height  131 , a thread width  133  a thread length (not indicated), and preferably a rounded outer surface or land  127 , for reasons explained further below, such as that which is provided by the use of circular cross-sectioned wires  126 . A thread surface area (not indicated) being the thread length times the thread width  133 , represents the portion of the thread which is exposed directly to conduit  104 , the significance of which will be discussed further below. The wires  126  may be made of any suitable material, such as metal or carbon fibre, nylon, etc. The wires  126  are preferably mounted about the external surface of the rotor  114  in a helix pattern, having a helix or thread angle  135 , and circumferentially spaced apart from each other 120°. When rotated, the rotor  114  is dynamically radially supported within conduit  104  substantially only by a layer of the oil (the working fluid, in this example) between the rounded outer surface  127  of the thread  123  and the inner surface of the working conduit  104 , as described further below. Rounded surface  127  preferably has a radius of about 0.008″ or greater, but depends on pump size, speed, working liquid, etc. The threads  123 , the outer surface of rotor  114  and the inner surface of working conduit  104  together define a plurality of oil passages which are preferably relatively shallow and wide. These shallow and wide oil passages provide for a thin layer of working fluid between rotor and conduit.  
         [0028]     In accordance with the present invention, the number and configuration of the helical thread(s)  123  is/are not limited to the wires  126  described above, but rather any other suitable type and configuration of helical thread(s) may be used. For example, referring to  FIG. 3B , a more fastener-like thread  123  may be provide in the form of ridge  129 , having a rounded surface  127 , on the operative surface of the rotor. Alternately, a thread  123  may be formed and then mounted to the rotor in a suitable manner. Any other suitable configuration may also be used.  
         [0029]     Where the helical thread(s) are not integral with the rotor, they are preferably sealed to the rotor  114  to reduce leakage therebetween. For example, for wires  126  sealing is provided by welding or brazing, however other embodiments may employ an interference fit, other mechanical joints (e.g. adhesive or interlocking fit), friction fit, or other means to provide fixing and sealing. It will be understood that the mounting means and sealing means may vary, depend on the materials and configurations involved. Where extensible thread(s) are employed, such as wires