Abstract:
A fuel pump assembly has a pump mounted to an electric motor by a spring clamp device preferably having a plurality of arms spaced circumferentially around the pump and extending axially generally parallel to an axis of rotation of the motor, from a common base member. The base member is preferably received by the motor, and each arm preferably has a clip which projects radially inward to contact an outboard end face of the pump. The clips are preferably disengageable from the pump and exert a controlled force on the pump, thus producing a consistent and controlled clamping force across the housing encasement to eliminate any potential distortion of the preferably plastic housing.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a fuel pump assembly and more particularly to a spring clamp device for securing a motor to a pump of the assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     Prior art automotive fuel pump assemblies typically have an electric motor with a stator and an armature with a drive shaft connected to a fuel pump between inlet and outlet end caps which are all received inside of a metallic sleeve extending axially along the entire length of the assembly. The ends of the sleeve are rolled over and project radially inward of the end caps to generally align and hold the assembly together and prevent de-coupling of the pump from the motor. During manufacturing, the various components of the pump and motor and the end caps are all assembled inside the sleeve and then both of its ends are rolled over the end caps thus securing all of the components of the pump and motor together in axial alignment.  
         [0003]     Unfortunately, this process requires the entire assembly be purchased from a single manufacturer who assembles and/or produces both pump and motor components. Furthermore, rolling the ends of the sleeve places a compressive force on the internal components which is not easily controlled or consistently repeated. Excessive stress placed upon the plastic components of the pump can degrade pump performance. Yet further, the sleeve-type of pump and motor assembly is expensive to manufacture and can not be repaired without destroying the sleeve.  
       SUMMARY OF THE INVENTION  
       [0004]     A fuel pump assembly has a pump coupled to an electric motor by a spring clamp device preferably having a plurality of arms spaced circumferentially around the pump and motor and extending generally axially and parallel to an axis of rotation of the motor, from a common first member and to a plurality of second members. The first member spans radially and is preferably received by the motor, and the plurality of second members preferably project radially inward from the respective arms to contact an outboard face of the pump. The second members are preferably disengageable clips which exert a controlled force upon the pump, thus exhibiting a consistent and controlled stress across the pump encasement to eliminate any potential distortion of the preferably plastic encasement.  
         [0005]     Objects, feature, and advantages of this invention include a fuel pump assembly which can be dis-assembled without destroying any of the assembly components, the motor and pump can be separately manufactured and pre-assembled, and the pump encasement can be made of relatively inexpensive plastic without concern of distortion. Operation reliability and performance is improved, and the assembly is rugged, durable, maintenance free, of relatively simple design, inexpensive to manufacture and assemble, and in service has a long useful life. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     These and other objects, features and advantages of this invention will be apparent from the following detailed description of the presently preferred embodiments and best mode, appended claims, and accompanying drawings in which:  
         [0007]      FIG. 1  is a side view of a fuel pump assembly of the present invention;  
         [0008]      FIG. 2  is a bottom end view of the fuel pump assembly;  
         [0009]      FIG. 3  is a segmented cross section of a fuel pump and spring clamp device of the fuel pump assembly taken along line  3 - 3  of  FIG. 2 ;  
         [0010]      FIG. 4  is a cross section of the fuel pump assembly illustrating two fasteners and taken along line  4 - 4  of  FIG. 2 ;  
         [0011]      FIG. 5  is a top view of the spring clamp assembly;  
         [0012]      FIG. 6  is a side view of the spring clamp assembly;  
         [0013]      FIG. 7  is an enlarged fragmentary side view of the spring clamp assembly of  FIG. 6 ;  
         [0014]      FIG. 8  is a side view of a second embodiment of a fuel pump assembly;  
         [0015]      FIG. 9  is a side view of a second embodiment of the spring clamp device utilized in  FIG. 8 ; and  
         [0016]      FIG. 10  is a segmented cross section of a third embodiment of a fuel pump assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     Referring in more detail to the drawings,  FIGS. 1-4  illustrate an electric fuel pump assembly  20  embodying the present invention and having an electric motor  22  coupled to a fuel pump  24  secured by a spring clamp device  26  to the motor. The motor  22  is generally elongate axially and has a stator encircling an armature with a drive shaft  34  journaled for rotation by bearings carried by end caps  28  and  30  received in a housing shell  32 . The drive shaft  34  projects axially outward from the inboard end cap or surface  30  along an axis of rotation  36  for mechanical coupling to the fuel pump  24 . The motor  22  and the pump  24  are preferably pre-assembled, “off-the-shelf,” items which are releasably mounted together in coaxial alignment by the snap fitting spring clamp device  26 .  
         [0018]     Referring to  FIGS. 3 and 4 , the fuel pump  24  has an encasement or housing  38  with a base  48  and a cover or end cap  52  preferably made of non-corrosive and economical plastic which defines a cavity  40  receiving a gear-rotor assembly  42  of a positive displacement pump. The base  48  has an inboard face  44  which faces the inboard end cap or surface  30  of the motor  22  and a through bore  50  for receipt of the motor shaft  34 . The pump end cap or cover  52  is attached and sealed to the base  48  during assembly and after the gear-rotor assembly  42  is installed therein. The end cap  52  has an outboard end face  46  and an axially projecting fuel outlet  54  and a fuel inlet  56 . Inlet  56  communicates with the fuel inlet of the gear-rotor assembly  42  and outlet  54  communicates with the cavity or outlet  40  of the gear-rotor assembly through which it discharges fuel at a high pressure when operating. If desired, a turbine pump assembly or other type of fuel pump assembly may be utilized in lieu of the gear-rotor pump assembly  42 .  
         [0019]     Referring to  FIGS. 5-7 , the spring clamp device  26  releasably mounts and attaches together the motor  22  and pump  24  of the fuel pump assembly  20 . The clamp device  26  preferably attaches to the inboard end cap or surface  30  of the motor  22  by two fasteners or screws  60  and extends radially outward and axially along the pump housing  38  to partially envelope or “cage,” and resiliently engage the pump  24 . An annular member or base plate  62  of the spring clamp device  26  has two diametrically opposed holes  64  to receive the screws  60  which thread into the end cap  30  of the motor  22  and hold the base plate  62  directly against the end cap  30  in a substantially perpendicular orientation to the axis of rotation  36 . Four resilient flex arms  68  project substantially axially downward from a peripheral edge  66  of the base plate  62  and are preferably integral and unitary with the base plate. The arms  68  are preferably substantially equally spaced circumferentially from one another and are preferably slightly bowed outward when not flexed for engagement to the pump  24 . Located at the distal end  70  of each arm  68  is a finger or clip  72 , which projects generally radially inward, and resiliently snaps over the outboard face  46  of the pump encasement  38  as the arms  68  resiliently flex from a radially outward unstressed state and in a generally radially inward direction toward a radial unstressed state and axial stressed state.  
         [0020]     Each clip  72  has a contact portion  74  which projects radially inward from its associated flex arm  68  and preferably angles axially inward at an angle  78  preferably about five degrees when in a disengaged state (as best shown in  FIGS. 6 and 7 ) and with respect to an imaginary plane  76  disposed perpendicular to the axis of rotation  36 . From the contact portion  74 , the clip  72  has a rounded cam-like return bend  80  which extends to a generally axially outward projecting distal tab  82  of the clip  72 . The spring clamp device  26  is preferably made from a single stamping of sheet metal or spring steel.  
         [0021]     During assembly of the fuel pump assembly  20 , a downward projecting cylindrical shoulder  84  of the motor housing  32 , disposed concentrically about the shaft  34 , is received in the base plate  62  of the spring clamp device  26  through a central hole  86  (as best shown in  FIG. 5 ). The screws  60  are then threaded into the motor end cap  30  which rigidly holds the base plate  62  to the motor  22  with the flex arms  68  projecting generally axially away from the motor  22  (as best shown in  FIGS. 3 and 4 ). The clips  72  of the flex arms  68  are then resiliently moved radially outward so that the clips  72  radially clear the pump housing  38  when the pump  24  is moved between them, and axially toward and coupled with the motor  22 .  
         [0022]     With the pump  24  coupled to the motor drive shaft  34  and the flex arms  68  released, the cam-like bends  80  of the clips  72  are preferably in biased contact with a slightly rounded peripheral edge  81  of the pump encasement  38  but not yet in direct contact with the outboard face  46 . An external force applied in a radially inward direction against the mid-section of each bowed flex arm  68  causes the flex arms to generally straighten and the contact portions  74  of the clips  72  to align parallel with the imaginary plane  76  (as best shown in  FIG. 7 ). The cam-like bend  80  then assists each clip  72  to snap over the edge  81  and slide over the outboard face  46  in a radially inward direction. When the external force placed upon the flex arms is released, the resilience or spring force of the bowed flex arms  68  and clips  72  exert an evenly distributed and consistent force upon the plastic pump encasement  38  in an axially inward direction. If removing the pump  24  from the motor  22  is desired, a radially outward force is placed upon the clip tabs  82  which flexes the arms  68  radially outward to radially clear the clips  72  from the cylindrical pump housing  38 . Once cleared, the pump  24  can then be moved axially away and de-coupled and removed from the motor  22 .  
         [0023]      FIGS. 8 and 9  illustrate a modified spring clamp device  26 ′ wherein the flex arms  68 ′ extend the entire axial length of the pump  24 ′ and motor  22 ′ and the base plate  62 ′ is in biased contact with the outboard end cap  28 ′ of the motor housing  32 ′. Preferably the end cap  28 ′ has a cylindrical shoulder  88  over which the base plate  62 ′ is received. With this modification, separate fasteners or screws are not required.  
         [0024]     Skilled persons will understand that the orientation of the spring clamp device  26 ″ relative to the motor  22 ″ and pump  24 ″ could be reversed so that the clips  72 ″ engage the motor end cap or surface  28 ″ and the base plate  62 ″ is attached to the pump base  48 ″ or overlies and engages to the pump end cap  52 ″ (as best shown in  FIG. 10 ).  
         [0025]     While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possibly equivalent forms or ramifications of the invention and it is understood that the terms used herein are merely descriptive rather than limiting and that various changes may be made without departing from the spirit or scope of the invention.