FIELD OF THE INVENTION
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
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.
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
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.
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
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:
FIG. 1 is a side view of a fuel pump assembly of the present invention;
FIG. 2 is a bottom end view of the fuel pump assembly;
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;
FIG. 4 is a cross section of the fuel pump assembly illustrating two fasteners and taken along line 4-4 of FIG. 2;
FIG. 5 is a top view of the spring clamp assembly;
FIG. 6 is a side view of the spring clamp assembly;
FIG. 7 is an enlarged fragmentary side view of the spring clamp assembly of FIG. 6;
FIG. 8 is a side view of a second embodiment of a fuel pump assembly;
FIG. 9 is a side view of a second embodiment of the spring clamp device utilized in FIG. 8; and
FIG. 10 is a segmented cross section of a third embodiment of a fuel pump assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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.
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.
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.
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.
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.
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.
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.
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).
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.
Patent Application
20060083631
