Rotor pump seal

Feb. 23, 1965 s. _B mcleod etal 3,170,409

ROTOR PUMP SEAL

Filed April 1, 1963

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United States Patent Office ^{3 I70}’⁴⁰⁹

Patented Feb. 23. 1965

- --1:)3,170,409 ROTOR PUMP SEAL

Stewart B, McLeod, Southfield, and Robert E. Shelhart, Dearborn,- Mich;, assignors- tis-Djirir Gorpriration; Oak Park, Mich,, a corporation-of Michigan 5

Filed Apr. 1,1963, Ser. No, 269,478

Claims. (CI. 103—126)

This invention relates to fluid transfer pumps in general and more particularly to rotary pumps and the ₁₀fluid sealing problems thereof.

Rotary pumps require that the parts: thereof be machined to much closer tolerances than other type pumps. This applies to the fluid pumping faces of the pump parts but equally as well to the end-to-end dimensions of rotor jg parts and bores to preclude fluid volume and pressure

I losses either between- or- around the fluid transfer parts.

^! Providing, an edequate fluid seal between relatively / rotatably parts is always a problem but it is particular-_: ly difficult where several relatively rotatable parts are 20 involved and small size pump parts are desirable.

A Gerotor type pump such as is used in a pump, ’motor and fluid reservoir assembly to supply hydraulic fluid to power cylinders of a convertible folding top mechanism provides a good example for explaining the 25 scope of the problem mentioned and the solution to such problems offered by this invention.

¹ In a Gerotor type pump there are cooperative and relatively rotatable internal and external rotor parts which arc received within a rotor chamber or bore in a housing 39 part. The rotor chamber or bore is closed at one end by a . cover, or a housing part which serves such purpose, and the internal rotor is driven by a shaft extended through the other end of the housing and engaged therewith. The internal rotor drives the external rotor 35 and both rotate relatively and with respect to the end walls of the rotor chamber;

In this type pump the inlet and outlet ports are formed through one of the rotor chamber end Walls and are provided in open communication between the relatively 40 rotatably rotor parts and on diametrically opposite sides thereof; Accordingly, any undue clearance between the ends of the rotor parts: and the wall closing the rotor chamber provides a direct passageway between the fluid inlet and outlet ports. . . 45 \ ' A pump having a one-inch rotor will require tolerances as close as .0005 in the depth of the rotor chamber bore and .0003 thickness for the rotor parts. This usually i means problems in matching rotor parts to each other ’ ) as well as to particular housing bores, if losses are to be 50 minimized, and requires further expense in this regard;

Just as close tolerances must be maintained to prevent fluid volume and pressure losses across the pump, it is also obvious that reasonable clearance or other means must be provided to enable free movement of the rotor 55 parts without binding, scoring pressures or the like which might later cause pump failures or inefficiencies.

¹ In the past efforts have been made to provide either a fluid pressure seal or a spring loaded seal between the rotor and cover members in this type of pump. How- 60 ever, neither have proven acceptable and the close tolerance requirements have prevailed.

¹ Fluid pressure seals normally include a small disc received between the cover and rotor parts with means for applying the pump pressure between the disc and the 55 cover to seat the seal on the rotor parts. The sealing pressure must be light to avoid any. interference with the rotor drive and it must be effected before fluid passage occurs under the seal. Otherwise the . seal is either seated against the cover or balanced up off the rotor parts 70 and is ineffective.

’ Spring loaded seals on the other hand present nu2 ' ' ' merous problems in small pump assemblies. They* normally include a disc and a small spring er a spring'washer which makes assembly extremely difficult. The spring or spring washer is received between the rotor chamber cover and the- sealing disc. The spring pressure must' be light to prevent binding and there is invariably a wear problem sooner or later. : :

It is an object of this invention to provide a fluid pressure seal for rotary pumps and others which is simple in construction, easily provided in a piimp assembly, essentially wear resistant, frees tolerances, and is highly effective in use.

^; It is an object of this invention to provide a selfretaining and positionable seal having magnetic properties and responsive to proper seating fluid pressures.

The fluid seal of this invention includes a sealing ring or disc having magnetic characteristics for attract tion and seating against the rotor members in a pump housing bore., It is disposed to receive pump fluid: thereover,-between itself and a closing cover member, to supplement: the force of magnetic attraction and to keep the seal seated and prevent fluid passage between inlet and outlet parts. The flux attachment between the magnetic disc and rotor parts provides no hindrance to relative movement between the rotor parts and the resultant efficiency of the fluid pumps is immeasurably improved.

These and other objects and advantages to be gained in practice of: this invention will be better: understood and appreciated: upon a reading of the following· specification in regard to a preferred embodiment' of the invention and having reference to the accompanying drawings wherein:

FIGURE 1 is a side view of a: pump, motor and reservoir assembly having parts broken away and shown in cross-section to better show an embodiment of this invention used therein.'

FIGURE 2 is an enlarged cross-sectional view of the pump portion of the assembly shown by FIGURE Γ as seen in the plane of line 2—2 thereon.

FIGURE 3 is an enlarged, fragmentary, and crosssectional view of the pump portion of: the assembly shown by FIGURE 1, with the details of the fluid pressure sealing means of this invention shown more clearly.

FIGURE 4 is an exploded view of certain’ pump. parts and the fluid seal of this invention as taken from FIGURE 3.

FIGURE 1 shows an assembly 10 including a motor housing 12, pump:14 and reservoir member 16’.

The motor housing 12 includes a housing shell 18 which is crimped or otherwise engaged as at 20 to the pump 14. A reversible electric motor (not shown) is provided in the housing shell 18 and has the shaft 22 thereof extended into the pump 14- for driving engagement with the operable parts thereof.

The pump 14’includes a pump housing and cover parts 24 and 26 respectively.’

Referring to FIGURE 3; the pump housing 24 has a cylindrical bore 28 provided in an end face thereof and receptive of the operable parts of the pump later described. A passage 30 is provided through the other' end of the housing, from the bore 28, for the drive shaft 22 and a suitable journal bearing 32 and fluid seal· 34 are provided therein. In addition,· interchangeable inlet and outlet passages-36 and 38 are provided through’the housing and in communication with the bore 28,

The cover part 26 of pump 14 is secured to the end of the housing part 24 by threaded bolt fasteners 39. It includes a recess 40 formed in the face thereof abutting the-housing part and in concentric alignment with the bore 28 which, as previously mentioned, is receptive of

3,170,409 the operative parts of the pump. The recess 40 is itself receptive of an annular disc 42 of magnetic material.

•The reservoir member 16 includes a housing or shell 44 which is secured to the cover part 26 of the pump 14 by a tie bolt 46. A fluid reservoir chamber space 48 is provided within the housing or shell 44 and suitable reservoir passages 50 and 52 are formed through the cover and housing parts 24 and 26 of the pump 14 for communication with the inlet and outlet passages 36 and 38 of the pump.

The motor, pump and reservoir assembly unit 10 is of the type used to supply hydraulic fluid to one or more hydraulic cylinders such as may be used to operate a folding convertible top for automotive vehicles. Accordingly, a reversible motor is used to operate the pump for supplying fluid from one or the other of the inlet and outlet passages 36 and 38 through the pump and to the other thereof.

Although not specifically shown, it will also be appreciated that the reservoir passages 50 and 52 include check valve means to assure communication only between the inlet side of the pump and the reservoir chamber in the course of the fluid flow transfer. Such check valve means have not been specifically shown or described since they do not pertain to the present invitation other than as makes the overall fluid transfer system more efficient.

Referring now to FIGURES 2-4:

Within the pump bore 28 is provided a wear place 54 and concentrically disposed internal and external rotor parts 56 and 58.

The wear plate 54 is of plastic or like non-magnetic and wear resistant material. It is provided in the bottom of the rotor bore 28 and is formed to include crescent shaped inlet and outlet pasages 60 and 62 disposed on diametrically opposite sides thereof. Similarly formed and disposed inlet and outlet ports 64 and 66 are provided through the pump housing part 24 and extend from the rotor chamber bore 28 to the inlet and outlet passages 36 and 38 to provide means of fluid flow communication therebetween. The wear plate 54 includes a positioning detent 68 which serves to locate it within the rotor chamber bore with its inlet and outlet passages alinged with the fluid flow inlet and outlet ports.

Referring to FIGURE 2, it will be noted that the drive shaft 22 is received eccentrically within the rotor bore 28 and similarly through a shaft passage 70 in the wear plate. The end of the drive shaft 22 is in turn formed for driving engagement with the internal rotor member 56 within a D-drive slot 72 provided therein.

The internal or inner disposed rotor member 56 is formed to include teeth 74 formed for driving engagement with the outer disposed or external rotor part 58. The outer rotor part 58 is, in turn, formed to include lobes 76 between which the inner rotor teeth 74 are engaged and over which the teeth pass in the transfer of fluid in the manner commonly known with such cooperative rotor parts. For purposes of discussion the expanded and contracted fluid pockets formed between the rotor parts in the course of their relative rotation will henceforth be referred to as the pump chambei· space and is identified in the drawings by the numeral 78.

The magnetic discs 42 which is disposed within the cover recess 40 is annular in shape and with an exteral rotor member which is one inch in diameter and it is about one-eighth inch in thickness. The disc is disposed to overlap both of the rotor parts and to close the ends of the chamber spaces provided therebetween. It is of less thickness than the cover recess 40 and a clearance space 80 is accordingly present between the disc and the end wall 82 of the cover recess.

The housing part 24 and cover part 26 are of a nonmagnetic material, as a zinc or aluminum die casting, while the rotor parts 56 and 58 are themselves magnetically responsive.

The disc 42 is accordingly magnetically attracted and normally retained to the rotor parts by magnetic flux lines passing therebetween.

In the operation of the disclosed motor, pump and 5 reservoir assembly 10 the magnetic disc 42 provides a fluid seal in the manner hereinafter described:

When the drive motor is started, the drive shaft 22 turns the internal rotor member 56 in one direction or the other and it in turn drives the external rotor 58 and 10 the transfer of fluid across the pump commences.

Fluid flow is induced through one of the inlet and outlet passages 36 and 38 to the appropriate supply port 64 or 66. The reservoir check valve system (not shown) opens the appropriate reservoir passage 50 or 52 15 and closes the other thereof. Fluid flow is accordingly obtained through the inlet port to the rotor bore 28 and within the appropriate pump chamber spaces between the rotor members 56 and 58 in the course of their rotation.

The initial build-up of fluid pressure within the inlet 20 fluid passage will also cause fluid to bleed and pass under the rotor part 56, about the end of the drive shaft 22, through the D-drive slot 72 in the rotor part 56 centrally through the annular magnetic disc 42 and to the clearance space 80 on the back side thereof and between 25 the magnetic disc and the end wall 82 of the disc receptive recess 40 provided in the pump cover part 26.

The magnetic attraction of the annular disc 42 to the rotor parts assures an initial closure engagement over the chamber space between the rotor parts and also as30 sures having the clearance space 80 over the disc.

The permissive bleeding or flow of fluid through the disc 42 to the clearance space 80 is provided to assure proper seating thereof, to supplement the force of magnetic attraction holding the annular disc in sealing rela35 tion over the rotor parts, and also to provide a light pressure seal to safeguard against fluid pressure within the pump chamber spaces having an initial build-up sufficient to lift the magnetic disc from its magnetically attracted engagement with the rotor parts and permit a 40 by-passing fluid flow across the ends of the rotor parts which is the very thing to be avoided. The fluid pressure within the clearance space 80 is sufficient to counteract the fluid pressure within the pump chamber spaces 78 and to assure magnetic attraction of the disc 42 to the 45. rotor parts precluding this cross flow. Furthermore, once this pressure build-up is obtained within the clearance space 80 the magnetic disc 42 itself, by the pressure applied on the opposite face of the internal rotor member 56 precludes any significant fluid flow to the 50 clearance space or otherwise under the rotor parts and between the pump chamber spaces.

Neither the magnetic flux connection of the magnetic disc 42 to the rotor parts, nor the fluid pressure assuring such connection, interferes with the relative movement 55 between the rotor parts. The flux lines of attraction are readily sheared and re-established at points of relative contact between the magnetic disc and the respective rotor parts.

The relative movement between the disc and rotor 60 parts is minimal since it is only such as exists between the rotor parts themselves. That is, the magnetic disc 42 will rotate with one of the rotor parts and will move relative to the other thereof only in the same respect as the rotor parts more relative to each other.

No wear will be experienced as regards the magnetic disc 42 and the end wall 82 of the cover recess 40 since the two are not in engagement and a fluid film is provided therebetween.

₇0 With the magnetic seal of this invention, supplemented by the pressure seal in the manner disclosed, fluid flow through the pump 14 is through one of inlet and outlet passages 36 and 38, to the pump chamber spaces between the rotor members 56 and 58 and through the other 75 of the inlet and outlet passages without significant fluid

3,170,409 volume or pressure loss therebetween as experienced with conventional Gerotor pumps.

Without further discussion it should be obvious that some variations, modifications, alternate arrangements in structure and the like are conceivable and within the 5 scope of this invention.

Although a preferred embodiment and arrangement of structure has been specifically shown and described in detail, it will be appreciated that this has been done to illustrate the scope of the present invention and without 10 intent to unnecessarily limit the invention thereto in any regard. Accordingly, such improvements, modifications and alterations as come to mind and are within the spirit of this invention and are not specifically excluded by the language of the hereinafter appended claims 15 are to be considered as inclusive thereunder.