Gerator hydraulic device having seal with steel and resilient members

A seal utilizing a two part construction of a rubber resilient body and a steel sealing wear member for use in a cavity to create a seal between two parts that have relative motion in respect to each other.

Gerotor hydraulic devices are recognized in the field as being a preferred 
method of developing power in low speed, high torque applications. This 
include wheel drive, auger drives, scissors lifts, and other similar 
applications. Hydraulic motors are disclosed in the U.S. patent 
application Nos. 3,606,601 and 4,697,997. Hydraulic motors, however, need 
to have sealing contact at surfaces between an orbiting and/or rotating 
part and a stationary part. This sealing contact is difficult to provide 
due to the problems with the eccentric and/or rotary motion between these 
two parts, as well as the need to compensate for temperature induced 
dimensional changes in the various parts. In addition there is a possible 
passage over holes such as valving openings that may damage the seals. Due 
to these difficulties, most gerotor designers utilize a minimum number of 
seals between eccentric parts. These designers instead design in the 
tolerances of 0.002-3 to as little as 0.0001 inch clearance between the 
parts and utilize this reduced clearance as the seal. This design is 
serviceable. However, it still allows a certain amount of fluid to bypass 
through the clearance. This bypass reduces the efficiency of the gerotor 
mechanism from what it otherwise would be. In addition the dimension of 
the device becomes more critical in the design. 
OBJECTS 
It is an object of this invention to provide for a high reliability 
mechanical seal between parts moving in an eccentric or other manner in 
respect to each other. 
It is an object of this invention to reduce the leakage between parts 
having eccentric or other motion in respect to each other. 
It is an object of this invention to increase the efficiency of gerotor 
motor hydraulic devices. 
It is an object of this invention to increase the longevity of gerotor 
motor hydraulic devices. 
It is an object of this invention to increase the volumetric and mechanical 
efficiency of gerotor motor hydraulic devices. 
Other objects, and a more complete understanding of the invention, may be 
had by referring to the drawings and specifications in which:

This invention relates to an improved seal. The invention will be described 
in the preferred environment of a gerotor motor/pump (not shown) having a 
housing containing a drive shaft (not shown) connected to a gerotor 
structure 13 and rotary valve 14 via a wobble stick 15 (FIG. 1). The 
environment of the invention in a similar complete gerotor motor is 
described in my U.S. application No. 282,675 filed Dec. 12, 1988--a device 
having a sealed control opening and an orbiting valve--issue fee paid Aug. 
14, 1989, U.S. Pat. No. 4,877,383 (incorporated herein by reference). This 
gerotor device can produce power when fluidically connected as a motor to 
a source of high pressure or it can produce high pressure fluid when 
physically connected as a pump to a motor or other source of rotary power. 
The device is described as a motor. 
The drive shaft is located in the housing for rotation in respect thereto. 
In this gerotor motor, as in that disclosed in Mr. White's prior 
application No. 282,675, U.S. Pat. No. 4,877,383 or the U.S. Pat. No. 
4,697,997, the speed and direction of rotation of this shaft 12 is 
governed by the volume, pressure, and direction of flow of the fluid 
through the gerotor structure 13. 
The gerotor structure 13 itself includes an end plate 20, a manifold plate 
21, a gerotor device 22, and a balancing plate 23 fixedly attached 
together so as to produce a single integral unit (by bolts). The gerotor 
device shown is a rotor 16 within a stator 17 (FIG. 1). Other pressure 
mechanisms could also be used. 
The end plate 20 is the termination cap and porting plate for the device 
10. Two ports 30 and 31 are machined into the plate 20 so as to form the 
fluid connections for the device. One port 30 connects to a commutation 
ring 32 in the opposing face of the plate 20. This commutation ring 32 in 
turn communicates with the central section 34 of the orbiting valve 14 to 
provide a fluid connection therefor. The other port 31 connects to a 
ring-shaped cavity 33 on the opposing side of the plate 20. This cavity 33 
surrounds the outside circumferential edge 35 of the orbiting valve 14 to 
provide a second fluid connection to the valve 14. 
The orbiting valve 14 is the main valve for the device. The center opening 
34 of the valve 14 communicates with one port 30 via the ring 32. The 
external side about outer edge 35 of the valve 14 communicates with the 
other port 31. (Due to the fact that there is a space 36 between the 
outermost position 35 of the orbiting valve 14, fluid is able to freely 
move about the outside of the valve 14). 
The manifold plate 21 is next to the orbiting valve 14 between the valve 14 
and rotor 16. The manifold plate 21 serves to connect the center 34 and 
outer 35 sections of the orbiting valve 14 to the gerotor cells between 
the rotor 16 and stator 17 selectively as the device is operated. The 
manifold plate 21 itself is formed as a brazed assembly of four thin 
stamped plates 40-43. 
The pressurized fluid in the embodiment disclosed is segregated to the area 
of the device near the orbiting valve 14 by the sealing of the wobble 
stick drive connection to the valve 14. In the preferred embodiment shown, 
this sealing is accomplished by restricting the effective size of the 
drive opening 50 through the valving plate 40 of the manifold plate 21 to 
a size capable of being sealed by the inside drive surface 52 of the valve 
14. To accomplish this, the radius of the drive surface 52 of the valve is 
slightly greater than the radius of the opening 50 plus the offset of the 
center of the valve 14 from the center of the valve manifold 21. With this 
relationship, the inside drive surface 52 of the valve 14 will seal the 
opening 50 throughout the operational valving orbit of the valve 14. 
Central seals 38 improve the seal against fluid from passing into the 
wobble stick drive connection at the center of the valve 14. Note that the 
central seal 38A on the inside of the valve 14 against the valving plate 
40 is larger than the central seal 38B of the valve 14 against the porting 
end plate 20. The reason for this is that the seal 38A seals fluid from 
the wobble stick drive connection access hole 50 in plate 40. The seal 38A 
must be a sufficient diameter to continually seal this hole 50 during the 
entire orbiting motion of the valve 14. The seal 38A must therefore have a 
radius greater than the radius of the hole 51 plus the amount of orbit 
offset. Since the hole 50 is of significant diameter, the seal 38A must 
also have a significant diameter. In contrast, the seal 38B seals the 
wobble stick of connection 51 to the valve 14. The seal 38B must be of a 
diameter to continually seal this connection 51 while at the same time 
fitting within the diameter of the commutation groove 32 in the end plate 
20 (so as to not subject the seal to inordinate wear). The seal 38B must 
therefore have a diameter larger than the connection 51 and also a 
diameter smaller than the radius of the groove 32. The size of the seal 
38B is thus normally different from the size of the seal 38A. An outer 
seal 39 prevents fluid from passing between the central section 34 of the 
valve 14 and the space 36 about the outer edge 35 of the valve 14. (Note 
that any seal 39 on the outer ring of the valve 14 on the opposite side of 
the valve 14 against the manifold plate 21 would travel over the valve 
openings 53 for the device, subjecting such seal to wear. In the preferred 
embodiment shown, the seal at this point is limited to the flat steel of 
the outer ring of the valve 14; this flat steel provides an acceptable 
seal without being subject to the wear a separate seal would be. This is 
especially so given the loading of the flat steel by the seal 39 on the 
opposing side of the valve 14. The improved seal of the invention could, 
however, be utilized at this location (and others such as in the rotor) if 
desired; The improved seal, having no edges or resilient section to catch 
and traveling along a flat surface, would provide an improved seal at this 
point at a cost of some longevity.) 
Any fluid that does leak through the seals 38 into the central wobble stick 
cavity is easily drained off: the fluid would be of very low volume. The 
device shown in FIG. 1 has an internal drain connection for this fluid. In 
this device a passage 61 connects the central opening 56 to the housing 
ring-shaped channel 62 in the valve spacing plate. The ring-shaped channel 
62 is in turn connected via check valves 63 and 64 operate to selectively 
connect the ring channel 62 (and thus the central opening 56 the housing 
11) to the port 30, 31 having the lowest relative pressure. This provides 
an automatic internal drain for any excess fluid in the central opening 
56. 
The wobble stick 15 connects the drive shaft to both the rotor 16 and valve 
14 passing rotary and orbital forces. 
In its orbiting motion the valve 14 connects the port 30 through the 
central opening 34 to some gerotor cells of the gerotor device 22 while 
connecting the port 31 through the surrounding edge 35 to others of 
gerotor cells of the gerotor device 22 through the manifold plate 21 as is 
customary for separate orbiting valve devices. 
The improved seal 38, 39 of this application includes a body 100 having a 
resilient section 112 and a integral steel section 113. This seal is 
located within a generally cylindrical cavity in one of the body parts 
having an eccentric or other motion relative to the other. 
The composition/cross sectional shape of the resilient section 112 of the 
body 100 of the preferred improved seal is not critical. It is preferred 
that this section 112 has the properties of a) resiliency; and b) 
sufficient strength so as to retain the bond with the later discussed 
steel section. 
In the preferred embodiment shown the resiliency is established by the 
utilization of a 70 Durometer Buna-N material for the section 112 of the 
seal in combination with a tapered shape. The steel member is bonded to 
the Buna-N material such that no separation would normally occur. This 
bonding retains the steel member 113 in its relative position against the 
rotational forces which are otherwise put on the steel member. This 
retention reduces the wear on the seal by insuring that any wear that does 
occur does so between the steel surface and the opposing part and not 
between the steel member 113 and the resilient section 112. The tapered 
shape of the resilient member gives the seal a further range of 
resiliency. In addition to the use of a tapered shape in combination with 
the rectangular cavity allows the seal a significant range of movement 
including expansion and contraction within the cavity without otherwise 
impeding the movement of the seal. This increases the ability of a gerotor 
designer to design a seal having predictable qualities. 
The steel member 113 is the main seal for the gerotor device between the 
parts having an eccentric motion. The steel member 113 accomplishes this 
by having effectively zero tolerance or clearance between the steel member 
and the other part. To provide for this sealing contact, the steel member 
113 has the attributes of resistance to abrasion and other desirable 
surface wear characteristics. It's preferred that the strength of this 
steel member 113 be significantly greater than the other part of device on 
which it will be bearing. Note that the steel member 113 has a limited 
surface area in respect to the area swept by the other part of the device. 
For this reason the sealing loads are spread out on the other part of the 
device instead of concentrated as in the steel member 113. This 
spreading/traveling contact is the primary reason that the other part of 
the device can be of a softer material than the steel member 113. In the 
preferred embodiment shown, the steel member has a hardness of above RC-35 
with RC-60 preferred and the hardness of the part upon which it will bear 
(the housing part 20 or the plate 40) is much softer at approximately 
RB-80. The use of steel for the critical sealing function eliminates most 
consideration for the temperature of the device (i.e. plastic etc. or 
something else that might have its strength compromised by the 200.degree. 
F. typical temperature for gerotor devices). 
The dimensions and strengths for the seal of this invention are selected in 
order to match its application. 
The particular preferred seal 39 disclosed has a resilient member 112 with 
an unstressed overall inner diameter from 1.628 to 1.630 inches, an outer 
diameter from 1.747 to 1.749 inches, and a depth from 0.097 to 0.099 
inches. The sides 115 of the resilient member 112 are tapered at 
15.degree. after a distance from 0.040 to 0.042 inches from one end 
thereof. The 15.degree. taper leads to an end 116 having a radius of 0.030 
to 0.032 inches. The steel member 113 has an overall inner diameter and 
outer diameter the same as the resilient member 112 and a depth from 0.009 
to 0.011 inches. The preferred seal 38B has a resilient member 112 with an 
unstressed overall inner diameter from 0.375 to 0.377 inches, and an outer 
diameter from 0.497 to 0.499 laches. (The other dimensions are the same as 
the seal 39.) These dimensions have been found to provide a good 
combination of strength vs. resiliency for the seals as previously 
discussed. The steel member 113 preferably has a hardness of from RC-35 to 
RC-60. 
The cavity 120 in the part which cooperates with the seal is designed to 
hold the improved seal in position in respect to the eccentric forces 
imparted to the steel member of the seal while at the same time providing 
a surface 121 against which the resilient member can bear to hold the 
steel member 113 in contact with the other part. This insures that the 
seal remains in place in respect to the part while at the same time 
providing a good sealing contact with such part throughout the life of the 
seal. In the preferred embodiment shown, the cavity is a generally 
rectangularly shaped cavity having a width substantially equal to the 
width of the steel member, and having a depth a little less than the total 
dimension of the improved seal including body 100 and steel member 113. 
The width of the cavity 120 retains the steel member 113 in place in 
respect to the eccentric or sideways forces put on such member 113 during 
the operation of the device, while at the same time allowing a piston-type 
motion of the steel member in and out of the cavity. The depth of the 
cavity is designed to insure that the steel member 113 protrudes slightly 
out of the surface of the part 122 containing the cavity, also providing a 
support for the sides of the steel member 113, while at the same time 
providing enough surface area between the resilient member and either the 
sides or the bottom of the cavity, so as to allow the resilient member to 
expand and contract while holding the steel part in position in respect to 
the rotational forces put on such steel part by the eccentric and/or 
rotary motion between the first and second moving parts. In the preferred 
embodiment shown, the cavity has a rectangular cross-section with a depth 
slightly less than the depth of the uncompressed resilient member such 
that the steel member just barely engages the sidewalls of the cavity in 
the member's uncompressed state. This relationship facilitates the 
construction of the device by insuring that no special concern need be 
taken for the seal during the assembly of the device. This is done by 
having the steel member seated in respect to the cavity in the unstressed 
unassembled position. After assembly, this sidewall contact is preferably 
increased to support the sides of the steel member 113. 
The particular improved seal 39 dimensioned earlier is designed to be 
utilized in a cavity having an inner diameter from 1.623 to 1.625 inches, 
an outer diameter from 1.752 to 1.754 inches, and a depth from 0.1002 to 
0.1004 inches. The dimensions for the cavity for the preferred seal 38B 
are an inner diameter from 0.370 to 0.372 inches, an outer diameter from 
0.502 to 0.504 inches and a depth from 0.1002 to 0.1004 inches. 
With these dimensions, the steel member 113 can be seated within the cavity 
120 during assembly with the assembly compressing the resilient member 112 
so as to preload the steel member 113 into sealing contact with the 
associated part (note again that it is preferred that the depth of the 
steel member 113 be greater than the maximum distance between the two 
moving parts so as to reduce the shearing loads on the steel/resilient 
member bond). 
Although the invention has been described in its preferred form, with as 
certain degree of particularity, it is to be understood that numerous 
changes could be made without departing from the invention as hereinafter 
claimed. For example the seal could be utilized in a purely rotational 
application, the steel member could be made of ceramic, or other changes 
made.