Interengaging gear machine with compensating force on bearing members

A pair of mating gears are mounted for rotation about respective axes in a gear-type fluid displacing pump or motor. Each gear has a pair of shaft portions at opposite axial ends of the respective gear, and bearing members surround respective ones of the shaft portions for journalling the gears. Each bearing member of one of the gears is juxtaposed with a respective bearing member of the other of said gears and, during rotation of the gears, the juxtaposed bearing members are subjected to forces which urge the bearing members to move relative to each other, particularly in direction towards each other. An arrangement is provided to counteract such forces and to oppose such relative movement of the juxtaposed bearing members.

BACKGROUND OF THE INVENTION 
The present invention generally relates to a gear-type fluid displacing 
machine and, more particularly, to external gear-type hydraulic pumps or 
motors and, still more particularly, to improvements in the operation of 
such hydraulic machines. 
During the operation of presently known gear-type pumps, the finite number 
of component parts of such machines causes non-uniform delivery of fluid 
to be pumped to a user. The torque characteristic of such machines also 
varies widely between maximum and minimum values. Such non-uniform 
operation is highly unsatisfactory for most commercial applications. 
Moreover, during operation of such gear-type machines, the rotating gears 
are subjected to forces which urge the gears to move relative to each 
other due to an unequal distribution of pressure which exists in the 
region about the gears. Such forces have a force component which urges the 
gears, and concomitantly the bearing members which journal the gears, 
towards each other. Moreover, such forces have a force component which 
urges the gears against the inner circumferential wall of the housing 
chamber in which the gears are mounted. 
Such forces are highly undesirable because they generate fluctuations in 
the rate and quantity of the fluid to be displaced in the machine, thereby 
decreasing the efficiency of the operation of the machine. Such 
fluctuations also generate chatter and prevent quiet, smooth-running 
operation. 
SUMMARY OF THE INVENTION 
Accordingly, it is the general object of the present invention to overcome 
the disadvantages of the prior art. 
Another object of the present invention is to improve the efficiency of 
operation of a gear-type machine. 
Still another object of the present invention is to counteract any forces 
which tend to move the gears and their associated bearing members relative 
to each other. 
Yet another object of the present invention is to provide a quiet, 
smooth-running fluid displacing machine. 
In keeping with these objects and others which will become apparent 
hereinafter, one feature of the invention resides, briefly stated, in a 
combination in a gear-type fluid displacing machine, particularly a pump 
or a motor, which comprises a pair of mating gears each having a pair of 
shaft portions at opposite axial ends of the respective gear. The gears 
are mounted in the machine for rotation about respective axes. A pair of 
bearing members journal each gear, and each bearing member surrounds one 
of the shaft portions. Moreover, each bearing member of one of the gears 
is juxtaposed with a respective bearing member of the other of said gears. 
During rotation of the gears, the bearing members are subjected to forces 
which urge the bearing members to move relative to one another along a 
direction such that the distance between the axes of rotation of the gears 
is changed. In accordance with the invention, counteracting means are 
operative for opposing such forces and such relative movement of the 
juxtaposed bearing members. If the forces urge the juxtaposed bearing 
members to move in direction generally towards each other, then the 
counteracting means is operative for preventing such relative movement of 
the juxtaposed bearing members towards each other. 
In a preferred embodiment, the juxtaposed bearing members bound a gap with 
each other, and the counteracting means which is in communication with a 
high-pressure zone of the machine conveys this high pressure to this gap. 
A compensating force is thereby generated in the gap and acts to oppose 
the undesirable forces which act on the gears and on the bearing members. 
The invention thus overcomes the prior art problem of having the bearing 
members strike each other with relatively great noise at relatively fast 
speeds and with relatively large force magnitudes. The rather high contact 
pressure between bearing members of prior art constructions is likewise 
substantially reduced. Gears mounted in machines of the present invention 
will no longer move through or oscillate within large distances, i.e. gear 
play is substantially reduced towards zero with the machines of the 
present invention. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The gear-type fluid displacing machine of FIG. 1 may be used either as a 
pump or as a motor. The machine comprises a housing having a main or 
central section 10 and two outer side sections or covers 11 and 12 which 
are bolted to the main section 10, as shown in FIG. 3. The covers 11 and 
12 overlie and seal opposite ends of a chamber 13 which has a 
cross-sectional configuration fashioned after the number "eight." The 
"eight"-shaped chamber 13, as shown in FIG. 3, comprises two partially 
overlapping cylindrical bores which are machined into the main section 10. 
A pair of mating gears 26 and 27 are respectively received in the bores of 
chamber 13, and the gears are operative for generating a high-pressure 
zone or area in the machine as they rotate. Gear 26 has trunnions or stub 
shaft portions 22, 23 at its opposite axial ends; and gear 27 has 
analogous stub shaft portions 24, 25 at its opposite axial ends. Each bore 
of the chamber 13 receives a pair of coaxial annular bearing members 14, 
16 or 15, 17. Bearing members 14, 16 respectively surround shaft portions 
22, 23, thereby journalling gear 26. Bearing members 15, 17 respectively 
surround shaft portions 24 and 25, thereby journalling gear 27. Bearing 
members 14-17 are formed with interior bores 18-21 which respectively 
receive stub shaft portions 22, 24, 23 and 25. 
One of the shaft portions, e.g. the shaft portion 25 of gear 27, has an 
extension 28 which passes through an opening 29 formed in cover 12. The 
free end of this extension 28 can be coupled to a prime mover, not shown. 
Sealing plate 30 is located between the axial ends of gears 26, 27 which 
face bearing members 14, 15 and the axial ends of the latter. Similarly, 
sealing plate 31 is located intermediate the opposite axial ends of gears 
26, 27, which face bearing members 16, 17 and the axial ends of the 
latter. Sealing plates 30, 31 are formed with bores 34-37 which 
respectively surround shaft portions 22, 24, 23 and 25 with clearance. 
Sealing plates 30, 31 facilitate fluid leakage reduction within the 
machine since they are pressed by hydraulic forces in sealing engagement 
with the respective axial ends of the bearing members 14-17 and the axial 
ends of the gears 26, 27. 
Sealing plates 30, 31 are respectively formed with channels 32, 33 in which 
sealing elements are accomodated. Each channel 32, 33 has a configuration 
fashioned after the numeral "three," as shown in FIG. 3. Bores 38 
establish communication between the channels 32, 33 and a high-pressure 
zone established by the rotating gears during operation of the fluid 
displacing machine. 
The fluid displacing machine has an input port 50 and an output port 49. 
When used as a pump, input port 50 is at low pressure and output port 49 
is at high pressure. Conversely, when used as a motor, input port 50 is at 
high pressure and output port 49 is at low pressure. 
During rotation of gears 26, 27 an unequal distribution of pressure exists 
about the periphery of the gears which subjects the gears to a hydraulic 
force F.sub.hydr having a force component which urges the gears towards 
each other. Concomitantly, the individual members of the juxtaposed pairs 
of bearing members 14, 15 and 16, 17 are urged towards each other. As 
noted above, this relative movement or play is highly undesirable because 
the gears and bearing members cannot operate efficiently and quietly as a 
result of such undesirable play. 
FIG. 2 shows a proposed way of counteracting such relative movement. A 
cutout or cylindrical recess 41 is formed at side surface 39 of bearing 
member 14. Another similar cutout or cylindrical recess 42 faces cutout 41 
and is formed at side surface 40 of bearing member 15. The line of 
symmetry of the cylindrical cutouts 40, 41 extends generally normally of 
the axes of rotation of gears 26, 27, i.e. the line of symmetry extends in 
direction of line A--A. 
An insert member 43, preferably of elastic resilient material, is mounted 
in recess 42 so that the insert member 43 is flush with the closed end of 
recess 42. The insert member 43 extends into and is received in recess 41. 
The upper surface 44 of insert member 43 is arcuate and bounds a space or 
gap 47 with the closed end of recess 41. 
In accordance with the invention, the high pressure generated by the gears 
26, 27 during operation of the machine is communicated via bores 38 to 
channel 32. A connecting bore 45 connects the channel 32 with the gap 47. 
Thus, a compensating force is generated in gap 47 which has a force 
component F.sub.D which opposes the relative movement of the juxtaposed 
bearing member pair 14, 15. 
An analogous situation exists for the other juxtaposed bearing member pair 
16, 17. In this case, a compensating force component F.sub.D is similarly 
generated in gap 48 which is bounded by bearing members 16 and 17. 
Now, with particular reference to the force vector diagram of FIG. 2, 
vector F.sub.hydr /2 identifies a proportionate fraction of the entire 
hydraulic force F.sub.hydr which acts to urge bearing member 14 along a 
direction in which the bearing member 14 is not only urged against the 
inner circumferential wall of chamber 13, but also is urged towards the 
other bearing member 15. The generated compensating force has a force 
component F.sub.D which, when vectorially added to vector F.sub.hydr /2, 
produces a resultant force F.sub.R. Resultant force F.sub.R is shown in 
dashed lines in FIG. 2, and its constituent parts are identified in FIG. 4 
by force component F.sub.G and force component F.sub.A. 
It will be noted that the original hydraulic force vector F.sub.hydr /2 has 
been effectively modified to assume the magnitude and direction of the 
resultant force F.sub.R. This means that the force which tends to move 
bearing members 14 and 15 towards each other has been correspondingly 
reduced. This modification of the forces acting on gear 14 results 
therefore in the desired greatly reduced play in the operation of the 
machine. 
The magnitude of vector F.sub.A is very small and, ideally, this magnitude 
is zero. The magnitude of F.sub.A is of course dependent upon the 
magnitude of the force component F.sub.D which in turn depends upon the 
size of the gaps 47, 48. For high volumetric discharge pumps the gaps 
between the bearing members may not be adequate to produce a sufficiently 
strong compensating force. Therefore, additional gaps may be arranged at 
the periphery of the bearing members, for example at the low pressure side 
of the machine. 
The additional forces generated in such gaps are operative for properly 
dimensioning the resultant force so that the magnitude of the force 
components thereof, i.e. F.sub.A and/or F.sub.G may be selected and 
adjusted as desired. The invention thereby contemplates providing at least 
one and preferably a plurality of high-pressure areas at any desired 
location about the periphery of the individual bearing members. These 
high-pressure areas are operative for preventing undesired movement, such 
as movement of juxtaposed bearing members towards each other and/or 
movement of the bearing members against a circumferential wall of the 
chamber. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
gear-type fluid displacing machine, it is not intended to be limited to 
the details shown, since various modifications and structural changes may 
be made without departing in any way from the spirit of the present 
invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.