Variable volume positive displacement rotary pump

A tubular cylinder block is mounted for rotation about its axis within a cylindrical bore of a pump housing. The pump housing has circumferentially spaced inlet and outlet ports opening radially to the bore. Right angle intersecting diametric passages extend through the cylinder block and are alignable with the inlet and outlet ports during rotation of the drive block, the diametric passages being square in cross-section, and piston members of corresponding square transverse cross-section are slidably positioned within respective diametric passages with the piston members bearing square slots within side faces thereof intermediate of their ends facing axially. A square drive block is carried commonly within the piston member slot whose axis of rotation is adjusted eccentrically relative to the axis of rotation of the cylinder block. Cylinder block internal peripheral grooves separated by lands control fluid passage via the piston formed cavities between the inlet and outlet ports.

FIELD OF THE INVENTION 
This invention relates to positive displacement rotary pumps, and more 
particularly, to such rotary pumps whose volume or capacity may be readily 
adjusted. 
Positive displacement rotary pumps have long been employed for pumping oil 
and light incompressible fluids and in which a rotary member is mounted 
eccentric to the axis of the cylinder within which it is placed, and 
wherein radial, sliding blades are borne within the rotary member, and 
wherein working chambers as defined by the cylindrical bore of the fixed 
housing or casing, the rotary member rotating about its axis but eccentric 
with respect to the axis of the bore and the sliding vanes decrease in 
volume between circumferentially spaced inlet and outlet port locations, 
opening radially of the interior of the cylindrical bore housing these 
members. While such pumps are quite capable in operation, they have 
certain deficiencies. The limited contact area between the moving elements 
and the fixed elements of the pump result in high wear, noise and fatigue 
of these parts. 
SUMMARY OF THE INVENTION 
The present invention is directed to an improved variable volume rotary 
pump which comprises a pump housing having a cylindrical bore. An annular 
cylinder block having a diameter on the order of the pump housing bore is 
mounted concentrically within the bore for rotation about its axis. 
Circumferentially spaced inlet and outlet ports are provided within the 
housing which are in radial plane alignment. At least one diametric 
passage extends through the cylinder block at right angles to its axis of 
rotation, and piston members in the area of crossing each bear a square 
slot within their side faces facing axially of the cylinder block. These 
form connected rectangular pistons on each side of the square slot for 
each respective piston member. A square drive block is carried jointly 
within the piston member slots. Means are provided for adjusting 
eccentrically, the drive block axis relative to the axis of the cylinder 
block. Motor means are provided for driving the cylinder block about its 
axis of rotation, whereby the square pistons slide within the diameteric 
passages during rotation, but the pistons are prevented from rotation and 
contact between themselves, and wherein the increase in contact area 
between the pistons and the cylinder block tends to reduce wear, noise and 
fatigue of the pistons. Cylinder block internal peripheral grooves 
separated by lands control fluid passage via the piston formed cavities 
between the inlet and outlet ports. 
Preferably, an electric drive motor has a motor drive shaft projecting from 
one end thereof which engages the cylinder block on one side thereof. An 
adjustment shaft may be coaxially fixedly mounted on the side of the 
cylinder block opposite that connected to the motor drive shaft. The 
eccentric adjustment shaft bears a cylinder or eccentric on one end 
thereof which is eccentric with respect to the axis of the eccentric 
adjustment shaft and which is carried within a circular bore of the drive 
block shaft such that the drive block rotates on its circular bore. A 
cylindrical stuffing box bears the eccentric adjustment shaft, the 
eccentric adjustment shaft slidably supporting a gland nut having threaded 
to the exterior thereof, a lock nut which, in turn, threadably abuts the 
end of the stuffing box. The gland nut has an end received within the 
stuffing box and which longitudinally bears on packing such that, backing 
off the gland nut, permits seal adjustment of the shaft. The gland nut is 
then tightened to vary the seal, whereupon, the lock nut is tightened 
against the end of the stuffing box cylinder to set the seal. 
The pump housing may comprise a cylindrical member. The inlet and outlet 
ports may be diametrically opposite each other, and the cylindrical 
housing bore includes peripheral recesses between the inlet and outlet 
ports which are closed off intermediate the inlet and outlet ports by a 
land. Further, a longitudinal recess within the bore extends from the 
inlet port to a point longitudinally beyond one end of the cylinder block. 
The casing further comprises a bypass outlet port within the casing in 
fluid communication with the longitudinal recess such that when the pump 
is not operating, the bypass outlet port functions to maintain the pump at 
constant operating temperature. The cylinder block may be provided with an 
axial opening of rectangular transverse cross-section and the motor shaft 
may carry on the end of the shaft facing the cylinder block a rectangular 
drive plate operatively coupled to the motor shaft for rotation therewith. 
The drive plate has a portion projecting within the drive block 
rectangular opening corresponding in configuration and size to such 
opening whereby the rectangular drive plate, in turn, drives the cylinder 
block about its axis during rotation of the motor shaft. Preferably, a 
damper motor is connected by means of suitable linkage to the eccentric 
adjustment shaft and the eccentric is rotated by the shaft automatically 
to provide the required input.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, there is shown a variable volume positive 
displacement rotary pump, indicated generally at 10, the pump 10 being 
mounted to the end of a drive motor 12 and being coupled mechanically to 
the drive motor shaft 14 such that the pump 10 operates upon energization 
of the electric drive motor 12. The pump 10 comprises a cylindrical pump 
housing indicated generally at 16 which terminates at one end 16a in a 
radially outwardly directed flange 18 through which, at spaced 
circumferential positions, extend holes or openings 18a which receive 
bolts 20 for locking the pump housing to the end of a motor housing 12a of 
the motor 12. A gasket 22 is interposed between the flange 18 of the pump 
housing 16 and the end of the motor housing 12a. The cylindrical housing 
16 is open at both ends with the end 16b, opposite that 16a bearing the 
flange 18, having mounted thereto, an end plate 21. End plate 21 is 
circular in form and is mounted to the cylindrical pump housing 16 by 
means of a plurality of cap screws 30 with the end plate being sealed to 
the pump housing 16 by way of gasket 24. The pump housing 16 may be of 
cast construction or, alternatively, it may be machined so as to include a 
cylindrical bore 26 and a counterbore 28 constituting an enlarged diameter 
cavity on the right side of the pump housing, as seen in FIG. 1. Cast, 
machined, or otherwise formed within the cylindrical pump housing 16, are 
diametrically opposed inlet and outlet ports as at 38, 40, respectively, 
the ports 38 and 40 being in generally transverse planar alignment and 
displaced longitudinally relative to the third port 42 constituting a 
bypass outlet port for the pump. The port 42 is in general longitudinal 
alignment with the outlet port 40 and opens to the bore 26 as does the 
inlet and outlet ports 38 and 40, respectively. Rotatably mounted within 
the housing bore 26 is annular cylinder block 44. Block 44 and the other 
components of the pump are preferably formed of metal. The diameter of the 
cylinder block 44 is slightly less than the diameter of bore 26 so as to 
sealably fit within this bore and thus being supported for rotation about 
its axis coaxial with the bore 26. Bore 26 and counterbore 28 form a 
radial shoulder as at 29, and bore 26 at this end is closed off by way of 
a back plate 32. Back plate 32 is annular in form and is mounted to the 
pump housing 16 by way of a plurality of circumferentially spaced cap 
screws 34, the back plate 32 being sealed relative to bore 26 by way of 
annular sealing gasket 36. 
The annular back plate 32 is provided with a bore at 32a and a counterbore 
at 32b through which the motor drive shaft 14 projects. The motor drive 
shaft 14 is provided with a longitudinal keyway 14a which is rectangular 
in cross-section and within which fits a rectangular striplike key 51. 
Mounted to the motor shaft 14 is a cylindrical drive coupler 48 which 
bears a rectangular recess longitudinally within the same, as at 48a which 
is in alignment with the keyway 14a within motor shaft 14. The key 51 is 
inserted within aligned slots 14a and 48a to lock the drive coupler 48, 
and the drive coupler 48 is forced to rotate with shaft 14 when the motor 
12 is energized. The drive coupler 48 is cylindrical in form and 
terminates at its end opposite motor 12 in an axial projection 48b of 
rectangular cross-section which extends diametrically across the end of 
drive coupler 48. The cylinder block 44 is provided with a rectangular 
and, preferably, as illustrated, square opening 44e formed by opposed 
walls 44a and 44 b and right angle opposed walls 44c and 44d, 
respectively. Mounted within the right end of the square opening 44e of 
the cylinder block 44 is a squared off drive plate 46 having a square 
projection portion formed by opposed faces 46b and right angle opposed 
faces 46c, the opposed portion of this member being extended by way of 
flanges as at 46d which act as axial stops and prevent further projection 
of the drive plate within the square hole 44e of the drive block. 
Centrally within the face 46e of the drive plate, is a transverse, 
rectangular slot 46a within which is fitted the rectangular 
cross-sectional axial projection 48b of the drive coupler 48. 
As may be appreciated, when shaft 14 rotates, the drive coupler 48 which is 
keyed thereto, causes the projection 48b of the drive coupler 48 fitted to 
slot 46a of the drive plate 46, to drive plate 46 about the axis of shaft 
14. Since the drive plate projection 46b is fitted to the square opening 
44e of the cylinder block 44, the cylinder block 44 necessarily rotates 
about its axis coaxially within the pump housing bore 26. 
The cylinder block 44 is further provided with diametrically extending and 
right angle intersecting passages 49 and 50. In the position of the 
cylinder block 44, as shown in the drawings, passage 49 is horizontal and 
passage 50 is vertical, the passages opening up to the square hole 44e 
which extends axially within the cylinder block 44 and at right angles to 
passages 49 and 50. Slidably positioned within passages 49 and 50 are 
respectively pistons or piston members 45 and 47. Both of these piston 
members take the form of rectangular blocks having square transverse 
cross-sections, dimensioned slightly less than and being slidably fitted 
within respective diametric passages 49 and 50. Passages 49 and 50 are 
slightly axially offset. Further, each of the piston members is slotted 
intermediate of its ends to form rectangular slots as at 45a for piston 45 
and as at 47a for piston 47. This forms for piston member 45, pistons 45b, 
45c, which are connected at 45d, and for piston member 47, pistons 47c and 
47b at respective ends of piston member 47 connected at 47d. The 
rectangular slots as at 45a for piston member 45 and 47a for piston member 
47 open to the square hole 44e within the cylindrical drive block 44 and 
the piston member slots 45a and 47a face the end of the pump remote from 
the electric drive motor 14. The slots 45a and 47a are dimensioned so as 
to closely receive the piston members. It should be noted that the square 
cross-section diametric passages 49 and 50 are slightly axially offset 
from each other the distance of the thickness T of the portions 45d, 47d 
connecting the piston members 45 and 47. In general, the plane of rotation 
of the piston members 45 and 47 within the cylindrical drive block 44 
correspond with the transverse or radial plane extending through the axes 
of the diametrically opposed inlet and outlet ports 38 and 40, 
respectively. The square drive block 52 may be cubic in form with four 
equally dimensioned right angle sides which are dimensioned to the slots 
45a and 47a of the piston members 45 and 47 and are closely received 
within these slots when the piston members 45 and 47 are slidably mounted 
within the diametric passages 49 and 50, respectively, of block 52. 
Drive block 52 bears an axial bore 52a which receives a cylinder or 
eccentric 60 having a diameter essentially equal to that of or slightly 
smaller than the bore 52a of the drive block 52 within which the eccentric 
60 is positioned. In turn, the eccentric 60 is fixed to one end of an 
eccentric adjustment shaft 62, the eccentric or cylinder 60 being 
eccentrically mounted with respect to the axis of shaft 62. When the shaft 
62 rotates, the eccentric 60 rotates eccentrically about the axis of shaft 
62. Thus, the drive block 52 axis of rotation shifts in an eccentric 
manner. The eccentric adjustment shaft 62 projects outwardly of the pump 
housing end plate 21. The end plate 21 is provided with a tapped and 
threaded bore 54 which threadably receives one end 66a of a cylindrical 
stuffing box member indicated generally at 66. The stuffing box member 
portion 66a is threaded on its exterior as at 68, and is threadably locked 
to the end plate 21. The stuffing box member 66 is provided with a bore 
66b, and bears an annular internal recess 70, within which is carried 
stuffing box packing 72. Also slidably mounted on the shaft 62 is a 
cylindrical gland nut indicated generally at 74 provided with a hex end 
74a and being threaded over the major portion of its outer periphery as at 
74b. End 74c of the gland nut 74 presses against the end of the packing 
72. The stuffing box member 66 is threaded as at 66d to threadably engage 
the threaded portion 74b of the gland nut 74. In turn, the gland nut 
threaded portion 74b carries a lock nut 76 which is threaded internally as 
at 78 and which, when rotated, bears against the end 66c of the stuffing 
box member to lock the gland nut 74a in an axial position compressing the 
packing 72, thereby insuring that a fluid seal exists for eccentric 60 
regardless of its angular eccentric position about shaft 62 axis, which 
defines the eccentric position of the piston drive block 52 rotating on 
eccentric 60. 
It may be further ascertained that a positive displacement pumping action 
occurs due to the cooperative nature between the sliding piston members 
and the pump housing which bears upper and lower cooperating internal 
peripheral grooves as at 16A and 16B, respectively, which intersect the 
inlet and outlet ports 38, 40, respectively, and which are separated by 
non-grooved portions defining lands 16C and 16D, which in the illustrated 
case are diametrically opposite and at right angles to inlet and outlet 
ports 38, 40. While the upper groove 16A communicates fully over its 
arcuate extent with outlet port 40, and while the lower groove 16B is open 
throughout its arcuate extent with inlet port 38, communication is 
effected by way of the cavities or volumes formed between the 
reciprocating piston members and the diametric passages 49 and 50, within 
which the piston member slides. 
Under the circumstances as seen in FIG. 3, a fluid entering the inlet port 
38 fills the portion of the diametric passage 50 at the end of piston 
member 47b when that passage is aligned with the port 38 at that moment. 
Piston member 47b and its cylinder block 44 defines a pumping chamber V of 
given volume. As the cylinder block 44 rotates about its axis, in the 
direction of the arrow, FIG. 3, the drive block 52 is forced to rotate 
about the axis of the eccentric cylinder 60 and causes the piston member 
47 to slide within diametric passage 50 (as does piston 45 within passage 
49). In the instant case, the piston 47b when moving, due to rotation of 
cylinder block 44, from its position shown in FIG. 3 to a position just 
prior to that occupied by piston 45b, causes an increase in the volume V 
to a much increased value V" prior to opening the chamber to the outlet 
port 40 for discharge. The intermediate volume V" is shown at that instant 
for piston 45b, which is cut off from the inlet and outlet ports by land 
16C, the reciprocating action of the pistons changing the volume of the 
working chambers as defined by the pistons and the diametric passages 49 
and 50 within cylinder block 44 which bear these passages. 
As can be appreciated, subsequent to the volume V" being cut off to the 
inlet port 38 via the lower groove 16B, it opens to the outlet port via 
the upper groove 16A and its volume diminishes to volume V'. FIG. 3, 
therefore, shows the eccentric to the left and therefore the maximum 
output or maximum flow conditions for the positive displacement pump. As 
may be further appreciated, during continued counterclockwise rotation, 
the piston member in moving from the outlet port 40 back towards the inlet 
port 38 passes by land 16D. At this point, with the eccentric positioned 
as shown in FIG. 3, the piston member as evidenced at 45c will be extended 
the maximum towards the outside, that is, radially outwardly nearly 
touching the section of the housing between the circular grooves or 
passages 16A and 16B at land 16D. However, as the cylinder 44 continues to 
rotate, the cavity opens within cylinder block diametric passage bearing 
the piston member and communicates with the lower groove 16B, allowing oil 
to flow through the inlet and passage or groove 16B for reception into the 
cavity provided by the diametric passage bearing piston member. As may be 
appreciated, it is not necessary that the inlet and outlet ports 38 and 40 
be diametrically opposite each other, and in fact in some circumstances, 
this would not be desirable. It is only necessary that the ports connect 
to their respective grooves or passages as at 16A, 16B, and that they be 
separated by way of lands as at 16C, 16D. 
As may be appreciated by viewing FIG. 2, particularly in conjunction with 
FIGS. 1 and 5, the eccentric adjustment shaft 62 is rotated by an 
appropriate mechanism, whereupon, the axis of the eccentric 60 may be 
shifted 90.degree. from that shown in FIG. 3, with shaft 62 rotating 
90.degree. about its axis and causing a corresponding eccentric shift for 
the piston drive block 52. This will change the pump 10 from its maximum 
capacity condition, as illustrated in FIG. 3, to zero capacity or 
completely unloaded condition, as seen in FIG. 2. In this case, the 
working chamber volume V" in FIG. 3, 90.degree. to the bottom opening to 
the inlet 38 is equal to the volume V'" diametrically opposite thereto, 
that volume having changed from intermediate values as at V and V' in this 
figure. While not shown, further rotation of the eccentric 60 in the 
direction of arrow 61, FIG. 3, will permit the pump to be reversely 
operated, that is, outlet 40 can become an inlet and inlet 38 can become 
the outlet 40 for the pump. However, this will affect specific 
arrangements made for bypassing the flow under circumstances where the 
pump is not permitted to positively drive fluid from inlet port 38 to 
outlet port 40. 
In this respect, the pump housing 16 at the bore 26 is provided with an 
annular elongated groove or bypass channel 27 which extends the length of 
the bore 26, intersecting inlet port 38 at its center and extending well 
past the side of the cylinder block 44 facing the back plate 32. The 
portion of the bore 26 not occupied by the cylinder block 44 forms a 
cavity 17, not only within which is located the drive coupler 48 coupling 
motor drive shaft 14 to the cylinder block 44 via drive plate 46, but also 
fluid connecting the bypass channel 27 and thus the inlet port 38 to the 
bypass outlet port 42. This allows flow through the pump via the inlet 
port 38 and the bypass outlet port 42 when the pump is not operating, to 
maintain the pump at constant operating temperature. 
In the illustrated embodiment of the invention, a gear motor which is 
schematically shown in FIG. 1, is connected mechanically as shown in 
dotted line fashion at 11 to shaft 62 to match oil flow to demand, the 
eccentric being rotated by the shaft automatically to provide the input 
required to the pump. 
A further aspect of the present invention is the nature in which the drive 
plate axial projection is spring biased into the square opening 44e within 
the cylinder block 44 and the cylinder block 44 in turn is forced against 
the end plate 21 while maintaining a mechanical seal between the driven 
cylindrical drive coupler 48 and the back plate 32 at the opening through 
which both shaft 14 and the drive coupler 48 project into pump housing 
cavity 17. 
An annular ring 58 is mounted to the cylindrical drive coupler 48 adjacent 
drive plate 46 against which one end of a biasing compression coil spring 
63 abuts while the opposite end of the coil spring 63 abuts against a 
radial shoulder of a collar 56 which slides upon the cylindrical drive 
coupler 48 and which, in turn, presses a ring seal 54 of rectangular 
radial cross-section against a fixed mechanical seal 53. Seal 53 is of 
L-shaped radial cross-section and is borne within counterbore 32b to abut 
a shoulder 32c defined by bores 32a and 32b within the back plate 32. 
Thus, the compression coil spring 63 performs one function in axially 
biasing the pump cylinder block 44 to the left, maintaining the piston 
members in contact with the drive block 52 and the diametric passages 48 
and 50 properly aligned with the normal flow plane for the fluid being 
pumped as defined by the aligned axes of the inlet port 38 and outlet port 
40. Spring 63 further biases the seal member 52 to the right, sealing off 
chamber 17 from a chamber 19 on the right side of back plate 32. 
While the invention has been particularly shown and described with 
reference to a preferred embodiment thereof, it will be understood by 
those skilled in the art that various changes in form and details may be 
made therein without departing from the spirit and scope of the invention.