Drive transmission means

This invention provides apparatus for use in a drive transmission system comprising a pump adapted to perform work on a medium and means repetitively and automatically to unload the pump. When connected with a flywheel driven by a prime mover an embodiment alternately performs work and then is unloaded to permit acceleration of the flywheel. In use in a driven transmission system there is provided a flywheel driven by an engine, a pump driven by the flywheel, powered by the pump, and means repetitively to unload the pump permitting the engine to accelerate the flywheel and compensation means to power the hydraulic motor while the pump is unloaded. The pump is preferably a rotary positive displacement pump having relief galleries eliminating the seal between pumping elements driving each cycle.

TECHNICAL FIELD 
This invention relates to means for transmitting power from a prime mover 
to a load. 
In transmitting power from a prime mover to a load provision must commonly 
be made for variation in load demand. Frequently the prime mover is 
incapable of responding to such variation by increasing energy output with 
desired rapidity or such response can be achieved only by inefficient 
operation of the prime mover. 
BACKGROUND ART 
An example is a motor vehicle having an internal combustion engine as prime 
mover and propelling the vehicle as load. 
The vehicle is provided with a gear box between the engine and the load to 
provide torque conversion enabling the engine to run in a power output 
range and at a speed of revolution range in which the engine operates 
efficiently, notwithstanding load variation, for example when the vehicle 
travels up a hill. 
Nevertheless the engine cannot operate at its optimum efficiency under all 
conditions because the gear box provides for change of gear ratios in 
discrete steps. 
Moreover rapid acceleration within any gear ratio can only be achieved by 
carburetting a fuel rich mixture which is inefficiently utilised by the 
engine and is wasteful of fuel. Alternatively the engine may be operated 
at optimum fuel economy but at the expense of slower acceleration. 
Embodiments of the present invention provide means of operating such a 
motor at a more nearly constant fuel consumption and at close to optimum 
engine efficiency, while permitting periods of vehicle acceleration at a 
rate which is independent of engine speed of revolution. 
Furthermore embodiments of the invention provide a more or less 
continuously variable torque conversion in transmission of power from a 
prime mover to a load and may be used in substitution for a gear box. 
In some embodiments it is possible to deliver more torque to the load than 
could instantaneously be provided by the prime mover. 
According to a first aspect the invention consists in apparatus for use in 
a drive transmission system comprising: 
a pump adapted to be driven to perform work on a medium, 
and means repetitively and automatically to unload the pump. 
According to a second aspect the invention consists in apparatus for use in 
a driven transmission system comprising: 
a flywheel driven by a prime mover 
a pump driven by the flywheel to perform work on a medium and means 
repetitively to unload the pump whereby to permit acceleration of the 
flywheel. 
According to a third aspect the invention consists in drive transmission 
means for transmitting power from a prime mover to a load comprising: 
a flywheel driven by the prime mover, 
a pump driven by the flywheel, 
a hydraulic motor powered by the pump, 
means repetitively to unload the pump thereby permitting the prime mover 
repetitively to accelerate the flywheel; and 
compensation means to power the hydraulic motor while said pump is 
unloaded. 
According to preferred embodiments of the invention the pump is a positive 
displacement pump, and more preferably a rotary positive displacement 
pump, provided with relief galleries which eliminate the seal between 
pumping elements during a part of each stroke or revolution, whereby the 
pump is repetitively unloaded.

With reference to FIG. 1, there is shown schematically an embodiment of 
drive transmission means according to the invention. The apparatus is 
intended to deliver power from a conventional engine (not shown) from 
which torque is to be transmitted to an output shaft 2 for driving a load 
(not shown in FIG. 1). 
A main shaft 3 supported by bearings 1 is coupled at one end for example by 
inter-engageable splines 4 with the engine whereby main shaft 3 may be 
driven in axial rotation. A pump, indicated generally at 5, having an oil 
inlet indicated at 6 fitted with a filter 7, and having an outlet 8 fitted 
with a non-return valve 9, is driven from main shaft 3. 
In the present example pump 5 is a rotary positive displacement pump of a 
type to be described in more detail hereinafter which is provided 
internally with means, also to be described, whereby the pump is 
repetitively unloaded. Specifically the pump is loaded during a first and 
third quarter revolution of main shaft 3 producing a high pressure at pump 
port 8 while during a second and a fourth quarter revolution of main shaft 
3 the pump is unloaded. That is to say, pump 5 utilises power supplied to 
it during two quarter revolutions to raise oil to high pressure while 
during the remaining two quarter revolutions the pump performs 
substantially no work and is freely rotatable. 
Pump 5 is mounted in a sump 10 and the high pressure pump outlet port 8 
communicates via a high pressure manifold 11 with the inlet side 12 of a 
hydraulic motor indicated generally at 13 whereby output shaft 2 is driven 
in rotation. Oil from the outlet side 14 of motor 13 is returned to sump 
10. A valve may be provided whereby the direction of flow of hydraulic 
fluid from manifold 11 through motor 13 may be reversed permitting the 
motor and consequently output shaft 2 to be driven in clockwise or 
anticlockwise rotation. 
The torque delivered by motor 13 is controlled by the bleed of fluid from 
manifold 11 via a valve having a valve orifice 20 communicating with a 
bypass return line 21 which returns oil to sump 10. The ratio of the 
amount of oil returning to the sump by motor 13 to the amount bypassing 
motor 13 through return line 21, that is to say the pressure of oil 
supplied to motor 13, is controlled by valve rod 22 which is actuatable to 
open or close valve orifice 20. 
High pressure oil manifold 11 also communicates with a high pressure oil 
stabiliser indicated generally at 23. Oil stabiliser 23 comprises a large 
diameter control air cylinder 24 fitted with an air piston 25 movable 
slidably therein and providing a seal with the walls of cylinder 24 so 
that air piston 25 divides cylinder 24 into a low pressure side 26 and a 
high pressure side 27. A piston rod 28 is connected at one end to the low 
pressure side of air piston 25 and, at the other end, to a small diameter 
oil piston 29 slidable within oil cylinder 30 and providing a seal 
therewith. Valve rod 22 has one end connected on the side of oil piston 29 
opposite the side of connection of piston rod 28 thereto and is co-axial 
with piston rod 28. The other end of valve rod 22 is slidable in a valve 
seating so as to control oil flow from manifold 11 via valve inlet 16 and 
valve orifice 20 to oil bypass return pipe 21 which has a diameter greater 
than that of valve rod 22. 
A compressor 30A, in the present example driven by inter-engaging gears 31 
and 32 from main shaft 3 provides compressed air via a line 33 to the high 
pressure side 27 of air piston 25. The air pressure in the high pressure 
side of air piston 25, that is to say in the cylinder head, is controlled 
by valve means indicated generally at 34 connected between orifice 35 of 
the cylinder head and an air return line 36 communicating with the low 
pressure side 26. The low pressure side 26 is provided with an air inlet 
37 having a filter 38 communicating with the atmosphere and an outlet 35A 
communicating via air line 40 with the inlet side of compressor 30 whereby 
air is provided to compressor 30. Valve means 34 includes a valve head 234 
having a stem 235 extending through a valve seat orifice 236. Valve head 
234 is biased toward a seated position by a spring 237, and the passage of 
air through the orifice may be controlled by displacing valve head 234 by 
any conventional means, for example a lever acting on valve stem 235. 
Valve rod 22 is arranged so that when air pressure on the high pressure 
side of air piston 25 is at atmospheric pressure and oil manifold 11 is 
pressurised, oil pressure in manifold 11 drives oil piston 29 and air 
piston 28 to fully extended positions in which valve rod 22 opens valve 
orifice 20 fully, thereby permitting flow of oil to bypass line 21. 
Increase of air pressure can be used to drive valve rod 22 progressively 
to close off oil bypass of motor 13 at orifice 20, or close it completely. 
A flywheel 50 is fixedly mounted to shaft 3. 
In operation the engine may be operated for example at a constant throttle 
and thereby turns shaft 3 and flywheel 50. During the first and third 
quarter revolution of shaft 3 pump 5 is driven, supplying high pressure 
oil to manifold 11. A proportion of the oil is used to drive hydraulic 
motor 13 and the balance is returned via valve orifice 20 and bypass 21 to 
sump 10. The pressure of oil admitted to motor 13, and hence the torque 
delivered by the motor, may be varied according to the torque requirements 
at output shaft 2 by control of air pressure at the high pressure side of 
piston 25 by means of valve 34 and thereby control of valve rod 22. 
During the second and fourth quarter cycle of pump 5 no appreciable work is 
performed by the pump. During those periods the output of the engine 
therefore accelerates flywheel 50 storing energy as kinetic energy in the 
flywheel. During such periods the reservoir of oil contained in high 
pressure oil cylinder 30 is driven by air pressure acting on air piston 25 
via piston rod 28 and oil piston 29 to drive motor 13 and at the same time 
closing the bypass of oil via valve orifice 20, thereby acting to even out 
the pressure fluctuations in the high pressure oil manifold 11 and to 
provide a more or less constant average oil pressure to motor 13. 
It will be apparent that the torque transmitted from the couple of engine 
and flywheel 50 to shaft 2 can be varied continuously and that this is 
achieved by simple control means. Moreover more energy can be supplied for 
a short period to drive shaft 2 than is supplied during that short period 
by the engine, the additional energy withdrawn from the kinetic energy 
stored in the flywheel. In that event the flywheel is decelerated but can 
be again accelerated during following second and fourth quarter 
revolutions of shaft 3 occurring during periods when energy demand at 
output shaft 2 is less than the average supplied by the engine. It is 
therefore possible to drive the engine for example at optimum efficiency 
with respect to fuel consumption and to store the energy produced in 
flywheel 50. If energy supplied to the load exactly equals the output of 
the motor (ignoring losses which are minor) the flywheel will on average 
be neither accelerated nor decelerated. If the energy supplied to the load 
during a period is less than that provided on average by the motor, the 
surplus will be stored in the flywheel by acceleration thereof, and the 
stored energy will be available for subsequent consumption at a rate 
greater than the average output of the motor by deceleration of the 
flywheel. The system as a whole therefore performs at an optimum 
efficiency notwithstanding variations in load demand. 
With reference to FIGS. 2, 3 and 4 there is now described an embodiment of 
an apparatus which may be used as a hydraulic pump, as the hydraulic motor 
13 of FIG. 1 or as the air compressor 30A of FIG. 1. For simplicity its 
operation will be described first with reference to its use as a hydraulic 
pump. 
The pump comprises a housing 100 having a first port 101 which in the 
present example is an inlet port and a second port 102 which in the 
present example is an outlet port, a first rotor 103 fixedly mounted to a 
shaft 104 and a second rotor 105 fixedly mounted to a second shaft 106. 
Shafts 104 and 106 are parallel and are supported by bearings 108 mounted 
to parallel end walls 109 and 110 of housing 100. 
Shafts 104 and 106 project through end wall 109, high pressure oil seals 
117 being provided to prevent escape of oil from the housing interior, and 
shaft 106 is driven synchronously with, but in opposite sense to, shaft 
104 by means of intermeshing gears 111 and 112 mounted respectively to the 
shafts 104 and 106 externally of the pump and adjacent wall 109. 
Rotors 103 and 105 are of generally cylindrical shape and equal radii and 
are effectively in rolling line contact. However rotor 103 is provided 
with two protruding lobes 113 and 114 each of which in cross-section is 
shaped in the arc of a circle centred on the circumference of rotor 103, 
at diametrically opposite points thereof, and is adapted during rotation 
of the rotor to sweep fluid admitted at the inlet through a volume defined 
between rotor 103 and housing 100 to port 102. 
For this purpose the peripheries of lobes 113 and 114 are in close 
tolerance clearance with housing 100 between port 101 and port 102 in the 
direction of rotation of rotor 103. 
Rotor 105 is provided with depressions 115 and 116 which in cross-section 
are shaped in the arc of a circle of the same radius as that of lobes 113 
and 114 and centred on the circumference of rotor 105. That is to say 
depressions 115 and 116 of rotor 105 correspond in cross-section to the 
protrusion of lobes 113 and 114. 
Moreover the synchronisation of the two rotors during rotation is such that 
lobes 113 and 114 intermesh periodically with the depressions 115 and 116. 
At rotary angle of maximum intermesh the lobes are in contact with or at 
close clearance tolerance from the depression surface of rotor 105 over a 
cross-section corresponding to an arc, as shown in FIG. 2. Inlet port 101 
and outlet port 102 are centred on the chord of intersection of the 
circles of pump housing 100 at opposite ends of the chord. For preference 
at least the outlet port is slot-shaped and extends longitudinally in the 
axial direction. 
In operation of the apparatus of FIGS. 2 to 4 as a pump, fluid is admitted 
at port 101 and swept in the direction of port 102 by driven rotation of 
shaft 103. The fluid is substantially prevented from returning to the 
inlet port side by the seal formed between rotors 103 and 105 at the line 
of contact and is therefore expelled from port 102. 
By virtue of synchronisation of the rotors, lobes 113 and 114 may pass 
through the seal line while maintaining the seal. In addition some fluid 
from inlet 101 is carried in depressions of rotor 105 towards exit port 
102 where the progressive engagement of a lobe with the depression 
positively displaces the fluid carried from the depression ejecting the 
fluid in a trailing direction, and expelling it from the exit port. 
When used as an air pump the apparatus may be submerged in oil within a 
sealed sump. Filtered air is provided from outside the sump at atmospheric 
pressure via an air inlet line to the pump inlet. Air is ejected from the 
pump outlet into the surrounding oil and passes to a space above the oil 
level. A high pressure air outlet connection communicates with the space. 
For preference a baffle is provided in the oil above the pump outlet port 
and further baffles may be provided to prevent oil from being entrained 
with high pressure air drawn from the sump outlet connection. 
Oil enters the pump from the pump outlet port at least when the pump is not 
operated and, it is thought, during certain portions of its rotary cycle, 
thereby providing lubrication of the pump. 
When used as a hydraulic motor a hydraulic fluid under pressure may be 
admitted at one port whereby the rotors are driven and spent fluid at a 
lower pressure exits from the other port. In this case shaft 104 or 106 is 
extended externally of housing 100 to provide a drive shaft. 
There will now be described with reference to FIGS. 5 to 7 apparatus 
suitable for use as pump 5 of FIG. 1. 
The pump is in most respects similar to the apparatus shown in FIGS. 2-4 
and the same numerals are used in FIGS. 5 to 7 to identify parts 
corresponding to those of FIGS. 2-4. 
An important difference of the present pump from that described in FIGS. 2 
to 4 is the provision of means which periodically break the pump seal and 
thereby relieve the load on the pump. 
In the embodiment of FIGS. 5 to 7 there are provided 4 circumferential 
pressure relief recesses 120 extending over an arc subtending an angle of 
90.degree. at the rotor axis and each located along an edge of the rotor 
cylindrical portion and intermediate the lobes. 
In the present example the rotor has a width in the axial direction of 90 
mm and the recesses have a radial depth of 10 mm and an axial width of 10 
mm. 
The effect of pressure relief recesses 120 is that during operation of the 
apparatus as a pump in the manner described in relation to the apparatus 
of FIGS. 2 to 4, the pump of FIGS. 5 to 7 provides positive displacement 
during a first and third quarter cycle of rotor 103 while during a second 
and fourth quarter cycle the seal between inlet and outlet sides of the 
pump is broken by virtue of communication therebetween via pressure relief 
recesses 120 as shown in FIG. 7. 
Thus during the second and fourth quarter cycles substantially no work is 
performed by the pump of FIGS. 5 to 7. 
During the first and third quarter cycles commencing with reformation of 
the seal the volume contained between the line of seal at rotors 103 and 
105, outlet port 102, the leading surface of a lobe approaching the outlet 
port, and the surface of rotor 105 rapidly contracts, ejecting fluid 
contained in that volume and in the corresponding depression of rotor 105 
from the outlet at high pressure. 
The pump thus produces a pulsating output achieving high peak pressures 
during a first and third quarter cycle and is freely rotatable during a 
second and fourth quarter cycle. 
In other embodiments, apparatus according to the invention may be adapted 
to replace the clutch and gear box of a vehicle by being mounted in the 
transmission housing of the vehicle in substitution for the clutch and 
gear box. In that event, the transmission output shaft is connected, for 
example by a spline coupling, to a universal joint connected to the 
vehicle tail shaft and thereby to the load, in this case the vehicle, 
while the input shaft is connected via a splined coupling to the flywheel 
of the vehicle engine. With reference to FIG. 1, first shaft 3 is then 
supported by bearings from the transmission housing of the vehicle. Pump 5 
and motor 13 are housed within the transmission housing which acts as an 
oil sump. Main shaft 3 is in fact an extension of shaft 104 of pump 5. The 
external synchronising gears 111 and 112 of pump 5 and motor 13 are 
lubricated by the oil in the sump. 
In other embodiments of the invention, the prime mover may be of any kind, 
for example, an internal combustion engine, electric motor, a waterwheel 
or a man-powered pedal arrangement. 
The flywheel dimensions and weight should be selected having regard to the 
power output of the motor, the power requirements of the load and the 
storage capacity required. 
It will be understood that while use of pumps as described are highly 
preferred, they are not essential for performance of the invention. 
Any pump may be used if means are provided for relieving the load 
repetitively so that the flywheel can be accelerated. 
For example, a gear pump could be employed having grooves cut in certain 
gear teeth. 
Alternatively a reciprocating piston pump can be provided with longitudinal 
grooves along the cylinder wall over a part of the piston stroke. 
Moreover means external of the pump may be used to relieve pump load. For 
example, depending on the type of pump chosen, a pump may be arranged with 
a bypass line connecting the outlet to the inlet, the bypass line having a 
repetitively operated valve. The valve could be a rotary valve controlled 
from the main drive shaft or could for example be a solenoid valve 
electrically opened and closed repetitively. 
However it is essential that the pump be relieved by some means to permit 
energy storage in the flywheel. Furthermore it is not essential that the 
periods of no load be of equal duration with the periods of load. 
The use of the embodiment of motor and pump described has the advantages of 
simplicity and uniformity of design varying only in scale and therefore 
units of differing scale may easily be combined in a modular manner to 
meet the particular design requirements of a transmission system. 
Moreover the adoption of the pump to provide means of repetitively 
unloading it is achieved with simplicity. 
It will be understood that similar pumps having a fewer or greater number 
of lobes and having lobes of different diameter relative to the rotor, or 
having other profiles fall within the scope of the invention.