Improvements in Rotary Gear Pumps.
Year: 1896

page_text: Date of Application, 26th Mar., 1896-Accepted, 2nd May, 1896
COMPLETE SPECIFICATION.
Improvements in Rotary Gear Pumps.
I, MILAN WOODBURN HALL, of Number 87 John Street, in the City of New
York, in the County and State of New York, United States of America, Pump
Manufacturer, do hereby declare the nature of the said invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement:-
This invention relates to rotary gear pumps, in which two gear wheels in a closely
fitting casing, having inlet and outlet openings, rotate with their teeth in mesh, so
that as they turn the water is carried around in the spaces between their teeth
from the inlet to the outlet of the pump. Such pumps, although long known, have
been almost useless for general purposes because the pressure of the water lifted
has forced the gears against their bearings and the walls of the casing with so
much power that great friction and wear has resulted. The friction has been so
great that most of the power used in revolving the pump gears has been consumed
in friction, and the wear has soon made the gears so loose that they leak and
permit a back flow of water between the gear wheels and the casing.
My invention consists in avoiding these two disadvantages by balancing the
pressure on opposite sides of the gears, by providing ducts communicating from
the space between the teeth on the one side to the space between the teeth on the
other side, so that the pressure on each side shall be equal, and the gears will be
relieved from the friction and wear before existing. These ducts may extend
diametrically across the gear. In actual use the ducts are found to more than
double the efficiency of the pump and to avoid all friction and wear.
In the drawings,
Fig. 1 is a side elevation of a pump having three gears;
Fig. 2 is an end elevation thereof;
Fig. 3 is a cross section thereof cut on the lines 3-3 in Figs. 1 and 4 and
looking in the direction of the arrow, and
Fig. 4 is a horizontal section thereof on the line 4-4 in Figs. 2 and 3;
Fig. 5 is a plan view of one of the improved gears, partly in axial section,
showing the cross ducts;
Fig. 6 is a cross section of a pump having only two gears, and
Fig. 7 is a rear view thereof."
Figs. 5, 6 and 7 show the simplest and preferred construction, and I will first
describe my improvements as therein shown.
In this construction the casing A¹ has the usual two cylindrical chambers B¹
and intermeshing gears C. These gears are long toothed pinions, the teeth of.
which are accurately finished to make a close fit with each other and a close
working fit with the side walls of the chambers B'. The gears are mounted on
shafts D¹, one of which is driven by a pulley, or from a motor, or belt, as desired.
The water enters through a suction pipe El and port a, passes around in the
spaces between the teeth, and is discharged through a port b and discharge pipe F¹.
As thus far described the construction is the same as that of the well known gear
pump, which, although long known, has not been much used because the weight
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Fig. 4 is a horizontal section thereof on the line 4-4 in Figs. 2 and 3 ;
Fig. 5 is a plan view of one of the improved gears, partly in axial section,
showing the cross ducts;
Fig. 6 is a cross section of a pump having only two gears, and
Fig. 7 is a rear view thereof.
Figs. 5, 6 and 7 show the simplest and preferred construction, and I will first
describe my improvements as therein shown.
In this construction the casing A₁ has the usual two cylindrical chambers B¹
and intermeshing gears C. These gears are long toothed pinions, the teeth of.
which are accurately finished to make a close fit with each other and a close
working fit with the side walls of the chambers B'. The gears are mounted on
shafts D, one of which is driven by a pulley, or from a motor, or belt, as desired.
The water enters through a suction pipe E¹ and port a, passes around in the
spaces between the teeth, and is discharged through a port b and discharge pipe F¹.
As thus far described the construction is the same as that of the well known gear
pump, which, although long known, has not been much used because the weight
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page_text: of the water lifted, by bearing on the discharge side of the gears forces them
against the wall with such friction that it requires too much power to drive the
gears and that they are soon worn loose and leak, and this bad effect is added to
by the suction of the water on the suction side, which draws the gears against the
wall to an additional extent. If in raising a column of water from a lower to a
higher level there is a pressure of twenty pounds per square inch at the discharge
side of the pump, this pressure in the space 10 would force the gear toward the
opposite wall with a twenty pound pressure per square inch, and if on the suction
side there is a suction of ten pounds per square inch this suction in the space 1
would draw the gear toward the wall with a force of ten pounds per square inch.
In the spaces 2 to 9 the effect of the pressure would vary from a suction pressure
to a discharge pressure. As the gears rotate very rapidly, under this pressure the
bearings are soon worn away and the teeth are pressed against the wall and also
worn loose. A large part of the power is required to overcome this friction.
To avoid this disadvantage 1 provide cross ducts c extending diametrically, or
in other suitable way, across and through the gears from one space to the other,
through which ducts the pressure on one side can be communicated to the other
side so that it will be exactly balanced on each side of the gear. These ducts
may be bored across as shown in Figs. 5 and 6, or arranged in any suitable way.
One small diametrical bore between the spaces is sufficient. The shaft may have
an annular groove c¹ connecting this bore as shown in Figs. 5 and 6, so that each
bore is separated from those of the other spaces. Thus the pressure in the
space 10 will be communicated through the duct to the space 4, that in the space 9
to the space 3, and that in the space 1 to the space 7, and so on. Only a minute
flow of liquid through the duct is required to equalize the pressure in both
spaces, as both spaces are already filled with liquid, hence no loss through the
ducts occurs, and the gears are so perfectly balanced that the gears run without
-friction-or-wear, permitting all the force for driving the pump to be exerted in
lifting the water.
In actual use of the pump shown in Fig. 6, by coupling it to an electric motor
and running it at various speeds and under varying water pressures, I find the
following results when the balancing ports are opened to balance the gears, and
when they are closed by plugging them up to correspond to the old pumps :-

page_text: Thus it will be seen that with the driving of the pump with the balancing cross
ports the efficiency, in proportion to the power required, is very much greater
than is the case when the balancing ducts are not used. Aside from this, in actual
use with the continuous running of a pump for a year it is found that neither the
gears nor the bearings are noticeably worn when the balancing ports are used, and
that the pump runs noiselessly even at high speed.
I prefer to make one of the gears of brass or metal and the other of hard
rubber or composition, as I find that the gears thus constructed work more
smoothly than if both are made of metal.
Having described the simplest construction containing my improvements, I will
now describe the construction shown in Figs. 1 to 4, in which an ordinary gear C,
carried by a shaft D, is arranged between the two pinions and drives them in
opposite directions, and the suction and discharge passages E and F are divided,
so that the flow shall pass from the suction chamber e, partly through the port a,
and partly through a cross duct hd h into the suction chamber e', and through the
port a', to the balanced gears C, by which the water is carried through the
chambers B and discharged, part through the port b, aud part through the port b',
into the chamber f, and through the cross duct i, d, i, into the discharge
chamber f, and to the discharge passage F, as shown by the arrows. The ports d
and d' are formed in the heads g 9. Caps j cover the ends of the shafts D', and
the stuffing box k prevents leakage around the driving shaft D. The ducts c c
here balance the gears C¹, and the middle gear C is balanced by its location
relatively to the others and to the ports a a' and bb'.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In rotary gear pumps, having two or more toothed pinions revolving in
chambers in a casing, and having suction and discharge ports, ducts extending
across the pinions from the spaces between the teeth on one side to the spaces
between the teeth on the other side, for balancing the pressures on the opposite
sides of the pinion, substantially as set forth.
2. In rotary gear pumps having two or more pinions revolving in chambers in a
casing with their teeth in engagement, ducts extending diametrically through the
pinions for communicating the pressure between the opposite sides of the pinions,
substantially as set forth.

page_text: 3. A pinion for rotary gear pumps having ducts formed through it from the
space between its teeth on one side to the space between its teeth on the other side,
substantially as set forth.
4. A rotary gear pump having a casing having cylindrical chambers, and two
or more gear wheels rotating in said chambers, one of said gear wheels being of
hard rubber or composition and the other of metal, substantially as set forth.
5. A rotary gear pump having three intermeshing gear wheels revolving in
chambers and balanced as shown in Fig. 3.
6. The improvements in gear pumps substantially as described and shown.
Dated the 23rd day of March 1896.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.