US Patent 2601003: Gear pump

June 17, 1952

Filed May 17, 1946

G.W. PONTIUS, TIT
GEAR PUMP

2,601,003

2- SHEETS--SHEET 1

June 17, 192

F£1ed May 17, 1946

G.W. PONTIUS, IE
GEAR PUMP

2,601,003

2 SHEETS---SHEET 2

/ TTO,qA/6"Y .

Patented June 17, 1952 2,601,003

UNITED STATES PATENT

1
This invention relates fo improvements in gear
pumps.
Since the advent of the gear pump there has
always been the problem of trapping fluid
tween the meshing teeth of the gears. Fiuid
trapped between the teeth adversely affects the
mechanical efiïciency and pump lire. Vrious
ways have been proposed for releasing this
trapped fiuid but all seem fo have some objec-
tionable feature which renders the pump im-
practical and/or expensive. Not a few of the
attempts ai relieving the entrapped fluid have
resulted in a loss of volumetric efficiency with-
out having accomplished the primary objective
of adequately relievin high trapping pressures.
If is, therefore, an object of this invention fo
oovide a gear pump which has ifs teeth formed
fo allow the escape of fluid confmed between
teeth which are in meshing relationship.
A îurther important object of the invention
resides in the provision of a gear pump, the
teeth of which have ffrooves in their faces ex-
tending frorn the addendum circle fo a point in
their faces where the line of action intersects
the tooth faces when two mating tooth surfaces
have their pitch lines substantially co-extensive
ai the pitch point.
A yet more important object of the invention
resides in the provision of a gear pump, the teeth
of which have cutout portions in the exterior
surfaces thereof fo provide escape means for
fluid conflned between teeth .in mesh.
A still further important object of the in-
vention resides in the provision of a gear pump
equipped with means for communicating the
space between teeth in mesh fo either the out-
let or the inlet ai II rimes.
Another important object of the invention
the provision of a ffear pump, the teeth of which
have their surfaces constituted fo provide an
escape for fluid between teeth in mesh.
The above and other objects and features of
the invention will be apparent from the follow-
ug description of the device taken in connection
with the accompanying drawings which form a
part oï this speciflction and in which:
Figure ! is a top plan view of one form of
ear purnp incorporating the invention;
Figure 2 is an isometric view of one of the
gears of the pump;
Fiure 3 is an enlarged view of the two gears
n meshing relationship with portions broken
away;
Figure 4 is an enlarged view of parts of two
ears utilizing a modified form of the invention;
Fure 5 is taken on the line -- in Figure 4
showing a view of one of the teeth; nd
Figure 6 is a view of the two gears of Figure 1
with portions removed, and showing the

2,60î,003
GEA PUMP
George W. Pontius, III, Sotth Bend, Ind.,
signor to Bendix Aviation Corporation, South
Bend, Ind., a corporation of Deaware
Application May î7, î96, Serial No. 670,452
10 Clams. (CI. î03--î26)

OFFICE

2
tionship of the teeth af their initial stage of
mesh.
leferring now to Figure î, reference numeral
 designates a pump housing or body having a
 cover  mounted thereon by screws . The
body is provided with an iniet 6 and an ourlet
. A driving gear  is rotatably disposed
within the body in meshing relationship fo a
gear . The latter gear is keyed fo a shaft
10  which is carried by the ody. The driving
gear ] is keyed fo a shaft  and constructed
and arranged fo rotate the gears. The interior
of th pump body or housing is formed at $ nd
$ to cooperate with the gears  and  for
] conveying fluid from the inlet $ to the ourlet
 where the fluid is put under pressure. The
driving gear  is considered to rotate in a clock-
wise direction as illustrated in Figure i by the
direction of the arrow.
20 The gears  and  a'e of the spur gear type
with teeth 3 and $ having tips  and 
 spectively, leferring now to Figures i and
these gears are comprised of an addendum circle
, a pitch circle , base circle , dedendum
2 circle , pitch line , pitch point $ and a line
of action . The tooth surfaces of the respec-
tive teeth are located between the addendum
and dedendum circles and are divided by the
pitch lines $ into tooth faces  and tooth
0 flanks .
Fluid is received af the inlet by the .gear teeth
and carried fo the ourlet in a manner familiar
fo those skilled in the art. To prevent the
trapment of fluid in pockets  and  formed
 between mshing teeth  and  the leading
faces of the teeth  ar slotted or channelled
ai S, and the trailing faces of teeth  are
channelled af  as best shown in Figures î fo
Backlash, designated at 3, is formed between
40 contiguous faces of the meshing gears and pro-
rides communication between the pockets  and
 which actually move as the gears rotate.
Backlash rnay be obtained in any suitable
manner familiar to those skilled in the art. I
.5 actual practice the slots or channels would be
ïormed in both faces of a gear tooth to permit
operation of the pump in ëither direction.  Sec
Figure .
These channels are disposed in the tooth faces
. so that when the teeth  and  move into con-
tact, the fluid confined in the space or pockets
 and  between the teeth is allowed to escape.
See Figure 6. I is obvious that if an escape of
some kind is not provided for this confined fluid
: thc gear teeth would tend to compress the sub-
stantially non-compressible fluid, such as off,
which in ail probabilities would result in pump
destruction. That is, at the rime of initial con-
tact between teeth  and 3 (sec Figure 6)
C0 poçke$  i smaller in volume than the pocket

2»601»003

3
58. As the driving gear 20 rotates the driven
gear 22 the pocket 55 increases in volume and
pocket 55 decreases in volume but the rate of
decrease in volume of the latter pocket is greater
than the rate of increase in volume of the former 5
pocket until a predeterntined position of rota-
tion of the teeth is reached, whereby there is
a tendency to put the confined or entrapped fluid
under pressure.
If these channels are not properly and accu- I0
rately located in the teeth faces mal-function of
the pump is inevitable. For optimum pump op-
eration it has been ïound that the channels 0
and 62 must be of a definite length. The length,
of course, varies with gear size and construction. 15
The wdth V of the channels should be such as to
allow a reasonable flow velocity of fluid from the
pockets. If shouid ibe noted that the width W of
the channels iS always less than the tooth width
.. in order to provide driving contact in all positions 20
of meshing teeth. When teeth 32 and 34 are in
con_tact at predetermined points A and B along
their surfaces th length of the channels 6 and
52 is eqtal to the distance from the points of
contact o said teeth to the addendum circle. The OE5
points A and B are located by the intersection of
the line of action with the points of tangency
between the driving and driven teeth of gears 20
and 2 respectively. That is, stating it another
way, the location of the channels is determined 30
as follows: When two mating tooth surfaces have
their pitch lines substantially coextensive af the
pitch point, tooth faces are channelled or other-
wise exteriorly relieved ïrom the addendum cir-
cles to points where the line of action intersects ,
the tooth Ïaces.
If should be noted that when the line of action
5 passes through points A and B as aïoremen-
tioned pockets 56 and 50 are substantially of the
saine volume. When contact between gea teeth 4o
3 and 34 was first ruade pocket  was larger
in volume than pocket 55. See Figure 6. In the
position shown in Figures 1 and 3 the pockets 0
and 5 have just closed to outiet by reason of the
contact between the tooth faces across the entire 5
teoth width to thereby close the passage or chan-
nel 6. Likewise, channel 6 is also closed at this
instant. A slight amount of rotation of gear 
wfll open the passage 0 to communicate the
pockets with the inlet. Continued rotation of the 50
driving gear, beyond where the line of action
passes through points A and B, wfll cause pocket
5 to decrease in volume but at a rate slower than
the increase in volume of pocket 56 to thereby
tend to create a low pressure or vacuum in the 5
pocket or chamber 56, which low pressure is con-
ducive to gear chatter. However, as aforemen-
ti0ned this condition is avoided by providing a
channel or passage 60 which communicates pock-
et 56 with the inlet 6 substantially simultane- 60
ously with the sealing of the chamber or pocket
55 from the ourlet  as best shown in Figures 1
and 3. To illustrate the criticalness of location
and size of these passages it will be well to point
out that if the channels are teo long there wfll 65
be leakage from the ourlet to the inlet whereby
the volumetric efliciency of the pump will be re-
duced and if too short high pressures will be de-
veloped within the pockets between the gears.
It should be emphasized that a gear pump in- 70
corporating the features of this invention has a
relatively higher eflciency.
Figure 4 is a modifled form of the invention
and is adapted to function in much the saine
manner as the preferred embodiment of Figures 75

4
1 to 3. Instead of the tooth faces being grooved
as hereinbefore described, the tooth flanks are
grooved at @ and 2 of teeth  and 5 respec-
tively. To permit use of the pump in either di-
rection of rotation both flanks of a tooth are
channelled. However, for clockwise rotation,
only channels 8 and 2 will be needed. For
counter-clockwise rotation channels  and 2
are used. When two mating teoth surfaces bave
their pitch lines substantially coextensive at the
pitch point tooth flanks are channelled from a
predetermined point below the base circles fo a
point in the tooth flanks where the line of action
intersects the tooth flanks to thereby provide an
escape for the entrapped fluid. The piteh line is
designated by the numeral 00 in Figure 5.
Although the invention has been described in
connection with certain speciflc embodiments the
principles are susceptible of numerous other ap-
plications that will readily occur to persons
skilled in the art. The invention is, therefore, fo
be llmited only as indicated by the scope of the
appended claims.
Having thus described the various ïeatures of
the invention, what I claire as new and desire fo
secure by Letters Patent is:
1. In a fluid pump or motor, a body having
inlet and outiet ports, a driving gear located in
the body, a driven gear, said driving and driven
gears having teeth in mesh with faces in con-
tact relationship and backlash therebetween, said
teeth in mesh forming pockets therebetween in
whlch fluid is entrapped, and a channel in the
leading tooth faces of each of the teeth of the
drlving gear ,and in the trailing tooth faces of
each of the teeth of the driven gear extending
along the tooth faces ïrom the addendum circles
of the gears fo a point in the tooth faces inter-
sected by the line of action at a rime when the
piteh lines of two mating gear teeth pass through
the piteh point.
2. The method of locating channe]s in the
tooth fa.ces of mating gears having back!ash
therebetween to provide a means of escape for
fluid entrapped between the teeth in mesh, the
steps of which comprise placing the gear teeth
in engaging relationship so that two mating
tooth surfaces bave their pitch lines substantialiy
coextensive ai the pitch point, and locating a
channel in the leading tootl] face of one oï the
gears and in the trailing tooth face of the other
gear so that said channel will extend along the
teoth faces from a point in the tooth faces wherc
the line of action intersects said tooth faces fo
the addendum circles of the respective gears.
3. In a fluid pump or motor, a body having an
inlet and an ourlet, driving and driven gears
disposed within the body with backlash there-
between, said gears havin teeth with surfaces
in contact when the gears are in meshing rela-
tionship, the teeth in mesh having pockets
formed therebetween in which fluid is entrapped,
and a channel in the flanks of the leading tooth
surfaces of each of the teeth of the dïiving gear
and in the flanks of the trailing tooth surfaces
of each of the teeth of the driven gear extend-
ing from a predetermined point below the base
circles of the gears to a point where the line of
action intersects the tooth flanks when the two
mating tooth surfaces have their pitch lines sub-
stantially coextensive at the pitch point.
4. A fluid pump or motor comprising a body
having inlet and outiet ports, a pair of gears
locaed in the body in meshing relationship and

»601»008

having backlash therebetween, said meshing
gears constructed and arranged fo form two
moving pockets between the teeth in mesh and
having variable volumes which entrap fluid, the
increase in volume of one of the pockets being
ata slower rate than the decrease in volume of
the other pocket, whereby the entrapped fluid in
said one pocket tends tobe subjected to a de-
creasing pressure and the entrapped fluid in said
other pocket tends tobe subjected to an increas-
ing pressure, and means providing an escape for
the entrapped fluid fïom the pockets comprising
a passage in the trafling tooth faces of the teeth
of one of said gears and in theqeading tooth
faces of the teeth of the other gent, said passage
extending from the addendum circles of said
gears to a point in the tooth faces of said gears
intersected by the line of action ata rime when
the pitch lines of two mating gear teeth pass
through the pitch point.
5. A fluid pump or motor comprising a body
having inlet and ourlet ports, a pair of gears
located in the body with the teeth of said gears
meshing in such a manner as fo provide backlash
therebetween, said meshing teeth .constructed
and arranged to form two moving pockets be-
tween the teeth in mesh having variable volumes
which entrap fluid, the increase in volume of
one of the pockets being ata slower rate than
the decrease in volume of the other pocket,
whereby the entrapped fluid in said one pocket
tends to be subjected fo a decreasing pressure
and the entrapped fluid in said other pocket
tends tobe subjected to an increasing pressure,
and means providing an escape for the entrapped
fluid from the pockets comprising a passage in
the leading tooth faces of each of the teeth of
one of the gears and in the trailing tooth faces
of each of the teeth of the other gear, said Pas-
sage extending from the addendum circles of the
gears to a point in the tooth fa.ces intersected by
the line of action at a rime when the pitch lines
of two mating gear teeth pass through the pitch
point, whereby said other pocket is communi-
cated to ourlet to expel the entrapped fluid there-
fo and said one pocket is communicated to inlet
to equalize the pressure therein after communi-
cation with the ourlet is cut off.
6. In a fluid pump or motor, a body having
inlet and ourlet ports, a pair of gears located in
the body in meshing relationship, said gears hav-
ing backlash, with the teeth in mesh forming
movinŒE pockets therebetween in which fluid is
œentrapped, and a relief in the trailing tooth
faces of one of the gears and in the leading tooth
faces of the other gear, said relief extending
from the addendum circles of said gears to a
point in the tooth face of said gears intersected
by the line of action af a rime when the pitch
lines of two mating gear teeth are substantially
coextensive at the piteh point.
7. In a fluid pump or motor, a body having
inlet and ourlet ports, driving and driven gears
in the body arranged in meshing relationship,
with the teeth in mesh forming pockets there-
between in which fiuid is entrapped, said gears
having backlash therebetween, and a channel in
the leading tooth faces of each of the teeth of
the driving gear and in the trafling tooth faces
of each of the teeth of the driven gear extending
along the tooth faces from the tooth tips of the
gears to a line in the teoth faces normal to and
intersecting the line of action ata rime when the
Pitch lines of two mating gear teeth pass through
the pitch point.

6
8. In a fluid pump or motor, a body having
inlet and out]et ports, driving .and driven gears
in the body arranged in meshing relationship,
with the teeth in mesh forming pockets there-
5 between in which fluid is entrapped, said gears
having backlash therebetween; and a channel in
the leading tooth faces of each of the teeth oî
one of the gears and in the trafling toth faces
of each of the teeth of the other gear extending
lO along the tooth faces from the tooth tips of the
gears fo a line in the ooth faces normal fo and
intersecting the line of action ata rime when
the pitch lines of two m.,ting gear teeth pass
tln'ough the pitch point.
15 9. In a fluid pump or moter, inlet and ourlet
ports, a pair of gears arranged in meshing rela-
tionship with the teeth in mesh forming two
pockets therebetween in whichfluid is entrapped,
said gears having backlash, and a charmel in the
20 leading tooth surfaces of each of. the teeth of
one of the gears and in the trailing tooth sur-
faces of each of the teeth of the other gear, each
of said channels of one of said gears having one
of its ends located in the surface ata predeter-
25 mined point so as to communicate one of the
pockets with one of the ports belote the pitch
lines of the two mating gear teeth forming the
pockets are coextensive and each of said chan-
nels of the other gear having one of its ends
30 located in the surface af a pïedetermined point
so as to communicate the other pocket with the
other port after said pitch lines are coextensive,
the other end of each of said .channels being
located in the surface ata point where the line
35 of action intersects the tooth surfaces when two
mating tooth surfaces have their pitch lines co-
extensive af the pitch point.
10. In a fluid pump or m0tor, driving and
driven gears arranged in meshing relationship
40 with the teeth in mesh forming pockets there-
between in which fluid is entrapped, said gears
having blacklash, and a channel in the flanks of
the leading tooth surfaces of each of the teeth
of one of the gears and in the flanks of the
45 trafling tooth surfaces of each of the teeth of
the other gear extending along the tooth flanks
from a predetermined location therein below the
base circles of the gears to a point where the line
of action intersects the tooth flanks when two
50 mating tooth surfaces bave their pitch lines sub-
stantialiy coextensive at the pitch point.
GEORGE W. PONTIUS, III.
55 REFERENCES CITED
The following references are of record in the
file of this patent:
UN1TED STATES PATENTS

6O

65

7O

7

Number
884,812
1,252,160
1,633,793
1,686,867
1,712,095
1,728,529
1,813,875
1,923,268
1,976,227
2,159,744
2,344,628

Number
439,908

Naine Date
Gfllmor et al ....... Apr. 14, 1908
Pagel .............. Jan. 1, 1918
Porst ............. June 28, 1927
Kuhn .............. Oct. 9, 1928
Schurr ............. May 7, 1929
Butler ............ Sept. 17, 1929
Fehr ............... July 7, 1931
Jensen ............ Aug. 22, 1933
Howard ............ Oct. 9, 1934
Maglott ............ M.ay 23, 1939
Monahan .......... Mat. 21, 1944
FOREIGN PATENTS
Country Date
Great Britain ...... Dec. 17, 1935