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Патент USA US3048131

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Aug. 7, 1962
Filed June 2, 1961
5 Sheets-Sheet 1
CIA/125N635 M TYDEMA/v
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Aug. 7, 1962
Filed June 2, 1961
3 Sheets-Sheet 2
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Aug. 7, 1962
Filed June 2, 1961
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United States Patent Office
3,048,! 19
Patented Aug. 7, 19622
It is, therefore, the principal object of the present in
Clarence W. Tydeman, Timnath, Colo., assignor to Tyde
vention to provide a novel and improved air-cooled pump
for hydraulic ?uid and the like.
A second objective is the provision of a pump of the
class described which is operative to maintain the tem
perature of the ?uid nearly constant at about 20° F. above
ambient temperature over extended periods of operation.
Another object of the invention which for-ms the sub
11 Claims. (Cl. 103-118)
ject matter hereof is to provide a lightweight portable air
This invention relates to hydraulic pumps and, more 10 cooled gear pump assembly.
speci?cally, to air-cooled pumps of a type adapted to
Still another objective is to provide a pump housing
having an improved radiator design.
deliver hydraulic ?uid to an operating unit at a substan
An additional object of the invention herein disclosed is
tially constant temperature and pressure.
the provision of a circulating gear pump assembly that
In my copending application Serial Number 101,297
?led April 6, 1961, I disclose an improved hydraulically 15 includes a non-chattering check valve of unique con
operated tracer assembly for engine and turret lathes that
Further objects are to provide an invention of the
is capable of reproducing the contoured edge of a tem
class aforementioned which is relatively inexpensive,
plate on a workpiece to tolerances of plus or minus 0.000‘1
inch. In order for this high degree of accuracy to be
versatile, virtually trouble-free, compact, adaptable for
use in a wide variety of ?uidpumping applications and
attained, however, it is absolutely necessary that the hy
decorative in appearance.
draulic ?uid which forms the operative connection be
‘Other objects will be in'part apparent and in part
tween the stylus or feeler of the tracer unit and the tool
pointed out speci?cally hereinafter in connection with the
holding quill of the cutter unit be delivered thereto at a
description of the drawings that follows, and in which:
relatively high pressure and at a nearly constant ambient
FIGURE 1 is a diametrical section showing the air
temperature; otherwise, the degree of precision that the
cooled gear pump for‘hydraulic ?uids of the present in
assembly is capable of producing becomes impossible to
realize. In fact, this same thing is true of most, if not all,
FIGURE 2 is a fragmentary sectional detail taken along
high-precision hydraulically-operated machinery.
line 2-2 of FIGURE 1 illustrating the ?uid delivery
Now, it is well known that hydraulic ?uid can be
passage in the radiator together with the over?ow passage
pumped to an operatingunit at a nearly constant pres
back to the sump;
sure and relatively low uniform temperature by utilizing
‘FIGURE 3 is a fragmentary section taken along line
any one of a number of different types of refrigeration
3--3 of FIGURE 2 showing a different view of the over
units either directly associated with the pump or connected
?ow passage;
into the feed lines intermediate the pump and operating
:FIGURE 4 is a horizontal section through the radiator
unit. While this approach to the problem must be con- '
taken along line 4-4 of FIGURE 1;
'sidered effective to produce the desired end result, namely,
FIGURE 5 is a vertical section through the radiator
holding the temperature of the ?uid nearly constant, it
taken along line 5-5 of FIGURE 4;
has a number of serious drawbacks that make it more or
I FIGURE 6 is a top plan view showing the ring that
less impractical. For example, the size and weight of
the refrigeration unit required to handle the ?ow of ?uid 40 supports the cap or cover for the fan and radiator;
of FIGURE 1 showing the gear pump slightly enlarged;
results in apparatus that cannot be considered portable in
man Machine Works, Inc., Redwood City, Calif., a cor
poration of California
Filed June 2, 1961, Ser. No. 114,386
the common sense of the term.
In addition to the prob
FIGURE 8 is a fragmentary sectional detail to an en
lem of bulk, the operating costs are likelyto be rather
larged scale illustrating the pressure regulator assembly,
high to say nothing of the substantial increase in initial
expense. As a result, most machine shops prefer some 45 portions of the valve element having been broken away
type of air-cooled pump even though to use one of the
prior art designs often means sacri?cing a signi?cant
to expose the interior construction.
Referring now to the drawings for a detailed descrip
amount of the accuracy the hydraulically-operated ma
tion of the air-cooled pump of the present invention which
chine tool connected thereto is capable of producing.
The need for some type of cooling apparatus becomes
has been designated broadly by numeral ‘10, and partic
ularly to FIGURE 1 for this purpose, it will be seen to
include a sump or ?uid reservoir 12 that provides a base
on top of which rests a coverplate 14 supporting a gear
pump 16 on the underside thereof, a radiator 18 providing
at a rate of less than a gallon per minute and a pressure
a housing for motor 20 that operates both the gear pump
of about 500 p.s.i. will result in the ?uid coming to a boil
within the period of approximately one-half hour. This, 55 16 and fan 22, and a cap or cover 24 attached to the top
of the radiator by means of supporting ring 26'. ‘Fluid
of course, is an intolerable situation and means must be
reservoir ‘12 has an open-topped hollow cylindrical con
provided for holding the oil temperature down to a Work
readily apparent when it is realized that a gear pump
operated by a one-half horsepower motor to deliver ?uid
?guration, the wall portion 28 of which is provided with a
able level.
fill opening 30, an opening 32 for exhaust line 34, and an
The prior art attempts to design an air-cooledhydraulic
pump effective to maintain a ?uid pressure of the order 60 opening receiving tube 36 by which ?uid from the sump
or reservoir is delivered to thermometer 38. An elbow
of 500 p.s.i. at a temperature not to exceed approximately
?tting 40 is attached within the ?ll opening 30 and pro
125° F. have met with little success in terms of a com
rvided with a plug 42 which keeps dust and dirt out of the
pact, portable and inexpensive unit. Some of them, while
?uid which might otherwise cause faulty operation of the
effective to hold the temperature of the ?uid to a useable
maximum, permit variations over a rather wide range 65 hydraulically-controlled mechanism receiving ?uid from
the pump. The plug is, of course, only removed when the
somewhat dependent upon whether the machine tool is
?uid is changed or replenished.
being operated or the ?uid is merely circulated by-passing
The upper edge of the wall portion 28 of the reservoir
the operating unit. Although the maximum temperature
12 is, in the particular form shown, provided with an
is not a critical factor in such a vunit, the fluctuations
70 integrally-formed inturned ?ange 44 to which is bolted
therein are, giving rise to- erratic and unpredictable oper
or otherwise attached a coverplate 14 that carries the
ation of the machine tool.
gear pump 16 suspended from the underside thereof as
the hollow cylindrical wall portion 92 with the bottom
well as providing structure containing the lower portions
of the ?uid delivery passage 46 and over?ow passage
provided for purposes of dissipating the heat generated
4-8. The reservoir is ?lled with hydraulic ?uid to a level
by the motor.
which at least submerges the lower end of pump intake
passage 56.
‘Coverplate 14 comprises a circular disk having a cup
shaped cavity 52 in the center thereof that contains a
centrally-located opening 54 in its bottom portion 56
of motor shaft 76 directs air down through openings 137
in supporting ring 26 and over the motor thus forcefully
exhausting the heat generated by the motor from the
78 of the radiator 18, a series of exhaust ports 166 are
Fan blade 22 mounted on the upper end
radiator through openings 166.
An annular cooling chamber 168 surrounds the hol
adapted to pass the shaft 58 by means of which the pump 10 low cylindrical wall portion 92 of the radiator de?ned
16 is driven.
The edge of the disk-shaped coverplate
is bolted to the inturned ?ange 44 of the reservoir form
ing a ?uid-tight seal therewith. The radiator 18 is, in
turn, bolted to the coverplate and centered with respect
thereto by means of interlocking circular rib‘ portions 60
and 62. integrally-formed boss 64 adjoining the cup
shaped cavity of the coverplate on the outside thereof
contains both ?uid delivery passage 46 and over?ow
passage 43, the precise location and arrangement of
which will be set forth in greater detail presently in
by radial ?ange 110, downwardly and outwardly sloped
?ange 112, and connecting wall portion 114 that joins
the free edges of these ?anges which are cast integrally
with wall portion 92 that provides the fourth wall of
the chamber. As shown, the ?uid cooling chamber is
generally trapezoidal in vertical section with the inclined
?ange 11?. positioned directly in the path of the air cir
culated downwardly from the periphery of the fan 22
through openings 116 in the support ring 26 and into the
convergent air space left between the exterior surface of
the radiator and the interior surface of the annular skirt
connection with the description of FIGURES 2 and 3.
118 of cap 24. Air ?owing over inclined ?ange 112 and
Now, in connection with FIGURES 1 and 7, it can
connecting wall portion 114 of the radiator provides for
be seen that pump 16 is of the common gear-type having
primary cooling of the ?uid being circulated within
an intake passage 56 opening onto the underside thereof
which is enclosed by a ?ltering screen 66. The fluid 25 chamber 108 as it carries away the heat through the
annular gap 120 left between the adjacent surfaces of
taken into the intake passage is delivered to the meshed
the radiator and cap or cover ‘24. Some secondary cool
gear elements 68 and 70‘ that are journalled for rotation
ing is achieved from the air forced by the fan past the
within ?gure-eightshaped cavity 72. One of the gear
motor along hollow cylindrical wall portion 92 and out
elements 70 is mounted on a stub shaft 74 for rotation
therewith while the other gear element 68 is mounted 30 past radial ?ange 110 although this l?ow is primarily
for the purpose of carrying 01f the heat of the motor
on shaft 58 that is connected to the motor shaft 76.
before it can heat up the ?uid in the adjacent cooling
The entire pump unit 16 is, therefore, eccentrically lo
chamber appreciably.
cated on the underside of the bottom portion 56 of the
cup-shaped cavity 52 in coverplate 14 to place shaft 58
in axial alignment with the centrally-located motor shaft
Rotation of the gear elements 68 and 70 within cavity
72 in the direction of the arrow in FIGURE 7 picks up
?uid from the intake passage and delivers same to delivery
passage 46 provided in the integrally-formed boss 64
carried by the coverplate 14 under pressure. The particu
lar manner in which delivery passage 46 is constructed
An integrally-formed boss 122 projects into cooling
chamber 108 and contains the delivery passage 46, over
?ow passage 48, branch passage 124 that leads to the hy
draulically-operated machine tool or the like controlled
by the pump mechanism, pressure-responsive valve as
sembly 126 along with the cavity 123 therefor, and passage
1% connecting the latter cavity into the cooling chamber
of the radiator. A detailed description of these passages,
their location and function will again be de?ned pending
completion of the radiator, supporting ring 26 and cover
by drilling intersecting radial and vertical passages from
the exterior surfaces of the coverpiate, pump housing
From FIGURES 4 and 5 it is apparent that radiator 18
and radiator and, thereafter, plugging the surface open 45
is preferably cast as a unitary structure from some metal,
ings, is well known in the art forming no part of the
such as aluminum, which provides a good coef?cient of
present invention; therefore, it will not be described in
thermal conductivity as well as being relatively lightweight
detail although readily apparent from an examination of
The construction of the radiator 18 can best be seen
in connectionlwith FIGURES 1, 4 and 5 to which refer
ence will be made. As aforementioned, interlocking an
nular ribs 69 and 62 on the bottom 78 of the radiator
and top of coverplate 14 center these elements with re
spect to one another while fasteners 80 maintain the
assembled relation therebetween. The bottom 78 of the
yet strong. In a cast element such as radiator 18 contain
ing an internal annular cooling chamber such as that
numbered 108 within which the fluid circulates, it is, of
course, necessary to provide a plurality of core holes 132
opening into the chamber from which the mold can be
removed. As illustrated, three of these core holes are
plugged with soft plugs 134 while the fourth contains
a removable threaded plug 136 providing continued access
to the cooling chamber for inspection and cleaning pur
radiator includes a centrally-located opening 82 through
which the motor shaft 76 passes into the cup-shaped
FIGURES 1 and 6 show most clearly the construction
cavity 52 in the coverplate where it is attached to shaft
58 of the pump by means of shaft coupling 84. An up 60 of supporting ring 26 which comprises a centrally-located
hub-forming portion 137 that houses the bearing 13% in
standing annular rib 86 surrounds central opening 82
which the motor shaft 76 is journalled, a plurality of
and is provided with an ‘annular shoulder 88 projecting
inwardly therefrom on which shaft bearing 90 is sup
A hollow cylindrical wall portion 92; extends upwardly
from the bottom 78 of the radiator de?ning a housing
for electric motor 26 that is encased therein. In the
particular form shown, the stationary ?eld poles 94 of
the motor that carry the ?eld winding or coil 96 are
supported on the shoulder 98 de?ned by an inwardly
extending annular rib 1W placed on the inside surface
of hollow cylindrical Wall portion 92. The motor shaft
76 is provided with a shoulder 102 that rests on the
spoke-like portions 140 extending radially outward from
the hub-forming portion in angularly spaced relation to
their point of attachment with outer ring portion 142,
and an integrally-formed inner ring portion 144 inter
connecting the spoke-like portions intermediate the hub
portion and the outer ring portion. The interstices be
tween the hub, spokes and ring portions de?ne the open
ings 116 and 107 of the supporting ring, the location and
function of which have already been described.
Inner ring portion .144 overlies the upper edge of the
hollow cylindrical Wall portion 92 of the radiator and is
attached thereto by suitable fasteners as indicated. The
inner race of thrust bearing 90 supporting the armature
1% for rotation Within the ?eld coil. At the juncture of 75 outer ring portion 142, on the other hand, engages the
underside of shoulder 146 provided on the inner surface
of the skirt .118 of cover 24.
Cover or cap 24'can only be seen in FIGURE 1 where
it will be noted to have an open top covered by screen
148 which protects the fan 22 yet provides an air intake
opening. The annular skirt 118 supports the screen in
that of the bypass circuit and usually on an intermittent
Finally with reference to FIGURES l and 8 the novel
and improved pressure-responsive valve assembly 126
especially suited for use in the instant air-cooled pump
unit will be described. Valve cavity 128 opens onto the
spaced relation above supporting ring 26 thus de?ning a
exterior of boss 122 of the radiator and, as shown, extends
inward essentially radially to intersect both passage 130
and delivery passage ‘46. The inner extremity of cavity
tends downwardly below ring 26 in spaced relation outside
radiator 18 and directs the air from the fan along the 10 128 is tapered at its point of connection with delivery
passage 46 to provide a frusto-conical seat 156 located up
inclined ?ange 112 of the latter to carry away the heat
stream of the intake end of passage 130. A truncated right
conducted therethrough from the ?uid. An opening 152 is
conical valve element v158 mates with seat 156 providing a
provided in the skirt of the cover adjacent the pressure
?uid-tight seal therewith when biased into closed position
responsive Valve assembly 126 enabling the latter to be
by compression spring 160 located in cavity 128 between
removed and serviced.
said valve element and plug 162. The intermediate por
Having described in detail the several components of the
tion of cavity 128 is preferably threaded internally as
air-cooled pump assembly with the exception of pressure
indicated to receive the threaded section 164 of the plug.
regulator assembly 126 shown in FIGURE 8, reference
The outer extremity of the valve cavity is smooth-bored
will now be made to FIGURES 1, 2 and 3 for an explana
to form a ?uid-tight seal with O-ring 166 provided in annu
tion of the ?uid-circulating and cooling systems. Ordi
cavity 150 in which the fan operates. The skirt 118 ex
narily, the hydraulically-operated servo-system operating
lar groove 168 at outer end of plug 162. Threaded ad
a machine tool or the like that is connected to the pump
justment of the plug in the valve cavity varies the pre
l-oad compression on spring 160 thus regulating the ?uid
assembly of the present invention will operate only inter
mittently and require ‘a good deal less than the full
volumetric output the pump is capable of delivering.
Thus, an ef?cient by-pass system is absolutely necessary
which will keep the ?uid circulating while being cooled to
maintain a relatively constant temperature. In this con
nection it should be noted that the ?uid heats up the most
when being circulated in the by-pass system rather than
when it is being delivered to the servo-system in the operat
pressure required to unseat valve element 156.
Valve element 156 is constructed to provide a transverse
passage 178 opening onto the conical surface at diametri
cally opposed points and a longitudinal passage 1'72 inter
connecting the transverse passage 170 with delivery pas
sage 46. When seated as shown in FIGURES 1 and 8, the
outlets of the transverse passage 170 are, of course, closed
_ against the frusto-conical surface of the valve seat thus
?uid passes the pressure-responsive valve assembly in'the
by-pass circuit. Also, it is mandatory that the ?uid in the
preventing the movement of ?uid into passage 130. When,
however, the fluid-pressure in delivery passage 46 exceeds
the opposing force applied by spring 160, the valve element
bypass system be maintained at a pressure at least equal
will move off its seat allowing ?uid to pass from the
to, and preferably considerably greater, than the maximum
operating pressure of the operating circuit; otherwise, the
delivery passage 46 into passage 130.
' ing circuit, the greatest temperature rise occurring as the
?uid would be by-passed continually and never be avail- _
If passages 170 and 172 were eliminated from the valve
element 158 it would function much in the same manner as
a ball check valve used as a pressure-responsive system;
able for use in the higher pressure operating circuit.
Accordingly,. the function of the pump is to maintain an 40 however, experience with the use of ball check valves in
such a high pressure ?uid system has shown them to be
excess of high pressure ?uid available at a relatively con
unsatisfactory from the standpoint that they develop a
stant temperature at all times to satisfy the operatin
requirements of the servo-system.
chatter at certain critical ?uid pressures which produce I
erratic operation due to ?uctuations in the line pressure
Now, the ?uid issuing from the pump under pressure
leading to the servo-mechanism. The instant valve mecha
passes in delivery passage 46 through boss 64 in the cover
nism, on the other hand eliminates this chattering problem
plate 14 for the reservoir up into boss 122 located inside
through the use of passages 17¢’) and 172. The truncated
the annular cooling chamber 108 in the radiator 18 where
conical valve element is, of course, required to» maintain
it opens the pressure-responsive valve assembly 126 and
longitudinal passage 17.2 aligned with the discharge end of
drops down through passage 130 into said annular cham
delivery passage 46 which would not be possible with a
ber. As the ?uid enters the cooling chamber and circu
spherical valve element.
lates therearound it is cooled by the air circulated by fan
Having thus described the several useful and novel fea
22 passing over the walls bordering said chamber which
tures of the air-cooled pump assembly of the present in
conduct the heat away to the atmosphere. When the ?uid
vention it will be apparent that the many worthwhile ob
level in chamber 108 reaches the top of over?ow passage
48 (FIGURES 2 and 3) it drops back down through the 55 jectives ‘for which it was designed have been achieved.
Although but a single speci?c embodiment of the inven
radiator into the reservoir.
tion has been illustrated and described in the accompany
The effectiveness of the pump assembly can best be
ing drawings, I realize that certain changes and modi?ca
appreciated from the fact that when equipped with a pump
tions therein may well occur to those skilled in the art
delivering slightly less than a gallon per minute and the
pressure regulator adjusted to maintain the ?uid pressure 60 within the broad teaching hereof; hence, it is may inten
tion that the scope of protection afforded hereby shall be
at about 500 p.s.i., the temperature of the ?uid remained
limited only insofar as said limitations are expressly set
relatively constant at approximately 20° above ambient
forth in the appended claims.
temperature even though all of the ?uid was by-passed
What is claimed is: '
continuously for a period of eight hours, the normal work
1. An air-cooled pump for hydraulic ?uid and the like
ing day.
which comprises: an open~topped reservoir having an
The operating circuit of the pump assembly comprises
opening in a wall portion thereof adapted for connection
merely branch passage 124 located in the boss 122 of the
to an exhaust line returning ?uid thereto from an operat
' radiator which opens into delivery passage 46 upstream
ing unit; a coverplate secured to the open top of the res
of pressure-responsive valve assembly 126 and return line
34 discharging into the reservoir. The outlet of this' 70 ervoir in ?uid—tight sealed relation, said coverplate in
cluding a ?uid delivery passage and an over?ow passage;
branch passage 124 is, of course, connected to the line 154
a pump supported on the underside of the coverplate
connected to the hydraulically-operated servo-mechanism,
within the reservoir in position to draw ?uid therefrom
whereas, line 34 receives ?uid discharged therefrom and
and deliver same under pressure to the delivery passage;
return it to the reservoir. The entire operating circuit
above-described functions at a pressure substantially below 75 a radiator mounted atop the coverplate in fluid-tight
aolae, 1 19
sealed relation thereto and including a centrally-located
open-topped hollow cylindrical wall portion de?ning a
portion spaced above the radial ?ange and a second hol
low cylindrical wall portion spaced outwardly of the ?rst
hollow cylindrical wall portion interconnecting the radial
motor ‘housing, a continuous annular cooling chamber
surrounding the motor housing, a boss located within the
,annular cooling chamber, said boss containing a valve
socket connected to receive ?uid from the delivery passage
in the coverplate, a branch outlet passage connected to
receive ?uid from the delivery passage upstream of the
valve socket for delivery to the operating unit, and a pas
sage interconnecting the annular cooling chamber with 10
the valve socket downstream of the latter’s connection
into the delivery passage, and exhaust ports in the base of
the motor housing; a motor mounted in the hollow cylin—
drical wall portion of the radiator and operatively con~
nected to the pump through the coverplate; a fan opera
tively connected to the motor for rotation above the ra
diator in a direction to circulate air downwardly across
both the inside and outside walls of the annular cooling
chamber to cool the ?uid contained therein, said fan also
directing air over the motor and out the exhaust ports in ~
the motor housing; support-forming means attached to the
top of the radiator underneath the fan journalling the mo
tor shaft; a cap attached to the support~forming means in
position to cover the fan, said cap having an open top
adapted to admit air to the fan and an annular skirt en~
circling the radiator in spaced relation to the annular
cooling chamber therein; and, pressure-responsive valve
means located in the valve socket between the outlet of
the delivery passage and the inlet of the passage connect
ing said valve socket into the annular cooling chamber of
the radiator, said valve means being operative to open at
a predetermined pressure in excess of that required to
actuate the operating unit connected to receive ?uid from
the branch passage and deliver same to the annular cool
ing chamber where it is cooled before entering the over
?ow passage for return to the reservoir, and said valve
means being operative to close shutting off the supply of
?uid to the cooling chamber when the operating unit is
receiving ?uid from the pump through the branch passage.
2. The air-cooled pump as set forth in claim 1 in which
the valve socket terminates at its inner end where it opens
into the ‘delivery passage in a frusto-conical valve seat lo~
cated ahead of the intake end of the passage intercon
necting said valve socket with the cooling chamber, and
- in which the pressure-responsive valve means comprises '
a truncated conical valve elements shaped to ?t the trusts
a generally trapezoidal vertical cross section.
4. The air-cooled pump as set forth in claim 1 in which
passage interconnecting the valve socket. with the cooling
chamber is located to provide a gravity drain therebe
5. The air-cooled pump as set forth in claim 1 in which
the inlet end of the over?ow passage in the cooling cham
ber is located to maintain the latter chamber substantially
full of ?uid.
6. The air-cooled pump as set. forth in claim 1 in which
the adjacent surfaces of the skirt and cooling chamber
converge toward the exhaust opening de?ned there
7. The air-cooled pump as set forth in claim 1 in which
the support-forming means comprises a centrally-located
hub portion journalling the motor shaft, a plurality of
spokes radiating from the hub portion, an intermediate
ring portion interconnecting the spokes and cooperating
'therewith and with the hub portion to de?ne openings
positioned to admit air circulated by the ‘fan to the interior
of the motor housing, said intermediate ring portion being
attached to the hollow cylindrical wall portion of the ra
diator, and an outer ring portion interconnecting the en
tremities of the spokes to de?ne therewith and, with the
intermediate ring portion a plurality of openings posi
tioned to deliver air circulated by the fan into the space
de?ned between the annular skirt of the cap and the
cooling chamber of the radiator, said outer ring portion
being attached to said skirt forming the support for the
8. The air-‘cooled pumped as set forth in claim 2 in
which the plug is adjustable within the valve cavity in a
direction to vary the spring bias on the valve element
for purposes of regulating the ?uid pressure required to
by-pa'ss ?uid into the cooling chamber.
9. The air-cooled pump as set forth in claim 2 in which
the valve element includes a transverse passage opening
onto the conical surface thereof at at least one point
and a longitudinal passage interconnecting the transverse
passage with the truncated end of said valve element in
‘position to receive ?uid from the delivery passage in both
open and closed positions.
conical seat forming a ?uid-tight seal therewith, a plug
v1O. The air-cooled pump as set forth in claim 9 in
closing the outer end of the valve socket, and a compres—
which the plug is adjustable within the valve cavity in a
direction to vary the spring bias on the valve element for
purposes of regulating the ?uid pressure required to by
pass ?uid into the cooling chamber.
sion spring connected between the plug and valve element
biasing the latter into closed position.
3. The air-cooled pump as set forth in claim 1 in which
and inclined ?anges to form a ?uid-tight chamber having
the cooling chamber is de?ned by the hollow cylindrical
wall portion of the radiator, a substantially radial ?ange
encircling said hollow cylindrical wall portion on the out
side thereof above the exhaust ports, a downwardly and '
outwardly ?ared ?ange encircling the cylindrical wall
11. The air-cooled pump as set forth in claim 9 in which
the transverse passage opens onto the conical surface of
the valve element at two substantially diametrically
spaced points.
No references cited.
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