Патент USA US3048131код для вставки
Aug. 7, 1962 c. w. TYDEMAN 3,043,119 AIR-COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 5 Sheets-Sheet 1 /50 24» 26 +3 E6. /08'~ //0/ INVENTOR. .—- .._/4 CIA/125N635 M TYDEMA/v A 7' TO/PNE Y5 Aug. 7, 1962 c. w. TYDEMAN 3,043,119 AIR-COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 3 Sheets-Sheet 2 ~o~ 0%.. / 0Q / §Q4§ ¢ %6 /,4FlnAwlvlma../vm////‘k.... a ,0 / ‘Q Mll/ ,1 .. .. / _ 45 ms a“ / / ... w... 5,, Ma w Mm/ 3 2 4 ‘Wm/-HIM / ~ I, m ..___ / = _ ,Q‘ /8Q§ %o¢$=l_r/ ./ . . Q‘...1/ ,, / ?e. 5, INVEN TOR. CLARENCE M TYDEMA/V BY 14 TTO/PN E Y5 Aug. 7, 1962 , c. w. TYDEMAN 3,048,119 AIR~COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 3 Sheets-Sheet 3 /8 /58 ~/70 ‘/ /72 r v66” ‘M 25 T’ /68 ms >56 "1' 46 H6. 8. INVEN TOR. CLARENCE M TYDEM/IN BY A TTO/PNE Y5 United States Patent Office 3,048,! 19 Patented Aug. 7, 19622 2 1 It is, therefore, the principal object of the present in 3,048,119 AIR-COOKED PUMP ASSEMBLY FOR HYDRAU LIC FLUID AND THE LIKE 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. I ' 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 struction. 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, vention; s 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 and 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. “ - 5 3,048,119 . 4 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 76. 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 24. 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 FIGURE 1. I 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 oses. 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 ported. 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, 65 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 3,048,119 5 6 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 basis. 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. 65 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 ‘F 3 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 tween. 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 between. 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 cap. 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 awe-.t" 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.