US2540714A - Pump - Google Patents

Description

1951 R. R. CURTIS ET AL 2,540,714

PUMP

Filed Jan. 22, 1945 3 Sheets-Sheet l O 2 A D29 6 ZNVENZ U5 EBgssaZ guf'zz's a Zmm Feb. 6, 1951 R. R. CURTIS ET AL 2,540,714

PUMP

Filed Jan. 22, 1945 5 Sheets-Sheet 2 ZNME Z U 55 Eusse Z Z 23. Curifzs FwzZd J [522mm Feb. 6, 1951 R. R. CURTIS ETAL 2,540,714

PUMP

Filed Jan. 22, 1945 5 Sheets-Sheet 3 BusseZZ E. Cur-252's EwaZd r]: Zamm Patented Feb. 6, 1951 PUMP Russell R. Curtis and Ewald J. Kimm, Dayton,

Ohio, assignors, by mesne assignments, to Thompson Products, Inc., Clevcland,v Ohio, a

corporation of Ohio Application January 22, 1945, Serial No. 573,827

1 Claim.

This invention relates to a pump, and more particularly to high pressure air compressor adapted to be installed, for instance, in garages, service stations and the like for providing a source of compressed air.

The air compressor assembly of our present invention includes a rotary pump of the radially extensible, multi-vane type. To facilitate the manufacture of the pump rotor, the hub" portion of the rotor is provided with radially extending slots the full length thereof, instead of beingprovided with slots terminating short of the ends of the rotor h-ub, as previously. This novel feature permits the slots to be milled out more easily since the milling cutter can travel the full length of the hub portion of the rotor in each pass. End plates secured to the stub shafts of the rotor are provided on either side of the hub for sliding clearance with the lateral edges of the vanes. This makes for a simpler construction than heretofore, I

Another feature of the rotor construction is the provision of slots or grooves in at least one face of the vane for substantially the full length thereof, whereby the pressures at the bottom of the slots beneath the bases of the vanes tend to be equalized with the higher of the pneumatic pressures adjacent the working. faces of the vanes. In this way pneumatic radial thrust on the vanes is approximately balanced. We have also found that by making the vanes of carbon, thei low mass minimizes wear on'the bore.

Another feature of our pump assembly is the provision of a lubricating system for the introduction of a lubricant into the pump bore at a point of relatively low pressure therein. The lubricating system includes a line from the discharge port of the pump for the compressed air and entrained lubricant, a lubricant separator in Y the discharge line, a line for carrying off the separated lubricant from the separator to a cooling device for lowering the temperature of the separated oil and a connectionfrom the cooling device to a metering valve assembly.

The metering valve assembly includes a metering needle controlling a passage for the lubricant back into the interior of the pump, and resilient means for holding the valve closed for all pressures below a predetermined pressure, such as, for instance, 75 lbs./sq. in. Tubing from the discharge side of :the pump establishes communication with the interior of the metering valve assembly on the other side of a Sylphon that seals off the main interior of the metering valve assembly. The arrangement is such that fluid pressure on the sylphon serves to open the metering vanes to roughly equalize the pneumatic radialneedle when the pressure is greater than that for which the valve is set. For all lower pressures, the resilient means referredto serves-to cause the metering valve to close. Thus, this valve is shut b fore the compressor chamber pressure drops down to atmospheric pressure, thereby preventing flooding of the compressor chamber when the compressor shuts off.

In order to prevent the setting up of a back pressure when the compressor is not operating, a check valve is positioned in the discharge line between the pump and the oil separato and the point of connection for the tubing back to the metering valve assembly is ahead of the check valve. Consequently, when the compressor shuts oil, pressure drops at the discharge side of the pump, the Sylphon expands to its normal position and the resilient means previously referred to act to close the metering valve pin. Thus, lubricant is admitted into' the bore of the pump only when the pump is operated and then only when the discharge pressure is above a predetermined level.

It is therefore an important object of this invention to provide a-pump assembly of novel and improved construction embodying features that enable it to be manufactured at relatively low cost and that materially increase its operating efiiciency.

.It is a further important object of this invention to provide a high pressure air compressor of the radially extensible, multi-vane type in which the slots for the vanes extend the full length of therotor hub and end plates secured to the rotor shaft serve to confine thelateral edges of the vanes while providing a sliding clearance therebetween.

1It-is a further important object of this invention to provide an air compressor, pump or the like, having a lubricating systemof improved efficiency that operates automatically during operation of the compressor to inject lubricant into tion to provide a rotary pum'pof thevane type in which the'vanes are formed of carbon, or other suitable materialof relatively low density, to minimize wear on the bore, and in which slots are provided in one of the faces of each of the thrust onthe vanes by introducinginto the space at the baseof each of the vanes the higher of the pneumaticpressuresadjacent the outer vane'surfaces in the pumping chamber.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings.

On the drawings:

Figure 1 is a top plan view of an installation of an air compressor embodying the principles of our invention.

Figure 2 is a broken front elevational view of the same.

Figure 3 is an enlarged sectional view. taken substantially along the line III-III of Figure 1, with parts in elevation.

Figure 4 is a fragmentary side elevational view looking toward the pumping end of the apparatus.

Figure 5 is a fragmentary sectional View taken substantially along the line VV of Figure 3.

Figure 6 is a plan view of a pump vane. or blade.

Figure '7 is an end View of the vane of Figure 6.

As shown on the drawings:

The reference numeral indicates generally an air compressor of our invention mounted upon a receiver 1 i by means'of supporting brackets 44. Said air compressor includes a motor l2, to one end of which is fastened a rotary compressor [3. The rotary compressor i3 is secured to the motor housing by means of bolts l4.

The rotary compressor is driven from the motor I2 through the motor shaft I (Fig. 3) supported at its extending end in a bearing race I6 mounted in the motor housing. Said shaft 15 extends through a seal I! that is attachedby means of screws It to an apertured plate [9. The seal H is of the rubber diaphragm type, the details of which need not be specifically described here as suitable seal constructions of this type are well known. The driving end of the motor shaft 15 engages the tongued end 20 of driven member 21 that also serves as an end plate for the rotor vanes. A cylindrical housing 22 encloses the driving connection and provides an annular shoulder for a bearing race 23.

Said end plate 2! is secured to the inner end 24 of a rotor stub shaft by means of a pin 25 that extends transversely through these two members. Said end plate 2| thus rotates with the rotor shaft in the bearing race 23. The other rotor stub shaft 25 carries a similar end plate 2'! secured to said stub shaft by means of end of the rotor and balance any end thrust, a

connection is provided between the chambers at opposite ends of the rotor 33. This is accomplished by providing-a threaded hole III in the end cap 30 (Fig. 3) and a threaded hole 2 extending through the wall of the housing 22, and by connecting the two holes by tubing I [3. Since the housing assembly for the rotor is substantially fluid tight, the tubing l [3 effects an equalization of fluid pressures on opposite ends of the.

rotor and thus effects a balance of any endv thrust. The bore 32 (Figs. 3 and 5)' is eccentric with respect to the axis of the rotor. The contour of the bore may suitably be built up of Archimedes.

and parabolic types of spirals joined together to provide compression and extension zones. The compression zone, indicated at C may have twice 4 the angular length of the extension zone, indicated at E, allowing for very gradual compression. It will be understood, of course, that these proportions may be changed at will. The combination of spirals employed permits the total angular displacement to be divided in any way desired. In addition, the maximum extension is relativelyrsmall in proportion to the diameter of bore or rotor, and the consequent gradual angularity of the Archimedes spirals and the low acceleration of the parabolic'spirals cause smooth, small-vibration action.

The rotor 33 is provided with radially extending slots 34 that extend the full length of the rotor. By reason of this construction, the slots 34 can be more readily milled out than would be the case if the slots terminated short of the ends of the rotor. As shown, there are twelve such radially extending slots, but ther may be more or fewer than that number. A vane 35 is mounted in each of the slots 34. As shown in Figures 6 and '7, each of the vanes 35 is rectangular in shape and is provided along one of its broad faces with a slot or recess 36 that extends substantially the full height of the vane. The purpose of the slot 35 is to permit the pressure in the radially extending slot 34 at the ,base of each vane .to be roughly equalized with the higher of pneumatic pressures at the two sides of the outer free ends of the vanes, and thus roughly balance pneumatic radial thrust on the vanes. The vanes themselves are preferably made of carbon or other relatively low density material so as to minimize bore wear. A relatively large number of vanes is used so that there is no great difference in pneumatic pressure on either side of each vane.

The pump housing Si is provided with an intake port 31 opening into the extension zone E, and a discharge port 38. The intake port 31 is connected by a nipple 39 to an air filter 40. A nipple 4| threaded into the discharge port 38 is connected through a T 42 to piping 43.

As best shown in Figures 1, 2 and 4, the piping 43 is connected to an oil separator 45, which may be of any suitable construction for the separation of the lubricant from the compressed air. A check valve 46 is inserted in the piping 43 ahead of the oil separator 45, the purpose of the check valve being to prevent backpressure from the tank ll passing into the compressor when the latter isnot operating.

From the oil separator 45 piping 41 leads to a cooler, indicated generally by the'reference numeral 4B. Said cooler 4'8 includes a number of horizontally disposed coils of piping 49 supported by means of vertical plates 50. A fan 5| is mounted upon the rear extended end 52 of the motor shaft to provide air circulation through and over thecoils 49 to aid in cooling the oil passing therethrough. A pipe 53 leading from the top of the oil separator 45 serves to conduct the compressed air from said separator into the top of the tank I I.

The cooled oil from the cooler 48 is led through a pipe 54 to an oil metering valve assembly indicated generally by the reference numeral 55. Said oil metering valve assembly 55 is mounted directly on top of the bore casing 3!. ing 3| is provided with a small diameter passage 55 (Fig. 3) extending into the pumping chamber. Above the small passage 56 the bore housing is counterbored and threaded to receive the lower threaded end 51 of the member ll forming part of said metering valve assembly.

Said casends'of a plurality of levers 64'.

Said :lower end ii! is aprovidedpwith an .axial pasisage 58 of smalldiameter and adaptedito b'econ trolled by means ota metering needle 5.9. Said metering needle is fixed in .the lowerend of a stem as that is slidable in "the vertical bore Bl provided for the purpose. Said stem 59 has a longitudinally extending slot 62 for permitting the passage of the lubricant therealong into the space beneath said stem 60.

The upper end of thestem Gil is provided with an annular groove 63 into which lit the inner An inverted cupshaped cap 65 is positioned above said stem 69 with its lower open end spacedfrom the annular wall .55 that surrounds saidstem soas to permit the flow of lubricant into the well 6'! provided by said annular wall 66. "The cap65 isalso provided with openings 109. A light spring 68 is placed within said inverted cup-like cap 65 to rest upon the upper end of said stem 60. The outer ends of the levers 64 extend through slots provided for the purpose inthe'lower end of the cap 55, so that when the cap moves downwardly, the levers are rocked to'lift the stem 60. v

The housing 69 of said metering valve assembly 55 is cylindrical in shape and provided with a lower reduced end it! that is internally threaded for threading upon the'passagecl mem-- ber H. Said housing fis'has a threaded opening 12 for receiving theend of the piping 54 which conducts the lubricant to the interior of said housing. Said housing is :provided with an integral transversely extending wall l3 that di vides the interior of the-housing into an upper 'chamber 14 and an intermediate chamber iii.

An'integrally formed second wall portion has an aperture T! in which-is positioned a sleeve 75E providing a passageway from said chamber l5 to a lower chamber 19.

The'wall 13 is provided with an upstanding, internally threaded annular portion -8ll into which is threaded the lower end of a guide member 3|. The guide membertl is provided with an axially extending bore through which extends arod 82 that rests at-itslower'end'upon the cap 65. An adjusting'nut .83 is threaded upon theupper reduced and :84 of said guide member 8|. The u-pperend of-thecasing 69 is closed'by a Sylphon-8 5,-the lower flanged end of which is secured to-said upper end of the housing by screws 89. Sylphon 85 and issecured at itsupper end in a disc8l that is fitted inside the upper'end of the Sylphon. A coiled spring 88 surrounds the upper end of the plunger 82 and is vheld under compression between said adjustmentnut'83 and the disc 81.

A cap 86 frictionally engages an upstanding.

flange H 9 formed on the lower end, of the Sylphon 85. Said cap 86 has a passagedfitting 90 formed with a lower annular shoulder? against which the top of the Sylphon 85 normally bears. Said fitting 8!) has an axial passagei92 to which is connected one end of a smalldiameter tube 93.

The tube 93' (Figs...1, 2 and 4) 'is connected into the T 42 on the discharge side of the compressor. Consequently, whenever the compressor is running, the pressure at the discharge port 41 is transmitted through the tube 93'and the passage 92 to theinside of the cap 86 above the Sylphon 85.

The adjusting nut 83 will ordinarily be set for a predetermined pressure, such as '75 lbs. per sq. in., so that when the pressure on the top of the Sylphon exceeds that amount, the Sylphon will The rod 82 extends into the 'pump bore. moving parts of the compressor. passageway '56 is on the low pressure side of the pump, the oil need not be underany substantial motor. communication with the interior of the tank the tank drops below a-predetermined point.

zbecontractedsand'cause :thevrod 82 to :press downwardly upon the cuplike cap 55. Downward movement of said cap causes the levers 64 to elevate :the stem 69 and the attached needle 59 toopen the passage :58.

Whenever the passage 58 is opened in this way, oil is caused .to flow from pipe.54 through the chambers 15 and vIll, along the groove :62 and .through the passageways 58 and 56 intothe The oil serves there to lubricate the Since the pressure head in order to make it flow into the pump bore.

As illustrated in Figures 1 and e, a pressure operated switch 94 serves to'start and stop the compressor. Said switch is'connected by a nipple H32 in the main airline 96 from the receiver. A safety valve 98 is connected in said line by a T 91. 'A pressure gauge 59 is positioned in the branch pipe 95. A cable l'i'lll connects the switch 94 1.0 a source of electrical energy and a second cable l'lll connects the switch to the The pressure responsive switch 94 is in are threaded in said auxiliary discharge ports.

Normally these ports are closed by spring pressed check, or by-pass valves lll'l, 161a and i'll'lb under the action of the corresponding springs I08, "18a and I881).

Said springs are of only suificient compressive strength to hold the valves shut until the 'pressure builds up to above a predetermined point, whereupon the valves open and the compressed air is caused to flow through the auxiliary discharge ports and their connecting passages into the main discharge port. The purpose of this is to save power when the compressor is being operated to bring the pressure in the receiver ll up to the predetermined point. For instance, if the pressure in the receiver is to be maintained between the limits of 120 to 150 lbs. per sq. in., so long as the pressure in the receiver is below that range, the auxiliary discharge port valves I01, ltiia and lislb remain open so that the compressor does not have to compress the air to'its final stage which would not be reached until the rotor vanes pass the main discharge port 38. The by-pass valves llli, liila and 10119 are not .relief valves but check valves and the retaining springs I98, iillla and 13b are very weak. When the pressure in the receiver II is up to its lower limit, say of 120 lbs. per sq. in., the by-pass valves close so as to get the full compression of which the pump is capable.

The operation Of the system will now be described in greater detail. In starting up, assuming that the receiver is under only atmospheric pressure, the end of the cable is plugged into a suitable source of electrical current, whereupon the pressure actuated switch 94 closes to energize the motor I2. The motor thereupon starts up the pump. As soon as the pressure builds up on the discharge side of the pump, air and entrained oil will be discharged through the .line 43, and past the check valve 46 into the oil separator 45. Air is there separated and conducted into the top of the receiver ll through the pipe 53. The separated oil passes out through the bottom of the separator 45, through the dis- 'chargeline 41 into the cooler 48. The fan serves to draw air over and through the coils 49 and thus increase the rate of cooling of the oil passing therethrough. The cooled oil is led from the cooler through the piping 54 into the metering valve assembly 55.

Until the pressure in the receiver builds up to the predetermined point, such for instance .as'75 lbs; per sq. in., the spring 88 will hold the Sylphon against the annular shoulder 9| to close the passageway 92. The metering needle 59 during this time will be closed position, closing the passageways 58 and 56 into the bore of the pump. As soon, however, as the pressure is sufiicient to overbalance the compressive action of the spring 88, the Sylphon will be contracted to open the lower end of the passage 92. Movement of the Sylphon is transmitted through rod 82 to the cap 65. Upon depression of the cap 65, the outer ends of the levers 64 will be depressed and .the inner ends of said levers will be elevated to raise the stem 60 and the attached needle 59, thereby opening the passages 58 and 56 into the bore of the pump. So long as these passages remain open, oil from the return pipe 54 passes through the chambers and 19 and through the openings 109 into the interior of said cap 65. From there, the oil finds its way along the groove 52 into the passages 58 and 56 and thence into the bore of the pump. As previously explained, the passage 56 is at a point in the pump bore where the pressure is relatively low, so that the oil flows freely whenever the passageways are opened by the needle 59.

Until the pressure in the receiver is built up to the range for which the pressure switch is set, air is discharged from the pump through the auxiliary discharge ports i96, 166a and 19611 and through their interconnecting passageways I05, I050; and H351) to the main discharge port 38. This, as previously explained, reduces the load placed upon the compressor during the initial stage of bringing the receiver up to pressure.

The check valve 46 in the discharge line 43 serves to prevent back pressure from the receiver H finding its way into the pump when the pump is not operating. With'the check valve 46 operating to out ch back pressure, the pressure in the pump bore drops rapidly as soon as the pump ceases to run, with the result that the pressure in the line 93 also drops and permits the spring 88 to expand the Sylphon and thus close on the passage 92. The light spring 6-8 serves to hold the metering needle 59 in closed position. e

The slot 36 in each of the vanes serves to introduce the higher of the two pneumatic pressures adjacent the working ends of the vanes into the space below the vanes indicated at S in Figure 3. In this Way pneumatic radial thrust is roughly balanced on each of the vanes.

Centrifugal force alone is relied upon' to hold the vanes in their extended position against the wall 32 of the bore. The lubricant injected into the bore by the metering needle 59 serves to lubricate the wall of the bore and also to lubricate between'the lateral edges of the blades and the end plates 2| and 21. end plates serve as guides for the lateral edges .of the vanes, there being only suilicient clearance to permit sliding movement over the inner faces of said end plates.

, The bore of the compressor is of such contour as to givea rapid throw-out of the vanes to full extension,'fo11owed by a gradual retrac-' tion after passing the inlet port. This gives a gradual compression without building up an abrupt load on the vanes.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claim.

We claim as our invention:

In a vane type pump assembly including a pump housing having a mixed air and oil discharge port on the high pressure side of the pump, an oil intake on the low pressure side of the pump, and means for recovering and returning oil from the air-oil discharge mixture to said oil intake, a valve for metering the oil returned to said pump through said intake comprising a valve housing having a connection opening therein incommunication with the discharge port of the pump, a spring-pressed bellows in said valve housing biased toward covering said connection opening, a valve stem having a needle'controlling said oil intake, means including a spring normally acting upon said valve stem to bias said needle toward intakeclosing position, and a force-transmitting member operatively connecting said bellows and said means to move said valve stem against the bias of the spring acting thereon to cause said needle to open said intake when pressure at the connection opening against said bellows over-balances the force of the spring biasing said bellows and uncovers said opening.

RUSSELL R. CURTIS. EWALD J. KIMM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,830,424 Codner Nor/-3, 1931 1,898,914 Viclrers Feb. 21, 1933 1,943,561 Staley Jan. 16, 1934 2,013,484 Aivaz Sept. 3, 1935 2,096,543 Hull et a1. Oct. 19, 1937 2,149,337 Deming -1 Mar. 7, 1939 2,264,616 Buckbee Dec. 2, 1941 2,455,297 Curtis et al. Nov. 30, 1948 FOREIGN PATENTS Number Country Date 432,215 Great Britain July 23, 1935, 432,252 Great Britain July 23, 1935 The

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