US1216119A - Rotary compressor and the method of operating it. - Google Patents

Description

A. 'HINZ. ROTARY COMPRESSOR AND'THE MEYHODQF U 'ERATlNG IT.

7 1 APPLICATION HLE DJULYl I. I911 i 1,216,119. Patented Feb. 13,1917,

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WITNESSES.-

A HINZ. ROTARY COMPRESSOR AND THE METHOD OF OPERATING IT.

APPLICATION FILED JULYIZII I911 Patented Feb.13,1917;

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r r A. HINZ. ROTARY COMPRESSORAND THE METHOD OF OPIRATING IT.

APPLICATION FILED JULY 21,!911.

- Patented Feb. 13,1917) 3 SHEETS-SHEET a.

' inn/Ewan A TTOHWE Y invented certain new and l UNITED STATES PATENT OFFICE.

,ADOLF Him, 013 rnANKron'r-oN-TnE-MAIN, GERMANY, ASSIGlIOR T roxonmr a WITTEKIN D MASCHINENBAU AK'IIENGESELLSCHAF'I OF FRANKFURT -ON THE- MAIN, GERMANY, A CORPORATION OF GERMANY ROTARY COMPRESSOR AND THE METHOD OF OPERATING IT.

Specification of Letters Patent.

Patented Feb. 13, 1917.

Application filed July 21, 1911. Serial No. 6 39,741.

To all whom it may concern: r Be it known that I, Anonr HINZ, a suh ]ect of the German Emperor, and resident of lira n kfort-- .)n-the-Main, (irinmany, have t'ul Improvements in Rotary Conuvrosors and the Methods of Operating Them, of which the following a, specification Rotary compr sors, as now cmistructed, are inferior to :reci 'nrocating piston com.- pressors in this respect that in the case of? a,temporarily low (ainsumptiou of gas or air the output oi. the compi cannot be adjusted to the momei'itary consumiiition. "u n'essor by pedicut avail. able only down to a certain. limit, the criti cal output at which the air or within the compressor is subject to vibrations which interfere with its proper operation. It was therefore necessiiiry hitherto, in the event of a. low consmuption, to o 'ierate the COIDII)IGSSOI under too great a load and to allow the excess of compressed air to escape unused.

In order to reduce this loss oi? energy, I

, air required for co have devised a method of: animation according to which, in case oi. a ool'u'lumption lower than the ni'irmal output of the compressor, the latter will be disconnected temporarily from the time that pm we in s id. pipe exceeds the allowableminimum l'll'L sure (that is to say, the PIOSSHIQ at which the operation of the compressor becomes jerky or subject to vibrations) until the pressure has fallen again to said minimum pressure or to an intermediate iiure, During the times the compressor is disconnected from the pressure coiuluit, the suction eli'ect re duccd so as to diminish as far as possible, the output of the compri 'ir and the on orgy required for its operation. During these times of interrupted eiimncction, the imption is taken from stored in the various the "amount of air parts of the pressure conduit. Owing to the reductitm of the suction effect during the periods of interruption, according to my method of adapting the operation of a pre 'urc pi pe, from the rotary compressor to the consumption, of

air, the energy required for the operation of the UOIIIPIGSSO? during such periods 15 materially small :1- than that required when increase gradu lily; d uriug th second period the eompri'" "I )1' is disconnected entirely sure in said c1" nduit will'hc reduced by the consumption, "dud furthermore (luring this second period the energy required to operate the comprr ssor is reduced as for as possible, by diminishing the suction efi'ect.

The delivery of air or gas is interrupted as soon the suction effect or suction pressure has been reduced by about of an atmosphere. If however in carrying out my .method the piessure at the suction end is reduced inthe well-known manner, 'by means of a throttling device which after disi'zonnecting he compressor from the deliver conduit is hrought immediately into ire conduit, sotiiat the presthe position in which the compressor can be run idle witl the least expenditure of energy, the prissure at the suction end may be reducedv to of an atmosphere (absolute measure) andv even. less. In this case the con'ipressor while running idle will require only about 1 0 power.

of the normal operating With this mode of operation, the load on the compressor will vary as it is run alternately under f1 ill load and idle, and aq'cord' mg to my invention the. load fluet'uatlonsf thus arising my be minimized by closin the throttle gr: dually until the point corresponding; to the caitiealicutput is reached,

and their bringing the -throttle"into.the

proper position for the niodt economical idle he reason for.

running of the compressor. this 1s found in the fact that when throb 'tling gradualh by small amounts, sayi of an atmosphere, to the pointat which the compressor begins to'vibrate or labonthe output may be diminished without inter rupting delivery from the compressor, since owing to the reduction of the output the compression ratio will increase notwithstanding the relatively low pressure of the air at the suction end.

My improved method may be carried out automatically,

set id operation periods to .the other at the proper time. For this purpose, a check valve or like device is provided in the delivery conduit and the throttle arranged in the suction conduit is placed under the influence of the pressure in the delivery conduit on one hand, and on the other hand under the influence of a spring or other opposing force which acts more powerfully during the open position of the throttle than during its closed position. With such an arrangement, the existence of maximum pressure in the delivery conduit will close the-throttle automatically, so as to reduce the pressure at the suction and. Now it is well known that in a rotary compressor,

other factors remainin unchanged," the compression ratio, that is to say, the rati between the final. pressure of the compresse air and the pressure at the suction end, is approximately constant. Therefor the abovementioned reduction of pressure at the suction end. will automatically" and simultaneously reduce the final pressure obtained in the compressor,'to a point where such pressure will be below that prevailing at the time in'tlie delivery conduit. Consequently, air will begin to flow'from the delivery conduit back intothe compressor,

' thus causing the check valve in the delivery conduit to close automatically. This disconnects the compressor from the delivery conduit.

until. the pressure in the delivery. conduit has fallen an amount equal to the difference between the maximum pressure and the opposing force.

Another way oi reducing the'ip ressure at the suction and according to my invention consists-in utilizing' the. excess of air. For tlllS purpose, after the pressure within the .del-ivery conduit has risen above the minimum pressure, a portion of the air-delivered by the compressor isthrown'by an lnjGCtOI' or like apparatus against the air which is, K55.

on its way to the compressor, and after the compressor has been disconnected fromthe delivery conduit, the entire amount of air delivered is thus directed against the suction current. When a check valveis pro-v vided in thedelivery conduit, the returning ofa. portionof the air from the delivery end to'the suctionflend, indicated, will reduce thepressure at the suction. end sulliclently to cause an automatic closing of said valve so as to disconnect the compressor that is to. say; with an automatic change from one of the above-dc;

' conduit.

The throttle is notopened again from the delivery conduit. Vhen at a later stage the entire amount of air is returned to the suction end, as described, a further material reduction of pressure takes place at the suction end and in the compressor, up to the check valve, thus again reducing the power required for operating the compressor during the time it is disconnected from the delivery conduit. In this mode of carrying out my invention, the regulation may be controlled not only by the pressure prevailing in the delivery conduit but bythe output of the compressor. Furthermore, since the air returned from the pressure end of the compressor to the suction end is warm so that warm air is supplied to the compressor, the friction at the rotors of the compressor is diminished, this resulting in a further reduction of the power required. to run the compressor during the time it is disconnected from the delivery 'Itis diflicult to obtain as considerable a reduction of the pressure at the suction end when employing only the above-indicated injector action as'with a throttling arrangement in the suction conduit. If therefore it is desired to secure .the advantages of the injector action and at the same time toobthe manual closing' of a valve or out-oil 1 slide, or by means of an auxiliary motor entering into action when the maximum pressure is attained. After the connection has been interrupted at the delivery end, the pressure may be reduced at the suction and so its to reduce the power required for operating the compressor.

.The .novel features of my'invention are defined in the appended claims.

Seven typical examples of compressors embodying my invention are illustrated in the accompanying drawings, urc: 1'is an elevation, with parts in section,

showing in diagrammatic fashion an ar rangemcnt in. which the pressure of the coin pressed fluid is utilized to govern the oper ation autmnatically;'Fig. 2 is a fragi'ncntary sectional view illustrating a regulator constrilction difi'crin r slightly from that shown m Fig. 1; Figsdfi and 4 are sectional views representing two further constructions of regulators; Fig. 5 illustrates dlagraiumatt cally a form of my invention in which the in which Fig-' compressed fluid is returned to the suction end; Fig. 6 shows diagrammatically a struc F ig. 1, the rotary compressor 2 (of'any suitable type), driven by a suitable motor 1, re-

ceives its sup 1y of air or other fluid to be compressed, t irough the suction pipe 3 and delivers such fluid in a compressed condition through the outlet 15 into the delivery conduit t from which the compressed air is led or distributed to the place of consui'nption. In the suction pipe 3 is located a throttle valve 5 pivoted to the pipe by meansv of a rock shaft (3. Upon this shaft is secured an arm 7 connected by a link 13 with the rod .8 of a piston 10 movable in the cylinder 9. A )ipe-12 connects the upper end. of the c hnder 9 with the delivery conduit 4, so' t at the piston 10 is exposed on one side to the air pressure prevailing at that time in the delivery conduit. A suitable force, constituted in the present case by the tension of a coiled spring 11, acts against the other side of he piston and therefore in opposi.

tion to the pressure exerted on the upper face of the piston... The tension of the spring is preferably adjustable, as by providing a screw connection betwecn the piston 10 and its rod 8.

i A suitable check device, such a check valve 14, is interposedbetween theoutlet 15 and the delivery conduit 4.

The tension of the spring 11 is adjusted toa point where it will balance the air aressure exerted against theupper face 0 the piston 10 when the consumption of air and the output of the compressor are normal. In this case the throttle valve is in the open position indicated by solid lines.

When the consumption of air is smaller than the normal output of the compressor 2, the latter forces into the delivery conduit 4 a greater amount 'ofiiir than defused. The resulting clogging causes the pressure in the delivery conduit 4 (includin the piping connected tl'lerlwith) to rise a )ove the'normal pressure. This 111 turn, will gradually force down the IJISiZOX]. l0 and move. the

throttle valve 5 so as to reduccsthe efl'ective cross section of the suction pipe 3.1 Under to about of thefnormal output. When the output has fallen to the critical point, the throttle 5 will be in the intermediate'po sition indicated by the dotted line in Fig. 1.

When however the consumption of air This will continue until the so-called critical j output 1s reached, winch as a rule amounts falls below the (ritical output, the continued increase of pressure in the delivery conduit 4 will cause the throttle valve 5 to assume the extreme position indicated by the dot tween the compressor and the delivery con-- 1 duit L The reduced amount of air then.

still. delivered by the compressor is'allowed to escape through an, outlet A.

While the coiripressor is cut off from the delivery condu t, the compressed air rer ui red at the places of consumption is taken romthe amour t stored or contained in the delivery conduit 4, so that the pressure within said conduit is reduced. When the reduction has p -oceeded to an extent correspondingg, to the friction of the piston 10 in the cylil'ider 9 and to the friction at the pivot joints of he connections 7, 13, 8, the spring 11 will restore the piston IOand the throttle valve 5 to the intermediate position indicated by dc tted-lines. The com ressor 1.0 will then operate with about it of t e normal output, the increasing pressure at the outlet 15 willop en the check valve 14, whereupon a further increase in the )ressure of the air now passing through t e pipe 12 will force the iston lddownward These operations or periods of operation will he goes above or above.

In this form of my invention, the opposing; force constituted by the tension of the spring 11 is equal to the n'iaxin'nun pressure,

conduit at. It will therefore be understood repeated automatically as often pressure )elow the limits mentioned a that with an ar angement such as described above the air pressure 111 the delivery conduitanay be kept almost absolutely constant.

Instead of reducing the pressure at the.

suction end by the interposition of a throttle in the slilction c )nduit, the same result may be obtained, of course, by throttling the air current at some other-suitable place. For instance, with a multi-stage compressor (this being a well-known type oflrotary compressor) the air current may be throttied at any on: of the com ressor stages or siinultaneouily at a'plural ity of stages. The other parts or stages ofthe compressor will continue tieir normal operation even while some of the parts or stages are subjected to the throttling action.

hen it is desired to increase the Sensitiveness of the regulator, this may be accomplished by means of a relay provided.

with a governing connection, an example of such an arrangement being shown in Fig. The parts 1, 2, 4,14, 15 not represented in Fig. 2, and pipes 3, 12, are to be the same as in-Fig. 1. The pipe 12 leads to a cylinder 16 in which is arranged a piston 17, subjected on one side to the pressure prevailing in the delivery conduit 1 and in the pipe 12 connected therewith, and on the other side to the opposing action of a spring' 18, the tension of which may be adjusted. The piston rod 19 is connected by a transverse lever 20 with the rod 21 vo-E a piston 22 arranged to move-in a. cylinder 23. The rod 21 extends entirely through the cylinder 23, and is pivotally connected at its lower end with the link 13, the said link, together with the arm 7, rock shaft 6 and throttle'valve 5 being of the same construction as described with reference to Fig. 1.

The opposite ends of the cylinder 23 are connected with pipes 24, 25 respectively by means of which a. suitable medium under pressure may be conveyed to one end of the cylinder and from the other end. Compressed air from the pressure chamber of the compressor may be utilized for this pur- "it '(the spring 18 pose.

lay piston 22 and of the throttle 5 may correspond to each particular position of the piston 17, a, governing connection has been provided. In the particular instance shown in hi 2, the lever 20 is pivotally connected, between the points at which it is connected with the piston rods 19, 21 respectively, with a slide valve rod 26 carrying two con nectcd piston valves 28, 29 contained in a valve chest 27. This chest is connected between. the valves '28, 29, with a pipe 30 for the supply oi the medium under pressure (for instance, compressed air from the compressor). At the ends of the chest or casing 27 are provided outlet pipes 31 and 32 respectively, the distance between the outlets being greater than that between the valves 29. The pipes 24., are connected with the chest 27 at points the same distance apart as the valves 28, 29.

In the central position the slide " elves 28, 29 cover the orifices of the pipes 24, 25 respectively, sure supplied through the pipe 30 cannot reach the cylinder If however the piston 17 s moved upward owing to an increase of pressure in the delivery conduit same time), the lever 20 will swing or rock about its connection with the piston rod 21,

I since the piston their connections with the In order that a definite position of the resumption diminishes, the throttle so that the medium under presbeing compressed at the raise the slide valves 28,. 29, so that the medium under pressure will pass from the supply pipe 30 through the valve chest 27 to the pipe 24-aud to the upper end of the cylinder 23. At the same time, the chamber below the piston 22 will. be placed in communication with the outlet pipe 32, by means of the pipe 25 and the lower portion of the valve chest 27.

The piston22 being forced downward by the pressure of the medium admitted at the top of the cylinder 23, the air or other medium contained in the cylinder below the cylinder will be expelled through the pipe 32. At the same time, since now the piston 17 may be considered stationary, the lever 20 will swing about its left-hand end (that is to say, about the pivot connecting it with the piston rod 19). This movement will raise the slide valves 28, 29 to their initial central position in which they cover the ports of the pipes 21, lock the piston 22, of fluid contained above and below the piston respectively. When the piston 17 thereupon moves down under the influence of the spring 18 owing to a reduction of pressure in the delivery conduit 4. and in the pipe 12,

similar operations will be performed. That piston through the pipe 25, and to allow fluid to escape from above the piston 22 through the pipes 24, 31. This will cause the piston 22 to move upward so that the lever 20 will swing about its leftdiand end as a fulcrum, restoring the valves 28, 29 to the position shown in Fig.

In its general features, the operation of the apparatus shown in Fig. 2 is the same as that of the arrangement shown in Fig. 1. As long as the consumptionof air equalS the output of the compressor, the several parts of the regulator remain in the tion indicated by solid lines. Vhen con- 'ill be closed gradually, and when the cutlnit has been reduced to about -71- of value,

cated by dotted lines.

indicated by dot-a-nd-dash lines, in which the checlrvalve 14 closes to disconnect the compressor 2 from the delivery conduit 4.

If, after a certain maximum pressure. has been exceeded, the throttle 3 brought in mediately into the extreme (substantially 25 and thus hold orv by confining the bodies posicannot move. This will its normal, I the throttle and connected parts will be in the interl'nedii-ite position-indie Should the cousin! tion dur-reasestill further, the parts of tie regulator will assume the extreme position closed) position corresponding to the idle running of the compressor, so that the pressure at the suction end is reduced of an atmosphere (absolute) or less, this In order to avoidthe load fluctuations to will 'efi'ecta material further diminution of the power required ,to operate the compressorfdurin the time it is disconnected from the delivery conduit. According to the example shown in Fig. 3, the pipel2 (leading trom the delivery conduit 4) is connected with the upper end of a cylinder 337,-s that the pressure prevailing-in the deliverv conduit will act on'the upper surface'of a piston 34. The piston rod 35 is provided'zwith a pin 36' pivotally connected with the link'13r which is connected with the throttle in the same manner as described before. The pin 36 further passes into a slot 37 provided in the arm 38 of a lever fulcrumed at 40 upon a bracket 39. The other arm 41 of this lever carries a weight 42,

which for instance may be adjustable along an are 43 and secured after adjustment, say by mealns'bt a set screw.

The weight 42 is adjusted to such a position. that at a predetermined maximumpressure the eflect or moment of the Weight (Weight multiplied by horizontal projection of its radius from the fulcrum 40) will balance the pressure exerted on the upper surcated by "the dot'anddash lines, which cor- ,responds to the idle running of the compresson. In this position the rocking of the lever 38, 41 has brought the welght 42 nearer to the vertical planepassing through the fulcrum-40 so that the effective leveragejofsaiiil weight, that is to say, the horizontal-iptojection of its distance or radius from the fulcrumr40, has been reduced, so that the effective moment of the weight has become; smaller than the fluid pressure 'act-' .ing on the piston 34 when the latter is in its upper position.

closing of the throttle causes the compressor Since the substantial to be disconnected from'the delivery conduit" (by the action of the. check valve 14), the pressure" will fall in the delivery conduit 4 and in the pipe 12, but the welght 42 will be unable tov bring the piston 34 back to :its upper position until the reduction of pressure 1n. said delivery conduit corresponds to'the automatic reduction in the effective'leverage of the weight,42.

By'adjusting the weight 42 along the are 43 the minimum pressxn'e may be varied within wide limits.

which the mot or 1 is subjected by the sudden increaseand d screase of the load on the compressor 2, I may employ an arrangement such as shown in Fig. 4. Here the output is at first reduced gradually, as in the constructions illustrated by Figs. 1 and 2, until the critical output is reached, and then the throttle 5 is b1 'ought into the approximately 9 closed positior which corresponds to the idle running of the compressor. The pipe 12 is connected with the cylinder 44 havlng a hollow extension 45 at its upper head. A

double piston is employed, composed of a large piston 43 in the cylinder 44, and of a small piston 47 in the extension 45. The annular upper surface of the piston 46. is exposed to the pressure prevailing in the delivery conduit and in the pipe 12; a coiled spring 48 presses a ainst the lower surface of the piston l6. lhe space below the said piston. is oper. to-the surrounding air, and the piston has a pivotal connection with a rod 49, pivota 1y connected at its lower end with the arm 7 on the rock shaft Got the throttle valve 5. When this valve is open,

the piston is in its upper position, slightly below the per; connected with the'pipe12.

At a point slig htly above the position of the pistondfi when the throttle 5 1s inthe intermediate positim corresponding to the ci'itical output, a pipe 50 leads from the cylinder 44 to a point if the extension 45 above the piston 47. v s

The tension of the'spring 48 is so adjustance the min'inum pressure exerted on the annular upper surface of theflpiston 46. hen the consumption of air'dereases, the

ed in any sutable manner that with the throttle 5 open the spring tension 'will balresultin incroaseof pressure in-the deliv ery con uit aid in the pipe 12.-Wi li force th piston 46 down gradually and-shift the throttle 5 so an to decrease the. output of the compressor. When the critical output is reached '(with the throttle 5 in the position indicated by the dotted line) the p1ston 46 willbe below the lower end of thepipe 50 so. that the laiter will be in communication; with the pipe'12. The pressure in this lat te'r pipe will therefore also prevailinfthe. chamber vof' the extension 45 above the pis-= ton 47. On account of the increased total. I pressure tending to force the piston 46 down,

the spring48 will be compressed strongly,

and the throttle 5' will be brought into the extreme, nearly closed position indicated by the dot-and-c'l'a sh line, which position corre sponds to the idle running of the com-' pressor.

\Vhen the compressor iscut off from the delivery condt it 4, the pressure in the latter 7 will fall, but ihe spring 48 willnot-be'able to return the 'col'npound piston 46, 47. to its uppermost position juntil the pressure has been reducedby an amount corresponding to the pressure exerted against the effective surface of the small piston 47;. Thus when the minimum pressure is' restored the compressor will be connected again with the delivery conduit.

By properly-selecting, the effective area of the small piston 47 the difference between maximum and minimum pressure may be in creased or decreased within wide limits. 7

The construction shown in Figs. 1 and 2 mayalso be rnade'to operate inthe same manner as the device shown in Fig. 47, if instead of-thes'prings 11 and 16 respectively.

I'employrlouble springs, that is to say, two springs one of which (like the spr ngs 11 and16) engages the piston and the cylinder head at all times while'tlieother comes into action only after a certain travel of the piston; the first part of the travel of the piston will therefore compress only one of the springs and adjust the throttle 5 to its intermediate position, Without interrupting the connection between the'compressor and the 'vdeljyery conduit, while the further travel wilhle ompi'ess both. springs and bring the throttle o tothe extreme position, in which -'the check valve disconnects the delivery conduit4 from the compressor 2.-

in Figs. 3 and-4: can'be increased byusing in connection therewith a relay. of the same character as shown in Fig. That is to say, one case thepiston 34 of Fig. 3 with its rod 35 and. pin 36, cylinder 33 and weighted lever arrangement 37, 38, 39, 40,

'11, 42, 4.3-will take the place of the parts 16,

2 remaining unaltered, with the. lever 20 ivoted in this case to the piston rod 35. n the other case'the'cylinder 44, 45, double piston 46, 47, spring. 48 and connection 50 would be substituted for-the parts 16, 17,

.l8 ofIFig. 2, the otherparts of Fig. 2 relnai'ning unaltered, with the left-hand end of-the lever 20 pivoted to the rod' or the compound piston 46, 47.

the excess 0 In the "form of my invention illustrated by Fig. 5, the reductionoffthe pressure .at the suction end, required. to carry out my method of operatiomis obtained by utilizing air delivered bythe compressor. Fromthe. outlet"15 of the compressor 2 a pipe'51 leads to in-injector or rather to the compressor.

ejector 52-, indicated in' diagrammatic .fas'hion, said ejector being so disposed within the suction pipe 3that the current of air, issuing from the'ejectornozzles will be .ilirecte'd against the current ofair flowing I A shut-off valve 53 or equii-ale'nt device .is provided at a suitable point of the pipe 51. Furthermore, a-checlcvalve 14 is interposed between the delivery conduit 4 and the point at which the pipe 51 is branclied'off from the outlet 15.

Tliesensitiveness ofthe regulators shown When the consumption. of air is considerably below normal, the; compressor is operated with the valve 53 closed,"until the pressure in the delivery conduit Pl es attained a predetermined value. Then the'valve 53 is opened to such'an extent that the excess of air over that required for consum tion will flow through the pipe 51 to the :eJec't r 52. he air current discharged at'the-moss zles in opposition to the main air current,

as indicatedby arrows, will reduce the pres sure at the suction end to such an' extent that the pressure at the outlet 15 will fall .below the pressure prevailing in the delivery conduit 4, so that the check valve 14 will close automatically and disconnect the com-.

'ressor 2 from the delivery conduit P."

lhereupon the valve 53 is opened fully, causing the entire amount of air delivered by the compressor 2 tov be returned to the suction pipe 3 through the pipe 51 and ejector 5'2, and to be discharged against the current of'air flowing to the compressor. The strength of the opposing current issuing from the ejector nozzles being 'tl1uS .increased, the pressure at the outlet 15' is reduced to'a minimum depending on-the .par-

ticular conditions of each individual case..

In this form of my invention also, the air required for consumption during the time that the delivery conduit is disconnected from the compressor, is taken from ;-the

amount stored in the .said c0nduit,including the distributing pipes; this will cause the pressure to fall in said conduit and as soon as it equals the pressure, in Ithe outlet 4 15', the check valve 14 will operu Thereupon the valve 53 is closed and the operation 18 repeated in thesame manner Whenever the consumption falls considerably bee low the normal output of tl compressor.

It is advantageous to us'e'ithemethod" 0-ioperation described with reference to Fig;

5,- i n conjunctionwith the nithodemployed" according to Figs. 1 to 4 inclusive, that isto say, t he pressure at the suction tend would be reduced by meansusuch as the throttle valve 5 shown in Figs. 1 to 4, and' in addition to this,the air deliveredv bythe compressor after it has been cut oil from the delivery conduit, would be r'eturned to the suction pipe, and discharged into thesaine in the directibn contrary to'theflow of the pressor duringthetime itis disconnected from the delivery conduit, will bereduc'ed to a nunimuin.

Figs. 1 and 5, andfthe'fs u'cture Shown in air on its way to the compressor. In this manner the power required tofrun the com 7 1-25- Thus, the structure; illustrated by Fig. 6-combinesthefcatures off Fig.f'7 is 'acombination of. tl1e l eatures shown In Figs. 1, 3,. an'd 5 that ist'o say,'the construction of Fig. 7 differs frolnthat 'of Fig. 6 chiefly by thefact-that,Fig.",7'employs the weighted-lever resistance 4 1, 42,

a throttle loca ted in the suction c0nduit, a y In testimony whereof I have signed this piston operatrvely connected with sald spepificatlon in the presence of two subthrottlq, a spring exerting; pressure on said scrlbing Witnesses.

pistonxn one direction, und means for ca'us- ADOLF HINZ v #3 ing the pressure prevailing in the delivery WVitnesses:

duit of the compru sor to act on the pis- JEAN- GRUND,

t6uiin npposition to said spring. CARL G'RUND.

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