US2178660A

US2178660A - Compressor regulator

Info

Publication number: US2178660A
Application number: US181656A
Authority: US
Inventors: Allan O Carpenter
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1937-12-24
Filing date: 1937-12-24
Publication date: 1939-11-07
Anticipated expiration: 1956-11-07

Description

No'v. 7, 1939.

A` o. CARPENTER 2,178,660

COMPRESS 0R REGULATOR I I `Filed Dec. 24, 1957 2 sheets-sheet 1 HIS ATTORNEY.

Nom 7, 1939. A. o. CARPENTER 2,178,660

COMPRESSOR REGULATOR Filed Dec. 24, 1937 2 sheets-sheet 2 .far

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17 Fig-?.

` INVENTOR Wlan ayvmfei@ BYMf/g HIS ATTORNEY Patented Nov. 7, 1939 l PATENT OFFICE' 2L178,660 CONIPRESSOR REGULATOR Allan 0. Carpenter, Corning,

any, Jersey City,

Ingersoll-Rand Comp N. Y., assignor to N. J., a

corporation of New Jersey Application December l Claims.

This -invention relates to regulators for motor driven uid compressors, and more particularly to a regulator wherein the speed of the motor is operated at either maximum speed or minimum 5 speed in accordance with the output of the compressor.

A motor driven unit of this sort comprises a m'd compressor driven-by a motor or engine, such as an internal combustion motor or a steam engine, and a receiver tank to receive and store the fluid under pressure discharged by the compresser. In the operation of the unit, the discharge of iluid to the receiver continues until the pressure therein reaches a predetermined l5. amount, whereupon, a device provided on the compressor operates to prevent further discharge of fluid to the receiver tank (commonly termed unloading) and, at the same time, decelerates the compressor driving motor to its minimum,

0 or idling, speed. The compressor then continues to operate in this manner until the pressure in the receiver tank falls to a predetermined mini,- mum point and then the device operates to permit the compressor to again discharge fluid to 25 the receiver tank (commonly termed reloading"), and to accelerate the motor to its maximum operating speed.

With this mode of operation the compressor, under light loads, will iiuctuate rapidly between 3@ its minimum, or idling, speed and its maximum speed, resulting in ineicient and ineconomicalv operation ofthe unit.

It is, accordingly, an object of the present invention, to provide a means whereby a motor 35 driven compressor unit may reload while the motoris operating at its minimum speed.

It is a further object to provide means whereby, under light loads, it is impossible to reload the compressor at the maximum motor speed un- 40 til a predetermined minimum discharge pressure of the compressor is reached.

A still further object is to provide means whereby the motor can not accelerate to its maximum speed to reload the compressor, under 45 light loads, until a predetermined minimum pressure is reached in the receiver and then only after a predetermined time delay.

It is a still further object to provide a device whereby resumption of maximum motor speed, after reloading, is prevented under light loads .Y and permitted when reloading occurs under heavy loads..

Another object is to provide a de'dce for con- 55 Atrolling the speed setting of the governor' in action engine 'l directly connected to 24, 1937, Serial N0. 181,656

cordance with variations in the discharge pressure of the compressor. i x

Another object is to provide a regulating device varying in accordance with the discharge pressure of the compressor whereby, on the oc- 5 currence of a predetermined high discharge pressure, the motor speed is reduced from the maximum speed to the minimum speed; of a predetermined maximum pressure, the compressor unloads; of a predetermined low pressure, the compressor reloads; and of a predetermined minimum pressure, the motor accelerates from the minimum motor speed to the maximum motor speed.

These and other objects will be -readily apparent from the following specication oi which the drawings form a part and in which y Figure 1 is a view partly in elevation and partly in section illustrating vthe application of the present invention to a compressor unit, and in which the view cf the governor is increased in size in order to bring out the details more clearly.

Figure 2 illustrates in section the loading device shown in Fig. 1, and Figure 3 is a view partly in elevation and partly in section of part of the governor controlling device constructed in accordance with the principles of this invention.

It will be noted by referring to Fig. 1 that the compressor unit consists of a fluid compressor I mounted on a frame 3 supported by wheels 5., The frame 3 also supports an internal combusdrive the uid compressor I. Fluid tobe compressed by the compressor I is supplied by the inlet conduit 9 and the conduit II- delivers the compressed fluid discharged from the compressor to the receiver tank I3. Y The inlet' conduit 9 contains a means to unload and reload I5 which is illustrated in detail in Fig. 2. This device consists of a casing I1 connected to the conduit 9 at its upper end and to the compressor I at its lower end. The casing is so designed that aportion of the wall extends within the outer walls thereof and forms valve guides I9 for the balanced cylindrical reciprocating valve 2|. A plate 23 closes an opening 24- in the side wall of the casing I1 and is provided with a recess 26 in whichfrests a spring 25, normally urging the cylindrical valve 2| towards Vthe right or open position. With the valve in the open position shown in Fig. 2- it is readily apparent that uid may enterl through the conduit 9, pass aroundthe valve 2l and ow into the compressor.

, piston chamber and to transmit its motion to the valve 2| by bearing on the pin 33 formed as an integral part of the cylindrical valve 2|.

When the pressure exerted by the piston 29 on the valve 2| is suilcient to overcome the force of the spring 25, the cylindrical valve 2| will be moved away from its seat 3|. Movement of the valve from its seat will shut cif communication between the inlet conduit 9 and the compressor I when the ribs 35 are moved into alignment with the walls of the casing I1, which form the guides I9 for the valve 2|.

At one side o1 the piston chamberl 21 and communiting therewith is a pressure operated auxauxiliary valve iliary valve, generally designated as 35. This valve serves to control the admission of pressure uid to the piston chamber, and thus themove-4 ment of the piston against the force of the spring 25. The auxiliary valve 36 comprises a valve body 31 communicating directly with the receiver tank I3 through the conduit 39. In order to prevent continuous communication between the receiver tank and the piston chamber 21 an proper 4| is normally pressed on the seat 43 by the member 45. As is apparent from the ligure, the member 45 transmits the pressure of thespring 41, which is compressed between this member and the bushing 49. Y

In the event that the pressure in the receiver tankis sumcient to move the auxiliary valve proper 4| from its seat 43 against the compressive Vforce of tt spring 41, a second seat 5| is provided by a bushing 53 in the auxiliary valve body 31 and providing the valve 4| with an appro,V priate face to rest on this seat. By adjusting the bushing 49, the compression of the spring 41 may be or decreased, and the pressure at which the valve 4| willleave its seat 43 and seek its seat 5| may thus be predetermined, and also theprsure 'at whichthe valve 4| returns to its seat 43.

From the above description it will be seen that when the prmure in the receiverA reaches a'predetermined point, which is suflcient to overcome the compressive force of the spring 41, the valve 4| Awill open, thereby permitting fluid to Ilowf past the valve seat 43, through the channel V55, into the piston chamber 21, and cause the piston to Push the tion. The pressure which is necessary to 'open the valve 4| is greater Ythan that required to maintain the valve open, since the eiiective pressure area ct the valve is increased by the portionY the valve which seats of the diametrlcal area of onthe seat 43 when the valve is closed.

' VVthat the spring 41 can return Howevenwhen the pressure falls suiiiciently so seat 43, the-tluid'trapped in the chamber 21 must be allowed to escape. Thisvis-'accomplished by permitting the uidtc ow through the channel 55, by-the seat-5L and through a central opening 51, in the bushing 49, surrounding the member 4l to the atmosphere. Whenthe fluid has been exhausted from the piston chamber, the com-- preasive force of thev spring will move 'the cylindrical valve 2| from its closed position to its open position and return the valve 2| to its seat 3|. s

reciprocate in the i bear against a cylindrical valve to its closed p0si- -against a hooked lever the valve 4| to itsA .By way of summarizing the action of. this device, it may be said that'when the pressure inthe receiver tank reaches a predetermined point the auxiliary valve opens and permits the fluid pressure to close the cylindrical valve tof unload the machine. When the pressure has fallen to a predetermined low point, the auxiliary valve closes, the fluid pressure escapes from the piston chamber and the cylindrical valve opens to again reload thecompressor.

With reference to Fig. 1 `the speed oi the internal combustion motor is controlledby a governor, generally indicated at 59, which consists of a shaft 6| directly connected to the shaft (not shown) of the engine. A gear 63 secured to a ange on the shaft 6| is provided with ears 65 on which are fulcrumed weights 61. gine rotates, the centrifugal force moves the weights away from the shaft 6| in accordance with the speed of the motor, until they reach their' outermost position at which time they act to prevent further increase in the speed of the motor. Rollers 69 mounted on the weights 61 plate sion on the shaft 6|. Hence, as the weights move outwardly vthe governor spring 891s compressed and the motion of VthepIate 1| is transmitted, through an anti-friction bearing 13, to a plate 15, formed integrally with the pin 11 coaxial with and slidably mounted on the shaft 6|.

The plate 15 is provided-with a clevis 19 surrounding and pinned to lever 9| fulcrumed on theW ment of the weights 61 inwardly toward the shaft 6|, moves the plate 1.| in the same direction, thus pivoting the lever 8| about its iul'crum 83 and moving the butteriyvalve 81 by means of the rod 95 toward the open position to accelerate the Conversely, Awhen gine is increased, the lever 9| and rod |15,v under the influence of the spring 99, move the butterily valve in the opposite direction to decrease the fuelsupply to the motor.

As is customary in centrifugal governors, the weights 61 are resiliently held in their retracted position and to this end a spring 89 is provided. 'I'his spring is housed in a casing 9| secured to the frame of the motor and having a bore 93 extending therethrough. The bore communicates at one end with a recess 95 in which the spring is contained and has a plunger 91 extending therethrough and provided with a flange against which one end of the spring 89 rests. The other end of the spring pushes a member 99 against the projection ||l| formed on the lever 8|.

'I'he external end of the plunger 91 bears |93, fulcrumed on the 9|, and is adapted to transmit forceto The speed setting of the by the amount of the casing compress the spring 99. governor is determined force the weights 61 must exert to mcve the plate Hence, if the hooked lever forces the plunger 91 to compress the spring to the limit, a much greater speed of the motor'willbe necessary in order that the centrifugal force of the weights 6l shall be suilcient to move -the plate 'Il' outwardly from the shaft against the resistance oi' the'spring I9. Under these conditions, consequently, the plate 1|, the lever 3|. and rod 95,l wil not be moved to throttle and 1| surrounding an exten-v the speed of the encompression When the endecrease thespeed of the motor until the speed of the motor exceeds the maximumspeed at which it is desired to operate the motor.

, against the compression the conduit 33.

valve itil will remain Conversely, if the hooked lever |03 is moved :o that the spring 89 may expand, move the ilunger 91 to the left, the plate 1| may be moved iut from the shaft 6| by the weights 61 when ;he motor is running at a much slower rate. The result is that the motor will operate at a greatly reduced speed and a slight increase in speed will cause the weights to move the plate 1| further away from the shaft thereby throttling the motor intake and decreasing the speed to the desired Thus, if the position of the hooked lever |03 is regulated, the speed setting of the governor may be regulated, and or that reason a pressure responsive device having two control positions is connected to this lever by the tie-rod |05.

The details of the regulating mechanism are best illustrated by reference to Fig. 3. 'The reguiating mechanism consists of a chambered casing im, having a bore |09 communicating with the piston chamber lil. The piston`||3 in the chamber is secured to a shaft ||5 extending through the bore |09 and connected to the lever M1 fulcrumed on the frame of the motor at lld.- At the end of the lever opposite to that on which the shaft H5 is secured, is the tie-rod |05 which connects with the hooked lever |03. In one end of the chamber Hl is a recess |2l in which.v rests a spring |23 bearing against the piston M3 and normally urging it toward the right.

The end of the chambered casing H01 is closed by a plate E25 suitably secured thereto. A conduit i2i extends through this plate chamber lll and bears against the piston H3. Slots 629 are provided in the end of the conduit which hears againstthe piston to provide a large' This conduit opening into the piston chamber. communicates with a means responsive to the discharge pressure such as an .auxiliary r`valve mechanism, generally indicated at |3l, which is similar in construction to the auxiliary, valve mechanism i described in connection with the unloading and reloading device, V.and also communicates with the receiver Since the structural features of the auxiliary valve mechanism auxiliary valve mechanism 3E, described in connection with the unloading and reloading device, the same numerals with a numeral t added as `a s'nx are used toindicate'sirnilar parts, and description or the auxiliary valve |36 Will be dispensed with. Y Likewise the operation of this valve is the same as the operation of the previously described valve, except for the fact that diierent receiver pressures are employed to open and close the valve. The regulation ofthe pressures, of course, being accomplished by varying the compressive torce o the spring Bi.

During the operation of the compressor the closed during the initial period of loading the receiver. However, when the pressure inthe receiver tank rises to a point where it isrsuiiicient to move the valve 4| Il'irom its seat @3i against the compression of the spring fili, uuid will now from the receiver tank past the seat 613i, into the conduit |21, and escape into the piston chamber il! thereby exerting pressure on the piston l I3 and moving the piston of springy |23 toward the left. The movement of the piston is transmitted to the lever ill by the shaft l|5 and consequent movement of the tie-rod |05 will move piston chamber, the piston into the piston tank by means o iti are similar to those of theV upon the will of the operator who the hooked lever away from the plunger 91 and permit ,the spring 8B to expand.

Releasing the compressive force on the spring 89 permits the lug l0 bearing' against the member 99, to move further to the left with the result 5 that the butterfly valve 81 closes. The motor will then operate at its minimum speed as was previously explained: This state continues so long as the valve 4|| is resting on its seat 5H and allowing the passage of iluid from the receiver tank 410 by the seat 43|.

When the pressure in the receiver tank begins to fall the valve will remain open until the pressure on the valve dll is no longer sufcient to overcome the compressive force exerted by the spring 41|.`

` The pressure required to hold the valve open is considerably less than the pressure required to open the valve. This will be readily apparent when it'is noted that the effective pressure area.

is increased to the total diametrical area of the 20 valve 4| l, as was pointed out in the description of valve 4| in the auxiliary valve 36. Upon the closing of the valve 41|, shutting off the flow vof fluid under pressure from the receiver to the move from its left-hand position back to the normal unactuated chamber. This is due to the fact that uid under pressure remains in the chamber when the valve 4H closes and, accordingly an escape for the uid 30 in the chamber is provided, similar-to the escape provided with the unloading and-reloading device 36.

The path for the quently, through the |21, past the seat 5| i, through the channel 51|, to the atmosphere. With this arrangement the piston chamber is normally open to atmospheric pressure and it is only when the predetermined high pressure occurs iluid is admitted therefrom to the piston chamber, and at that time the atmospheric vent is closed by the valve 4H as it rests on the seat 5| l.

In the operation of the entire regulating means escape of `uid is, consethe predetermined high presure at which the aux- 45 iliary valve |3l opens is slightly less than the maximum allowable pressure at which the auxiliary valve 35 opens. For example, the valve 13B may open at 100 pounds per square inch and the valve 36 at 105 pounds per square inch. The 50 regulation of these pressures, of course, depends may vary the compressive force of the springs 4l or Ml in the manner described. As the opening pressures for the respective valves are different, in accordance `with this invention the corresponding closing pressures are adjusted to be different. Thus the corresponding closing predetermined low pressure for the auxiliary valve 3B may be 85 pounds per square inch, whereas the corresponding closing, 6G ,or predetermined minimum, pressure for the auxiliary valve |3| may be`80 pounds per square inch. In general the operation oi the unit is as follows: When the machine is started, assuming no pressure at the receiver, both oi the auxiliary valves 3E and |.3I are closed leaving the unloader valve 2| in its open position and the piston H3 in its right-hand position, corresponding to the vmaximum speed setting of the motor governor.

When the pressure builds up to the pounds 70 per square inch, the valve Ml opens, the piston H3 movesto its left-hand position and changes the governor speed setting to the minimum speed.

If the load is constanh'thecompressor will then operate to supply vthe necessary require- 75 does not immediately 25 position at the right of the slots |29, into the conduit 35 in the receiver tant. that 40` -pounds per square inch, the valve ments at the minimum speed of the motor. It the pressure should continue to build up in the receiver to the maximum allowable pressure, 105 pounds per square inch, the valve 4| operates to close the unloading valve 2| and thereby prevents further discharge of air to the receiver. It the load now increases, the pressure in the receiver tank will fall and when itl reaches 85 y4I the unloading valve 2| opens again permitting the discharge of air from the compressor to the receiver. So long as the load does not increase to the point where the pressure in the receiver tank falls to 80 pounds per square inch, the valve 4H remains open and the machine will continue to operate at minimum speed. Should the load increase, however, and the pressure fall to the minimum allowable pressure of pounds per square inch, the valve 4H will close, permitting the fluid in the chamber III to escape to atmosphere and the piston tomove to its righthand position thus causing the motor again to accelerate to its maximum speed.

It is thus apparent that during the operation of the compressor the regulating means will oper ate to maintain the motor running at minimum speed so long as the load does not require the motor to run at maximum speed, and the cycle of operation will be similar to that described.

It is understood that the described is a preferred embodiment of the invention and that many changes which do not depart from the'scope and spirit of the invention will occur to those skilled inthe art.

I claim:

1. In a regulator for a motor driven fluid compressor having a speed governor, a compressor discharge controlled pressure responsive .device for controlling the speed setting of the governor having two control positions, means to unload the compressor at a predetermined maximum discharge pressure and to reload the compressor at a predetermined low discharge pressure, and means responsive to a predetermined high discharge pressure intermediate the maximum and low discharge pressures to enable the discharge pressure to set and maintain. the pressure responsive device in one control position 'until a predeterminedminimum discharge pressure less than said low discharge pressure is reached.

2. In a regulator for a motor driven luid compressor having a fluid receiver tank and a speed governor, a pressure device for controlling the speed setting of the governor actuated by .the fluid pressure in the receiver tank, means to unload the com pressor ,at a predetermined maximum pressure in the receiver-tank and to reload th compressor at a predetermined low pressure in the receiver tank, means responsive to a predetermined high pressure intermediate the maximum and low pressures in the receiver tank to admit fluid therefrom to the pressure device and responsive to a predetermined minimum pressure less than the low pressure in the receiver tank to prevent admission of fluid therefrom to the pressure device, and means to regulate the predetermined high and predetermined minimum pressures. f

3. 1n a regulator for a motor driven iluid compressor having a iluid receiver tank and a speed governor, a pressure operated device for controlling the speed setting of the governor in accordance with the fluid pressure in the receiver tank having a maximum speed setting position and a minimum speed setting position, means to uncloses and construction i above mediate said maximum load the compressor at a predetermined maximum pressure in the receiver tank and to reload the compressor at a predetermined low pressure in the receiver tank, means normally preventing admission of iluid from` the receiver tank tothe pressure responsive device to enable said pressure responsive device to remain at its maximum speed setting position and adapted to admit fluid to said pressure responsive device when a predetermined high pressure intermediate the predetermined maximum and low pressures is reached until a predetermined minimum pressure less than the predetermined low pressure is reachedv to change said pressure responsive device to and maintain it at the minimum speed setting position.

4. In a regulator for amotor driven fluid compressor adapted to discharge fluid under pressure to a receiving means and having a speed control governor, means to unload the compressor at a predetermined maximum discharge pressure and to reload the compressor at a predetermined low discharge pressure, pressure means in communication with the receiving means to control the speed setting of the governor, and means normally preventing communication between said pressure means and the receiving means adapted to permit communication with the pressure in the receiving means is within a predetermined range after a predetermined high pressure interand low pressures has been reached.

5. A regulator for a motor driven fluid compressor having a governor, a pressure responsive device for controlling the speedsetting of the governor in accordance with variations in the discharge pressure of the compressor having two control positions, means to unload the compressor at a predetermined maximum pressure and to reload the compressor at`a predetermined low discharge pressure,v adjustable means to predetermine the discharge pressures atwhich the last said means operates, meansl to render the pressure responsive device operative to assume onel control position at a' predetermined high pressure intermediate said pressures and to assume the other control position when a predetermined minimum pressure less than said low pressure is reached. and ad- `iustable means to regulate the pressures at which the last said means operates.'

6. A regulator for a motor driven iluid compressor having a governor, a pressure responsive device for controlling the speed setting of the governor in accordance with variations in the discharge pressure of the compressor having two pressure and to reload the compressor at a pre' determined lowl discharge pressure, adjustable means to` predetermine the pressure at which the last said means operates, and means to render the pressure responsive device operative torassume one control position at a predetermined high discharge pressure intermediate said predetermined maximum and predetermined low discharge pressures and to assume the other control position at a predetermined minimum discharge pressure less than said predetermined low dischargeipressure, means to predetermine the pressures at which the last said means operates, and means associated with the last said means to normally subject the pressure responsive device to atmospheric pressure.

7. A regulator for a motor driven iuid compressor having a governor, a pressure responsive device for controlling the speed setting of the governor in accordance with variations in the discharge pressure of the compressor having a maximum speed setting position and a minimum speed setting position and normally maintaining the governor at maximum speed setting, means to unload the compressor at a predetermined maximum discharge pressure and to reload the compressor at a predetermined low discharge pressure, means to render the pressure responsive device operative to change the governor to the minimum speed setting at a predetermined high pressure intermediate said predetermined maximum and low discharge pressures and maintaining that speed setting within a predetermined lower range of discharge pressures, and means associated with the last said means to subject the pressure responsive device to atmospheric zo pressure when the discharge pressure is outside pressure and means said predetermined range.-

8. A regulator for a motor driven uid compressor having a speed governor comprising a pressure responsive device for controlling the speed of the governor in accordance with variations in the discharge pressure of the compressor having a maximum speed setting position and a minimum speed setting position, means to normally maintain the governor at a maximum speed setting, means to unload the compressor at aV maximum discharge pressure and to reload the compressor at a predetermined low discharge pressure, means to render the pressure responsive device operative at a predetermined high pressure intermediate said maximum and W discharge pressures to cause the governor to adjust and maintain the motor speed at a minimum and to render the pressure responsive device inoperative-to cause the governor to accelerate the speed of the motor Ato' a maximum when a predetermined minimum rdischarge pressure less than said low discharge pressure is reached.

9. A regulator for a motor driven duid compressor having a governor comprising a pressure responsive device actuated in accordance with variations in the discharge pressure of the compressor normally positioned to maintain the governor at the maximum speed setting and having a minimum speed setting position, means to unload the compressor at a predetermined maximum discharge pressor at a predetermined low discharge pressure, means responsive to a predetermined high discharge pressure intermediate said predetermined maximum and predetermined lovv -discharge pressures to render said pressure responsive device operative to move to its minimum speedf setting position thereby changing the governor to its minimum speed setting.

l0. In a governor speed regulator for a motor driven uid compressor, a pressure responsive device having maximum and minimum speed setting positions for controlling the governor in accordance With variations in the discharge pressure of the compressor, means to unload the compressorat a predetermined maximum discharge to reload the compressor at a predetermined low discharge pressure, and means normally maintaining the pressure responsive device in the maximuml speed setting position' until a predetermined high pressure. intermediate said predetermined maximum and low ydischarge pressures is reached. i

11. In a governor speed regulator for a motor driven uid compressor, a pressure responsive to reload the compressor at pressure and to reload the comdevice having a maximum speed setting position and a minimum speed setting position for con- `trolling the governor in accordance yvvith variations in the discharge pressure of the compressor, means to unload the compressor at a predetermined maximum discharge pressure and means to reload the compressor at a predetermined low discharge pressure, means responsive to the discharge pressure of the compressor normally preventing movement of the pressure responsive device from its maximum speed setting position to efiect movement of the pressure responsivedevice to its minimum speed setting position when a predetermined high -pressure intermediate said predetermined maximum and predetermined low discharge pressures is reached, and means to predetermine said high pressure.

l2. In a governor speed regulator for a motor driven uid compressor having a receiver tank, means to unload the compressor at a predetermined maximum discharge pressure and means a predetermined low discharge pressure, a casing containing a chamber, a piston in the chamber, a spring normally preventing movement of the piston, a series oi interconnected levers for transmittingmovement of the piston to the governor, a second'casing having a chamber communicating with the receiver tank, a conduit connecting the two casings, a piston in the second chamber, a piston seat in the chamber, a spring normally holding the piston against the seat to prevent communication between the receiver and the rst chamber, meansto adjust the tension on the spring whereby the piston in the second chamber may be moved from its seat by a predetermined high pressure intermediate said predetermined maximum and low discharge pressures in the receiver to permit the pressure in the receiver to move the piston in the first said chamber against the tension of its spring and to reseat upon occurrence of a predetermined minimum pressure less than said predetermined low pressure in the receiver, means to vent the nrst chamber through the second chamber when its piston is seated, and means to prevent Aventing when the piston is unseated.

13. In a regulator for a motor driven iiuid compressor having a speed. governing means, compressor discharge pressure actuated control means for the speed governing means receiving iiuid discharged by the compressor, means to unload and reload the compressor in accordance with variations in the compressor discharge presy sure, and means to prevent the pressure actuated control means from receiving compressor discharge nuid until the compressor discharge uuid pressure rea-ches a predetermined pressure less than the compressor unloading pressure.

14. In a regulator for a motor driven :duid compressor having a speedv governor and a receiver'V tank comprising means to unload the compressor at a predetermined max' um discharge. pressure and to reload the compressor at a predetermined low discharge pressure, and a pressure responsive device having a maximum speed setting position and a minimum speed` setting position comprisingr means deiining a chamber communicating with-the receiver, a piston in the chamber, means to transmit movement of the piston to the governor, a spring to normally maintain the piston in the maximum speed setting position, means normally preventing communication between the receiver and chamber adapted to permit communication when the pressure in the receiver reaches a` predetermined high pressure and '..ntilr 15..In a regulator for a motor driven iluid compressor having a governor and a receiver tank including means to unload the compressor 'eating with the receiver, pressure responsive means in the chamber, means to transmit movement ot the premure responsive device to the governor, means to normally maintainfthe pressure responsive device in its maximum speed setting position, means normally preventing communication between the receiver and chamber adapted to permit communication within a predetermined preure mined high discharge pressure less than the predetermined maximum discharge pressure has been reached. and means to predetermine said 1' ange.

ALLAN' O. CARPENTER.

range after a predeter-