US2166789A - Compressor regulator - Google Patents

Description

July 18, 1939.

Filed May 12, 19:53

C. S. BAKER COMPRESSOR REGULATOR 2 Shee tS-Sheet 1 INVENTOR dam-1w dffiakea HIS ATTORNEY July 18, 1939. c, s, BAKER 2,166,789

' QOMPRESSOR REGULATOR 7 Filed May 12, 1938 2 Sheets-Sheet 2 5 INVENi-QR 1 v I 1.91 J V I His ATTORNEY Patented July 18, 1939 COMPRESSOR REGULATOR Charles S. Baker, Corning, N. Y., assignor to Ingersoll-Rand Company. Jersey City, N. J., a corporation of New Jersey Application May 12, 1938, Serial No. 207,438

20 Claims.

This invention relates to motor driven fluid compressor units and more particularly to apparatus to control the speed of the motor in accordance with changes in the discharge pressure of the compressor and to maintain the motor at a minimum speed for a predetermined time after the compressor has been Iullyloaded and the output of the compressor requires the maximum speed of the motor. 7

An ordinary portable motor driven fluid compressor unit comprises a motor or engine such as internal'combustlon motor or steam engine di rectly connected to drive a fluid compressorgwhich delivers fluid to a receiver tank wherein it is stored until needed. Such compressor units are commonly provided with regulator means to prevent overloading of the receiver tank when the pressure of the fluid in the receiver tank reaches a predetermined value. Upon reaching this predetermined pressure, the regulator operates to prevent a further discharge of fluid to the receiver from the compressor.(commonly termed unloading) and at the same time reduces the speed of the motor to a minimum or idling speed. g Thereafter the compressor unit idles until the pressure in the receiver tank decreases to a predetermined minimum pressure whereupon the regulator again operates to permit the compressor to discharge fluid to the receiver tank (commonly termed reloading) and to accelerate the motor to its maximum operating speed.

The chief disadvantage attending the use of such regulating means is that pressure in the receiver tank drops to predetermined minimum pressure, the compressor reloads and simultaneously therewith the motor speeds up to its maximum speed regardless of how great the demand upon the compressor may be. The speeding up of the motor to its maximum speed not only causes a great wear and tear on the motor but in many instances is entirely superfluous because an intermediate speed would be sufilcient to supply the compressed fluid required by the load under which the compressor is operating. Naturally, the result is very uneconomioal operation.

It is accordingly an object of the present invention to provide a compressor unit with means whereby the compressor may reload when the load is light without simultaneously accelerating the motor to the maximum speed. 1

Another object of the invention is to provide means whereby a motor driven fluid compressor unit may operate at its minimum speed without reloading.

65 A still further object is to provide means whereby the compressor unit may accelerate to and run at speed between minimum and maximum in order to maintain corresponding rates of discharge of fluid into the receiver.

A further object is to provide means in a com- 6 pressor unit whereby the motor speed may be held at a minimum-speed during unloading and reloading of the compressor.

It is a further object to provide means in a compressor unit whereby, under ordinary unloading and reloading, the motor is not permitted to accelerate toward the maximum speed for a predetermined time after predetermined minimum pressure 'occfifsin the receiver.

Still another object is to provide a device which will delay acceleration of the driving motor after reloading to accommodate a light load at low motor speed and somewhat later to permit acceleration of the motor when reloading occurs under a heavy load.

These and other objects will be readily apparent from the following description of which the drawings form a part. In the drawings in which similar reference numerals refer to similar parts,

Figure 1 is a view partially in elevation and partially in section illustrating the application of the present invention to a compressor unit and in which the governor is increased in size in order that the details may be brought out more clearly.

Figure 2 is a view in sectional elevation of the governor regulating portion of the regulator constructed in accordance with the principles of the present invention and shown in Fig. 1.

Figure 3 is a sectional view of the unloading device illustrated in Fig. 1.

Figure 4 shows a sectional view of the governor illustrated in Fig. 1.

A portable motor driven fluid compressor unit is shown in Fig. l and comprises a fluid compressor I, mounted on a frame 3, supported by wheels 5, driven by a motor i, and supplied with the fluid to be compressed through the inlet pipe 9. Thecompressor delivers the compressed fluid to the receiver tank ll through a conduit i3. Interposed between the inlet conduit 9 and the compressor l is the unloading and reloading device l5 shown in detail in Fig, 3 which will be described hereinafter.

Speed regulation of the motor I, is accom- 5o plished by the governor generally indicated at l1. The governor, illustrated in detail in Fig. 4, consists of a shaft l9, directly connected to the cam shaft of the motor (not shown), having an extension 2]., A gear 23, having weights 21 fulcrumed at 29 thereon, is bolted to the flange 25 formed on the shaft I9.

As the speed of the motor increases, the centrifugal force moves the weights 21 toward their outermost position and in so doing the rollers 3|,

mounted on the lever supporting the weight 21,

bear against the plate 33. Recess 35 provided on plate 33 surrounds the shaft extension 2| and guides the plate as it slides on the extension 2|. The motion of the plate 33 is transmitted through the anti-friction bearing 39 to a plate 4| formed integrally with the pin 43 slidably mounted in the shaft extension 2| and co-axial therewith.

The clevis 45 mounted on the plate 4| is pinned to the lever 41 (shown in Fig. 1) fulcrumed on the frame of the motor at 49. At the end of the lever 41 opposite to the clevis 45, is a tie-rod 5| to control the butterfly valve 53 in the intake of the motor and since outward movement of the weights 21 tends to pivot the lever 41 about its fulcrum 49 to move the tie-rodto the left, the

consequent movement .of the butterfly valve 53.

will throttle the fuel supply to the motor and decelerate the motor.

Conversely, when the motor speed is to be increased, the weights 21 will move toward their innermost position and the 'lever 41 and tie-rod 5| will then move the butterfly valve 53 to its open position and thereby increase the fuel supply to the motor to accelerate the motor.

As is customary in centrifugal governors, the weights 21 are resiliently maintained in their retracted position and for this purpose a spring 31 is provided. The compressive force of the spring 31 is transmitted to the weights 21 through the lever 41 by the member 51 hearing against one end of the spring 31 and the projection 55 formed on the lever 41' between the tie-rod end and the fulcrum 49.

In order to inclose the spring 31, a casing 59 having a bore 9| extending therethrough and communicating at one end with the recess 93 is secured to the frame of the motor 1. As was pointed out, one end of the spring 31 bears against the member 51, and the opposite end bears against a similar member 65. The degree of compression of the spring is, of course, controlled by the position of the members 51 and 95 and since the member 51 bears against projection 55, regulation of the compression of the spring 31 can be accomplished by the movement of the member 95. For this purpose. a guide member 61 extends through the bore 6|, into the recess 63, and into a recess formed in the member 65. A plunger pin 69 is guided by the guide member 61 and bears directly against the member 65. When the spring 31 is compressed by movement of the plunger pin 99 against the member 95. it is obvious that the centrifugal force set up by the weights 21 required to move the lever 41 against the compression of the spring 31 is much greater than when the spring 31 is in its released or uncompressed position. It is also apparent that the degree of compression on the spring by which the speed setting of the governor is determined may be controlled by regulating the position of the plunger pin 99 and for this purpose the regulating mechanism shown in Fig. 2 is employed.

This regulator consists of a casing 1|, suitably secured to the motor' frame by bolts 13, provided with a bellows chamber 19, closed by a head 8| secured to the casing. The interior of the bellows chamber communicates directly with the atmosphere through the opening 33 in which is threadedly secured a bushing 35 having an orifice 31 to restrict the flow of fluid passing through the bushing.

Extending through a suitable opening in the head 8|, into the bellows chamber 19, and secured within the chamber to a piston 9| is a plunger rod 99. .Bellows member 93 hermetically sealed to the piston 9| at one end between the casing 1| and the head 8|, at the other end controls movement of the plunger rod 39. With this arrangement the passage of fluid from the bellows chamber 19 to the interior of the bellows 93 is impossible, but communication with atmosphere is provided by the opening surrounding the plunger 89 in the head 8|. For the purpose of transmitting movement between the bellows 93 and the plunger pin 59, a lever 95 is pivotally connected to the plunger rod 89 by a pin 99. Since it is often desirable to regulate the degree of com pression of the governor spring 31 which the bellows 93 can affect, a bolt IIlI' threadedly engages the end of the lever 95 and bears against the plunger pin 69. A nut I93 serves to lock the bolt IIlI in position.

Similarly, it is often advantageous to control the degree of compression of the bellows 93 and consequently the movement of the plunger 89. To this end the head 8| carries a bracket I95 through which is threaded a bolt I91 suitably locked in position by the lock nut I09. The limit of expansion of the bellows 93 may be adjusted by the position of the bolt III secured on the opposite end of the ,lever 95 and locked in position by the 'locknut II3. By this present arrangement, it is therefore possible to regulate the compression limits of the governor spring 31 by adjustment of any one of the three bolts IIlI, I91, and III under certain conditions, or by adjustment of all of the bolts under other conditions.

In the upper part of the casing 1| is an opening 5 in which rests a valve bushing II1. This valve bushing 1 has an orifice II9 into which extends a needle valve I2I. The needle valve |2I is normally pushed into the orifice I 9 by a spring I23, bearing at one end againt a flange I25 on the needle valve I2I and at the other end against a washer I21 held in the valve bushing II1 by the ring I 29. The valve bushing extends into a recess I3| formed in the upper part of the casing 1| and permits communication between this recess and the chamber 19 when the needle valve is not maintained at its seating position. Pressure fluid from the receiver tank is supplied to the recess |3| through the opening I33 by the conduit I35 leading directly to the receiver tank.

In order to form a closed chamber of the recess I3I, a diaphragm I31 is interposed between.

the walls of the casing 19. This diaphragm I31 also serves to deflne'one end of a second chamber I39. Centrally located in the diaphragm is a contact member I which bears against the end of the needle valve- IZI. It is desirable for the operation of this apparatus that the contact member normally be brought to bear on the end of the needle valve and for this reason the spring I43 is placed in the chamber I39. The regulation of the degree of spring compression is accomplished by the bushing member I43 longitudinally movable by the stem I41 and maintained in position by the nut I49.

By the means of this arrangement of parts. when the fluid pressure in the receiver tank is sumciently great to move the diaphragm I31 wainst the force of spring I 43, the contact member I will move upwardly thus permitting the spring I33 to move the needle valve Ill into its seating position to close the orifice H9 and thus prevent entrance of fluid from the receiver tank to the bellows chamber 19. Conversely, when the receiver tank pressure falls'to a'prssure which is insuflicient to permit the diaphragm I31 to overcome the compression of the spring I 43, the contact member IlI will move the needle valve I2I from its seating position, by overcoming the resistance of the spring I23, and thus permitting fluid to enter the bellows chamber 19. When fluid enters the bellows chamber-19, if its pressure is sufllcient, it will tend to move the bellows 93 toward the left; otherwise the pressure of the fluid within the bellows 93, the escape of fluid through orifice 91, and the compressive force of the governor spring 31 are all factors tending to maintain the bellows 93 stationary.

Needle valve III is tapered so that its position with respect to its seat I I9 determines the amount or fluid admitted from chamber I3I to chamber 19. Inasmuch as orifice 91 provides a fixed resistance to escape of fluid from chamber 19, valve I2I meters the flow of fluid to and pressure in chamber 19 in accordance with receiver pressures at II but in greatly exaggerated degree. Accordingly, the pressure exerted by bellows 9I upon governor spring 31 varies with such receiver pressure. Thus, when the compressor unit is started, the pressure of the fluid in the receiver is insumcient to move the diaphragm I31 and, consequently, the spring I43 maintains the needle valve I2I- open thereby admitting fluid from the receiver tank to the bellows chamber. The pressure of the fluid in the bellows chamber 19 will be relieved through the oriflce 81 under ordinary conditions but as soon as the pressure hegins to increase to the point where the orifice 81 is insufllcient in size to relieve the pressure of the fluid entering the chamber 19 pressure will act to compress the bellows. As the bellows is compressed, the governor spring 31 will also be compressed as was previously explained. When a pressure suihclent to compress the bellows 93 and hold the plunger rod 39 against the stop m1 is reached, the governor spring will be compressed ta its utmost limit and, consequently, the motor will operate at its maximum speed. As the pressure in the receiver tank II increases during the operation of the motor at maximum speed, the

pressure acting on the diaphragm I31 will likewise be increased and tend to move the diaphragm 931? to close the needle valve HI and .iurther restrict the flow of fluid to the bellows chamber. With the needle valve closed, the pressure remaining in the bellows chamber 19, will escape through the oriflce 81 and the bellows 93 will expand under the influence oi the governor spring 31. Under such conditions the governor spring 3?, being fully expanded, permits the motor to operate at its minimum speed.

If the load on the compressor shouldincrease to decrease the receiver pressure, the needle valve I will again be opened and the same cycle of operation will occur to bring the motor speed to the maximum speed. After such a load change it is desirable to operate the motor at its minimum speed for a predetermined time without increasing the speed of the motor to its maximum speed. Therefore, in order to provide a suitable time delay the casing H is provided with an opening I5I in the wall of the chamber I39, which opens into the recess I63. A check valve I65 is placed in the recess I63 and covers the opening I5I when it is seated. The check valve is normally maintained on its seat I61 by a spring I59 which is maintained in the recess I63 by the plug I6 I. The plug I6I is threaded to receive the conduit I63 communicating directly with the compressor inlet manifold. In this manner the recess I53 is maintained at the same pressure as the, compressor inlet manifold and since the check valve is provided with an orifice I66 communicating with the opening ISI the chamber I39 is also subjected to the same pressure;

To ensure economical operation of the above described regulating apparatus, it is important that some means of unloading and reloading the compressor be supplied and for that reason the unloader shown in Fig. 3 will now be described. This unloader, generally indicated at I 5, consists of a casing I15 placed at the inlet of the compressor I and connected with the inlet conduit 9. A portion of the casing-I15 extends within the outer Walls thereof to form valve guides I11 for the balanced unloading valve I19 reciprocal within the casing. To one side of the casing is an opening I8I closed by a plate I93 provided with a recess I in which one end of the spring I81 rests. The opposite end of the spring I91 bears against thevalve I19 to maintain this valve normally in its open position as indicated in Fig. 3. With the valve in this position fluid may enter from the conduit 9, pass around the valve I19 into the passage I9I leading directly to the compressor. As long as valve I 19 is open, passage I9I is subjected to atmospheric pressure but upon closing the valve the pressure is reduced to a vacuum.

Opposite the opening I8I is another opening I95'in the casing wall in which is secured a piston chamber I93 having a surface I96 which serves as a stop for the valve I19 when it is in its open position. For the purpose of moving the valve the piston I91, in slidable engagement with the cylindrical wall I98 of the piston chamber, is provided and is adapted to transmit its motion to the valve I19 by bearing against the shaft i99 which is formed as an integral part of the valve.

1 Since the unloading and reloading of the compressor depends on the pressure in the receiver a.

tank, the piston is arranged to be actuated by the pressure of the fluid in the receiver tank.

Means for regulating the admission cf fluid from the receiver tank to the piston chamber is provided and to that end an auxiliary valve is formed as a part of the unloading device. This auxiliary valve consists of an auxiliary valve body 29H closing the open end or" the piston chamber I98 and communicating with the interior of the chamber through the passage 263. The conduit 2% supplies fluid from the receiver tank to the interior 'of the auxiliary valve body. Within the casing 20I is a reciprocatory auxiliary valve proper 201 normally maintained on an upper seat 209 by the spring 2 toprevent the entrance of fluid from conduit 205 to the piston chamber I98. Member 2) provided with a head 2| 3 interposed between one end of the spring 2H and a recess formed in the valve proper 291 forms a guide for the spring and manual means for opening the valve. The bushing 2I5 forms the other limiting abutment for the spring 2| I and is secured in a second bushing 2I1 threadedly engaging the auxiliary valve chamber 20L This second bushing 2" provides an adjustable seat 2I9 against which the valve 201 bears when the pressure in the receiver tank is suflicient to-move the valve against pressure of the spring 2. The pressure of the spring 2 isregulated by, threadedbushing 2I5 and determines the receiver pressure at which the valve is to open.

A vent 2I3 is formed by the member 2IlI and the bushing 2I5 and serves to relieve the pressure in the auxiliary valve chamber and the piston chamber when the auxiliary valve proper 201 is seated on its seat 209. If, while the compressor is operating, the fluid pressure in the receiver tank II increases sufficiently to move the auxiliary valve proper 201 from its seat 203 and to maintain it on the adjustable seat 2I8, the fluid pressure will pass through the passage 203 into the piston chamber and cause the pisv and any air existing in the piston chamber will escape through the passage 203 and the vent 2I8 to the atmosphere. In such an event the compressor will be fully loaded since the entrance of air is not prevented by the valve I13 and the inlet manifold I9I will again be subjected to atmospheric pressure.

The operation of the invention as described above is as follows:

During the period when the compressor unit is being brought into operation obviously no change is desired and accordingly the regulating apparatus above referred to functions only when the compressor unit is operating under normal load conditions. Accordingly, while the compressor unit is operating under load and the pressure-in the receiver tank II is low, the diaphragm I31 holds valve I25 open permitting fluid under pressure to enter bellows chamber 19 and to compress bellows 93. The compression of the bellows 93 is transmitted to the governor spring 31 as was previously described and the speed of the motor is, therefore, dependent on I the degree of compression of the bellows 93.

With valve I25 in its openmost position the pressure in bellows chamber 19 will be sufllcient to cause bellows 33 to hold governor spring 31 fully compressed and allow the motor to operate at its maximum allowable speed. 80 long as the pressure in the receiver tank II does not rise, the motor will function at its maximum speed thus automatlcally providing the correct motor speed for a heavy load.

With a rise in pressure in the receiver tank II, however, the diaphragm I31, being subject to receive pressure, will move upwardly in direct accordance with the degree of pressure. Upward movement of the diaphragm 31 permits the tapered needle valve I25 to move upwardly a corresponding amount and begin metering or restricting the fluid entering bellows chamber 19. Inasmuch as the diaphragm I31 controls the needle valve I25, the degree of metering is dependent on the pressure in the receiver tank 'I I. The eifect of metering the fluid entering the chamber 13 is to reduce the amount of fluid entering that chamber and since the orifice 31 continually vents the chamber, the pressure acting on bellows 33 varies inversely with the pressure oi the fluid in the receiver tank II but in a greater degree. Consequently, as the receiver pressure increases, the bellows 33 will re-exp'and under the influence of governor spring 31. As

II the compressive force on the governor spring 31 is reduced the motor is decelerated. Full expansion of governor spring 31 and bellows 93 permitting deceleration of the motor speed to the minimum speed occurs only when the pressure in the receiver tank has reached a high pressure of predetermined value. In accordance with this invention, so long as the compressor unit remains loaded, the motor speed is arranged to 'fluctuate in accordance with fluctuations in the load on the unit as evidenced by the compressor discharge pressure or pressure in the receiver tank II.

The receiver pressure at which the motor speed is reduced to a minimum is determined by the method in which it is desired to operate the unit. If the motor is to operate at minimum speed only when the compressor is completely unloaded, the compression of spring I43 is so regulated that the diaphragm I31 is unable to permit needle valve I25 to assume the metering position corresponding to the minimum speed of the motor until the maximum receiver pressure is reached. However, at the maximum pressure the diaphragm I31 is not moved to its minimum speed position by the pressure of the fluid supplied by conduit I3I. Instead, this movement is brought about in the following manner:

Upon the occurrence of the maximum permissible pressure in the receive tank II the device I unloads the compressor I and induces a vacuum in the compressor inlet manifold ISI, as was pointed out hereinbefore. At the same time, the vacuum is set up in conduit I63 which moves check valve I55 against spring I59 toopen port I5I wide and quickly subject recess I39 to the vacuum. The effect of the vacuum is to almost instantaneously snap' the diaphragm I31 to its uppermost position thereby closing needle valve I25 and, as above described, causing the motor 1 to operate at its idling speed. The vacuum serves also to lock the diaphragm in its uppermost position and to provide a time delay as will be explained. I

In some instances it may be preferable to operate the motor at its minimum speed at pressures below the maximum allowable discharge pressure in order that the compressor need not necessarlly be unloaded before the motor may decelerate to its idling speed. To achieve this purpose the spring I43 is adjusted to allow a predetermined high discharge pressure acting on diaphragm I31 to move the diaphragm and the needle valve I25 to positions where bellows 93 will expand and allow the governor spring 31 to assume its minimum motor speed position. The device I5, however, is still adjusted to unload the compressor I when the maximum allowable discharge or receiver pressure is attained.

The eflect of such an adjustment is to cause the, motor speed to reduce to the minimum speed when a predetermined high discharge pressure is reached. Variation of the discharge pressure above the predetermined high pressure without reaching the predetermined maximum pressure does not aifect the minimum speed setting of the governor but. if the pressure fluctuates below the predetermined high discharge pressure, the speed of the motor will vary since that variations in receiver pressure aflect diaphragm I 31 and consequently needle valve I25 controlling the flow of fluid to bellows chamber 19. Such variations will cease as soon as the receiver pressure rises to the maximum permissible discharge pressure since the device I5 then acts to unload the compressor I and induce a vacuum in chamber I38.

Again the diaphragm I31 will snap to its uppermost position and remain locked there to prevent further variation of the motor speed from the minimum.

Regardless of which of these methods of operating the unit is used,'whenever the maximum discharge pressure is reached the motor is maintained at its minimum speed. Thereafter, upon a drop in pressure from the predetermined maximum pressure the compressor I remains unloaded and the motor speed at a minimum until a predetermined minimum pressure occurs in the receiver tank. With proper adjustment of spring 2 I I, in the auxiliary valve body I, the valve 201 will close and permit the cylindrical valve I19 to open and reload the compressor I when this predetermined minimum pressure occurs. Were it not for the check valve I55 and its restricting orifice I65 which causes a time delay, the motor speed, under control of the governor regulating apparatus, would almost immediately jump to a maximum.

As the compressor I is reloaded by the opening of the valve I19 the compressor manifold I9I is subjected to atmospheric .pressure. The conduit I63 conveys fluid at this pressure to the check valve I55 which, under the combined force of spring I59 and atmospheric pressure, returns to its seat I51. While the check valve I55 is so maintained on its seat, fluid at atmospheric pressure can enter chamber I39 only through the orifice I55. The pressure in chamber I39 accordingly will gradually approach atmospheric pressure after the compressor I has been reloaded but, naturally, there will be a certain time delay before the chamber will be at atmospheric pressure and the diaphragm I31 free to move under the influence of the pressure in the receiver tank II. The duration of the delay is predetermined by the size of the orifice I65 and, by variation of the size, any desired delay may be secured.

Thereafter the apparatus functions as though no time delay had occurred and the motor varies its speed as required to conform with the load on the compressor.

As an illustration of the manner in which the compressor unit will function when the minimum speed and unloading pressure are reached at the same instant, let it be assumed that the compressor motor I is to operate at maximum speed when the pressure in the receiver tank reaches 80 pounds per square inch and at a minimum speed when the pressure is at 105 pounds per square inch. Furthermore, that the compressor is to be unloaded at a pressure of 105 pounds per square inch and is to be reloaded at 80 pounds per square inch. Upon operation of the compressor, as the pressure gradually increases from 80 pounds per square inch toward, but does not reach, 105 pounds per square inch, the motor speed gradually decelerates from the maximum toward the minimum motor speed. If, then, the pressure remains constant or decreases gradually, the motor will respectively either remain at constant speed or accelerate gradually in order that the motor speed will be just suflicient to carry the loader: the compressor. Should the pressure in the receiver tank reach 105 pounds per square inch, the loading device I5 will function and unload the compressor and, at the same time, the motor will assume its idling speed.

Leakage or the load on the receiver will reduce the pressure in the receiver tank I I and when it reaches 80 pounds per square inch, the compressor is reloaded by the loading device I5.

During this time the compressor motor is operating at its idling speed. Upon reloading, after a predetermined time delay as explained hereinbefore, the motor is permitted to accelerate rather slowly toward its maximum speed. The cycle of operation will thereafter repeat itself.

Under the alternate method of operation above referred to, the only difference is that the motor is adjusted to operate at minimum speed when the discharge pressure is at 100 pounds per square inch for instance, whereas, the unloading pressure of the compressor is at 105 pounds per square inch. A pressure of 100 pounds will therefore cause the motor to assume its minimum speed but so long as the pressure does not reach 100 pounds per square inch the speed of the motor may vary with the receiver pressure increasing or decreasing between maximum and minimum speeds and in the range between 100 and 105 pounds the motor speed stays at a minimum. If the pressure becomes 105 pounds per square inch, the compressor will unload and, as was previously explained, lock the motor speed at the idling speed. In other respects the function of the compressor unit, under this method, is identical with the first method disclosed.

It is to be understood that the construction above 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 in the art.

I claim:

1. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded, means to unload the compressor at a predetermined pressure and to reload the compressor at a predetermined minimum discharge pressure, means to lock said pressure responsive device at said predetermined discharge pressure of the compressor until said predetermined minimum discharge pressure is reached, and means to prevent variation of the governor speed setting by the pressure responsive device for a pre determined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded.

2. In a motor driven fluid compressor unit I having a motor speed governor, a pressure reting position when the discharge pressure is at and below a predetermined minimum discharge pressure and a minimum speed setting position when the discharge pressure is at and above a predetermined high discharge pressure, means to unload the compressor at a second predetermined high discharge pressure and to reload the compressor at said predetermined minimum discharge pressure of the compressor, means to lock said pressure responsive device at the minimum speed position, means to maintain the pressure responsive device at the minimum speed setting position for a predetermined time after the discharge pressure reaches said minimum discharge pressure and the compressor has been reloaded.

3. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position when the discharge pressure is at a predeter- I termined minimum discharge pressure is reached,

and means to prevent variation of the governor speed setting bythe pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded.

4. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the dis charge pressure 01' the compressor while the compressor is loaded having a maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure, means to unload'the compressor at a predetermined maximum discharge pressure andto reload the compressor at said predetermined minimum discharge, pressure, means to predetermine said maximum discharge pressure with respect to the last said means, and means to prevent variation of the governor speed setting by the pressure responsivedevice for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded.

5. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure, means to predetermine said high discharge pressure, means to unload the compressor at a predetermined maximum discharge pressure and to. reload the compressor at said predetermined minimum discharge pressure, and means to prevent variation of the governor speed setting by the pressure responsive device for apredetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded.

6. In a, motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting oi the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting positionat a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure comprising a chambered casing, pressure responsive means in a chamber of the casing, a shaft coacting with the pressure responsive means, means to connect the shaft with the governor, means to unload the compressor at a predetermined pressure at least as great as said predetermined highdischarge pressure.

and to reload the compressor at said predetermined minimum discharge pressure of the compressor, means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded comprising a valve in a second chamber of said chambered casing to control communication between said chambers, a conduit to admit pressure discharge fluid to the second casing, a diaphragm in the second chamber bearing on the valve and forming a third chamber, a spring to hold the diaphragm against the valve in the third chamber, a second conduit to admit fluid to and from the compressor intake from and to said third chamber, means to adjust the tension of the spring, and check venting means in the second conduit whereby the flow oi the fluid admitted to the third chamber is restricted to provide said time delays 7. In a motor driven fluid compressor unit having a motorjspeed governor, a pressure responsive device to control and vary the speed setting of the governor upon variations of the discharge pressure of the compressor while the compressor is loaded having a'maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure comprising a chambered casing, pressure responsive means in a chamber of the casing, a shaft co-acting with the pressure responsive means, means'to connect the shaft with the governor, and means to predetermine said high discharge pressure with respect to the pressure responsive device, meansto unload the compressor at a predetermined pressure at least as great as said predetermined high pressure and to reload the compressor at said predetermined minimum discharge pressure, means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded comprising a valve in a second chamber of said chambered casing to control communication between said chambers, a conduit to admitpressure discharge fluid to the second chamber, a diaphragm in the second chamber bearing on the valve and forming a third chamber, a spring to hold the diaphragm against the valve in the third chamber, a second conduit to admit fluid to and from the compressor intake from and to said third chamber, means to adjust the tension of the spring, and check venting meansinthe second conduit whereby the flow oi. the fluid admitted to the third chamber from the compressor intake is restricted to provide said time delay.

8. In a motordriven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at and below 'a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure comprising a chambered casing, pressure responsive means in the chamber of the casing, a shaft co-acting with the pressure responsive means, means to connect the shaftwith the governor, means to unload the compressor at a predetermined discharge pressure at least equal to said predetermined higher discharge pressure and to reload the'compressor at said predetermined minimumdischarge pressure, means to predetermine said high discharge pressure, means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded comprising a valve in a second chamber of said chambered casing to control communication between said chambers, a conduit to admit pressure discharge fluid to the second casing, a diaphragm in the second chamber bearing on the valve and forming a. third chamber, a spring to hold the diaphragm against the valve in the third chamber, a second conduit to admit fluid to and from the compressor intake from and to said third chamber, meansto adjust the tension of the spring, and check venting means in the second conduit whereby the flow of the fluid admitted to the compressor intake from the third chamber is restricted to provide said time delay.

9.- In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speedsetting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure comprising a chambered casing, pressure responsive means in the chamber of the casing, a shaft co-acting with the pressure responsive means, means to connect the shaft with the governor, means to predetermine said high discharge pressure, means to unload the compressor at a predetermined discharge pressure at least as great as said predetermined high discharge pressure and to reload the compressor at said predetermined minimum discharge pressure, means to predetermine said maximum discharge pressure with respect to the said varying means, means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded, comprising a valve in a second chamber of the casing to control communication between said chambers, a conduit to admit pressure discharge fluid to the second casing, a diaphragm in the second chamber bearing on the valve and forming a third chamber, a spring to hold the diaphragm against the valve in the third chamber, a second conduit to admit fluid to and from the compressor intake from and to said third chamber, means to adjust the tension of the spring, and check venting sure, means to unload the compressor at a predetermined discharge pressure at least as great as said predeterminedhigh discharge pressure and to reload the compressor at said predetermined minimum discharge pressure, and means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time ai'ter the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded.

11'. In a motor driven fluid compressor unit having a motor speed governor, a pressure re-- sponsive device to control and vary the speed setting ofv the governor'upon variation of the discharge pressure of the compressor while'the compressor is loaded having a maximum speed setting position at a predetermined minimum dis- 12; In a motor drivenfluid compressor unit having a motor speed governor, a pressure responsive device to control and vary the speed setting of the governor upon variation oi! the discharge pressure oi the compressor while the compressor is loaded having a maximum speed setting position at a predetermined discharge pressure and a minimum speed settin osition at a predetermined high discharge pressure, means to predetermine said high pressure, means to unload'the compressor at a predetermined discharge pressure at least as great as said predetermined high pressure and to reload the compressor at said predetermined minimum discharge pressure, means to predetermine said predetermined discharge pressure with respect to said unloading means, and means to prevent variation of the governor speed setting by the pressure responsive device for a predetermined time after the discharge pressure reaches said predetermined minimum discharge pressure and the compressor has been reloaded;

13. In a motor driven fluid compressor unit having a motor speed governor, means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loadedhaving a maximum speed setting position at a predetermined low discharge pressure and a minimum speed setting position at a predetermined high discharge pressure including pressure responsive means, means to conduct compressor discharge fluid to the pressure responsive means to actuate said pressure responsive means, and means to regulate the flow of discharge fluid to said pressure responsive means in accordance with variations in the pressure of the compressor discharge fluid and to prevent flow of fluid for a predetermined time after the pressure of the discharge fluid has reached said predetermined low pressure, and means to unload the compressor at a predetermined pressure at least as great as said predetermined high pressure and to reload the compressor at said predetermined low discharge pressure.

14. In a motor driven fluidcompressor unit having a motor speed governor, means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure including pressure responsive means, means to conduct compressor discharge fluid at the pressure responsive means to actuate said pressure responsive means, and means to regulate the flow of discharge fluid to said pressure responsive means in accordance with variations in the pressure of the compressor discharge fluid and to prevent flow of fluid for a predetermined time after the pressure of the discharge fluid has reached said predetermined minimum pressure, means to unload the compressor at a predetermined pressure at least equal to said predetermined high discharge pressure and to unload the compressor at said predetermined minimum discharge pressure, and means 'to predetermine the higher pressure with respect to said loading means.

15. In a motor driven fluid compressor unit having a motor speed governor, means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at a predetermined low discharge pressure and a minimum speed setting position at a predetermined high discharge pressure including means to predetermine said high discharge pressure, means to conduct compressor discharge fluid to the pressure responsive means to actuate said pressure responsive means, and means to regulate the flow of discharge fluid to said pressure responsive means in accordance with variations in the pressure of the compressor discharge fluid and to prevent flow of fluid for a predetermined time after the pressure of the discharge fluid has reached said predetermined minimum pressure, and means to unload the compressor at a predetermined pressure at least equivalent to said high pressure and to reload the compressor at said predetermined minimum discharge pressure.

16. In a motor driven fluid compressor unit having a motor speed governor, means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor having a maximum speed setting position at a predetermined minimum discharge pressure and a minimum speed setting position at a predetermined high discharge pressure including means to predetermine said high discharge pressure, means to conduct compressor discharge fluid to the pressure responsive means to actuate said pressure responsive means, and means to regulate the flow of discharge fluid to said pressure responsive means in accordance with variations in the pressure of the compres-' scr discharge fluid and to prevent flow oi fluid for a predetermined time after the pressure of the discharge fluid has reached said predetermined minimum pressure, means to unload the compressor at a predetermined pressure at least equal in magnitude to said predetermined high pressure and to reload the compressor at said predetermined minimum discharge pressure, and

means to predetermine said higher pressure with respect to said means to unload.

17. In a motor driven fluid compressor unit having a motor speed governor, means to control and vary the speed setting of the governor in accordance with variations of the discharge pressure of the compressor while the compressor is loaded having a-maximum speed setting position at a predetermined minimum pres,

sure and a minimum speed setting position at a predetermined high discharge pressure including pressure responsive means actuated by the pressure of the compressor discharge fluid, means to control the compressor discharge fluid actuatingthe pressure responsive device and to prevent actuation thereof for a predetermined time when the discharge pressure reaches said predetermined minimum pressure, and means to unload the compressor at apredetermined pressure at least as great as said predetermined high pressure and'to reload the compressor at said predetermined minimum pressure.

18. In a motor driven fluid'compressor unit having a motor speed governor, means to'control and vary the speed setting of the governor in accordance with variations of the discharge pressure of the compressor while the compressor is loaded having a maximum speed setting position at a predetermined minimum pressure and a 'minimum speed setting position at a predetermined high discharge pressure including pressure responsive means actuated by the pressure of the compressor discharge fluid, means to control the compressor discharge fluid actuating the pressure responsive device and to prevent actuation thereof for a predetermined time when the discharge pressure reaches said predetermined minimum pressure, means to unload the compressor at a predetermined pressure at least as great as said predetermined high pressure and to reload the compressor at said predetermined minimum pressure, and means to piedetermine said predetermined pressures.

19. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and regulate the speed setting of the governor comprising a chambered casing, pressure actuated means in the casing, means to transmit movement of the pressure actuated to the governor, means to vent said chamber, a diaphragm in the casing subject to the pressure of the compressor discharge fluid -and defining a second and a third chamber in the casing, said second chamber being in communication with the flrst' said chamber,- a spring pressed valve normally open to'c'ontrol communication between the flrst said chamber and said second chamber bearing against said diaphragm, a spring in the third chamber bearing against the diaphragm, means to regulate the compression of said spring, means to vent said third chamber, and an oriflced check valve in the last said means to delay the entrance of fluid into the third chamber.

.20. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device to control and regulate the speed setting of the governor comprising a chambered casing, pressure actuated means in the casing, means to transmit movement of the pressure actuated to the governor, means to vent said chamber, a diaphragm in the casing subject to the pressure of the compressor discharge fluid and defining a second and a third chamber in the casing, said second chamber being in com- Ill chamber, an orificed check valve in the last said means to delay the entrance of fluid into the third chamber, and means to unload the compressor at a predetermined discharge pressure and to reload the compressor at a predetermined 5 minimum discharge pressure.

CHAS. S. BAKER.

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