US2171286A

US2171286A - Compressor regulator

Info

Publication number: US2171286A
Application number: US190799A
Authority: US
Inventors: Charles S Baker
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1938-02-16
Filing date: 1938-02-16
Publication date: 1939-08-29
Anticipated expiration: 1956-08-29
Also published as: GB524958A; FR850295A

Description

Aug. 29, 1939. c. s. AKER v 2,171,286

COMPRESSOR REGULATOR Filed Feb. 16, 1938' 4 Sheets-Sheet 1 HIS ATTORNEY;

Aug 29; 1939. R c, s, BAKER 2,171,286

COMPRESSOR REGULATOR -F'iled Feb. 16. 19:58- 4 Sheets-Sheet 2 10.9 I 1a; 1041 0 .95 r 191 1w 1% 110 10.9

. 7 c533. (9.9.7.92 )2 9 9? 5 74 i n 76 .91

m5 ATTORNEY.

c. s. BAKER 2,171,286

COMPRESSOR REGULATOR Aug. 29, 1939.

4 Sheets-Sheet 3 Filed Feb. 16, 1938 \N M @w a v v Q v R v h M 0. @W L; 0 a Q m A v, r R 3 \Q Q Ti. I MN. u .w I. I MN, U w M -$a 4 $m ww a... M o N m NH \w Q 0 {L {E a .K w Mm wlwfi 3 QN .wN N g w Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE gersoll-Rand Company, Jersey City, N. 1., corporation of New Jersey Application February 16, 1938, Serial No. 190,799

35 Claims.

This invention relates to motor driven fluid compressors, and more particularly to apparatus to control the speed of the motor by the variations in the discharge pressure of the compressor a and to maintain the compressor fully loaded until the speed of the motor has been reduced to a minimum.

A motor driven fluid compressor unit comprises a motor or engine, such as an internal combustion motor or steam engine, directly connected to drive a compressor which compresses a fluid and delivers it to a receiver tank where it is stored until used. Ordinarily, in order to prevent overloading of the receiver, regulator means are provided which, when the pressure in the receiver tank reaches a predetermined point, 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; The compressor unit then idles until the pressure in the receiver tank falls to a predetermined minimum pressure whereupon the regulator 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 disadvantages of operating the compressor unit in this way are that the compressor will not run at a minimum speed at any time unless the compressor is completely unloaded, nor will it operate at any speed but the maximum speed when the compressor is loaded.-

It is accordingly an object of the present invention to provide means whereby the speed of the motor of a compressor unit may be controlled by variation in the discharge pressure of the compressor. e

It is another object of the invention to provide means whereby a motor driven compressor unit may operate at its minimum speed without unloading.

It is' a further object to provide means in a compressor unit whereby the compressor maybe gradually unloaded in accordance with a gradual rise in the discharge pressure of the compressor v after a predetermined high discharge pressure of the compressor is reached.

Still another object is to provide means in a w compressor unit whereby the degree of unload-' ing or reloading of the compressor is-dependent on the discharge pressure of the compressor.

A further object is to provide a device in a r 3 compressor unit whereby the motor speed is held REISSUED JAN 2 3 1940 (0]. 230-4) at aminimum during unloading and reloadingof the compressor. Still another object is to provide a device in a compressor unit whereby'the motor may accelerate or decelerate between the maximum and the 5 minimum speeds of the motor before the compressor begins to unload.

Another object is to provide a compressor unit v with a device whereby the motor may be accelerated and decelerated between its maximum and 10' minimum speeds until the compressor discharge pressure reaches a predetermined high pressure and thereafter remain at its minimum speed 'until a predetermined minimum discharge pressure is reached.

These and further objects will be readily apparent from the following description of which the drawings, in which similar numerals indicate like parts, form a part and in which Figure 1 is a view partly in elevation and part- 20 ly in section illustrating the application of the present invention to a compressor unit. A portion of the governor regulator and the governor is increased in size in order that the details may be brought out more clearly,

Figure 2 is a view partially in elevation and partially in section of the governor regulating portion of the regulator constructed in accordance with the principles of this invention, and

Figure 3 is a view similar to Figure 1 illustrat- 3 0 ing the application of a modification of the present invention to a compressor unit,

Figure 4 is a sectional view .of the governor regulator illustrated in Figure 3, and I Figure 5-is a view in section of the load regu- 35 lating portion of the compressor unit shown in Figures 1 and 3. With reference to Figs. 1 and 3, the compressor unit consists of an internal combustion motor I, mounted on a frame 3, supported by wheels 5, 40 and directly connected to drive the fluid compressor I, which is likewise mounted on the frame 3. Fluid is delivered to the compressor 1 through a conduit 9 and delivered from the compressor to a receiver tank II by the conduit l3.

The speed of the motor I is controlled by a governor generally indicated at l5, having a. shaft I'I directly connected to the shaft of the motor I (not shown). The shaft I! has a flange iii to which is secured a gear 2|. on the gear 2|, are weights 25 which carry rollers 21.

Accordingly, when the weights move outwardly against the force of the governor spring 33,'the motion of the plate is transmitted through Fulcrumed at 23,

the anti-friction bearing 35 to a plate 31 formed integral with pin 3| coaxial with and slidably mounted on the shaft H. The plate 31, through the clevis 39 and a lever 4|, fulcrumed on the frame of the motor at 43, transmits motion to a link 45 rotatably connected to the lever 4|, by pin 41 at the end opposite to that at which the clevis 39 is secured. This tie-rod or link 45 actuates the butterfly valve 49 in the fuel intake of the motor I, and since outward movement of the weights 25 will cause the tie-rod 45 to move toward the left the consequent movement of the butterfly valve will decrease the fuel supply to the motor and thus decelerate the motor speed. Thus as the motor I rotates, centrifugal force causes the weights 25 to fly toward their outermost position and upon reaching this position they cause the closing of the throttle valve 49 to prevent a further increase in the speed of the" motor.

Conversely,-as the speed of the motor is de creased, the weights 25 move in towards the shaft l1 causing the plate 29 to move in the same direction and pivot the lever 4| about its fulcrum 43. This makes the tie-rod 45 pivot the butterfly valve about its fulcrum 5| toward its open position to increase the fuel supply to the motor and to thus tend to accelerate the speed of the motor.

As is customary in centrifugal governors, the weights 25 are held in their retracted position by the governor spring 33 and the tension of this spring determines the motor speed at which the weights 25 will move to their outermost position. In order to house the spring, a casing 53 having a bore 55 extending therethrough is secured on the frame of the motor. The bore 55 communicates with a recess 51, formed in one end of the casing 53, and has a punger 59, provided with a flange 6| resting in the recess 51, extending therethrough. One end of the spring 33 rests against the flange 6| and the opposite end bears on member 63 and holds that member against a projection 65 provided on the lever 4|.

The portion of the plunger 59 which extends outside of the casing 53 bears against a hooked lever 61, fulcrumed on the casing 53 at 69 and adapted to move the plunger 59 to compress or release the spring 33. Since the speed setting of the governor is determined by the amount of force the weights 25 must exert on the plate 29 in order to overcome the force of the spring 33, it is apparent that should the hooked lever 61 force the plunger 59 to compress the spring 33 to its compression limit the motor will have tooperate at its maximum speed in order that the centrifugal force of the weights 25 shall be sulficient to overcome the resistance of the spring 33. Under such conditions. consequently, 'in order for the weights to move outwardly enough to move the lever 4| to throttle the motor, the speed of the motor must exceed the maximum desired speed.

Conversely, if the hooked lever 61 is moved in the opposite direction, so that the spring 33 may expand, plate 29 may be moved out from the shaft H, by the weights 25, when the motor is operating at a much slower rate. As a result, under such circumstances the motor will operate at a minimum speed and the slightest increase in speed will cause the weights 25 to move the plate 29 further away further close the butterfly valve to throttle the motor intake and decrease the speed to the desired minimum motor operating speed.

from the shaft and thereby It follows, therefore, that if the position of the hooked lever 21 is controlled, the speed setting of the governor may be changed to regulate the motor speed in varying degrees and for that purpose a pressure responsive device which will assume various positions in accordance with the discharge pressure of the compressor is connected to the lever 61 by a tie-rod 1|.

The details of the regulating mechanism are best illustrated in Fig. 2. With reference thereto it will be noted that it consists of a casing generally indicated at 12 secured to the motor frame by suitable means such as the bolts 13 and provided with a bellows chamber 14 closed by a head 15. The interior of the bellows chamber 14 is connected directly to the receiver tank by a conduit 16. The conduit 16 threadly engages the bushing 11 which has an orifice 18 to restrict the flow of fluid coming from the receiver. The fluid enters the bellows chamber 14 after leaving the orifice 18 through the passage 19.

Head 15 is provided which extends the plunger rod 8|, having a piston member 82 fastened to the end thereof within the bellows chamber. One end of a bellows 83 is secured to the piston 82 in air-tight relationship and the opposite end of the bellows is secured in air-tight relat onship between the casing 12 and the head 15 in order that it will be impossible for any fluid in the bellows chamber 14 to enter the bellows proper 83.

At the opposite side of the casing, to that where orifice 18 is positioned, is a passage 84 passing through a portion of the casing 12 and the head 15. In this passage is a bushing 85 with an orifice 86 secured in end thereof. The area of the orifice 86 is larger than the area of the orifice 18 and, consequently, the fluid entering the bellows chamber is restricted more than the fluid leaving the bellows chamber through orifice 86.

With this arrangement of parts the bellows chamber will be subjected to fluid at the same pressure as the fluid in the receiver tank since fluid is. conveyed from the receiver tank to the bellows chamber by the conduit 16 and enters the chamber through the orifice 18. If the orifice 86 were not provided, it is readily apparent that the bellows chamber 14 would constantly be subjected to the same pressure as the receiver However, with a means, which will be described hereinafter, to open and close the venting orifice 86 the pressure in the bellows chamber 14 will vary considerably from the pres sure in the receiver tank II.

The external end of the plunger rod 8l' is clevised and rotatably fastened to the lever 81 by the pin 88 which also serves to connect the regulator lever 89 fulcrumed at 80, on the head 15. The pin 88 thus makes it possible to have relative rotation between the

levers

81 and 89 and the plunger 8|. Surrounding this pin connection is a guard 9| head 15 threadedly engaged by the bolt 82, locked in position by the lock nut 93, to regulate the outward movement of the plunger 8|.

As a result of this arrangement, when orifice 86 is closed, the pressure in the bellows chamber 14 corresponds to the pressure in the receiver tank ii, and if the pressure is sufficient, it will move the bellows 83 to the right. This movement will be opposed by the resilience of the bellows 83 and the pressure of atmosphere, since passage 88 is large enough to permit air to enter around the plunger 8| into the interior of the formed as a part of the' with a passage 80 through bellows 83. Of course, as the bellows 83 moves when the end'of the plunger 8| bears against the bolt 92.

Conversely, when the orifice 88 is opened, the

pressure in the bellows-chamber 14 will drop since fiuid may escape to atmosphere permitting the resilience of the bellows 83 and atmospheric pressure to move the bellows to the left carrying the plunger 8| with it.

Movement of the plunger 8I will pivot lever 89 about its fulcrum 98 and thus, by means of tierod 1 I, transmit movement of the bellows 83 into regulation of the compression on governor spring 33.

The apparatus controlling the opening and closing of orifice 88 will now be described. In the upper part of the casing 12 is a recess 94 having an enlarged portion 95 in which. is secured, by plate 98, suitably fastened to the easing, a diaphragm 91. A branch of conduit 18 issecured in the passage 98 opening into the diaphragm chamber 99. It will thus be seen that the receiver tank pressure will be maintained in the diaphragm chamber 99. At the casing end of recess 98 is a threaded bore I88 designed to receive the guide bushing I8I for the plunger I82 extending into the recess.

The plunger I82 has a follower portion I83 bearing against the diaphragm 91. Within the recess 98 the guide bushing |8I has a flange I88 on which one end of a spring I85 rests and the opposite end of the spring bears against the follower I88. By means of the guide bushing II II the compressionof the spring I85 may be regulated and a lock nut I88 serves to maintain the bushing in a fixed position.

The end of the plunger-I82 oppositeto the end having the follower I88 is reduced in diameter and has a threaded portion I81 to receive a regulating bushing I88 and a locking means such as the nut I89. The upper portion of lever 81 is provided with a passage I I8 of sufiicient diameter to permit the shaft I82 to pass therethrough.

A spring III is maintained between the lever 81 and the bushing I88. Where the reduced portion of the shaft I82 begins a shoulder is formed and which provides a seat for the slidable abut ment I I2. This slidable abutment is freely movable on the reduced portion of the shaft I82. The spring I normally holds the lever 81 against the abutment II2. In order to permit free movement of the lever 81 about pin 88 and a constant contact point between that lever and abutment II2, a recessed surface H3 is formed on the lever 81 to prevent the tip end of the lever from touching the abutment. Intermediately placed on the 'lever 81 is a button valve II8.

which is so positioned with respect to the orifice 88 in the bushing 85 that under normal conditions the button obstructs the orifice and at least to some degree prevents escape of fiuid from the bellows chamber 18. i v

In order to lock the apparatus in the maximum speed setting position a locking cam and handle H is pivotably mounted on the head 15 and may be moved into position to lock the lever 89 in a position to maintain the maximum tension on the g ernor spring 33. From this description it will be seen that as the pressure in the receiver tank II increases the. pressure on diaphragm will increase tending to move the diaphragm 91 and shaft I82 toward the right against the resistancenof spring I85. As shaft I82 moves to the right it pushes abutment I I2 against the end of lever 81 which consequently moves rightwardly. Only the upper portion of lever 81 will move since the lower end pivots about pin 88 and consequently the button valve I is moved away from orifice 88 to open that orifice. 0n the other hand, assuming that orifice 88 is open due to a high pressure in the receiver tank, and that the pressure begins to fall, the diaphragm 91, shaft I82, bushing I88 and spring III will be moved leftwardly when the compression of spring I85 is sufficient to overcome the pressure of the fluid in diaphragm chamber 99. This movement will pivot lever 81 toward the left and thereby close orifice 88.

In the modified regulator illustrated in Figs. 3 and 4 the parts and the operation is slightly different and it will be seen to consist of a casing |I8 securely fastened to the frame of the motor by suitable meanssuch as the bolts II1.

The casing H8 is provided with a bellows chamber II8, closed by a head II9, communicating' with the intake manifold I28 of the-motor I through the opening I2I, in' which is secured a bushing I22, having an orifice I23, to connect the pipe I28, leading from the intake I28 of the motor, to this chamber. Within the chamber I I8 and bearing against a wall thereof is a spring I25, the other end of which bears against the member I28 provided with a flange I21 forming the head of the bellows I28 and to which one end of the bellows is secured. The other end of the bellows is held between the casing H8 and the head 9.. 1

Centrally located in the head H9 is a bore I29 through which extends a hollow shaft I38 secured to the member I28 and providing communication with the passage I3I in the member I28. A bushing I32 having an orifice I33, is inserted. in the passage through shaft t38 which vents the chamber II8 to the atmosphere.

It will thus be apparent that, while' the motor is operating, the vacuum set up in, the intake manifold is directly communicated to the bellows chamber II8 through the conduit I28, the orifice I23 and the opening I2I. If there were no vent for this chamber, the vacuum set up therein would cause the bellows to expand against the compressive force of the spring I25. However, since the evacuation of air from the-bellows chamber 9 is restricted by the orifice I23, a vacuum cannot be effected in that chamber unless the orifice I83 is at least partially closed. Thus with this orifice I33 open, air may enter through the orifice I33 and pass through the shaft I38 and the member I28 into the casing and drawn through the conduit I28 to the intake manifold I28.

The shaft I88 carries an extension clevis I34 to which is fastened, by the stud I35, the lever I38 fulcrumed on a portion of the head H9, at I31, and rotatably secured to the tie-rod 1|. It will be seen that movement of the bellows under the influence of the vacuum in chamber H9 will be directly transmitted to the governor spring 33. The range of longitudinal movement of the shaft I38 is limited by the position of bolt I88 threadedly engaged in the head 9. Movement of the bellows I28 and the shaft I38 is controlled by regulating the degree of the vacuum set up in the chamber II9. Such regulation is accomplished by the T-lever I38 fulcrumed at I89 and adapted to control the orifice I38.

The movement of the lever I38 is controlled by the pressure responsive device generally indicated at I88. This device consists of plunger ated by a diaphragm I43 against which it is held by the pressure ofa coil spring I44. Plunger I is guided in a sleeve I45 extending into chamber I46 formed in casing I I6, and threaded therein being held in place by lock nut I41. Diaphragm I43 is held in place by a head I48 bolted to flange I49 of easing I I6 and forming a pressure chamber I50, the inlet I5I of which is connected by means of pipe I52 to the receiver tank II. Spring I44 bears against the head I42 of plunger HI and flange I53 on bushing I45, its tension being adjustable by screwing the bushing I45 into or out of the chamber I46, suitable flats I54 being provided for that purpose on the bushing I45.

A part I55 of the shaft I44, which extends outside of the casing H6 and sleeve I45, is reduced in diameter and is provided with a bearing flange I 56 of greater diameter than the shaft I4I proper. Slidable member I51 supported by this part I55 of the shaft and bearing against the spring I58 is held on the shaft by a nut I59, which also serves to regulate the degree of compression on the spring I58. Leg I60 of lever I38 is interposed between bearing flange I56 and spring I56 being provided with a hole I6I to receive portion I55 of plunger I. The motion of plunger I is thus transmitted to lever I38 to vary the restriction at the opening of orifice I33. One portion of the member I51 rests on the raised portion I62 provided on the leg I63 of the T-lever I38 and is arranged to latch therewith as will be described hereinafter.

With reference again to Figs. 1 and 3, a means to unload and reload the compressor is provided a between conduit 9 and the compressor 1.

The details of this device are illustrated in Fig. 5 and consist of a casing I 65 connected to the conduit 9. A portion of the walls of the casing extend within the outerwalls thereof to form the value guides I61 for the balance cylindrical valve I69. An opening "I in the casing is closed by a plate I13 which is provided with a recess I15 wherein a spring I11 rests. This spring normally urges the cylindrical valve toward its right hand or open position. When the valve is in its open position, the fluid may enter from conduit 9, flow past the cylindrical valve I69 and into the compressor.

Another chambered casing I19 is secured on one side of the casing I65 directly opposite to the plate I13. In this chamber casing is the guide I8I formed integrally with the chamber casing I65 to slidably support a bushing I83 which, in turn, supports the rod I85. One end of the rod bears against the cylindrical valve I69 and has a head I81 formed end thereof.

The head I81 rests which is secured to the at the opposite against a diaphragm I89 chamber casing I19 by the cup I9 I. The bushing I83 is formed with a flange I93 to bear against the spring I95, normally urging the head I81 and shaft I85 toward the right. Between'the diaphragm and the cup I9I, is a chamber I91 which is in direct communication with the receiver tank I I through the conduit I99. With this device forming part of the compressor unit it will be noted that, as the pressure in the receiver .tank increases to the point where it is suflicient to move the head 81 against the compression of the spring I95, the rod I85 will move to the left and consequently move the cylindrical valve toward its closed position.

If the pressure. should decrease after reaching 2,171,286 I having a head I42 and adapted to be actuthis point. the spring I will move the rod I85 toward the right against the pressure in the receiver and the cylindrical valve will follow the rod I85, being urged by the spring I11.

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

Referring again to the regulator shown in Figs. 1 and 2 and assuming that the pressure in the receiver I I is below a desired minimum value, lack of pressure in the chamber 99 permits the spring I05 to maintain the diaphragm 91 and the shaft I02 in its left hand position (Fig. 2). In that position the spring III will hold the lever 81 against the abutment I I2 thus holding the button valve II4 escape of fluid through the orifice from the chamber 14. With this orifice closed, the pressure in chamber I4 will naturally be the same as the pressure existing in the receiver tank I I.

Upon increasing the pressure in the chamber 14 the bellows 83 will collapse causing plunger 8I to exert force on lever "which, through link 1I, lever 61 and plunger 59, compresses the governor spring 33 tending to open the throttle valve 49. In this manner the speed setting of the governor I5 is changed to increase the speed of engine I. As the motor speeds up, the pressure in the receiver tank begins to rise and to increase the pressure on diaphragm 91. Shaft I02 thus pushes against the abutment II2 which, in turn, moves the lever 81 until the button valve II4 begins to open the orifice 86. Fluid may then escape faster from chamber 14 through the larger orifice 86 than it enters the chamber through the smaller orifice 18. Atmospheric pressure within the bellows 93 then tends to expand the bellows and to withdraw shaft 8I into the bellows pulling with it lever 89 and correspondingly reducing the compression of governor spring 33, closing the throttle valve 49, and reducing the engine speed. The

reduction in engine speed correspondingly reduces compressor produces just enough air to supply the demand or until the discharge pressure reaches a predetermined value whereat the motor is reduced to its minimum speed. Prior to reaching such predetermined pressure the diaphragm 91 and plunger I02 will have reached their extreme right hand position where they remain so long as the pressure in the receiver I I does not fall.

Upon reaching the predetermined high pressure above referred to, the compressor is further unloaded progressively by choking its inlet. This is accomplished by apparatus shown in detail in Fig. 5. The initial compression of the spring I95 is adjusted by means of the threaded bushing I83 to equal the total pressure on the opposite side of diaphragm I89 when the above mentioned predetermined high pressure is reached. At values above that pressure, diaphragm I89 pushes the plunger I85 against inlet valves I69 to overcome of the spring I11; thus,

some predetermined high pressure it will be seen that the valve I69 will completely choke the compressor Inlet and thereby completely unload the against the orifice 86 to prevent the spring I05 will hold the plunger I02 in the withdrawn position until the pressure in the receiver tank increases whereupon the same cycle will occur.

Obviously, under varied loads, the regulator may accelerate or decelerate the engine I without approaching the minimum or maximum speeds of the engine-I. Furthermore, the pressure in the spring I05 may be adjusted to predetermine the pressure necessary to move the plunger I02 and by this means the minimum and maximum speeds may be predetermined.

The operation of theregulator of Figs. 3 and 4 is as follows: a

Assuming that the pressure in the receiver II is below a desired minimum value, alack of pressure in the chamber I50 permits the spring I44 to move the diaphragm I43 and the shaft I4I to the. left (Fig. 4). In that position the lug I51 has passed beyond the raised portion I82 and rests in the recess I88 formed on the leg I83 of the T-lever I38. The T-lever I38 is held out of engagement with the orifice bushing I32 and permits the entry of air throughthe orifice and shaft to the chamber II8. Atmospheric pressure in chamber II8 equalizes the fluid pressure on bellows I28 and permits spring I25 to collapse the bellows and exert force on lever I38 which through link 1I, lever 81 and plunger 53 compresses governor spring 33 tending to open throttle valve 49. In this manner the speed setting of governor I5 is changed to increase the speed of engine I. As the motor speeds up, the pressure in the receiver tank begins to rise and to increase the pressure on diaphragm I43. Plunger I4I thus pushes against the end I80 of lever I38 until the other end of that lever begins to restrict theoriiice in bushing I32. Air is then withdrawn from chamber 8 faster through the larger orifice I23 than it enters the smaller orifice I32. Atmospheric pressure within bellows I28 opposes the spring I25 and the shaft I28 tends to withdraw from lever I38 pulling with it lever .I38 and correspondingly reducing the compression of governor spring 33, closing the throttle valve 49, and reducing the engine speed. The reduction in engine speed also reduces the rate of increase of compressor discharge pressure at receiver, II.

As the discharge pressure continues to increase, plunger I4I continues to push against lever I38 so as to close the orifice I33 and, simultaneously, the unbalance of air pressure on bellows I28 tends to withdraw that orifice from the lever with the consequent adjustment of compression of governor spring 33 causing reduction in the motor speed. The above described interaction continues until the motor speed is reduced to a point at which the compressor produces just enough air to supply the demand or until the discharge pressure reaches a predetermined value whereat the motor is reduced to its minimum speed also.

Prior to reaching such predetermined pressure? the sliding flange I51 has been hooked behind the projection I82. As the pressure increases and plunger I4I moves to the right, the portion of lever I38 designated by I80 also moves to the right. This movement causes projection I82 to' move 'down'until sliding flange I51 over-rides projection I82 and flange I51 is pushed ahead by spring I58 to lock lever I38 in place. The pressure responsive devices including lever I38 and bellows I28. and the devices actuating and actuated by them are rendered inoperative until a predetermined low discharge pressure is reached as will be described hereinafter.

, The unloading device of Fig. 5 operates with this regulator in the same manner as described in connection with the regulator of Figs. 1 and 2. Thus, after unloading the compressor and reloading the compressor, the speed of the engine I will not be resumed until the lowest permissible discharge pressure is reached, due to the latch- .ing of the plunger I51 on the projection I82 of lever I38 (Fig. 4). During such lowering of pressure, plunger I is withdrawn into chamber I48 without change in the position of lever I38, keeping closed the orifice I33 until nut I58 withdraws flange I51 from engagement with projection I82. Spring I58 is compressed during such withdrawal and, upon the disengagement referred to, causes end I 80 of lever I38 to resume its position against the abutment I58, whereupon flange I51 drops into the recess I85. Correspondingly, the end of lever I38 moves out of engagement with the orifice I33 to admit atmospheric pressure into bellows I28. Thereupon the movement of plunger I, under the influence of pressure in chamber I50, resumes control of the movement of the lever I38 and governor spring 33 as described above.

It will be seen that adjustment of the sleeve I in the casing is effected by turning the nut I54 and has the effect of moving the button I58 longitudinally with regard to the housing and, correspondingly, moves the end of lever I38. By this means, therefore, can be adjusted the pressure at which speed of the motor I begins to be eflected. Likewise, adjustment of the sliding flange I51 with respect to the plunger I4I, which is effected by adjustment of nut I59, will efiect the low pressure at which plunger I51 disengages itself from the projection I 82. The maximum speed of the motor may also be determined by adjustment of the stop screw I84 which limits the movement of lever I38 (Fig. 4).

If, for example, the motor is to be operated at its minimum speed when the pressure in the receivertank has reached 95 pounds per square inch, the compression of spring I05 is so adjusted in the regula or of Fig. 2 that lever 81 will hold valve I I4 in pa ltion to prevent the escape of fluid from chamber 14 and likigifie the compression of the spring I44 of the r ator of Fig. 4 is so adjusted that the lever I38 will prevent entrance of air into the chamber I I8 to thus reduce the motor speed to the minimum when that pressure is reached. If the pressure at which the unloading device is to begin functioning is 100 pounds per square inch, the proper compression on the spring I85 is secured by regulation of the bushing I83, and when pressure increases to that pressure the unloading device will come into action and will gradually close the cylindrical valve. If the pressure increases still more until it reaches the pressure at which the compressor is to be completely unloaded, namely, at 105 pounds per square inch, the compressor will be completely unloaded. As long as the pressure in the receiver remains within the range of 100 to 105 pounds per square inch, the cylindrical valve will assume a closed or partly closed position comparably with the pressure in the receiver tank. If, however, the pressure in the receiver tank falls below 100 pounds per square inch, the spring I95 will overcome the pressure in the receiver tank and maintain the cylindrical valve open. Should the pressure continue to fall because of a heavy load, the governorregulator of Fig. 2 will begin to accelerate the motor towards its maximum speed as soon as the pressure falls below 95 pounds .compressor will be pressure and will thenceforth control the speed of the engine whereas the regulator of Fig. 4 will continue to maintain the motor at its minimum speed until some pressure such'as 80 pounds per square inch is reached at which time the lever I38 will be free from the orifice as was explained previously and the motor may again accelerate to its maximum speed.

It is manifest, therefore, that the unloading and reloading device will not operate until a pressure is reached suflicient to maintain the governor at a minimum speed setting position and will then vary the degree of loading of the compressor in accordance with variations in the discharge pressure of the compressor. Furthermore, when the pressure falls, the governor speed regulator of Fig. 2 will begin regulating the motor speed as soon as the compressor is completely reloaded whereas the regulator of Fig. 4 will maintain the motor at its minimum speed until a much lower pressure than that required to obtain minimum speed is reached.

The pressures herein designated have been assumed merely for the sake of explanation and may be varied to secure other speed and unloading ranges provided the unloading device does not begin to function until the motor is operating at substantially its minimum speed. Furthermore, it may be advantageous to operate the compressor unit in a manner to permit the compressor to begin unloading at the same pressure as that at which the speed of the motor is reduced to its minimum speed.

During the operation of the compressor under the above pressure settings and' under loads which prevent the receiver pressure from increasing to 95 pounds per square inch, the motor speed will progressively and degressively vary as the pressure in the receiver increases and decreases. Thus, if the pressure in the receiver increases and decreases, the motor speed will in crease and decrease inversely with the pressure changes. after the inch, this Of course, with the regulator of Fig. 4, pressure reaches 95 pounds per square regulator maintains the speed at the minimum speed until the pressure in the receiver decreases to the predetermined low pressure, namely 80 pounds per square inch, at which point the compressor will begin reloading at maximum speed again.

Likewise, when the pressure in the receiver hovers within the range of 100 to 105 pounds per square inch, the degree of unloading or reloading varies progressively and degressively with the pressure change. Thus, at a pressure in close proximity to 105 pounds per square inch, the compressor will be almost completely unloaded whereas, with the pressure above but in close proximity to 100 pounds per square inch, the almost completely reloaded. Within this range the amount which the unloading valve opens and closes depends on the pressure and the receiver tank and will vary with the variations of the pressure. Upon an increase in pressure, the valve will close and, upon a decrease in pressure, it will open.

It is understood that the constructions above described are preferred embodiments 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 regulator to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high discharge pressure, and means to vary the quantity of fluid admitted to the compressor between a. maximum and a minimum quantity upon any variation in the discharge pressure of the compressor above said predetermined high discharge pressure.

2. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive regulator to control and vary the speed setting of the governor between maximum and minimum motor speed upon any variation of the discharge pressure respectively between a predetermined minimum discharge pressure and a predetermined high discharge pressure of the compressor, and means to vary the quantity of fluid admitted to the compressor between a maximum and a minimum quantity upon any variation in the discharge pressure respectively betweensaid predetermined high discharge pressure and 'a predetermined maximum discharge pressure of the compressor.

3. In a motor drivenfluid compressor unit having a motor speed governor, a pressure responsive regulator to control and vary the speed setting of the governor having speed setting positions between maximum and minimum motor speed, means to control the pressure responsive regulator and vary its speed setting position upon any variation in the discharge pressure of the compressor between a predetermined minimum discharge pressure and a predetermined high discharge pressure, and means to vary the quantity of fluid admitted to the compressor upon variation in the discharge pressure of the compressor above said predetermined high discharge pressure.

4. In a motor driven fluid compressor unit having a motor speed governor, pressure responsive means having positions intermediate the maximum and minimum motor speeds to control and vary the speed setting of the governor, means to control the pressure responsive means and vary its speed setting position between maximum and minimum motor speeds upon respective variations intermediate a predetermined minimum discharge pressure and a. predetermined high discharge pressure of the compressor, and means to vary the quantity of fluid admitted tothe compressor between a maximum and a minimum quantity upon any variation in the discharge pressure of the compressor respectively between said predetermined high discharge pressure and a-predetermined maximum discharge pressure of the compressor.

5. In a motor driven fluid compressor unit having a motor speed governor, pressure responsive means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high discharge pressure comprising a casing having a chamber, means in the chamber sure,

subject to the discharge pressure of the compressor adapted to regulate the speed setting position of the governor, a vent for the chamber, a second chamber in the casing subject to the discharge pressure of the compressor, means responsive to the discharge pressure in said second chamber to open and close said vent, and means to vary the quantity of fluid admitted to the compressor upon any variation in the discharge pressure of the compressor above said predetermined high discharge pressure of the compressor.

6. In a motor'driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a pressure responsive device to control and vary the speed setting of the governor upon variation of 'the discharge pressure of the compressor below a predetermined high discharge pressure and having a maximum. and minimum speedsetting position, means forming a part of said device to cause the pressure responsive device to gradually change the speed setting of the governor to the minimum speed position as the dimharge pressure approaches said predetermined high discharge pressure, and means to vary the quantity of fluid admitted to the compressonupon any variation in the discharge pressure of the compressor between said predetermined discharge pressure and a predetermined maximum pressure.

'1; In a motor driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high presmeans to predetermine said high pressure, and means to vary the quantity of fluid admitted to the compressor upon any variation in the dis charge pressure above said predetermined high discharge pressure.

8. In a motor driven fluid compressor unit having 'a speed setting governor to regulate the speed of the motor, a pressure responsive device to control and vary the speed setting of the governor between maximum and minimum motor speed positions upon any variation of. the discharge pressure respectively between a predetermined minimum discharge pressure and a predetermined high discharge pressure of the compressor, means to predetermine said minimum and high discharge pressures, means to vary the quantity of fluid admitted to the compressor between a maximum and a minimum quantity upon any variation in the discharge pressure respectively between said predetermined high discharge pressure and a predetermined maximum discharge pressure of the compressor, and means to predetermine said high, and maximum pressures with respect to the last said means.

9. In a motor driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure -of the compressor below a predetermined high discharge pressure, and means to vary the qua'ntity' of fluid admitted to the compressor upon any variation in the discharge pressure of the compressor above said predetermined high discharge pressure comprising a casing having a chamber therein associated with the fluid inlet of the compressor, a valve inthe fluid inlet of the compressor, movable means subject to the discharge pressure of the compressor in said chamber and consaid device to cause said device I speed setting nected to move said valve upon movement thereof, and means to predetermine the pressure at which said movable means will move.

10. In a motor driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a. pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a, predetermined high discharge pressure and having various speed setting positions between maximum and minimum speed setting position, means forming a part of the device to gradually change the speed setting of the governor to the minimum speed position as the discharge pressure approaches said predetermined high discharge pressure and to gradually change the speed setting of the governor to the maximum speed position as the discharge pressure decreases from said predetermined high discharge pressure toward a predetermined minimum. discharge pressure, and means to vary the quantity of fluid admitted to the compressor upon any variation in'the discharge pressure of the compressor between said predetermined high discharge pressure and a predetermined maximum pressure.

11. In a motor driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a pressure responsive device to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high discharge pressure and having various speed setting positions between maximum and minimum speed setting position, part of said device to cause the device to gradually change the speed-setting of the governor to the minimum speed position as the discharge pressure approaches said predetermined high discharge pressure and to gradually, change the speed setting of the governor to the max mum speed position as the discharge pressure decreases irom said predetermined high discharge pressure toward a predetermined minimum discharge pressure, means to gradually reduce the quantity of fluid admitted to the compressor to a minimum as the discharge pressure approaches a predetermined maximum discharge pressure and to increase the quantity of fluid admitted to the compressor to maximum as the discharge pressure decreases from the predetermined maximum discharge pressure toward the predeter- .mined high discharge pressure.

12. In a motor driven fluid compressor unit having a speed setting governor to regulate the speed of the motor, a pressure responsive device to control'and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high discharge pressure and having various speed setting positions between maximum and minimum speed setting position, means forming a part of to cause the device to gradually change the speed setting of the governor to the minimum speed position as the discharge pressure approaches said predetermined high discharge pressure and to gradually change the of the governor to the maximum speed position as the discharge pressure decreases from said predetermined high discharge pressure toward a predetermined minimum discharge pressure, and means to vary the quantity of fluid admitted to the compressor upon any variation in the discharge pressure of the compressor above said predetermined high discharge pressure comprising a casing having a chamber therein associated with the fluid inlet of the compressor, a valve in the fluid inlet of the compressor, movable means subject to the discharge pressure of the compressor in said chamber and connected to move said valve upon movement thereof, and means to predetermine the pressure at which said movable means will move.

13. In a motor driven fluid compressor unit having a speed setting governor for the motor, a pressure responsive means to control and vary the speed setting of the governor upon variation of the discharge pressure of the compressor below a predetermined high discharge pressure comprising a casing having a chamber, means in the chamber subject to the discharge pressure of the compressor adapted to regulate the speed setting position of the governor, a vent for the chamber, a second chamber in the casing subject to the discharge pressure of the compressor, means to open and close said vent responsive to the discharge pressure in said second chamber, means to vary the quantity of fluid admitted to the compressor upon any variation in the discharge pressure of the compressor above said predetermined high discharge pressure comprising a casing having a chamber therein associated with the fluid inlet of the compressor, a valve in the fluid inlet of the compressor, movable means subject to the discharge pressure of the compressor in said chamber and connected to move said valve upon movement thereof, and means to predetermine the pressure at which said movable means will move.

14. In a motor driven fluid compressor unit having a 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 below a predetermined high discharge pressure, means to gradually reduce the quantity of fluid admitted to the compressor to a minimum as the discharge pressure approaches a predetermined maximum discharge pressure and to increase the quantity of fluid admitted to the compressor to maximum as the discharge pressure decreases from the predetermined maximum discharge pressure toward the predetermined high discharge pressure.

15. In a motor driven fluid compressor unit, a governor to regulate the speed of the motor having various speed setting positions between a maximum and a minimum speed setting position, a pressure device subject to the discharge pressure of the compressor to control and gradually change the speed setting position of the governor to the minimum speed position as the discharge pressure of the compressor approaches a predetermined high discharge pressure and to change the governor to the maximum speed position as the discharge pressure decreases toward a predetermined minimum pressure, means to predetermine said high and minimum pressures, means to gradually reduce the quantity of fluid admitted to. the compressor to a minimum as the discharge pressure approaches a predetermined maximum pressure and to increase the quantity of fluid admitted to the compressor to a maximum as the discharge pressure approaches said predetermined high discharge pressure, and means to predetermine said high and maximum discharge pressures with respect to the last said means.

16. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device for controlling and varying progressively and degressively the speed setting of the governor in accordance with variations of the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with the discharge pressure of the compressor above a predetermined high discharge pressure, and means to prevent said pressure responsive device from varying the speed setting of the governor when said predetermined high pressure is reached and until a predetermined minimum discharge pressure is reached.

17. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device for controlling and progressively and degressively varying the speed setting of the governor in accordance with the variations in the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with the discharge pressure below a predetermined compressor discharge pressure, means to render the pressure responsive device inoperative at said predetermined discharge pressure and operative thereafter at a predetermined minimum pressure to vary the speed setting of the governor, and adjustable means to regulate the pressure range within which the last said means operates.

18. In a motor driven fluid compressor unit having a motor speed governor, a. pressure responsive device for controlling and progressively and degressively varying the speed setting of the governor in accordance with the variations in the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with the discharge pressure of the compressor above a predetermined pressure, adjustable means to predetermine the pressure at which the last said means operates, means to render the pressure responsive device inoperative to vary the speed setting of the governor at said predetermined discharge pressure and thereafter render it operative at a predetermined minimum pressure, and adjustable means to regulate the pressure range within which the last said means operates.

19. In'amotor driven fluid compressor unithaving a motor speed governor, a pressure responsive device for controlling and progressively and degressively varying the speed setting of the governor in accordance with variations in the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with the discharge pressure of the compressor above a predetermined pressure, adjustable means to predetermine the pressure at which the last said means operates, and means to render the pressure responsive device inoperative to vary the speed setting of the governor at a predetermined pressure not exceeding the first said predetermined pressure and to maintain the pressure responsive means inoperative thereafter until a predetermined low discharge pressure is reached.

20. In a motor driven fluid compressor unit having a motor speed governor, a pressure rcsponsive device for controlling and progressively and degressively varying the speed setting of the governor in accordance with variations in the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with variations in the discharge pressure of the compressor above a predetermined pressure adapted to unload the compressor completely at a predetermined maximum discharge pressure, and means to render the pressure responsive device inoperative to vary the speed setting of the governor.

21. In a motor driven fluid compressor unit having a motor speed governor, pressure responsive means to control and progressively and vdegressively vary the speed setting of the governor in accordance with variations of the discharge pressure of thecompressor, means to progressively and degressively unload and reload the compressor in accordance with variations in the discharge pressure of the compressor within. a

predetermined range of compressor discharge pressures and above a predetermined high pressure, and means to lock the first said means to render it inoperative within a. lower predetermined'discharge pressure range when said predetermined high pressure range is reached.

'22. In a motor driven fluid compressor unit having a motor speed governor, means responsive to variations of the discharge pressure of the compressor to control and progressively and degressively vary the speed setting of the gov; ernor, means to progressively and degressively unload and reload the compressor in accordance with variations in the discharge pressure of the compressor above a predetermined high pressure, and means to lock the first said means to render it'inoperative to vary the speed setting of the governor at said predetermined high pressure.

23. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device for controlling and progressively and degressively varying the speed setting of the governor in accordance with variations in the discharge pressure of the compressor, means to unload the compressor progressively and de'gressively above a predetermined high discharge pressure until a predetermined maximum discharge pressure is reached and to progressively and degressively reload the compressor as the pressure falls from the predetermined maximum discharge pressure until said predetermined high discharge pressure is reached, means to lock the pressure responsive device to render it inoperative to vary the speed setting of the governor at said predetermined high discharge pressure to permit the governor to maintain the motor at minimum speed and to unlock the pressure responsive device to permit the governor to accelerate the speed of the motor to a maximum when a predetermined lower discharge pressure is reached.

24. In a motor driven fluid compressor unit having a motor speed governor, a source of fluid, means actuated by said fluid for controlling and progressively and degres'sively varying the speed setting of the governor, means responsive to the discharge pressure of the compressor to control actuation of the first said means by said fluid,.and means to progressively and degressively unload and reload the compressor in accordance with variations in the discharge pressure of the compressor.

25. In a motor driven fluid compressor unit having a motor speed governor, a source of fluid, means actuated by said fluid for controlling and progressively and degressively varying the speed setting of the governor, means to prevent actuation of the first said means by said fluid, means responsive to variations in the discharge pressure of the compressor to control the last said means, and means to progressively and degressively unload and reload the compressor in acsure of the compressor.

26. In a motor driven fluid compressor unit having a source of fluid, a motor speed governor regulator comprising a chamber, means in the chamber actuatable by said .fluid, means to vent the chamber and prevent actuation of the last said means by the fluid, means associated with the means in the chamber to transmit movement thereof to the governor, pressure responsive means subject to the discharge pressure of the compressor, means controlled by the pressure responsive means to open and close the venting means; and means to unload and reload the compressor above a .predetermined high pressure comprising a casing having a chamber subject to the discharge pressure of the compressor, movable means responsive to variations of the discharge pressure of the compressor, and a valve associated with the movable means to vary the amount of unloading and reloading of the compressor.

27. In a motor driven fluid compressor unit having a source of fluid, a motor speed governor regulator comprising movable means actuated by said fluid, means to prevent actuation of the movable means by said fluid, means associated,

pressure of the compressor, and a valve associated with the last said means to vary the amount ofunloading and reloading of the compressor in accordance with movements thereof.

28. In a motor driven fluid compressor unit having a motor speed governor, a pressure responsive device for controlling and varying progressively and degressively the speed setting of the governor in accordance with variations of the discharge pressure of the compressor, means to progressively and degressively unload and reload the compressor in accordance with the discharge pressure of the compressor above a predetermined high discharge pressure comprising a casing having a chamber subject to the discharge pressure of the compressor, movable means responsive to variations of the discharge pressure of the compressor, and a valve associated with the movable means to vary the amount of unloading and reloading of the com' pressor.

29. In a motor driven fluid compressor unit having a motor speed governor, of pressure responsive device for controlling and varying progressively and degressively the speed setting of the governor in accordance with variations in the discharge pressure oi. the compressor, means to progressivelyand degressively unload and reload the compressor in accordance with the discharge pressure of the compressor above a predetermined high discharge pressure comprising movable means responsive to variations in the discharge pressure of the compressor, and a valve associated with the movable means and responsive to movements thereof to vary the amount of unloading and reloading the compressor.

30. In a governor speed-regulator for a motor driven compressor comprising a casing having one chamber subjected to the discharge pressure of the compressor and a second chamber subjected to intake manifold pressure for the motor, pressure responsive means in each chamber, means to transmit movement of the pressure responsive means in the second chamber to the governor, means to admit atmosphere to the second chamber, and means actuated by the pressure responsive means in the first said chamber to render the last said means ineffective.

31. In a motor driven fluid compressor, a governor to control the speed of the motor, a pressure responsive device for controlling the characteristics of the governor in accordance with variations of the discharge pressure of the compressor, comprising a casing having a chamber subject to the discharge pressure of the compressor and a second chamber subject to the motor intake manifold pressure, pressure responsive means in each chamber, means to vent the second chamber to atmosphere, means controlled by the pressure responsive means in the first said chamber to render the venting means ineffective upon a predetermined minimum discharge pressure until a predetermined high dis charge pressure is reached.

32. In a regulator for a motor driven fluid compressor having a governor and means to progressively and degressively unload and reload the compressor in accordance with variations in the discharge pressure of the compressor, and a pressureresponsive device to control the speed setting of the governor in accordance with the variation of the discharge pressure of the compressor having chambers therein, means to vent one of the chambers to atmosphere, and means to close said vent when the discharge pressureof the compressor reaches a predeter-' mined minimum pressure and maintain it closed util a. predetermined high pressure is reached.

33. In a regulator for a motor driven compressor having a governor, a casing having a chamber subject to the discharge pressure of the compressor and a second chamber subject to the pressure of the motor intake manifold, pressure responsive means in said chambers, venting means for the second chamber, means associated with pressure responsive means in the other chamber to prevent venting by said venting means when the discharge pressure of the compressor reaches a predetermined minimum pressure and assure venting by said venting means when the discharge pressure of the compressor reaches a predetermined high discharge pressure, adjustable means to regulate the pressures at which said last means operates, and means connected with the pressure responsive means in said second chamber to directly control the governor speed setting.

34. In a regulator for a motor driven fluid compressor having a governor and a receiver to which the compressor discharges, comprising-a casing having a chamber in communication with the receiver and a second chamber in communication with the intake manifold of the motor, a diaphragm in the first said chamber, a bellows in said second chamber, a hollow plunger rod connected to the bellows, a vent formed in one end of the plunger rod to open the first said chamber to atmosphere, a plunger associated with the diaphragm, a lever actuated by the plunger, a valve on said lever and controlled thereby to open and close the vent, a series of levers connecting the hollow plunger rod and the governor to vary the speed setting thereof in" accordance with the movements of the bellows, and means to predetermine the pressure at which the diaphragm moves the plunger and lever to open and 'close the vent.

35. In a regulator for a motor driven fluid compressor having a governor, comprising 9. casing having one chamber subject to the discharge pressure of the compressor and a second chamber subject to the intake manifold pressure of ,the motor, a diaphragm in the first said chamber movable upon variation in the compressor discharge pressure, a plunger connected with the diaphragm, a bellows in the second chamber, a hollow plunger connected to the bellows, an orifice in the hollow plunger to admit atmospheric air through the plunger to the chamber, a pivotal lever associated with diaphragm plunger adapted to open and close the vent upon variation of the discharge pressure of the compressor, and

1 a series of inter-connecting levers to connect the hollow plunger to the governor whereby the speed setting of the governor may be varied in accordance with the movement of the bellows, and means to admit atmospheric air within the bellows whereby upon closing of the vent the vacuum created by the motor will expand the bellows and maintain the governor at its minimum speed setting position and upon opening of the vent the atmospheric pressure in the chamber will overcome the vacuum of the motor and compress the bellows to move the governor to its maximum speed setting position.

CHARLES S. BAKER.