US2181978A

US2181978A - Variable capacity compressor

Info

Publication number: US2181978A
Application number: US195277A
Authority: US
Inventors: Jr Edward M Paullin
Original assignee: Worthington Pump and Machinery Corp
Current assignee: Worthington Pump and Machinery Corp
Priority date: 1938-03-11
Filing date: 1938-03-11
Publication date: 1939-12-05
Anticipated expiration: 1956-12-05

Description

J Dec. 5 1939.

E. M; PALgLL-IN, J 2,1813% VARIABLE CAPACITY COMPRESSOR f Fi led aMarch "11, v 1958 s Sheet-Sheefl 1 Fig. 1

I EnvARa Mb PAuLumJa INVENTOR 1 ATTORNEY Dec. 5, .1939. E. M. PAULLIN. J 2,181,978

VARIABLE CAPACITY COMPRESSOR Filed March 11, 1938 s Sheets-Shet 2 FIQZ 155 2 6 5: o Fm. I3 69 121 66 q H o wiw i d) IF I .7 1 k; jkgza EDWARD MPAuLuN J I V ENTOR ATTORNEY mww x 9 E.'M.-PA ULL|N, JR 2,181,978

I VARIABLE CAPACITY COMPRESSOR Filed March 11, 1938 8 Sheets-Sheet 4 v L o TI f L N \\N EowAau M.'Pmu.1,m JR.

INVENTOR ATTORNEY D 1939- E. M. PAULLiN, JR 2,181,978

VARIABLE CAPACITY: COMPRESSOR Filed March 11, 1958 Y a Sheets-Sheet 5 Fla. .5

EnwAaa M. PAuLLm-JR l ENTOR ATTORNEY 9- I E. M. PAULLIN, JR 2,181,978

mum imam-n comxssoa Filed Iarch 11, 1938 8 Shets-Sheet s ATTORNEY.

DH; 1939. E. Q. PAULLIN, JR $181,978

VARIABLE CAPACITY COIPRBSSOR Filed Hal-ch '11,- 1938 a sheets-sheet 1 F 4 FIG-25 mes v k c D I Enmnn M.PAm.uu,Jn.-

7 77m: INVENTOR ATTORNEY Patented Dec. 5, 1939 i 2,181L978 I I v I v VARIABLE CAPACITY COMPRESSOR Edward M. 'Paullin, Jr., Buffalo, N. Y., assignor to Worthington Pump and Machinery Corporation, Harrison, N, 1., a corporation of Delaware Application March 11, 1938, Sei'la1 N0. 195,277

1 33 Claims.

' This invention relates to variable capacity air or gas compressors, and more particularly to a governing mechanism for controlling the loading and unloading of a compressor in predetermined percentages of its capacity, such loading and unloading being automatically controlled by pressure of fluid compressed, either before or after compression in accordance with the load demands upon the compressor, thereby maintaining practically constant the suction or the reservoir pressure.

More particularly the present invention is an improvement of the variable capacity compressor and governing mechanism disclosed in my copending application Serial Number 740,869, filed August ,22, 1934.

An object of the present invention is to provide a variable capacity control governor or instrument which embodies means, the action of which makes it possible ,to operate the compressor at fractional percentages of its capacity at exactly the same pressures as those at which it woul operate at full load and capacity.

Heretofore, in variable capacity compressors and their control mechanisms, the above operation has not been possible, since in approved types on the market, with the compressor operating at full capacity a decrease in load demand is reflected in an increased receiver pressure. If the increased pressure is suflicient to cause the governor or control instrument to operate, the compressor drops to 75% capacity operation and continues to operate at the higher pressure unless the pressure in the reservoir system due to the decreased compressor capacity tends to fall off. If a further increase in pressure is had, .the governor or control mechanism will again operate to reduce the output capacity of the compressor to Likewise the pressures pyramid until finally the compressor is completely unloaded at a pressure which is considerably above the normal 100% capacity pressure, actually four times the pressure difierential per step of fractional unloading of the compressor.

With the present invention, the re-positioning means will, within a predetermined time, always re-position the step control operating'means to its original position, thereby permitting operation of the compressor at partial capacity within the same pressure limits as 'at full load or capacity.

Another object of "the invention is to provide in combination with an air or gas compressor, an

instrument or governor which will hold an average pressure on a system by varying compressor capacityand re-position the governor limits after each successive step in the loading or unloading of the compressor.

In some systems or compressor installations where the receiver system is particularly large or the rate of variance of compressor capacity,

that is, the lag of each step of variance oi. compressor capacity, is particularly small, there may T NT: b -"F C f be suflicient time lag or delay between the change Y in capacity of the compressor and the pressurein the receiving system so that the restoring; of the pressure limits in'the governor mechanism would cause successive operations thereotthat were not actually in accordance with capacity demands. This would mean that the instrument or governor would be operating or swinging through two or three steps of capacity varying operation when only one step would be required to accommodate or compensate for the pressure change or the increase or decreasein the demand tor airor gas in the system.

Therefore it is an object of the present invention to provide, in a variable capacity compressor and its control, means which controls the restoratlon feature of the bias return of the instrument or governor which will delay the action of the resetting or bias return for one step, two steps, any desired number of steps or even for the entire range of the instrument or governor, thereby providing a simulation of the action of overnormechanisms in present use in which pressures are for the second step, etc., through the entire range of loading and unloading of the compressor, without requiring such pyramiding of pressures.

By delaying the re-setting or bias return of the instrument or governor the limits between steps of operation of the governor and consequently thefractional unloading or loading of the compressor are reduced, thereby narrowing the differentialand holding the pressure output more nearly at demand, than would be provided if such delay of the resetting or bias return were not provided. For example, if one-half pound pressure variance would cause the instrument or governor to change the capacity of the compressor one step or one predetermined fractional portion of its capacity, and there was a delay in the reaction of this change in the reservoir system and the present elements of the instrument were returned to their original position by the return action, that same half-pound pressure variance would c use the instrument or governor to move through another step of operation. Such action is prevented by the present invention.

Other objects of the present invention are to provide in a variable capacity compressor and its control instrument or governor, a mechanism which is positive in operation, provides automatic initial unloading of the compressor, embodies a compressor capacity indicator whereby the percentage of full capacity at which the compressor is operating may be readily ascertained at all times, embodies a demand limiter or capacity selector whereby the mechanism maybe set to cause operation of the compressor at any predetermined percentage of its full capacity, beyond which set percentage of capacity the compressor will not go; a mechanism which is responsive to time as well as pressure variances; embodies ad-' justable differential means whereby the differential in pressures required to load or unload the compressor in steps may be varied as desired, and one which readily lends itself. to con:-

trol from a remote point.

With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a variable capacity compressor embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

v In the drawings:

Figure 1 is a plan view of the improved governor mechanism for a -variable capacity compressor.

Figure 2 is an end elevation of the governor. Figure 3 is an end elevation of the governor showing the end opposite to the one shown in Figure 2. Figure 4 is a longitudinal section through a part of the governor taken on the line 4-4 of- Figure 1.

Figure 5 is a detailed section of a part of the governor taken on the line 55 of Figure 1 and showing the contact making and brealdng mechanism in elevation.

Figure 6 is a detailed section on the line 6-6 2111 Figure 1 showing part of the resetting mecha- Figure '7 is a section on the line |-'I of Figure 1 showing a part of the operating mechanism for the contact making and breaking cams.

Figure 8 is a detailed side elevation of the demand limitator mechanism.

. Figure 9 is a detail in plan of the limitator mechanism.

Figure 10 is a detailed plan view of the demand limitator cam.

Figure 11 is a diagrammatic lay-out of the demand limitator cam.

Figure 12 is a detailed section taken on the line l2--l2 of Figure 1 and showing the power connecting mechanism.

Figure 13 is a detailed section on line l3-l3 of Figure 1 showing the step-by-step cam.

Figure 14 is a detailed view of the resetting cam and lever.

Figure 15 is a-front cam.

Figure 16 is an edge view of the resetting cam.

Figure 17 is a section through the resetti Figure 18 is an edge view of the resetting cam elevation of the resetting showing it in one adjusted position.

Y that shown 2,181,978 camshowlng it in the adjusted position illus- Figure 22 is a vertical section through the pres-- sure operated mechanism and taken on the line 22--22 of Figure 1.

Figure '23 is a horizontal section through the pressure operated mechanism and taken on the line 23-23 of Figure 22.

Figure '24 is a detailed view partly in section of a solenoid operated valve employed. in the variable capacity compressor, control. 1

Figure 25 is a view partly in section and partly in elevation of the solenoid valve and taken at right angles to the view shown'in Figure 24.

Figures 26, 27 and 28 are a series of graphs illustrating the phases of operation of the variable capacity compressor. Figure 26 shows a curve or graph of the loading or unloading of of a variable capacity compressor constructed in accordance with the present invention.

Figure 29 is a diagrammatic View illustrating the variable capacity compressor and governor arrangement.

Referring more particularly to the drawings, and with particular reference to the diagrammatic-Figure 29, a multi-cylinder compressor is shown comprising a low pressure cylinder I and a high pressure cylinder 2. These compressor cylinders are loaded and unloaded in predetermined fractional percentages of their capacity by the various control valves 3, 4, 5, 6, I and 8. While, in the drawings, the loading and unloading of the compressor cylinders is illustrated as being provided through the medium of holding open suction valves which are indicated as the control valves 3, 4, 5 and 6 and by opening the clearance pockets 9 and I0 through the medium of the

control valves

1 and 8 respectively, it is to be understood that the improved control or governor mechanism forming the present invention may be employed in connection with any approved type of.control or unloading valves and with any approved system of unloading such as the one illustrated in Figure 29 of the drawings, or other approved types employing onlyunloader control valves or various combinations oi-unloaderor control valves as shown, for instance, in Patents Nos. 1,636,439; 1,704,343; 1,579,781; 1,579,782;

1,764,646, and others.

In Fig. 29 of the drawings the various control valves of the cylinders l and 2 are shown connected in pairs as, for instance, the control valves 3 and 5 are connected to each other and to the solenoid operated distributor valve structure l4 through a pipe IS. The valves 4 and 6 are connected together and through the pipe Hi to the solenoid operated distributor valve I7, while the valves 1' and 8 are connected through the pipe l8 with the solenoid operated distributor valve l9, thus the valves will operate in pairs to simultaneously load and unload both the low pressure cylinder I and the high pressure .cylinder 2 in the same predetermined percentage ofcapacity of the cylinders.

The solenoid operated valves l4, l1 and I!) are all similar in construction and may be of any approved type of solenoid operated valve applicable for performing the work. One such construction of solenoid operated valve is shown in, detail in Figures 24 and 25 of the drawings.

Each of the distributor valve structures c'omprises a solenoid 20, the core 2| of which is connected by means of a rod 22 to the pivoted valve operated lever 23. The valve operating lever is pivotally supported as shown at 24 and contacts the valve operating pins 25 and 25 which in turn engage the valves 21 and 28 respectively for unseating the valves. The valves 21 and 28 are seated by springs 29 when the pressure of the lever 23 is relieved therefrom.

When the solenoid 20 is de-energized, the dropping of the core 2| will move the lever 23 into the position shown in Figure 24 of the drawings at which time the pressure fluid valve 21 will be seated, cutting oif the flow of pressure fluid as vented from the control valves which are connected to the respective solenoid operated valve, and the valve 28 will be unseated.

Pressurefluid from any suitable source, preferably either the suction line of the compressor system or from the receiver into which the fluid compressed is delivered, is delivered to the solenoid operated valve structure through a pipe 30* and enters the valve structure through the port .34. When the valve 28 is .open or-unseated the pressure fluid will flow through the solenoid operated valve structure into the chamber 32 therein, outwardly through the port 33 into any one of the pipes l5, I6, or I8, to which the respective valve is connected, for supplying pressure fluid to noid 20 of the valve structure I4 is de-energized through the medium of the governor mechanism, as will be hereinafter fully described, pressure fluid passes from the pipe 30 through the solenoid operated valve structure and pipe l5 to the control valves 3 and 5, operating these control valves and rendering the crank ends of the 'cylinders l and 2 non-compressing, thus unloading the crank ends and causing the compressor to operate at 50 per cent of its capacity.

When the solenoid 20 is energized, the core 2| thereof will rise, allowing the spring 29 to seat the valve 28 andcut off the delivery of operating pressure fluid to the valves 3 and 5, or such other of the control valves as are connected'to the solenoid de-energized. When the core 2| rises it will open the valve 21 and will connect the control valves through the port 33, chamber 32, to the exhaust or bleed-oil port 3 I, allowing the pressure fluid to bleed from the control valves and the trolled by the respective affected control valves.

The port 3| may either open to atmosphere, or it may be connected to the suction line-of the compressor system if it is so desired, this depending upon the type of fluid being compressed.

The specific construction of the control valves 3, 4, 5, s, 1 and a will not be described in the present application since they are relatively well known and their specific construction is-illustrated and described in the prior patents hereinabove mentioned, and it is to be understood that the present invention is not limited to any particular type of control valve, but any of the many types of compressor loading and unloading control valves now in use may be employed in the carries the' contact bar 54.

present invention without departing from the spirit of the invention. The present invention comprises a novel arrangement of various mechanisms, both pressure and electrically operated, for controlling the energizing of the solenoids 28 of the various distributor valves, for timing the period of energization of such solenoids, and for operating the control mechanism in such manner as to make it highly sensitive to variations or differentials in either receiver or suction pressure, and to the demand on the compressor, so that the loading and the unloading steps of the compressor may be efiected with much narrower or reduced difierentials than has been possible with the use of approved types of compressor governor mechanisms. For instance, in the various approved types of compressor unloading control governors and sys-' terns heretofore in use, a differential or variance of approximately two pounds is required to effect successive steps of loading or unloading the compressor cylinders and these variances build up or pyramid, whereas in the present variable capacity compressor and control governor therefor .the

efiecting of such successive steps of loading or un-' "loading-on a difierentialor variance of approximately one-half pound or 'evenless in the pressure ,of fluid compressed will be permitted, and in' lieu of such variances pyramided to require the succes'sive steps, the present mechanism will effect the successive steps on successive difierentials of equal degree.

One end of the circuit or each of the solenoid valves l4, l1 and I9 is connected with the line LI of the main current supply and the other ends of the coils of the solenoids are connected through suitable wires with contact points on the I anism. Electrical circuits are completed through the. solenoids by

contact levers

41, 48, 49 and 50,

which bridge or connect the contacts 4| and 4l',

42 and 42', 44 and 44', and 46 and 46'. The con tacts 4 l 42', 44 and 46' are connectedto the line 11-2 of the main electrical current supply.

The specific construction and mounting of the circuit closing contact levers is illustrated in Figbe described in connection with the lever 48, but it is to be understood that all of the levers are similarly constructed and mounted. The lever 48 is carried by an arm 5|, which is pivotally supported on the supporting base 52 of the governor mechanism as shown at 53. For the purpose of insuring proper contact, a contact bar 54 is connected to the lever 48 by a bolt 55 on which the bar 54 is -ure 5 of the drawings, wherein the contact lever 48 and its cooperating mechanisms are illustrated. The specific construction of the contact levers will slidably mounted. The bar 54 is urged into contact making position by a spring 56, and the contact lever 48 is also urged into contact making positionby means of a spring 51 which engages the end of the lever 48 opposite of its connection with the pivoted arm 52 from the end which The lever 48 is moved out of contact making position by means of a cam 58, which engages a cam roller 59 carried by the outer free end of the pivoted arm 5 l. Cams 60, 6|, and 62 are provided for operating the contact, levers 58, '41, and 43 a the second shaft. therethrough is merely an ex-' The cams 58, 88, 6| and 82 are carried by a shaft 63, which is shown in the drawings, with theexception of the diagrammatic Figure 29. as a hollow shaft which receives therein a second shaft,- hereinafter referred to specifically. The making of the shaft 63 hollow and the extending pedient to consolidate the governor mechanism and render it more compact, so that this shaft 63 need not be a hollow shaft in so far as'the spiri of the present invention is concerned.

The hollow shaft83 is rotatably supported in suitable bearings 64, carried by the supporting base, 52 of the governor mechanism and it has a gear 65 mounted thereon which meshes with the pinion 66 of the differential gear mechanism 81. The pinion 66 is carried by the disk 68 of the differential gear mechanism, which disk is rotatably mounted on the shaft 63. In the drawings, with the exception of the diagrammatic Figure 29, a shaft 69 is shown as extending through the hollow shaft 63 for the purpose of compactness in the construction of the governor, but if expedient this shaft 69 may be placed in any suitable position, in

proper relation to the shaft 63. The disk 68 has a gear 18 thereon which meshes with a worm 1I. This worm 1I is car ried by a shaft 12 which has a bevel gear 13 thereon. The beveled gear 13 is adapted to mesh with either one of the bevel gears 14 or 15, which are carried by the shaft 16. The shaft 16 is connected by an 'expansive' spring clutch 11 with the shaft 18. The shaft 18 is connected by suitable gearing 19 with the operating motor 88 of the governor mechanism in such manner that the shaft 18 will rotate continuously during the operation of the motor 88.

a shaft in a reverse direction releases the contact. levers from the restraint of the cams and permits v The bevel gears 14 and 15 are rotatably mounted on the shaft 16 and they are always in mesh with the gear 13.- The bevel gears 14 and 15 are rotatably connected to the shaft 16 by means of clutches BI and 82'. Either the gear 14 or 15 is rotated with the shaft 16 depending upon the direction of movement of the shaft 16 against the spring 82 of .the clutch 11 or the spring 83 which engages the opposite end of the shaft. The shaft 16 is either held in neutralposition as shown in Figure 29 of the drawings, at which time the disk .88 is stationary, or it is forced to the right, thereby connecting the gear '15 with the shaft 16, or forced to the left, thereby connecting the gear 14 to the shaft through the medium of the pin 8I.

the springs 51 to act to close the circuit through the respective contacts. The

cams

58, 68, 6| and 62 are set on the shaft 63.at different angles so as to provide the proper sequence of operation of the various contact levers'to provide proper sequence control of the loading and unloading of the compressor. A stop cam 84 is mounted on the shaft 63 and has a plurality of arouate indentations or serrations 85* in its circumference. A pivoted arm 86 is pivotally supported from the supporting base 52, as shown at 81 in Figure 13 of the drawchanging the 2,181,978 I ings, and it has a roller 88 on its outer free end which engages in any one of the notches or serrations 85 to provide a stop to preventhunting movement of the governor mechanism. The pivoted arm' 86 is urged into stop relationship with the stop cam 84 by a spring 89, which is connectedto the pivoted arm 86. The spring 89 is tensioned to cause the roller 88 to be urged against the perimeter of the cam 84 with sufficient strength to provide a brake or stop to prevent over-run of the shaft 63,,the tension of the spring 89, however, being such that upon they starting of operation of the governor mechanism and rotation of the shaft 63 the shaft will be. permitted to move at least one step, or suflicient distance to provide one step in the unloading of the compressor.

The shaft 18 has a crank pin 98 thereon which is connected to a kick rod 9I The kicking rod 9| is connected to a yoke 92. The-yoke 92 oscillates back and forth, pivoting -or rocking on a bearing 93 on the shaft 63. The yoke 92 has two

dogs

94 and 95 pivotally mounted thereon, connected by a spring 96 at their free ends and normally held in a neutral position by a leaf 91, which is rockably mounted on the shaft 63. The leaf-91 carries two

pins

98 and 99 which engage the cam surfaces I88 of the

dogs

94 and 95 respectively, and hold the two dogs out of operative position. The leaf 91 has an extension I8I thereon which swings through a given are, being re-' positioned at the end of each stroke by engagemoved into and out of stopping position as will be hereinafter described. Notches I82 and I83 are provided in the carrier member I3I to permit normal swinging movementoof the leaf 91 through its complete path. The leaf 91 is mounted in relation to the yoke 92 to provide suiiicient friction to move the leaf with the rocking of the yoke but to'permit limited movement of the leaf independently of the yoke if the extension I8-I of the leaf engages the stops or other means stop or limit its movement. If the extension IN is not allowed to travel through its entire stroke the leaf 91 will stop but the yoke 92 will continue its movement, thereby allowing

eitherthe pin

98 or 99,, depending upon whichdirection the yoke I is moving when restriction is applied to the'leaf 91, to be displaced with respect to the

dogs

94 and 95. If the pins are displaced a dog will then drop, for example, into the position shown at the left hand side of Figure '1 of the drawings, and

on the return stroke of the yoke 92 the dog, which has dropped, will engage the ratchet wheel I84. The ratchet wheel I84 is keyed to or rigidly carried by the cam shaft 63, so that the movement of the yoke 92, with the dog 94 or the dog 95 engaging the ratchet I84 will crank or turn the shaft 68 a definite number of degrees. thereby positions of the cams 58. 68. 6i

and 62. I

The restriotionor stopping of the leaf 91 is caused by the "n'iovement into its path of one or the other of the stopsI86 or I81. movement of which is controlled by. the pressure operated mechanism I88.

The pressure operated mechanism I88 includes a diaphragm I 89, which extends across the interior of a suitable housing H8, which is connected through its inlet III to the source of prespressor. That is,'.the diaphragm I89 may be acted upon either by receiver pressure or by the 76 arc ers The diaphragm I09 has a pin I I2 carried thereby which projects out of the casing H and engages the plate structure H4. The plate structure II4 has a pair of flat springs II6 connected thereto which are in turnconnected to posts I I6. A pin H1 is carried by the plate structure '4 near the end opposite to the end at which the clearly shown in the diagrammatic Figure 29;

posts II6 are located. A spring II8 is connected to the pin II1 so that the plate structure H4 is yieldably suspended by the action of the springs H5 and H8 for rocking movement under action of the diaphragm I09 through the medium of the pin H2. The tension of the spring H8 and consequently the adjustmentof the pressure operated device for operation by different degrees of pressure is provided by the adjustment of the spring carrying collar II9 along its screw-threaded supporting column I20. The column I20 is rotatably supported by the supporting structure 'I 2 I which also serves to prevent rotation of the spring carrying collar II9.

An arm I23 is rigidly attached to the plate structure H4 and projects laterally therefrom. The arm I23 has a'plurality of spaced openings I24 in its outer projecting end, any one ofwhich is adapted to receive the reduced end I25 of the connecting arm I26 (see Figure 7). The arm I26 is adjustably mounted on the lower end of the cross member or lever I21. Thecross lever I21 is pivoted on the rod I28 of the rocking bracket I29.

The upper or forward end of the cross lever I21 has a pin I29 carried thereby which engages the periphery of the cam I30 mounted on the shaft 69. The bracket I29 is pivotally carried by the structure I3I and it. has a plate I32 carried thereby. The plate I32 carries pins I33 and I34 disposed on opposite sides of its pivot which engage and actuate the pawls I06 and I01 respectively.

The pawls I06 and I01 are rockably supported by the member I3I and they are moved by rocking.

movement of the cross-lever. I21 upon'variances I in the pressure of fluid delivered againstthe diaphragm I09, to control movement of the leaf- 91,

pawls

94 and 95, and consequently the positioning of the

cams

58, 60, GI and 62. The cross lever I21 is held with the pin I29 engaging the periphcry of the cam I30 by the spring I36.

The shaft 69 has a resetting or elevationvcam I38 on its end opposite tothe cam I30. The .cam I38, which controls the resetting of the governor mechanism, is shown in detail in Figures 15 to 21 inclusive of the drawings, and in association with the lever 84 in Figure 1-1 of the drawings. 7 The shaft 69 is connected to the shaft- 16 through the differential gearing structurefl, as

compressor, or in other words, it is adjustable' to vary the timeof the resetting or biasing of the governor mechanism.

The cam its includes the hub m which is v rigidly connected to the gear I39, and is pinned on the shaft 69 by a set scre'wshown at I42, so as to permit adjustment of the position of the cam onthe shaft. Thehub portion I of thecam has a segmental flange I43 on its outer end, which is ofl-set laterally from the end face of the hub- I4I of the cam and provides an angled shoulder I44, which forms a step for operating the lever 64. The cam I38 also includes the adjustable ring I45 which is rotatably mounted on the hub I of the cam. The ring I45 is held in adjusted positions by means of a suitable set screw shown at ,I46. The ring I45 has an annular flange I41 formed thereon which flange has a laterally offset portion t48 encompassing substantially half its area. The laterally oiI-set portion I48 forms a shoulder I49 which is tapered similar to the taper of the shoulder I43 and provides an abutment or shoulder over which the end of the lever 84 rides for rocking the lever. By adjusting the position of the shoulder I49 on the adjustable ,ring of the cam in positions as shown in Figures 18 to' 21 inclusive, it will be apparent that, the

. time of operation of the lever 84- during the rotation of the shaft 69 may be varied: either advanced or delayed, depending upon the time delay desired in the resetting or biasing of the governor control mechanism.

The lower end of the cross-lever I21 is provided with a plurality of spaced openings I21 which permit of various adjustments in the connection between the bar I26 and the lever. The series of openings I21 and I24 permit a relatively wide range of adjustment between the connection of the lever I21 and the movable arm I23 for regulating the scope of movement of the cross lever I21 as necessary or .desired.

The lever 84 has a cam roller 84 thereon for engagement with the cam I 38.

The shaft 63 has a visible indicator I50 mounted thereon and rotatable therewith which shows the percentage of capacity at which the compressor is operating.

The varying of the time for restoring or resettingaction is accomplished by the shifting of the sections of the cam I38. Byshiftingthe sections of the cam I38 the time .at which the shoulders I44 and I48 engage the lever 84 for rocking it is varied so that the shifting or engagement of the sections of the clutch 82' is varied. The rotation of the cam I30 depends upon the connection of the gear 15 with the motor and consequently by varying the time of icoupling the gear 15 to the motor shaft 18 and the resultant operation of the shaft 12 the time required for restoring or resetting the mechanismmay be-vari'ed.

The present variable capacity compressor control mechanism embodies means in the form of a demand limitator which is manuallyset to regulate or determine the maximum out-put of the compressor. That is, if theexisting conditions are such that it is desirable to confine the maximum out-put of the compressor to 50 per cent, or perhaps 75 per cent of its maximum capacity, then the demand limitator structure may be set so that when the governor has once unloaded the compressorbelow the degree indicated by the setting of the demand limitator, the governor mechanism will operate to further unload the compressor and will continue to function in the usual manner, except that it will never reload above the setting of the demand limitator.

The demand 'limitator structure includes a dial I6I, which is rotatably' supported by a suitable supporting structure I52 and has a finger knob I53 thereon to facilitate its adjustment. The dial I6I has a seriesof notcheslflcut-in its periphcry which have suitable indicia I66associated pin I60 at its end opposite to the end which engages the cam I61. The pin I60 is held in 'engagement with the lateral stepped face I6I of. a cam I62 by means of a spring I63. The cam I62 has a plurality of steps or shoulders I 64 formed on itsface which are engaged by the pin I60.

The shoulders I64 correspond to the indicated percentages of capacityiii on the dial I6I.

- The cam I62 is rotatablymounted on the shaft 63 for limited rotary movement relative thereto, by means of a spring coupler structure I61, which is of approved construction. The cam I62 has a second cam I66 formed integrally therewith whichis of the same diameter as the ratchet or star wheel I 04, and abuts the cam I04. The cam I04 has a series of notches I66 in its perimeter as well as having shoulders I10 formed thereon. The notches I66 and shoulders I10 are engaged by the

pawls

64 and 66 for turning the shaft 63 and positioning the

cams

66, 60, 6I and 62 to control the degree of unloading and loading of the compressor and to cause rotation of the shaft 63 and the consequent setting of the cams either the

pawl

64 or 66 must engage in one of the notches I66 or against one of the shoulders I10. In the lay-out Figure 11 the projected peripheral spaces "I of the ratchet or star wheel I04 are indicated with the various degrees of capacity of the compressor. The cam I66 has a pair of peripherally extended portions I12 and I13 formed thereon, the outer surfaces of which align with the outer surfaces of the peripheral extensions "I of the ratchet or star wheel I04.

The spring coupling I61 is such that it will connect the cams I62 and I66 to the shaft 63 for rotation therewith until an obstruction is presented to arrest rotation of the cams I62 and I66, such as the contact of the pin I60 with one of the shoulders I64, at which time movement of both the cams I62 and-I66 with the shaft'63 will be arrested. The point or position of thesevcams upon the arresting of their movement relative to the shaft 66is determined by the positioning of the. pin I60 through the adjustment of the lever I66 by the cam I61. The positioning of .the cam I61 is controlled by the manual rotation of the dial Iii, so that il'theydlal lil is rotated I to position where the notch I64 represented by the indicia 16 receives the springstop I66, this means that the maximum loading of the com- -pressor atsuch time will be '15 per cent of the capacity of the compressor, and the lever I66 will be adjusted so that the pin I60 will engage the corresponding step or shoulder I64 to arrest rotation of the cams I62 and I66 with the shaft 63 when the peripheral extension 2 on the perlphery of the cam I66 is in position to prevent the

dogs

64 or 66 from engaging either the shoul der I10 or the notch I66 in the ratchet or star wheel I04 to rotate the shaft 63 for adjusting the position of the

cams

66, 60, 6I or 62 to permit loading ofthe compressor to 100 per cent of -its capacity, and thus the maximum operating capacity of the compressor at such adjustment will be limited to 75 per cent and when the output demand is less than this 75 per cent capacity or when the pressure reaches a predetermined detact lever 60, de-energizing alarms gree corresponding thereto, the compressor will 4 start to unload. The indicator disk I60 on the system hereinabove described is primarily a system or instrument which holds an average pressure on a systemv by varying compressor capacity and repositioning the governor limits after each successive step. However there may be instances or particular applications wherethe compressor receiver system is particularly large, and the rate of variance of the compressor capacity is par ticularly small, there may be suflicient lag between the change of the compressing rate and the pressure in the system so that the restoring of the pressure limits in the governor would cause successive operations thereof that were not in accordance with the capacity demand, resulting in unnecessary step operations of'the governor.

By adjustment of the cam I66, the restoration or resetting action of the governor mechanism may be delayed one step, two steps, or for the entire range of thegovemor, which results in operation of the present mechanism in simula-' tion of the action of compressor governors of approved types now in use. as shownby Figure 26 of the drawings. That is, the pressure differences required for each step operation of the governor are allowed to pyramid, so that if one-half pound pressure change is required for the first step operation of the governor, an'additional' one-half pound will be required for the second step operation, etc..throu'gh the entire range of the governor.

Ordinarily, in the operation of the present governor, if one-half pound in pressure variance will cause the governor to change the output capacity of the compressor one step, and the cam I30 and the co-operating parts are restored to their original position or reset, then; the same onehalf pound pressure variance will cause a successive step operation of the governor mechanism. Thus the pressure differential is narrowed. This action is shown inglgure 27 of the draw- Referring to Figure 28 of the drawings, A and B represent the governor limits or points at which the step operations of the governor takes place, and P represents the receiver or suction pressure, or in other words, the pressure source, variation. of which effects unloading and loading of the compressor cylinders I and 2.

If the compressor cylinders I and 2 are operating at 100 per cent of capacity and the controlled pressure risesso that it reaches the limit represented by the line A, the pressure operated mechanism II4 will move the arm I26 and operate the cro'ss lever I21. The operation of the cross lever I21 will rock the rocker bracket I26 and move the stop pawl I01 into the path of the extension IOI on the leaf 61, arresting movement of the leaf 61 while the yoke 62 continues its stroke. The arresting of movement of the leaf 61 will cause the pawl 64 todrop and engage one of the shoulders I10 on the ratchet or star wheel I I04 and rotate the shaft 66 by movement ofthe yoke 62. This movement of the shaft 63 will cause depression of the circuit closing conthe solenoid of the valve I6 and resulting in operation of the control valves 1 and 6 andthe consequent reduction of output capacity of the compressor cylinders I and 2, per cent, permitting operation'of the comthe shaft I8 willstart the operation of the dif- 'ferential gear mechanism which will slowly pressor cylinders at per cent of the maximum out-put capacity of the cylinders. I

As the governor takes this first step, the cam I30 will reposition the cross lever I21 leveling off the rocker bracket I29, moving the stop pawl I01 out of the path of the extension IOI of the leaf 91, repositioning these parts for an additional step or operation. At this point the differential gearing 81 returns the cam I30 to its original position, although should the pressure in the control source not change in the interval,

the cross lever will again be operated and cause a second step operation of the governor with the resultant change in the out-put capacity of thecompressor cylinders 'I and 2'.

If, however, the pressure is dropping, the diaphragm I09 will allow the cross lever I21 to return to its original position so that by the time the cam I30 has returned to its original position, the leaf 9'I will be permitted uninterrupted movement through its arc and no governor action will be set up.

Should the pressure in the source decrease sufficiently so that it reaches the lower limit indicated by the line B, the same action is set up,

except that the direction of movement of the cross lever I2! is reversed, and the'stop pawl I06 is brought into position to arrest movement of the leaf 91, causing the pawl 95 to engage the ratchet or star wheel I04 and operate the shaft 83 in a reverse direction, to make the circuit through the solenoid 20 of the valve structure I9, allow the pressure operating fluid to bleedfrom control valves I and 8 through the port 3| of the valve structure I9, with the resultant loading of the compressor cylinders.

The above same operations are repeated re-' gardless of the percentage of out-put capacity at which the compressor cylinders are operating. The shaft 69 is geared to the shaft 83 through the differential gearingi'l so that as the shaft 83 is operated by either of the pawls 94 or 95-the shaft 69 will be correspondingly rotated, which rotation will move the cam I38, causing the roller 84 to move from the neutral position on the cam I38, and rock the lever 84. The rocking of the lever 84 will move the shaft I6, and cause either the clutch 3| or 82' to engage its respective gear I4 or IE, dependii'igupon whether the pressure in the control source is increasing or decreasing. The connecting of one of the gears I4 or I5 with change the relative positions of the

shafts

83 and 69. The shaft 83 however is held against rotation, under the small amount of power transgearing must move the'shaft 89, which movement restores the cam I30 to its original position.

From the foregoing it will be apparent that the unloading is effected by successively de-ener- I gizing solenoids in control of pressure fluid means for operating the unloading means. Energizing of the solenoids is controlled by switch levers. 41-30 which are operated by cams 88 to 82 on shaft 83.

The motor operates continuously and oscillates yoke 92 by means of rod 9|. Whenthe receiver pressure rises above that desired pressure fluidacts against diaphragm I09. This diaphragm-acts through pin 2, plates II4, I23 to rock I21 counter clockwise (Fig. 7) to-move stop I01 into the path of the leaf ML The yoke 92 may then move relative to the leaf. III so that the pafwl'94 drops down as shown in Fig."7- and engages the periphery of the ratchet wheel I04 and turns the shaft 83 to cause one of the cams 58 to 62 on the shaft 33 to operate one of the solenoids. Rotation of shaft 63 operates through gears-85, 66, I40 and I39 to turn shaft 89 and cam I 30 to turn lever I2'I= clockwise towards its original'position and move I0I away from the leaf IOI, so that the spring 96 again may raise the pawl 94 from ratchet wheel I04 to center the leaf IOI with the yoke 92.

I Rotation of the shaft 69 causes the cam I38 to move the lever 84 and release spring 83 so that spring 82 moves clutch 8| into engagement with gear I4. During this time shaft 83 is held against,

rotation by engagement ofroller 88 in recess 85' of cam 84 (Fig-13). Motor rotates gear I3 and shaft 69 in the opposite direction to return is-varied by adjusting hub I on shaft 89 and a ring I45 on hub. I4I (Figs. 15-21).

The indicator I5I on shaft 63 shows at what Y percentage of its full capacity the pump is operating,

The pressure at which the unloading is efiected is adjusted by sleeve H9 and screw I20.

It will be understood that the invention is not to be limited to the specific construction or' arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What-is claimed is:

1. The combination with air or gas compressor, of control valves on said compressor for controlling the loading andunloading of the compressor in fractional parts of its full capacity, means for controlling operation of said control valves, pressure responsive means for operating said valve control means, means for automatically re-setting saidvalve control means after each operation whereby the compressor will operate at the same discharge pressure irrespective of the percentage of its full capacity at which it is operating, and a manually operable demand limiter embodying a plurality of stops brought selectively into or out of stopping a variable capacity relation with said control valve controlling means for regulating the maximum percentage of capacity at which the compressor'can operate.

2. The combination with a variable capacity air or gas compressor, of control valves on said r compressor for controlling the loading and. un-

loading of the compressor in fractional parts of its full capacity, means for controlling operation of said control valves, pressure responsive means for operatingsaid valve control means, means for automatically re-setting-said valve control means after each operation whereby the compressor will operate at the same discharge pressure irrespective of the percentage of its full capacity at which it is operating, adjustable meansv for momentarily delaying the return of the valve control operating means to allow the change effected by-operation of the control valves to be come effective in the receiver system of the compressor before a successive operation of the control valve operating means is permitted, and a demand limiting device embodying a plurality of stops brought selectively into or out of stopping 8 relation with said control valve controlling means for. regulating the maximum percentage of capacity at which the compressor can operate.

3. The combination with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and unloading of the compressor in fractional parts of its full capacity, means for controlling operation of said control valves, pressure responsive means,

for operating said valve control means, means for automatically re-setting said valve control means after each operation whereby the compressor will operate at the same discharge pressure irrespective of the percentage of its full capacity at whichit is operating, means for momentarily delaying the return 01' the valve control operating means to allow the change eflfected by operation of the control valves to become effective in the receiver system of the compressor before a successive operation of the control valve operat- 'ing means is permitted, said delay means including a'cam comprising relatively adjustable sections adjustable to regulate the time interval of the delay. I

4. The combination with a' variable capacity air or gas compressor, of control valves on said compressor for controlling the loadingand unloading of the compressor, electrically operated means for controlling'operation of said control valves, said electrically operated means comprising means responsive to deviation from a predetermined pressure for controlling operation of the electrically operated means, means for varying the setting of said responsive means, means for re-positioning said control valve operating means after'each operation, and means controlling connection of said repositioning means and said electrically operated means for momentarily delaying the repositioning of said control valve operating means to allow the change eflected by operation of the control valves to becomeeiiective in the receiver system of the compressor before a successive operation of the control valve operating means is provided.

5. The combination with a variable capacity air or gas compressor, of control valves on the compressor for controlling the loading and unloading of the compressor, solenoid operated dis-- tributor valves for controlling admission of operating pressure fluid to said control valves, sole-- 6. The combination with a variable capacity air or gas compressor, of control valves on said compressorwfor controlling the loading and unloading of the compressor, electrically operated means for controlling operation of the control valves, means responsive to deviation from a predetermined pressure for controlling operation of said electrically operated means, means for varying the setting of said responsive means through a series of predetermined positions, means-tor restoring the responsive means to its original setting, and means controlling connection of said repositioning means and said electrically operated means for momentarily delaying the return of the responsive means to its original setting.

7. The combination with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and unloading 01 the compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts,- cams for moving said contacts into and out of circuit closing position, a -prime mover, astep by step cam for rotating said contact moving cams, means operated by said prime mover for rotating said step by stem cam, said prime mover operated means being normally out of cam moving enagement with the step by step'cam, and pressure 0 perated means for moving said prime mover operated means into cam rotating engagement with said step by step cam.

. s. The combination with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and unloading of the compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts, cams ior moving said contacts into and out of circuit closing position, a prime mover, a step by step cam for'rotating'said contact moving cams, means operated by said prime mover for rotating said step by step cam, said prime mover operated means being normally out of cam moving engage- I ment with the step by step cam, pressure operated means for moving said prime mover operated .means into cam rotating engagement with said step by step cam, and means for re-positioning said pressure operated means after each operation thereof.

9. The combination with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and un loading oi. the compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts, cams for moving saidv contacts into and out of circuit clos-, ing position, a prime mover, a step by step cam for rotating said contact moving cams, means operated by said prime mover for rotating said step by step cam, said prime mover operated means being normally out of cam moving engagement with the. step by step cam, pressure operated means for moving said prime mover operated means into cam rotating engagement with said step by step cam, means for repositioning said pressure operated means after each operation thereof, and means for delaying the re-positioning of said pressure operated means.

10. The combination with a variable capacity air or gas compressor, of control valves 'on said compressor for controlling the loading and unloading of the compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts, cams for moving said contacts into and out of circuit clos ing position, a prime mover, a step by step cam for rotating .said contact moving cams, means operated by said prime mover for rotating said step by. step cam, said prime mover operated means'being normally out of cam moving engagement with the step by step cam, pressure operated means for moving said prime mover operated means into cam rotating engagement with said step by step cam, and a demand limiter iricluding means for rendering certain steps of the step by step cam inactive for regulating the max operation of said control valves including mov-.

able electric-circuit closing contacts, cams ior angers imum percentage of the full capacity at which the compressor can operate.

11. The combination with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and unloading of the compressor, means for controlling operation oi said control valves including movable electric-circuit closing contacts, cams for moving said contacts into and out of circuitclos ing position, aprime mover, a step by step cam for rotating said contact moving earns, a rocking yoke operated by said prime mover, pawls on said yoke {or rotating engagement with said step by step cam, and pressure operated means for moving said pawls into cam rotating engagement with said step by step cam. r

12. The combination with a variable capacity air or gas compressor, or control valves on said 7 compressor for controlling the loading and unloading of the compressor, means for controlling operation of said control valves includingmovable electric-circuit-closing-contacts, cams for moving said contacts into-and out of circuit closing position, a prime mover, a step by step cam for rotating said contact moving cams, a rocking yoke operated by said prime mover, pawls on' said yoke for rotating engagement with said step by step cam, and pressure operated means for moving said pawls into cam rotating engagement with said step by step cam, said pawls arranged one to rotate the cam in one direction and the other to reverse the direction of rotationv of said cam, said pressure operated means acting under pressure difierences to control the direction of rotation of the step by step cam.

13, The combination with a variable capacity air or gas compressor, of control valvesfor controlling the loading and unloading oi thecompressor, means'controlling operation of said control valves including a step by step cam, means for rotating said cam in steps, and a demand limiter including means'for rendering certain ot the step operations of said cam inactive.

14. -The combination with a variablecapacity' air or gas compressor, of control valves on said compressor for controlling the loading and unloading of the compressor, means for controlling moving said contacts into and out of circuit clos ing position, a prime mover, astep by step cam for rotating said contact moving cams, means operated by said prime mover for rotatimg said step. by stepcam, said prime mover operated means being normally out of cam moving engage-' ment with the step-by step cam, pressure-operated means for moving said prime mover operated means into cam rotating engagement with air or. gas compressor, of control valves on said said step by step cam, and a1 ratchet cam and pawl operated with said contact moving cams for preventing overrun movement of the contact operating cams.

15. The combination with a variable capacity compressor for controlling the ldading and unloading of the compressor, means for-controlling operation of said control valves including movable electric-circuit closing contacts, cams for rocking yoke operated by said prime mover,

pawls on said-yoke for rotating engagement with i said step by step cam, pressure operated means 7 for moving said pawls into cam rotating engagemoving said contactsinto and out of circuit closing position, a prime mover, a stepby step cam for rotating said contact moving cams, a

ment with said step by step cam, a ratchet cam and pawl associated with said contact moving cams for preventing overrun movement of the contact operating cams, and means-tor re-positioning said pressure operated means after each yoke operated by said prime mover, pawls on said yoke for rotating engagement with said step by step cam, pressure operated means for moving said pawls into cam rotating engagement with said step by step cam, a ratchet cam and pawl associated with said contact moving cams for preventing overrun movement of the contact operating cams, means for re-positioning said pressure operated means after each. operation thereof, and means for delaying the re-position- I ing of said pressure operated means.

17. The combination-with a variable capacity air or gas compressor, of control valves on said compressor for controlling the loading and unloading or the compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts, cams for moving said contacts into and out of circuit closing position, a prime mover, a step by step cam vfor rotating said contact moving cams, a rocking yoke operated by said prime mover, pawls on said yoke for rotating engagement with said step by step cam, pressure operated means for moving said pawls into cam rotating engagement with said step by step camp, said pawls arranged one torotate the cam in one direction and the other to reverse the direction of rotation of said cam,

said pressure operated means acting under pressure diilerences to control the direction of rotation of the step by step cam, and a ratchet and pawl associated with'said contact moving cams' for preventing overrun movement of the contact operating cams.

'18." The combination with a variable capacity air or gas compressor, of control valves'on said compressor for controlling the loading and unloading of the compressor, means for controlling operation of said control valves including' movable electric 'clrcuit closing contacts, cams for moving said contacts into and out of circuit closing position, a prime mover, a step bystep cam for rotating said contact moving cams, means operated by said prime mover for rotating said step'by step cam, said'prime mover operated means being normally out of cam moving engagement with the step by step cam, pressure operated means for moving said prime mover operated means into cam rotating engagement with said step by step cam, pressure responsive means for operating said pressure operated means, adjustable means for regulating said pressure responsive means to vary the degree of diilerential pressure demand required to operate the pressure operated means, a re-positioning cam for re-positioning said pressure operated means after each operation thereof,

. 19. The combination witha variable capacity airor gas compressor, of control valves on said compressor for controlling the loading and unloading of the'compressor, means for controlling operation of said control valves including movable electric-circuit closing contacts, cams for moving said contacts into and out of circuit closing position, a prime mover, a step by Step cam for rotating said contact moving cams, means operated by said prime mover for rotating said step by step cam, said prime mover operated means being normally out of cam moving engagement with the step by step cam, pressure operated means for moving said prime mover operated means into cam rotating engagement with said step by stem cam, pressure responsive means for operating said pressure operated means, adjustable means for regulating said pressure responsive means to vary the degree of differential pressure demand required to operate the pressure operated means, a re-positioningcam for repositioning said pressure operated means after each operation thereof, said re-positioning cam being adjustable whereby the time interval of re-positioning may be varied.

20. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, a step by step cam for controlling operation of said valves, means for operating said step by step cam normally out of operative connection with the cam, pressure operated means for operatively connecting said cam operating means and cam, means'forrepositioning said pressure operated means after each operation thereof, and means for delaying the repositioning of said pressure operated means.

21. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, a step by step cam for controlling oper- V ated means after each operation thereof, and

means for delaying the repositioning of said pressure operated means, saiddelaying means including a cam having relatively adjustable sections adjustable for regulating the time interval of the delay.

v 22. The combination with a variable capacityair or gas compressor, of control valves for controlling the loading and unloading of the compressor, a step by step cam for controlling operation of said valves, means for operating said step by step cam normally out of operative connection with the cam, pressure operated means for operatively connecting said cam operating means and cam, means for repositioning said pressure operated means after each operation thereof, means for delaying the repositioning of said pressure operated means, and a demand limitator including means for rendering certain steps of the step by step cam inactive for the maximum percentage of the full capacity at which the compressor can operate.

23. The combination with a variable capacity air or gas compressor, of control valves for con-\ trolling the loading and unloading of the com-= pressor, means for controlling operation of said control valves including. movable electric circuit closing contacts, cams for moving 'saidcontacts into and out of circuit closing position, a prime mover, a step by step camfor-rotafing said contact moving cams, a rocking yoke operated by said prime mover, pawls on said yoke for rotating engagement with said step by step cam, pressure and cam, means for repositioning said pressure 'movement of said step by step. cam after each operated means for moving said pawls into cam rotating engagement with the step by step cam, and stop means associated with said contact moving cams for definitely stopping movement of the cams after each contact has been moved into or 5 out of circuit closing position, T 24. The combination with a variable capacityair or gas compressor, of control valves for controlling the loading and unloading of the com pressor, a step by step cam for controlling operation of said valves, means for operating said step by step cam normally out of operative connection with the cam, pressure operated means for operatively connecting said cam operating means j' operated means after each operation thereof, means for delaying the repositioning of said pres- I sure operated means, and means for stopping step operation thereof.

25. The combination with a variable-capacity air or gas compressor, of control valves for controlling the loading and unloading of the comassociated with said step by step cam for prevent;

ing overrun of movement of the step by step cam upon each step operation thereof.

26. The combination with a variable capacity 30 air or gas compressor, of control valves for controlling the loading and unloading of the compressor, electrically operated means for controlling operation of said valves, cams for controlling the energizing of said electrically operated means, acontinuously operating-electric motor, pressure'actuated means for operatively connecting said motor and cams to operate the cams by the motor, means actuated by said motor for resetting said motor and cam connecting means, and means actuated by said motor'for delaying the resetting of said connecting means.-

27. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, electrically operated means for con-- trolling operation of said valves, cams for controlling the energizing of said electrically operated means, a. continuously operating electric motor, pressure actuated means for operatively connecting said motor and cams to-operatethe cams by the motor, means actuated by said motor fOr resetting said motor and cam connecting means, meansactuated by said motor for delaying the resetting of saidconnecting means, and means associated with said cam to prevent overrun of the cams upon each operation thereof.

28. The combination with-a variable capacity air or gas compressor, of control valves for conmotor, pressure actuated means for operatively 65 connecting said motor and cams to operate the cams by the motor, means actuated by said motor for vresetting said motor and cam connecting means, a starcam operable withsaid cams, and

means co-actifig with said star cam to prevent overrunoperation of said cams. &

29. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, electrically operated means for conconnecting said motor and cams to operate the cams by the motor, means actuated by said motor for resetting said motor and cam connecting means, and means actuated by said motor for delaying the resetting of said connecting means, said delay means including a cam comprising relatively adjustable sections adjustable to regulate the time interval of the delay. 30. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, electrically operated means for controlling operation of said valves, cams for controlling the energizing of said electrically operated means, a continuously operating electric motor, pressure actuated means for operatively connecting said motor and cams to operate the cams by the motor, and a demand limiting device embodying a plurality of stops brought selectively into or out of stopping relating with said cams to regulate the movement ofthe cams and the maximum capacity at which the compressor can operate. v

' 31. The combination with a variable capacity air or gas compressor, of control valves for controlling the loading and unloading of the compressor, electrically operated means for controlling operation of said valves, cams for controlling the energizing of said electrically operated means, a continuously. operating electric motor, pressure actuated means for operatively connecting said motor and cams to operate the cams by themotor, and a manually set demand limiting device embodying a plurality of stops brought selectively into or out of active relation with said motor and cam connecting means for controlling the connection between the motor and cams for regulating the maximum capacity at which the compressor can operate.

32. The combination-with a .variable capacity compresson'of control valves for controlling the loading and unloading of the compressor, electrically operated means for controlling operation of said valves, cams controlling energizing of said electrically operated means, a shaft carrying said cams, a continuously operating motor, an optrically operated means for controlling operation.

of said valves, cams controlling energizing of said electrically operated means, a shaft carrying said earns, a continuously operating motor, an operating yoke connected to said motor and operated thereby, means normally holding said yoke out of operating connection with said shaft, pressure operated means for moving said holding means to permit operative connection of the yoke and shaft, and a star cam carried by said shaft to prevent overrun of the cams upon each operation thereof.

- EDWARD M. PAULLIN, Ja.