US1931771A - Control means for electric motor operated devices - Google Patents

Description

Oct. 24, 1933. c, s. PINKERTON CONTROL MEANS FOR ELECTRIC MOTOR OPERATED DEVICES I 2 Sheets-Sheet 1 Filed Dec. 17, 1931 Oct. 24, 1933. 1,931,771

CONTROL MEANS F OR ELECTRIC MOTOR OPERATED DEVICES C. S. PINKERTON' 2 Sheets-Sheet 2 Filed Dec. 17, 1951 3) MOW/v mam/wow Patented Oct. 24, 1933 UNITED STATES PATENT OFFICE CONTROL lVIEANS FOR ELECTRIC MOTOR OPERATED DEVICES Application December 17, 1931 Serial No. 581,576

13 Claims.

This invention relates to improvements in control means for electric motor operated devices, and the invention more particularly relates to improvements in remote pressure control means for fluid distribution systems.

The remote pressure control means herein disclosed is in general of the character described and claimed in my prior Patent No. 1,743,233, dated January 14, 1930.

An object of the invention is to provide a novel system of relays for control of an electric motor operated device.

Another object is to provide improved and simplified control means for a relay system of the character aforementioned.

Another object is to provide means enabling utilization of a minimum number of low voltage control lines between a flow controlling valve of the distribution system and a point in the system relatively far removed from said valve.

Another object is to provide means of the character aforementioned wherein certain of the control elements employed are operable with relatively low current consumption, whereby relatively small transmission lines may be employed regardless of the distance between a given remote point and said elements of the control system.

Another object is to provide means responsive to pressure conditions at a remote point in the fluid distribution system to directly control the pressure of fluid supplied to the latter.

Another object is to generally-improve the details of construction and operation of the parts of the fluid pressure control system as a whole.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described, it being understood that the invention is susceptible of embodiment in other forms without departing from the scope of-the appended claims.

In the drawings, Figure 1 illustrates schematically and diagrammatically a portion of a fluid distribution system having my improved control means applied thereto, and

Fig. 2 is a similar illustration of my invention as applied to the control of compressors and compressor-unloaders of a fluid distribution system for maintenance of a predetermined substantially constant pressure at a remote point in the latter.

Referring to Fig. 1, the numeral 5 designates a conduit through which a fluid, such as gas, is

Interposed between conduits 5 and 6 isa valve 7 which may be of the well-known oscillatable disk type,--a reversible motor 8 being provided for driving said valve from an extreme open position to an extreme closed position, and vice versa,.or to any intermediate position, through the medium of suitable worm and pinion gearing 9,-the worm shaft 9 being threaded to effect travel of a nut 9 which in its respective extreme positions engages limit switches 9, 9 to effect interruption of the motor circuit connections. As will be understood the conduit 6 may be of considerable length, say five or ten miles long, between the valve 7 and a point 6 at which it is desired to maintain a substantially constant fluid pressure of predetermined value.

Accordingly I provide at the point 6 a suitable pressure responsive device, such as the prover-bell designated in general by the numeral 10, said device as shown being provided with a pivoted contactor 11 which is retained in the intermediate or neutral position illustrated upon attainment and during maintenance of a predetermined pressure of fluid at the point 6 of conduit 6. Upon a predetermined decrease in pressure of the fluid at point 6 contactor 11 is movable upwardly by bell 10 into engagement with a stationary contact 12, and upon a predetermined increase in pressure of said fluid the contactor 11 is moved downwardly by bell 10 into engagement with a stationary contact 13,it being understood that the device 10 is calibrated and/or adjustable to provide for response thereof in either sense in accordance with the requirements of the particular installation. Also it is to be understood that any other suitable form of pres- 1 sure responsive device may be employed if desired.

More particularly, assuming a given adjustment of valve 7 (say, half-open positioning thereof as indicated by the position of nut 9 and further assuming a demand or rate of consumption of the fluid such that the pressure thereof at point 6 remains of a substantially constant predetermined value, there will of course be no movement of contactor 11 to either 01. its extreme positions, and hence there will be no necessity for adjustment of valve 7. On the other hand, if the rate of supply through valve 7 exceeds the rate of consumption of the fluid the pressure of the latter will be increased, with resultant movement of contactor 11 into engagement with contact 13. The arrangement is preferably such that upon engagement of contactor 11 with contact 13,-the contacts 14, 14 of switch 14 having previously been closed by depression of push button 44 ,--a rectified current of relatively low voltage is caused to flow in a'g'iven direction through the operating coil 15 of a polarized relay 15 of well known form. The energizing circuit for coil l5 may be traced from contactor 11 by conductor 16 through said coil, by conductor 17 to and through contacts 14 14 of switch 14 by conductors 18 and 19 through the elements 20 of a rectifier system of well known form, and thence by conductor 21.to contact 131 Said rectifier system preferably includes a second set of elements 22,-and said elements 20, 22 have associated therewith the secondary windings 20 22* of a transformer 23 the primary windings of which are shown at 23 and 23 The primary windings 23, 23 may be supplied from a suitable source of alternating current of relatively high voltage, say 110 volts, as represented by lines 1 1", which voltage may be stepped down through the medium of the secondary windings 20, 22" to a relatively low value, say 10 volts.

Polarized relay 15 is provided with a contactor 15 which is movable from the neutral position thereof as illustrated to selectively engage either 7 of the stationary contacts 15 or 15; and assuming engagement of contactor 15 with contact 15 upon energization of the circuit of coil 15 in the manner just described, an energizing circuit is completed for the winding 2 1 of a relay 24 the normally open contacts 24, 24 of which are adapted when closed to energize the field 8* of motor 8 and to efifect a flow of current in one direction through the armature of said motor.

The energizing circuit for winding 24 may be traced from line L by conductors 24 25 and 26 through the contacts 27 and 28 of a suitable timing device which provides for intermittent closure of said contacts, by conductors 29 and 30 through a normally closed push button switch 31, by conductor 32 through the contacts of limit switch 9, by conductor 33 through said winding 24, thence to and through contact 15 and contactor 15 of the polarized relay. and by conductor 34 to line L.

Upon closure of contacts 24*, 24 of relay 24 a circuit is completed for motor 8 to provide for operation thereof in one direction, said circuit extending from line L by conductors 24 25 and 35 through the field winding 8", by conductors 36 and 37 through said contacts 24', by conductor 38 to and through the armature of said motor, by

conductor 39 through said contacts 24, and by conductors 40 and 41 to line L.

As will be understood the energizing circuit for the winding 24' of relay 24 will only be completed during closure of the contacts 27, 28 of the aforeto be understood that such timing device may and preferably does include adjustable elements of the character disclosed in my Patent No. 1,743,233 whereby the periods of'opening and closing 0! contacts 27, 28 may be preselected at will to predetermine the duration of each intermittent operation of motor 8 and to permit a given adjust- :ment of valve 7 by motor 8 to become effective (with reference to the pressure of fluid at the point 6) prior toa repeated operation of said motor 8.

After the required degree of closing movement of valve 7 has been effected through one or more periods of intermittent operation of motor 8 the pressure of fluid at the point 6 will be reduced to the desired value, with consequent movement of contactor 11 out of engagement with contact 13 to the neutral position illustrated,--thereby interrupting the en'ergzing circuit of the polarized relay coil 15 to insure against further automatic movement of valve 7 toward its fully closed 1 position.

if the rate of consumption oi fluid from conduit 5 has decreased to a very low value, the contactor 11 may be retained in engagement with contact 13 even after valve 7 has been moved to its fully closed position. In this event, how ever, the contacts of limit switch 9 will be opened automatically to interrupt the circuit of motor 8 whereby injury to the valve 7 or the driving elements thereof is prevented.

If the rate of consumption of fluid from conduit 6 exceeds the rate of supply thereof through valve7, the pressure of fluid at the remote point 6 will of course be reduced, and upon a predetermined reduction of pressure the contactor 11 will be caused to engage contact 12, with a' consequent flow of rectified current of relatively low voltage through the ml 15 of polarized relay 15, but in a reverse direction from that aforedescribed. Said circuit may be traced from contact 12 by conductor 45 to and through the rectifier elements 22, conductors 46 and 18 through contacts 14, 14 of switch 14, conductor 17 through said coil 15, and by conductor 16 to contactor 11. The consequent reversal of current through coil 15 will cause engagement of polarized relay contactor 15 with the contact 15 An energizing circuit will thus be completed for the winding 46 of relay 46,said circuit extending from line L by conductors 24 25 and 26 through contacts 27, 28 (when closed) of the timing device, by conductors 29 and 30 through the contacts of push button switch 31, conductors 32 and 47 through the contacts of limit switch 9, conductor 58 through said winding 46 to and through said contact 15 and contactor 15 and by conductor 34 to line L Contacts 46 and 46 of relay 46 are adapted when closed to complete an energizing circuit for motor 8 to provide for operation of the latter in the reverse direction from that aforedescribed. Said circuit may be traced from line L by conductors 24, 25 and 35 through the field winding 8, conductors 36 and 49 through contacts 46, by conductor 50 through the armature of motor 8, by conductor 38 through contacts 46", and by conductors 51 and 41 to line L' During each period of closure of the contacts 46*, 46 of relay 46 (as controlled by the adjustment of the timing device represented diagrammatically by the cam member 42), the motor 8 is operated in a direction to effect opening movement of valve 7,--which opening movement will be continued intermittently in the manner aforedescribed until the fluid pressure at point 6 has been increased to the desired value, with consequent disengagement of contactor 11 from contact 12 to de-energize the polarized relay coil 15, or until valve 7 has been fully opened with re sultant opening of the contacts of limit switch 9 to interrupt the last-mentioned circuit of motor 8.

vThe reference characters R and G designate electric signal lamps which are respectively connected in circuit in parallel with the relay windings 24 and 46 ,-said lamps being normally jointly illuminated upon closure of the contacts 28, 27 of the timing device and extinguished upon opening of said contacts (assuming operation of push button switch 14 to effect disengagement of its contacts 14, 14

The lamp G is further subject to control by the contacts of limit switch 9, so that upon full open positioning of valve '7 (as characterized by opening of the contacts of said limit switch 9) the-circuit of lamp G will be completely interrupted pending movement of valve 7 from its full open position. During such full open positioning of valve '7 the lamp R will be energized during intermittent closure of the contacts 28,

27 of the timing device, whereby a visual signal or indication of the position of valve '7 is provided for the attendant. In like manner the lamp R is further subject to control by the contacts of limit switch 9 so that upon full closed positioning of valve '7 the circuit of said lamp will be interrupted by said limit switch contacts, and subsequent intermittent illumination of lamp G alone may be utilized to provide a visual signal or indication to the attendant that the valve 7 is in full closed position. In practice the lamp R is preferably colored red and the lamp G is pref- I erably colored green.

' Also I preferably provide additional means affording an audible signal or indication to the attendant that the valve '7 is in its full open position. Said means as shown may comprise an electrically operated bell 52 the operating coil of which is adapted to be connected across lines L L upon closure of the contacts 53 53 of a relay 53. As shown relay 53 is provided with a coil 53 which when energized tends to effect engagement of contact 53 with contact 53* Said relay is further provided with a coil 53 which acts when energized to withhold contact 53 from engagement of contact 53 against the biasing effect of coil 53. Coils 53, 53 are jointly energized and de-energized upon closing and opening, respectively, of the contacts 27, 28 of the timing device. Coil 53 however, is additionally subjected to control by the contacts of limit switch 9, so that upon full open positioning of valve '7 (with consequent opening of the contacts of limit switch 9) the energizing circuit of coil 53 will be interrupted to permit closure of contacts 53 53 of relay 53 under the bias of coil 53 during each intermittent closure of contacts 27, 28 of said timing device. The advantages of this arrangement will be apparent to those skilled in the art.

It is to be understood that lines 1 1 may be connected to lines L L respectively, or to any other suitable source of alternating current supply.

Inasmuch as the conductors 16 and 18 are only required to carry rectified or direct current of relatively low voltage the dotted line portions 16 and 18 thereof may be connected to a pair of telephone wires or lines extending between the remote point 6 and the operating elements of valve 7. By the means aforedescribed I have reduced, by one, the number of control lines required between the remote point and the flow controlling valve, as compared with the disclosure of my Patent No. 1,743,233. This feature is of considerable importance since the rental charge for use of the telephone lines is thereby reduced by onethird. If telephone lines are not available for use in the manner herein contemplated a relative saving of even greater amount but of like proportion is effected in that only two control wires (instead of three) are required to be installed between said remote point and the valve '7.

In the foregoing description contacts 14 14 and 44 44 of switches 14 and 44, respectively, were assumed to have been bridged or closed, such closure having been effected by merely depressing the push button 44. If it is desired to discontinue automatic control of valve '7, this may be effected by merely depressing push button 44 to open the contacts 14 14 44 44 Contacts 14, 14 are thus closed. as shown in the drawings, and control of the operation of valve 7 is transferred from the contacts of polarized relay 15 to a pair of normally open push button switches 54 and 55. Closure of push button switch 54 corresponds in function with closure of contacts 15*, 15 of said polarized relay, whereby valve 7 may be moved to the desired degree toward fully closed position; and push button 55 may be temporarily depressed manually to effect the desired degree of movement of valve '7 toward fully opened position. The visual and audible signal elements R, G and 52 function as aforedescribecl under conditions of manual control of operation of valve 7. The relays 24 and 46 are preferably provided with mechanical interlocking means of well known form (not shown) to insure against I simultaneous closure of the contacts thereof in the I event of simultaneous closure of the push button switches 54, 55.

The fluid distribution system illustrated in Fig. 2 is in general quite similar to that shown in Fig. 1, and corresponding parts have been designated by like characters of reference in the two figures. Thus I have shown means identical with the elements aforedescribed to control ener gization of the coil 15 of polarized relay 15,- the contactor 15 and contact 15 of said relay being adapted to control energization of the winding 24 of relay 24, and the contactor 15 and contact 15 of said polarized relay being adapted to control energization of the winding 46 of relay 46. The contacts 24 and 46 of relays 24 and 46 in this instance are respectively adapted to provide maintaining circuits for the windings 24 46 of the latter under certain conditions, as hereinafter described. The contacts 24 and 46 of said relays are adapted when closed selectively to provide energizing circuits for the split field windings 56 or 56 of a motor 56 to effect operation of the latter in reverse directions selectively.

The driving motor 43 for the timing device 42 is subject to control by push button switch 44, as in the previous illustration. In this case, however, I have shown the contacts 2'7, 28 of the timing device directly interposed between the supply line L and contactor 15 of the polarized relay. Motor 56 as shown is adapted to drive a worm 57 which meshes with a pinion 58 fixed to a shaft 58*. Fixed to one end of shaft 58 is a contactor 59 which is movable by said shaft throughout a predetermined range to sequentially engage and disengage a plurality of fixed contacts 60, 61, 62, and 63,said contactor having a number of off positions marked 0, 1, 2, 3 and 4 wherein the elements function in the manner hereinafter described.

Also secured to shaft 58- in angularly offset relation to each other are a pair of contactors 65 and 66 which are adapted under given con ditions to sequentially and'transiently engage the contacts 65, 66 respectively. Carried by con tactor 65 is a contactor 65 which is adapted to engage a contact 65 simultaneously with engage ment of contact 65* by said eontactor 65,- a well known form of lost motion connection being provided between contactors 65 and .65 .whereby the latter is permitted to disengage its cooperating contact 65 while the former remains in engagement with its cooperating contact 656. Also carried by contaetor 66 is a eontactor 66 which is adapted to engage. a contact 66 slmultaneously with engagement of contact 66 by said contaetor 66,--a similar lost motion con nection being provided between contactors 66 and 66 whereby the latter is permitted to disengage its cooperating contact 66 while the former remains in engagement with contact 66, and also while contactor 65 remains in engage ment with contact 66 as aforedcscribed.

Assuming closure of a push button switch 6?, the arrangement is preferably such that upon closure of contacts 65 65 an energizing circuit is completed for the closing coil 68 of an electromagnetically operable switch 66, the con-- tacts 68 of the latter when closed completing circuit for the motor 69 which is adapted. as shown to drive a compressor or pump '70 oi well known form. Compressor 76 is provided at one end thereof with a valve 'lll which is adapted to be opened upon energization of the operating coil 70* to partially unload the compressor where by the same delivers fluid at a rate of substan tially one-half of its capacity. As a'fcreindicatcd the coil '70 is energized simultaneously with completion of the circuit of motor 69, so that the compressor 70 initially" delivers one-hall oi? its rated capacity If this rate of supply of iiuid to conduit 6 is insufficient to restore the desired degree of pressure at the remote point 6 the motor 56 will continue to operate to eventually effect disengagement of contactor 65 from cooperating contact 65, thereby deenergizing the coil 70 to permit valve 70 to functir a. in the normal manner, whereupon compressor 76 operates at full capacity.

Thereafter if the pressure of fluid at the remote point 6 remains below the required value motor 56 will continue to operate to effect en gagement of contactors 66 and 66 with their cooperating contacts 66 and 66 ,--the contacts 66 66 completing an energizing circuit for the closing coil '71 of an electromagnetically operable switch 71. The contacts 71 of switch 71 when closed complete circuit for the motor '72 which drives a compressor 73 like the compares sor 70 aforedescribed. Compressor '73 is provided at one end thereof with a valve '73 which is adapted to be opened upon energization of the operating coil 73 to partially unload the compressor, said unloading efiect being provided prior to or at the instant when the compressor is started. Under these conditions compressor 70 will be operating at full capacity and compressor '13 at half-capacity. If the pressure at the remote point 6 thereafter remains below the value desired or required motor 56 will continue to operate, with resultant disengagement of contacts 66, 66 to interrupt the circuit of coil 73*, whereupon compressor 73 will likewise operate at full capacity.

It is to be understood that the timing device represented diagrammatically by the cam 42 and contacts 28, 27 may be of'the adjustable character defined in my patent aforementioned, whereby the intermittent operations of motor are timed to permit eachjchange in the rate of delivery from compressors 70 and/or '73 to take effect at the remote pointfi prior to a repeated operation ofsaid motor 56;

In order to more fully describe the operation of this system, let it be assumed that both of the compressoi's'w and {13 have been shut down (which condition would be represented by positioning of contactor '59 at the point o l, with consequent disengagement oi. all of the contac tors 65, 65 and '66, 66 from their associated contacts. Then if the pressure of fluid at the remote point 6 drops a predetermined degree be low the required value contactor ll will engage contact 12 with consequent energiaation of coil 15 of the polarized relay 15in a sense to 1 o engagement of contactor 16* with contact l5 ,-and assuming closure of contacts 2'2, 26 of the timing device at that instant, or within a predetermined period thereafter, circuit will be completed for the coil 46 of relay i6,-said circuit being obvious. Contacts &6 when closed complete circuit for motor 56 through the field winding 56 of the latter. Motor 66 will th upon operate in a direction to cause movem contactor 59 from the position 0 'thereor rto engagement with segment 66, and due to closure of contacts 46 oi relay 46 a maintaining circuit is provided for cell. 46* independently of he core tacts 2t", 28 of timing device. Said r ing circuit may be traced from line U, by conductor T l through cell d6 to and through eon tacts i6 by conductor '16 to segment 66 and contactor 56, by conductor l6 through push button switch 6'2 to line L Uperation of motor 56 in the required direction is thus insured pending movement of contaetor 56 out of engagement with segment 66 and into the oil" position thereof designated by the numeral 1. In the meantime. however, contactor 66 will have engaged contact 65 to provide an energizing circuit for the coil 1'0 of the unloader valve of compressor 'lll,--said circuit extending from line L by conductor 77 through coil ro by conductor '76 through con tact 65 and contactor 65, and by conductors 79 and 76 through switch 6'? to line L Contactor 65 will also be in engagement with contact 65 to complete a circuit for the coil 68 oi switch 68, said circuit extending from line L by conductor 86 through coil by conductor 61 through contact 65, contaetor 65 and by conductors 79, 76 130 through switch 6? to line L Upon closure of contacts 66 01" switch 66 a circuit is completed for motor 69, and operation of thevpartially loaded compressor .70 is initiated. After a predetermined period of time (dependent upon the distance between remote point 6 and compressor '70) the pressure eiTect upon the fluid in conduit 6 of operation of the partially loaded compressor will be transmitted to the point 6, and if the required pressure of fluid has been established eontactor 11 will be moved automatically to its intermediate or neutral position to de-energize the coil 15 of the polarized relay.

However, if the pressure of fluid at point 6 remains below the required value contactor 11 will remain in engagement with contact 12, and upon the next period of closure of contacts 27, 28 of the timing device, the aforedescribed energizing circuit for coil 4L6 of relay 46 will be again completed, and upon movement of contactor 59 into 1,931,771 engagement with segment 61 (through operation of motor 56 in the direction aforementioned) the aforedescribed circuit of coil 46 will be again maintained pending movement of contactor 59 to the oif position marked 2. At the same time contactor 65 will be moved out of engagement with contact 65 to interrupt the aforedescribed circuit for coil '70 of the unloading valve. and thereafter compressor 70 will be operated at full capacity. The pressure effect of thisincrease in the rate of, supply of fluid to conduit 6 by compressor '70 will be transmitted to point 6 prior to the next period of closure of contacts 27, 28 of the timing device. If contactor 11 of the prover bell then remains in engagement with contact 12, motor 56 is again operated in the same direction to effect engagement of contactor 59 with segment 62, whereby the energizing circuit of coil 46 is maintained pending movement of contactor 59 to the off position marked 3. At this time contactors 66 and 66 will have been engaged with their cooperating contacts 66 and 66, to energize the coil '73 of the unloading valve '73 of the second compressor '73 and to energize the circuit of coil '71 of switch '71, whereby the contacts '71 of the latter are closed to complete circuit for motor '7-2,with consequent initiation of operation of compressor 73 in a partially loaded condition.

If after the aforementioned predetermined time interval the contactor 11 remains in engagement with contact 12. closure of contacts 27, 28 will again provide for energization of coil 46 of relay 46,-and contactor 59 will cooperate with segment 63 to maintain said coil energized pending movement of contactor 59 to the off position marked 4. During such movement of contactor 59 contactor 66 will have been disengaged from contact 66, with consequent de-energization of coil 73*; ands thereafter the compressor '73 (as well as compressor '70) will be operated at full load. A suitable form of limit switch (not shown) may be provided to insure against any further operation of motor 56 in the direction aforementioned,' after the contactor 59 has reached said off position marked 4.

. Assuming an increase in pressure beyond the value required at point 6 (due, for instance, to

a decrease in rate of consumption of the fluid), contactor 11 of the prover bell will be caused to engage contact 13,--the coil 15 of polarized'relay 15 then being energized in a reverse sense reverse direction.

to cause engagement of contactor 15 with contact 15. Assuming closure of contacts 27, 28 of the timing device a circuit will be completed for the coil 24 of relay 24.--said circuit extending from line L by conductors '74 and 82 through coil 24, thence through contact 15 and contactor 15 through contacts 28, 27 to line L. Closure of contacts 24 of relay 24 will complete a circuit for motor 56 through the field winding 56 of the latter, with consequent operation thereof in the Thus contactor 59 will be moved from off position 4 into engagement with segment 63 whereby the energizing circuit of coil 24 is maintained pending movement of contactor 59 to its off position marked 3. In the meantime contactor 66 will have been re-engaged with contact 66 to again energize coil '73, whereby compressor '73 will be partially unloaded. The step by step operations are repeated in a reverse order from that aforedescribed to thereafter disengage contactor 66' from contact 66 to entirely shut down the compressor 73, to thereafter partially unload compressor '70, and to thereafter entirely shut down the latter as well; such automatic operations depending of course upon the pressure of fluid at point 6.

By the provision of timing means of the character aforementioned the pressure change resulting from a given adjustment of the fluid flow controlling means is allowed to have full effect at the remote point prior to the next succeeding adjustment. In this manner hunting of the fluid pressure control elements is substantially eliminated.

The control scheme of Fig.2 is particularly advantageous in that it eliminates the necessity for higher pressure of the fluid than is required at any point in the distribution system to maintain the desired pressure at a remote point in the latter. For this reason leakage of the fluid (as an incident to excessive pressure thereof) is likewise eliminated. 0n the other hand, the pressure of fluid at the remote point is maintained substantially constant irrespective of variations in the demand or rate of consumption at other points in the system or in the system as a whole.

While I have shown the compressors "70 and '73 as entirely controlling the rate of supply of fluid to conduit 6, it will be apparent to those skilled in the art that I may lead from a source of supply of fluid under given pressure a conduit which is connected to conduit 6 in a relation to normally by-pass said compressors,the normal pressure of fluid and the rate of flow thereof through said auxiliary conduit being preferably such that the required pressure of fluid will be maintained at a given remote point in the system under conditions of consumption of fluid at an average or normal rate. With such an arrangement one or both of the compressors would only be required to maintain the required pressure under "-peak load conditions in the distribution system. Also. of course, the aforementioned auxiliary conduit would preferably be provided with a suitable form of check valve to avoid loss of the additional pressures incident to operation of one or more of the compressors.

It will be understood that visible and audible signaling elements of the character illustrated in Fig. 1 may likewise be associated with the control elements of Fig. 2; and in like manner suitable alternative manual control elements may be added to the system of Fig. 2.

What I claim as new and desire to secure by Letters Patent is: I

1. In a fluid distribution system, in combination, a source of fluid supply, a distribution conduit, and means for varying the rate of supply of fluid to said conduit to maintain a substantially constant pressure at a remote point in-the latter under conditions of variation in the rate of consumption of the fluid, said means comprising adjustable flow regulating means located adjaceht to the source of supply and switching mecl': anism located at said remotepoint in the conduit and responsive to high and/or low pressure conditions in the latter, power operated means for effecting adjustment of said flow regulating means, and means for rendering said power operated means responsive to said switching mechanism, said last mentioned means including a polarized relay, and a single pair of conductors extending between said switching mechanism and the coil of said polarized relay.

2. In a fluid distribution system, in combination, a source of fluid supply, a distribution con duit, and means for varying the rate of supply of fluid to said conduit to maintain a substantially constant pressure at a remote point in the latter under conditions of variation in the rate of consumption of the fluid, said means comprising adjustable flow regulating means located adjacent to the source of supply and switching mechanism located at said remote point in the conduit and responsive to high and/or low pressure conditions in the latter, power operated means for effecting adjustment of said flow regulating means, and means for rendering said power operated means responsive to said switching mechanism, said last mentioned means including a polarized relay, a single pair of conductors extending between said switching mechanism and the coil of said polarized relay, and means operable independently of said polarized relay to render said power operated means ineil'ective for a given period preselected in accordance with the distance between said flow regulating means and said remote point in the conduit, whereby a given change in the rate of flow of fluid to said conduit is rendered effective at said remote point prior to a repeated operation of said power operated means.

3. In a fluid distribution system, in combination, a source of fluid supply, a distribution conduit, and means for varying the rate of supply of fluid to said conduit to maintain a substantially constant pressure at a remote point in the latter under conditions of variation in the rate of consumption of the fluid, said means comprising adjustable flow regulating means located adjacent to the source of supply and switching mechanism located at said remote point in the conduit and responsive to high and/or low pressure conditions in the latter, power operated means for effecting adjustment of said flow regulating means, and means for rendering said power operated means responsive to said switching mechanism, said last mentioned means including a polarized relay, a single pair of conductors extending between said switching mechanism and the coil of said polarized relay, means operable independently of said polarized relay to render said power operated means ineffective for a given period preselected in accordance with the distance between said flow regulating means and said remote point in the conduit, whereby a given change in the rate of flow of fluid to said conduit is rendered effective at said remote point prior to a repeated operation of said power operated means, and means for controlling operation of said power operated means independently of said switching mechanism and said polarized relay, said means comprising a transfer switch and a pair of manually operable push button switches, said push button switches being operable selectively to directly control the circuits normally controlled by said polarized relay.

4. In a fluid distribution system, in combination, a source of fluid supply, a conduit, adjustable means located at a given point for controlling the flow of fluid to said conduit, power means for effecting adjustment of said adjustable means to increase or decrease the rate of flow of said fluid, and means operable automatically to control the operation of said power means, said control means including a polarized relay coil located adjacent to said adjustable means, a pressure responsive device associated with said conduit at a remote point in the latter, said pressure responsive device including a movable contactor and a pair of stationary contacts to be mlectively engaged thereby, means for insuring a flow of current through said contactor in one direction upon engagement thereof with one of said contacts and to insure a reverse flow of current through said contactor upon engagement thereof with the other of said contacts, said last mentioned means including a current rectifying device for each of said contacts, and means comprising a single pair of conductors extending between said remote point and the terminals of said polarized relay coil, one of said conductors being electrically connected to said contactor and the other of said conductors being electrically connected to each of said current rectifying devices. 5. In a fluid distribution system, in combination, a source of fluid supply, a distribution con duit, and means for varying the rate of supply of fluid to said conduit to maintain a substantial- 1y constant pressure at a remote point in the latter under conditions of variation in the rate of consumption of the fluid, said means comprising a power operated compressor located adjacent to the source of fluid supply, switching mechanism located at said remote point in the conduit and responsive to high and/or low pressure con ditions in the latter, means controlled by said switching mechanism under predetermined low pressure conditions to initiate operation of said compressor in partially loaded condition, and means operable automatically after a predetermined time interval, in the event of continued low pressure conditions, to effect full load operation of said compressor.

6. In a fluid distribution system, in combination, a source of fluid supply, a distribution conduit, and means for varying the rate of supply of fluid to said conduit to maintain a substantially constant pressure at a remote point in the latter under conditions of variation in the rate of consumption of the fluid, said means comprising a plurality of power operated compressors located adjacent to the source of fluid supply and having the outlet ends thereof respectively connected with said conduit, switching mechanism located at said remote point in the conduit and responsive to high and/or low pressure conditions in the latter, means controlled by said switching mechanism under predetermined low pressure conditions to effect partial unloading of one of said compressors and to initiate operation of said compressor in partially loaded condition, and associated means also controlled by said switching mechanism and operable after a predetermined time interval to effect full load operation of said compressor, said means also acting thereafter to partially unload another of said compressors and to initiate operation of the latter in partially loaded condition, and said means also acting thereafter to effect full load operation of said second mentioned compressor.

7. In a fluid distribution system, in combina tion, a source of fluid supply, a distribution conduit, and means for varying the rate of supply of fluid to said conduit to maintain a substantially constant pressure at a remotepoint in the latter under conditions of variationin the rate of consumption of the fluid, said means comprising a plurality of power operated compressors located adjacent to the source of fluid supply and having the outlet ends thereof respectively connected with said conduit, switching mechanism located at said remote point in the conduit and responsive to high and/or low pressure condil ke tions in the latter, means controlled by said I switching mechanism under predetermined low pressure conditions to effect partial "unloading of one of said compressors and to initiate operation of said compressor in partially loaded condition, and associated means also controlled by said switching mechanism and operable after a predetermined time interval to effect full load operation of said compressor, said means also acting thereafter to partially unload another of said compressors and to initiate operation of the latter in partially loaded condition. and said means also acting thereafter to effect full load operation of said second mentioned compressor, said means being likewise controlled' by said switching mechanism under high pressure conditions to reverse the cycle of operations of said compressors and their respective unloaders, whereby the rate of supply of fluid to said conduit is intermittently decreased by predetermined amounts as required pending shut-down of all of said compressors.

8. In a fluid distribution system, in combination, a source of fluid supply, a distribution conduit, a plurality of power operated compressors interposed between said source of fluid supply and said conduit, means for initiating operation of said compressors in sequence, associated means for insuring partial unloading of each of said compressors upon initiation of operation thereof and for thereafter efiecting full load operation of the latter, whereby the rate of flow of fluid to said conduit may be increased in steps in accordance with variations in demand for the fluid, said means comprising a driving motor for each of said compressors, means including a reversible pilot motor and switch mechanism operable thereby to control energization of said driving motors and to control unloading and loading of the respective compressors, a polarized relay operable to selectively control the direction of operation of said pilot motor, and a pressure responsive switching mechanism located in said conduit at a point remote from said compressors, said last mentioned switching mechanism being operable to control energization of said polarized relay in accordance with variations in pressure of fluid at said remote point with respect to a predetermined value.

9. In a fluid distribution system, in combination, a source of fluid supply, a distribution conduit, a plurality of power operated compressors interposed between said source of fluid supply and said conduit. means for initiating operation of said compressors in sequence, associated means for insuring partial unloading of each' of said compressors upon initiation of operation thereof and for thereafter effecting full load operation of the latter, whereby the rate of flow of fluid to said conduit may be increased in steps in accordance with variations in demand for the fluid, said means comprising a driving motor for each of said compressors, means including a reversible pilot motor and switch mechanism operable thereby to control energization of said driving motors and to control unloading and loading of the respective compressors, a polarized relay operable to selectively control the direction of operation of said pilot motor, a pressure responsive switching mechanism located in said conduit at a point remote from said compressors, said last mentioned switching mechanism being operable to control energization of said polarized relay in accordance with variations in pressure of fluid at said'remote point with respect to a predetermined value, and means operable automatically and independently of said polarized relay to render said pilot motor intermittently ineffective for predetermined periods of time, whereby the pressure effect of a given change in the rate of supply of fluid by said compressors is transmitted to said remote pointprior to a further change in said rate of supply.

10. A gas pressure-regulating system comprising in combination a'source of gas, a main for carrying the gas to a point remote from the source, a valve in said main at said source, a pressureresponsive diaphragm in communication with the main at said remote point, a two-wire circuit extending from said source to said remote point, a source of direct current, a switch operatively connected to said diaphragm and arranged to connect said source of direct current to said two-wire circuit when the gas pressure exceeds or drops below that to be maintained, so that the current sent over. said circuit is of one polarity when the gas pressure at the remote point is too low, and of the opposite polarity when the gas pressure is too high, a polarized relay connected in said twowire circuit at said source of gas, a control circuit located at said source of gas and having three legs, either of the first two legs being arranged to be closed by the polarized relay, the third leg connected to the first two and serving as a common return lead, a source of electric current connected to a switch arm of said polarized relay and to the third leg of said control circuit, two solenoids, each connected in series with one of said first two legs, a switch in circuit with said solenoids, automatic means for alternately opening and closing said switch at regular time intervals, an electric motor operatively connected with said valve in the gas main, a power line for said motor, a motor-reversing switch connected between the motor and said power line, said reversing switch arranged to be closed by one of said solenoids in the control circuit -to operate the motor to close said valve, and to be closed by the other of said solenoids to operate the motor to open said valve.

11. A gas pressure-regulating system comprising in combination a source of gas, a main for carrying the gas to a point remote from the source, a valve in said main at said source, a reversible electric motor arranged to operate said valve, a pressure-responsive diaphragm in communication with said main at said remote point, a two-wire circuit extending from said source to said remote point, a source of direct current, a switch operatively connected to saiddiaphragm and arranged to connect said source of direct current to said pair of wires when the gas pressure exceeds or drops below that to be maintained so that the current sent over the pair of wires is of one polarity when the gas pressure is too low, and of the opposite polarity when the pressure is too high, a polarized relay connected to the two-wire circuit at the source of supply, means controlled by said relay for causing said reversible motor to close or open said valve according to the polarity of the direct current flowing through said relay, means independent of said relay control means constantly operating to interrupt the power to said reversible motor at predetermined time intervals.

12. A gas pressure-regulating system comprising in combination a source of gas, a main for carrying the gas to a point remote from the source, a valve in said main at said source, a motor arranged to operate said valve in either direction, a pressure-responsive diaphragm in commu-' nication with said main at said remote point, a two-wire circuit extending from said source to said remote point, a source of direct current, a switch operatively connected to said diaphragm and arranged to connect said source to said pair of wires when the gas pressure exceeds or drops below that to be maintained, so that the current sent over the pair of wires is of one polarity when p ing valve at said source, a reversible valve-actuating electric motor in a power circuit, a pressuremeasuring station remote from said gas source, two electric conductors connecting said gas source and station, two sources of direct electric current at said station arranged to establish a relay-actuating circuit in either direction in said conductors, a polarized relay operatively connected to control the power circuit of said motor, said relay adapted to be actuated by the current in said relay circuit to cause said reversible motor to run in either direction according to the polarity of the current, a gas-actuated diaphragm in communication with the gas conduit system at said remote station, a switch operable by said diaphragm in one direction under increasing gas pressure and in the opposite direction under de creasing pressure, said switch arranged to transmit the current from either of said two sources of current to said conductors, and.a constantlyoperating interrupter for the power circuit of said valve-actuating motor.

CLARENCE S. PINKERTON.

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