US3662948A

US3662948A - Control system and method for operating heat exchanger means and the like

Info

Publication number: US3662948A
Authority: US
Inventors: Louis M Puster
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1970-01-21
Filing date: 1970-01-21
Publication date: 1972-05-16
Anticipated expiration: 1989-05-16

Abstract

A pneumatically operated actuator having a first condition for maintaining an on-off heat exchanger means in an off condition thereof as long as a pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining the heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and means for automatically creating and directing to the actuator a pneumatic signal that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of the actuator will be both variable in relation to each other from approximately 0 to 100 percent of the time in each time period depending upon the magnitude range of the pneumatic signal in each time period.

Description

United States Patent Puster 1 May 16, 1972 [72] Inventor: Louis M. Puster, Knoxville, Tenn.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Jan. 21, 1970 [21] Appl.No.: 4,616

[56] References Cited UNITED STATES PATENTS 2,914,077 11/1959 Grogan ..137/85 X 3 ,O20,49O 2/ 1962 Kleiss 3,126,904 3/1964 Ciarlariello ..236/82 UX 3,443,121 5/ i969 Weisbrod ..236/46 F Primary Examiner-Meyer Perlin Assistant Examinerl. D. Ferguson Attorney-Auzville Jackson, Jr., Robert L. Marben and Candor, Candor & Tassone [57] ABSTRACT A pneumatically operated actuator having a first condition for maintaining an on-off heat exchanger means in an off condition thereof as long as a pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining the heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and means for automatically creating and directing to the actuator a pneumatic signal that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of the actuator will be both variable in relation to each other from approximately 0 to 100 percent of the time in each time period depending upon the magnitude range of the pneumatic signal in each time period.

27 Claims, 8 Drawing Figures Patented May 16, 1972 3,662,948

4 Sheets-Sheet 1 30 hi? 6 fif TIME (MINUTES) INVENTOR. LOUIS M. PUSTER HIS ATTORNEYS Patented May 16, 1972 3,662,948

4 Sheets-Sheet 2 IA 82 -7OA INVENTOR. LOUIS M.PUSTER BY FIG'4 I M, M f 7 440..

HIS ATTORNEYS Patented May 16, 1972 3,662,948

4 Sheets-Sheet IOO Y FIG.6 4%, win

HIS ATTORNEYS CONTROL SYSTEM AND METHOD FOR OPERATING HEAT EXCHANGER MEANS AND THE LIKE This invention relates to a control system and method for operating a heat exchanger means or the like.

It is well known that many comfort control systems utilize electric resistance heaters to provide the heat and/or direct expansion refrigeration to provide the cooling whereby in either case, the only practical control mode is an on-off cycling of the heaters and/or the refrigeration compressor with a pneumatically operated electrical switch. However, it has been found that it is difi'icult to obtain satisfactory control of the temperatures in this way since heating and/or cooling capacity sufficient to handle the maximum loads must be provided whereby overheating or undercooling is typical under light load variations. Further, response time and thermostat location become extremely critical factors in such prior known control systems.

However, it is a feature of this invention to provide a control system comparable to that obtained on a proportional action system by on-ofi cycling the heat and/or cooling device on a proportional time basis.

In this manner, the control system of this invention provides a much better temperature control than a conventional on-off system and the advantages of the system of this invention are especially pronounced at light load conditions where normal on-off control allows overheating in heating systems and undercooling in cooling systems. Thus, a thermostat with slow thermal response is intolerable with the conventional on-off control, even on steady load conditions, but will give excellent control results in the time proportional system of this invention.

Accordingly, another feature of this invention is to provide a system which makes possible the use of cheaper resistance heating and direct expansion cooling systems where the difficulty of good control has required in the past the installation of more sophisticated systems.

In particular, one embodiment of this invention provides a control system for operating an on-off heat exchanger means, the system comprising a pneumatically operated actuator having a first condition for maintaining the heat exchanger means in an off condition thereof as long as the pneumatic control signal thereto is in a first magnitude range and having a second condition for maintaining the heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range. Means are provided for automatically creating and directing a pneumatic signal to the actuator that varies in magnitude over each predetermined time period in a repeating cycle of the time periods so that the first condition and second condition of the actuator will be both variable in relation to each other from approximately to 100 percent of the time in each time period depending upon the magnitude range of the pneumatic signal in each time period. This lastnamed means comprises a pneumatically operated summation relay means that receives part of its signal means from a temperature responsive device that senses the output temperature effect of the heat exchanger means and receives the remaining part of the pneumatic signal means from a pneumatically operated timing means that directs its signal means to the relay means with a substantially linear magnitude during each predetermined time period.

Other objects, uses and advantages of this invention are apparent from a readingof this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is a schematic view illustrating the improved control system and method of this invention.

FIG. 2 is a chart illustrating the pressure action produced on the pneumatically operated electrical switch of the control system of FIG. 1.

FIG. 3 is an enlarged, axial cross-sectional view of the diverting relay of the control system of FIG. 1.

FIG. 4 is a cross-sectional view of the volume booster of the control system of FIG. 1.

FIG. 5 is a cross-sectional view of the volume booster relay with bias of the control system of FIG. 1.

FIG. 6 is a cross-sectional view of the summation relay of the control system of FIG. 1.

FIG. 7 is a cross-sectional view of the pneumatically operated thermostat means for the control system of FIG. 1.

FIG. 8 is a cross-sectional view of the pneumatically operated electrical switch of the control system of FIG. 1.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide control means for a heat exchanger means and the like, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide control means for other devices as desired.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, the system and method of this invention is generally indicated by the reference numeral 10 and comprises an on-off" heat exchanger means 11, such as a conventional refrigeration compressor arrangement adapted to be turned on when the same has its leads l2 and I3 interconnected to power source leads L and L, by a pneumatically operated electrical switch construction 14 later to be described, the pneumatically operated electrical switch construction 14 being so constructed and arranged that the same is adapted to maintain the heat exchanger means 11 in its ofi condition when the pneumatic signal being directed thereto by a conduit means 15 is at and below a certain magnitude and is adapted to turn on the heat exchanger means 11 when the pneumatic signal through the conduit means 15 to the switch 14 is at and above a predetermined magnitude.

A pneumatic pressure source 16 is provided for the system 10 and is adapted to supply main pressure through a conduit means 17 at a substantially constant pressure, such as 25 psi or the like, with the conduit means 17 being directed to a nor mally open port 18 of a diverting relay l9 later to be described in detail.

The diverting relay 19 may be adjustable or nonadjustable and is preferably provided with a wide difi'erential so as to trip at approximately 20 psi and be reset at 10 psi as will be apparent hereinafter.

A control signal is adapted to be directed to the control signal port 20 of the diverting relay 19 from a conduit means 21 and when the magnitude of such control signal is below the previously described high trip point magnitude of the diverting relay 19, the diverting relay 19 transmits a branch pneumatic signal through a branch port 22 and conduit means 23 to the main or supply port 24 of a volume booster relay 25 that is provided with bias and will be described in detail hereinafter.

The branch pneumatic signal from the relay 25 is adapted to be directed out of a branch port 26 through a conduit means 27 having an orifice 28 therein and being interconnected downstream from the orifice 28 to a conduit means 29 that leads to a timing or capacity tank 30.

A check valve arrangement 31 is provided in a conduit means 32 that bridges the orifice 28 in the conduit means 27 to permit rapid exhausting of the timing tank 30 when the main port 24 of the relay 25 is interconnected to the at mosphere in a manner hereinafter described.

The pressure in the conduit means 27 downstream of the orifice 28 is interconnected by a conduit 33 to the signal port 34 of the relay 25 whereby the bias on the relay 25 is adjusted to maintain the branch pressure at the port 26 upstream of the orifice 28 at a predetermined level above the signal pressure in the conduit 33 downstream of the orifice 28 so that a constant pressure drop is maintained across the orifice 28 to insure essentially constant flow and a constant rate of rise of the pressure in the timing tank 30 as will be apparent hereinafter.

The pressure fluid from the timing tank 30 is interconnected by the conduit 29 to a signal port 35 of a volume boosting relay 36 that has its supply port 37 interconnected by a conduit 38 to the main conduit 17 as illustrated in FIG. 1. The branch port 39 of the relay 36 is interconnected by a conduit 40 to the conduit 21 that leads to the signal port of the diverting relay 19.

However, the conduit 21 is also interconnected to the plus port 41 of a summation relay 42 having its supply port 43 interconnected by a conduit 44 to the main conduit 17.

Thus, it can be seen that when the pressure in the tank 30 builds up to produce through the volume booster 36 a signal pressure to the signal port 20 of the diverter relay 19 that equals the high trip point of this relay 19, the diverting relay switches and dumps the tank 30 through the check valve arrangement 31, the booster relay 25 and to the atmosphere through a normally closed port 45 of the diverting relay 19 that leads to the atmosphere through a conduit means 46. When the tank pressure 30 is exhausted down to the reset pressure setting of the diverter relay 19, the diverter relay l9 resets and starts recharg' g the tank 30 until the same again reaches the trip point of the relay 19.

In this manner, a saw tooth pneumatic signal" is repetitively being directed by the conduit 21 to the plus port 41 of the summation relay 42 to be utilized in a manner hereinafter described, such saw tooth pressure being represented by the line 47 in the chart of FIG. 2 for a purpose hereinafier described.

A pneumatically operated condition responsive means 48 is provided for the system and is adapted to sense the output temperature effect of the heat exchanger means 11, the pneumatically operated thermostat 48 receiving supply pressure at a port 49 thereof that is interconnected to the main conduit 17 by a conduit 50. The branch pressure from the thermostat 48 is directed out of a branch port 51 through a conduit means 52 that leads to the minus port 53 of the summation relay 42.

The resulting output from the summation relay 42 is directed out of the branch port 54 thereof to the conduit that leads to the pneumatically operated electrical switch 14.

Thus, it can be seen that the resulting output of pressure from the branch port 54 of the summation relay 42 to the pneumatically operated electrical switch 14 is substantially a duplicate of the saw tooth pressure provided by the timing tank 30, but its level is adjustable by means of the summation relay bias and its level goes up and down as the thermostat output goes up and down. Thus, by proper calibration of the bias of the summation relay 42 and the trip and reset points of the pneumatically operated switch 14, the heaters or the refrigeration compressor of the heat exchanger means 11 will be turned on for a portion of each cycle unless the output of the summation relay is completely above or completely below the make" and break pressures of the pneumatically operated electrical switch 14, in which case the system will be either 100 percent on or I00 percent off.

For example, it is assumed in FIG. 2 that the horizontal line 54' indicates the pressure below which the pneumatically operated pressure switch 14 will not turn on the refrigeration means 11 and the horizontal line 55 indicates the pressure received by the pneumatically operated electrical switch 14 which will turn on the refrigeration means 11. The upper dash lines 56 for each timed cycle of the summation relay 42 represents the signal to the pneumatically operated electrical switch 14 when the thermostat output signal is low so as to provide a 100 percent refrigeration on time of the heat exchange means 11 during each time period of the repeating cycles of operation produced by the timing tank 30. In contrast, the lower dash line 57 in each time period illustrated in FIG. 2 represents the pressure directed to the pneumatically operated electrical switch 14 by the summation relay 42 during each time period when the output of the thennostat 48 is high so that the heat exchanging means 1 1 will be 0 percent on during each time period.

Thus, in this manner, it can be seen that the heat exchanging means 1 1 will be a certain percent on and a certain percent off for each time period represented by the saw tooth arrangement in FIG. 2 depending upon the particular magnitude of the signal being directed by the summation relay 42 to the electrical switch 14.

In this manner, the control system 10 is a better temperature control than a conventional on-off heat exchanging system where light load conditions allows overheating in heat systems and undercooling in cooling systems, particularly where slow thermal response of a thermostat is provided because the same produces an intolerable condition with the conventional on-off control even on steady load conditions.

However, the control system 10 of this invention provides a heat exchange output comparable to that obtained form a proportional action system making possible the use of cheap resistance heating and direct expansion cooling systems where the difficulty of good control has required the installation of more sophisticated control systems in the past.

The control system 10 of this invention is extremely flexible. The cycle time is adjustable by varying the bias on the volume booster relay 25 to give more or less pressure drop across the orifice 28. The trip and reset points of the diverting relay 19 (if adjustable) also can be utilized to vary the cycle time and the system throttling range as well. The thermostat 48 and pressure of the timing tank 30 inputs to the summation relay 42 can be reversed, which will reverse the action of the thermostat 48. This can be advantageous in designing a fail-safe system.

Also, by utilizing a multi-point summation relay 42, the thermostat throttling range can be narrowed by piping the thermostat output into more than one input. Thus, a system would be provided that would control on the basis of an average thermostat temperature by the piping of the outputs of more than one thermostat into the same summation relay.

Therefore, it can be seen the control system 10 of this invention provides not only for the operation of a heat exchange means, but also the various parts of this invention provides improved control means for other devices as desired.

The details of the various parts of the control system 10 previously described will now be described in detail.

DIVERTING RELAY 19 As illustrated in FIG. 3, the diverting relay 19 comprises a housing means 58 having the port means 18, 20, 22 and 45 formed therein.

The signal pressure port 20 leads to a chamber 59 formed in the housing means 58 and defined in part by a flexible diaphragm 60 being nonnally urged downwardly by a compression spring 61, the diaphragm 60 carrying a plunger 62 that is engageable with a lever 63 pivotally mounted to the housing 58 at a pivot point 64 intermediate the opposed ends 65 and 66 of the lever 63. A compression spring 67 normally urges the end 65 of the lever 63 into engagement with the pin 62. The other end 66 of the lever 63 comprises a valve member adapted to move between and seal against opposed valve seats 68 and 69 respectively being disposed in fluid communication with the

ports

45 and 18 as illustrated.

When the signal pressure in the chamber 59 of the diverter relay 19 is below the trip point thereof, the compression spring 61 maintains the flexible diaphragm 60 downwardly against the stop shoulder 70 as illustrated in FIG. 3 whereby the plunger 62 holds the lever 63 in the position illustrated in FIG. 3 so as to normally close the valve seat 68 whereby the supply pressure port 18 is fluidly interconnected through the open valve seat 69 to the branch port 22 and, thus, to the supply port 24 of the booster relay 25.

However, when the signal pressure at the port 20 exceeds the trip point setting of the diverter relay 19, the resulting pressure differential across the flexible diaphragm 60 causes the flexible diaphragm 60 to move upwardly in opposition to the force of the compression spring 61 so that the compression spring 67 causes the lever 63 to pivot in a clockwise direction about the pivot point 64 whereby the valve member 66 moves away from the valve seat 68 and into engagement with the valve seat 69 so that the source port 18 is closed and the branch port 22 is now interconnected to the atmosphere through the opened valve seat 68 and port 45 whereby the supply port 24 of the booster relay 25 is interconnected to the atmosphere through the atmosphere port 45 of the diverter relay 19.

When the signal at the port decreases below the reset pressure value of the relay 19, the resulting drop in pressure differential across the flexible diaphragm 60 permits the compression spring 61 to move the flexible diaphragm 60 downwardly and back to the position illustrated in FIG. 3 whereby the branch port 22 '5 again interconnected to the supply port 18 while the atmosphere port 45 is disconnected therefrom by the valve member 66 being disposed against the valve seat 68.

VOLUME BOOSTER RELAY WTH-l BIAS The volume booster relay 25 as illustrated in FIG. 5 comprises a housing means 70 carrying a pair of flexible diaphragms 71 and 72 disposed in spaced stacked relation to cooperate with the housing means 70 and defining three

stacked chambers

73, 74 and 75 with the

chambers

74 and 75 adapted to be interconnected together by a valve seat means 76 carried by the diaphragms 71 and 72 and being respectively interconnected to passage means 77 and 78 formed in the housing means 70. The pasage means 77 lads to the atmosphere while the passage means 78 defines the branch port 26 of the relay 25 that is interconnected to the conduit 27 at a point upstream Erom the orifice 28 as previously described.

The housing means 70 defines another valve seat 79 adapted to interconnect a pasage means 80 to the chamber 75, the passage 80 defining the supply port 24 of the relay 25 so as to be interconnected to the conduit means 23 leading from the branch port 22 of the diverting relay 19.

A movable valve mans 81 is carried by the housing mans 70 and has a first valve portion 82 adapted to open and close the valve seat 79, a second valve portion 83 of the valve means 81 being adapted to open and close the valve seat mam 76 of the diaphragm 72 as will be apparent hereinafter. A compression spring 84 is carried by the housing means 70 and normally tends to urge the valve mans 81 upwardly in FIG. 5 to have the valve portion 82 normally close the valve seat 79.

The housing means 70 has another pasage mans 84' formed therethrough and interconnecting with the chamber 73, the pasage 84' defining the signal port 34 of the relay 25 so as to be connected to the conduit 33 previously described.

Anadjustingspring85isdisposedinthechamber73andis interconnected to an adjusting screw 86 as well as to the valve seat means 76sothatthespringmeans85canactupordown on thediaphragmmeans'll and72to augmentoractagainst the control presure being directed to the chamber 75 and being opposed by the signal premre being directed to chamber 73.

Thus,shouldthesignalpressmeandchamber73beofsuch force in relation to the control pressure in chamber 75, the diaphragm mans 71 and 72 are moved downwardly whereby the valve seat mans 76 moves the valve mans 81 downwardly to open the valve seat 79 and increase the pressureinthechamber75 and, thus,thecontrolpressure.Conversely, should the control presure in chamber 75 exceed the signalpresureinthechamberfi by amountgreaterthnnthat set bytheadjustingscrew86,thecompresionspring84closes the valve means 81 againstthevalve seat79andthe pressure in the chamber 75 moves the diaphragms 72 and 71 upwardly incppositiontotheforceofthespringSStoopathevalve seat means 76 away from the valve portion 83 to exhaust some ot'the control pressure in the chamber 75 to the chamber 74 out through the pasage mans 77.

In thismannenthecontmlprmureinthechamberfiwill be equal to the signal presure in the chamber 73 plus or minus the setting of the spring 85 by the adjtstirzg screw 86 whereby for one psi change in the sign! presure in the chamber 73, there is a matching one psi change in the control presure in the chamber 75, but the control presure may be greater or les than the signal pressure depending upon the setting of the bias of the spring 85.

However, in the control system 10 of this invention, the spring is adjusted by the adjusting means 86 so that a certain pressure drop will always be maintained acres the orifice means 28 so that the control pressure in the chamber 75 will be higher than the signal presure in the chamber 73.

VOLUME BOOSTER RELAY 36 As illustrated in FIG. 4, the volume booster relay 36 is substantially identical to the volume booster relay 25 of FIG. 5 previously described except that there is no bias provided in the volume booster relay 36 so that the control pressure and the signal pressure will always be the same whereby the controi ressure will change the same amount when the signal presure is increased or decreased.

ln particular, the parts of the relay 36 similar to the relay 25 previously described are indicated by like reference numerals followed by the reference letter "A whereby it can be seen that the relay means 36 includes the housing means 70A carrying diaphragrns 71A and 72A cooperating therewith to define the three stacked chambers 73A. 74A and 75A. The diaphragm: 71A and 72A carry the valve seat means 76A that is adapted to opened and closed by the valve portion 83A of the valve means 81A having the portion 82A thereof opening and closing the valve seat mans 79A that interconnects the supply presure pasage means 80A with the branch pressure chamber 75A.

The chamber 74A is interconnected to the atmosphere by the pasage mans 77A while the chamber 73A is intercom nected by the passage mans 84A to the conduit 29 and the pasage mans 78A is interconnected to the conduit 40.

The pasage 80A is interconnected to the supply conduit 38 whereby the volume booster relay 36 in the control system 10 of this invention receives its pneumatic signal from the timing tank 30 and fumishes a control pressure equal thereto to the conduit mans 21 that directs that signal pressure to the

ports

20 and 41 of the diverting relay 19 and summation relay 42.

SUMMATION RELAY 42 As illistrated in FIG. 6, the summation relay 42 comprises a housng means 87 carrying four diaphragms 88, 89. 90 and 9! in stacked relation and being interconnected together to move in unison by a centrally d'spos d valve seat member 92 having a valve seat means 93 at the lower end thereof adapted to be opened and closed by the valve portion 838 of a valve means 818 fonned in the same manner as the alve means 81 previ ously described and normally being urged to a closed position against a valve seat mans 94 of the housing means 87 by a comprasion spring 95.

The four diaphragrm 88-91 cooperate with the housing means 87 to define five stacked

chambers

96, 97, 98, 99 and 100 with the chamber 96 being interconnected by a passage mans 101 to the atmosphere, the chamber 97 being interconnectedbyapasagemanslilltotheconduitllasthe 102definestheplusport4Lthechamber98 being interconnectedbyapasageliBtotheconduitSZasthe passage 103definr=tbemimmport53,thechamber99being interconnectedtotheatmospherebyapasage 104andthe chamber 100 being interconnected by a pasage 105 to the conduit15asthepssage l05definestheoutputport54. The valveseat94leaihtoapasagemeans l06thatdefines the supply port 43 and, thus, is interconnected by the conduit 44 to the srpply conduit 17.

Anadjustingspring l07iscarriedinthe chamber96andis interconnected to the valve seat member 92 and to an adjuning screw 108 so that the spring force thereof acting on the diaphragm stack can be varied as desired.

The summation relay 42 is balanced and in equilibrium only when all the up and down force: are equal. The control or output pressure in the chamber 100 preset. upwardly on the effective area of the diaphragm 91 and the minus signal in the chamber 98 preses upwardly on the difference between the effective areas of the diaphragrns 90 and 89. the plus signal in the chamber 97 pushing downwardly on the difference between the effective area of the diaphragrns 88 and 89 with the spring 107 acting up or down according to its adjustment.

Since the

diaphragms

91, 90 and 88 have the same effective area and the diaphragm 89 has an effective area twice as large as the other diaphragms. the control pressure in the chamber 100 is expressed as equalling the force of the plus signal in the chamber 97 minus the force of the minus signal in the chamber 98 plus or minus the force of the spring 107.

PNEUMATICALLY OPERATED THERMOST AT 48 As illustrated in FIG. 7. the pneumatically operated thermostatic means 48 comprises a housing means 109 provided with a pasage means 110 that defines the supply port 49 that is interconnected to the supply conduit 17 by the conduit 50, the passage 110 leading to a chamber 111 that hm a valve seat 112 connected to a chamber means 113 that leads by a pasage means 1 14 to the conduit 52 as the pasage 114 defines the output port 51 thereof. The chamber 113 is defined by a flexible diaphragm 115 that carries a member 116 fulcrumed on a fulcrum 117 ofthe housing means 109 intermediate the

ends

118 and 119 of the beam or lever 116. The end 118 ofthe beam 116 has a valve seat 120 that is adapted to be opened and closed by a valve portion 121 of a valve mears 122 having its larger portion 123 normally urged to the closed position against the valve seat 112 by a compression spring 124. The valve seat 120 leads by a passage means 125 to the atmosphere.

The chamber 111 of the housing means 109 leads through a restrictor 142 to another chamber 126 of the housing means 109 also being defined in part by the diaphragm 115 with the chamber 126 acting on the end 119 ofthe beam 116 in opposition to a compression spring 127 normally tending to urge the beam end 119 downwardly in FIG. 7 as the compression spring 127 is disposed against thestationary part 128.

The chamber 126 is connected by a pasage means 129 to a nozzle leak port 130 that is opened and closed by a bimetallic leak port lever 131 supported on the end 132 of an operating arm 133 fulcrumed at 134 and having an adjustable screw 135 at the end thereof bearing against an adjustable cam 136 A compresion spring 137 is dkposed between the operating arm 13 and a leaf spring prmure plate 138 cantilevered to the housing means 109 by a fastening means 140 and bearingagainstthediaphragn 115 ataportionthereofthat cooperates with the housing 109 to define a feedback chamber 141 interconnected by a pmage means 142' in the housing 109 to the chamber 1 13.

Theser ointofthethermostatuisadjustedbythecam 136, rotation of which changes the attitude of the operating arm 133 and thereby changes the temperature at which the bimetallic leak port lever 131 will close the leak port nomle 130.

'Ihusitcanbeseenthatthesupplyairtlowsintothe chamber 111 and is channeled through the restn'ctor 142 to thecharnber 126whichisinterconnectedtotheleakportnozzle 130. Restrictionattheleakportnonle 130bythebimetallicmember 131 sensingtheternperamrecausesanincreasein presure intheehamber 126which movestheend l19ofthe beam ll6upwardlyinoppositiontotheforceot'thecompression spring 127 and cam the end 118 thereof to push downwardly on the valve means 122 and open the valve seat lllpermitringaninaeaseinpressureflowintothediamber 113 and. thus. to the minus port53ofthe summation relay42. However. the inc-rm in presume in the chamber 113 acts agaimtthediaphragm 115tomovethesameupwardlytorock the beam 116 in a counterclockwise direction whereby the presureinthecharnbc' 1l3isinrelationtotheamountof opening or clomg of the leak port nozzle 130 by the bimetallic member 131 sensing the output temperature effect for the heat exchanger means 11.

THE PNEUMA'I'ICALLY OPERATED ELECTRICAL SWITCH 14 The pneumatically operated electrical switch 14 is illustrated in FIG. 8 and comprises a housing means 143 carrying a flexible diaphragm 144 that cooperates therewith to define a chamber 145 interconnected by a pasage means 146 to the conduit 15. The diaphragm 144 at the chamber 145 carries an actuator 147 abutting against an end 148 of a lever 149 pivotally mounted at 150 to an electrical switch 151 that has an operating plunger 152 bearing against the other end 153 of the lever 149. The end 148 of the lever 149 is urged in a downward direction in FIG. 8 by a compression spring 154 having its upper end 155 Bearing against an adjusting member 156 carried by a stationary frame means 157.

Thus, it can be seen that when the pressure in the chamber 145 exceeds the force of the compression spring 154. the diaphragm portion 144 moves upwardly to move the end 153 of the lever 149 downwardly in FIG. 8 to cause the plunger 152 of the switch 151 to either turn on the heat exchanger means 1 1 or turn 06 the same as the cme may be. Conversely, when the presure in the chamber 145 is les than the force of the compression spring 154 opposing the same, the diaphragm 144 moves downwardly to the position illustrated in FIG. 8 so that the end 153 of the lever moves upwardly to hold the plunger 152 in the position illustrated in H6. 8 whereby the heat exchanger means 11 is either in an on or off condition as the case may be.

OPERATION From the above detailed description of the various components of the control system 10 of this invention. it can readily be seen that the previously described operation of the control system 10 can eflectively control the on-otf heat exchanger means 11 in the manner previously described.

In particular, the detailed operation of the control system 10 will now be described.

It is mined that the heat exchanging means 11 is for cool ing and comprises a refrigeration compressor which when turned on produces a cooling output ellect. It is also assumed that the birnetal member 131 of the thermostat means 48 moves away from the leak port 130 as the temperature rises and that the electrical switch 151 in order to turn on the heat exchanging means 11 must have its plunger 152 moved downwardly by the upward moving of the diaphragm 144.

The supply air from the source 16 into the conduit means 17 can be approximately 25 psi and is directed to the normally opened port 18 and normally opened valve seat 69 so as to be in direct communication with the outlet port 22 thereof that leads to the supply port or passage of the volume booster relay 25. With the timing tank 30 being at its lowest pressure, the signal therefrom to the volume booster relay 36 is such that the same provides a corresponding control pressure in the chamber 75A that leads to the

chambers

97 and 59 of the summation relay 42 and diverter valve 19. Since this pressure in the chamber 59 of the diverter valve 19 is below the set point thereof 5 provided by the spring 61, the diverting valve 19 remains in the position illustrated in FIG. 3 to continuously supplypresineairtothepasagemeanswofthevolume boomer relay is. Since the signal being received in the chamber 73 of the relay 15 is less than the control presiire in thechamber75becauseoftheorifice28intheconduit 27, the relay 25 continuously increases the control presure out of thepasagemeansmthereofintotheeonduitflsoastc progresivelyincresedaepresureinthetimingtankSQ Asthepresureinthetirningtanklloincreasesthepressure to the plus chamber 97 of the summation relay 42 co:- respondingly increases to tend to increase the pressure at the contmlcharnberoftherelay42thatisdirectedtothe chamber or'the switch means 14 as represented by the line 47 in H0. 2.

However, ifthe thermostat means 48 is demanding an increased cooling efl'ect of the heat exchanger means 11. the birnetal member 131 moves farther away from the leak port 130 to decrease the pressure in the chamber 113 and, thus, the pressure to the minus chamber 98 of the summation relay 42 so that the net effect of the summation relay 42 is to provide an increasing pressure to the chamber 145 of the switch means 14 to cause the heat exchanger means 11 to be turned on when such pressure to the switch 14 is above the horizontal line 55 in FIG. 2.

Such increasing pressure in the timing tank 30 continues until the pressure in the chamber 59 of the diverter relay 19 exceeds the force of the compression spring 61 and moves the diaphragm 60 upwardly to close the valve member 66 against the valve seat 69 and, thus, interconnect the atmosphere at the port 45 to the port 22 and, thus, to the passage 80 of the relay 25. With the passage 80 now interconnected to the atmosphere, the conduit 27 upstream of the check valve 31 and FIG. 1 is now at atmospheric pressure so that the pressure in the conduit 27 downstream of the check valve 31 opens the check valve 31 to exhaust the pressure in the timing tank 30 so that the pressure signal being directed to the chamber 59 of the diverter relay l9 falls 011' to a level which permits the spring 61 to reset the diverter relay 19 back to the position illustrated in FIG. 3 so as to begin the timing operation of the pressure regulation of the timing tank 30 all over again.

Therefore, it can be seen that this invention not only provides an improved system and method of operating a exchanger means or the like, but also this invention provides improved parts for such a control system or the like.

While the form of the invention now preferred has been disclosed as required by the statutes, other forms may be used, all coming within the scope of the claims which follow.

What is claimed is:

l. A control system comprising an on-off" heat exchanger means, a pneumatically operated actuator having a first condition for maintaining said heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatic means for automatically creating and directing a pneumatic signal to said actuator that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately to 100 percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic means comprising a pneumatic timing tank and a passage defining means and a diverting relay means for pneumatically charging said tank through said passage defining means in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage defining means in the opposite flow direction thereof so as to thereafter repeat the charging cycle, said diverting relay means having restriction means in said passage defining means and through which said tank is charged with pressure, said diverting relay means having by-pass means in said passage defining means by-passing around said restriction means for rapidly exhausting said tank at the end of each charging cycle thereof.

2. A control system as set forth in claim 1 wherein said automatic means provides said pneumatic signal with a substantially linear magnitude during each predetermined time period.

3. A control system as set forth in claim 1 wherein said automatic means provides said pneumatic signal with an increasing magnitude during each predetermined time period.

4. A control system as set forth in claim 1 wherein said actuator comprises a pneumatically operated electrical switch construction.

5. A control system as set forth in claim 1 wherein said automatic means comprises a pneumatically operated control relay means that directs said signal to said actuator in relation to pneumatic signal means imposed on said control relay means.

6. A control system as set forth in claim 5 wherein a condition responsive device provides part of said pneumatic signal means to said control relay means, said condition responsive device providing said part of said pneumatic signal means with a magnitude in relation to the condition sensed by said device.

7. A control system as set forth in claim 6 wherein said condition responsive device is a temperature responsive device that senses the output temperature effect of said heat exchanger means.

8. A control system as set forth in claim 6 wherein said diverting relay means provides the remaining part of said pneumatic signal means to said control means, said diverting relay means providing said remaining part of said signal means with a substantially linear magnitude during each predetermined time period.

9. A control system as set forth in claim 8 wherein said control relay means is a summation relay means that provides its pneumatic signal to said actuator in relation to the difference between said two parts of said pneumatic signal means.

10. A method of controlling an on-off heat exchanger means comprising the steps of providing a pneumatically operated actuator having a first condition for maintaining said heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatically creating and directing a pneumatic signal to said actuator that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately 0 to percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic step comprising the steps of providing a pneumatic timing tank and a diverting relay means for pneumatically charging said tank through a passage in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage in the opposite flow direction thereof so as to thereafter repeat the charging cycle, charging said tank through restriction means in said passage of said diverting relay means, and by-passing around said restrictor means for rapidly exhausting said tank at the end of each charging cycle thereof through by-pass means of said passage of said diverting relay means.

11. A method as set forth in claim 10 wherein said automatic step comprises the step of providing said pneumatic signal with a substantially linear magnitude during each predetermined time period.

12. A method as set forth in claim 10 wherein said automatic step comprises the step of providing said pneumatic signal with an increasing magnitude during each predetermined time period.

13. A method as set forth in claim 11 wherein said actuator comprises a pneumatically operated electrical switch construction.

14. A method as set forth in claim 10 wherein said automatic step comprises the step of providing a pneumatically operated control relay means that directs said signal to said actuator means in relation to pneumatic signal means imposed on said control relay means.

15. A method as set forth in claim 14 and including the step of providing part of said pneumatic signal means to said control relay means by a condition responsive means that provides said part of said pneumatic signal means with a magnitude in relation to the condition sensed by said device.

16. A method as set forth in claim 15 wherein said condition responsive device is a temperature responsive device that senses the output temperature effect of said heat exchanger means.

17. A method as set forth in claim 15 and including the step of providing the remaining part of said pneumatic signal means to said control relay means with said diverting relay means that provides said remaining part of said signal means with substantially linear magnitude during each predetermined time period.

18. A method as set forth in claim 17 wherein said control relay means is a summation relay means that provides its pneumatic signal to said actuator in relation to the difference between said two parts of said pneumatic signal means.

19. In combination, a pneumatically operated actuator having a first condition for maintaining an on-off" heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatic means for automatically creating and directing a pneumatic signal to said actuator that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately to 100 percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic means comprising a pneumatic timing tank and a passage defining means and a diverting relay means for pneumatically charging said tank through said passage defining means in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage defining means in the opposite flow direction thereof so as to thereafter repeat the charging cycle, said diverting relay means having restriction means in said passage defining means and through which said tank is charged with pressure, said diverting relay means having bypass means in said passage defining means bypassing around said restriction means for rapidly exhausting said tank at the end of each charging cycle thereof.

20. A combination as set forth in claim 19 wherein said automatic means provides said pneumatic signal with a substantially linear magnitude during each predetermined time period.

21. A combination as set forth in claim 19 wherein said automatic means provides said pneumatic signal with an increasing magnitude during each predetermined time period.

22. A combination as set forth in claim 2! wherein said actuator comprises a pneumatically operated electrical switch construction.

23. A combination as set forth in claim 19 wherein said automatic means comprises a pneumatically operated control relay means that directs said signal to said actuator means in relation to pneumatic signal means imposed on said relay means.

24. A combination as set forth in claim 23 wherein a condition responsive device provides part of said pneumatic signal means to said control relay means, said condition responsive device providing said part of said pneumatic signal means with a magnitude in relation to the condition sensed by said device.

25. A combination as set forth in claim 24 wherein said condition responsive device is a temperature responsive device.

26. A combination as set forth in claim 24 wherein said diverting relay means provides the remaining part of said pneumatic signal means to said relay means, said diverting relay means providing said remaining part of said signal means with a substantially linear magnitude during each predetermined time period.

27. A combination as set forth in claim 26 wherein said control relay means is a summation relay means that provides its pneumatic signal to said actuator in relation to the difference between said two parts of said pneumatic signal means.

t l t i

Claims

1. A control system comprising an ''''on-off'''' heat exchanger means, a pneumatically operated actuator having a first condition for maintaining said heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatic means for automatically creating and directing a pneumatic signal to said actuator that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately 0 to 100 percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic means comprising a pneumatic timing tank and a passage defining means and a diverting relay means for pneumatically charging said tank through said passage defining means in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage defining means in the opposite flow direction thereof so as to thereafter repeat the charging cycle, said diverting relay means having restriction means in said passage defining means and through which said tank is charged with pressure, said diverting relay means having by-pass means in said passage defining means by-passing around said restriction means for rapidly exhausting said tank at the end of each charging cycle thereof.

10. A method of controlling an '''' on-off'''' heat exchanger means comprising the steps of providing a pneumatically operated actuator having a first condition for maintaining said heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatically creating and directing a pneumatic signal to said actuator that varies in magnitude ovEr each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately 0 to 100 percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic step comprising the steps of providing a pneumatic timing tank and a diverting relay means for pneumatically charging said tank through a passage in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage in the opposite flow direction thereof so as to thereafter repeat the charging cycle, charging said tank through restriction means in said passage of said diverting relay means, and by-passing around said restrictor means for rapidly exhausting said tank at the end of each charging cycle thereof through by-pass means of said passage of said diverting relay means.

19. In combination, a pneumatically operated actuator having a first condition for maintaining an ''''on-off'''' heat exchanger means in an off condition thereof as long as the pneumatic signal thereto is in a first magnitude range and having a second condition for maintaining said heat exchanger means in an on condition thereof as long as the pneumatic signal thereto is in a second magnitude range, and automatic means for automatically creating and directing a pneumatic signal to said actuator that varies in magnitude over each predetermined time period in a repeating cycle of said time periods so that the first condition and second condition of said actuator will be both variable in relation to each other from approximately 0 to 100 percent of the time in each time period depending upon the magnitude range of said pneumatic signal in each time period, said automatic means comprising a pneumatic timing tank and a passage defining means and a diverting relay means for pneumatically charging said tank through said passage defining means in one flow direction thereof for each predetermined time period and for then discharging said tank back through said passage defining means in the oppoSite flow direction thereof so as to thereafter repeat the charging cycle, said diverting relay means having restriction means in said passage defining means and through which said tank is charged with pressure, said diverting relay means having bypass means in said passage defining means by-passing around said restriction means for rapidly exhausting said tank at the end of each charging cycle thereof.

22. A combination as set forth in claim 21 wherein said actuator comprises a pneumatically operated electrical switch construction.