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Publication numberUS2767277 A
Publication typeGrant
Publication dateOct 16, 1956
Filing dateDec 4, 1952
Priority dateDec 4, 1952
Publication numberUS 2767277 A, US 2767277A, US-A-2767277, US2767277 A, US2767277A
InventorsWirth James F
Original AssigneeWirth James F
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Control system for power operated fluid pumps
US 2767277 A
Abstract  available in
Images(2)
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Claims  available in
Description  (OCR text may contain errors)

J. F. WlRTH Oct. 16, 1956 CONTROL SYSTEM FOR POWER OPERATED FLUID PUMPS Filed Dec. 4 1951 2 Sheets-Sheez l Oct. 16, 1956 J. F. wlRTH 2,767,277

CONTROL SYSTEM FOR POWER OPERATED FLUID PUMPS Filed Deo. 4, v1951 2 sheets-sheet 2 75/ 7X e V 72 e United States Patent Oiice CONTROL SYSTEM FOR POWER OPERATED FLUID PUMPS James F. Wirth, Minneapolis, Minn.

Application December 4, 1952, Serial No. 324,018

1 Claim. (Cl. 200-83) My invention relates generally to controls for iluid pressure systems and more particularly to a control system for power operated fluid pumps.

More specically, my invention is in the nature of a control mechanism for terminating the operation of a iluid pump when the normal ow of fluid through the pump is interrupted. Such interruption may be the result of any one of a number of conditions, such as, for instance, a deficiency of the fluid at the source, obstructions occurring in the system, or the accidental or intentional shutting od of the flow at the outlet end of the system. It is known that arrangements utilizing pressure operated switches broadly are old in the art. Such arrangements have included pressure operated mechanisms interposed between the pump and the tluid outlet of the system and have been dependent upon an unusual rise or drop in pressure to terminate the pumping action. The above described arrangement usually requires a relatively costly and elaborate installation, which at best, does not meet every contingency which may occur in various fluid pressure systems. An important object of my invention is, therefore, the provision of a fluid pressure system having control mechanism which is in free communication with the negative pressure inlet side of a pump whereby to terminate operation of the pump immediately upon loss of said negative pressure.

Another important object of my invention is the provision of control mechanisms for iluid pressure systems as set forth, utilizing a single control device for initiating operation of pressure generating means and for automatically terminating the operation thereof upon interruption of the flow of uid through the system.

Another object of my invention is the provision of control mechanism as set forth which is relatively simple and inexpensive to manufacture, which may be quickly and easily installed in an existing fluid pressure system, which is efcient in operation, and which is rugged in construction and durable in use.

The above and still further highly important objects and advantages of my invention will become apparent from the following detailed specification, appended claim and attached drawings.

Referring to the drawings, which illustrate the invention and in which like characters indicate like parts throughout the several views:

Fig. l is a fragmentary view in side elevation of a fluid pressure system and control means therefor incorporating my invention, some parts being broken away and some parts being shown in section;

Fig. 2 -is a vertical section taken substantially on the line 2-2 of Fig. l;

Fig. 3 is a view partly in plan and partly in horizontal section taken substantially on the line 3--3 of Fig. l on a reduced scale;

Fig. 4 is a wiring diagram;

Fig. 5 is a fragmentary view in front elevation of the control switch housing of my invention;

Fig. 6 is a View partly in side elevation and partly 2,767,277 Patented Oct. 16, 1956 diagrammatic of a modilied form of the invention, some parts being broken away and some parts being shown in section; and

Fig. 7 is a fragmentary View corresponding to a portion of Fig. l showing a still further modied form of control mechanism of my invention.

Referring with greater detail to the drawings and more particularly to the preferred embodiment of the invention illustrated in Figs. 1 to 5 inclusive, a uid pressure system 1s illustrated as comprising a uid pressure pump l coupled at its inlet 2 to conduit means 3 and at its outlet or delivery end 4 to a delivery conduit 5. The conduit means 3 comprises conduit pipes or conduits 6 and 7 connected by a fitting 8 and an intake screen or the like 9 which is adapted to be submerged in liquid to be displaced. The delivery conduit 5 may be assumed to eX- tend to the desired point of delivery and may if desired be provided at or adjacent its delivery end with suitable nozzle or valve means not shown. The pump 1 is conventlonal in nature and is preferably of the constant delivery type incorporating an impeller rotor not shown, but which may be assumed to be mounted on a shaft 1l) that 1s coupled to the shaft of an electric motor 11. The impeller shaft 10 on the pump 1 is normally driven by the motor 11 in a direction under which the delivery outlet 4 1s under a positive pressure greater than that of the surrounding atmosphere. By the same token the inlet 2 of the pump 1 and the conduit means 3 connected thereto 1s placed under a sub-atmospheric or negative pressure. These conditions are normal with conventional fluid pressure systems.

My novel control mechanism for the fluid pressure system above described comprises a two-position switch 12 lnterposed in an electric circuit for the motor 11, a pressure responsive element 13 and operating connections therebetween and the switch 12. The pressure responsive element 13 is in the nature of a relatively thin flexible dlaphragrn 14 which cooperates with an open-topped cupshaped member 15 to define a chamber 16. The perlpheral edge portion of the diaphragm 14 is interposed between a circumferentially extended ange 17 integrally formed with the member 15 and a similar iange 18 of a downwardly opening cup-shaped member 19 similar to the member 15 and disposed in over-lying relationship thereto. The marginal edge portion of the diaphragm 14 1s clamped between the flanges 17 and 18 by a pluralrty of circumferentially spaced nut-equipped clamping screws or the like 20. The member 15 is provided at its central portion with a tubular boss 21 having a central opening 22 aligned with an opening 23 in the member 15. The opening 22 adjacent the lower end of the boss 21 is screw threaded to receive the upper screw thread end of a p1pe nipple 24 that has its lower end screw threaded into the tting 8, whereby the chamber 16 is in free communication with the negative pressure inlet 2 of the pump 1 through the conduit element 6.

The switch 12 includes a body 25 preferably made from insulating material such as synthetic resin or the like suitably mounted in a housing member 26 that is screwed or otherwise mounted on a base member 27 as indicated at 28. The base member 27 rests upon the inverted cupshaped member 19 and is anchored thereto by screws or the like 29. The switch 12 is preferably of the double contact type having a pair of laterally spaced contact elements 30 and 31 one each connected to an opposite side of a two wire power line 32 by means of leads 33 and 34 respectively, see particularly Fig. 4. Another pair of spaced contact elements 35 and 36 are connected -to the motor 11 by means of respective leads 37 and 38. The contact elements are rigidly secured in the conventional rnanner to the switch body 25, and are adapted to be engaged by connector bars 39 and 40, the former of which overlies the contact elements and 35 and which is movable into and ,out of circuit closingengagement therewith, andthe latter of which overlies the contact elements 31 and 36 and which is movable into'and out of circuit closing engagement therewith. Obviously, the connector bars 39 and 40 are made from metal having relatively high electrical conducting qualities such as copper or brass. The connector bars 39 and 40 are yieldingly biased toward engagement with their respective contact elements by relatively light coil compression springs 41 and 42 and are supported intermediate their ends by a pusher plate or the like 43 which is preferably made from insulating material such as hard rubber, synthetic resin or'the like. The ,pusher plate 43 is guided for vertical movements in a pair of opposed channels 44 in the switch body 25, and .rests upon Vthe intermediate portion of a manually operated lever 45 which is loosely hinged as indicated at its rear end 4-6 to a bracket 47 rigidly secured to the base member 27, see Figs. 2 and 3. The front end of the lever 45 projects outwardly through an L-shaped opening 4S in the switch housing 26 within easy reach of the operator, see Figs. l, 3 and 5.

The above mentioned connections between the switch 12 and the pressure responsive element 13 includes the operating lever 45 and a rigid link in'the naturerof a post 49 that is rigidly secured at its lower end to the diaphragm 14 by a washer-equipped machine screw or the like Sli and which at its upper end is provided with a headed retaining pin or screw 51 that extends downwardly through an aperture 52 in the lever 45 and into the upper end of the post 49. As shown in Figs. l and 2, the post 49 extends upwardly through aligned apertures 53 and 54 in the central portions of the member 19 and the switch housing base member 27. A coil compression spring 55 is interposed between `the base'member 27 and the operating lever 45 and encompasses the post 49 therebetween. rl`he spring 55 is of a size and weight to overcome the pressure of the relatively light springs 41 and 42, so that normally the switch 12 is in a switch open position.

ln use, the pump driving motor 11 is energized by manually depressing the level 45'against yielding bias of the spring 55 to permit the springs 41 and 42 to move the bars 39 and d@ downwardly into circuit closing engagement with their respective contact elements. With reference to Fig. 5, it will be seen that the L-s'haped opening 48 denes a stop shoulder 48. The aligned apertures 53 and 54 are suciently large, and the diaphragm '14 suiciently flexible to permit the lever 45 to be moved laterally into engagement with the stop shoulder 48. The yielding bias of the spring 55 is lsu'tticient to frictionally maintain the lever 45 against the stop shoulder 48 as long as the chamber 16 is maintained at atmospheric pressure. As kiluid is drawn into the pump 1 from the intake member 9 and forced outwardly through the delivery conduit 5, a sub-atmospheric or negative pressure is set up in the chamber 16 suliicient to maintain the diaphragm 14 and the parts carried thereby in a switch closed position as indicated by dotted lines in Fig. 2. Immediately upon achievement of sub-atmospheric or negative pressure within the chamber 16, the lever 45 will be pulled downwardly by the diaphragm 14 away from engagement thereof from the stop shoulder 48 whereupon said lever 45 willassume `its normal position at one side of the stop shoulder 48 and within the vertical leg 48 of the opening 43 and as indicated in Figs. l and 3. ln other words, the operator may come as desired, initiate operation of the motor 11 by manually holding the lever 45 in a depressed position until negative pressure is formed within the chamber 16, or he might move the lever 45 downwardly and laterally into engagement with-the'stop nshoulder d8 and release the same, thus enabling the operator to be engaged in other activity during the relatively short time needed for negative pressure to be built up within-the chamber 16. As long as there is a normal flow of fluid through the pump 1, a negative pressure will be present within the chamber 15 and the switch 12 will remain closed until the lever 45 is manually raised against said negative pressure to move the switch 12 to its open position. In the event that the supply of uid at the intake end 9 becomes exhausted, air will be drawn into the intake conduit 3 in suicient quantity to cause a loss of the negative pressure within the chamber 16 thus permitting the spring 55 to open the switch 12 and deenergize the motor 11 and terminate operating of the pump 1i Similarly, if the ilow of uid through the system is cut off at the outlet end of the delivery conduit 5, either due to the shutting on` of a valve by the operator or due to accumulation of foreign matter in the delivery conduit, the negative pressure at the inlet side of the pump will be automatically reduced and the switch 12 will open. Moreover, if for any reason the pump itself should fail todraw properly, noV negative-pressure will occur at the intake side of the pump and the switch will move to its switch open position as soon as the operator releases initial starting pressure on the lever 45. From the above it should be obvious that the pump and motor may be shut oil by the operator at the delivery end of the delivery conduit 5 even though said delivery end is a substantial distance away from the pump, simply by manually shutting oli the flow of water at the delivery end. The motor and pump will remain inoperative until the lever 45 1s again manually depressed.

In the modified arrangement illustrated in Fig. 6, a pump 1 is shown as being provided with an inlet 2 and an outlet 4', the former of which is coupled to conduit means 3 by means of a pipe 6' and a fitting S', and the latter of which is connected to a delivery conduit 5', all in the manner of the structure of the Figs. l to 5 inclusive. The pump 1 is driven by a conventional internal cornbustion engine 5o having a combustion chamber 57 into one wall of which is screw threaded a conventional spark plug 53. Control mechanism *for the fluid pressure pump comprises a pressure responsive element in the nature of a diaphragm 1d mounted between a pair of opposed cooperating cup-shaped members 15 and 19', the former of which is coupled to the fitting 3 by a nipple or the like 24. A two-position switch 59 comprises a relatively stationary Contact element el? and a movable contact element 6l. that is mounted on a resilient metallic arm 62 anchored to a mounting plate 63 as indicated at 6d. The mounting plate 3 is carried by a switch housing member 26 that is rigidly secured to a base member 27 suitably anchored to the cup-shaped member 19. The arm 62 is yieldingly biased in a direction to maintain the contact elements 6b and 61 in a spaced apart relationship, and is movable in a direction to close an electric circuit through said Contact elements by a plunger rod or the like 65 mounted on a lever d5. The lever 45' is coupled to the diaphragm 1d' by a rigid link or post 49 and is yieldingly biased toward engagement of the plunger 65 with the resilient switch arm 62 by a coil compression spring 55" interposed between the lever 45' and the base member 27. it should be noted that the elements bearing prime marks in Fig. 6 are identical to corresponding'elements in Figs. l to 5 inclusive bearing lthe same reference characters without the prime marks.

ln this form of the invention, the contact element 6) is connected intermediate the ends of a power lead 65 that is shown as being connected at one end to the spark plug 58 and whichV may be assumed to be connected at its other end to a spark coil or similar ignition system. The spark plug 58 is grounded through the internal combustion engine 36 in the usual manner and as indicated at 67. The switch arm 62 is grounded through a lead 63 and the engine 56.

Operation of the engine 56 may be initiated only if the switch Contact elements 6l) and 61 are in a spaced apart switch open relationship. Thus the lever 45 must be manually depressed and held in a depressed switch open position until the engine S6 is in operation for a suflieient time to cause negative pressure to be built up in the chamber defined by the diaphragm 14 and the cup-shaped member 1S. Thereafter, if for any reason a loss of negative pressure occurs in the intake side of the system, the spring 55 will be permitted to move the contact element 61 into switch closing engagement with its cooperating contact element 60 thereby shunting the circuit to the spark plug 58 and causing the engine S6 to stop.

ln the modified arrangement illustrated in Fig. 7, parts corresponding to similar parts in Figs. 1 to 5 inclusive carry identical reference characteristics with the exponent a added. This form of the invention illustrates a remote control arrangement for causing the lever 45a to be depressed to move a switch, not shown, to a motor operative position. Suitably mounted to the base member 27a is a solenoid coil 69 having mounted therein a plunger 70 which extends through a suitable aperture in the lever 45a and which is provided at its upper end with a head 71 adapted to rest upon the upper surface of the lever 45a. The solenoid coil 69 is interposed in an electrical circuit comprising a lead wire 72 that is connected at its opposite ends to a source of electrical potential such as a pair of power Wires 73 and 74. A normally open momentary contact push button switch 75 is interposed in the lead wire 72 for the purpose of energizing the solenoid 69. With this arrangement, the operator may be stationed remote from the system and by merely closing the switch 75 will cause the solenoid 69 to be energized to depress the lever 45a in the same manner that vthe lever is depressed manually in the structure of Figs. 1

to 6 inclusive. This arrangement is preferably used in connection with a switch, not shown, but which may be assumed to be similar to the switch 12 of Figs. 1 to 5 inclusive.

While I have shown and described a commercial form of my novel fluid pressure system and control means, it will be understood that the same is capable of modication without departure from the spirit and scope of the invention as defined in the claim.

What I claim is:

1n a tluid-pressure-operated control switch, structure defining a chamber adapted to be connected in communication with a source of tluid under negative pressure, said chamber being defined in part by a pressure responsive movable element, a housing mounted on said structure, said housing having an opening in one Wall thereof, said opening having an offset portion adjacent one end thereof, means operatively coupling said movable element to said switch and including a manually operable member extending outwardly through said opening in the housing wall and a rigid link anchored at one end to said movable element and connected at its other end to said manually operable member, yielding means urging said movable element and coupling means in a direction to open said switch, said movable element being operative responsive to negative pressure in said chamber to close said switch against bias of said yielding means, said manually operable member being manually movable into the offset portion of said opening whereby to engage the housing wall deining said offset portion of the opening to hold said switch in a switch closed position in the absence of negative pressure in said chamber, generation of negative pressure in said chamber causing said manually operable member to be disengaged from the housing wall in the offset portion of said opening and moved laterally away from said oiset portion of the opening.

References Cited in the tile of this patent UNITED STATES PATENTS 1,655,683 Standerwick Jan. 10, 1928 1,698,693 Durdin Jan. 8, 1929 1,832,620 Cook et al. Nov. 17, 1931 2,357,440 Williams Sept. 5, 1944 2,453,156 Neracher et al Nov. 9, 1948 2,645,409 Lawler July 14, 1953 2,680,168 Murphy June 1, 1954 FOREIGN PATENTS 994,549 France Aug. 8, 1951

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1655683 *Apr 23, 1926Jan 10, 1928GektRegulating mechanism fob turbine-driven centrifugal compressors
US1698693 *Jul 16, 1927Jan 8, 1929 Pumping apparatus
US1832620 *Jul 9, 1928Nov 17, 1931Johnson Motor CompanyPump
US2357440 *Feb 8, 1943Sep 5, 1944Williams Philip HSwitch
US2453156 *Nov 13, 1939Nov 9, 1948Chrysler CorpServomotor
US2645409 *May 17, 1948Jul 14, 1953Boeing CoAir induction system heating in supercharged engine
US2680168 *Jul 7, 1952Jun 1, 1954Murphy Frank WSafety switch
FR994549A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2918011 *Sep 17, 1956Dec 22, 1959Jabsco Pump CoPump control system
US2923790 *Dec 27, 1957Feb 2, 1960Ernst John JPositive action low pressure pump cutoff switch attachment
US2933570 *Jan 6, 1958Apr 19, 1960Kenco Pump Division Of The AmePressure sensitive pump control
US3046964 *Jan 11, 1960Jul 31, 1962Chery Walter VAutomobile starting device
US3080890 *Apr 2, 1959Mar 12, 1963Cutler Hammer IncPressure responsive operator
US3114320 *Dec 11, 1961Dec 17, 1963George W HughesSand trap for pump by-pass line to motor control switch diaphragm
US3217653 *Mar 9, 1961Nov 16, 1965Donald G GriswoldValves and automatic controls
US3278704 *Sep 14, 1964Oct 11, 1966Leo Smith HenryPressure-actuated circuit breaker
US3302574 *Jan 14, 1965Feb 7, 1967Davco Mfg CorpPressure responsive pump control
US3408468 *Oct 28, 1966Oct 29, 1968Ite Circuit Breaker LtdDifferential pressure actuated switch utilizing high speed latch and lost motion means
US3414661 *May 19, 1965Dec 3, 1968Massachusetts Inst TechnologyHigh temperature furnace
US3433911 *Oct 12, 1966Mar 18, 1969Ite Circuit Breaker LtdDifferential pressure actuated switch with high speed latch means
US3457865 *Mar 20, 1967Jul 29, 1969Dunlap Robert BControl apparatus
US3575563 *Feb 10, 1969Apr 20, 1971Russell Carl DexterAxis translator switching mechanism
US4036404 *May 7, 1976Jul 19, 1977Auto-Chlor SystemMeans for indicating dishwasher additive absence
US4056333 *Nov 26, 1975Nov 1, 1977ValleylabIntravenous feeding pump failure alarm system
US4828545 *Apr 16, 1987May 9, 1989Omni-Flow, Inc.Pressure responsive multiple input infusion system
US5100380 *May 16, 1989Mar 31, 1992Abbott LaboratoriesRemotely programmable infusion system
US5304126 *Dec 31, 1990Apr 19, 1994Abbott LaboratoriesInfusion system having plural fluid flow lines
US5375650 *Nov 13, 1992Dec 27, 1994Nec CorporationLiquid coolant circulation control system for immersion cooling systems
US5458185 *Sep 29, 1994Oct 17, 1995Nec CorporationLiquid coolant circulation control system for immersion cooling
US5464392 *Mar 7, 1994Nov 7, 1995Abbott LaboratoriesInfusion system having plural fluid input ports and at least one patient output port
US5570481 *Nov 9, 1994Nov 5, 1996Vico Products Manufacturing Co., Inc.Suction-actuated control system for whirlpool bath/spa installations
US6059536 *Jan 21, 1997May 9, 2000O.I.A. LlcEmergency shutdown system for a water-circulating pump
US6342841Apr 9, 1999Jan 29, 2002O.I.A. LlcInfluent blockage detection system
US7690897Oct 13, 2006Apr 6, 2010A.O. Smith CorporationController for a motor and a method of controlling the motor
US7931447Nov 17, 2006Apr 26, 2011Hayward Industries, Inc.Drain safety and pump control device
US7988425Jun 6, 2006Aug 2, 2011Stingl David APump and alarm control
US8133034Feb 7, 2006Mar 13, 2012Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8177519Jul 21, 2009May 15, 2012Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8177520Apr 8, 2005May 15, 2012Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8281425Oct 9, 2012Cohen Joseph DLoad sensor safety vacuum release system
US8282361Jul 21, 2009Oct 9, 2012Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8313306Oct 2, 2009Nov 20, 2012Pentair Water Pool And Spa, Inc.Method of operating a safety vacuum release system
US8353678Jul 21, 2009Jan 15, 2013Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8354809Jan 15, 2013Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8360736Mar 31, 2010Jan 29, 2013Regal Beloit Epc Inc.Controller for a motor and a method of controlling the motor
US8436559Jun 9, 2009May 7, 2013Sta-Rite Industries, LlcSystem and method for motor drive control pad and drive terminals
US8444394May 21, 2013Sta-Rite Industries, LlcPump controller system and method
US8465262Oct 24, 2011Jun 18, 2013Pentair Water Pool And Spa, Inc.Speed control
US8469675Dec 7, 2006Jun 25, 2013Pentair Water Pool And Spa, Inc.Priming protection
US8480373Dec 7, 2006Jul 9, 2013Pentair Water Pool And Spa, Inc.Filter loading
US8500413Mar 29, 2010Aug 6, 2013Pentair Water Pool And Spa, Inc.Pumping system with power optimization
US8540493Dec 8, 2003Sep 24, 2013Sta-Rite Industries, LlcPump control system and method
US8564233Jun 9, 2009Oct 22, 2013Sta-Rite Industries, LlcSafety system and method for pump and motor
US8573952Aug 29, 2011Nov 5, 2013Pentair Water Pool And Spa, Inc.Priming protection
US8602743Jan 13, 2012Dec 10, 2013Pentair Water Pool And Spa, Inc.Method of operating a safety vacuum release system
US8602745Dec 11, 2006Dec 10, 2013Pentair Water Pool And Spa, Inc.Anti-entrapment and anti-dead head function
US8801389Dec 1, 2010Aug 12, 2014Pentair Water Pool And Spa, Inc.Flow control
US8840376Mar 29, 2010Sep 23, 2014Pentair Water Pool And Spa, Inc.Pumping system with power optimization
US9051930May 30, 2013Jun 9, 2015Pentair Water Pool And Spa, Inc.Speed control
US9243413Dec 8, 2011Jan 26, 2016Pentair Water Pool And Spa, Inc.Discharge vacuum relief valve for safety vacuum release system
US9328727Dec 20, 2010May 3, 2016Pentair Water Pool And Spa, Inc.Pump controller system and method
US9371829Oct 30, 2007Jun 21, 2016Pentair Water Pool And Spa, Inc.Pump controller system and method
US9399992Jul 29, 2014Jul 26, 2016Pentair Water Pool And Spa, Inc.Pump controller system and method
US9404500Sep 12, 2011Aug 2, 2016Pentair Water Pool And Spa, Inc.Control algorithm of variable speed pumping system
US20050226731 *Apr 8, 2005Oct 13, 2005A.O. Smith CorporationController for a motor and a method of controlling the motor
US20060127227 *Feb 7, 2006Jun 15, 2006A.O. Smith CorporationController for a motor and a method of controlling the motor
US20080095638 *Oct 13, 2006Apr 24, 2008A.O. Smith CorporationController for a motor and a method of controlling the motor
US20080095640 *Oct 13, 2006Apr 24, 2008A.O. Smith CorporationController for a motor and a method of controlling the motor
US20090290990 *Nov 26, 2009Brian Thomas BraneckyController for a motor and a method of controlling the motor
US20100068073 *Mar 18, 2010A. O. Smith CorporationController for a motor and a method of controlling the motor
US20100080714 *Apr 1, 2010A. O. Smith CorporationController for a motor and a method of controlling the motor
USRE36871 *Mar 9, 1995Sep 12, 2000Abbott LaboratoriesRemotely programmable infusion system
DE1169224B *Feb 17, 1960Apr 30, 1964Karl ZieglerUEberwachungsgeraet zum Feststellen von Gasblasen in einer durch eine Leitung stroemenden, elektrisch leitenden Fluessigkeit
Classifications
U.S. Classification200/83.00Z, 200/83.00R, 200/322, 417/34, 417/43
International ClassificationH01H35/24, H01H35/34
Cooperative ClassificationH01H35/34
European ClassificationH01H35/34