US3234344A

US3234344A - Electromagnetic circuit breaker having a solenoid with a hydraulic time delay means

Info

Publication number: US3234344A
Application number: US252404A
Authority: US
Inventors: Raymond B Heilman
Original assignee: Heinemann Electric Co
Current assignee: Heinemann Electric Co
Priority date: 1963-01-18
Filing date: 1963-01-18
Publication date: 1966-02-08
Anticipated expiration: 1983-02-08

Description

Feb. 8, 1966 R. B. HEILMAN 3,234,344

ELECTROMAGNETIC CIRCUIT BREAKER HAVING A SOLENOID I WITH A HYDRAULIC TIME DELAY MEANS Filed Jan. 18, 1963 4 Sheets-Sheet 2 H9 IO! 93 nh i mll 4 INVENTOR.

RAYMOND B.HEILMF\N 5 QT TOR J Feb. 8, 1966 R. B. HEILMAN 3,234,344

ELECTROMAGNETIC CIRCUIT BREAKER HAVING A SOLENOID WITH A HYDRAULIC TIME DELAY MEANS Filed Jan. 18, 1963 4 Sheets-Sheet 5 WELD SUSPENSON sTRUCTURE. O BROKEN nwr-w HERE AND PQQT'LY OMFFTED FOR CLRQlTY INVENTOR. RAYMOND B. HEILMAM irrpmw R. BIHEILMAN 3,234,344 ELECTROMAGNETIC CIRCUIT BREAKER HAVING A SOLENOID Feb. 8, 1966 WITH A HYDRAULIC TIME DELAY MEANS 4 Sheets-Sheet 4.

Filed Jan. 18, 1963 INVENTOR. BY RAvM'omo B. HEILMHM /415 HTTOQ/UE J United States Patent )flFice 3,234,344 Patented Feb. 8, I966 3,234,344 ELECTROMAGNETIC CIRCUIT BREAKER HAV- ING A SOLENOID WITH A HYDRAULIC TIME DELAY MEANS Raymond B. Heilrnan, Trenton, N.J., 'assignor to Heinemann Electric Company, Trenton, N.J., a corporation of New Jersey Filed Jan. 18, 1963, Ser. No. 252,404 17 Claims. (Cl. 200-97) This invention relates to the electromagnet of a magnetic circuit breaker of the type in which the contacts open after a time delay period for certain overloads and instantaneously at higher overloads and, more particularly, to an improved movable tube of an electromagnetic device for controlling the variation in the time delay period for a given overload as the ambient temperature changes between extreme limits. This invention also relates to an arrangement for automatically resetting the movable tube duringthe opening of the contacts after electromagnetic opening of the contacts either instantaneously or after a time delay.

A fully electromagnetic circuit breaker of the time delay type is illustrated by Wilckens Patent No. 2,360,922, in which a movable magnetic core is housed within a stationary nonmagnetic tube and the core is moved by certain overload currents from one end of the tube toward the other end to increase the strength of the magnetic field and to trip open the circuit breaker contacts after a time delay by actuating a pivotal armature. Movement of the core in such circuit breakers is retarded by a spring and the dash pot action of a silicone oil, both within the tube, the oil during the movement of the core moving from one side of the core to the other in the annular orifice defined by the clearance between the core and the tube. Due to the change in volume and viscosity of the oil as the temperature changes, the time delay period produced by such an arrangement varies somewhat with the temperature of the oil, resulting in the electromagnetic tripping of the circuit breaker after time delay periods which vary, to some degree, for the same overload current as the temperature varies.

While it is true that use of silicone oils has been preferred because, among other reasons, the viscosity of silicone oils changes little with temperature changes, a characteristic which is relatively well known, (Chambers Technical Dictionary, Third Edition, 1958, p. 1013), in some uses it is desirable to compensate for even this small change in viscosity because of the variation in time delay periods which it would otherwise produce, so as to reduce the variation in time delay periods for the same overload current conditions, as the temperature changes greatly, i.e., compensate for temperature changes.

Also, in prior arrangements, an air bubble in the tube housing the magnetic core and the silicone oil has been used to accommodate the volume changes of the oil as the ambient temperature varies. But the air bubble tends to resist being split in its passage from one side of the core to the other, which may impede the core travel in excessof what is desired, or if the air bubble manages somehow to move from one side of the core to the other,

as one unit, the core would be impeded less than usual during such movement, and in either case a variable volume of the space housing the fluid automatically varies in direct response to the pressure exerted by the fluid on the walls enclosing it. The preferred fluid is a liquid in the operating temperature range, and since the volume and the viscosity of a liquid are interrelated, compensation for the varying viscosity is achieved by using the change in fluid volume, and the consequent change in pressure on the walls enclosing it, to move the initial position of the core and also simultaneously change the size of the orifice through which the fluid must flow during movement of the core, to compensate for the fluids ditferent viscosity at the different temperature.

In view of the foregoing, it is, therefore, an object of this invention to provide an improved tube for the electromagnet which automatically provides some compensation for varying ambient temperatures so as to result in a time delay period, at certain overloads, within a predetermined range.

In this invention the tube itself is attracted toward the coil to initiate movement of the mechanism to the conacts open position, at certain overloads after a time delay period and at higher overloads instantaneously, and, hence, another object of this invention is to provide an arrangement which uses a part of the linkage mechanism (during its movement to the contacts open position) to reset the tube to its initial position automatically and simultaneously with opening of the contacts.

In one embodiment of the invention the electromagnet comprises a coil which surrounds, in part, a movable tube formed of nonmagnetic material except for a tube end cap or pole and a movable core within the tube. The interior of the tube is divided into two spaces by a flexible, expansible member or bellows, the movable mag netic core being disposed in one of the spaces in which is also a fluid whose volume and viscosity varies with temperature. The movable core divides the space containing the fluid into two smaller spaces and movement of the core toward the coil (and the tube magnetic cap or pole) is retarded by a spring and the dash pot action of the fluid which passes through orifices'from the underside of the core to the upper side thereof. The expansion and contraction of the fluid, due to the arrangement of the various parts, varies the size of one of the orifices as the temperature varies and also varies the initial position of the core (relative to the coil), to compensate, to some degree, for the changes in temperature of the fluid and the tube so as to control the variation in time delays, as the temperature varies, for a given overload current within the range of currents in which a time delay is desired.

The foregoing and other objects of the invention, and the best mode in which I have contemplated applying such principles will more fully appear from the following description and accompanying drawings in illustration thereof.

In the drawings,

FIG. 1 is a sectional view, partly in elevation, of a circuit breaker embodying the present invention, illustrating the contacts open position;

FIG. 2 is an enlarged sectional View of the movable tube illustrated in FIG. 1, showing the internal details thereof for the contacts open position and the normal temperature;

FIG. 3 is a sectional view taken along the line 3--3 in FIG. 1 but part of the suspension structure for the movable tube has been broken away for illustrative purposes and the mechanism is illustrated in the trip free position;

FIG. 4 is a partial view taken along the line 44 in FIG. 3 but in FIG, 4 some of the suspension structure 3 for the movable tube is illustrated which is not illustrated in FIG. 3;

FIG. 5 is a fragmentary diagrammatic view showing the contacts in the open position and illustrating primarily the movable contact arm engaging the tube reset spring for automatically resetting the movable tube when the contact arrn moves toward the open position; 7

FIG. 6 is an end elevation view taken along the line 6-6 in FIG. 5; and

FIG. 7 is a view similar to FIG. 5 but illustrating the contacts in the closed position and the movable contact arm disengaged from the tube reset spring to allow the tube to move down during electromagnetic tripping.

Referring to the drawings, there is illustrated-a circuit breaker 10, including an outercasell and

terminal structures

12 and 13 extending therefrom. The terminal structure 12 is connected within the case by a conductor 14 to a coil 15 forming part of 'an electromagnet 15 which, on predetermined overload current cond'itions, moves axially a tube 20, thelatter being partly of magnetic material and functioning in the manner of an armature for the solenoid coil 15. The tube. 20 controls 'a linkage mechanism 21 of the circuit breaker for auto matically (on predetermined overload conditions) opening the

contacts

22 and 23 by pivoting the contact22 out of engagement with the stationary contact 23. For opening the contacts, the movable contact 22is carried by a movable contact arm 24 pivoted at the'right on'laterallyprojecting feet 25, the arm'24 being electrically connected by a flexible conductor 19 tothe coil 15. Manual opening and closing of the contacts 22 and .23 is efifectuated by a handle '28, whereas electromagnetic tripping of the contacts to the open position is efiectua'ted by the pivotal movement of a lock 29 (FIG. 4) upon suitable downward movement of the tube 29 and pivoting of-the counterweight suspension structure 30 (FIGS. 3 an The linkage mechanism 2 1;comprises two groups of links referred to for'convenience as the handle toggleor first group 3i and the main toggle or second group 32. The linkage is more fully described and claimed in a copending patent application filed onDecember 24, 1962, by Raymond B. Hellman and Harold H. Bahr, Serial No. 246,699.

Briefly, however, pivotal counterclockwise movement of the handle. 28, starting from the open contacts position of FIG. 1, causes the handle. toggle links 31 comprising the handle link 33 and a link of varying length 34 (joined together by a knee-pintle 42) to move to the right and the handle force to be transmitted ,by a coupling link 35, from the link of varying length 34 to the knee pintle 41 of the main toggle 32, the latter" comprising the

toggle links

37 and 38,;and the catch link 391$ The lower link 38 is, in; turn, connected to the movable contact arm 24, whereby movement of the handle link 33 results in the movable arm 24 being rotated in counterclockwise direction, closingthe

contacts

22 and 23. 'In the closed position of the contacts, thecatchlink 39 is restrained from movementby a lock 44. carried by a cradle 45. In turn, the cradle 45 is restrained by the lock 29 from moving in the counterclockwiseidirection (due to the bias imposed on the cradle 45 by the catch link 39) from the force of the openingfsp'rings 48.

When the tube 20 moves downwardlya sufficient distance, upon predetermined overloads, the tube 20 pivots clockwise (FIGS. 1 and 4) thecounterwe'ight suspension structure 30 sufiiciently to engagethe lock '29 and rotate the latter in the clockwise "direction falso. Suflicient clockwise rotation of the lock 29 results in the release of the cradle 45, whereby they catch link 39 is released and-the'upper end of the catch link 39'moves in the clockwiseidirection under; the bias of the opening springs ls. This'clockwise movement of the catch link 39 causes the toggle formed by

links

37 and 38 to collapse to the left (FIG. 1); due to the pressure of the openin g springs 48, whereupon the contactsopen. 'Dur-' ing the collapse of the main toggle links, the knee pintle 42 of the handle toggle is moved overcenter (toward the left) sulficiently for the spring 51 (carried by the link of varying length 34) to help reset the mechanism.

Referring to FIG. 2, the tube 20 comprises a generally cylindrical case 55 of nonmagnetic material, preferably stainless steel, definingxa shoulder 56, which divides the case 55 into'a lower case part 57 of smaller diameter than the upper case part 58. The lower case part 57 is closed and completely 'sealedby a nose (cap or pole) piece 60, of magnetic material, welded to the. case part 57 and having an axial opening through which extends an elongated pin 62 of nonmagnetic material, also preferably of stainless steel and welded to the lower end of the nose 60 (to completely seal the tube). The upper end of the tube 20 is closed byv acap 63, of non-magnetic material and preferably of stainless steel, and welded to the upper case part 58 and a bellows 65 to seal a space 66;. v

. The interior of the tube 20 is divided by the expansible, flexible member or bellows 65 into the first space 66, completelyv filled ,with' a fluid, and a. second space '67, thebellows being formed of a thin metallic material and preferably from nickeL. The first space 66 comprises an i lower partefi, an intermediate .part 69; (between the shoulder 56 and the lower end ofthebellows 65) and an upper annular part 7tl circumferentially surrounding the space 67. Disposed within the intermediate space 69 and extending into the lower space at all times, asufficientdistance 10 be surrounded in part at all times by the coil 15 and its magnetic-frame 7 0, is a movable core or armature 72 of magnetic material and comprising an elongated annular lower tube 73 and an integral annular upper piston 74. v i e v Z The core 72 moves a iallyrelative to the tubular case 55 of the tube 20, and is guided in such movement by the sliding 'fitbetweenthe annular tube 73 and the inner surface of the tubular case part 57 and the. sliding fit between the pistonjfl and the inner surface of the upper tubular case part 58, the latter two jointly defining an annular orifice 75. The piston 74 carries and has attached in spacedrelation thereto, preferably by spot weld ing, an orifice plate 76 housing a floating annular orifice valve 86, the plate 76 havinga centrally formed orifice 77 and massive 835 an orifice 187 for. jointly with a metering pin 80, controlling the rate of fluid flow between 0pposite sides of the piston 74 during axial, downward movement of'the core 72.

The metering pin 80 for the orifice 87 depends from and is securedto a lower plate 79 secured to and car,- ried by the bellows 65, the orifice plate 76 being biased by a core spring 81 toward the bellows plate 79 at all times. The core spring "81 is seated at its lower end a ainst the magnetic nese 50, extends into the axial opening 820i thecore72, and is seated at the up'pe'r end against a shoulder 83 formed on 'thecore 72, the spring 81 resisting downward movement of the core and returningit to its initial position after electromagnetic tripping. After electromagnetic tripping, the fioatingannular valve 86 provides for the fast return of the fluid into the space69. e r V I The metering pinj80 is concentric with the upper portion of the pin '62, the metering pin 80 being provided with a longitudinal openingsfs into which the pin 62 slid'ably'fits for 'g uiding' the metering pin 8% during movement of the latter. As illustrated, the core spring 8 1is also concentric with the pins 62' and '80 and with the lower portion of the core 72 and "the spring 81 'is inter mediate the Stland, the core 72.

The bellows plate 79 is biased downwardly at all times against thejfluid within the space 66 by 'an axial sprin g88centr'ally positioned within the bellows'65. A threaded hole 90 is provided in the cap '63 to receive a threaded plug 96 which bears against the upper end of the spring "88in thereby adjust, within certain limits, the force exerted downwardly by the spring 88 on the bellows plate 79 and the fluid.

To limit upward travel of the core 72 and properly:

J seal the space 66, the upper end of the case part 58 has an inner surface which defines two annular shoulders 92 and 93 separated by a cylindrical wall 94. A cylindrical sleeve 95, concentric with the upper tubular case part 58, interfits with and abuts, a portion of the inner surface of the case part 58 and has an upper bent rim 97 lying upon the shoulder 92, as illustrated in FIG. 2, the lowermost terminal portion 98 of the sleeve 95 acting as a stop to limit upward movement of the core 72 by abutment therewith of the upper periphery of the orifice plate 76.

The bellows 65 is generally of cylindrical shape with a closed, lower, horizontal end to which the plate 79 is secured and which defines with the length-wise convolutions a cylindrical space of variable volume, as determined by the volume of the fluid within the space 66, the bellows 65 being of one piece construction.

The bellows 65 has an upper, flexible end portion 99 which extend-s upwardly between two hollow (for flexibility), stainless steel rings 101 and 4102, each of one piece construction. The cap 63 is provided with two shoulders 1108 and M9, the vertical surface of shoulder 108 biasing the ring 192 radially outward against the bellows end portion 99, the latter being urged against the ring 101, which is in turn urged against the inside of the uppercase '8. Vertically upward movement of the ring 102 is restrained by the horizontal surface of shoulder 108 and downward movement by the outwardly rolled edge portion .105 which forms an annular lip-like ledge, as illustrated in FIG. 2, below a horizontal plane through the center of the ring 102. The horizontal surface of the shoulder 109 biases another part of the bellows end 99, downwardly against the ring 1111, after the bellows end has been turned at approximately a 90 angle, as illustrated in FIG. 2, while downward movement of the ring 101 is prevented by the rim 97.

The bellows end '99 then extends horizontally beyond the ring 101 and lies between the shoulder 93 and the horizontal surface of shoulder 109, the bellows end 99 being then again turned at 90 angle to extend upwardly between the rim of the cap 63 and the rim of the upper case part 58. An interference fit is provided between the cap 63, the bellows end 99, and the inner rim surface (119 of the upper case part 58 and the cap is pressed into position to preliminarily seal the space 66. The final step in sealing the space 66 is to weld the extremity of bellows end 99 annularly with a bead type weld to the outer periphery of the cap 63 and the upper case part 58, as illustrated.

The coil .15 is formed by a suitable number of turns of wire electrically insulated from each other and wound upon a non-magnetic metal tube 111. The magnetic frame 70 for the coil is provided by an open ended almost completely annular tube, of L-shape in crosssection, except for the slot 114 (FIG. 2). That is, the frame 70 includes an integral top wall with an opening to receive the case part 57 and the frame extends down around the coil 15. The top, horizontal wall of the frame 70 has an annular lip 118, as best illustrated in FIG. 2, which stands up with a thickness approximately the same as that of the piston 74 of the core 72, to aid in completing the magnetic circuit when the tube and core 72 are in their lowermost positions.

The bottom of the coil 15 is closed by a magnetic pole or bushing 115 which also extends within the cylindrical space defined by the nonmagnetic tube 111 about which the coil is wound. The pole 115, FIG. 1, is of L-shape in cro-sssection, ends slightly above the middle of the length of the tube 111, has a slot (not shown) extending axially similarly to slot 11-2, and the pole 1115 closes the bottom of the coil, except for a radial continuation (of the aforementioned slot) through which the flexible conductor v19 extends. The tubular part of the bushing 115, adjacent its juncture with the horizontal part of the bushing 115, FIG. 2, is formed on its outside surface,

6 i.e.', facing the coil, with an annular, undercut, half-moon shaped recess 117. The presence of the bushing with the undercut recess .117 extending into the cylindrical space defined by the tube 111, as described, was found to significantly raise the overload current value at which instantaneous overload tripping took place.

Secured to the pole '115 is a bearing'116 through which extends the lower part of the pin 62 for guiding the tube 20 during movement and for limiting upward movement of the tube 20 by engagement of the reset plate 142 with the bearing 116.

The nose 60 and pin 62 interfit with the pole piece 115,

as illustrated, to define an air gap Z of variable size dependent on the axial position of the tube 20 and an annular space between the nose 60 and the pole piece 115 of constant radial size regardless of the axial position of the tube. Similarly, the piston 74 (of the core 72) over: :lies the top surface of the frame 70 to define an air gap between the latter and the lower surface of the piston 74 of varying size dependent on the axial position of the tube 20 and an annular space between the tube 73 and the coil 15 of constant radial size regardles of the axial position of the tube 20.

The counterweight suspension structure '30 (FIGS. 3 and 4) is formed by spaced plates and 121 which are pivoted intermediate their ends on pintles 122 (FIG. 4) secured to arms 1123, the latter being welded at their right hand ends to the frame plates .124 of the mechanism. The spaced

plates

120 and 121 are also pivotally connected by pintles 126 to the tube 20, the pintles 126 being secured to the right of pintles 122 and to the tube 20 by a strap which frictionally and tightly engages the outer surface of the tube 20 and is carried thereby. Springs 128 are provided to bias the pintles 126 above or below the pintles r122, the springs .128 having their right hand ends connected to the

counterweight plates

120 and 121 between pintles 123 and .126. The counterweight structure 30 is further described and claimed in a separate patent application filed January 18, 1963, by Ronald Nicol, Serial No. 252,413.

As illustrated in FIGS. 1 and 5 to 7, coiled about a pin 14!) (secured to the spaced frame plates 124) is a reset torsion spring 141 for the tube 20. The reset spring 141 has one end secured to-a reset plate 142 which is in turn secured to the lower end of pin 62 of the tube 20. The other end of the reset spring 141 is disposed to the left of an extension 1 43, the latter being secured to the right hand portion of the arm 24, FIGS. 5 and 7, and having a lateral portion 144. The extension 143 and the associated end of the reset spring 14 1 are arranged relative to each other so that in the closed position of the contacts, FIG. 7, the lateral portion 144 is spaced from the near end of reset spring 141, the spring 141 being relaxed at this time and applies no bias to the tube 20. When the mechanism moves from the contacts closed to the contacts open position, whether by manual movement of the handle 28 or electrom'agnetica-lly by release of the cradle 45 (by the pivotal lock 29), the lateral portion 144 engages the associated end of the spring 141 and depresses it, causing the other end of the reset spring 141 to exert a force upwardly upon the pin 62 of the tube (20 which is suflicient, upon denergization of the coil 15 (that is, extinction of any are that may form) to reset the tube 20 by moving it upwardly sufiiciently for the pintles 126 (of the counterweight structure 30) to move above the center of pintles 122, at which time the suspension springs 128 also help to move the tube 20 up to its reset or open contacts position.

When the mechanism is in the contacts open position, as illustrated in FIG. 1, manual closing of the contacts is accomplished by manually moving the handle 28 counterclockwise about the pintle 152 of the handle link 33. This movement of the handle 28 forces the handle toggle knee pintle 42 to move the sliding link down against the upward of the handle toggle spring '51 (the latter being carried-by the L-shaped link 1'54 which pivots about pin'tle1153) and further compresses the IspiringSL'moving thepin'tlef42 from theleft of a centerj lineconnecting the pintles ,152 and .153, towardthe rig t hereer; TheL shaped'link 'is also connected to link "33 byfloating link 148 through I

pintles

42 and 155 and the L-shaped link 154 carries'the pintle1155 about .thefpint1e1 j3 in a manner to maintain the 'floating'link :148 and thec'oupling link 35 in force transmitting relation and 'the'L-shaped link 154 performs this-same function during, electromagnetic tripping, Continued counterclockwise movement of the handle 28 causestheknee pintle 4Q. tornove through the center line between the "pintles 1'52 and 1'53 and to the right hand side'thereof, the line of action'of the handle toggle spring" 511 now moving-from theletttothe right o tthe line between'pintles 152*and '153, whereby the toggle spring il'now movesjthe handle toggle links to the rightfwith a snapact-io'n, until the handle link 33 abuts against the rightst op pin.15=7, FIG. 'l,thehandle toggle spring'51 remaining jmorecompre'ssed when the handle'link as abuts theright 'stop in 157 than when it abuts theleftsto'p pin lSS. v V

When the linkage is turned to thefclosed pbsitionfof the contacts, thetogglelinks37 and 38Lgo"overcenter to the right and thespring'force"of'the' opning springs 48 tend to rotate the catch link '39 clockwise, but rotation of the catch link is restrained'by thelock lip 44 carried by the cradle'45. I t I Atpredetermined'ciirrent conditionsfabove a current level at which insta'ntaneous'tripping of the circuit breaker is desired the electromagnetic flux is sufficient about the magnetic nose 6t) andma'gneticc'orefl to create a pull on the tube 20 whichmovesit sutficiently downwardly, to pivot the "counterweight structure 30 v and the lock 29 (including'the lattersfinturnedl1atcl1'160, ElG. 3) out of engagemenfiwith the, upper end of. the cradle 45 at'which'tim'e the catch .link.39'isfreleased by the lock lip 44. The toggle -for'rned by links '37 and 38 now collapsesto'the'left' and the movable 'a'rmf24moves to its contacts open. position under the bias'o fthe openingispri'ngs' 48. and a contact fo'rce spring 162, FIG. 1. Upon the occurrence "of ove'rlo'ad'currents above a certain percentage in excess of the 1 rated load but below the aforementioned higher, instantaneous trip current value, the'tube '20 provides time"delays'between 'the occurrence ofjthe'overlo'ad 'current'andj the opening of the contacts, These time delays varyi'for the Shine overload current value depending ion thetemperature'oftheitube 20 but the variation due to temperature changes is rereduced, i.e., "compensated, by the arrangement of the tube20.

That is, when thejcoilflS is energized, a' magnetic field is establihejdin themag netic frame 70am about the :ma'gneticfnose 6 0 and the j'rnagnetic movable core 72. The-magnetic field'is insufficient, 'at'rated'loajd condi- 20 againstthe upward fo'rcepla'ced'on'theltubeZO- by the counterweight "structure "30 or to move the core toward thecoil1'5fagainst the retarding springfil'and' fluid within space '65. However, upon the occurrence of overload-currents above a certainpercentage inexeess of the rated current but below the aforementioned'higher, in-

s'tant'a'neous trip current, this magnetic field does sufficiently attract the armature 7 2 to' start movementf thereoftowardthe coil 15,, against the'bias ofth'e core spring 81 and'the'dampingetfect of'the fluid within the space 66 'such time against plate 76. As the magnetic: core 72 moves downwardly toward the coil, the magnetic force ,on'the core 72 and'on the magnetic nose idilincreases,

due to thefactthat the reluctanceof the circuit'is being lowered, since the equal gaps, indicated as X and Win FIG. 2, arebeing decreased. When the core movesdownwardly sufliciently, that is, as the piston 74 approaches or contacts the shoulder 56 and the lower end of the core tube extension 73 approaches or contacts the nose '69, the magnetic force on the magnetic nose 60 becomes great enough to overcome the upward force of the counterweight structure 36 and the magnetic force now moves the entire tube 20 through the equal gap distances, indicated as Y and Z, in FIG. 2, between the shoulder 56 and the top of the magnetic frame 70, and between the nos'e'dtl and the lower pole 115. This movement of the tube 20 carries with it the arm 165 of the counterweight structure 30 which strikes the pivotal lock 29 to pivot-the latter sufficiently to release the cradle 4-5 and there'byrelease the catch link 39, whereby the main toggle links 37 and 38 collapse to move the arm 24 to the open contacts position. v v

When'the counterweight structure 30 so'rnoves, once the pintle 126 of the counterweight'structure passes below the horizontaljplane through the center of pintles 122, the spring 128 of the counterweight structure 30 also helps to move the time delay tube device 2t) downwardly with a snap action, since the spring 128 now biases the pintle126 downwardly also.

' The closer the current values approach the instantaneous'trip value, the faster will the core 72 'move toward the coil 15, because the strength of the magnetic field is then'greater and this will in turn increase the magnetic 'fieldso as to achieve a force on the magnetic nose 60 which is sutficient to move the tube 2t) downwardly-without the need for the movable core to move through any or all of the entire gap distances, labeled X and Win FIG. 2. Thus, an inverse time delay results, that is, long time delays at smaller overloads and shorter time delays at largeroverloads. Upon the occurrence of short circuits or extremely 'high'o'verloads above the instantaneous trip current value, the tube 20 moves downwardly without any movement of the core 72. That is, the current at such times creates a sufficiently high magnetic pull on the magnetic nose 60 to, with the aid of the force on the fluid due to the pullon the magnetic core 72, instantaneously move the tube 2.6 downwardly for instantaneously tripping open the circuit breaker.

The movable core 72, the fluid completely filling the space66, and'the bellows '65 are arranged so that the piston 74 is at the predetermined distance X above the shoulder 56 at the normal ambient temperature of 75 F .,'this dimension being checked after assembly of the tube 20 by X-rays (but before welding together the cap 63, the case rim 119, and the bellows end 99). If necessary'the tube is disassembled and refilled to insure'that 'the amount of fluid, and, hence, the volume of the space 66, is the amount required to result in the predetermined distance X, within the tolerancedesired.

When the ambient tem perature varies from 75 F., the volume of the fluid within the space fiechanges and the viscosity of the fluid also changes. I

The metering pin has an outside surface to-cornpensate'for theternperature changes, the pin outside surface comprising three stepped tapers and a cylindrical portion at the lower end, of a diameter larger than any of the tapered surfaces, the smallest tapered diameter being at theend of thepin 80 attached to the'bellows 65 and the largest diameter at the opposite end, as illustrated 'in FIG. 2. Upward movement of the core 72 is stopped by the lower end 98 of the aluminum slecve' at a predetermined temperature but it should be noted that at temperatures above, this predetermined temperature the -bellows may continue to contract, to a position deter- "mined by'the springs 88 and 170, moving the pin 80 upwardly, even though further movement of the core 72 is prevented. Contraction of the bellows 65 is at all times initially resisted by the spring 88, but to further resist the upward force on the bellows 65 (exerted by the fluid) the second spring 170 is placed within the first spring 88 (seated upon the bottom of the bellows and engageable with the plug 96), the second spring 170 being of shorter axiallength than the first spring and coming into action only after the bellows 65 has contracted an amount equal to the difference between the length of the two

springs

88 and 170.

Thus, assuming the existence of the normal temperature of 75 F. and an overload current in the range to produce a time delay before the opening of the contacts, the movable core 72 will move downwardly and the fluid will flow upwardly through the

orifices

75 and 87. The orifice 75 is of fixed size but the orifice 87 varies in size as the core 72 moves becoming smaller as the core 72 moves down until the piston 74 abuts the shoulder 56 after it has travelled through the distance X, FIG. 2.

But when the temperature of the fluid increases above the, normal temperature, the volume of the fluid increases and its viscosity decreases, contracting bellows 65, and the metering pin 80 and the core 72 move upward. Upon an overload current within the time delay range suflicient to initiate downward movement of the core 72, the fluid flows upwardly through the

orifices

75 and 87. The orifice 87 is of the same size, initially as during the position ofthe core 72 for the 75 F. normal temperature up tothe aforementioned higher predetermined temperature but above this predetermined temperature the orifice 87 is smaller, due to the fact that upward movement of the core 72 has stopped but not that of the pin 80. At temperatures above 75 F., when the core 72 has moved through a distance equal to the distance X for the normal 75 F. temperature, the size of the opening between the orifice 87 and the pin 80 decreases from the size existing at the end of travel of the core 72 at the normal temperature. Such reduction in size jointly with the longer distance through which the core 72 must travel at the increased temperature, compensates for the decreased viscosity to provide a time delay, at temperatures above the normal temperature, which approximates the time delay period at the normal temperature for a given overload, in the range of overload values where a time delay is desired.

When the ambient temperature decreases from a temperature above 75 F. to the normal 75 value, the fluid in the space 66 and the force of the

springs

88 and 170 return the metering pin 80, the bellows 65, and the movable core 72 to the normal 75 F. position, as illustrated in FIG. 2.

If the ambient temperature drops below 75 F., the

fluid decreases in volume and increases in viscosity and the core 72 moves (at the decreased temperature) relative to the metering pin 80 less than at the normal 75 F. temperature because contraction of the fluid causes the bellows 65 to elongate and moves the core 72 down (against the force of spring 31) to an initial position closer to the nose 60 than the normal position of the core 72 at the normal temperature. Also, elongation of the bellows 65 under pressure of spring 88, as the fluid contracts, results in lowering of the pin 80 so that a smaller outside surface diameter defines with the valve 86 a larger orifice 87 during the end of the down ward travel of the core 72 so that ultimately a larger orifice 87 exists (after-the core 72 moves its full amount) than exists "at the end of core travel at the normal temperature, thus compensating for the increased viscosity .of the fluid at lower temperature.

normal, a larger orifice 87 resultsbetween the metering pin 80 and the valve 86 (relative to the opening at the normal temperature) for the fluid to flow through, because the lower temperature contracts the fluid causing the bellows to expand, thereby lowering the pin and the core 72, this larger opening resulting at the time movement of the core 72 ends during a time delay period. Similarly, when the fluid temperature increases from normal, at the end of core travel, a smaller orifice 87 will result between the pin 80 and the valve 86 because the higher temperature expands the fluid (against the springs within the bellows) raising the pin 80 and the core 72.

Thus, it is seen that when the fluid temperature decreases and its viscosity increases, since the orifice 87 is larger and the travel of core 72 toward nose 60 is less, time delay compensation has been made for the increased fluid viscosity for overloads in the time delay range. Similarly when the fluid temperature increases and its viscosity decreases, since orifice 87 is now smaller and the travel of core 72 toward the nose 60 is longer, time delay compensation has been made for the decreased fluid viscosity for overloads in the time delay range.

The method used to exclude all of the air from the space 66 when filling it with silicone oil is described hereinafter. Initially the various parts are preconditioned by immersing them in a beaker containing silicone oil and heating them for about one hour at about 400 F., in an assembly chamber by heat from the electrical heating coil of the assembly fixture to be used subsequently in the assembly of the tube. Thereafter, the air is evacuated by the use of suitable pumps from the assembly chamber.

The pumping continues until bubbling activity from the assembly chamber subs-ides to a low rate at which time the assembly chamber is returned gradually to atmospheric pressure and room temperature. Subsequently the assembly chamber is again evacuated and this process is repeated until no bubbles are observed at temperatures of about 400 F. Allof the moisture and some of the absorbed gases in the silicone oil and metal parts are removed by this alternating procedure of heating and pumping.

The first step is to immerse the case 55 completely in a suitable quantity of silicone oil contained in an assembly fixture (not illustrated) which is placed within the assembly chamber. The core spring 81, the core 72 including its valve 87 and plate 76, the sleeve 95, the ring 101, and the bellows 65 are then submerged in the sillcone oil, in almost the desired final axial position relative to the case 55, and aligned, at such time, by a guide sleeve wall forming part of the assembly fixture. At this time some of the silicone oil is displaced into the reservoir forming part of the assembly fixture. (The guide sleeve wall is concentric with the case 55 and forms an axial continuation of the cylindrical wall 94.) This placement of the parts in the case 55 is accomplished within the assembly chamber at a vacuum pressure of about 2 millimeters (mm.) of mercury and at a temperature of about 400 F. produced by the electrical heating coil forming part of the assembly fixture. During this operation the space 67 (enclosed by the bellows 65) becomes filled with silicone oil also.

The second step is commenced at a temperature of about 400 F. and a vacuum pressure of 2 mm. of mercury or less. When a satisfactory level of evacuation. is achieved, evidenced by only an occasional small bubble, the temperature is reduced to about 300 F. With the space 66 sealed jointly by the bellows end 99, the ring 101, the guide wall and a positioning sleeve having a circular surface for holding firmly the bellows end 99 against the upper surface of the ring 101, air at atmospheric pressure is allowed to return at a slow rate into the assembly chamber. Entrance of such atmospheric air tends to further insure that the bellows 65 will be firmly seated against the silicone oil in the space 66 with no air bubble between the two. Thereafter, the assembly chamber is returned to a vacuum pressure of 2 mm. or less and the temperature is stabilized at about 300 F. At such time the ring 101, the sleeve 95, the core 72 and the bellows 65 are jointly moved downwardly by a press which forcefully moves'downwardly and positions the sleeve rim 97 '(of sleeve '95,.) against the shoulder 92, i.e., the final desired position illustrated in FIG, 2. During such movement to the final position, some of the silicone oil between the bellows '65 and the case 55 is displaced through a small port in the guide sleeve into the reservoir, further insuring the complete filling of the space d6. Also, a plunger is placed within the bellows 6'5 to resist the tendency of the bellows to compress, while it is moved downwardly against the silicone oil;

The bellows 65 is made so that at the temperature of 300 F, the bellows is neither extended nor compressed bythe siliconeoilwithinthe space66. This neutral position was selected for the filling of the space "66 to avoid the use 'of devices to extend or contract the bellows to correspond to its length at some other temperature.

The third step is commenced with the fixture and the tube at about 300 F., the assembly-chamber being gradually brought to atmospheric pressure and the guide sleeve and positioning sleeve are thereafter removed. The 'fluid which has entered the "space 67 is also removed at this timefa'nd the

springs

88 and 170, the ring sea, the cap 63 and the plug% are placed in approximately the correct axial position. The assembly chamber is then reclosed and brought to a temperature of about 125 F. and a vacuum pressure of about 10 mm. of mercury. The cap 63 and the ring 102 are then forcefully driven by the press until the ring 102 is just past the center of the ringf101, to the position illustrated in FIG. 2.

Simultaneously, the cap 63 is pressed into position against the bellows end 99 and Within the rim 119 to jointly seal the space '65 due to the interference fit therebetween. Thereafter, the tube 2t) is removed from the assembly chamber and the weld about the cap 63, the

'bellows end 99 and the rim 119 is madeto'permanently insure the sealfor the space 66. t

4 Thus, no air is allowed into the space 66 which could accomrn'ddateexpansion and contraction of the silicone oil and "all such expansion and contraction is reflected in afchangedlength of the bellows 65.

Hence, a tube has been provided in which only the core and the nose are of magnetic material, the rernainde r being -of non-magnetic materials, functioning in "the nature of an armature 'for the coil and providing instantaneous tripping at certain overloads and timedelay tripping at other overloads. Further, the positions of thecore and the metering pin change, as the temperature changes, so that the time delay will approach the time delay at the normal temperature for the same current value. I p

Also, a small quantity of the same kind of silicone oil as is placed in the space 66 maybe placed in the space '57 so that when the temperature increases sufiiciently to vaporize thesilicone oil in the space 67 the downward force on the bellows 65 is sufiiciently in excess of the upward "forceon the bellows -65 to maintain the latter in contact with the silicone oil in the space '66, miniinizing the "tendency or the silicone oil within the space 156 to vaporze and maintaining any vaporization of it toja minimum. Further, to create such a vapor force within thespace 67, the threaded connection between the plug 96 and the cap :63 is hermetically sealed, such as, referring to FIG. 2, by circuniferentially brazing the joint between the plug and the cap at the junction of the upper horizontal surface of the cap 63 and the threaded portion of-th'e'plug 96.

axially extending portion extending less than half way within the tube of nonmagnetic material, a second tube movable from a first position to a second position upon predetermined overload current conditions, said second tube being surrounded partially by said first tube and said coil, said second tube including a forward end cap of magnetic material surrounded at least in part at all times by said first tube and coil, a bearing secured to said frame for positioning said second tube relative to said frame and coil, a bellows within said second tube for dividing said tube into first and second spaces, a fluid of varying voiume as the temperature changes within said first space, a movable core of magnetic material within said first space, a spring for biasing said movable core against said bellows, said movable core being partly surrounded by said frame and coil and partly outside of said frame and coil, said movable core being movable from a first positionspaced from said frame to a second position closer to said frame against the bias of said spring, whereby upon a changein temperature, the volume of said first space changes and the position' o f said movable core changes also due to its being biased against said bellows, whereupon subsequent predetermined overload current conditions the electromagnetic flux causes said movable core to move through a distance that is variable depending on the temperature.

t 2. The structure recited in claim 1 wherein said fluid also varies in viscosity as the temperature varies, said movable core forms an orifice for the flow of fluid therethrough upon movement of said core by theelectromagneti'c flux, said movable core divides said first space into two portions between which said fluid flows through said orifice, a pin carried by said bellows and within said orifice, said pin having an outer surface of 'varyingshape to variably restrict said orifice, the position of said pin relative to said orifice being dependent on the volumeof said first space, whereby the pin compensates 'for changes in viscosity of the fluid by variably restricting the orifice. 3. In a circuit breaker having a linkage controlling separable contacts, an electromagnet for providing an inverse time delay period relative to the magnitude of the overload current for overloads above a first predetermined current and below a second predetermined current comprising the combination or a tube movable from a first position to a second position by electromagne'tic flux, movement of said tube toward said second position initiating separation of said contacts, a coil, said tube being surrounded in part by said coil, said tube comprising a flexible member separating the interior of the tube into first and second spaces, the first space being filled with a fluid which varies in volume and viscosity dependent upon the temperature, a movable core of magnetic material within saidfi'rst space, a spring withinthe second space biasing said flexible member against the mass of fluid in said first space, a second spring for biasing said movable core into engagement with said flexible member, said movable core subdividing said first space into a first portion and a second portion,saicl movable core having an orifice for placing said first and second space portions in communication Witheach other, and said flexible member carrying a metering pin extending into said orifice, whereby at predetermined overload currents after suflicient movement of said tube during a time delay period from said first position toward said second position separation of said contacts is initiated by the linkage of the circuit breaker, the aforesaid structure controlling the variation in the time delay period as the temperature of thefluid changes.

4.1m a circuit breaker, the combination comprising an electromagnet including a coil, a hollowtube of nonmagnetic material movable from a first position to a second position, said coil surrounding and'slidably receiving a portion of said tube, the portion of said tube surrounded by said coil including an end cap of magnetic material, an expansible member within said "tube dividing the interior of the tube into a first space and a second space, a movable core of magnetic material within said first space, said first space containing a liquid whose volume and viscosity varies with temperature, said movable core being operatively connected to said expansi-ble member for controlling the axial position of said core relative to said coil as the temperature varies, said core being spaced from said end cap of said tube to form a gap andmovable toward said end cap upon predetermined current conditions by the electromagnetic flux of the coil, whereupon suflicient movement of said core .and reduction of the gap, the magnetomotive force on the end'cap increases suific'iently to move the tube toward its second position; 5. In a circuit breaker having a pair of separable comtacts, an electromagnet for providing an inverse time delayrelativeto the magnitude of the overload current including a'coil mounted upon a tube of nonmagnetic materiaL-a. magnetic frame for said coil and a second tube movable from a first position to a second position upon predetermined overload to open said contacts, the improvement in said second tube comprising a bellows dividing said second tube into first and second spaces, a fluid in said first space of varying volume and viscosity as the temperature of the second tube changes, a movable armature core of magnetic material in said first space, said first space being completely filled with fluid to substantially exclude all air, said second space being defined by the volume enclosed by said bellows, said movable core being biased against said bellows so that as the volume of the fluid in the first space changes, the volume of the bellows changes and the position of the core relative to the coil and the magnetic field produced by the latter changes, said core including an orifice for the flow of fluid therethrough and from one side to the other of said core when said core is attracted toward said coil to provide a retarding dash pot action, a metering pin carried by said bellows, associated with said orifice, and variably positioned relative thereto thereby, upon temperature changes, to vary the size of the orifice, to decrease the orifice size upon increases in temperature of the second tube and to increase the orifice size upon decreases in temperature of the second tube.

6. The structure recited in claim wherein said second tube has a portion of magnetic material in the magnetic field of said coil, and said metering pin has an annular surface shape of varying diameter along its length, the end of said metering pin of smallest outside diameter being operatively connected to said bellows and the end of said metering pin of largest outside diameter being at the end of said pin toward which said core moves when attracted by the magnetic field of said coil.

7. In a circuit breaker having a pair of separable contacts, an electromagnetic device for providing an inverse time delay relative to the magnitude of the overload currents, said electromagnetic device including a coil energized by said overload currents, and a tube movable toward said coil to electromagnetically initiate separation of the contacts, the improvement in said tube comprising an expansible member within said tube forming with a part thereof a space of variable volume, a liquid within said space completely filling said space, a magnetic movable core within said space, a spring biasing said magnetic core to one end of said space, said magnetic core defining an orifice, a metering pin for variably restricting said orifice and controlled by said expansible member in response to changes in volume of said liquid to increase the orifice restriction as the liquid expands and decreases the orifice restriction as it contracts.

8. The structure recited in claim 7 wherein said magnetic core is biased against said expansible member, said core being disposed between said coil and said expansible member so that as the liquid expands the magnetic core is moved away from the coil and as the liquid contracts the magnetic core is moved closer to the coil.

9. The structure recited in claim 8 wherein said tube is formed in part of magnetic material between the core and the coil.

10. In a circuit breaker having a pair of separable contacts, an electromagnetic device for providing an inverse time delay relative to the magnitude of the overload currents in a predetermined range of overload currents, said electromagnetic device including a coil energized by said overload currents and a tube movable toward said coil to electromagnetically initiate separation of contacts, the improvement in said tube comprising expansible and contractable wall structure forming a space of variable size, a liquid substantially filling said space and excluding sufficient air therefrom so as to prevent the presence of an air bubble which would tend to accommodate the changes in volume of the liquid, a movable core of magnetic material also within said space and attractable toward said coil during said predetermined range of overload current values, said liquid retarding the movement of said core at such times, whereby as the volume of said liquid varies as the temperature varies, said wall structure automatically defines a space of different size, and movement of the core is retarded only by the liquid and is not affected by an air bubble.

11. The structure recited in claim 10 and further including a variably restricted orifice carried by said core, the restriction of said orifice being controlled by said wall structure in response to the volume changes of said liquid.

12. The structure recited in claim 11 wherein the core is biased toward the portion of the wall structure at the end of the space away from the coil, said space being expansible in the direction away from said coil and contractable in the direction toward said coil, so that as the liquid expands the core is moved away from the coil and as the liquid contracts the core is moved closer to the coil.

13. The structure recited in claim 12 wherein the tube is formed in part of magnetic material between the core and the coil.

14. In a circuit breaker, the combination comprising an electromagnet including a coil, a hollow tube of nonmagnetizable material movable from a first position to a second position relative to said coil, said coil surrounding said tube in part, the part of said tube surrounded by said coil including a magnetizable pole piece, a movable core of magnetizable material within said tube, a spring biasing said core away from said pole piece, a fluid within said tube for retarding movement of said core, said tube being movable toward said pole piece upon predetermined overload currents to decrease the magnetic reluctance of the magnetic circuit established by said coil about said pole piece and core and thereby increase the magnetic pull on the pole piece of said tube sufiiciently to move said tube from said first to said second tube position after a time delay, the magnetic pull on said pole piece at higher, predetermined overload currents being sufficient to instantaneously move the tube from the first to the second tube position.

15. In a circuit breaker, an electromagnetic comprising the combination of a coil, a frame of magnetic material for said coil, a cylindrical space defined by said coil, a tube partially extending into said space and movable from a first to a second position, said frame including a magnetizable bushing extending into said space on the side opposite said tube, said bushing having an undercut annular surface facing said coil, said tube including a pole piece of magnetic material in interfitting relation with said bushing but spaced therefrom to establish an air gap of variable size axially and an annular space of constant radial size but variable in axial position, a movable core of magnetizable material within said tube, said core being partially disposed in the cylindrical space defined by said coil and partially outside thereof and overlapping a portion of said frame to establish with said frameia second air gapof variable size and with said'tube pole piecea third air gap of-variable sizeand'a second annular space of constant radial size but of variable axial position;

16. In a circuit breaker, an electromagnet comprising acoil defining-a cylindrical space, a tube'partially extending-into said-space and movable from a first position to a second posit-ion, a'flexible member dividing the tube interior;- into-two spaces, oneoi said spaces being filled with a fluid that varies in volume and viscosity as its temperature changes, a movable core of'magnetic material in the.space 'filled withthe-fluid and-attractable by the magnetic: field of said-:coil, said coreincluding an orifice for the: flow therethrough ofsaid fluid upon movement of the core; and a metering pin variably positionable by the flexible member as the flexible member expands and contracts in response :to the change invoiu-me of the fluid, said :pin cooperating with said orificeto restrict the orifice as' thetemperature of the' fluid increases and to enlarge the orifice asthetemperature decreases, saidv core. being movable by themagnetic field of the coil between a first and a second position, and movement of. the-core toward saidsecond position during predetermined over:

load currents thereafter movingflhe tubeaft ir. ll? dl'ty- References .Citedhyzthe Examiner UNITED; STATES" PATENTS B-ERNARD A. GILHEANY; Primary- Examiner.

ROBERT K. SCH'AEFER, Examiner.

Claims

1. IN A CIRCUIT BREAKER, AN ELECTROMAGNET FOR PROVIDING AN INVERSE TIME DELAY RELATIVE TO THE MAGNITUDE OF THE OVERLOAD CURRENT COMPRISING THE COMBINATION OF A TUBE OF NONMAGNETIC MATERIAL, A COIL MOUNTED UPON SAID TUBE, A TUBULAR FRAME OF MAGNETIC MATERIAL CIRCUMFERENTIALLY PARTIALLY SURROUNDING SAID COIL, SAID FRAME EXTENDING AXIALLY THE LENGTH OF SAID COIL AND INCLUDING END COVERS OVERLYING THE ENDS OF SAID COIL AND AN INTERNAL AXIALLY EXTENDING PORTION EXTENDING LESS THAN HALF WAY WITHIN THE TUBE OF NONMAGNETIC MATERIAL, A SECOND TUBE MOVABLE FROM A FIRST POSITION TO A SECOND POSITION UPON PREDETERMINED OVERLOAD CURRENT CONDITIONS, SAID SECOND TUBE BEING SURROUNDED PARTIALLY BY SAID FIRST TUBE AND SAID COIL, SAID SECOND TUBE INCLUDING A FORWARD END CAP OF MAGNETIC MATERIAL SURROUNDED AT LEAST IN PART AT ALL TIMES BY SAID FIRST TUBE AND COIL, A BEARING SECURED TO SAID FRAME FOR POSITIONING SAID SECOND TUBE RELATIVE TO SAID FRAME AND COIL, A BELLOWS WITHIN SAID SECOND TUBE FOR DIVIDING SAID TUBE INTO SAID FIRST AND SECOND SPACES, A FLUID OF VARYING VOLUME AS THE TEMPERATURE CHANGES WITHIN SAID FIRST SPACE, A MOVABLE CORE OF MAGNETIC MATERIAL WITHIN SAID FIRST SPACE, A SPRING FOR BIASING SAID MOVABLE CORE AGAINST SAID BELLOWS, SAID MOVABLE CORE BEING PARTLY SURROUNDED BY SAID FRAME AND COIL AND PARTLY OUTSIDE OF SAID FRAME AND COIL, SAID MOVABLE CORE BEING MOVABLE FROM A FIRST POSITION SPACED FROM SAID FRAME TO A SECOND POSITION CLOSER TO SAID FRAME AGAINST THE BIAS OF SAID SPRING, WHEREBY UPON A CHANGE IN TEMPERATURE, THE VOLUME OF SAID FIRST SPACE CHANGES AND THE POSITION OF SAID MOVABLE CORE CHANGES ALSO DUE TO ITS BEING BIASED AGAINST SAID BELLOWS, WHEREUPON SUBSEQUENT PREDETERMINED OVERLOAD CURRENT CONDITIONS THE ELECTROMAGNETIC FLUX CAUSES SAID MOVABLE CORE TO MOVE THROUGH A DISTANCE THAT IS VARIABLE DEPENDING ON THE TEMPERATURE.