US 3900810 A
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Description (OCR text may contain errors)
United States Patent 1 [111 3,900,810
Grenier Aug. 19, 1975 TIME DELAY CAPSULE FOR MAGNETIC Primary ExaminerHarold Broome CIRCUIT BREAKER Aime J. Grenier, N. Attleboro, Mass.
Assignee: Texas Instruments Incorporated,
Filed: June 26, 1974 Appl. No.: 483,466
References Cited UNITED STATES PATENTS 9/1954 Wilckens 335/174 2/1971 Bakes 335/174 Attorney, Agent, or FirmJames P. McAndrews; John A. Haug; Russell E. Baumann  ABSTRACT A time delay capsule has a tubular housing to be mounted within a coil in a magnetic relay or the like and has a core which is movable in the housing when the coil is energized for increasing the magnetic field established by the coil to the level necessary for actuating the relay. A spring normally biases the core to one end of the housing and a liquid in the housing retards core movement in response to coil energization, thereby to provide a time delay after coil energization before actuation of the relay occurs. The core and spring are arranged with respect to means sealing the liquid within the housing to permit easy capsule assembly and to assure precise and reliably predetermined core movement within the capsule.
6 Claims, 3 Drawing Figures PATENTED AUG 1 9 I975 TIME DELAY CAPSULE FOR MAGNETIC CIRCUIT BREAKER BACKGROUND AND SUMMARY OF THE INVENTION In a conventional time delay capsule for a magnetic relay, a tube is closed at one end and has a flange at the other end. A magnetic core having a central stem is inserted in the tube with a coil spring disposed around the core stem to keep the core biased against the bottom closed end of the tube and the tube is filled with a predetermined amount of silicon oil for retarding movement of the magnetic core in the tube. Finally, a top cap is brazed to the open, flanged end of the tube for sealing the tube. The high temperature reached during such a brazing operation often results in an annealing of the first few turns of the spring which rests against the top cap during the brazing. Such annealing of spring turns frequently results in a reduction in the level of the bias force on the core and causes a subsequent lowering of the relay coil current threshold which is effective to cause core movement in the capsule. Since the annealing of the spring caused by the brazing is not consistent, allowance cannot be made for the annealing by using a spring of higher force than needed and thereby allowing for the annealing effect. Accordingly, the conventional time delay capsules frequently employ very high annealing point springs such as inconel springs even though springs are more costly and more difficult to manufacture. Further, in the con ventional delay capsules, the top turns of the spring are sometimes inadvertently caught between the top cap and the tube flange during the brazing operation. This results in the distortion of the spring within the tube and hinders the core from attaining its required full travel in the tube, thereby leading to faulty relay operation. Similarly, the spring tends to be jammed between the core and the side wall of the tube. Such jamming also tends to prevent the core from attaining its desired full travel in the capsule. Further, individual convolutions of the coil do not always coil up neatly during compressing of the spring by core movement in the capsule and this also causes inconsistent travel of the core up the tube. Finally, the brazing operation often causes splatter of brazing material into the tube to obstruct the travel of the core within the tube.
It is an object of the present invention to provide a novel and improved time delay capsule; to provide a time delay capsule in which both the rate and extent of core movement is precisely predetermined; to provide a time delay capsule which is of economical construction; and to provide a time delay capsule which is adapted to be easily and accurately assembled.
Other objects and advantages of the novel and improved time delay capsule of this invention will be exemplified in the structures hereinafter described.
In the accompanying drawings in which several of the various possible embodiments of the invention are illustrated:
FIG. 1 is the preferred embodiment of this invention showing a cross section of a time delay capsule for a magnetic circuit breaker;
FIG. 2 is a second embodiment of this invention showing a cross section of a time delay capsule for a magnetic circuit breaker; and
FIG. 3 is a third embodiment of this invention showing a cross section of the time delay capsule for a magnetic circuit breaker.
Referring now to the drawings, the time delay capsule of the magnetic circuit breaker is shown generally as 10 in FIG. 1. The time delay capsule 10 is made up of a closed ended tube 12 with straight side walls which flare out to form a flange portion 14 at the open end of the tube 12. This tube is preferably made out of nonmagnetic materials such as brass. Inside the tube 12 a liquid such as a silicone oil 18 of preselected viscosity and quantity is inserted. A core 20 having an outer diameter fitting snugly within the tube while permitting easy sliding movement of the core in the tube is made up of a magnetic material which will move within the tube 12 to reduce the magnetic circuit reluctance when the coil is energized to a sufficient level. The core 20 has a hollow center of one diameter running almost its entire length and then changing abruptly to a smaller diameter hole for the rest of its length. A spring 22 is inserted within the hollow center of the core and is of such outside diameter that it easily fits within the larger diameter hole in the core but will not fit in the smaller diameter hole and therefore the bottom coils rest on a ledge 32 created by the diameter hole change within the core 20. The spring is a conventional type circular coil spring made preferably out of beryllium copper to produce a predetermined core bias spring force when inserted in the time delay capsule.
The spring 22 is held in position by a guide stem 24 as shown in FIG. 1 which has a lower or foot portion 36 which fits Within and runs the entire length of the spring and an upper or head portion 34 which has a smaller diameter than the large diameter hole in the core 20 and yet a larger diameter than the inside diameter of the spring coils so as to be able to hold the spring 22 in place. This guide stem is then held in position by the insertion of a tube cap 26. The spring 22 and the guide stem 24 cause the core to be biased against the closed end of the tube while not preventing it from being able to traverse the length of the tube in response to a magnetic field of sufficient magnitude and duration. The guide stem is also preferably formed of a non-magnetic material.
In accordance with this invention the cap 26 of the tube 12 has a flat top portion 27 with a neck or plug'- portion 29 with two grooved sections. The first grooved section 31 provides a space for a compressible annular gasket or O-ring seal 30 while the second provides a retaining groove 28 which will help provide a mechanical lock as indicated at 16 when the tube wallfiis rolled in. In assembly of the capsule 10, the O-ring 30 is positioned in the first groove and pressure is applied against the top of the cap holding it tight against the flange portion 14 of the tube which compresses the O-ring 30. Then, the side wall of the tube is rolled into the retaining groove 28 for drawing the cap down onto the gasket 30 which provides an oil tight seal between cap 26 and tube 12.
The capsule 10 is adapted for use within the coil of a magnetic relay or circuit breaker as is indicated diagrammatically at 33 in FIG. 1. When a surge of current goes through the magnetic circuit breaker, a large magnetic field is produced by the coil 33 which in turn exerts a force on the core 20 in the time delay capsule 10. This magnetic force tends to cause the magnetic core 20 to move toward the cap end of the time delay capsule for increasing the strength of the magnetic field established by the coil to the level necessary for actuating the magnetic relay or circuit breaker as will be understood. However, such movement of the core tends to be retarded by the presence of the spring 22 and the oil 18 within the capsule. That is, such movement of the core requires compressing of the biasing spring 22 situated between the core ledge 32 and the bottom surface of the top portion of the guide stem 24. Such core -.movement, also requires the oil 18 to be passed through the small passages provided by the hollow center of the core and by the small space between the core and the .tube 14. The action of the spring 22 and the oil 18' thus retard movement of the core in response to energization of the coil 33. If the silicone oil 18 and the biasing spring 22 were not present, a current surge in the coil 33 would be sufficient to cause the core to travel almost instantaneously to the top of the tube and cause the relay or breaker to trip. However, with the time ;delay provided by the capsule 10, the relay or breaker is actuated only where the coil 33 has been energized by sufficient current for a sufficient period of time or the level of current is of such magnitude that instant trip is desired.
a In the capsule 10, the spring 22 is easily assembled with the core and stem before assembly in the tube 14, thereby to assure that all coils of the spring are free to move in a proper manner. Further, the stem 36 assures the proper coiling of the spring 22 occurs during capsule operation. The capsule does not require brazing for sealing, and the spring 22 is well spaced from the sealed end of the tube 14 in any event, so that there is no risk of annealing the spring during capsule assembly. Accordingly, inexpensive and easily manufactured springs 22 are used in the capsule.
. A second embodiment of this invention is illustrated at 38in FIG. 2. This embodiment of the time delay capsule is similar to the preferred embodiment described earlier except for the cap 40 and the means for affixing the. cap 40 to the tube 12. That is, the tube 12, the core 20, the spring 22, the oil 18 and the guide stem 24 are identical in description and positioning as in the preferred embodiment described above with reference to FIG. 1. In the capsule 38, however, a cap 40 is made with a flat top portion 42 with a neck or plug portion 44 which fits into the tube 12. A circular groove 46 is made in the bottom periphery part of the top portion of the cap 40. In this groove 46 a washer-shaped ring 48 of-brazing material is inserted so it rests between the external periphery of the bottom of the top portion of the cap 40 and the flange portion 14 of the tube. This cap is brazed to the tube flange 14 by use of the ring 48 providing a leak-proof seal between the tube and cap which is well spaced from the spring 22. In this arrangement, even though the cap is brazed to the tube 12 for sealing the tube, the spring 22 is spaced from the brazed cap so that no annealing of turns of the spring occur during brazing of the cap to the tube. Accordingly, inexpensive materials are used in the spring. Further, the arrangement of the cap 40 for cooperation with the brazing ring 48 also assures that no splatter of brazing material into the tube 12 can occur.
A third embodiment of this invention is illustrated at 50 in FIG. 3. This embodiment of the time delay capsule is also similar to the preferred embodiment of the invention described earlier with reference to FIG. 1. That is, in the capsule 50 the tube 12 is filled with oil 18 and an end cap 52, provided with grooves 54 and 56, is fitted into the tube end along with an O-ring 30 to be sealed to the tube by a swaged or rolling in the side wall of tube 58.
With the capsule 50, however, a solid core 60 made out of magnetic material is provided in the configuration of a solid cylinder of diameter just smaller than the inside diameter of the tube 12 so it can move easily but snugly within the tube. This cylinder core 60 extends from the closed end of the tube about 40 percent of the way up the tube and then changes its diameter to a much smaller one. This top portion 62 of the core serves as a loose fitting arbor over which the spring 64 fits. The bottom portion of the spring coil rests on the ledge 66 which was formed where the diameter of the core is reduced. The top portion of the spring butts against the cap 52. The cap 52 is of the same general configuration as the one used in the capsule 10 except for an additional circular stem 68 added to the bottom of the cap which serves as a loose fitting arbor for receiving the top of the spring 64. In the capsule 50, the spring 64 is easily fitted on the arbors provided by the core and by the cap 52 to assure that the spring is accurately positioned within the tube 12 and the tube is then swaged or rolled in as at 58 for securing and sealing the capsule without use of brazing.
In view of the above, it will be seen that the several objects of the invention are achieved and the other advantageous results are obtained.
As various changes could be made in the above constructions, designs and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.
' I claim:
1. An improved time delay capsule for a magnetic circuit breaker or the like comprising a tube having an open end and a closed end, a magnetic core having an axial bore with a reduced diameter portion forming a shoulder within the bore adjacent one end of the core, the magnetic core being slidably disposed in the tube with said one end of the core at the closed end of the tube, a liquid of selected viscosity disposed in the tube, a coil spring disposed within the axial bore in the core and having one spring end engaging said shoulder, a stem having a reduced diameter portion fitted within the coil spring and having a head portion slidable in the bore in the magnetic core and engaging the opposite end of the coil spring, a cap fitted into the open end of the tube to engage the head portion of the stem, and means spaced from the coil spring sealing the cap to the tube.
2. An improved time delay capsule as described in claim 1 in which the tube has a flange around its open end, said cap has a top portion resting on said tube flange and a plug portion extending from said top into the end of the tube, said plug portion having first and second annular grooves therein, an annular gasket fitted around said cap plug into said first groove and compressed between the cap and flange for sealing the cap to the tube, and the tube is swaged into said second plug groove for sealing the cap and tube in said sealed relation.
3. An improved time delay capsule as described in claim 1 in which the tube has a flange around its open end, said cap has a top portion resting on said tube flange and a plug portion extending from said head into the end of the tube, and said cap top is brazed to said tube flange.
4. An improved time delay capsule as described in claim 3 in which said plug portion of the cap has an annular groove wherein a braze washer ring is disposed in said groove and brazed to said cap top and tube flange.
5. An improved time delay capsule for a magnetic circuit breaker or the like comprising a tube having an open and a closed end, said tube having a flange around its open end, a magnetic core having a foot portion slidable in the tube and having a somewhat reduced diameter portion extending from said foot portion to act as an arbor and creating a shoulder between said core portions, said core being disposed in the tube with said foot portion adjacent said closed tube end, a liquid of selected viscosity disposed in the tube for retarding sliding of the core in the tube, a coil spring disposed around said core arbor having one spring end engaging said shoulder, a cap fitted into the open end of the tube with a top portion resting on said tube flange and a plug portion extending from said top into the end of the tube to engage the remaining spring end for biasing the core to the closed end of the tube, said plug portion having first and second annular grooves therein, and an annular gasket fitted around said cap plug into said first groove and compressed between the cap and flange for sealing the cap to the tube, the tube being swaged into said second plug groove for sealing the cap and tube in said sealed relation.
6. An improved time delay capsule for a magnetic circuit breaker or the like comprising a tube having an open end and a closed end, a magnetic core slidably disposed in the tube, a liquid of selected viscosity disposed in the tube for retarding sliding of the core in the tube, a cap fitted into the open end of the tube with a top portion and a plug portion having first and second annular grooves therein, a coil spring having a first and a second end, said first end engaging said magnetic core and said second end engaging said plug portion of the cap thereby biasing the core toward the closed end of the tube, and an annular gasket fitted around said cap plug into said first groove and compressed between the cap and tube for sealing the cap to the tube, the tube being swaged into said second plug groove for sealing the cap and tube in said sealed relation.