US 3729696 A
A hydraulic-magnetic time delay actuator for use with circuit breakers, switches or relays, comprising a non-magnetic time delay tube encircled by a solenoid coil. The tube contains a retarding fluid and a magnetic core, the core being movable longitudinally in the tube in response to the magnetic flux generated by the coil. An armature is pivotally located in the magnetic field of the coil and is movable thereby to actuate the relay, circuit breaker or switch. The movable core has formed therethrough an axial bore which houses a valve and forms a seat for the valve adjacent one end of the bore. A helical stop spring, a portion of which has an outer diameter greater than the interior diameter of the bore, is located therein. The stop spring is inserted into the bore by twisting the spring to reduce its diameter while concurrently pushing it into the bore. The spring is held in place in the bore by frictional engagement with the interior surface thereof. The leading edge of the inserted stop spring is located a preselected distance from the valve seat to limit the movement of the valve away from its seat. The stop spring is tapered slightly in the direction of the valve and is formed of a magnetically permeable material in order to increase the efficiency of the actuator.
Claims available in
Description (OCR text may contain errors)
Unite States Patent [191 Pope [451 Apr. 24, 1973  TIME DELAY ACTUATOR  ABSTRACT [75 1 llnvemo'r: Ralph Pope, Robbinsvme, NJ hydrauhc-magnetic time delay actuator for use with c1rcu1t breakers, swltches or relays, comprlsmg a nonl l g Heineman" Electric p y magnetic time delay tube encircled by a solenoid coil. Trenton, The tube contains a retarding fluid and a magnetic  Filed: p' core, the core being movable longitudinally in the tube in response to the magnet1c flux generated by the  'Appl. No.: 247,732 coil. An armature is pivotally located in the magnetic field of the coil and is movable thereby to actuate the 52 US. (:1. ..335/62, 251/337, 335/239 relay breaker F The movfible has  km Cl Holh 7/03 formed therethrough an ax1al bore whlch houses a valve and forms a Seat for the valve adjacent one end  Field of Search ..335/62, 61, 218, of the bore A helical Ste 8 tin a onion of which has an outer dlameter greater than the mtenor dlameter of the bore, is located therein. The stop spring is  References Cned inserted into the bore by twisting the spring to reduce vUNITED STATES PATENTS its diameter vvhile concurrently pushing it into the I bore. The sprmg held in place in the bore by fric- 2,694,789 11/1954 W1lckens ..335/2l8 tiona] engagement i the interior surface thereof 3,308,847 3/1967 Umam The leading edge of the inserted stop spring is located 3,183,931 5/1965 Alford ..l37/612.l
Primary Examiner1-lar0ld Broome Att0rney .loseph G. Denny, III et a1.
a preselected distance from the valve seat to limit the movement of the valve away from its seat. The stop spring is tapered slightly in the direction of the valve and is formed of a magnetically permeable material in order to increase the efficiency of the actuator.
9 Claims, 3 Drawing Figures O 6 34 23 m 26 I /7 I I I 43 /8 0 l I 42 i 3.320 /6 l3 44 Q I 56 I Patented April 24, 1973 2 Sheets-Sheet l BACKGROUND OF THE INVENTION The invention relates generally to circuit breakers, relays or switches. More specifically the invention relates to circuit breakers, relays or switches incorporating a hydraulic-magnetic actuator comprising a solenoid coil wound around a sealed tube containing a movable core and a retarding liquid through which the core is moved in response to the energization of the coil. The actuator also includes an armature pivotally supported adjacent the tube for movement toward and away from said tube depending upon the energization of thesolenoid coil.
The purpose of the retarding liquid is to create a time delay between the energization of the coil at a preselected level and the subsequent tripping of the circuit breaker, or operation of the relay or switch contacts.
In devices of this type, when the coil is unenergized or energized below a preselected level, the core is moved by means of a biasing spring to a-position in the tube most remote from the armature. Upon energization of the coil to a preselected level, however, the movable core is pulled toward the armature against the bias of the biasing spring by the magnetic flux generated by the coil, but its movement toward the armature is retarded by means of the retarding liquid which is forced to pass through the narrow space between the interior surface of the tube and the movable core. The rate at which the core moves through the tube is determined by the viscosity of the retarding liquid. When, after a preselected time, the core reaches the end of the sealed tube nearest the armature, the circuit breaker, relay or switch, as the case may be, is activated.
When the coil is subsequently de-energized or energized below a preselected level, the core is again moved by the biasing spring toward the end of the tube most remote from the armature to a reset position. It is, of course, desirableto have the movable core reach its reset position as rapidly as possible. In order to accomplish this the movable core is provided with a central bore or passage extending longitudinally through the core. A ball-type check valve is located in this passage, the valve being seated or unseated depending upon the direction of movement of the COI'Ci- In response to the movement of the core toward the armature, the valve is moved onto its seat whereby the retarding liquid is blocked from passing through the central passage in the core, while in response to the movement of the core away from the armature, the valve is unseated to permit substantially unobstructed flow of the retarding liquid through the passage.
The invention is directed specifically to a means for limiting the movement of the ball-check valve away valve may move away from its seat so as to permit its rapid return to its seat in response to the motion of the core toward the armature.
A drawback associated with the above noted prior art arrangement is that it necessitates the accurate drilling of a diametrically disposed hole into which the stop pin may be inserted, thereby adding to the cost of the actuator and the time required to assemble it.
OBJECTS AND SUMMARY OF THEINVENTION A principal object of this invention is the provision of an improved hydraulic-magnetic time delay actuator for use in connection with circuit breakers, switch or relays.
A still further object is to provide an improved means for limiting the movement of a check valve to control the flow of a retarding liquid through a movable core in a time delay actuator of the above noted type.
A still further object is to provide a time delay actuator which is inexpensive and easily assembled.
The preferred embodiment of the invention comprises a hydraulic-magnetic actuator which includes a hollow non-magnetic tube around which is wound a solenoid coil and in which is contained a movable core and a retarding liquid. The movable core has formed therethrough a central bore in which is located a check valve. The bore forms a seat near one end thereof on which the valve may become seated to obstruct the flow of retarding liquid through said core. A helical stop spring at least a portion of which has an initial exterior diameter greater than the interior diameter of the bore is twisted against itself to reduce its diameter and is thereby inserted into the bore, the leading edge of the inserted spring being spaced a preselected distance from the seated valve, so as to limit its movement away from the seat when it becomes unseated. The stop spring is held in place in the bore by frictional engagement with the interior surfaces thereof. The stop spring may be made of a magnetically permeable material and, in addition, may be tapered in the direction of the valve seat to further improve the operation of the actuator.
The foregoing and other objects of the invention, the principles 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.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings;
FIG. 1 is a longitudinal sectional view through the casing of the circuit breaker of the invention, showing the operating mechanism of the circuit breaker in elevation and including a longitudinal sectional view of the time delay tube and movable core according to the invention incorporated therein;
FIG. 2 is an enlarged longitudinal sectional view of the movable core showing the details of the check valve and stop spring; and
FIG. 3 is a traverse cross sectional view of the movable core taken along the line 3-3 of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS For illustrative purposes, the improved hydraulicmagnetic actuator according to the invention is shown as being incorporated into a circuit breaker of the type shown in U.S. Pats. Nos. 2,694,789, 2,000,109 and 2,360,922. It should, however, be understood that the improved hydraulic-magnetic actuator disclosed herein may be incorporated into various other types of circuit breakers, and in addition, may also be incorporated into various relays and switches.
Referring to FIG. 1 of the drawings, there is shown a circuit breaker comprising an insulating case 11 and an operating mechanism 12. The operating mechanism 12 is described in detail in the prior patents noted above, among others, and will therefore be described only briefly immediately hereinafter.
The circuit breaker operating mechanism 12 comprises a main frame 13 which is fixedly supported within the insulating case 11. The frame 13 is generally L-shaped, is made of a magnetically permeable material, and is provided with a pair of ears 15 containing holes for carrying a pivot pin 16 on which a switch blade 17 is rockable into and out of engagement with a stationary contact 18 connected to a line terminal 19. The switch blade 17 is continuously biased in the direction away from engagement with the contact 18 by a main spring 20.
The switch blade 17 is coupled to an operating handle 21 through an overcenter toggle comprising the links 22 and 23. The handle 21 is integral with a handle link 24 which is pivotally supported on a pin 25 carried in holes in another pair of ears 28 extending from the main frame 13. The toggle may be latched or locked to form a rigid connection between the handle 21 and the switch arm 17 by means of a latch shaft 26 which engages a tooth 27 on the link 22, as explained more fully in U.S. Pat. No. 2,360,922. The latch shaft 26 may be rotated to collapse the toggle by moving the trip arm 29 thereof, to allow the tooth 27 to move past the flat face of the shaft 26. If, when the switch blade 17 is locked into contact with the contact 18, the trip arm 29 is so moved, the switch blade -17 will move away from the contact 18 as a result of the collapse of the toggle and the biasing action of the main spring 20.
The moving of the trip arm 29 to collapse the rigid toggle and open the circuit breaker is effected by a hydraulic-magnetic time delay actuator 30. The time delay actuator 30 comprises an L-shaped armature 31 having an attractable arm 32 and an actuating arm 33 and pivotally supported from the main frame 13 on a pin 34. The armature 31 is continuously biased for rotation in a counter-clockwise direction by means of a spring (not shown) wound on the pin 34 so that the actuating arm 33 is normally out of engagement with the trip arm 29 and the attractable arm 32 is in abutment with a stop member 36, which limits the rotation of the armature 31.
The actuator 30 also includes a time delay tube 41 around which is wound a solenoid coil 40, the time delay tube being supported in an opening in one leg of the L-shaped main frame 13. The armature 31 is, of course, made of a magnetically permeable-material so as to be movable by the magnetic field generated by the solenoid coil 40. As is well known in the art of circuit breakers, one end of the coil 40 is soldered or otherwise fixedly connected to the switch blade 17 by means of a braided wire 44, while the other end of the coil 40 is connected to the terminal 43.
The time delay tube 41 contains a movable core 42 and a retarding liquid 45 and is closed at one end by a magnetic pole piece 46. The core 42 is made of a magnetically permeable material and is movable longitudinally through the retarding liquid 45 in the tube 41 by the magnetic field generated by the coil 40. The core 42 is biased by a biasing spring 47 away from engagement with the pole piece 46, the forepart of the core 42 being reduced in diameter to permit passage thereof through the spring 47 into contact with the pole piece when the core is in its attracted position. The core 42 makes a slip fit with the interior surface of the tube, such fit being sufficiently loose to permit slow seepage of retarding liquid from one side of the core 42 to the other during axial movement of the core toward the pole piece 46 under the influence of the magnetic field generated by the coil 40. The core 42 has formed therethrough an axial bore or passage 50 having located therein a check-type ball valve 51. The bore 50 adjacent one end of the core 42 is narrowed to form a seat 52 for the valve 51.
Also contained within the bore 50 is a helical stop spring 55 whichserves to limit the movement of the ball valve 51 away from its seat 52. The spring 55 is tapered in diameter in the direction of the valve 55 and is preferably made of a magnetizable material to further add to the magnetizable mass of the core 42 and thereby improve the operation of the actuator 30. A least a portion of the spring 55 has an outer diameter, prior to insertion into the bore 50, which is greater than the interior diameter of the bore 50.
The stop spring 55 is inserted into the bore by twisting the spring 55 on itself to reduce its diameter while concurrently pushing it into the bore 50. In order to facilitate insertion into the bore 50, the stop spring 55 is terminated on its leading or root end 56 with a diametrically disposed tang 57. An inserting tool (not shown) is designed to pass through the .stop spring .55 and engage this tang 57 during the insertion process. By pushing the spring 55 into the bore 50 and concurrently twisting the spring 55 on itself by means of the tang 57, the spring 55 is reduced in diameter sufficiently to allow it to enter the bore 50.
The spring 55 is held in place in the bore 50 by frictional engagement with the interior surface thereof, resulting from the natural tendency of the spring to return to its original diameter while being restrained against doing so by the smaller diameter of the bore 50. The leading edge of the inserted stop spring 55 is located a preselected distance fromthe valve seat by means of the inserting tool (not shown) to limit to a preselected distance the movement of the valve away from its seat.
In operation, when the current flow through the solenoid coil 40 reaches a predetermined level the magnetic flux generated thereby causes the core 42 to move toward the pole piece 46 against the bias of the biasing spring 47. The rate of movement of the core 42 is dependent upon the viscosity of the retarding liquid 45 in the time delay tube 41. When rapid movement of the core is desired, a light liquid is employed, whereas when a more retarded movement is desired a more viscous fluid may be used in the tube. After the lapse of a sufficient amount of time the core 42 approaches the pole piece 24 sufficiently to decrease the reluctance of the magnetic current to a point where the attractable arm 32 of the armature 31 is attracted into contact with the pole piece 46. As the attractable arm 32 moves toward the pole piece 46, the actuating arm 33 of the armature abuts and moves the trip arm 29, thereby turning the lock shaft 26 and collapsing the toggle to open the circuit breaker contacts.
When the solenoid coil 40 is de-energized, the core 42 is moved by the biasing spring 47 away from the pole piece 46 toward its reset position at the end of the time delay tube 41 most remote from the pole piece 46. During this movement the valve 51 moves away from its seat 52 until its movement is limited by the leading end 56 of the stop spring 55, thereby permitting a substantially unimpeded flow of retarding liquid through the central bore or passage 50 in the movable core 42. As a result of the flow of liquid through the bore 50, the movable core 42 returns to its reset position in an appreciably shorter time than would otherwise be possible.
Having described this invention, what I claim is:
1. A time delay actuator comprising,
a magnetic frame,
a tube supported from the frame,
a coil encircling said tube,
a pole piece forming a closure for one end of said tube,
an armature pivotally supported from said frame and rotatable toward and away from said pole piece,
a fluid filling said tube,
a magnetically permeable core in said tube,
said core being movable along the axis of said tube through said fluid under the influence of the magnetic flux generated by said coil, said core including an axial bore therethrough, a ball valve located in said bore,
said bore forming a seat for said valve, and a helical spring located in said bore, a portion of said spring having an outer diameter, prior to insertion into said bore, greater than the inner diameter of said bore, the leading edge of said inserted spring being located a preselected distance from said valve seat to limit the movement of said valve away from said seat.
2. The combination recited in claim 1 wherein the outer diameter of said helical spring is tapered in the direction of said valve.
3. The combination recited in claim 2 wherein said helical spring is made of a magnetically permeable material.
4. The combination recited in claim 3 wherein said spring includes a diametrically disposed tang at its leading end, said tang suitable for being grasped during insertion of said spring into said bore to reduce its diameter and thereby permit said spring to enter said bore.
5. In a time delay actuator including a time delay tube, a solenoid coil wrapped around said tube, a retarding fluid and a movable magnetic core within said tube, a biasing spring for biasing said core to a first position in said tube, said core being movable longitudinally through said tube against the bias of said biasing spring to a second position in response to the magnetic field generated by said coil, said core having formed therethrough an axial bore, a valve housed in said bore, said bore forming a seat for said valve, the improvement comprising resilient means located within said bore on the side of the valve opposite said seat for limiting the movement of said valve away from its seat when said core moves from said second position to said first position, said resilient means being in tensionecl condition while in place in said bore to exert an outward force against the interior surface of said bore to thereby hold said means in place in said bore.
6. The combination recited in claim 5 wherein said resilient means comprises a helical stop spring, a portion of said stop spring having an outer diameter, before insertion into said bore, greater than the interior diameter of said bore.
7. The combination recited in claim 6 wherein said stop spring is tapered in diameter with the leading end of said inserted spring having a smaller diameter than the trailing end of said inserted spring.
8. The combination recited in claim 7 wherein said spring is made of a magnetically permeable material.
9. The combination recited in claim 8 wherein the leading end of said inserted spring includes a diametrically disposed tang.