Adjustable trip solenoid

[0002] This case is a divisional application of the U.S. patent application Ser. No. 09/515,112, filed Feb. 29, 2000 now U.S. Pat. No. 6,404,314, the contents of which are incorporated herein by reference thereto.

[0003] The present invention relates to an adjustable magnetic device.

[0004] A magnetic tripping device such as a solenoid generally comprises a coil or winding of wire through which a current is passed. The solenoid is configured to manipulate an actuator when the electromagnetic force generated by the coil exceeds a predetermined value of the solenoid.

[0005] The actuator is generally biased by a mechanical force in an opposite direction of the force generated by the electromagnetic field of the coil. This force is typically provided by a spring or other mechanical means wherein a plunger of the actuator is biased with respect to a stator positioned opposite to the actuator.

[0006] In addition, an air gap is positioned in between the actuator and a stator. The air gap is also located within the coil and provides an insulating barrier to the force generated by the electromagnetic field of the coil.

[0007] Accordingly, the tripping or predetermined tolerances of a solenoid are dependent upon the mechanical biasing force and the size and positioning of the air gap.

[0008] Moreover, the required range or predetermined tolerances of a magnetic tripping device vary in accordance with user's requirements such as the circuit loading.

[0009] Most solenoids are either fixed (nonadjustable) or have a single means of adjustment for either the air gap or biasing force.

[0010] In an attempt to accommodate these varying tolerances, an adjustable trip solenoid has been developed wherein the air gap between the stator and the actuator can be varied. However, the varying of this air gap also causes the spring biasing force to vary. Moreover, these changes are opposite with respect to each other. For example, increasing the air gap will also increase the biasing force of a spring.

[0011] Accordingly, there is a need for an adjustable solenoid wherein the air gap and mechanical biasing force can be varied so that as the air gap is decreased the mechanical biasing force is also decreased, and vice versa.

[0012] In an exemplary embodiment of the invention, an adjustable solenoid provides an adjustable air gap where the mechanical biasing force of the solenoid is either decreased or increased as the air gap is increased or decreased.

[0013] FIG. 1 is a front cross-sectional view of a solenoid constructed in accordance with the instant application;

[0014] FIG. 2 is a front cross-sectional view illustrating movement of a solenoid constructed in accordance with the instant application;

[0015] FIG. 3 is a view along lines 3—3 of FIG. 1;

[0016] FIG. 4 is a front perspective view of a portion of an alternative embodiment;

[0017] FIG. 5 is a front perspective view of the FIG. 4 embodiment illustrating movement thereof;

[0018] FIG. 6 is a front perspective view of the FIG. 4 embodiment illustrating movement thereof; and

[0019] FIG. 7 is a front perspective view of circuit breaker with an adjustable trip solenoid.

[0020] Referring now to FIGS. 1 and 2, an adjustable trip solenoid 10 is illustrated. In an exemplary embodiment, solenoid 10 is coupled to a circuit interruption mechanism 70 of a circuit breaker 72 (FIG. 7) wherein the movement or actuation of solenoid 10 causes a tripping mechanism 74 to trip circuit breaker 72.

[0021] Solenoid 10 has a support structure 12 into which a coil 14 is received. Coil 14 consists of a copper wire through which a current is passed. In accordance with the direction of the current being passed through coil 14, a magnetic field is generated by solenoid 10.

[0022] A plunger 16 for movement within solenoid 10 has an actuating member 18. Actuating member 18 is configured to pass through an opening 20 in support structure 12 of solenoid 10. In addition, actuating member 18 is configured to have a planar member 19, which in conjunction with actuating member 18 provides a receiving area for a portion of an actuating arm 21. The movement of plunger and accordingly actuating member 18 causes actuating arm 21 to move from a first position to a second position (illustrated by the dashed lines in FIG. 1). See also FIG. 2.

[0023] It is intended that actuating arm 21 is to be coupled to a mechanism 74 (FIG. 6) that in accordance with the movement of actuating arm 21 from the first position to a second position, will cause an intended result of the mechanism. For example, the movement of the mechanism will cause a circuit breaker to trip. Other uses may be the activation of warning lights, indication lights, status indicators and audible alarms, etc.

[0024] In addition, actuating arm 21 is provided with a biasing force in the direction of arrow 23 that must be overcome by the movement of plunger 18. In addition, the biasing force in the direction of arrow 23 also provides stability to actuating arm 21. Moreover, the biasing force causes actuating arm 21 to return to the position illustrated in FIG. 1, once plunger 16 returns to its initial position. A spring 25 or other bias producing means causes the biasing force to be placed upon arm 21.

[0025] As an alternative, and as illustrated by the dashed lines in FIG. 1, actuating arm 21 is positioned to rest upon plunger 18 and the biasing force of spring 25 is in a direction opposite to arrow 23. In addition, and as yet another alternative, actuating arm 21 may be replaced by a pair of actuating arms or planar member in which a portion is received and engaged by planar member 19 of plunger 18.

[0026] The movement of plunger 16 is caused by electromagnetic forces, which are generated by a current running through coil 14.

[0027] One end of a pair of springs 22 are secured to plunger 16 and the other end of springs 22 are secured to a pair of spring position stands 24. Springs 22 are positioned to provide a biasing force in the direction of arrow 26. Accordingly, and in order to position plunger 16 as illustrated by the dashed lines in FIG. 1, the electromagnetic force generated by solenoid 10 must overcome the biasing force of springs 22.

[0028] A stator 28 is positioned opposite to plunger 16 and an air gap 30 is defined between plunger 16 and stator 28. In addition, air gap 30 is positioned within coil 14.

[0029] Stator 28 is configured to have a first threaded portion 32 and a second threaded portion 34. An engagement surface 36 of spring position stands 24 also has a threaded portion 38. Threaded portion 38 is configured to have the same configuration (i.e. angle, size and slope) of first threaded portion 32.

[0030] Second threaded portion 34 of stator 28 is received and engaged in an opening 40 of support structure 12. The inner surfaces of opening 40 are configured to have a threaded engagement surface 42 that is sized and configured to engage second threaded portion 34 of stator 28.

[0031] An end portion 44 of stator 28 has an engagement opening 46. (FIG. 2) Engagement opening 46 is configured to receive and engage a tool such as a screwdriver, Allen wrench or other item for applying a rotational force to stator 28.

[0032] The pitch or angle of engagement of first pair of threads 32 and 38 is substantially opposite to second pair of threads 34 and 42. In addition, the size of threads 34 and 42 is substantially smaller than threads 32 and 38. In an exemplary embodiment, the size of threads 32 is 10 threads per inch, and the size of threads 34 is 32 threads per inch. Accordingly, there is approximately a 3 to 1 thread ratio between threads 32 and 34. Of course, it is contemplated that the dimensions, size and configuration of threads 32 and 34 may be larger or smaller than the dimensions mentioned above. Accordingly, and as a rotational force is applied to engagement opening 46 in a first direction, stator 28 will move in the direction of arrow 48. This movement of stator 28 will cause the size of air gap 30 to decrease. However, since the angle of engagement of first pair of threads 32 is opposite to that of second pair of threads 34, the movement of stator 28 in the direction of arrow 48, caused by the rotation of stator 28 in a first direction, will also cause spring position stands 24 to move in an opposite direction or in the direction of arrow 50. Moreover, and since the size of threads 32 is substantially larger than the size of threads 34, this movement is at a much greater rate with respect to each revolution of stator 28.

[0033] Accordingly, and as spring position stands 24 move in the direction of arrow 50, biasing force of springs 22 is decreased. A pair of shoulder portions 52 are located on the inner surface of support structure 12. Shoulder portions 52 provide an area into which spring position stands 24 can move as they move in the direction of arrows 50.

[0034] Accordingly, and as a rotational force is applied to stator 28 in a first direction, the size of air gap 30 is reduced while the biasing force of springs 22 is also reduced.

[0035] Conversely, and as a rotational force is applied to stator 28 in a second direction, the size of air gap 30 will increase, while the biasing force of springs 22 is also increased.

[0036] Thus, for a low X-setting on the solenoid, it is desirable to have a high-efficiency solenoid that can generate a high output force per Ampere-turn for any given construction. To accomplish this, it is desirable to have a small air gap with a low reverse bias force.

[0037] On the other hand, and for a high X-setting on the same solenoid, it is desirable to lower the efficiency of the solenoid and thereby lower the output force per ampere-turn for the same given construction. To accomplish this, it is desirable to have a large air gap with a large reverse bias force.

[0038] Accordingly, the solenoid of the instant application allows such adjustments to be made in a quick and convenient manner. Moreover, the same solenoid can be used for such applications.

[0039] In addition, and as contemplated in accordance with the instant application, the size and configuration of threaded portions 32 and 34 are configured to obtain a desired result. For example, each revolution of stator 28, or portion thereof, will cause stator 28 to move in a first direction of a known magnitude, while spring position stands 24 move in an opposite direction of a known magnitude. Therefore, and as a rotational force is applied to stator 28, the movement of stator 28 and spring position stands 24 will adjust the trip setting of solenoid 10 to a known value.

[0040] Referring now to FIG. 3, and as an alternative, surface 44 of stator 28 is marked with an indication arrow 54 while the surrounding surface of support structure 12 is also marked with a plurality of markings 56 which will indicate the trip setting of solenoid 10 when arrow 54 is pointing thereto. Of course, alternative marking arrangements are contemplated, such as, demarcations on the inner surface of opening 40 and stator 28 which will indicate the trip setting of solenoid 10 as stator 28 moves within opening 40. For example, such indications may be a color oriented scheme that provides a user with a quick and convenient means of determining the solenoid's trip setting.

[0041] Referring now to FIG. 4, an alternative embodiment of the instant application is illustrated. Here, component parts performing similar or analogous functions are numbered in multiples of 100.

[0042] Here, a solenoid 110 is configured to have a flux shifter 160. Flux shifter 160 is an elongated sleeve portion constructed out of a ferromagnetic material that is configured to be placed over plunger 116 and is capable of movement in the direction indicated by arrows 162.

[0043] Flux shifter 160 is secured to stator 128 by a pair of connection rods 164. Accordingly, and as a rotational force is applied to stator 128, through a tool inserted into engagement opening 146, the threaded portion 134 of stator 128 will travel through the threaded portion 142 of opening 140 which, depending on the direction of the rotational force, will cause stator 128 and accordingly flux shifter 160 to move in either direction of arrows 162.

[0044] Accordingly, and as stator 128 is moved in a direction away from plunger 116, air gap 130 increases in size and flux shifter 160 is repositioned to cover a portion or all of air gap 130. Since flux shifter 160 is constructed out of a ferromagnetic material, once it is positioned in close proximity to air gap 130, flux shifter 160 creates a path of lesser reluctance for the magnetic flux of solenoid 110 to travel.

[0045] For example, and referring now to FIG. 5, as flux shifter 160 covers air gap 130, the flux of solenoid 110 is partially illustrated by the dashed lines in FIG. 4. This positioning of flux shifter 160 will allow solenoid 110 to be able to accept a higher current value through coil 114 before plunger 116 is actuated. Moreover, the size of air gap 130 is also increased in the position illustrated by FIG. 5 this also increases in the amount of flux required to actuate plunger 116.

[0046] Conversely, and as flux shifter 160 and stator 128 are moved back into the position illustrated by FIG. 4, the flux of solenoid 110 is illustrated partially by the dashed lines in FIG. 6.

[0047] Comparing solenoid 110 of FIGS. 5 and 6 shows a high-efficiency electromagnetic system in FIG. 6 and a low efficiency electromagnetic system in FIG. 5. Since higher magnetic forces are generated from a solenoid having high efficiency, the magnetic forces generated by solenoid 110 of FIG. 6 will be greater than those of FIG. 5 at a given solenoid current value. Alternatively, for a given trip force, the solenoid 110 of FIG. 6 will have a trip point (activation threshold) at a lower solenoid current than will the solenoid 110 of FIG. 5.

[0048] Therefore, solenoid 110 provides the user with a single means of adjustment for introducing flux shifter 160 while concurrently increasing air gap 130 and vice versa. This configuration provides a wide range of trip settings for solenoid 110.

[0049] In an exemplary embodiment, solenoid 110 has a low gradient compression spring or springs 122 that has a de minimus change in bias force as stator 128 moves.

[0050] While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.