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Title:
AUXILIARY CONTACT INTERLOCKING DEVICE
United States Patent 3593232
Abstract:
Disclosed is a circuit protector having an interlock arrangement for operating an auxiliary switch when the protector is tripped by an overcurrent but not when the main contacts are manually opened. An interlock plate receives the stepped end of a support arm and normally holds the auxiliary switch in a first condition. Overcurrent tripping rotates the support arm to free the interlock plate, allowing the auxiliary switch to operate. The auxiliary switch is reset through the interlock plate when the main contacts are manually closed.


Inventors:
Shibuya, Eiji (Iruma-Gun, JA)
Konomoto, Takeshi (Fukuoka-Cho, JA)
Sawamura, Akihiro (Kita-Adachi-Gun, JA)
Application Number:
04/845840
Publication Date:
07/13/1971
Filing Date:
07/29/1969
Assignee:
Sanken-Airpax Company Limited (Tokyo, JA)
Primary Class:
International Classes:
H01H71/46; (IPC1-7): H01H9/24
Field of Search:
335/160,161,11,17 317
View Patent Images:
US Patent References:
3388357Magnetic type circuit breakerJune 1968Lawson
2656439Circuit breakerOctober 1953Gelzheiser
Primary Examiner:
Broome, Harold
Claims:
What we claim and desire to be secured by United States Letters Patent is

1. A circuit protector comprising a set of main contacts including a movable contact, a set of auxiliary contacts, a handle, a collapsible linkage coupling said handle to said movable contact, said main set of contacts being manually opened and closed by operation of said handle whereby said collapsible linkage follows a first path of movement in response to manual operation, overcurrent trip means coupled to said linkage for collapsing said linkage to open said main contacts in response to an overcurrent, at least a portion of said linkage following a second path of movement in response to overcurrent tripping different from said first path, an interlock plate operatively coupled to said auxiliary set of contacts, means resiliently biasing said interlock plate toward said linkage, a support arm coupled to said interlock plate and restraining said plate in a first position whereby said auxiliary contacts are in a first condition, said support arm including means spaced from said first path but lying in said second path of movement whereby said support arm is tripped by said portion of said linkage in response to overcurrent tripping to release said interlock plate with said auxiliary contacts assuming a second condition.

2. A circuit protector according to claim 1 wherein said linkage includes a contact arm carrying said movable contact, said interlock plate being resiliently biased toward said contact arm, whereby movement of said contact arm during manual reclosure of said main set of contacts urges said interlock plate back to said first position to reset said auxiliary set of contacts.

3. A circuit protector according to claim 2 wherein said support arm is rotatably mounted and includes a stepped end defining a shoulder, said interlock plate having a hole freely receiving said stepped end of said support arm, and means resiliently biasing said stepped end of said support arm toward one edge of said hole whereby said interlock plate engages said shoulder when said interlock plate is in said first position.

Description:
This invention is related to a means of interlocking a set(s) of auxiliary contacts with manual and tripping operations of an electrical circuit breaking device.

With regard to electromagnetic switches capable of interrupting a circuit when an excessively large current flows in the circuit, a variety of devices have heretofore been announced; those of large current interrupting ratings are usually known as no-fuse circuit breakers, while those of smaller current interrupting ratings, as circuit protectors.

This invention is generally concerned with a device which belongs to the latter group mentioned above.

Some types of circuit protectors produced by the prior art incorporate a number of auxiliary contacts which are operated as the main contacts are either closed or opened. In these types of circuit protectors, however, auxiliary contacts are made to operate both in the case of the opening of main contacts by a flow of overcurrent (called tripping). In this manner, it is not possible to discriminate from the operation of the auxiliary contacts whether the circuit protector is opened by hand or by an overcurrent. Therefore, circuit protectors of the prior art cannot be used in such applications as may require generation of alarms only when the circuit protectors are tripped by an overcurrent. For disabling the auxiliary contact circuit at the time of the manual opening, circuit protectors of the prior art require provision of a special, external circuit which disconnects the auxiliary contact circuit from external circuits such as alarm circuits selectively when the circuit protector is opened by hand. The need of such special circuit inevitably introduces inconvenience in use as well as complexity in structure, while it incurs an increase in cost.

Among conventional no-fuse circuit breakers of large current ratings, some types include a built-in control circuit which permits operation of the auxiliary contact circuit only when the circuit breaker is tripped by an overcurrent. Circuit protectors of small current ratings, however, are generally made small in structure and hence complex in internal mechanism, and also have a relatively weak overcurrent tripping force. Therefore, it has hitherto been extremely difficult to provide circuit protectors with a special, built-in device which selectively permits operation of the auxiliary contact circuit only at the time of overcurrent tripping.

In view of the foregoing description, it is a general object of this invention to solve this problem and provide a new auxiliary contact interlocking device.

These and further objects and advantages will be more apparent from the following specification, claims and appended drawings in which:

FIGS. 1 and 2 are diagrams illustrating a conventional circuit breaking switch with a set of auxiliary contacts;

FIG. 3 is a diagram illustrating an embodiment of this invention;

FIG. 4 is an enlarged diagram illustrating in detail only the interlock portion shown in FIG. 3;

FIG. 5 is a diagram illustrating an embodiment of this invention which is a manually operated position;

FIG. 6 is an enlarged diagram illustrating in detail only the interlock portion shown in FIG. 5;

FIG. 7 is a diagram illustrating an embodiment of this invention which is in a tripped position;

FIG. 8 is an enlarged diagram illustrating in detail only the interlock portion shown in FIG. 7;

FIG. 9 is a diagram showing only the principal portion of an embodiment of this invention;

FIG. 10 is another diagram showing only the principal portion of an embodiment of this invention.

For better understanding of this invention, the structure of a conventional circuit protector having a set of auxiliary contacts will first be described in connection with the accompanying drawings or more particularly with FIGS. 1 and 2. FIG. 1 illustrates only the principal mechanism of a conventional circuit protector whose main contacts are in a closed position. In FIG. 1, a circuit current enters the circuit protector via terminal 1, flows through lead 2, trip coil 3, lead 4, contact arm 5, main contact 6, and the opposite main contact 7, and finally goes out via a terminal 8 into a load circuit. While the circuit current is maintained at a normal level, current is permitted to continuously flow via the circuit protector. Should an overcurrent flow, the trip coil 3 is energized and opens the closure of the main contacts 6 and 7, thereby protecting the load circuit from being overloaded. The circuit protector shown in FIG. 1 is under the normal current condition in which the main contacts 6 and 7 are closed permitting a circuit current to flow. Both the contact arm 5 and a link 23 are pushed upward by the force f3 of a spring (not shown) but are held in position by a cam 22. A portion of the cam 22 is engaged and fixed with a pin 25. (Note: This pin is usually called a shearing pin.) If, under this condition, a handle 18 is thrown from the present position toward the left in FIG. 1 for opening the circuit protector, the handle 18 rotates counterclockwise with a pin 19 as its supporting point, causing a pin 20 also to rotate counterclockwise or to rise with respect to the present position. When the pin 20 is raised, both the cam 22 and a support 21 are also moved upward, because they are coupled together by the pin 20. On the other hand, a guide pin 26 is provided at an end of the link 23 and fitted in a portion of the cam 22, while a coupling pin 27 is used to connect the support 21 with the link 23. These two pins, 26 and 27, are used to hold the link 23 in place, resisting an upward force f3 . However, as the cam 22 and hence the link 23 move upward, the holding force provided via the pins 26 and 27 will be removed. When the holding force is removed, the link 23 and contact arm 5 are freed and pushed upward by the force f3 , opening the closure of the main contacts 6 and 7.

During the manual operation of the circuit protector, one end of the cam 22 remains coupled with a pin 25 and hence all of the support 21, cam 22, and line 23 are moved together as a single unit. Although the support, cam, and link are permitted to rotate counterclockwise, they are restrained from drawing a free, large locus, because all three are coupled together.

Now, the following description applies to the case in which the circuit protector is tripped by an overcurrent.

When an overcurrent flows through the circuit protector, the trip coil 3 is energized and a core 41 attracts an armature 31. As the armature 31 is attracted by the core 41, it rotates counterclockwise with a pin 40 as its supporting point while the other end of the armature 31 is raised with respect to the present position. The other end of the armature 31 then hits one end of a tripping rod 24 situated adjacent to the armature 31, providing a counterclockwise torque f2 to the tripping rod 24. Under normal conditions, a clockwise torque f1 is applied on the tripping rod 24 which then functions to maintain the coupling status of the pin 25 and cam 22, preventing a free movement of the cam 22. If the armature 31 hits the tripping rod 24 with a larger torque f2 than the torque f1 applied on the tripping rod 24, it causes the tripping rod 24 to rotate counterclockwise, thus disengaging the pin 25 from the cam 22. As the cam 22 is disengaged from connection with the pin 25, the cam 22 is freed for movement. The force holding the link 23 downward is thus removed, permitting the link 23 and the support 21 connected together with the link by the coupling pin 27 to rotate counterclockwise by the force f3 applied on the link 23 by a spring (not shown). The contact arm 5 connected with the link 23 by a pin 28 is now permitted to trip upward and to open the closure of the main contacts 6 and 7. In this particular case, the movement of the support 21 and link 23 is not restricted by the cam 22 and thus the locus drawn by the support and link as they rotate counterclockwise should become larger than that exhibited when the circuit protector is manually operated. The difference between the two loci is utilized in this invention to provide an auxiliary contact interlocking device.

The operation of auxiliary contacts is now described with reference also to FIG. 1. In circuit protectors of the prior art, it has hitherto been the practice to interlock auxiliary contacts with the tripping operation of main contacts. As shown in FIG. 1 for example, the contact arm 5 is used to control interlock plate 9 which is free for moving upward or downward as controlled by the contact arm 5. The interlock plate 9 in turn is pushing a movable rod 10 downward. While the main contacts are making a closure as shown in FIG. 1, the movable rod 10 is pushed downward by the contact arm 5 via the interlock plate 9, which is then depressing a spring contact 11. Thus, the spring contact 11 is permitted to keep contact with an auxiliary contact 15. Under this condition, an electrically through circuit is completed via a terminal 12, the spring contact 11, contact 15, and terminal 13. When the main contacts 6 and 7 open the closure, the contact arm 5 will be raised, permitting the interlock plate 9 to move upward. The force holding the movable rod 10 in place is then removed, causing the spring contact 11 to switch to the other auxiliary contact 16. Thereby, another electrical circuit is completed via the terminal 12, spring contact 11, contact 16, and terminal 14.

As has been described with reference to a specific example, auxiliary contacts of the prior art are operated every time when the main contacts open the closure, regardless of whether the opening of the main contacts is made by hand or by tripping, and thus it is not possible to discriminate from the operation of the auxiliary contacts whether the circuit protector is tripped by an overcurrent or by hand.

An object of this invention is to provide a means of discriminating between manual tripping and overcurrent tripping in a circuit protector.

Those not mentioned in the foregoing description but shown in FIG. 1 include: a microswitch assembly 17, a supporting plate 29 which maintains many parts of the circuit protector in place, a supporting point 30 for the contact arm 5, and a housing 32 which contains the entire mechanism of the circuit protector.

For the purpose of illustration only, the operation of a conventional circuit protector has been described with reference to FIG. 1. Of course, a circuit protector, to which this invention is applied, shall not be limited to one illustrated in FIG. 1 but can be extended to such a mechanism as shown in FIG. 2. With reference now to FIG. 2, there is illustrated a support 21 which replaces, and provides the same function as, the cam 22 used in the circuit protector illustrated in FIG. 1. When an armature 31 hits a tripping rod 24 in the counterclockwise direction at the time of overcurrent, a support 21 is freed from engagement with the tripping rod 24 and a link 23, and permits the link 23 to trip and rotate counterclockwise, thus opening the closure of main contacts 6 and 7. On the other hand, manual opening of the circuit protector maintains engagement between the support 21 and the link 23 and thus the counterclockwise rotation of the jointed unit of the support 21 and link 23 draws a rather limited locus as compared to that drawn when the circuit protector is tripped by an overcurrent. Therefore, by utilizing a difference between the two loci, such a mechanism as illustrated in FIG. 2 can also be used to embody this invention.

Briefly stated, a feature of this invention is to utilize a difference in locus to provide an auxiliary interlocking device as follows: In a circuit protector whose main contacts can be opened either manually or by an overcurrent tripping as mentioned in the foregoing, a spring-loaded plate interlocked with a set(s) of auxiliary contacts is additionally provided, which will be activated to operate the auxiliary contacts only when the circuit protector is tripped by an overcurrent. Said spring-loaded interlock plate is usually held in place by an additionally installed support arm at all times except when the circuit protector is tripped by an overcurrent. When the circuit protector is tripped by an overcurrent, a specific part of the circuit protector tripping mechanism which draws a unique locus for overcurrent tripping applies a force to said support arm in order to free said spring-loaded interlock plate from the existing restraint. Hence, auxiliary contacts are operated by the freed spring-loaded interlock plate. On the other hand, an arrangement is made in this invention so that, when the circuit protector is tripped by hand, no force is applied to said support arm and hence auxiliary contacts remain deactivated.

Another feature of this invention is to utilize the contact arm, which has one of the main contacts at its end, for resetting by hand the circuit protector from its tripped position to the normal position.

A further feature of this invention is to utilize the support arm and spring-loaded interlock plate for imparting a controlling force from the contact arm to auxiliary contacts.

These and other objects and features of this invention will be better understood upon consideration of the following detailed description of several embodiments of this invention with reference to the accompanying drawings and more particularly with FIGS. 3 through 10.

FIG. 3 illustrates an embodiment of this invention with its main contacts being closed. The parts constituting the main tripping mechanism of the embodiment illustrated in this figure are the same as those illustrated in FIG. 1 and are numbered in the same manner as in FIG. 1, except for some portions that have been omitted for ease of understanding. This omission is also practiced in FIGS. 5 and 7 which will be described later.

In the device illustrated in FIG. 3 which is an embodiment of this invention, a microswitch assembly 17 has a set of auxiliary contacts which are to be operated by a spring contact 11. Perpendicularly to one side of the spring contact 11, a movable pin 10 is provided, which is pressed downward by a spring-loaded interlock plate 9. By the force of a spring, the interlock plate 9 tends to move upward but is held in position by a support arm 35. Therefore, the movable pin 20 keeps depressing the spring contact 11, having it make contact with an auxiliary contact 15. The support arm 35 is coupled with a supporting plate 29 by a pin 38 together with a spring 37, which therefore tends to rotate counterclockwise by the force of the spring 37. The counterclockwise rotation of the support arm 35 is however held by the interlock plate 9 because the support arm 35 and interlock plate 9 are jointed together through a hole 33 made in the interlock plate 9. The support arm 35 can be rotated clockwise only when a clockwise torque greater than the resisting force by the spring 37 is applied to the support arm. Although the support arm 35 is engaged with the interlock plate 9, it is permitted to rotate clockwise because there is provided an open space in the hole 33 toward the clockwise direction of the support arm 35 as illustrated in FIG. 4 which is an enlarged diagram of the portion in which the support arm 35 is engaged with the interlock plate 9. The top edge 36 of the support arm 35 is the place to be hit by a tripping rod 24 and thus should be placed in a locus drawn by the bottom end of the tripping rod 24. In FIG. 3, the pictures of a support 21, cam 22, and link 23 are omitted.

Referring now to FIGS. 5 and 6, an operation which will occur when a handle 18 is thrown by hand from right to left for opening the closure of main contacts 6 and 7 is described. The main tripping mechanism will operate in an identical manner as described for FIG. 1, i.e., as the handle 18 is rotated counterclockwise, a pin 20 and its associated portion are also rotated counterclockwise and moved upward with a pin 19 as their supporting point. Following the movement of the pin 20, both a support 21 and a cam 22 (both not shown in FIG. 5) also move upward. By the upward movement of these parts, a link 23 (not shown in FIG. 5) together with a contact arm 5 is also moved, causing the main contacts 6 and 7 to open the closure. In this operation, attention must be paid to the relative position of a tripping rod 24. Since no external force is applied to the tripping rod 24 during this operation, a pin 25 is permitted to maintain engagement with the cam 22. As has already been described with reference to FIG. 1, the support 21, cam 22, and link 23 are thus moved in a rather limited locus and cannot make a large counterclockwise movement. Therefore, the tripping rod 24 exerts no force on the top edge 36 of the support 35. For this reason, although the main contacts 6 and 7 open their closure, the support arm 35 is permitted to maintain engagement with an interlock plate 9 as illustrated in FIG. 6, thus preventing the interlock plate 9 from being freed from the engagement. Thereby, the status of auxiliary contacts remains unchanged.

With reference now to FIGS. 7 and 8, the operation of the tripping mechanism in the case of overcurrent tripping is described: When an overcurrent flows through a trip coil 3, a core 41 attracts an armature 31, causing one end of the armature to hit a tripping rod 24 as already mentioned for the conventional circuit protector illustrated in FIG. 1. Thus, a pin 25 is disengaged from a cam 22, freeing the cam for movement. As a result, a support 21 and link 23 are also freed from restraint imposed by the cam 22 and permitted to rotate counterclockwise. By the force f3 of a spring imparted via the link 23 and a contact arm 5, both the support 21 and the link 23 will rotate counterclockwise, drawing a relatively large locus. The bottom end of the tripping rod 24 which is secured to the support 21 by the pin 25 strikes the top edge 36 of a support arm 35. If the striking force is greater than the counterclockwise torque holding the support arm 35 in position, the support arm 35 will rotate clockwise. By the clockwise rotation of the support arm 35, the step-shaped bottom of the support arm 35 is disengaged from the interlock plate 9, thus permitting the interlock plate 9 to trip upward by the force of a spring. The interlock plate 9 is then permitted to move upward as far as either a point at which the leg of the support arm 35 fills a coupling hold 33 as illustrated in FIG. 8, or a point at which the interlock plate 9 hits the contact arm 5.

As the interlock plate moves upward, a movable pin 10 accompanies the interlock plate 9 and hence the pressure exerted on a spring contact 11 is removed, permitting the spring contact 11 to switch to an auxiliary contact 16 by its own spring force. Then, another electrical circuit is completed via a terminal 12, the spring contact 11, auxiliary contact 16, and terminal 14. FIG. 7 illustrates the status of a circuit protector incorporating an embodiment of this invention at the instant when the circuit protector has just been tripped by an overcurrent and the closure of main contacts 6 and 7 have just been opened. If a handle 18 is not held in place by hand, the handle 18 will also eventually be thrown to the left automatically following the opening of the main contacts 6 and 7, and accordingly a tripping rod 24 will also be moved to the same position as it would be located when the circuit protector is manually opened as illustrated in FIG. 5.

Reference now should be made to FIGS. 9 and 10 for operation and structure of a support arm 35. FIG. 9 shows a side view of a support arm 35 holding an interlock plate 9 in place. The support arm 35 is mounted on a supporting plate 29 by means of a pin 38 and is powered by a spring 37. The support arm 35 thus tends to rotate by the force of the spring 37 but is held in place by the interlock plate 9. If, under this condition, an oppositely directed force greater than this spring force is applied to the support arm 35, the support arm 35 rotates toward that direction and the leg of the support arm 35 is freed from engagement with the interlock plate 9 and falls into a hole 33. FIG. 10 shows a side view of a support arm 35 whose leg falls into a hole 33.

When the load circuit is restored to normal after the circuit protector is tripped by an overcurrent, there is a need for resetting the circuit protector to bring the status of both the main contacts and the auxiliary contacts to normal. It may be possible to reset the auxiliary contacts directly by hand, but this invention utilizes the movement of a contact arm 5 for this purpose. When the circuit protector is reset by hand (i.e., when a handle 18 is brought back to the normal position), the bottom end of the contact arm 5 moves downward. In this invention, this movement is utilized to push an interlock plate 9 downward until the step-shaped end of a support arm 35 engages with the interlock plate 9.

When a few embodiments of the invention have been illustrated and described in detail, it is particularly understood that invention is not limited thereto or thereby and can be embodied in many other ways. In the embodiment of this invention described in the foregoing, the tripping rod 24 is adopted for striking the support arm 35. In another embodiment of this invention, for example, a unique hammering part for striking the support arm 35 may be used and provided directly on either the support 21 or the line 23. In a further embodiment of this invention, such an arrangement as either the support or the link itself strikes the support are 23 can be realized. In a still further embodiment of this invention, the structure of the support arm and interlock plate can take a different form from that illustrated and described hereinbefore.

The principles of this invention enable circuit protectors of small current ratings to operate auxiliary contacts only when tripped by an overcurrent, so that the opening of circuit protectors by an overcurrent can be discriminated from that by hand. Devices incorporating an embodiment of this invention thus do not require an additional circuit for this discrimination and can be used an a convenient, economic circuit breaking switch. When the devices are opened by hand, they do not produce alarms because their auxiliary contacts are not operated. Therefore, these devices can be used not only as circuit protectors but also as conventional on-off input switches, providing an extremely convenient means of switching electrical circuits.