Patent Publication Number: US-6703572-B1

Title: Anti-twist insert for circuit breaker handler accessory

Description:
FIELD OF THE INVENTION 
     This invention is directed generally to electromechanical devices and, more specifically, to an anti-twist insert for use in a switch-lock assembly of a circuit breaker. 
     BACKGROUND OF THE INVENTION 
     Electrical devices, such as circuit breakers, are used in many residential, commercial, and industrial electric systems, being indispensable components of such systems in protecting against over-current conditions. A circuit breaker includes a switch that can be placed in at least two positions: an ON position and an OFF position. In the ON position the circuit breaker closes an electrical circuit, thus allowing the flow of current in the particular circuit. In the OFF position the circuit breaker opens the electrical circuit, thus interrupting the flow of current in the particular circuit. 
     Under certain circumstances, it is desirable to lock the switch in either the ON position or the OFF position. For example, if a person is servicing components of an electrical circuit it is highly desirable to ensure that the circuit breaker remains in the OFF position. Serious bodily injury, even death, may result if the circuit breaker is accidentally turned ON while the person is in contact with components of the electrical circuit. Similarly, to prevent trespassers from tampering with an electrical circuit, it may be desirable to lock a circuit breaker in the ON position. This would ensure that only an authorized person may manually interrupt the flow of current. 
     Although some switch-locking devices for circuit breakers are available, they are in general expensive, complex, or flimsy. For example, a switch-locking device comprises a support part, a locking part, and a spring clip. The spring clip has a middle section that is fixed in the locking part, two legs that are slidably-engaged in two slots of the support part, and two ends that are inserted into two holes of a circuit breaker. After the locking part is swung in a counterclockwise direction to fit over the support part, the circuit breaker can be locked by inserting a padlock into a ring of the support part. Although such a switch-locking device provides adequate support when subjected to a tensile force, i.e., when the device is being pulled, it is nevertheless too flimsy when it is subjected to compressive or rotational forces, i.e., when the device is being pushed or twisted. The weak protection that the device provides when being pushed or twisted is due in great part to the fact that the support comes only from the two legs of the spring clip. For example, the switch-locking device can be separated from the circuit breaker when it encounters a relatively low twisting force because the two legs are easily displaced from their respective holes. Regardless of whether the twisting motion is accidental or intentional, the twisting motion renders the switch-locking device highly unreliable. 
     Accordingly, there is a need for a simple component that would prevent the easy removal of the switch-locking device when a twisting force is applied. There is also a need for a simple component that would provide greater support when a compressive force is applied to the switch-locking device. 
     SUMMARY OF THE INVENTION 
     Briefly, in accordance with the foregoing, a switch-lock assembly, for securing a circuit breaker in one of a plurality of circuit breaker positions, includes a switch-lock attachment and an anti-twist insert. The switch-lock attachment includes a spring member adapted to engage a retaining area of the circuit breaker, a support member adapted to accommodate the spring member, and a locking member connected with the support member via the spring member. The insert includes a securing end adapted to engage a first area of the circuit breaker for limiting the movement of the insert relative to the circuit breaker, and an interface area adapted to engage the switch-lock attachment for limiting the movement of the switch-lock attachment relative to the insert. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a perspective diagrammatic of a circuit breaker embodying the present invention; 
     FIG. 2 is an exploded diagrammatic of a switch-lock attachment comprising a support part, a locking part, and a spring clip; 
     FIG. 3 a  is a perspective view of one embodiment of an insert; 
     FIG. 3 b  is a planar view of the insert of FIG. 3 a ; 
     FIG. 4 is a perspective diagrammatic of an assembled embodiment of the present invention; 
     FIG. 5 is a perspective diagrammatic of the embodiment of FIG. 4 shown before the spring clip is connected to a circuit breaker; 
     FIG. 6 is a perspective diagrammatic of the embodiment of FIG. 4 shown after the spring clip is connected to the circuit breaker and before an insert is inserted into the circuit breaker; 
     FIG. 7 is a perspective diagrammatic of the embodiment of FIG. 4 shown after the insert is inserted into the circuit breaker and before the locking part is placed in a locked position; 
     FIG. 8 is a perspective diagrammatic of the embodiment of FIG. 4 shown after the locking part is placed in a locked position and before the circuit breaker is secured with a padlock; 
     FIG. 9 is a perspective view of another embodiment of the insert of FIG. 3 a ; and 
     FIG. 10 is a perspective view of another embodiment of the support part of the switch-lock attachment shown in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
     Referring now to the drawings, and initially to FIG. 1, an anti-twist insert  20  and a switch-lock attachment  22 , in one embodiment of the invention, are mounted on a circuit breaker  24 . The switch-lock attachment  22  is shown in a secured position, and a padlock  25  is used to lock the switch-lock attachment  22  and the insert  20  to the circuit breaker  24 . The insert  20  and the switch-lock attachment  22  will be described in more detail below. 
     The circuit breaker  24  includes a casing  26  and a switch area  28 . The casing  26  is made of two similar parts, a cover and a base, wherein the base is adapted to hold most of the internal components of the circuit breaker  24 . In general, after the internal components of the circuit breaker  24  are installed on the base, the circuit breaker  24  is enclosed by positioning and securing the cover on top of the base. 
     The switch area  28  is rectangularly shaped, and it includes a switch  30 , a securing slot  32 , a retaining area  34 , and a resting area  36 . The switch  30  can be used to manually move the circuit breaker  24  between a plurality of circuit breaker positions. For example, an operator can move the switch  30  between an ON position and an OFF position. In the ON position, the circuit breaker  24  is adapted to allow the flow of current through a particular electrical circuit, while in the OFF position the circuit breaker  24  is adapted to interrupt the flow of current through the particular electrical circuit. The switch  30  can also be used to indicate the position of the circuit breaker  24 . For example, an operator would want to confirm that the circuit breaker  24  is in the OFF position before commencing human interaction with the internal components of the circuit breaker  24  or with an electrical circuit connected to the circuit breaker  24 , such as when routine maintenance is required. 
     The securing slot  32  is located on one end of the switch area  28 , near the switch  30 , and it protrudes a short distance into the casing  26 . The retaining area  34  is located next to the switch  30 , and it includes two symmetrically-opposed retaining holes  38 . The resting area  36  is located opposite the securing slot  32 , and is generally a flat surface. 
     Referring now to FIG. 2, one embodiment of the switch-lock attachment  22  will be described in more detail. The switch-lock attachment  22  includes a support member  40 , a locking member  42 , and a spring member  44 . The support member  40  includes a flat mating surface  46 , a curved mating surface  48  located next to the flat mating surface  46 , a pair of channels  50  located on one end of the flat mating surface  46 , and a ring  52  centrally located on the curved mating surface  48  and protruding from the curved mating surface  48 . The channels  50  are formed along the entire thickness of the support member  40 , as shown. 
     The locking member  42  includes a primary mating surface  54  and a secondary mating surface  56 , wherein the primary mating surface  54  is adapted to match the flat mating surface  46  and the secondary mating surface  56  is adapted to match the curved mating surface  48 . The locking member  42  also includes a pair of parallel openings  58  and a retaining opening  60 . The parallel openings  58  protrude through the entire thickness of the locking member  42 , and the retaining opening  60  is positioned perpendicular to the parallel openings  58  for connecting the parallel openings  58  at one end. A ring slot  62  is positioned on the secondary mating surface  56 , and the ring slot  62  is formed through the entire thickness of the locking member  42 . 
     The spring member  44  includes a middle section  64  connecting a pair of legs  66  to each other, each one of the legs  66  having a retaining end  68 . To connect the spring member  44  to the locking member  42 , the middle section  64  is inserted into the retaining opening  60  and each of the legs  66  is inserted into respective ones of the parallel openings  58 . To connect the spring member  44  and the locking member  42  to the support member  40 , each of the legs  66  is inserted through respective ones of the channels  50  wherein each retaining end  68  depends beyond channels  50  of the support member  40 . 
     When the switch-lock attachment  22  is assembled, the locking member  42  is adapted to move between a secured position and an open position. In the secured position, the primary mating surface  54  is in contact with the flat mating surface  46  and the secondary mating surface  56  is in contact with the curved mating surface  48 . Also, the ring  52  protrudes through the ring slot  62 . In the open position the locking member  42  pivots around the middle section  64 , rotating in a counterclockwise direction around the axis of the middle section  64 , eventually causing each one of the legs  66  to separate from the respective ones of the parallel openings  58 . As the locking member rotates in the counterclockwise direction, the ring slot  62  disengages away from the ring  52 . 
     Referring now to FIGS. 3 a  and  3   b , one embodiment of the anti-twist insert  20  will be described in more detail. The insert  20  includes a securing end  70 , an interface area  72 , and a supporting end  74 . The securing end  70  has a generally rectangular shape and is adapted to fit in the securing slot  32  of the circuit breaker  24 . The interface area  72  includes a plurality of notches  76 , a first mating surface  78 , and a second mating surface  80 . The notches  76  are located along the first mating surface  78 , are symmetrically located with respect to each other, and are adapted to match the channels  50  of the support member  40 . The first mating surface  78  is adapted to match the flat mating surface  46  of the support member  40  and the primary mating surface  54  of the locking member  42 . The second mating surface  80  is adapted to match the curved mating surface  46  of the support member  40  and the secondary mating surface  54  of the locking member  42 . The second mating surface  80  includes a ring aperture  82  adapted to match the ring slot  62 . 
     In another embodiment, the insert  20  includes an observation opening  84  located between the securing end  70  and the interface area  72 . The observation opening  84  is adapted to allow an operator to visually inspect the position of the circuit breaker  24 . This is particularly useful when a plurality of circuit breakers  24  are installed next to each other, in a parallel configuration, because, otherwise, the switch  30  would be obstructed from plain view. The observation opening  84  allows the operator to do a cursory visual inspection of each switch to determine, for example, whether a particular circuit breaker  24  is ON or OFF. 
     In one embodiment of the present invention, the insert  20  is composed of a semi-rigid material. The material can be a metal or a plastic, e.g., a commercially available steel. 
     Referring now to FIG. 4, the assembly of the insert  20  and the switch-lock attachment  22 , in one embodiment of the present invention, will be described in more detail. The insert  20  is positioned over the support member  40  such that the ring  52  protrudes through the ring aperture  82 , the first mating surface  78  contacts the flat mating surface  46 , the second mating surface  80  contacts the curved mating surface  48 , and each one of the notches  76  is aligned with one of the channels  50 . 
     Each one of the legs  66  is inserted through one of the notches  76  such that the spring member  44  holds the insert  20  between the locking member  42  and the support member  40  of the switch-lock attachment  22 . When the locking member  42  is in the secured position, the separation distance between the support member  40  and the locking member  42  is generally equal to a thickness T of the insert  20 , i.e., the separation distance is minimal. The connection between the notches  76  and the spring member  44 , via each one of the legs  66 , minimizes the lateral movement of the switch-lock attachment  22  relative to the insert  20 . Similarly, the connection between the ring aperture  82  and the ring  52  minimizes the lateral movement between the switch-lock attachment  22  and the insert  20 . The two connecting points, at the notches  76  and at the ring aperture  82 , provide a bonding between the insert  20  and the switch-lock attachment  22  such that any generally rotational movement, including any lateral movement, between the insert  20  and the switch-lock attachment  22  is generally prevented. In other words, rotational and/or lateral movement of the switch-lock attachment  22  is inhibited by at least two connections when the insert  20  is installed. First, the ring  52  which protrudes through the ring aperture  82  opposes rotational or lateral movement of the switch-lock attachment  22 . Second, the spring member  44  when received in the notches  76  also opposes rotational or lateral movement of the switch-lock attachment  22 . 
     Referring now to FIGS. 5-8, the assembly of the insert  20  and the switch-lock attachment  22  to the circuit breaker  24  will be described. When the insert  20  is not installed, the only connection between the switch-lock attachment  22  and the circuit breaker  24  is provided by the two legs  66  of the spring member  44  which are retained by the two retaining holes  38 . If the switch-lock attachment  22  is subjected to a relatively low twisting force, such as a rotational force around the axis of the legs  66 , the switch-lock attachment  22  can easily snap out of place. For example, a twisting force can be applied accidentally when an operator is locking the switch-lock attachment  22  with a locking mechanism such as the padlock  25 , resulting in the dislodgment of the switch-lock attachment  22  from the circuit breaker  24 . This type of dislodgment is particularly likely to happen when a single, heavy padlock  25  is used to lock a plurality of switch-lock attachment  22 . Note that the padlock  25  is only exemplary and other locking devices may be used, e.g., a “U” type lock, a chain-padlock combination, or a cable lock. The dislodgment of the switch-lock attachment  22  from the circuit breaker  24  can also occur when a plurality of padlocks  25  are used to lock a single switch-lock attachment  22  via a padlock accessory. 
     After assembling the insert  20  in-between the support member  40  and the locking member  42  and interlocking the insert  20  with the spring member  44 , as described above, each retaining end  68  is squeezed towards the other such that the securing end  70  is aligned with the securing slot  32  and the supporting end  74  is aligned with the resting area  76 . As the locking member  42  is moved to its open position, the switch-lock attachment  22  is urged towards the circuit breaker  24  causing each retaining end  68  to be received in each one of the retaining holes  38 . After positioning the secured end  70  into the securing slot  32 , the locking member  42  is moved to its secured position. 
     In the secured position, the spring member  44  holds the insert  20 , the support member  40 , the locking member  42 , and the circuit breaker  24 , in tension. The secured end  70  provides the anti-rotational support to prevent the accidental or intentional twisting of the switch-lock attachment  22  from the circuit breaker  24 . The supporting end  74  provides the compression support to prevent the potential dislodgment of the switch-lock attachment  22  from the circuit breaker  24 . In addition, the padlock  25  can be attached to the ring  52  to lock the switch-lock attachment  22  to the circuit breaker  24 . 
     Adding the insert  20  to the switch-lock attachment  22  increases the force required to twist-off the switch-lock attachment  22  from the circuit breaker  24 . Whereas before adding the insert  20  the only connection between the switch-lock attachment  22  and the circuit breaker  24  relied on the two legs  66 , now, the switch-lock attachment  22  also relies on the securing end  70  of the insert  20  to limit any rotational or lateral movement of the switch-lock attachment  22  relative to the circuit breaker  24 , and in particular the twisting motion around the axis of the legs  66 . Furthermore, the supporting end  74  of the insert  20  adds extra support to the switch-lock attachment  22  and limits the displacement of the switch-lock attachment  22  when subjected to a compressive force, such as when the switch-lock attachment  22  is pushed towards the circuit breaker  24 . 
     In another embodiment, a plurality of circuit breakers  24  are installed next to each other, each circuit breaker  24  having a switch-lock attachment  22  with an insert  20 , and locking all the circuit breakers  24  to their respective switch-lock attachment  22  and insert  20  using a single padlock  25 . Using a single padlock  25  for a plurality switch-lock attachments  22  enables an operator to monitor the operation of a multitude of circuit breakers  24  with the use of a single key. Also, where the position of a plurality of circuit breakers  24  must be made dependent on each other, it is easier to group the circuit breakers  24  into one single system that contains a single padlock  25 . For example, it may be desirable to ensure that while a number of the plurality of circuit breakers  24  are in the ON position, another number of the plurality of circuit breakers  24  are in the OFF position. Using a single padlock  25 , and therefore a single key, makes the monitoring of the plurality of circuit breakers  24  easy and efficient. 
     In another embodiment, a plurality of padlocks  25  are used to lock a single switch-lock attachment  22 , which includes an insert  20 , to a single circuit breaker  24  via a padlock accessory. Using a plurality of padlocks  25  in the locking of a single circuit breaker  24  can be useful for safety reasons. For example, when a number of operators may be simultaneously performing maintenance operations on a circuit that is controlled by the circuit breaker  24 , it is desirable to ensure that that the circuit breaker  24  remains locked in the OFF position until all the operators finish their particular duties. When the operators finish their respective duties, each operator unlocks a respective one of the plurality of padlocks  25  that is assigned to that particular operator. Thus, if the duties of an operator take a longer period of time, that operator does not have to worry about being electrocuted as a result of the circuit breaker  24  being switched ON while he or she is working on the circuit. Having the insert  20  improves protection against twisting forces acting on the switch-lock attachment  22 , which can cause the dislodgment of the switch-lock attachment  22  from the circuit breaker  24 , that are caused by the combined weight of the plurality of padlocks  25 . 
     Referring now to FIGS. 9 and 10, another embodiment of the present invention will be described. In this embodiment, an insert  120  has an interface area  172  that is smaller than in the previous embodiment, which is shown in FIGS. 3 a-   3   b . A support member  140  includes a slotted hole  186  and an interface slot  188 . The slotted hole  186  is located between a flat mating surface  146  and a curved mating surface  148 , and it protrudes through the entire thickness of the support member  140 . The interface slot  188  is located on the flat mating surface  146 , next to the slotted hole  186 , and it has a depth which is generally equal to the thickness T of the insert  120 . The interface area  172  is adapted to match the interface slot  188 . Furthermore, the interface area  172  is adapted to prevent interference between the insert  120  and the spring member  44  (not shown). More specifically, the interface area  172  is narrow enough such that each one of a pair of legs  166  of the spring member  44  will freely engage the support member  140  and a locking member  142 . A supporting end  174  is adapted to allow its insertion through the slotted hole  186 . In other words, a width W 1  of the supporting end  174  should be smaller than a width W 2  of the slotted hole  186 . 
     When connecting the insert  120  with the switch-lock attachment  22 , the supporting end  174  is inserted through the slotted hole  186  and the interface area  172  is placed in contact with the interface slot  188 . In this embodiment, the relative motion between the insert  120  and the switch-lock attachment  22  is prevented mostly by the connection formed between the interface area  172  and the interface slot  188 . The rest of the assembly of the switch-lock attachment  22  and the insert  120  to the circuit breaker  24  is similar to the previous embodiment described in reference to FIGS. 2-8. 
     While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.