GOFMAN EFIM (IL)
ONUFRIENKO JURY IVANOVICH (UA)
ONUFRIENKO VIKTORIA (IL)
CHERTKOVA SOFIA (IL)
ULANOVSKY EDUARD (IL)
GOFMAN EFIM (IL)
ONUFRIENKO JURY IVANOVICH (UA)
ONUFRIENKO VIKTORIA (IL)
CHERTKOVA SOFIA (IL)
| US5500630A | 1996-03-19 | |||
| US5546062A | 1996-08-13 |
| 1. | An electrical switching device, associated with an electrical circuit having an electrical contact arrangement, said switching device comprising: a casing supporting said switching device, a latchable member carrying at least one electrical contact, arranged for movement away from the electrical contact arrangement in response to a minimum tripping force thereat, wherein said contactcarrying member is movable between first and second positions, wherein, in said first position, said at least one electrical contact is in touching contact with the contact arrangement such that the electrical circuit is closed and, in said second position, said at least one electrical contact is not in touching contact with the contact arrangement such that the electrical circuit is open, an actuating mechanism, movable between first and second operative orientations, for selectably moving said contactcarrying member between said first and second positions, and coupling means associated with said contactcarrying member and said actuating mechanism, wherein, when said minimum tripping force is not present, said coupling means is operative to transfer a positioning force from said actuating mechanism to said contactcarrying member, so as to permit movement of said contactcarrying member between said first and second positions, and wherein, in the presence of said minimum tripping force, said coupling means is operative to prevent transfer of a positioning force from said actuating mechanism to said contactcarrying member, thereby permitting movement of said contactcarrying member away from said first position to said second position, regardless of the operational orientation of said actuating mechanism . |
| 2. | An electrical switching device according to claim 1, wherein said coupling means comprises tripping means, a latching element, a latching mechanism, and biasing means, wherein: said tripping means is operative, in the absence of at least said minimum tripping force, to engage said latching element, thereby causing it to engage said contactcarrying member, and, in the presence of at least said minimum tripping force, to release said latching element from engagement with said contactcarrying member, said latching element engages said tripping means and said contactcarrying member, so as to transfer a positioning force from said actuating mechanism to said contactcarrying member, said latching mechanism is operative to engage said latching element with said tripping means and said contactcarrying member in the absence of at least said minimum tripping force, and said biasing means is operative to force said contactcarrying member away from said first position to said second position in response to said latching element being released from engagement with said contactcarrying member by said tripping means in the presence of said minimum tripping force . |
| 3. | An electrical switching device according to claim 2, wherein said tripping means comprises a lever element, pivotably mounted for movement between a first position wherein said lever element engages said latching element and a second position wherein said lever element does not engage said latching element, and resilient tension means in association with said lever element so as to provide said minimum tripping force; and wherein said lever element is coupled to said resilient tension means to transfer said minimum tripping force to said latching element via said lever element An electrical switching device according to claim 3 wherein said resilient tension means further includes means for adjusting said resilient tension means so as to provide a selected minimum tripping force. An electrical switching device according to claim 1 wherein said at least one electrical contact on said contactcarrying member comprises contact means of the movable bridge contact type An electrical switching device according to claim 2 wherein said biasing means comprises a resilient tension means An electrical switching device according to claim 6 wherein said biasing means further includes means for adjusting said resilient tension means so as to provide a selected biasing force An electrical switching device according to either of claims 1 and 2 wherein said coupling means and said latchable contactcarrying member are supported by said movable actuating member An electrical switching device according to claim 2 wherein said tripping means is supported by said contactcarrying member An electrical switching device according to either of claims 8 and 9 wherein said biasing means is coupled to said latchable contactcarrying member and is additionally supported at an anchor location on said casing. |
FIELD OF THE INVENTION
The present invention relates to electrical switching devices
BACKGROUND OF THE INVENTION
Electrical switching devices often include means to provide protection for electrical systems from electrical fault conditions such as current overloads and short circuits Such devices often include a spring-driven, latchable actuating mechanism which opens electrical contacts so as to interrupt the current through an electrical system in response to abnormal currents The actuating mechanism is latched by a trip bar which in turn is actuated by a trip mechanism The trip mechanism can include a thermal trip device which responds to persistent low levels of overcurrent and a magnetic trip device which responds instantaneously to high overcurrent levels, such as those generated by a short circuit in the electrical system The trip mechanism unlatches the actuating mechanism which opens electrical contacts in the electrical system to interrupt the current therethrough
It is required that the actuating and trip mechanisms interrupt the current in the electrical system in as short a time as possible for a number of reasons In the case of a high overcurrent, even a single current cycle can pass enough energy to an electrical system to cause serious damage to electrical circuitry which is intended to be protected by the switching device Additionally, even lower level overcurrents can cause arcing across electrical contacts as they open if they are not separated quickly enough This is true even when the current is switched off in a normal, non-fault, condition. Arcing also causes overcurrent damage and erodes electrical contacts An additional problem resulting from arcing is that it generates metallic particles, soot, and other debris which can damage the switching device and nearby components and which can impair their operation.
Many existing electrical switching devices, such as the circuit breaker disclosed in United States Patent Number 4,983,939, which also includes means for adjusting the magnitude of the required tripping force and a thermal tripping mechanism, employ springs to store mechanical energy to quickly actuate the tripping mechanism in case of a fault
current. One of the problems with existing art is that faster contact separation requires more stored mechanical energy. This, in turn, requires larger springs, which are more massive, and which are, hence, slower to actuate.
SUMMARY OF THE INVENTION
The present invention seeks to provide an electrical switching device to protect an electrical circuit against damage due to abnormal current conditions in the circuit, which overcomes disadvantages of known art by providing faster switching and hence, greater protection from abnormal current conditions as well as greatly reduced chance of arcing and damage therefrom.
There is thus provided, in accordance with a preferred embodiment of the invention, an electrical switching device including a latchable contact carrier carrying one or more electrical contacts that can move between positions wherein an associated electrical circuit is closed and open, an actuating mechanism to selectably drive the contacts between closed and open positions, and a coupling mechanism dependent on the presence of a minimum tripping force on the contacts. When the minimum tripping force is not exceeded, the coupling mechanism transfers the positioning force from the actuating mechanism to the contacts; and when the minimum tripping force is exceeded, no positioning force from the actuating mechanism is transferred and the contacts are driven to the open position for any orientation of the actuating mechanism.
Further in accordance with a preferred embodiment of the invention, the coupling mechanism includes a latch, a latching mechanism, a tripping mechanism, and a biasing spring. The latch locks onto the contact carrier to transfer the positioning force from the actuating mechanism to the contact carrier. The latching mechanism resets the latch in its locked position in relation to the contact carrier and the tripping mechanism. The tripping mechanism engages the latch and sets the level of the minimum tripping force required to be applied to the contacts to release the latch and decouple the contact carrier and contacts from the rest of the switching device, thereby freeing them to be driven to the open position by the biasing spring.
Additionally in accordance with a preferred embodiment of the invention, the latch, latching mechanism, and the tripping mechanism are mounted on the actuating mechanism, which allows the tripping mechanism to function with no dependence on the orientation of the actuating mechanism.
In accordance with alternative embodiments of the invention, the magnitude of the minimum tripping force required to release the latch and/or that of the force provided by the biasing spring are adjustable.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which
Fig 1 is a block diagram of an electrical switching device constructed and operative in accordance with a preferred embodiment of the present invention
Fig 2 is a pictorial representation of an electrical switching device constructed and operative in accordance with a preferred embodiment of the present invention with the switch in a closed position
Fig 3 is a pictorial representation of an electrical switching device constructed and operative in accordance with a preferred embodiment of the present invention with the switch in a tripped position
Fig 4 is a pictorial representation of an electrical switching device constructed and operative in accordance with a preferred embodiment of the present invention with the switch in an open position.
Fig 5 is a pictorial representation of an electrical switching device constructed and operative in accordance with a further preferred embodiment of the present invention with an alternative actuating mechanism and with the switch in a closed position
DETAILED DESCRIPTION OF THE INVENTION
Referring now to Figure 1, there is shown, a block diagram of an electrical switching device, referred to generally as 10, in accordance with a preferred embodiment of the present invention The switching device 10 is associated with an existing electrical circuit 1 1 with a contact arrangement 12. Electrical contacts 13 mounted on a contact carrier 14 can move between a closed position wherein they are in touching contact with the contact arrangement 12 of the circuit 11 and an open position wherein they do not touch the contact arrangement
12 of the circuit 1 1 In normal operation of the circuit, the switching device can be operated to close or open the circuit by moving the contacts and the contact carrier by means of an actuating mechanism 15 Actuating mechanism 15 can be driven by any suitable means such as a mechanical levering mechanism or a magnetic driver such a solenoid
As will become apparent from the following description, in response to abnormal current conditions in the circuit 1 1, the tripping mechanism 18 is tripped, releasing the latch 16, and the contacts 13 and the contact carrier 14 are forced to the open position by a biasing force provided by a biasing means 19
In a preferred embodiment of the present invention, the contact carrier 14 is normally engaged with a latch 16, which is held in place by a latching mechanism 17 and a tripping mechanism 18 When the latch is thus engaged, the positioning force from the actuating mechanism 15 is transferred to the contact carrier 14 to selectably open or close the contacts
13 with those 12 of the circuit 1 1 When there is an abnormal current condition in the circuit 1 1 , a force is generated on the contacts 13 of switching device 10 This force can optionally be a magnetic force directly caused by the current in the contacts 13, or a thermomechanical force in response to the heating from the current When the magnitude of this force exceeds a predetermined level, the tripping mechanism 18 is tripped to release the latch 16, thereby disengaging it from the contact carrier 14 When this occurs, the contact carrier 14 is thus free to move the contacts 13 to the open position in response to the action of the biasing force 19 Since the only coupling between the contact carrier 14 and the actuating mechanism 15 is via the latch 16, the biasing force 19 only needs to drive the contact carrier
14 and the contacts 13 to open the circuit As will be appreciated by persons skilled in the art, the small mass of the carrier 14 and contacts 13 in relation to that of the actuating
mechanism 15 and the rest of the switching device 10 is quickly and readily movable to respond to abnormal current conditions in the circuit 11, thereby providing improved protection thereto in comparison with that provided by prior art devices.
In accordance with a preferred embodiment of the invention, the switching device 10 can be closed or opened under normal circuit operation as a result of the action of an actuating mechanism 15. In response to an abnormal current in the circuit, the device 10 will open as a result of the action of a tripping mechanism 18. These different states of operation of the switching device are shown in Figures 2 through 4.
In Figure 2, there is shown a pictorial representation of an electrical switching device based on a preferred embodiment of the present invention wherein the switch is in a closed position Referring now to Figure 2, switch contacts 23, which are of the movable bridge type, are in touching contact with circuit contacts 22 A contact carrier 24 extends vertically, as shown in the figure, from the contacts 23 through insulating plate 61 and conducting shield 60, both of which serve to shield the interior of the switching device 20 from arcs Insulating plate 61 has the additional function of guiding the contact carrier 24 along its required path within the switching device 20 The contact carrier 24 is attached to a biasing spring 29 within the switching device 20, which, in turn, is anchored at location 51 to the switch casing The carrier 24 has a protrusion 52 along part of its vertical length ending with a shelf 53 that engages a latch 26 This enables the downward closing force, in the illustration, from an actuating mechanism, shown generally by 27, to be transferred to the contact carrier 24 and the contacts 23. In the figure, the actuating mechanism 27 is driven by a mechanical handle 54, but this is only by way of example
In the absence of forces, the latch 26 is positioned by a latching spring 55 In addition, the latch 26 is engaged and held in position by a tripping lever 56. The force which restrains the tripping lever 56 in place is set by a tripping spring 57, which is optionally adjustable by a screw mechanism 58.
In a preferred embodiment of the present invention, the arrangement of the circuit contacts 22 in the circuit 21 and the switch contacts 23 creates a magnetic circuit so that any current in the circuit 21 will cause the contacts 23 to be urged upward by a magnetic force generated in the magnetic circuit. It will be appreciated by persons skilled in the art, that the magnitude of the force so generated is proportional to the current. This force on the contacts
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23 is transferred via the contact carrier 24 to the latch 26 at the point of contact with the shelf 53 on the contact carrier The latch 26, in turn, transfers the force to the tripping lever 56, wherein it is balanced, across the pivot 59 of the tripping lever 56, by the force provided by the tripping spring 57.
Under normal current conditions in circuit 21, the force provided by the tripping spring 57 is greater than the tripping force exerted by the latch 26 on the tripping lever 56 The latch 26 and the tripping lever 56 will not move, and the switch 20 will remain in the untripped state shown in Figure 2.
In the presence of abnormal current conditions in the circuit 21, the upward magnetic force on the contacts 23, which is transferred to the tripping lever 56 as described above, is greater than the force set by the tripping spring 57 The tripping force on the latch 26 overcomes the opposing force from the tripping spring 57 and the latch 26 is tripped, as shown in Figure 3. The contact carrier 24 pushes the latch to a vertical position, as shown in the figure and is driven upwards by the magnetic force in the contacts 23 and by the force of the biasing spring 29, until they are no longer in touching contact with the circuit contacts
22 Since, as will be appreciated by those familiar with the art, the magnetic force is proportional to the current in the contacts 23, a greater overcurrent generates a greater tripping force, which causes the switch 20 to open faster, thereby providing maximal protection to the circuit 21 associated with the switch The circuit 21, now open, has no current flowing in it, but the current carrier 24 and contacts 23 are still driven upward and held in the open position by the biasing spring 29
It should be noted that the moving contacts 23 have rod-like protrusions 62 which point away from the fixed circuit contacts 22 Since, as will be appreciated by those familiar with the art, arcs tend to originate or be drawn to such protrusions, similar to the action of lightning rods, any arcs generated during opening or closing of the contacts move along the protrusions 62, rather than remaining at the contacts 23 themselves The protrusions 62 thus provide added protection to the contacts 23 from damage due to arcing. The contacts 22 and
23 are surrounded by a shielding mesh 64 which is close to the contacts 23 and the protrusions 62 to provide further arcing protection The insulating plate 61 and its conducting shield 60 have indentations 63 to accommodate the contact protrusions 62 when the switch is in the open position and the contacts 23 are raised, as shown in Figures 3 and 4
When the switch 20 is tripped, the contact carrier 24 and contacts 23 are decoupled from the rest of the switching device 20; and they are the only parts that move to open the circuit. Since the current carrier 24 and contacts 23 have a small mass relative to the entire switching device 20, only a small force is required to drive the tripping, and, hence, the tripping process is very fast. As will be understood by persons skilled in the art, this significantly reduces the possibility of damage to the circuit due to arcing and due to the action of the abnormal current that initiated the tripping.
When the abnormal state of the circuit 21 is rectified, the switching device 20 must first be reset in order to return the contacts 23 to the closed position. This requires using the actuating mechanism 27 to drive the device into the normal open position. Referring now to Fig. 4, there is shown the switching device 20 in the open state resulting from the action of the actuating mechanism 27. In the example shown in the figure, when the mechanical handle 54 of the actuating mechanism 27 is moved to the right, the actuating mechanism 27 is driven upwards, further from the contacts 22 of the circuit 21 When the actuating mechanism 27 is so positioned, the switch contacts 23 are not in touching contact with circuit contacts 22, even when the latch 26 is in its closed position, as shown in the figure
When the actuating mechanism 27 is in its open position, the latch 26 is driven into its closed position by the latching spring 55 without encountering an opposing force from the biasing spring 29 on the contact carrier 24. There is also a shift in the position of the tripping lever 56 with respect to the latch 26 which allows the latch 26 to trip the tripping lever 56 in the reverse direction with small resistance from the tripping spring 57 so as to reengage the tripping lever, as shown in Figure 4 Once so reengaged, the latch 26 also engages the shelf 53 on the contact carrier 24 so that when the actuating mechanism 27 is driven to its closed position, as in Figure 2, the latch 26 will drive the contact carrier 24 down to bring the switch contacts 23 into touching contact with the circuit contacts 22, thereby closing the circuit 21.
In accordance with a preferred embodiment of the invention, tripping and latching mechanisms are mounted on the actuating mechanism 27 As will be understood by persons skilled in the art, this allows the tripping mechanism to function with no dependence on the position or state of the actuating mechanism 27. If the circuit 21 is closed and an overcurrent occurs, the switching device 20 will trip if the actuating mechanism 27 is closed or if it is in
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process of opening or closing. This enables the device to provide yet enhanced protection to any circuit to which it is connected.
Referring now to Fig. 5, there is shown an alternative embodiment of the present invention wherein actuating mechanism 67 is driven by an electrodynamic or electromagnetic driver, such as a stepping motor or a solenoid and wherein tripping mechanism 65 is mounted on the contact carrier 24. As shown in the figure, the downward closing force from the actuating mechanism 67 is transferred via the latching mechanism 68 to the latch 26 and therefrom to the tripping mechanism 65 and the contact carrier 24. In this embodiment of the invention, the upward force to open the switch is provided by the biasing spring 29 when the actuating mechanism 67 raises the latching mechanism 68 and the latch 26 out of engagement with the tripping mechanism 65 In an alternative embodiment of the present invention, the tripping mechanism 65 has an additional arm 69 to engage the latch 26 and the latching mechanism 68 to reset the latch 26 after it has been tripped An additional advantage in the application of electrodynamically or electromagnetically driven actuation is that it enables the switching device to be actuated by remote control
It will further be appreciated, by persons skilled in the art that the scope of the present invention is not limited by what has been specifically shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow