The present invention relates to a blade contact switching device according to the preamble of the independent claim 1. Herein a blade contact switching device is a device having a fixed contact and a movable contact adapted to pivot around a pivoting axis such that in the closed state of the switching device, projections of contact areas of the fixed contact and movable contact overlap on a plane perpendicular to the pivoting axis.
One of the problems associated with a blade contact switching device is that during a closing operation a mutual contact area between the fixed contact and the movable contact increases gradually as the movable contact pivots towards the position thereof corresponding to the closed state of the blade contact switching device. The gradual increase of the mutual contact area is a disadvantageous property for short circuit performance of the blade contact switching device since during a closing event a short circuit current may destroy the fixed contact and the movable contact before the mutual contact area reaches its maximum value.
An object of the present invention is to provide a switching device with improved short circuit performance.
The objects of the invention are achieved by a switching device which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea of providing a switching device with a spreader member that is adapted to move a movable contact member in a lateral direction away from a fixed contact member such that during a closing event of the switching device the spreader member allows the movable contact member to contact the fixed contact member only after the movable contact member has pivoted to a position in which the contact area of the movable contact member overlaps at least partially with the contact area of the fixed contact member, wherein the lateral direction is a direction parallel to the pivoting axis of the movable contact member.
An advantage of the switching device according to present invention is its improved short circuit performance. The mutual contact area between the fixed contact and the movable contact increases faster than in a corresponding known switching device, thereby enabling the switching device to withstand larger short circuit current in connection with the closing event.
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which
The switching device 2 comprises a frame 201, a load terminal 32 adapted to be connected to a load, a supply terminal 38 adapted to be connected to a power supply, a first fixed contact member 34, a second fixed contact member 39, a first movable contact member 4, a second movable contact member 9, a first spring system comprising two contact springs 17, an actuator roll 8 and a spreader member 6. The load terminal 32, the supply terminal 38, the first fixed contact member 34 and the second fixed contact member 39 are stationary members relative to the frame 201.
The first movable contact member 4 has a first contact arm 41 provided with a contact area, and a second contact arm 42 provided with a contact area. The first fixed contact member 34 has a first contact area 341 and a second contact area 342 facing an opposite direction than the first contact area 341.
The first contact arm 41, the second contact arm 42, the first fixed contact member 34, the load terminal 32, the second movable contact member 9, the second fixed contact member 39 and the supply terminal 38 are made of copper. In an alternative embodiment the first contact arm, the second contact arm, the first fixed contact member, the load terminal, the second movable contact member, the second fixed contact member and the supply terminal are made of some other material with high electrical conductivity.
The first movable contact member 4 is adapted to pivot relative to the frame 201 around a first pivoting axis 45 between a first position and a second position. The second movable contact member 9 is adapted to pivot relative to the frame 201 around a second pivoting axis 95 between a first position and a second position. The first pivoting axis 45 and the second pivoting axis 95 are parallel to each other, and spaced apart from each other.
The switching device 2 has an open state and a closed state. A first type switching event is a closing event of the switching device 2 transferring the switching device 2 from the open state to the closed state, or from OFF state to ON state. A second type switching event is an opening event of the switching device 2 transferring the switching device 2 from the closed state to the open state, or from ON state to OFF state.
In the open state of the switching device 2, the first movable contact member 4 is in the first position thereof, and the second movable contact member 9 is in the first position thereof.
In the closed state of the switching device 2, the first movable contact member 4 is in the second position thereof, and the second movable contact member 9 is in the second position thereof.
In the first position of the first movable contact member 4, a projection of the contact area of the first contact arm 41 is located at a distance from a projection of the first contact area 341 of the first fixed contact member 34 on a switch plane perpendicular to the first pivoting axis 45. In the second position the projection of the contact area of the first contact arm 41 overlaps the projection of the first contact area 341 of the first fixed contact member 34 on the switch plane, and the contact area of the first contact arm 41 is in electrically conductive connection with the first contact area 341 of the first fixed contact member 34, and the first contact arm 41 is in electrically conductive connection with the load terminal 32.
The second contact arm 42 is substantially a mirror image of the first contact arm 41 with respect to a plane perpendicular to the first pivoting axis 45 such that when the first movable contact member 4 is in the second position, the first and second contact areas of the first fixed contact member 34 are located between the contact areas of the first contact arm 41 and the second contact arm 42 in a lateral direction parallel to the first pivoting axis 45. Further, the first movable contact member 4 is symmetrical with respect to a plane perpendicular to the first pivoting axis 45.
In the first position thereof, the second movable contact member 9 is located at a distance from the second fixed contact member 39, and in the second position the second movable contact member 9 is in electrically conductive contact with the second fixed contact member 39, and the second movable contact member 9 is in electrically conductive connection with the supply terminal 38. The second movable contact member 9 is identical to the first movable contact member 4, and the second fixed contact member 39 is identical to the first fixed contact member 34.
The first contact arm 41 is in electrically conductive connection with the load terminal 32 in every position of the first movable contact member 4. The second movable contact member 9 is in electrically conductive connection with the supply terminal 38 in every position of the second movable contact member 9.
In the second position of the first movable contact member 4, the first spring system is adapted to press the contact area of the first contact arm 41 against the first contact area 341 of the first fixed contact member 34 in order to provide the electrically conductive connection between the contact area of the first contact arm 41 and the first contact area 341 of the first fixed contact member 34. Each contact spring 17 of the first spring system is a flat spring. One of the contact springs 17 is in contact with the first contact arm 41. The first spring system is adapted to press the first contact arm 41 and the second contact arm 42 towards each other in the lateral direction.
In an alternative embodiment the first spring system comprises the first contact arm made of flexible material. The flexible first contact arm can be used with or without a separate contact spring.
The spreader member 6 is adapted to provide a first intermediate position for the first movable contact member 4 in which the projection of the contact area of the first contact arm 41 overlaps partially with the projection of the first contact area 341 of the first fixed contact member 34 on the switch plane while the contact area of the first contact arm 41 is spaced apart from the first contact area 341 of the first fixed contact member 34 in the lateral direction. In the first intermediate position of the first movable contact member 4, a projection of the contact area of the second contact arm 42 overlaps partially with the projection of the second contact area 342 of the first fixed contact member 34 on the switch plane while the contact area of the second contact arm 42 is spaced apart from the second contact area 342 of the first fixed contact member 34 in the lateral direction. The first intermediate position is a position between the first position and the second position of the first movable contact member 4.
Herein, the projection of the contact area of the first contact arm overlaps partially with the projection of the first contact area of the first fixed contact member when the overlapping area is at least 30% of a maximum mutual contact area between the first contact area of the first fixed contact member and the contact area of the first contact arm. In an embodiment, the spreader member is adapted to provide a first intermediate position for the first movable contact member in which said overlapping area is 100% of a maximum mutual contact area between the first contact area of the first fixed contact member and the contact area of the first contact arm.
During the first type switching event, the spreader member 6 is adapted to defer contact between the first contact arm 41 and the first fixed contact member 34. The spreader member 6 defers a contact time of the first contact arm 41, and increases a contact angle of the first contact arm 41. The contact time of the first contact arm 41 is a time during the first type switching event when the first contact arm 41 makes contact with the first fixed contact member 34. The contact angle of the first contact arm 41 is an angle of the first contact arm 41 at which the first contact arm 41 makes contact with the first fixed contact member 34. The contact angle of the first contact arm 41 is measured around the first pivoting axis 45 from the first position of the first movable contact member 4 towards the second position of the first movable contact member 4. Therefore, the spreader member 6 is adapted to increase a mutual contact area between the first fixed contact member 34 and the first contact arm 41 at the contact time of the first contact arm 41. Further, due to the symmetry of the first movable contact member 4, the spreader member 6 is adapted to increase a mutual contact area between the first fixed contact member 34 and the second contact arm 42 at the contact time of the second contact arm 42. The contact time of the first contact arm 41 is the same as the contact time of the second contact arm 42, and consequently the spreader member 6 is adapted to increase a mutual contact area between the first fixed contact member 34 and the first movable contact member 4 at a contact time of the first movable contact member 4. The contact time of the first movable contact member 4 is a time during the first type switching event when the first movable contact member 4 makes contact with the first fixed contact member 34.
In the first type switching event, the actuator roll 8 is adapted to rotate relative to the frame 201 around a rotation axis 85 from a first position to a second position, wherein during the first type switching event the actuator roll 8 cooperates with the first movable contact member 4 through a linkage system for pivoting the first movable contact member 4 from the first position of the first movable contact member 4 to the second position of the first movable contact member 4. The linkage system comprises a first linkage arm 804 operationally connecting the actuator roll 8 and the first movable contact member 4, and a second linkage arm 809 operationally connecting the actuator roll 8 and the second movable contact member 9. In the open state of the switching device 2 the actuator roll 8 is in the first position, and in the closed state of the switching device 2 the actuator roll 8 is in the second position.
During the first type switching event the first movable contact member 4 and the second movable contact member 9 pivot in opposite directions. Referring to
The rotation axis 85 of the actuator roll 8 is parallel to the first pivoting axis 45 of the first movable contact member 4, and is spaced apart from it. The rotation axis 85 of the actuator roll 8 is located between the first pivoting axis 45 of the first movable contact member 4 and the second pivoting axis 95 of the second movable contact member 9 in a longitudinal direction of the switching device 2 perpendicular to the lateral direction. In
In the second type switching event, the actuator roll 8 is adapted to rotate relative to the frame 201 around the rotation axis 85 from the second position to the first position. Rotation of the actuator roll 8 during the second type switching event is a reverse event compared to rotation of the actuator roll 8 during the first type switching event. During the second type switching event the first movable contact member 4 pivots from the second position of the first movable contact member 4 to the first position of the first movable contact member 4, and the second movable contact member 9 pivots from the second position of the second movable contact member 9 to the first position of the second movable contact member 9.
The spreader member 6 is symmetrical with respect to a plane perpendicular to the first pivoting axis 45. The spreader member 6 has a tapered section 62 adapted to provide a slope for the first contact arm 41 such that during the second type switching event the tapered section 62 cooperates with the first contact arm 41 for transferring the first contact arm 41 in a lateral direction away from the first fixed contact member 34. The tapered section 62 of the spreader member 6 is also adapted to provide a slope for the second contact arm 42 such that during the second type switching event the tapered section 62 cooperates with the second contact arm 42 for transferring the second contact arm 42 in a lateral direction away from the first fixed contact member 34. The tapered section 62 is located at a distance from the rotation axis 85.
A cross section of the tapered section 62 has a shape of a triangle. The point of the tapered section 62 is sharp. The point of the tapered section 62 is a free end of the spreader member 6. The widest portion of the spreader member 6 is located at a base of the tapered section 62. In the first intermediate position of the first movable contact member 4, the widest portion of the spreader member 6 is in contact with the first contact arm 41 and the second contact arm 42. The width direction of the spreader member 6 is parallel to the lateral direction.
The spreader member 6 has a supported end connected to the actuator roll 8. The spreader member 6 is movable relative to the frame 201 between a first position and a second position such that when the first movable contact member 4 is in the first position of the first movable contact member 4, the spreader member 6 is in the first position of the spreader member 6, and when the first movable contact member 4 is in the second position of the first movable contact member 4, the spreader member 6 is in the second position of the spreader member 6. During the first type switching event the spreader member 6 and the contact areas of the first contact arm 41 and second contact arm 42 move in opposite directions in the longitudinal direction. Said opposite movement of the spreader member 6 and the contact areas of the first contact arm 41 and second contact arm 42 further improves short circuit performance of the switching device 2.
The spreader member 6 is an integral part of the actuator roll 8. The spreader member 6 is stationary relative to the actuator roll 8. The spreader member 6 is made of the same plastic material as the actuator roll 8. In an alternative embodiment, the spreader member is made of an electrically non-conductive material different than the material of the actuator roll. In a further alternative embodiment, the spreader member is made of material whose hardness is lower than hardness of material of the first contact arm.
Material of the spreader member 6 has high heat endurance such that the spreader member 6 does not melt, deform or catch fire even in situations where the spreader member 6 comes into contact with the first contact arm 41 after the switching device 2 has conducted a maximum current thereof for a long period of time. In an embodiment the spreader member is made of a material whose hardness in 250° C. temperature is at least 80% of the maximum hardness of the material.
In an alternative embodiment the spreader member is a stationary member relative to the frame. In embodiments where the spreader member is not an integral part of the actuator roll, the spreader member may be made of an electrically conductive material, for example the same material as the first contact arm.
The switching device 2 of
In an alternative embodiment the first movable contact member only has one contact arm. In said alternative embodiment the spreader member may be an asymmetrical member.
The switching device 2 shown in
During the first type switching event the second movable contact member 9 makes contact with the second fixed contact member 39 before the first movable contact member 4 makes contact with the first fixed contact member 34.
It will be obvious to a person skilled in the art that the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
Number | Date | Country | Kind |
---|---|---|---|
19170115.0 | Apr 2019 | EP | regional |