The present invention relates generally to a switch, and in particular to a switch having an overload protection mechanism for operation safety.
A switch is operable between an ON (connected) state and an OFF (disconnected) state for control of power supply or electrical signal transmission. For a power switch, overheating and burning caused by overload resulting from undesired shorting is one of the major concerns of operation safety. Some switches available in the market are provided with safety mechanism that automatically cuts off power supplied therethrough in order to eliminate the potential risk of overheating and burning. Such switches, however, have complicated structures, making costs high and manufacture difficult.
Another concern of the safety mechanism of the power switch is the operation reliability thereof. Operation reliability of a safety mechanism may deteriorate due to aging of the parts thereof. Such reliability problem often causes failure of timely cutting off power supplied to the switch when the switch is overloaded, leading to disasters.
It is thus desirable to have a switch structure that is simple in structure but is reliable and possesses operation safety feature.
An object of the present invention is to provide a switch having a simple structure while capable of operation safety.
Another object of the present invention is to provide a switch of low costs while having overload protection.
A further object of the present invention is to provide a switch that is easy to manufacture.
Yet a further object of the present invention is to provide a switch that is reliable in cutting off power supply therethrough in an overload condition.
To achieve the above objects, in accordance with the present invention, there is provided a switch comprising a casing and first and second conductive blades. A conductive strip made of a material that bends when subject to a temperature rise is fixed to the first blade and has a free end. A conductive plate is arranged inside the casing and in electrical connection with the second blade and movable between an engaged position where the conductive plate engages the conductive strip to form an electrical connection between the first and second blades and a disengaged position where the conductive plate disengages from the conductive strip to electrically disconnect the second blade from the first blade. When an overload occurs, an excessive current flows through the conductive strip, causing the strip to bend from a normal operation condition to a breaking condition that separates the conductive strip from the conductive plate. A link is coupled to the conductive plate and defines an elongated slot receiving the free end of the conductive strip therein. The elongated slot allows the conductive plate to move between the engaged and disengaged positions without causing movement of the conductive strip while when the condutive strip is in the breaking condition, the link drivingly couples the conductive strip to the conductive plate for returning the conductive strip back to the normal operation condition. A leaf spring is pivoted between the casing and the conductive strip to retain the conductive strip in the breaking condition until the conductive strip is driven by the link back to the normal operation condition.
The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:
With reference to the drawings and in particular to
A driver assembly 22 is formed on an underside of the button 2 and extends into the interior space of the casing 1. The driver assembly 22 comprises a cylinder 221 extending from the underside of the button 2 inside which a cap 23 is partially and movably received. A biasing element 231, such as a helical spring, is mounted between the cylinder 221 and the cap 23 for biasing the cap 23 away from the cylinder 221. The helical spring 231 is received and retained in both the cylinder 221 and the cap 23.
Two slots 12, 13 are defined in a bottom (not labeled) of the casing 1. First and second conductive blades 14, 15 are fit and fixed in the slots 12, 13 and having tails (not labeled) extending beyond the bottom of the casing 1 for external connection. An opening 151 is defined in the second blade 15. A conductive strip 4 made of a conductive material, such as an alloy or a bimetal, that bends when subject to heat (and thus having a temperature rise) is arranged inside the casing 1 and has an end attached to the first blade 14 and a second, free end extending through the opening 151, forming a cantilever beam. The opening 151 is large enough to accommodate the bending and deformation of the conductive strip 4 without any physical engagement therebetween.
The second blade 15 defines a notch 152 in a top edge (not labeled) thereof. A seesaw plate 3 made of a conductive material is arranged inside the casing 1 and has a concave configuration and forms a bottom projection (not labeled) fit in the notch 152 of the second blade 15 whereby the seesaw plate 3 seesaws about the top edge of the second blade 15. The bottom projection of the seesaw plate 3 is formed by pressing the plate 3 that forms a recess 31 on a top side thereof and the recessed portion of the plate 3 forms the projection. A hole 32 is defined at a first end of the seesaw plate 3 to which a first contact 33 is received and fixed. A second contact 42 is mounted to a hole 41 defined in the conductive strip 4 to correspond to the first contact 33.
The cap 23 of the button 2 engages the top side of the seesaw plate 3 and is slidable along the seesaw plate 3 to seesaw the seesaw plate 3. When the button 2 is rotated to the first position (the ON condition, FIG. 3), the cap 23 is moved to the first end of the seesaw plate 3 close to the first contact 33 whereby the seesaw plate 3 is moved to an engaged position where the first contact 33 is brought into engagement with the second contact 42 of the conductive strip 4. Thus, an electrical connection between the first and second blades 14, 15, through the conductive strip 4, the second and first contacts 42, 33 and the seesaw plate 3, is formed.
When the button 2 is rotated to the second position (the OFF condition, FIG. 2), the cap 23 is moved to a second end of the seesaw plate 3 away from the first contact 33 whereby the seesaw plate 3 is moved to a disengaged position by rotation about the notch 152 of the second blade 15 to separate the first contact 33 from the second contact 42. Thus, the electrical connection between the first and second blades 14, 15 is broken.
In sliding along the seesaw plate 3 between the first and second ends thereof, the cap 23 is forced toward the button 2 when the cap 23 passes the edge of the second blade 15 by deforming the biasing element 231. If desired, the cap 23 may be partially received in the recess 31 defined in the top side of the seesaw plate 3 to be guided thereby.
The rotation of the button 2 between OFF and ON conditions causes the seesaw plate 3 to seesaw between the disengaged and engaged positions. When the seesaw plate 3 is moved to the disengaged position, to ensure correctly positioning of the seesaw plate 3 and to prevent undesired engagement between the seesaw plate 3 and the first blade 14 (noting that the seesaw plate 3 is always in engagement with the second blade 15), a partition 16 is formed inside the casing 1 and extending above the conductive strip 4 and the first blade 14. Thus, when the seesaw plate 3 is moved to the disengaged position, the second end of the seesaw plate 3 is stopped by the partition 16 thereby ensuring the correct positioning of the seesaw plate 3 at the disengaged position.
Similarly, when the seesaw plate 3 is moved to the engaged position, the casing 1 forms a first stop 17 located between the first end of the seesaw plate 3 and the conductive strip 4. When the first contact 33 engages the second contact 42, the first stop 17 engages the seesaw plate 3 and thus fixing the seesaw plate 3 at the engaged position. Overturning of the seesaw plate 3 is prevented. An additional second stop 18 may be formed inside the casing 1 spaced from and substantially opposite to the partition 16 for engaging the second end of the seesaw plate 3 and thus further fixing the seesaw plate 3 at the engaged position.
Also referring to
Preferably, one or more stops are formed inside the casing for preventing over-bending of the conductive strip 4 when the conductive strip 4 is subject to a temperature rise. This is to ensure that the conductive strip 4 does not contact the second blade 15 even when it is subject to a significant temperature rise.
Referring back to FIG. 1 and further referring to
The dimension of the second slot 52 of the link 5 and the dimension of the opening 151 of the second blade 15 are sized so that when an overload occurs during an ON condition with electrical current supplied through the conductive strip 4, the conductive strip 4 bends away from the seesaw plate 3, the longitudinal dimension of the second slot 52 allows the free end of the conductive strip 4 to move away from the first end of the seesaw plate 3. The movement of the free end of the conductive strip 4 is stopped by the lower end of the second slot 52 of the link 5 and is not allowed to contact the opening 151 of the second blade 15.
To return to the normal operation from the breaking condition, the button 2 is moved to the OFF condition. The seesaw plate 3 is moved to separate the first end thereof from the first stop 17. The free end of the conductive strip 4 is forced to move in unison with the seesaw plate 3 by means of the link 5. Thus, the switch is back to the OFF condition and is ready for next actuation. The button 2 may then be moved to the ON condition to engage the first contact 33 with the second contact 42 for resuming electrical connection between the first and second blades 14, 15.
The link 5 ensures that the free end of the conductive strip 4 can be brought back to its unbent position for next actuation of the switch. Even when the mechanical property of the conductive strip 4 deteriorate due to aging or other reasons, the link 5 still provide means for returning the conductive strip 4 back to its unbent position.
A U-shaped leaf spring 6 has opposite legs of which a first one is pivotally connected to the casing 1 and a second one pivotally coupled to the free end of the conductive strip 4. The second leg of the leaf spring 6 defines an opening 62 and the free end of the conductive strip 4 forms an extension having barbed end 43. The extension 43 is received in the opening 62, forming the pivotal coupling between the conductive strip 4 and the leaf spring 6. The pivotal connection of the first leg of the leaf spring 6 to the casing 1 allows the second leg of the leaf spring 6 to move with the free end of the conductive strip 4 when the conductive strip 4 is moved to the breaking condition due to overload.
The leaf spring 6 is preloaded and applies a force to the free end of the conductive strip 4 in a direction pointing from the pivotal connection of the first leg to the pivotal coupling of the second leg. When the conductive strip 4 is in a normal operation condition, the pivotal coupling of the second leg is located above the pivotal connection of the first leg. The spring force of the leaf spring 6 acts in such a direction to retain the conductive strip 4 in an upward concave condition which leads to the normal operation of the switch. When an overload occurs, the conductive strip 4 bends to a downward concave condition. The movement of the second leg of the leaf spring 6 with the conductive strip 4 moves the pivotal coupling of the second leg to be below the pivotal connection of the first leg whereby the spring force of the leaf spring 6 acts on the free end of the conductive strip 4 in such a direction to retain the conductive strip 4 in the breaking condition.
The spring force of the leaf spring 6 is overcome by a driving force provided by the movement of the link 5 to the conductive strip 4. Thus, the conductive strip 4 can be moved back to the normal operation condition against the leaf spring 6. The leaf spring 6 ensures operation reliability of the conductive strip 4 in both the normal operation condition and the breaking condition.
A bolt 101 is threadingly received in an inner-threaded hole 10 defined in the housing 1. A circumferential groove 1011, preferably having a V-shaped cross section, is defined in a free end of the bolt 101. The U-shaped leaf spring 6 has a flange 61 extending from the first leg of the spring 6 and receivingly engaging the groove 1011 of the bolt 101 for pivotally connecting the first leg of the leaf spring 6 to the casing 1. The pivotal connection of the first leg of the leaf spring 6 inside the casing 1 is position-adjustable by turning the bolt 101 to change relative position of the bolt 101 with respect to the casing 1.
A pushbutton 2′ is movably received in the interior space of the casing 1 through the side opening 112. A guide block 25 having a polygonal configuration is formed on a top side of the pushbutton 2′ defining a multi-section channel 24 surrounding the block 25. The channel 24 forms a closed loop path or route having stop points A and B. The second end section of the bar 191 is movably received in the channel 24 and is guided to move along the route. The pushbutton 2′ is linearly movable with respect to the casing 1 between an outer position (
A driver assembly 22 is formed on an underside of the pushbutton 2′ and extends into the interior space of the casing 1. The driver assembly 22 comprises a cylinder 221 extending from the underside of the pushbutton 2′ inside which a cap 23 is movably received. A biasing element 231, such as a helical spring, is mounted between the cylinder 221 and the cap 23 for biasing the cap 23 away from the cylinder 221. The helical spring 231 is received and retained in both the cylinder 221 and the cap 23.
Two slots 12, 13 are defined in a bottom (not labeled) of the casing 1. First and second conductive plates 14, 15 are fit and fixed in the slots 12, 13 and having tails (not labeled) extending beyond the bottom of the casing 1 for external connection. An opening 151 is defined in the second blade 15. A conductive strip 4 made of a conductive material, such as an alloy and a bimetal, that bends when subject to heat and thus having a temperature rise has an end attached to the first blade 14 and a second, free end extending through the opening 151 forming a cantilever beam. The opening 151 is large enough to accommodate the deformation of the conductive strip 4 without any physical engagement therebetween.
The second blade 15 defines a notch 152 at a top edge (not labeled) thereof. A seesaw plate 3 made of a conductive material has a concave configuration and forms a bottom projection (not labeled) fit in the notch 152 of the second blade 15 whereby the seesaw plate 3 seesaws about the top edge of the second blade 15. The bottom projection of the seesaw plate 3 is formed by pressing the plate 3, which forms a recess 31 on a top side thereof, and the recessed portion of the plate 3 forms the projection. A hole 32 is defined at a first end of the seesaw plate 3 to which a first contact 33 is received and fixed. A second contact 42 is mounted to a hole 41 defined in the conductive strip 4 to correspond to the first contact 33.
The cap 23 of the button 2 engages the top side of the seesaw plate 3 and is slidable along the seesaw plate 3 to seesaw the seesaw plate 3. When the pushbutton 2′ is moved to the inner position (the ON condition, FIG. 9), the cap 23 is moved to the first end of the seesaw plate 3 close to the first contact 33 whereby the seesaw plate 3 is driven to an engaged position where the first contact 33 is brought into engagement with the second contact 42 of the conductive strip 4. Thus, an electrical connection between the first and second blades 14, 15, through the conductive strip 4, the second and first contacts 42, 33 and the seesaw plate 3, is formed.
When the pushbutton 2′ is moved to the outer position (the OFF condition, FIG. 8). The cap 23 is moved to a second end of the seesaw plate 3 away from the first contact 33 whereby the seesaw plate 3 is driven to a disengaged position by rotation about the notch 152 of the second blade 15 to separate the first contact 33 from the second contact 42. Thus, the electrical connection between the first and second blades 14, 15 is broken.
In sliding along the seesaw plate 3 between the first and second ends thereof, the cap 23 is forced toward the pushbutton 2′ when the cap 23 passes the edge of the second blade 15 by deforming the biasing element 231. If desired, the cap 23 may be partially received in the recess 31 defined in the top side of the seesaw plate 3 to be guided thereby.
The movement of the pushbutton 2′ between the outer and inner positions (the OFF and ON conditions) causes the seesaw plate 3 to seesaw between the disengaged and engaged positions. When the seesaw plate 3 is moved to the disengaged position, to ensure correctly positioning of the seesaw plate 3 and to prevent undesired engagement between the seesaw plate 3 and the first blade 14 (noting that the seesaw plate 3 is always in engagement with the second blade 15), a partition 16 is formed inside the casing 1 and extending above the conductive strip 4 and the first blade 14. Thus, when the seesaw plate 3 is moved to the disengaged position, the second end of the seesaw plate 3 is stopped by the partition 16 thereby ensuring the correct positioning of the seesaw plate 3 at the disengaged position.
Similarly, when the seesaw plate 3 is moved to the engaged position, the casing 1 forms a stop 17 located between the seesaw plate 3 and the conductive strip 4. When the first contact 33 engages the second contact 42, the stop 17 engages the seesaw plate 3 and thus fixing the seesaw plate 3 at the engaged position. Overturning of the seesaw plate 3 is prevented.
Also referring to
Referring back to
The dimension of the second slot 52 of the link 5 and the dimension of the opening 151 of the second blade 15 are sized so that when an overload occurs during an ON condition with electrical current supplied through the conductive strip 4, the conductive strip 4 bends away from the seesaw plate 3, the longitudinal dimension of the second slot 52 allows the free end of the conductive strip 4 to move away from the first end of the seesaw plate 3. The movement of the free end of the conductive strip 4 is stopped by the lower end of the second slot 52 of the link 5 and is not allowed to contact the opening 151 of the second blade 15.
To return to the normal operation from the breaking condition, the pushbutton 2′ is moved to the outer position (the OFF condition). The seesaw plate 3 is moved to separate the first end thereof from the first stop 17. The free end of the conductive strip 4 is forced to move in unison with the seesaw plate 3 by means of the link 5. Thus, the switch is back to the OFF condition and is ready for next actuation. The pushbutton 2′ may then be moved to the inner position (the ON condition) to engage the first contact 33 with the second contact 42 for resuming electrical connection between the first and second blades 14, 15.
A U-shaped leaf spring 6 has opposite legs of which a first one is pivotally connected to the casing 1 and a second one pivotally coupled to the free end of the conductive strip 4. The second leg of the leaf spring 6 defines an opening 62 and the free end of the conductive strip 4 forms an extension having barbed end 43. The extension 43 is received in the opening 62, forming the pivotal coupling between the conductive strip 4 and the leaf spring 6. The pivotal connection of the first leg of the leaf spring 6 to the casing 1 allows the second leg of the leaf spring 6 to move with the free end of the conductive strip 4 when the conductive strip 4 is moved to the breaking condition due to overload.
The leaf spring 6 is preloaded and applies a force to the free end of the conductive strip 4 in a direction pointing from the pivotal connection of the first leg to the pivotal coupling of the second leg. When the conductive strip 4 is in a normal operation condition, the pivotal coupling of the second leg is located above the pivotal connection of the first leg. The spring force of the leaf spring 6 acts in such a direction to retain the conductive strip 4 in the upward concave condition which leads to the normal operation of the switch. When an overload occurs, the conductive strip 4 bends to the downward concave condition. The movement of the second leg of the leaf spring 6 with the conductive strip 4 moves the pivotal coupling of the second leg to be below the pivotal connection of the first leg whereby the spring force of the leaf spring 6 acts on the free end of the conductive strip 4 in such a direction to retain the conductive strip 4 in the breaking condition.
The spring force of the leaf spring 6 is overcome by a driving force provided by the movement of the link 5 to the conductive strip 4. Thus, the conductive strip 4 can be moved back to the normal operation condition against the leaf spring 6. The leaf spring 6 ensures operation reliability of the conductive strip 4 in both the normal operation condition and the breaking condition.
A bolt 101 is threadingly received in an inner-threaded hole 10 defined in the housing 1. A circumferential groove 1011, preferably having a V-shaped cross section, is defined in a free end of the bolt 101. The U-shaped leaf spring 6 has a flange 61 extending from the first leg of the spring 6 and receivingly engaging the groove 1011 of the bolt 101 for pivotally connecting the first leg of the leaf spring 6 to the casing 1. The pivotal connection of the first leg of the leaf spring 6 inside the casing 1 is position-adjustable by turning the bolt 101 to change relative position of the bolt 101 with respect to the casing 1.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
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Number | Date | Country | |
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20040037020 A1 | Feb 2004 | US |