1. Field of the Invention
The present invention relates to a safety switch that ensures the switch member to be pivoted automatically to “OFF” position under the current overload condition.
2. The Prior Arts
Each of U.S. Pat. Nos. 5,262,748, 4,167,720, 4,937,548, 5,223,813, 5,451,729 and 5,558,211 discloses a safety switch and each of these safety switches uses a bi-metallic plate to prevent from being burn under the current overload condition. The bi-metallic plate is deformed when an overloading occurs so as to separate the two contact points respectively located on the bi-metallic plate and one of the two terminals. Some inherent shortcomings for these conventional safety switches are found. There are too many parts involved in the safety switch and a longer period of time is required when assembling the switch, this increases the cost of the products. The parts might be arranged inaccurately and affects the deformation of the bi-metallic plate. Once the bi-metallic plate is deformed to cut off the circuit, because of the improper arrangement of the parts as mentioned above, the bi-metallic plate could deform to re-connect the two contact points to connect the circuit again when the temperature of the bi-metallic plate is reduced. The re-connect action might generate sparks which could cause dangerous events.
Therefore, it is desired to have a safety switch that allows the switch member to be switched to OFF position after the bi-metallic plate is deformed to cut off the circuit. The safety switch also can be installed at desired angle which does not affect the operation of the safety switch.
In accordance with an aspect of the present invention, there is provided a switch that comprises a body with a switch member pivotally engaged with the top opening of the body. A first terminal and a second terminal extend through a bottom of the body. An extension extends from an underside of a first end of the switch member, and a slot is defined through the extension. An operation member has a first end movably engaged with the slot of the extension. A contact plate is a bi-metallic plate and has a first end thereof connected to a second end of the operation member and a second end fixed to the first terminal. An opening is defined through the contact plate, and a tongue has a first end connected to an inside of the opening. A second end of the tongue is a free end and has a contact point which is removably in contact with the other contact point on the second terminal. The first end of the contact plate and the second end of the tongue are deformed in opposite direction under the current overload condition.
The main objective of the present invention is to provide a switch which provides a sufficient space for movement of the operation member to ensure the contact plate to be deformed completely to cut off the circuit.
Another objective of the present invention is to provide a switch, in which the switch member is automatically pivoted to “OFF” position under the current overload condition.
Yet another objective of the present invention is to provide a switch that includes less number of parts so as to have lower manufacturing cost.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.
Referring to the drawings and in particular to
An operation member 3 has a first end movably engaged with the slot 22 of the extension 21. In this embodiment, a horizontal rod 31 is connected to the first end of the operation member 3 and movably engaged with the horizontal space of the slot 22 between the OFF position as shown in
A contact plate 4 is made by bi-metallic material and has a first end thereof engaged with the engaging space in the second end of the operation member 3 and a second end of the contact plate 4 is fixed to the top bent portion of the first terminal 11. An opening is defined through the contact plate 4, a tongue 41 has a first end connected to an inside of the opening, and a second end of the tongue 41 is a free end. A second contact point 411 is fixed to the underside of the free end of the tongue 41 for being disengagably in contact with the first contact point 121 on the second terminal 12 when the circuit is cut off. The first end of the contact plate 4 and the second end of the tongue 41 are deformed in opposite direction under the current overload condition.
As shown in
As shown in
The specific shape of the slot 22 of the extension 21 allows the horizontal rod 31 of the operation member 3 to move in vertical direction along the vertical space of the slot 22 so that the contact plate 4 can be completely deformed and the switch member 2 can be pivoted to OFF position under the current overload condition.
While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.