Patent Application
20060197645
The present invention relates to a safety switch including a adjusting assembly to adjustably keep proper flexibility of the bi-metallic plate to ensure that the bi-metallic plate is deformed as desired when overload.
A conventional switch device, especially for those switches using bi-metallic plate to prevent from being burn when an overload is happened, generally includes a bi-metallic plate which is deformed when overload 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 switch devices are found. There are too many parts involved in the safety switch device and a longer period of time is required when assembling the switch device, 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. Because the inaccuracy of the deformation of the bi-metallic plate, the switch member does not set the “OFF” position after the bi-metallic plate is deformed to cut off the circuit.
Therefore, it is desired to have a device to ensure that the bi-metallic plate has proper flexibility and is deformed to accurately separate the two contact points and to pivot the switch member to “OFF” position.
In accordance with an aspect of the present invention, there is provided a switch device that comprises a body with a top opening for a switch member pivotably engaged therewith and two slots defined through an underside of the body so that a first terminal and a second terminal extend through the two slots. A first contact point is connected to the second terminal. A bi-metallic plate has an end fixed to the first terminal and a second contact point is connected to an underside of a second end of the bi-metallic plate. The second contact point is located above the first contact point. A recess is defined in an inside of the body and a hole is defined through a wall of the body and communicates with the recess. A link assembly includes a pull member and a push member, wherein an upper end of the pull member is pivotably connected to the switch member and a lower end of the pull member supports the underside of the second end of the bimetallic plate. An upper end of the push member is pivotably connected to the switch member and a lower end of the push member is in contact with the bi-metallic plate. A spring is biased between the push member and the body so as to provide a push force to the push member. An adjusting assembly which includes a board movably received in the recess and an adjusting member movably extends through the hole and is in contact with a first side of the board. A biasing member has a first end connected to the second end of the bi-metallic plate and a second end of the biasing member is engaged with a second side of the board.
The main object of the present invention is to provide a safety switch that uses a link assembly connected with the switch member to effectively control the bi-metallic plate to move between “ON” and “OFF” positions.
Another object of the present invention is to provide an adjusting assembly to connect a biasing member to a free end of the bi-metallic plate. The connection angle and force between the biasing member and the bi-metallic plate can be adjusted to ensure that the bi-metallic plate is deformed as desired when overload.
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
A link assembly 3 includes a pull member 31 and a push member 32. A first link 311 extends from an upper end of the pull member 13 and is pivotably engaged with the receiving hole 221 in the switch member 2 and a second link 312 extends from the lower end of the pull member 31. The second end of the bi-metallic plate 4 is supported on the second link 312. A third link extends from the upper end of the push member 32 and is pivotably engaged with the receiving hole 322, a bending portion 322 is formed on the lower end of the push member 32 and in contact with a top surface of the bi-metallic plate 4. The bi-metallic plate 4 includes a ridge 40 extending from the top thereof and the bending portion 322 of the push member 32 is in contact with one of two sides of the ridge 40. A boss 323 extends from a side of the push member 32 and one end of a spring 33 is mounted to the boss 323 and the other end of the spring 33 is engaged with an extension 16 of the body 1. The spring 33 can be a spiral spring which provides a push force to the push member 32 toward the pull member 31.
An adjusting assembly 5 includes a board 51 movably received in the recess 17 and an adjusting member 52 such as a bolt movably extends through the hole 170 and is in contact with a first side of the board 51. A biasing member 53 which is a U-shaped plate has a through hole 531 defined through a first end thereof and the second end of the bi-metallic plate 4 includes a tongue 42 which is engaged with the through hole 531. A second end of the biasing member 53 is engaged with a notch 511 defined in a second side of the board 51. The board 51 is moved axially in the recess 17 by operating the adjusting member 52 and a biasing force of the biasing member 53 relative to the bi-metallic plate 4 is adjusted.
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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.
