Patent Publication Number: US-7583175-B2

Title: Safety switch

Description:
BACKGROUND OF THE INVENTION 
   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 and the switch can be installed in any desired angle. 
   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 disclosed 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 product. The parts might be arranged inaccurately and affect 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. 
   SUMMARY OF THE INVENTION 
   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. A positioning member has a first end pivotally connected to an inside of the body. An operation member has a first end movably engaged with the slot of the extension, and a second end of the positioning member biases the first end of the operation member toward the first end of the switch member. 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, which can be installed in any desired angle by using the positioning member. 
   Yet 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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view to show a switch in accordance with the present invention; 
       FIG. 2  is a side view to show the “OFF” status of the switch in accordance with the present invention; 
       FIG. 3  is a side view to show the “ON” status of the switch in accordance with the present invention; 
       FIG. 4  is an enlarged view to show that a distance ΔS 1  is provided for the movement of the first end of the operation member in the slot; 
       FIG. 5  shows the first end of the operation member moves downward along the vertical space of the slot under the current overload condition; and 
       FIG. 6  is an enlarged view to show that a distance ΔS 2  is provided for the movement of the first end of the switch member when the switch member is pivoted to the OFF position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the drawings and in particular to  FIGS. 1 and 2 , a switch in accordance with the present invention comprises a body  1  with a top opening  10 , and a switch member  2  pivotally engaged with the top opening  10  of the body  1 . An extension  21  extends from an underside of a first end of the switch member  2 , and a substantially inverted L-shaped slot  22  is defined through the extension  21 . The slot  22  includes a horizontal space and a vertical space. The switch member  2  is pivoted about the pivots on two sides of the mediate portion thereof. A torsion spring  13  is connected to the inside of the body  1 , and includes a coil portion and two legs extended from the coil portion. The coil portion is mounted to a first rod  14  extending from the inside of the body  1  and one of the two legs is biased against a second rod  15  extending from the inside of the body  1 . The other one of the two legs contacts the underside of a second end of the switch member  2 . By the torsion spring  13 , the switch member  2  is kept to be at its OFF position where the first end of the switch member  2  is located at lower position and the second end is located at higher position as shown in  FIG. 2 . 
   A first terminal  11  and a second terminal  12  extend through a bottom of the body  1 , and a first contact point  121  is connected to a top bent portion of the second terminal  12 . A positioning member  17  is made by resilient material and includes a first end pivotally connected to an inside of the body  1 . The positioning member  17  is a substantially L-shaped member, which includes a horizontal portion  171  at the first end of the positioning member  17  and a vertical portion  172  connected to an end of the horizontal portion  171 . A hook is defined in a distal end of the horizontal portion  171  which extends through a through hole  16  in the body  1  and the hook is hooked with the through hole  16 . 
   An operation member  3  has a first end movably engaged with the slot  22  of the extension  21  and a second end of the positioning member  17  biases the first end of the operation member  3  toward the first end of the switch member  2 . 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  FIG. 2  and the ON position as shown in  FIG. 3 . A hole is defined through the operation member  3  and a stub  34  extends from an inside of the hole. A lip  33  extends transversely from the second end of the operation member  3 . An engaging space  32  is defined between the stub  34  and the lip  32 . The width of the engaging space  32  is slightly larger than the thickness of the contact plate  4 . 
   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  FIG. 2 , when the first end is pushed downward, the operation member  3  is pushed downward so as to move the first end of the contact plate  4 . The free end of the tongue  41  is then bent upward to separate the first contact point  121  and second contact point  411  to cut off the circuit. In the OFF position, the horizontal rod  31  of the first end of the operation member  3  is located at the right inner end of the horizontal space of the slot  22 . As shown in  FIG. 3 , when pushing the second end of the switch member  2  downward, the first end of the contact plate  4  is lofted along with the movement of the operation member  3 , the free end of the tongue  41  is then bent downward to let the first contact point  121  and second contact point  411  be in contact with each other to connect the circuit. In the ON position, the horizontal rod  31  of the first end of the operation member  3  is located at the left inner end of the horizontal space of the slot  22 . As shown in  FIG. 4 , when the switch member  2  is in ON position, there is a distance ΔS 1  provided for the movement of the first end of the operation member in the slot  22  if an overloading occurs. 
   As shown in  FIGS. 5 and 6 , under the current overload condition, the tongue  41  of the contact plate  4  deforms upward to separate the first contact point  121  and second contact point  411  to cut off the circuit. The first end of the contact plate  4  then is deformed downward to pull the operation member  3  downward, and the horizontal rod  31  of the operation member  3  moves along the vertical space of the slot the distance ΔS 1 . Therefore, the second end of the switch member  2  is pushed upward by the torsion spring  13 , and the first end of the switch member  2  moves downward a distance ΔS 2  so that the switch member  2  is pivoted to OFF position as shown in  FIG. 2 . In the meanwhile, the horizontal rod  31  on the first end of the operation member  3  moves along the vertical space to the right inner end of the horizontal space of the slot  22 . 
   The positioning member  17  ensures that the operation member  3  is not affected by gravity so that the operation member  3  functions normally at any angle. 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.