Safety devices for electric circular saws

• US 3,922,785 A
• Filed: 11/12/1974
• Issued: 12/02/1975
• Est. Priority Date: 11/15/1973
• Status: Expired due to Term

• Current Assignee: Fusao Fushiya
• Original Assignee: Fusao Fushiya
• Inventors: Fushiya, Fusao
• Primary Examiner(s): Smith, Al Lawrence
• Assistant Examiner(s): Peters, J. C.
• Application Number:
  US05/523,100
• Time in Patent Office: 385 Days
• Field of Search: 30/166,276,286,382,390,391 83/397,478,860
• US Class Current: 30/391
• CPC Class Codes: B23Q 11/08 Protective coverings for parts of machine tools; Splash guards
• CPC Class Codes: B27G 19/04 for manually-operated power-driven circular saws
• CPC Class Codes: Y10T 83/7734 With guard for tool

Abstract

An improved safety device for an electrically driven hand operated circular saw is disclosed. The device comprises an auxiliary switch connected in series to a main switch in an electric circuit between a power source and a motor for driving a saw blade, and a mechanism operationally connecting the auxiliary switch with a rotatable safety cover. According to one embodiment, the mechanism comprises a shaft and a lever secured to each end of the shaft. One of the levers is maintained in frictional contact with the safety cover for rotation therewith to simultaneously cause rotation of the shaft and the other lever. The other lever is associated with the auxiliary switch to break circuit continuity therethrough to discontinue rotation of the saw blade upon rotation of the safety cover in the direction in which it conceals the saw blade.

Claims

1. In combination with a safety device for an electrically driven hand operated circular saw, wherein a safety cover for a circular saw blade is provided rotatably in one direction to expose said saw blade and in the opposite direction to conceal said saw blade, and wherein means is provided for urging said safety cover in said opposite direction, the improvement which comprises:

an auxiliary switch connected in series to a main switch in an electric circuit between a power source and a motor for driving said saw blade; and

means operationally associated with said safety cover and said auxiliary switch for maintaining said auxiliary switch in its operative position during rotation of said safety cover in said one direction, but turning said auxiliary switch into its inoperative position upon rotation of said safety cover in said opposite direction.

2. The invention of claim 1 wherein said auxiliary switch is a limit switch adapted to turn into said operative position when engaged by said last named means upon said rotation of said safety cover in said one direction.

3. The invention of claim 1 wherein said auxiliary switch is a limit switch adapted to turn into said operative position when said last named means is disengaged from said limit switch upon said rotation of said safety cover in said one direction.

4. The invention of claim 2 wherein said last named means comprises:

a shaft supported by a gear housing on said saw rotatably about its own axis;

a first lever secured at one end to one end of said shaft for rotation therewith;

a second lever secured at one end to the other end of said shaft for rotation with said safety cover in a direction opposite thereto, said second lever extending in a generally diametrically oPposite direction from said first lever with respect to said shaft;

a member of elastic material secured to the other end of said second lever and maintained in frictional contact with said safety cover to cause said rotation of said second lever within a predetermined angle to thereby rotate said shaft and said first lever; and

means provided in a saw blade housing for restricting said rotation of said second lever within said predetermined angle;

the other end of said first lever being engageable with said limit switch upon rotation in one direction and disengageable therefrom upon rotation in the opposite direction.

5. The invention of claim 4 wherein said second lever is made of elastic material and maintains said frictional contact between said elastic member and said safety cover.

6. The invention of claim 4 wherein said restricting means comprises a pair of stoppers between which said second lever is interposed, said second lever being adapted to abut against one of said stoppers upon said rotation of said first lever in said one direction and the other stopper upon said rotation of said first lever in said opposite direction.

7. The invention of claim 3 wherein said last named means comprises:

a shaft supported by a saw blade housing rotatably about its own axis;

a pin secured at one end to one end of said shaft for rotation therewith;

a lever secured in its mid-portion to the other end of said shaft for rotation with said safety cover in a direction opposite thereto, said lever being generally parallel to said pin and having one end extending in a generally diametrically opposite direction from said pin with respect to said shaft;

a member of elastic material secured to said one end of said lever and maintained in frictional contact with said safety cover to cause said rotation of said lever within a predetermined angle to thereby rotate said shaft and said pin; and

means provided in said saw blade housing for restricting said rotation of said lever within said predetermined angle;

the other end of said pin being disengageable from said limit switch upon rotation in one direction and engageable therewith upon rotation in the opposite direction.

8. The invention of claim 7 wherein said elastic member is a rubber pin, and wherein said one end of said lever includes a substantially cylindrical, coaxially extending portion, said rubber pin being secured in said cylindrical portion and projecting therefrom at one end, said one end of said rubber pin being maintained in frictional contact with said safety cover.

9. The invention of claim 7 wherein said restricting means comprises a stopper provided in said saw blade housing and cooperating with a bottom inner wall portion of a handle on said saw to restrict said rotation of said lever within said predetermined angle, the other end of said lever being adapted to abut against said stopper upon said rotation of said pin in said opposite direction, and said other end of said pin being adapted to abut against said bottom inner wall portion upon said rotation of said pin in said one direction.

10. The invention of claim 9 wherein said lever is generally L-shaped and includes a projection on said other end thereof for abutment against said stopper.