Power tool safety mechanism

• US 4,063,600 A
• Filed: 05/05/1976
• Issued: 12/20/1977
• Est. Priority Date: 05/05/1976
• Status: Expired due to Term

• Current Assignee: Casey S. Krzes
• Original Assignee: Casey S. Krzes
• Inventors: Krzes, Casey S.
• Primary Examiner(s): Hafer, Robert A.
• Application Number:
  US05/683,505
• Time in Patent Office: 594 Days
• Field of Search: 173/12, 173/18, 175/170, 200/153 T, 200/157, 307/94, 307/119, 310/50, 310/68 B, 310/68 E, 91/220
• US Class Current: 173/176
• CPC Class Codes: B23B 45/02 driven by electric power
• CPC Class Codes: H01H 2300/026 Application dead man switch: power must be interrupted on release of operating member
• CPC Class Codes: H01H 9/06 Casing of switch constituted by a handle serving a purpose other than the actuation of the switch, e.g. by the handle of a vacuum cleaner
• CPC Class Codes: Y10T 408/14 Responsive to condition of Tool or tool-drive

Abstract

In a portable motor driven tool such as a drill, a handle is connected to the housing in a manner permitting limited relative movement, in particular pivotal movement, between housing and handle. Biasing springs maintain the handle in a first position, and a normally-closed switch in series with the tool motor has an operator element engaging the handle. If the tool becomes stuck in a workpiece during operation, the sudden reverse force acting between the handle and housing overcomes the spring bias force causing relative movement between handle and housing to open the switch and break the motor electric circuit thereby preventing safety hazards and damage.

Claims

1. In a portable motor driven tool, a motor housing, a motor operatively disposed within said housing, an electrical circuit for said motor, a control switch in said circuit for controlling the supply of electrical power to said motor, a handle for grasping by the user to hold said tool during operation thereof, means connecting said handle to said housing in a manner permitting limited movement of said handle with respect to said housing between first and second positions, a normally-closed switch in said circuit and operatively mechanically connected to said handle and said housing such that said switch is closed when said handle is in said first position and said switch is open when said handle is in said second position, biasing means normally maintaining said handle in said first position, whereby in response to a force acting between said housing and said handle sufficient to overcome said biasing means, said handle is moved to said second position thereby opening said switch to open said electrical circuit for said motor.

2. Apparatus according to claim 1, further including a second handle fixed to said housing at a location generally opposite said movably connected handle.

3. Apparatus according to claim 1 further including stop means operatively connected to said housing and to said movable handle for limiting the amount of relative movement between said housing and said handle.

4. Apparatus according to claim 1, wherein said normally-closed switch is located in said housing and has a switch operator element operatively engaging said handle.

5. In a portable motor driven tool, a motor housing, a motor operatively disposed within said housing and having a rotary output drive shaft, an electrical circuit for said motor, means in said circuit for controlling the supply of electrical power to said motor, a handle for grasping by the user to hold said tool during operation thereof, means connecting said handle to said housing in a manner permitting limited movement of said handle with respect to said housing between first and second positions, said handle being pivotally connected to said housing about an axis disposed parallel to the axis of said motor shaft, a normally-closed switch in said circuit and operatively mechanically connected to said handle and said housing such that said switch is closed when said handle is in said first position and said switch is open when said handle is in said second position, biasing means normally maintaining said handle in said first position, whereby in response to a force acting between said housing and said handle sufficient to overcome said biasing means, said handle is moved to said second position thereby opening said switch to open said electrical circuit for said motor.

6. In a portable motor driven tool, a motor housing, a motor operatively disposed within said housing, an electrical circuit for said motor, means in said circuit for controlling the supply of electrical power to said motor, a handle for grasping by the user to hold said tool during operation thereof, means connecting said handle to said housing in a manner permitting limited movement of said handle with respect to said housing between first and second positions, a normally-closed switch in said circuit and operatively mechanically connected to said handle and said housing such that said switch is closed when said handle is in said first position and said switch is open when said handle is in said second position, biasing means normally maintaining said handle in said first position, said biasing means comprising spring means having one end operatively engaging said housing and another end operatively engaging said handle, whereby in response to a force acting between said housing and said handle sufficient to overcome said biasing means, said handle is moved to said second position thereby opening said switch to open said electrical circuit for said motor.

7. Apparatus according to claim 6, wherein said spring means exerts a biasing force at least equal to the weight of said tool.

8. In a portable motor driven tool, a motor housing, a motor operatively disposed within said housing, an electrical circuit for said motor, means in said circuit for controlling the supply of electrical power to said motor, a handle for grasping by the user to hold said tool during operation thereof, said handle being elongated having one end adjacent said housing, means pivotally connecting said handle at said end to said housing along an axis generally perpendicular to the longitudinal axis of said handle in a manner permitting limited movement of said handle with respect to said housing between first and second positions, a normally-closed switch in said circuit and operatively mechanically connected to said handle and said housing such that said switch is closed when said handle is in said first position and said switch is open when said handle is in said second position, biasing means normally maintaining said handle in said first position, said biasing means comprising spring means between said housing and said end of said handle and spaced from said pivotal connection, whereby in response to a force acting between said housing and said handle sufficient to overcome said biasing means, said handle is moved to said second position thereby opening said switch to open said electrical circuit for said motor.