US 4,556,803 AGranted

Trigger switch circuit for solenoid-actuated electric hand tool

AssigneeElectro-Matic Staplers, Inc.

InventorHans Weigert

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Abstract

An electrically powered hand tool, such as a staple gun, can employ an electrical driver, such as a solenoid, which is actuated by a trigger circuit in response to depression of a trigger on the handle of the device. The trigger circuit can include a circuit board dimensioned to fit into the handle of the staple gun, and having AC input leads. A circuit formed of conventional electronic components delivers a burst of power to output leads which are in turn connected to a driver solenoid. This circuit is actuated to deliver the power burst by opening of a switch formed of two switch members: one switch member has a first flexible resilient conductive leaf formed, e.g., of an alloy of copper, extending beyond an edge of the board; the other member has a flexible resilient leaf with a bent-in pointed end contacting a side of the first blade. These blades are biased against each other to form a normally-closed switch. When the first blade is moved in one direction, the switch opens. When the first blade returns in the other direction to close the switch, the pointed end of the other resilient leaf of blade scratches off corrosion at the contact area of the two members. This permits low current (1 ma) to be used as a control current through the switch.

Claims10

Dependent claims

In a trigger switch circuit used in an electric hand tool of the type having a casing, a manually actuated trigger, and electrical driving means, the circuit comprising input leads to be coupled to a source of AC power, a mechanical switch actuated by said trigger, and electronic circuit means coupled to said input leads, said switch, and said electrical driving means, said electronic circuit means providing a burst of power to the electrical driving means when said switch is actuated by said trigger, the circuit means providing a small pilot control current through said switch, said pilot control current controlling the power burst to said driving means;

the improvement wherein said circuit means is sensitive to a break in said pilot control current and is actuated by opening of said switch to deliver said power burst;
and said switch is formed of a first and a second conductive member, the first member having a first flexible resilient conductive leaf fixed at one end and extending at another, free end thereof to be urged by said trigger;
said second member including a second resilient conductive leaf fixed at one end and having a bent-in member at a free end thereof with the bent-in member having a sharp point as its terminus contacting a side of the first flexible resilient conductive leaf, whereby when the first conductive member is moved in one direction by actuation of said trigger, the switch opens, and when the trigger releases the first conductive member, the resilience of the first conductive leaf moves the latter in the opposite direction and brings the two members back into contact to close the switch, and flexing of the first and second leaves moves the terminus of said bent-in member along the side of the first conductive leaf with the pointed terminus being operative to scratch away corrosion from an area of contact between said first and second members.

In a trigger switch circuit used in an electric hand tool of the type having a casing, a manually actuated trigger, and electrical driving means, the circuit comprising input leads to be coupled to a source of AC power, a mechanical switch actuated by said trigger, and solid state electronic circuit means mounted on a circuit board within said hand tool and electrically coupled to said input leads, said switch, and said electrical driving means, said electronic circuit means having a solid state element generating a burst of power furnished to the electrical driving means when said switch is actuated by said trigger, the solid state circuit means providing a small pilot current through said switch said pilot current controlling the power burst to said driving means;

the improvement wherein said solid state circuit means is sensitive to a break in said pilot current and is operative to be actuated by opening of said switch to deliver said power burst;
said pilot current is less than about one milliamp;
and said switch is formed of a first and a second conductive member, the first member having a first flexible resilient conductive leaf mounted directly on said circuit board at one end and extending at another, free end thereof to be urged by said trigger;
said second member including a second resilient conductive leaf mounted directly on said circuit board at one end and having a bent-in member at a free end thereof with a terminus contacting a side of the first flexible resilient conductive leaf, whereby when the first conductive member is moved in one direction by actuation of said trigger, the switch opens, and when the trigger releases the first conductive member, the resilience of the first conductive leaf moves the latter in the opposite direction and brings the two members back into contact to close the switch, and the flexing of the first and second leaves moves the terminus of said bent-in member along the side of the first conductive leaf to scratch away corrosion thereon.

1 more element

Dependencies are inferred from the claim text.