Electricity: circuit makers and breakers – Switch activation inhibitor – Actuator blocking device
Reexamination Certificate
2000-02-01
2001-04-17
Friedhofer, Michael A. (Department: 2832)
Electricity: circuit makers and breakers
Switch activation inhibitor
Actuator blocking device
C200S321000, C200S322000
Reexamination Certificate
active
06218633
ABSTRACT:
This application claims priority on Japanese Patent Application No. 11-34430 filed on Feb. 12, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to switch mechanisms for use in electric power tools, such as blowers, for controlling the rotational speed of the tool motors. More particularly, the present invention relates to such a switch mechanism which includes a speed change switch having a plunger and a trigger switch for pushing in the plunger.
2. Description of the Related Art
A typical blower is provided with a switch mechanism which includes a speed change switch having a plunger and a trigger switch for pushing in the plunger. Such a speed change switch is generally accommodated in the handle of the blower. The switch mechanism regulates the rotational speed of the tool motor according to the displacement of the plunger as the trigger switch is pulled in. The Applicant disclosed in Japan Published Unexamined Patent Application No. 6-254779 one such switch mechanism which includes a trigger switch and a regulating member, such as a speed change thumb-screw, mounted on the housing of the tool. The speed change thumb-screw includes a semicircular cam eccentrically mounted on the screw's shaft. When pulled protrusions on the trigger switch are brought into contact with the cam, thus limiting the movement of the trigger switch. Since the semicircular cam of the thumb-screw is eccentrically mounted on the screw's shaft, the user of the tool can readily adjust the maximum amount by which the trigger switch is pulled in by turning the thumb-screw.
While this switch mechanism achieves its intended objective, it is not free from certain problems and inconveniences. For example, as the trigger switch is located away from the speed change thumb-screw, when the user grips the handle, for example, with his right hand and pulls the trigger switch with the index finger, no other finger of the hand reaches the thumb-screw. As the user cannot operate the two elements simultaneously with one hands the left hand is needed to adjust the speed change thumb-screw. However, as a blower is often operated by one hand to direct airflow to various objects held by the other hand, operation of this switch mechanism requires the user to interrupt the work in order to adjust the setting of the thumb-screw to change the airflow. This reduces the ease of use of the tool and affects work efficiency.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a switch mechanism for an electric power tool whose trigger switch and regulating member are operable with one hand.
Another object of the present invention is to provide a switch mechanism for an electric power tool that improves the ease of use of the tool and work efficiency.
The above objects and other related objects are realized by the invention, which provides a switch mechanism for use in an electric power tool which is driven by a motor and includes a handle. The switch mechanism comprises: a speed change switch having a plunger, the speed change switch controlling the rotational speed of the motor; a trigger switch protruding out of the handle for being pulled to displace the plunger, the trigger switch displacing the plunger in correspondence with the amount by which the trigger switch is pulled; and a regulating member provided adjacent to where the trigger switch protrudes out of the handle so as to be operable from the outside of the handle. The regulating member, when operated, blocks the movement of the trigger switch as the trigger switch is pulled, thus controlling the amount by which the trigger switch is pulled. According to the foregoing switch mechanism, the regulating member can be operated to determine the amount by which the trigger switch is pulled into the handle, thus controlling the rotational speed of the motor. Moreover, as the regulating member is exposed adjacent to where the trigger switch projects out of the handle to permit operation from the outside of the handle, the user of the electric power tool can operate the trigger switch and the regulating member simultaneously with the hand holding the handle. This means the user can adjust the operation of the motor without discontinuing the work, thus enhancing the operability of the electric power tool and work efficiency.
According to one aspect of the present invention, the trigger switch, the speed change switch, and the plunger are disposed along an axis with the plunger interposed between the trigger switch and the speed change switch. In addition, when operated, the regulating member is located between the trigger switch and the speed change switch without interfering with the plunger so as to block the movement of the trigger switch.
According to another aspect of the present invention, the regulating member is a generally circular member rotatably supported by a shaft such that when the circular regulating member is rotated, a portion of the member is located between the trigger switch and the speed change switch and blocks the movement the trigger switch. The regulating member, being circular and rotatably operated on a shaft, facilitates adjustments of the rotational speed of the motor without affecting the manual operation of the trigger switch.
According to still another aspect of the present invention, the regulating member is capable of rotating between at least two positions and includes a cut-out and an arm defined by the cut-out, with the cut-out configured so as to allow the trigger switch to move through the regulating member without interference. When the regulating member is located in a first position, the arm blocks the movement of the trigger switch and when the regulating member is located in a second position, the trigger switch can be pulled through the cut-out without interference.
According to yet another aspect of the present invention, the arm is formed with a first surface located at a first predetermined distance from the trigger switch when the trigger switch is not pulled and the arm is further formed with a second surface oriented at an angle to the first surface and located at a second predetermined distance from the trigger switch when the trigger switch is not pulled. In this case, the second distance is made greater than the first distance. In addition, when the regulating member is in the first position, the first surface blocks the trigger switch as soon as the trigger switch has moved the first distance, and when the regulating member is in a third position, the second surface blocks the trigger switch as soon as the trigger switch has moved the second distance. Therefore, the movement of the trigger switch and thus the displacement of the plunger can be controlled in three different levels in this switch mechanism.
According to one feature of the present invention, the switch mechanism further comprises a rotation limiting member for allowing rotation of the regulating member within a predetermined range having two outer limits. One of the outer limits is located in the first position, whereas the other is located in the second position with the third position located intermediately between the two outer limits.
According to another feature of the present invention, the handle includes a pair of casing halves generally symmetrical about a ridge and the handle further includes two windows provided on both sides of the ridge so as to expose a peripheral surface of the circular regulating member for operation of the regulating member from the outside of the handle. As the circular regulating member is exposed to both sides of the handle for manual operation, the electric tool can be used equally well whether the user holds the handle with the right or left hand.
According to still another feature of the present invention, the regulating member includes at least two interfering surfaces for, when rotated, blocking the movement of the trigger switch to dis
Ito Hidenori
Okumura Michio
Foley Hoag & Eliot LLP
Friedhofer Michael A.
Makita Corporation
LandOfFree
Switch mechanism for use in an electric power tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Switch mechanism for use in an electric power tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switch mechanism for use in an electric power tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502686