Cutlery – Cutting tools – Saw
Reexamination Certificate
1999-05-12
2001-05-08
Watts, Douglas D. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S393000
Reexamination Certificate
active
06226877
ABSTRACT:
This application claims priority on Japanese Patent Application No. 10-130476, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sealing structures for preventing entry of dust, water, and other foreign matter into electric power tools. More particularly, the present invention relates to a sealing structure for blocking ingress of foreign matter into a body housing of a reciprocating saw and other electric power tools having a reciprocating slidable member which protrudes from the body housing of the tool.
2. Description of the Related Art
Conventionally, electric power tools, such as reciprocating saws, having a reciprocating slider which penetrates a body housing employ a dust seal or packing where the slider penetrates the housing in order to seal the interior of the body housing. Complete sealing, however, has been difficult to achieve due to the reciprocating motion of the slider. Dust tends to enter the body housing particularly easily when the slider is retracted into the body housing. If a reciprocating saw is used to cut a water pipe or is operated under wet conditions, water may enter the body housing of the tool. Such ingress of dust or water may cause damage to or wear of the internal gearing, or hinder the function of the internal bearings of the reciprocating saw, thereby affecting the overall operation of the tool.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a sealing structure for use in an electric power tool for effectively preventing entry of dust and water into a body housing of the tool, thus ensuring greater durability for the tool.
The above objects and other related objects are realized by the invention, which provides a sealing structure for use in an electric power tool which comprises a sealed chamber containing a portion of a reciprocable slide member having a front end which penetrates the chamber and a rear end disposed within the chamber. The sealed chamber, including the area penetrated by the slide member, is sealed off from the outside. The sealing structure further comprises an air vent formed in the sealed chamber for placing the sealed chamber in communication with the atmosphere and a valve provided in the sealed chamber and movable between a first position and a second position. When in the first position, the valve opens the air vent due to an advance of the slide member and when in the second position, the valve closes the air vent due to retraction of the slide member.
According to one aspect of the present invention, the sealed chamber is located downwind of a fan for cooling a motor provided in the electric power tool. Furthermore, the sealed chamber includes a partition wall in close proximity to the fan and the air vent is formed in the area of the partition wall opposing the fan.
According to another aspect of the present invention, the sealed chamber is defined by a pair of casing halves fitted together to form a seam and the sealing structure further comprises an endless seam packing fitted along the entire length of the seam between the casing halves.
According to still another aspect of the present invention, the valve is made of a resilient material formed integrally with the packing and is adapted to move between the first and the second positions in response to the change in the air pressure inside the sealed chamber caused by the reciprocating motion of the slide member.
According to yet another aspect of the present invention, the valve in one embodiment is of the flap or flapper type and is formed in an approximate V-shape having a bottom portion. Furthermore, the flap of the valve is suspended from the seam packing in close proximity to the partition wall inside the sealed chamber and includes a protrusion at the bottom portion for abutting and closing the air vent due to the retraction of the slide member and for moving forward to open the air vent due to the advance of the slide member.
In accordance with another aspect of the present invention, the sealing structure further includes means for positioning the protrusion of the valve with respect to the air vent. This feature allows accurate positioning of the protrusion, for example, during assembly of the electric power tool.
In accordance with still another aspect of the present invention, the sealing structure further includes at least one air passage for bringing a portion of the airflow generated by the fan into the proximity of the area of the sealed chamber penetrated by the slide member via the exterior of the sealed chamber so as to discharge the portion of the airflow substantially parallel to the direction of the advance of the slide member.
In one practice, the sealed chamber includes a casing upper half and a casing lower half which includes the partition wall, and moreover, two of the air passages are symmetrically grooved along the exterior of the casing lower half, each connected at a rear end to a through-hole formed in the partition wall of the sealed chamber.
In another practice, the electric power tool is a reciprocating saw in which a blade is attached to the front end of the slide member.
The present invention is also directed to a reciprocating saw which includes a chamber capable of being selectively sealed off from the outside thereof and a slide member which is disposed in the sealed chamber and has a front end penetrating the sealed chamber to the outside thereof. This slide member is adapted to reciprocate in lengthwise directions between an advance position and an retracted position. The reciprocating saw further includes valve means for placing the inside of the chamber in communication with the outside thereof due to the advance of the slide member and for sealing the chamber due to the retraction of the slide member.
According to one embodiment, the reciprocating saw further includes seal means mounted in the chamber where the chamber is penetrated by the slide member for sealing the chamber where the chamber is penetrated by the slide member. The seal means is also adapted to allow an amount of air substantially corresponding to the volume displaced by the retraction of the slide member within the chamber to be discharged forward out of the chamber at the seal means.
According to another embodiment, the chamber includes at a rear end thereof a wall in which the valve means is mounted and the reciprocating saw further includes a fan provided outside the chamber and directly rearward of and in close proximity to the valve means for delivering air into the chamber through the valve means due to the advance of the slide member.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.
REFERENCES:
patent: 2116123 (1938-05-01), Ocenasek
patent: 2631619 (1953-03-01), Folli
patent: 2722244 (1955-11-01), Schultz
patent: 3033252 (1962-05-01), Atkinson
patent: 4962588 (1990-10-01), Fushiya et al.
patent: 5392519 (1995-02-01), Inoue et al.
Foley Hoag & Eliot LLP
Makita Corporation
Watts Douglas D.
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