Elongated-member-driving apparatus – With interlock means
Reexamination Certificate
2003-08-11
2004-08-31
Smith, Scott A. (Department: 3721)
Elongated-member-driving apparatus
With interlock means
C227S010000, C227S130000
Reexamination Certificate
active
06783045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combustion-powered nail gun that generates drive force by igniting a fuel/air mixture to drive a fastener such as a nail into a workpiece.
2. Description of the Related Art
U.S. Pat. Nos. 4,403,722, 4,483,280(Re.32,452), 4,483,473, and 4,483,474 disclose combustion-powered tool assemblies.
FIG. 1
schematically shows configuration of a conventional combustion-powered nail gun
100
similar to that disclosed in these U.S. Patents. The nail gun
100
includes a housing
114
to which a handle
111
, a tail cover
117
, a push lever
121
, and a magazine
113
are disposed.
The housing
114
accommodates therein a head cover
123
, a combustion chamber frame
115
, a cylinder
104
, and a piston
110
. The combustion chamber frame
115
, the head cover
123
, and the piston
110
together define a combustion chamber
105
. Further, the piston
110
divides the internal space of the cylinder
104
and the combustion chamber frame
115
into upper chamber S
2
inclusive of the combustion chamber
105
and a lower chamber S
1
. The head cover
123
and the cylinder
104
are fixed to the housing
114
. The combustion chamber frame
115
is vertically movable within the housing
114
as guided by the housing
114
and the cylinder
104
. The upper end of the combustion chamber
115
can be seated on the head cover
123
to provide the sealed combustion chamber
105
. Although not shown in the drawing, a connection rod linkingly connects the combustion chamber frame
115
with the push lever
121
so that the combustion chamber frame
115
and the push lever
121
move together in an interlocking relation to each other.
Further, a spring (not shown) is provided for urging the push lever
121
downward. Therefore, the push lever
121
and the combustion chamber frame
115
are urged downwardly while no force operates against the urging force of the spring. At this time, because the head cover
123
and the cylinder
104
are fixed, an inlet (not shown) is opened between the head cover
123
and a top end of the combustion chamber frame
115
, and an outlet (not shown) is opened between the upper outer peripheral portion of the cylinder
104
and the combustion chamber frame
115
. Although not shown in the drawing, annular seals for forming tight seals at the inlet and the outlet are provided at the lower end of the head cover
123
and the upper end of the cylinder
104
. Further, an intake vent (not shown) is provided in the upper end of the housing
114
, and a discharge vent (not shown) is provided in the lower end of the housing
114
.
The housing
114
further accommodates a motor (not shown), a spark plug
109
in a space above the head cover
123
. Further, a fuel canister
107
holding a fuel is disposed in the housing
114
. An injection port (not shown) connects the fuel canister
107
for supplying combustible gas from the fuel canister
107
into the combustion chamber
105
. A fan
106
is disposed in the combustion chamber
105
. The fan
106
is attached to and rotated by the drive shaft of the motor (not shown). Electrodes of the spark plug
109
are exposed to the combustion chamber
105
. Ribs
124
are provided on the inner surface of the combustion chamber frame
115
so as to protrude radially inwardly of the combustion chamber
105
.
A seal ring (not shown) is held at an outer peripheral surface of the piston
110
so as to be slidably movable with respect to the cylinder
104
. A bumper (not shown) is provided in the cylinder
104
and below the piston
110
for absorbing excessive energy of the piston
110
after a nail driving operation. Also, an exhaust hole (not shown) is formed in the cylinder
104
. A check valve (not shown) of well-known construction is provided on the outer side of the exhaust hole. A driver blade
116
extends from the piston
110
toward the tail cover
117
for driving a nail. A trigger switch spring
112
A is connected to the trigger switch
112
for biasing the trigger switch
112
toward its OFF position.
The handle
111
is attached to a middle section of the housing
114
. A trigger switch
112
is provided on the handle
111
. The trigger switch
112
is biased by a trigger switch spring
112
A for urging the trigger switch
112
toward its OFF position. Each time the trigger switch
112
is pulled (turned ON), the spark plug
109
generates a spark if the sealed combustion chamber
105
is provided.
The magazine
113
and the tail cover
117
are attached to the lower end of the housing
114
. The magazine
113
is filled with nails (not shown). The magazine
113
feeds the nails one at a time to the tail cover
117
. The tail cover
117
sets the nails fed from the magazine
113
in a position below the driver blade
116
and guides movement of the nails when the nails are driven downward by the driver blade
116
into a workpiece W.
A mechanism
200
for maintaining closing state of the combustion chamber
105
is provided. The mechanism
200
includes a trigger switch bracket
201
extending from the trigger switch
112
, a rod
202
extending from the combustion chamber frame
115
, and a cam
203
. The trigger switch bracket
201
has a lower end provided with a pivot pin
205
. The cam
203
has a slot opening
206
engaged with the pivot pin
205
. The cam
203
is pivotally connected to the housing
114
by a pivot bush
207
, and has a first stop surface
208
selectively engageable with a lower end of the rod
202
. Further, the cam
203
has a second stop surface
209
for preventing manipulation of the trigger switch
112
.
When the combustion chamber frame
115
is separated from the head cover
123
by the biasing force of the spring, the rod
202
is positioned beside the second stop surface
209
, so that counterclockwise pivotal movement of the cam
203
is prevented, thereby preventing upward movement of the trigger switch
112
. When the combustion chamber frame
115
is seated onto the head cover
123
, the rod
202
is moved away from the second stop surface
209
, so as to allow counterclockwise movement of the cam
203
. In this state, if the trigger switch
112
is pulled upwardly (turned ON) against the biasing force of the trigger switch spring
112
A, the cam
203
is pivotally moved in the counterclockwise direction, so that the lower end of the rod
202
can be seated on the first stop surface
208
. As a result, downward movement of the combustion chamber frame
115
is prevented by the abutment between the rod
202
and the first stop surface
208
.
If the tool
100
is moved away from the workpiece w and if the trigger switch
112
is released, the cam
203
can be piviotally moved in a clockwise direction by the biasing force of the trigger switch spring
112
A, so that the lower end of the rod
202
slides over the first stop surface
208
, and can be positioned beside the second stop surface
209
.
In the conventional combustion-powered nail gun, the piston
110
is moved to its lower dead center as a result of combustion, and the piston
110
is returned to its original upper dead center by the pressure difference between the upper chamber S
2
and the lower chamber S
1
. After the combustion, negative pressure is generated in the upper chamber S
2
because high pressure combustion gas is discharged through the exhaust hole and the check valve and because heat of the combustion chamber
105
is gradually absorbed into the cylinder
104
and the combustion chamber frame
115
to lower the internal pressure. This is generally referred to as “thermal vacuum”. On the other hand, atmospheric pressure is applied in the lower chamber S
1
. Thus, the piston
110
can be moved toward its upper dead center. If the nail gun
100
is moved away from the workpiece W when the piston
110
has reached its upper dead center, the combustion chamber
105
is open to atmosphere. Combustion gas remaining in the combustion chamber
105
is expelled out of the combustion chamber
105
and fresh air is introduced into the com
Ohmori Yasuki
Shima Yukihiro
Hitachi Koki Co,. Ltd.
Smith Scott A.
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