Cutlery – Cutting tools – Saw
Reexamination Certificate
2002-02-26
2003-12-16
Shoap, Allan N. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S394000
Reexamination Certificate
active
06662455
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to saber saws. Various saber saws have been conventionally developed to cut or saw woody or steel materials or pipes in the housing or building construction sites or similar fields.
Conventional saber saws are basically classified into first and second types. According to a saber saw of the first type, a saw blade is reciprocated along a linear path. According to a saber saw of the second type, a saw blade is moved along an orbital path, for example, an elliptic path. The second type is also referred to as the orbital cutting type.
The conventional saber saws of the orbital cutting type, for example disclosed in U.S. Pat. No. 3,945,120 and in U.S. Pat. No. 3,461,732, are preferable to cut relatively soft material, such as woody members.
FIG. 1
shows a conventional saber saw of the orbital cutting type. A secondary shaft
109
is driven by a drive shaft
108
(of a motor or a comparable driving source). The secondary shaft
109
is provided with an eccentric shaft portion
109
b.
A wobble plate
118
is attached around the secondary shaft
109
. The wobble plate
118
converts the rotational motion of the secondary shaft
109
into a reciprocative movement. A saw blade
127
is attached to the front end of a plunger
120
. The plunger
120
is slidably coupled in a guide sleeve
113
. The guide sleeve
113
is swingable about its pivot ‘A’ defined by an axis which is perpendicular to the guide sleeve
113
and is fixed to a gear cover
106
. When the secondary shaft
109
rotates, the plunger
120
reciprocates in the back-and-forth direction in accordance with the motion converting mechanism of the wobble plate
118
which converts the rotation of secondary shaft
109
into the reciprocation of plunger
120
.
A link plate
135
is attached to a rear portion of guide sleeve
113
. The link plate
135
, extending downward from the guide sleeve
113
, has a distal end. The distal end of link plate
135
is brought into contact with the eccentric shaft portion
109
b
of secondary shaft
109
. During sawing operation, the saw blade
127
receives a reaction force F
1
which causes a clockwise moment about the pivot ‘A’ of guide sleeve
113
. The rear end of guide sleeve
113
moves downward. The distal end (i.e., lower end) of link plate
135
is depressed against the eccentric shaft portion
109
b
of secondary shaft
109
. The eccentric shaft portion
109
b
rotates in accordance with the rotation of secondary shaft
109
. The rotation of eccentric shaft portion
109
b
is transmitted to the guide sleeve
113
via the link plate
135
. Thus, the guide sleeve
113
swings in the up-and-down direction. As a result, the plunger
120
causes a mixed motion of the reciprocative motion and the swing motion.
The moving path of the saw blade
127
realized by the above-described mixed (i.e., reciprocative/swing) motion of the plunger
120
is dependent on the setting of a phase angle of eccentric shaft portion
109
b
relative to the plunger
120
.
FIG. 2
shows an orbital path of the saw blade
127
realized by the above-described mixed (i.e., reciprocative/swing) motion of the plunger
120
.
According to the orbital sawing operation shown in
FIG. 2
, the saw blade
127
chiefly cuts into a material
136
when the saw blade
127
is drawn toward the saber saw body (i.e., during the cutting stroke). This improves the efficiency of cutting work for sawing a wood or a relatively soft material.
FIG. 3
shows an ordinary sawing operation of a saber saw. A saw blade
127
with sawteeth is attached facedown to the front end of a saber saw body held by a user (not shown) in an upright position.
FIG. 4
shows another sawing operation of a saber saw held by a user (not shown) in an upside-down condition. The saw blade
127
is inversely attached to the saber saw body.
According to the above-described conventional saber saw of the orbital cutting type shown in
FIG. 1
, the sawing operation cannot be performed properly if the saw blade
127
is inversely attached to the saber saw body. More specifically, as shown in
FIG. 5
, the saw blade
127
receives a reaction force F
2
from the material
136
under the condition where the saber saw is held in the upside-down condition. The reaction force F
2
causes a clockwise moment about the pivot ‘A’ of guide sleeve
113
. The rear end of guide sleeve
113
moves downward. The distal end (i.e., an upper end in this case) of link plate
135
is released from the eccentric shaft portion
109
b
of secondary shaft
109
. Thus, the rotational motion of eccentric shaft portion
109
b
is not transmitted to the guide sleeve
113
. The plunger
120
does not cause a swing motion. The saw blade
127
attached to the front end of plunger
120
cannot move along an orbital path.
The saber saw disclosed in U.S. Pat. No. 3,945,120 discloses a member equivalent to the link plate
135
rotatably attached to the eccentric shaft portion
109
b.
If the linking mechanism disclosed in U.S. Pat. No. 3,945,120 is employed in the saber saw shown in
FIG. 1
, the plunger
120
will swing in the up-and-down direction even when the saw blade
127
is inversely attached to the saber saw body. The saw blade
127
will move along an orbital path shown in FIG.
6
. However, in this case, as better understood from the comparison between FIG.
2
and
FIG. 6
, the saw blade
127
moves in the opposite direction (refer to the direction of arrow) due to the unchanged phase relationship between the eccentric shaft portion
109
b
and the plunger
120
.
According to the orbital sawing operation shown in
FIG. 6
, the saw blade
127
cannot smoothly cut into the material
136
when the saw blade
127
is drawn toward the saber saw body (i.e., during the cutting stroke) because the saw blade
127
moves along an upper arc line far from the material
136
.
In this manner, none of the conventional saber saws teach a technical solution for enabling proper orbital sawing operation even when the saw blade
127
is attached inversely to the saber saw body.
The applicant's copending application Ser. No. 09/468,127, now patented as U.S. Pat. No. 6,282,797, discloses a saber saw of the orbital cutting type which can operate properly even when a saw blade is inversely attached to a plunger or a carrier.
PCT internal publication No. WO 98/07544 discloses a saber saw that approaches the better cutting performance of orbital saws without the complexity required for orbital motion and achieves a forward motion of the saw blade during the cutting stroke without resorting to orbital motion.
The proposed saber saws are still complicated in structure and need to be more simplified.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the prior art, an object of the present invention is to provide a saber saw of the orbital cutting type which can operate properly even when a saw blade is inversely attached to a saber saw body, thereby improving the efficiency of cutting work.
In order to accomplish this and other related objects, the present invention provides a first saber saw comprising a housing for accommodating a motor and a driven shaft rotatably supported by the housing and rotated by the motor. A plunger causes reciprocative motion with respect to the housing. A saw blade is attached to a front end of the plunger. A first motion converting mechanism, interposed between the driven shaft and the plunger, converts the rotational motion of the driven shaft into the reciprocative motion of the plunger. A second motion converting mechanism, interposed between the driven shaft and the plunger, converts the rotational motion of the driven shaft into the swing motion of the plunger. A plurality of eccentric shaft portions are formed on the driven shaft. The second motion converting mechanism includes contact portions selectively brought into contact with the eccentric shaft portions of the driven shaft.
According to a preferred embodiment of the present invention, the first saber saw of the present invention further comprises a gu
Osada Yoshio
Tachibana Toshihiko
Alie Ghassem
Hitachi Koki Co,. Ltd.
Parkhurst & Wendel L.L.P.
Shoap Allan N.
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