Tools – Wrench – screwdriver – or driver therefor – Having work engaging and force exerting portion inserted...
Reexamination Certificate
2000-06-09
2002-05-28
Smith, James G. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Having work engaging and force exerting portion inserted...
C081S460000, C411S403000
Reexamination Certificate
active
06393953
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a screw and a driver bit applied thereto, and to a combination of a screw and driver bit/wrench which realizes a tight engagement between an angular hole formed, for example, on a head of a hexagonal recessed screw or bolt and a driver bit provided with a bit tip formed to fit this angular hole, and which is capable of promptly and positively achieving attachment and detachment of the screw or the like by appropriate torque transmission.
BACKGROUND ART
FIGS. 13
to
16
show constructions of known conventional combinations of hexagonal recessed bolts and driver bits.
FIGS. 13 and 14
show a conventional bolt having a hexagonal recess at the center of the bolt head.
FIG. 15
illustrates a driver bit for the hexagonal recessed bolt.
FIG. 16
depicts how the bolt and the driver bit are engaged.
A conventional bolt
10
shown in
FIGS. 13 and 14
is provided with a hexagonal hole
12
at a bolt head
10
a
. This hexagonal hole
12
is formed so that constant, vertical wall surfaces
13
are respectively formed from the rim-edge toward a bolt neck
10
b
, and also a substantially conical bottom
14
with a slight slope is formed at the bottom thereof.
On the other hand, a conventional driver bit or wrench
20
in
FIG. 15
is constructed to be provided with a hexagonal tip blade
22
which fits the hexagonal hole
12
of the above-mentioned bolt
10
, and an appropriately elongated extended blade
22
a
formed to adapt to the shape of the vertical wall surfaces
13
formed from the rim-edge of the aforesaid hexagonal hole
12
toward the bolt neck
10
b
. The reference numeral
23
indicates a vertical wall formed on the side face between the above-mentioned tip blade
22
and the extended blade
22
a
. Namely, it is constructed so that the vertical wall
23
formed on the driver bit or wrench
20
tightly abuts and engages the vertical wall surface
13
formed on the hexagonal hole
12
of the above-described bolt
10
.
According to a combination of the conventional bolt and driver bit thus constructed, when the bolt
10
and the driver bit
20
are engaged as shown in
FIG. 16
, for example, the tip blade
22
and extended blade
22
a
of the driver bit
20
will respectively fit to the vertical wall surfaces
13
of the hexagonal hole
12
; and when the vertical wall
23
of the above-mentioned tip blade
22
and extended blade
22
a
abuts the vertical wall surface
13
on the hexagonal hole
12
in bolt
10
and the driver bit
20
is rotated, a specified torque can be transmitted to the bolt
10
. In other words, it is possible to attach/detach a bolt to/from an object to be bolted.
According to the conventional combination of bolt
10
and driver bit
20
with the configuration as mentioned above, a hexagonal hole
12
in bolt head
10
a
forms constant, vertical wall surfaces
13
from its opening edge toward the bolt neck
10
b
. On the other hand, in the driver bit
20
corresponding thereto, an area which is adjacent to each ridgeline from the hexagonal tip blade
22
to the extended blade
22
a
forms the vertical wall
23
corresponding to the shape of the vertical wall surface
13
on the above-mentioned hexagonal hole
12
, as shown in FIG.
16
.
Accordingly, in order to fit the blade
22
,
22
a
of driver bit
20
which has the above-mentioned vertical wall
23
forming the hexagonal side-surfaces, to the hexagonal hole
12
in bolt
10
which has the above-mentioned vertical wall side
13
forming the hexagonal side-surfaces, the tip blades
22
of the above-mentioned driver bit
20
is abutted to the opening edge of the hexagonal hole
12
in the above-mentioned bolt
10
. However, since length L
1
, i.e., the length between the symmetrically-opposing ridgelines across the center of hexagonal hole
12
, greatly differs from length L
2
, i.e., the length between vertical wall sides
13
, it becomes very difficult to manually match the center of the hexagonal hole
12
in bolt
10
with the center of the tip blade
22
of driver bit
20
. (See
FIG. 14
(dashed line therein) and
FIG. 16.
)
In this case, accordingly, if a part of the tip blade
22
of driver bit
20
engagingly abuts a part of the opening edge of the hexagonal hole
12
in the above-mentioned bolt
10
, a “come-out” phenomenon, where the tip blade
22
of the above-mentioned driver bit
20
slips out of the opening edge of the hexagonal hole
12
in the above-mentioned bolt
10
, may easily occur. When an excess force is applied to the driver bit
20
, and when the torque resistance is large, each of the ridgeline portions at the opening edge of the hexagonal hole
12
will gradually be damaged, as illustrated with shaded portion
15
in FIG.
14
. If this broken portion (shaded portion
15
) gradually expands, the above-described come-out phenomenon of the driver bit
20
will occur frequently, finally making a screwing operation impossible.
From this view point, prevention of the come-out phenomenon for the above-mentioned driver bit
20
requires application of a large pressure against the hexagonal hole
12
when rotating the driver bit
20
. No problem will occur when a rigid body, such as metal, is to be bolted or screwed. However, when handling precision parts, if the driver bit
20
comes out of the hexagonal hole
12
, there occurs a disadvantageous effect of damage or breaking these precision parts.
Further, occurrence of the above-mentioned come-out phenomenon will accelerate wearing of the bit tip, i.e., tip blade
22
and extended blade
22
a
. Wearing at these sites will further promote occurrence of the above-mentioned come-out phenomenon. As a result, damages of the hexagonal hole will also increase.
Yet further, it is possible to prevent the come-out phenomenon by applying an excess pressure to the above-mentioned driver bit
20
. However, it will be impossible to transmit a precise torque to a bolt, screw, or the like. Also, the amount of pressure applied to the driver bit
20
depends on an operator, resulting in a problem in that the screwing-torque applied to the bolt, screw or the like will vary.
When a bolt or screw is tightened manually, the operation of rotating the driver bit
20
by fully pressing the same against a bolt or screw may be a considerable labor and fatigue to the operator.
According to the conventional combination of bolt
10
and driver bit
20
as mentioned above, especially when an electrical tool is used to fix the screws, upon fitting the hexagonal hole to the bit tip, it is difficult to rotate a bolt while maintaining the bolt axis and the driver bit axis coaxially. When there is a deviation or slant between the bolt axis and the driver bit axis, for example, it is difficult to instantly fit the bit tip of driver bit
20
into the hexagonal hole at the bolt head as shown in
FIG. 14
(dashed line therein) and
FIG. 16
, not only will the above-mentioned come-out phenomenon be caused frequently, but damage of the opening edge of hexagonal hole will also be frequently caused.
When a hexagonal recessed screw is to be detached, the same come-out phenomenon and damage of the opening edge of hexagonal hole may easily occur. In this case, the screw cannot be detached, resulting in such a situation where a part of the object having been screwed has to be destroyed. Such a situation is especially remarkable when dust or the like is filled into the hexagonal hole.
It is an object of the present invention to provide a combination of a screw and a driver bit or wrench capable of: effectively preventing the come-out phenomenon of the driver bit, preventing screws from being damaged which had occurred conventionally, always achieving a proper and prompt screwing operation even if the polygonal hole in the screw is broken, and remarkably improving operation efficiency, by improving the configuration of a polygonal hole in a screw head in a combination of a screw and a driver bit.
DISCLOSURE OF THE INVENTION
In order to achieve the above aims, the screw according to the present invention is a polygonal recessed screw
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Smith James G.
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