Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
POWER-DRIVEN SCREWDRIVER
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a power-driven screw-
driver for successively driving screws into a workpiece.
Prior Art:
A known screw tightening apparatus as disclosed in
Japanese Laid-Open Patent Publication NO. 53-37968, published
April 7, 1978, includes a screw indexing lever movable to
advance a strip of screws when a fork-shaped protective plate
or a leg plate is forcibly pressed against a workpiece. The
strip of screws is subjected to undue tensile forces which
tend to skew a screw in a position to be driven. The prior
apparatus also has a slide block and a slide plate which are
normally urged by a spring toward a position in which the
free end of a screwdriver bit is disposed in the slide block, and
the spring is displaced off the axis of the screwdriver bit.
When the slide block and the slide plate are forced to slide
into an outer frame against the resiliency of the spring before
a screw is driven by the screwdriver bit, the slide block and
the slide plate are liable to become inclined with respect to
the screwdriver bit, a disadvantage which renders the screw-
driver apparatus difficult to handle. The screw indexing
lever is also spring-loaded to feed screws, and the operator
finds the known screw tightening apparatus quite heavy and
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sluggish during screw driving operation. The conventional
power-driven screwdriver is also disadvantageous in that
it can easily damage the workpiece, the worn screwdriver bit
cannot readily be replaced with a new one, and the screw being
driven is likely to get tilted as it passes through the fork-
shaped protective plate.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
power-driven screwdriver which can drive screws successively
into a workpiece properly and reliably.
Another object of the present invention is to provide
a screw indexing mechanism for feeding a succession of
screws reliably into a power-driven screwdriver without
screws'being skewed or inclined.
Still another object of the present invention is to
provide a power-driven screwdriver having moving parts biased
by a spring disposed around a screwdriver bit and sli~able
smoothly, with a r~mot~r possibility for a spring-loaded
protectiv~ plate to dama~e a workpiece.
Still another object of the present invention is to
provide a power-driven screwdriver which is simple in construc-
tion, lightweight, and can be disassembled and adjusted with
ease.
Still another object of the present nvention is to
provide a power-driven screwdriver so structured that it will
permit easy replacement of a worn screwdriver bit, prevent
screws while being driven from getting tilted, and provide
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easy adjustment of the degree to which the screw is to
be driven into a workpiece.
According to the present invention, an elongate outer
guide frame of a power-driven screwdriver has a longitudinal
cam slot including an oblique portion and extending substan-
tially parallel to a screwdriver bit extending through a
slide block slidably mounted in the outer guide frame, the
screwdriver bit being attachable to a motor-driven tool.
A slide plate slidably supported on the slide block has a
transverse cam slot extending substantially perpendicularly
to the screwdriver bit. A screw indexing lever is swingably
mounted on the slide block and has on one end thereof a pin
received in the longitudinal and transverse cam slots. When
the motor-driven tool is pushed toward a workpiece, the slide
block and the slide plate are caused to slide into the outer
guide frame against the bias of a spring around the screw-
driver bit as the pin moves along the longitudinal cam slot.
After the screwdriver bit has driven a screw in~o the workpiece
arld wherl the motor-driven tool is retracted away from the
workpiece, the slide block and the slide plate are forced to
slide out of the outer guide frame under the resiliency of
the spring. When the pin enters the oblique portion of the
longitudinal cam slot and the transverse cam slot, the screw
indexing lever is turned to supply a next screw to a position
in front of the screwdriver bit. The outer guide frame has
a slant slot in which there is fastenably disposed a stop pin
with which the slide block is engageable at a rear end thereof
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to adjust the e~tent to which the slide block is insertable
into the outer guide frame and hence the extent to which
the screw can be driven into the workpiece. The slide block
has a hook-shaped slot near the rear end receptive of the stop
pin. When the stop pin is received and retained in the hook-
shaped slot, the slide block remains fully inserted in the
outer guide block, allowing the screwdriver bit to be exposed
and replaced easily with a new one.
The above and other objects, features and advantages
of the present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which show a preferred embodiment of the present
invention by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a power-driven
screwdriver according to the present invention, as attached
to a motor-driven tool;
FIG. 2 is a longitudinal cross-sectional view of the
power-driven screwdriver shown in FIG. l;
FIG. 3 is a plan view of the power-driven screwdriver;
FIG. 4 is a plan view of the screwdriver with its parts
in a position ready for driving a screw in a workpiece;
FIG. 5 is a plan view of the screwdriver, showing the
parts positioned just after a screw has been driven in a
workpiece;
FIG. 6 is a front elevational view, partly in cross
section, of the screwdriver;
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FIG. 7 is a perspective view of a slide block for
receiving therein a screw bit and a screw indexing mechanism.
FIG. 8 is a rear view of the slide block illustrated
in FIG. 7; and
FIG. 9 is a plan view of an outer guide frame with
the slide bloc~ of FIG. 7 shown as being in a fully retracted
position therein.
DETAILED DESCRIPTION OF THE ~REFERRED EMBODIMENT
As shown in FIG. 1, a power-driven screwdriver E is
attached to a portable motor-driven tool A such for example
as an electric drill for being driven thereby. The motor-
driven tool A is of any conventional structure and may be
energized by any suitable source of power though electric
operation is preferable because of no need for compressed air
or other mediums.
In FIG. 2, the motor-driven tool A has a rotatable
member or chuck B for holding a screwdriver bit C. The power-
driven screwdriver E generally comprises an outer guide frame
1 having a substantially channel-shaped cross section (FIG. 6),
a slide block 10 slidably mounted in the outer guide frame 1,
and a slide plate 20 slidably supported on the slide block 10,
the slide plate 20 being disposed between the outer guide frame
1 and the slide block 10. The slide block 10 and the slide
plate 20 are telescopically movable in the same direction with
respect to the outer guide frame 1. A cover 60 (FIGS. 1 and
6~ is resiliently snapped on the outer guide frame 1 to close
the open side of the latter.
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As best illustrated in FIG. 5, the outer guide frame
1 is of an elongate shape and has an elongate dimension such
that: it will accommodate the slide block 10 therein. The
outer guide frame 1 includes, as shown in FIG. 6, a bottom 7
and a pair of spaced sidewalls 8, 9 projecting laterally from
the bottom 7 and having a pair of ridges 3, 3, respectively,
directed toward each other. The outer guide frame 1 also
has on an end thereof an attachment sleeve 2 for being mounted
on the motor-driven tool A, the chuck B being positioned in
the attachment sleeve 2. The block 20 is slidable into and
out of the outer guide frame 1 through an open end of the
latter which is located remotely from the attachment sleeve 2.
The slide block 10 is also elongate in shape and has a
length which is about four-fifths of the length of the outer
guide frame 1, and a maximum thickness which is about two
times the depth of the outer guide frame 1. The slide block
10 has a pair of grooves 11, 11 (FIGS. 6 and 7) defined
respectively in opposite side faces thereof and opening away
from each other. The ridges 3, 3 of the outer guide frame 1
are slidably received in the grooves 11, 11, respectively.
Thus, the slide block 10 is guided by the ridges 3, 3 to slide
into and out of the outer guide frame 1.
The guide plate 20 also has an elongate configuration
having a length which is about four-fifths of that of the slide
block 10 and a width which is about two-thirds of that of the
slide block 10. A nose 21 extends from the guide plate 20 and
has a flat bent portion 22 perpendicular to the guide plate 20
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and disposed in overhanging relation to a distal end of the
slide block 10, the nose 21 having a width which is approxi-
mately half the width of the slide plate 20. The slide plate
20 rides slidably on a pair of shoulders 12, 12 (FIG. 7) on
the slide block 10 and is retained thereon against dislodge-
ment by a pair of holder strips 31, 31 screwed to the slide
block 10 and overhanging the shoulders 12, 12, respectively,
as shown in FIG. 7. The flat bent portion 22 serves as a
protective plate for protecting a workpiece while a screw
is driven thereinto by the screwdriver E and as a guide surface
for assisting in assuring perpendicularity of the screw while
the latter is being driven.
The slide plate 20 has a longitudinal slot 23 in which
there is disposed a spring adjustment member 32 fixed to the
slide block 10. A compression coil spring 33 is also disposed
in the slot 23 and acts between the slide plate 20 and the
spring adjustment member 32 to normally bias the slide plate
20 in a direction to move the latter out of the slide block 10.
The slide block 10 is illustrated in its entirely in
FIG. 7, and has a recess 13 extending laterally between the
shoulders 12, 12 and having a depth which is substantially
half the maximum thickness of the slide block 10. The slide
block 10 includes a projection 14 having an upper surface
extending continuously from and lying substantially flush with
one of the shoulders 12. The projection 14 has a hole 14a
through which extends a screw 41 ( FIGS. 1, 2 and 6) which
extends through an oblong hole 14c in the spring adjustment
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member 32 and threadedly into an internally threaded retainer
14b. By loosening the screw ~1, the spring adjustment member
32 can be moved relatively to the slide block 10, thus per-
mitting adjustment of the resiliency of the spring 33. The
slide block 10 also has a cavity 15 receptive therein of the
attachment sleeve 2 of the outer guide frame 1, and a longi-
tudinal through bore 16 communicating with the cavity 15 and
receiving therein part of the screwdriver bit C as best shown
in FIG. 2. The bore 16 includes a small-diameter portion 16a
extending from an annular step 17 and having a diameter large
enough to allow passage therethrough of the screwdriver bit C
with a slight clearance. A compression coil spring 34 is
disposed around the screwdriver bit C and acts between the
attachment sleeve 2 of the outer guide frame i and the step
17 in the bore 16 to normally bias the slide block 10 in a
direction to slide out of the outer guide frame 1, as illus-
trated in FIG. 3.
As shown in FIGS. 3 and 4, the bottom 7 of the outer
guide frame 1 has a longitudinal cam slot 4 extending parallel
to the screwdriver bit C and having an oblique end portion 5
located remotely from the attachment sleeve 2 and inclined
substantially at an angle of 45 degrees to the longitudinal
axis of the outer guide frame 1 or the screwdriver bit C.
The oblique end portion 5 of the cam slot 4 terminates just
short of a front end of the outer guide frame 1. The outer
end of the cam slot 4 is located adjacent to an opposite or
rear end portion of the outer guide frame 1. The slide plate
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20 has a cam slot 24 defined in a rear end portion thereof
which is remote from the nose 21, the slot 24 having a
transverse portion 24a extending perpendicularly to the
screwdriver bit C and slightly curved rearward. The slot
24 has one end 25 substantially aligned longitudinally with
the closed end of the oblique cam slot portion 5 and the
other end portion 26 directed forward toward the nose 21
and held substantially in longitudinal alignment with the
cam slot 4. A pin 35 extend through the cam slots 4, 24
and holds the slide block 10 in the fully projected position
(FIG. 3) against the combined force of the springs 33, 34
when the pin 35 is positioned at the ends of the oblique cam
slot portion 5 and the transverse cam slot 24. Stated other-
wise, the pin 35 as thus positioned in the cam slots 5, 24
prevents the slide block 10 and the slide plate 20 from moving
further oùt of the outer guide plate 1, with the nose 22
spaced from the front end of the slide block 10.
A screw indexing lever 51 tFIGS. 3 and 4) is swingably
disposed in the recess 13 in the slide block 10 and is attached
substantially centrally thereof to the slide block 10 by a
screw 51a threaded into a threaded hole 18 in the slide block
10 opening into the recess 13. The screw indexing lever 51
supports on a rear end thereof the pin 35, and is angularly
movable about the screw 51a in response to movement of the pin
35 along the cam slots4, 24. More specifically, when the slide
block 10 moves out of the outer guide frame 1 toward the position
illustrated in FIG. 3, the lever 51 is turned counterclockwise
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about the screw 51a until the pin 35 reaches the ends of
the cam slots 5, 24, to thereby advance screws S on a strip
F one at a time into a position in front of the screwdriver
bit C, whereupon the screwdriver E is ready for driving the
advanced screw S into a workpiece.
The screw indexing lever 51 has a distal tapered end
52 bifurcated into a bent portion 52a directed away from the
slide plate 20 and supporting a screw advancing finger 55
pivotably attached thereto by a pin 56, and stopper 53 with
which the screw advancing finger 55 is engageable. A tension
spring 58 acts between an upper end 54 of the screw advancing
finger 55 and a pin 57 mounted on the slide block 10 to normally
bias the screw advancing finger 55 in a direction to turn clock-
wise as shown in FIG. 6. The screw advancing finger 55 is
normally held in a vertical position with the upper end 54
abutting sidewise against the stopper 53 under the resiliency
of the tension spring 58. When the slide block 10 is retracted
into the outer guide frame 1, the screw indexing lever 51 is
turned clockwise (FIG. 4) about the screw 51a whereupon the
screw advancing finger 55 moves leftward as shown in FIG. 6
until it engages a next screw S. The slide block 10 has an
opening 19 (FIG. 7-) adjacent to its front end in which the
screw advancing finger 55 is movable back and forth for screw
ndexing operation.
The slide block 10 has at its front end portion a cut-
away recess 49 in which there are mounted a pair of inner and
outer guide plates 47, 48 for guiding therebetween the strip
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F of screws S, the guide plates 47, 48 having inner ends
loc,ated in the slide block 10 adjacent to the bore 16 and
outler ends disposed outside the slide block 10. The inner
guide plate 47 has an opening 46 (FIGS. 6 and 7) held in
communication with the opening 19 in the slide block 10 for
permitting reciprocating movement therein of the screw
advancing finger 55. The bore 16 opens at its distal end into
the cut-away recess 49.
As shown in FIGS. 3 and 6, the screws S are mounted
on the strip F at regular intervals, the strip F being made
of synthetic resin. The screws S are made of a material which
is hard enough to penetrate a relatively thin sheet of iron.
The guide plates 47, 48 jointly define a channel 48a receptive
therein of the heads of the screws S as the latter are fed
along between the guide plates 47, 48. A leaf spring 50 is
attached to the outer guide plate 48 for engagement at a distal
end thereof with the screws S one at a time as the screws S
are supplied, preventing the strip ~ from moving backward. The
outer guide plate 48 is removably mounted on the slide block
10 by a screw 42 having an enlarged grip head 43. Thus, the
screws S on the strip F can readily be removed upon detach-
ment of the ou~er guide plate 48.
The power-driven screwdriver E thus constructed will
operate as follows: The strip F on which the screws S are
mounted is first inserted between the guide plates 47, 48
until a first screw S is located below the bore 16 in alignment
therewith. With the protective plate 22 held flatwise against
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a workpiece lM to be fastened to a sheet L of iron, the
motor-driven tool A is then pushed toward the workpiece M,
whereupon the slide block 10 and the slide plate 20 are
caused by the pin 35 to move together into the outer guide
frame 1 (upwardly as shown in FIGS. 4 and 5) against the
resiliency of the spring 34 as the pin 35 slides in the oblique
cam slot portion 5 and the transverse cam slot 24, enabling
the screw indexing lever 51 to turn clockwise about the screw
51a. When the pin 35 enters the longitudinal cam slot 4 and
the cam slot portion 26, the slide plate 20 is allowed to
slide slightly upwardly into the slide block 10 against the
force from the spring 33. Such upward movement of the slide
plate 20 causes a portion of the protective plate 22 to abut
against and hold a next screw S stably between the guide
plates 47, 48, as shown in FIG. 4, while the first screw S is
being driven into the workpiece M and the iron sheet L.
At the same time, the screw advancing finger 55 moves
leftward from the position illustrated in FIG. 6 against the
bias of the spring 58 as the finger 55 is turned counterclock-
wise about the pin 56 until the finger 55 moves past the next
screw S. When the clockwise angular movement of the screw
indexing lever 51 is completed as shown in FIG. 4, the screw
advancing finger 52 has traversed the next screw S and is
forced to turn clockwise about the pin 56 under the bias of
the spring 58.
Continued movement of the motor-driven tool A toward
the workpiece M causes the slide block 10 to slide deeply into
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the outer guide frame 1, while at the same time permitting
the pin 35 to move upwardly in and along the longitudinal
cam slot 4. The screw-indexing lever 51 thus remains tilted
in the position shown in FIG. 4. The distal end of the screw-
driver bit C is now brought into contact with the head of the
screw S located in alignment with the bore 16. When the motor-
driven tool A is pushed on, the screwdriver bit C forces the
tip of the screw S to pass through a bushing or sleeve 27 on
the protective plate 22 and to be held against the workpiece
M. The bushing 27 serves to prevent the screw S from being
skewed or inclined while the scre~ S is being advanced toward
the workpiece M. Then, the motor-driven tool A is energized
to rotate the screwdriver bit C, thus causing the screw S to
rip off the strip F and driving the same home into the work-
piece M and the iron sheet L, whereupon the latter is tapped
by the screw S, Thus, the workpiece M and the iron sheet L
are firmly fastened together by the screw S, as illustrated in
FIG. 5.
The outer guide frame 1 has a slant slot 6 having one
end positioned adjacent to the longitudinal cam slot 4. A
stop pin 36 extends through the slant slot 6 and is slidable
along but fastenable at desired positions in the slot 6. When
a rear end of the slide block 10 abuts against the stop pin
36 as fixed in the slot 6, the slide block 10 is no longer
permitted to slide into the outer guide frame 1. Thus, the
stop pin 36 serves as an adjustment pin for adjusting the
extent to which the slide block 10 is insertable back into the
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outer auide frame 1 and hence the extent to which the screw
S is driven into the workpiece M.
After the first screw S has been driven, the power-
driven tool A is retracted away from the wor~piece M. The
slide block 10 and the slide plate 20 are now released. The
slifie plate 20 is forced to move relatively to the slide block
10 under the bias of the spring 33 allowing the protective
plate 22 to disengage the next screw S, as the slide block 10
and the slide plate 20 slide in a direction out of the outer
guide frame 1 under the force of the spring 34. When the
pin 3S enters from the longitudinal cam slot 4 into the oblique
cam slot portion 5 and from the cam slot portion 26 into the
transverse cam slot portion 24a, the screw indexing lever 51
starts swinging clockwise about, the screw 5;a whereupon the
scr,ew advancing finger 55 engages and indexes the next screw
S to the position below the bore 16 in alignment therewith.
As shown in FIG. 2, the slide block 10 has a presser
pin 37 which is spring-biased to hold the head of the supplied
screw S against a wall of the bore 16, thereby preventing the
screw S from getting skewed in the bore 16.
The strip F is preferably composed of two molded layers
of thermoplastic synthetic resin, one being thinner than the
other, sandwiching the screws S therebetween. When the screw
S is rotated by the screwdriver bit C, only the thinner layer
is ruptured to free the screw S. Thus, the strip F is prevented
from being torn to bits when the screws S are separated there-
from. Two of such strips F may be employed to support screws
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S which are relatively long. The strip F from which screws
S have been removed is successively discharged out of the
power-driven screwdriver E.
Repeated use of the power-driver screwdriver E tends
to wear the front end of the screwdriver bit C at a rapid rate.
The screwdriver bit C as worn to the point where it can no
longer be used can be replaced as follows: The pin 36 is
positioned at the end of the slot 6 which is located adjacent
to the longitudinal cam slot 4, and then the slide block 10
is inserted fully into the outer guide frame 1 against the
force of the spring 34. The pin 36 is inserted into a hook-
shaped slot 38 defined adjacent to the cavity 15 in the slide
block 10 and is retained therein by being displaced in a
direction away from the longitudinal slot 4. The slide block
10 is now held in the fully inserted position in the outer
guide frame 1, with the end of the screwdriver bit C projecting
out of the outer guide frame as illustrated in FIG. 9. The
screwdriver bit C is pulled out by pliers or other tools, and
a new screwdriver bit is inserted into the bore 16 and attached
to the rotatable member B of the motor-driven tool A.
Although a certain preferred embodiment has been shown
and described in detail it should be understood that various
changes and modifications may be made therein without departing
from the scope of the appended claims.
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