U.S. patent number 3,739,825 [Application Number 05/186,844] was granted by the patent office on 1973-06-19 for screwdriver.
Invention is credited to John D. Knox.
United States Patent |
3,739,825 |
Knox |
June 19, 1973 |
SCREWDRIVER
Abstract
The bit of a screwdriver has a finder sleeve supported about its
working end by a non-circular split ring having one or more
straight sections against which a shoulder on the bit engages. The
ring is flat on its O.D. side and it is disposed in a
larger-diametered groove in the sleeve so that its flat side is
spaced off the flat opposing wall of the groove and allows for
expanding the ring further into the groove to remove the bit from
its sleeve.
Inventors: |
Knox; John D. (Louisville,
KY) |
Family
ID: |
22686490 |
Appl.
No.: |
05/186,844 |
Filed: |
October 6, 1971 |
Current U.S.
Class: |
81/451 |
Current CPC
Class: |
B25B
23/101 (20130101) |
Current International
Class: |
B25B
23/10 (20060101); B25B 23/02 (20060101); B25b
015/00 () |
Field of
Search: |
;81/121R
;145/5R,5C,5D,5F,51 ;279/19,19.4,19.5,23 ;287/DIG.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Simpson; Othell M.
Assistant Examiner: Bicks; Mark S.
Claims
Therefore having described my invention, I claim:
1. An implement comprising, in combination, a bit having a forward
working end and a rearward mounting end, a finder sleeve rotatably
mounted on said bit about its working end and axially slidable
relative thereto, a coil spring within said sleeve and encircling
said working end, a retaining ring in a groove on said bit and a
shoulder internally of said sleeve between which the coil spring is
compressed with forward movement of the bit relative to the sleeve,
a continuous groove internally of said sleeve spaced rearwardly of
said shoulder, a resilient split retaining ring within said groove
and encircling the bit between its mounting end and the retaining
ring on the bit, one of said retaining rings having a straight
section against which the other of said retaining rings engages
when the bit is moved in a rearward direction relative to the
sleeve to inhibit separation of the bit and sleeve, said straight
section being yieldable in response to a suddenly exerted and
axially directed force against one of said bit and sleeve to allow
separation of the sleeve from the bit.
2. The combination of claim 1 wherein the retaining ring on the
sleeve has the straight section, the cross section of said ring
further having a dimension in its radial direction which is less
than its axially directed dimension.
3. The combination of claim 2 wherein the retaining ring received
within the groove of the sleeve has a generally D-shape in cross
section with its flat side facing the outer side wall of its
receiving groove and its arcuate side engaging the retaining ring
in the groove of the bit.
4. The combination of claim 1 wherein the non-circular ring has at
least two oppositely disposed straight sections.
5. The combination of claim 4 wherein the non-circular ring has
intervening arcuate resilient sections between its straight
sections which extend at least partially within its receiving
groove along the length thereof.
6. The combination of claim 3 wherein the non-circular ring has two
oppositely located straight sections.
7. An implement comprising, in combination, a bit having a forward
working end and a rearward mounting end, a finder sleeve rotatably
mounted on said bit about its working end and axially slidable
relative thereto, a continuous groove on the inner wall of said
sleeve, a continuous groove in the outer wall of the bit
intermediate its ends, a first retaining ring in said groove on the
bit, a second retaining ring within said groove of the sleeve and
encircling the bit between its mounting end and the ring in the
groove of the bit, one of said retaining rings being split and
having a straight section against which the other retaining ring
engages when the bit is moved in a rearward direction relative to
the sleeve, said one retaining ring having a cross-section which
includes a flat side facing the base wall of its receiving groove
and an inclined sloping wall which engages the I.D. surface of the
other retaining ring to yieldably retain the sleeve assembled about
the bit.
Description
This invention relates to screw drivers, more particularly to the
power-operated type, although the invention is certainly useful
with those that are manually-operated.
More specifically, the invention comprises a novel and improved
construction of bit and finder sleeve therefor which facilitates
removal when it is necessary to replace the bit.
A principal object of the invention is to provide such a
construction which is also practical and economical to manufacture
as well as to use.
In conventional finder sleeve designs, the sleeve has a
circular-cross section split retainer ring which seats in a
provided groove and encircles the bit engaging on a shoulder,
flange or second retaining ring on the bit. Usually, said flange or
ring on the bit cooperates with an internally located shoulder of
the sleeve to confine an encircling coil spring against which the
bit moves in the sleeve to engage its working end with the head of
a screw it is to be used to tighten. However, removal of the bit
from the sleeve, as when changing bits, has proved to be a problem.
Customarily a notch has been provided in the side sleeve at its
shank end through which the ring can be fished out. This is a
time-consuming and tedious operation. Moreover, the ring must be
constructed to close tolerances which will assure proper hold of
the sleeve to the bit during use.
It is the feature of this invention that the retainer ring of the
sleeve is given a non-circular shape or one more nearly polygonal
by deforming it from a true circular form to include at least one,
but preferably two, or more oppositely disposed straight sections
with intervening arcuate sections. Under the tension of the ring
the straight sections closely engage about the shank of the bit and
constitute abutments against which the retaining ring or other
abutment of the bit engages. The intervening arcuate sections of
the ring, however, more fully extend within the groove to
positively locate and hold the ring in place. Manufacturing
tolerances therefore become less of a problem since with the O.D.
of the arcuate sections bottoming in the groove, the I.D. of its
straight sections continues to provide interference preventing
separation of the sleeve from the bit.
Thus in operation of the screwdriver, the bit is free to rotate in
the sleeve and to slide forwardly in the sleeve against the
restraining action of the coil spring in order to engage its
working edge with the slotted head of a screw as the sleeve drops
about the screw head to hold it in position for said engagement by
the bit. The sleeve, however, is not dislodged and does not
separate from the bit, either on the down or return stroke of the
bit.
A further feature of the invention is that the retainer ring is
given a cross sectional shape which facilitates separation of the
sleeve from the bit when that becomes necessary. For this purpose,
a cross section is selected for the ring such that its thickness
considered in a direction radially of the ring is narrower than its
thickness considered axially thereof. This accommodates flexing of
the straight sections in response to a sudden heavy impact asserted
axially against the sleeve while holding the bit against movement.
This allows the sleeve retainer ring to slip past the shoulder or
retaining ring on the bit which normally restrains it.
Advantageously, the cross-section of the ring will have a D-shape
with its flat side facing outwardly and away from its engagement
with the shoulder of the bit. The D-shape affords the straight
section of the ring with the required resiliency and the arcuate
side which engages the bit retaining ring facilitates a camming
action to allow the inner bit retainer ring to slip by with flexing
of the straight sections of the sleeve ring.
Many other objects, advantages and features of the invention will
become apparent as the preferred embodiments are described
below.
DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, the same will now be
described in connection with the accompanying drawings, in
which:
FIG. 1 is a plan view partly in section illustrating a preferred
embodiment of the invention;
FIG. 2 is a cross sectional view taken along lines 2--2 in FIG. 1
looking in the direction indicated by the arrows and shows the
preferred form of sleeve retaining ring provided with two
oppositely disposed straight sections;
FIG. 3 is a sectional view taken along lines 3--3 of FIG. 2 looking
in the direction indicated by the arrows and illustrates a
preferred cross-sectional shape for the sleeve retainer ring;
FIGS. 4 and 5 show two other forms of sleeve retainer rings which
may be employed in accordance with the present invention; and
FIGS. 6 and 7 illustrate other cross sectional shapes which the
sleeve retainer ring may take according to this invention.
DETAILED DESCRIPTION
Referring now more particularly to the several views wherein like
parts are identified by like reference numerals, FIG. 1 illustrates
a bit at 10 having an intermediate shank 12, a rearward mounting
end 14 of polygonal shape by which it is non-rotatably supported
within the hollow of a holder (not shown) of a power-operated
screwdriver or of a handle of a manual screwdriver so as to be
rotated therewith. As illustrated, said mounting end 14 includes a
circumferentially extending recess or groove 16 by which it may be
removably secured within said holder as by a ring, detent or other
actuatable means in conventional fashion. At its forward end, bit
10 comprises a working end 18 suitably shaped to engage, for
example, within the kerf of the slotted head of a screw which is to
be tightened with rotation of the bit 10 by its holder. Mounted
about said working end 18 is a finder sleeve indicated generally at
20. Said sleeve has a recess 22 in its forward end which is conical
or otherwise shaped to accommodate the head of a screw and locate
it for engagement by the working end 18 of the bit which slides
axially forward through said sleeve 20.
As illustrated in FIG. 1, sleeve 20 has a through bore provided
with a cylindrical wall 21 which complements the cylindrically
shaped shank 12 of the bit in order to guide said axial sliding
movement of the bit within the sleeve while permitting the bit
freedom to also rotate in the sleeve. Said sliding movement of the
bit is stabilized by coil spring 24 which encircles said working
end of the bit and is confined within the sleeve between an
internal shoulder 26 on the sleeve and a split retainer ring 28
supported within a provided continuous circumferentially extending
groove or recess 30 on the bit shank 12. Sleeve 20 is provided with
means in the form of a second split retainer ring 32 which is
confined within internal groove 34 and serves as an abutment or
stop against which the bit retainer ring 28 engages to prevent
unintentional separation of the bit as when the bit and sleeve are
raised together off the screw head to an overhead position.
It is a feature of this invention, however, that the bit may also
be withdrawn through said rearward end of sleeve 20, as when it is
desired to change bits in the screwdriver or to replace the finder
sleeve. Thus the invention makes it unnecessary to provide each bit
with its own finder sleeve. Moreover, there will be instances when
it will be necessary to utilize more than one finder sleeve with a
particular bit so as to accommodate working on screws having
different head shapes.
Considering now FIGS. 2 and 3 with FIG. 1, it will be seen that
retainer ring 32 is not circular in shape, but has a pair of
oppositely disposed straight sections 38 with intervening arcuate
sections 40. In the embodiment of FIG. 4 ring 32 has four such
straight sections and in FIG. 5 but one straight section.
Preferably these straight sections 38 have an angular extent of
roughly between 45 and 60 degrees depending on the diameter of the
shank 12 of the bit with which the sleeve 20 is assembled. However,
in the case of the FIG. 4 embodiment there may be an advantage in
terms of increased resiliency if the straight sections are somewhat
shorter in length. The intervening arcuate sections 40 of the
retainer ring are substantially true sections or segments of a
circle; and preferably one of said arcuate sections will be split
as indicated at 42 in FIGS. 2, 4 and 5.
As illustrated in FIG. 2, the major portion of said straight
sections 38 of the sleeve retaining ring 32 lies outside the
receiving groove 34 and in the path of movement of the bit
retaining ring 28. The intervening arcuate portions 40 of said
retainer ring 32, however, reside within the confines of said
groove 34 along substantially their full extent. The angular extent
of the straight sections 38 is such that their separation or I.D.
of the ring as indicated at X is less than the O.D. of the retainer
ring 28 of the bit even when the O.D. of its arcuate sections 40
causes said arcuate sections to bottom on the groove 34. Ring 32
may therefore be made to commercial tolerances with full assurance
that its straight sections will, when the ring is assembled in
groove 34, effectively function as abutments against which the bit
retaining ring 28 engages to retain the sleeve in assembled
relation about the bit.
As illustrated by FIGS. 1 and 3, the sleeve retainer ring 32 has
been given a D-shape in cross section so that it is flat on its
O.D. or outer side, as indicated at 44 which faces the base or
horizontal wall 54 of the receiving groove 34. The I.D. or inner
side 46 of the ring 32, as illustrated in FIG. 3, comprises
substantially one-half of a true circle. However, its arcuate side
46 need not be truly circular. For example, it may have outwardly
sloping portions as illustrated at 46a and 466 in FIG. 6 which are
not true segments of a circle. Actually, no portion of the cross
sectional shape of the ring need be truly arcuate. Thus, as shown
in FIG. 7, the I.D. side of ring 32 may be defined by inner side
surface 46c which is disposed substantially parallel with its O.D.
or outer surface 44 and its surfaces 46a and 46b comprise inclined
flats terminating in upper and lower surfaces 46d which are more
nearly parallel with each other and at right angles to 46c.
However, including FIG. 7, the I.D. side of each of the illustrated
retainer ring 32 may be considered and therefore described as
"arcuate-like." Thus, in accordance with the invention, retainer
ring 32 may be said to have an arcuate-like shape surface 46 on its
I.D. side which constitutes the abutment against which the
retaining ring 28 of the bit abuts when the working end 18 of the
bit is fully retracted within its sleeve 20. It will also be
understood that when describing surfaces 44, 46a, 46b and 46c as
flat, actually this is true only in cross section and when
considered in the whole they are more truly conical or
cylindrical.
Referring now to FIG. 3, it will be seen that groove 34, which
receives sleeve retaining ring 32, is channel-like in shape and has
opposed generally planar upper and lower side walls 50,52 which are
generally parallel and spaced apart a distance only slightly
greater than the corresponding thickness of the retainer ring 32
which seats therein. The outer or base wall of said groove 34, is
indicated at 54, is flat or more aptly cylindrical in shape.
Considering now FIGS. 2 and 3 with FIG. 1, ring 32 loosely fits
within its receiving recess 34 and about shank 12 of the bit such
that the sloping underside 46a of its arcuate inner surface 46 in
at least the straight sections 38 engages with the surface of the
retainer ring 28 of the bit above the horizontal center line
thereof; and at least the arcuate sections 40 of said retainer ring
32 seat far enough within recess 34 that the sleeve 20 is thereby
suspended in an encircling relation about the working edge 18 of
the bit as illustrated in FIG. 1. In accordance with this invention
it is essential only that some portion of the straight sections 38
thus engage retaining ring 28 on the bit since reliance is placed
on the arcuate sections 40 to engage the upper surface 52 of the
groove 34 to retain the ring 32 within its receiving recess and
little or no reliance is placed on said arcuate sections 40 as
abutments to engage the retaining ring 28. In its non-working or
raised position some portion of 46b of ring 32 engages with the
upper side wall 52 of the channel groove 34 under the expanding
force of coil spring 24 so as to hold the sleeve 20 in its
illustrated position completely enclosing the working edge 18 of
the bit.
The illustrated D-shaped cross section of the ring increases the
ability of ring 32 and particularly its straight section 38 to flex
in a direction outwardly from retaining ring 28, while the arcuate
shape of the inner side of the straight segments 38, and
particularly their lower inclined slope 46a constitute a cam
surface which cooperates with the arcuate shape of the bit ring 28
to promote movement of the retainer ring 32 past the retainer ring
28 on the bit as said straight sections are caused to momentarily
flex outwardly in response to a sharp or sudden axially-directed
force exerted either against the sleeve or the bit while holding
the other stationary.
It will also be apparent that a similar advantage can be
accomplished if the bit retaining ring 28, as opposed to the sleeve
retainer ring 32, is provided with the above-described alternate
arcuate and straight sections, as well as the illustrated D-shaped
cross section. However, in this event, the flat side of the
D-shaped cross section of ring 28 would be on its I.D. or inner
side.
By deforming one of the retaining rings 32 and retaining ring 28,
as thus described, so that it has at least one and preferably two
oppositely disposed straight sections, the ring is given a more or
less polygonal shape which presents less of a manufacturing
problem. By this we have reference to the fact that in tests it has
been found that when retainer rings 28 and 32 are substantially
circular, it is important that tolerances be maintained within
about 0.004 inches in order that the I.D. of ring 32 will properly
abut the O.D. of ring 28 and at the same time permit separation of
the bit and sleeve as aforedescribed. To make a truly circular ring
within such tolerances is difficult. However, when sleeve retainer
ring 32, for example, is provided with straight sections as
described, manufacturing tolerances become considerably less of a
problem. Moreover, the illustrated D-shape in cross section of the
rings with the corresponding increased resiliency of the straight
sections which are now relied upon to engage ring 28 to support the
sleeve, render ring 32 susceptible to sudden applications of force
on either the sleeve or the bit to allow their separation as above
described.
Thus it will be apparent that all of the recited objects of the
invention have been demonstrated as readily obtainable.
* * * * *