U.S. patent number 3,772,942 [Application Number 05/275,628] was granted by the patent office on 1973-11-20 for adjustable torque wrench.
Invention is credited to Bosko Grabovac.
United States Patent |
3,772,942 |
Grabovac |
November 20, 1973 |
ADJUSTABLE TORQUE WRENCH
Abstract
In a click-type torque wrench comprising an elongate tubular
lever, a work engaging head pivotally mounted at the front end of
the lever and having a lever arm projecting freely and rearwardly
in the lever, spring loaded cam and link means within the lever
rearward of the lever arm to normally yieldingly hold the lever arm
and head against pivotal movement relative to the lever, said
spring loaded cam and link means comprising a link with a flat
rearward disposed cam seat pivotally connected with and projecting
rearwardly from the lever arm, axially adjustable pivotal bearing
means between the ends of the lever, a slide block with a flat,
forwardly disposed cam seat in the lever, a cam block with flat
faces between and normally engaging the cam seats, spring means
rearward of the slide block and normally yieldingly urging the
slide block forwardly and novel, manually operable means rearward
of the spring means to vary the force exerted by the spring means
through the cam and link means.
Inventors: |
Grabovac; Bosko (Newport Beach,
CA) |
Family
ID: |
23053172 |
Appl.
No.: |
05/275,628 |
Filed: |
July 27, 1972 |
Current U.S.
Class: |
81/483 |
Current CPC
Class: |
B25B
23/1427 (20130101) |
Current International
Class: |
B25B
23/142 (20060101); B25B 23/14 (20060101);
B25b () |
Field of
Search: |
;81/52.4R,52.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones, Jr.; James L.
Claims
Having described my invention, I claim:
1. A click-type torque wrench comprising an elongate horizontal
lever with front and rear ends, a work-engaging head with a
vertical axis adjacent the front end of the lever, a lever arm
projecting rearwardly from the head, a crank pin on a vertical axis
connecting the rear end of the lever arm at the front end of the
lever, an elongate crank pivotally supported by and projecting
rearwardly from the crank pin, an elongate link with a front end
pivotally connected with the rear end of the crank and projecting
rearwardly therefrom, bearing means between the ends of the link
and pivotally supporting the link on a vertical axis shiftable
longitudinally of the lever, a slide block carried by the lever for
free longitudinal shifting relative thereto and spaced rearward
from the rear end of the link, spring means carried by the lever
rearward of the slide block and normally yieldingly urging the
slide block forwardly, cam means between the link and the slide
block including flat front and rear seats with laterally spaced
vertical shoulders at opposite sides thereof and defining laterally
spaced vertical corners on the link and the slide block
respectively and a cam block with flat front and rear faces between
and normally in flat bearing engagement with the front and rear
seats and having laterally spaced vertical edges in pivotal
engagement in said corners and means on the lever in spaced
relationship from the opposite sides of the rear ends of the crank
and the link to be engaged by the end of the link upon lateral
shifting of the crank and the link and to limit lateral shifting of
the rear end of the link and rocking of the cam block between said
seats resulting from the application of sufficient torsional force
applied to the head on the vertical axis thereof, through the lever
arm, crank and link to turn said cam block between said seats
against the force of the spring means.
2. A structure as set forth in claim 1 wherein said bearing means
is selectively shiftable longitudinally of the link whereby the
relative longitudinal extent and mechanical advantage of the
portions of the link extending forwardly and rearwardly from the
pivotal axis of said bearing means can be selectively varied to
adjust the operation of the wrench.
3. A structure as set forth in claim 2 wherein the lever is an
elongate tubular member with a central longitudinal bore, said
crank and link normally extending longitudinally and freely through
and substantially concentric with the bore, said bearing means
including a part on the link pivotally and slidably engaged in the
bore, said slide block is slidably engaged in the bore for free
longitudinal shifting therein, and said means to be engaged by and
to stop the link being defined by the portions of the bore at the
opposite sides of said link.
4. A structure as set forth in claim 2 wherein the lever is an
elongate tubular member with a central longitudinal bore, said
crank and link normally extending longitudinally and freely through
and substantially concentric with the bore, said bearing means
including a part on the link pivotally and slidably engaged in the
bore, said slide block is slidably engaged in the bore for free
longitudinal shifting therein, and said means to be engaged by and
to stop the link being defined by the portions of the bore at the
opposite sides of said link and crank, said bearing means is
selectively shiftable longitudinally of the link whereby the
relative longitudinal extent and mechanical advantage of the
portions of the link extending forwardly and rearwardly from the
pivotal axis of said bearing means can be selectively varied to
adjust the operation of the wrench.
5. A structure as set forth in claim 1, wherein said spring means
includes an elongate helical compression spring with a front end
engaging the slide block and extending rearwardly therefrom, and
adjusting means to vary the compression of and force exerted by the
spring onto the slide block and including a carrier block carried
by the lever rearward of the spring, an elongate longitudinally
extending screw thread in and through the carrier block and having
means at its forward end to engage the rear end of the spring, and
drive means including a manually engageable driver engaged with and
between the rear ends of the screw and the lever and shiftable
longitudinally from a normal forward position where it is in rotary
locked engagement with the lever and rotary unlocked engagement
with the screw to an actuated rear position where it is in rotary
unlocked engagement with the lever and rotary locked engagement
with the screw.
6. A structure as set forth in claim 5 wherein the lever is an
elongate tubular member with a central longitudinal bore, said
crank, link and spring normally extend longitudinally and freely
through and substantially concentric with the bore, said bearing
means includes a part on the link pivotally and slidably engaged in
the bore, said slide block is slidably engaged in the bore, said
means to be engaged by and to stop the link being defined by the
bore at the opposite sides of said link.
7. A structure as set forth in claim 5 wherein the carrier block is
fixed in the bore, said screw is concentric in and extending freely
longitudinally of the bore, said driver including an outer sleeve
portion engaged about the exterior of the rear portion of the
lever, a central core portion projecting from the rear end of the
sleeve portion into the bore and having a central opening with a
cylindrical rear portion and polygonal front portion freely
receiving the rear portion of the screw, said operating means
further including an elongate polygonal drive part on the rear end
of the screw freely engageable in the rear portion of said central
opening when the driver is in its forward position and establishing
driving engagement in the forward portion of said opening when the
driver is in its rear position.
8. A structure as set forth in claim 7 wherein said bore has
splines in its rear portion and said core has splines on its rear
portion, said splines on the core engaging the splines in the bore
only when the driver is in its forward position.
9. A structure as set forth in claim 8 wherein the forward end of
the rear portion of the opening defines a rearwardly disposed
shoulder and said polygonal part carries a radially outwardly
projecting stop part about its rear portion to engage said shoulder
and to limit rearward movement of the driver relative to the said
polygonal part and the lever.
10. A structure as set forth in claim 9 which includes
circumferentially spaced calibrating marks at the forward end of
the sleeve portion of the driver and said lever has axially spaced
calibrating marks to occur adjacent the forward end of the sleeve
portion when the driver is in its rear position and with which the
marks on the sleeve portion are cooperatively related to indicate
set operating forces of the wrench.
Description
This invention has to do with an improved torque wrench, that is,
with that class of wrench which includes means for limiting or
indicating to the operator of the wrench when a set of
predetermined force is transmitted by the wrench onto a related
piece of work, such as a screw fastener, or the like. More
particularly, this invention relates to an improved, adjustable
click-type torque wrench, that is, that particular type or class of
torque wrench which is such that when a predetermined, set force is
transmitted by the wrench onto a related piece of work, certain
parts within the wrench structure move rapidly from a normal
position to an actuated, stopped, position and in such a manner
that a slight movement, impact and audibly "click-like" sound is
transmitted by the wrench, to signal the operator that the desired,
set torque has been reached and applied to the work.
The ordinary torque wrenches of the specific type or class here
concerned with involve an elongate tubular lever arms with front
and rear ends, hand grip means at the rear end of the arms and work
engaging heads adjacent the front ends of the arms. The heads have
elongate pivot arms or cranks projecting rearwardly and freely into
and through the forward portions of the lever arms. The forward
portions of the pivot arms or cranks are pivotally mounted to the
forward ends of the lever arms and have flat rearwardly disposed
seats at their rear ends. Within the lever arms, rearward of the
cranks are longitudinally shiftable slide blocks with flat
forwardly disposed seats. Cam blocks with flat front and rear faces
are engaged with and between the seats on the cranks and blocks.
Within the lever arms, rearward of the blocks, elongate compression
springs are arranged to engage the blocks and normally yieldingly
urging the blocks forwardly toward the cranks, with the flat cam
faces in flat pressure engagement with the crank and block seats.
Within the rear end portion of the lever arms and engageable at the
exterior thereof, manually operable setting means are provided
which means engage the springs and are operable to vary the amount
of force exerted by the springs onto and through the blocks.
In operation, when a sufficient, actuating force is exerted between
the lever arms and the heads, as by manually applied force on the
lever arms, when the heads are in stopped engagement with related
pieces of work, the rear ends of the cranks pivot laterally in the
lever arms and strike the inner adjacent sides of the lever arms to
transmit audible clicking sounds. When the cranks swing laterally,
the cam blocks must turn or rock between their related seats. Such
rocking of the cam blocks urges the pressure blocks rearwardly
against the resistance of the springs.
The flat front and rear faces of the cam blocks have straight edges
on planes parallel with the pivotal axis of the cranks and the
seats with which said faces are related have shoulders against
which the noted straight edges of the cam blocks stop and are
pivotally supported.
The lateral extent of the cam faces and the axial or longitudinal
extent of the cam blocks determine the stability of the cam blocks
between their related seats. The dimensions of the cam blocks and
their resulting stability in established wrench structures is not
subject to change or variation.
It will be apparent that the magnitude of the actuating force in
wrenches of the character described above is determined by the
length of and mechanical advantage afforded by the cranks, the
stability of the cam blocks (both of which factors are fixed) and
the pressure exerted by the springs. By adjusting the pressure of
the springs, the actuating forces can be varied and sets (within a
limited range of forces) as desired.
While the above noted basic and old wrench construction has proven
to be quite satisfactory, it has been found to be wanting in a
number of ways. Due to the inherent limitations of space within the
lever arms of such wrenches, the effective length of the cranks is
limited and the size or dimensions of the cam blocks and their
resulting stability is restricted or limited. There are anumber of
other limiting and restricting features in such wrenches which
become apparent from a study of such structures, but which need not
be specifically considered at this time.
As a result of the above noted fixed, invariables in such wrenches,
the spring pressure must be considerable in those wrenches provided
for each range of forces that such wrenches are commonly provided
for. As a result of the high spring forces encountered, the
adjusting means provided to adjust and vary spring pressure are
subjected to high forces which makes them hard or difficult to
operate and which subjects them to undesirable rapid wear and early
fatigue. Also, the noted high spring pressures subject the cam
blocks and their related seats to exceptionally high forces which
result in undesirable rapid deformation and wear of those parts,
which wear and/or deformation upsets and alters the operating
characteristics of the wrenches and renders them inaccurate and
undependable.
In the wrenches provided by the prior art, as described above, when
the cam block and/or the cam block seats become worn and/or when
the springs change in character due to fatigue, there is no means
for adjusting and effectively recalibrating such wrenches and the
wrenches must be disposed of or their worn and/or fatigued parts
must be replaced.
In establishing wrenches, as set forth above, the effective range
of forces attainable by a single spring is limited, with the result
that special springs of predetermined strength must be provided for
each range of forces and, as a result, special wrenches, which
differ only in the special nature of the springs employed and, in
some cases, in the calibrations provided for setting the wrenches,
must be provided for each desired range of forces.
An object of feature of this invention is to provide a click-type
torque wrench having novel actuating means whereby the spring
forces, or strength of the spring employed can be materially less
than in wrenches of the same class provided by the prior art.
It is an object and feature of my invention to provide a wrench
structure of the character referred to above which is such that the
cam block and its related seats are subjected to materially less
wearing forces and the spring adjusting means is subjected to
materially less forces than in wrenches provided by the prior art
whereby my new wrench structure is materially easier to operate and
has a materially longer life expectancy than do wrenches provided
by the prior art.
Another object and feature of the instant invention is to provide a
wrench structure of the character referred to having novel
adjusting means whereby a single wrench structure can be adjusted
and set to operate throughout any desired operating range, without
the provision and use of special springs and a means whereby the
wrench structure can be effectibely adjusted to compensate for wear
and fatigue without requiring the replacement of parts and/or
reconstruction of the wrench.
Still further, it is an object and feature of this invention to
provide a wrench of the character referred to including an
intermediate link between the crank and the cam block which link is
pivotally connected with the crank and pivotally supported in the
lever arm; said link affording a mechanical advantage for the
spring and the cam means whereby the spring and its attending
forcing throughout the construction can be materially lessened.
It is yet another object and feature of my invention to provide a
means of the character referred to above wherein the pivotal
support between the link and the lever arm is adjustable
longitudinally of the link and said lever arm to afford adjustment
of the construction.
Finally, it is an object and feature of my invention to provide
improved adjusting means for the spring.
The foregoing and other objects and features of my invention will
be apparent and understood from the following detailed description
of a typical preferred form and application of my invention,
throughout which description reference is made to the accompanying
drawings, in which:
FIG. 1 is a side elevational view of my wrench with parts shown in
one position;
FIG. 2 is a top plane view of my wrench with parts shown in another
position;
FIG. 3 is an enlarged detailed sectional view taken as indicated by
line 3--3 on FIG. 1;
FIG. 4 is an enlarged detailed sectional view taken as indicated by
line 4--4 on FIG. 2;
FIG. 5 is an enlarged detailed sectional view taken as indicated by
line 5--5 on FIG. 1;
FIG. 6 is an enlarged detailed sectional view taken as indicated by
line 6--6 on FIG. 2;
FIG. 7 is a sectional view taken as indicated by line 7--7 on FIG.
5;
FIG. 8 is a sectional view taken as indicated by line 8--8 on FIG.
6;
FIG. 9 is a sectional view taken as indicated by line 9--9 on FIG.
5; and
FIG. 10 is a sectional view taken as indicated by line 10--10 on
FIG. 6.
It is to be understood that the drawings here provided and referred
to are for the purpose of illustrating the basic structure provided
by my invention and that certain liberty has been exercised in the
proportioning of parts for the purpose of better illustrating the
invention.
The wrench here provided includes an elongate, cylindrical,
tubular, lever A with front and rear ends 10 and 11, a work
engaging head H adjacent the forward end of the lever A and having
a rearwardly projecting lever arm 12 or limited longitudinal extent
projecting into the lever A; a crank pin P pivotally connecting the
lever arm 12 in and to the front portion of the lever A, (for the
purpose of this disclosure, the lever will be described as being
disposed or extending horizontally and the axis of the crank pin P
being on a vertical axis intersecting the central, horizontal,
longitudinal axis of the lever and/or the wrench structure). The
construction next includes an elongate crank C formed integrally
with the lever arm 12, projecting rearwardly in the lever A from
the pin P. The crank is preferably tapered rearwardly and normally
projects freely in and through the lever A, concentric with the
axis thereof and has a flat rear end 15 with a rearwardly opening
central socket 16.
The rear end of the lever arm 12 and front end of the crank C are
joined at the axis of the pin P by a semi-spherical enlargement 17
which establishes substantial free universal bearing support in the
bore of the lever and which is provided with a vertical bearing
opening 18 through which the pin P extends. The opposite ends of
the pin P are engaged and held in openings 19 in the lever, as
clearly illustrated in FIGS. 1, 2 and 3 of the drawings.
The head H can be of any desired form and style and is shown as a
substantially square, block-like member with a polygonal
work-engaging projection 20 depending therefrom, on a vertical axis
intersecting the central longitudinal axis of the structure.
The construction here provided next includes an elongate,
preferably cylindrical, link L, with front and rear ends 21 and 22
arranged in the lever, rearward of the crank C and normally
arranged with its axis concentric with the axes of the crank and
the lever.
The forward end portion of the link L project freely into the
socket 16 in the rear end of the crank and is pivotally connected
with the crank by a pivot pin P' engaged in registering openings 22
and 23 in the crank and the link. The axis of the pin P' is
vertical, normally intersects the central axis of the construction
and is parallel with the axis of the pin P and the projection 20 on
the head H.
The rear end 22 of the link is shown as being slightly enlarged and
is characterized by a flat rearwardly disposed front seat F, which
seat establishes an element or part of a cam means M, which will
hereinafter be described. The flat rearwardly disposed seat F is
defined by a vertically extending channel in the rear end of the
link L and is characterized by laterally spaced, laterally inwardly
and rearwardly disposed, vertical shoulders 25. The shoulders 25
are parallel with the axes of the pins P and P' and are spaced a
predetermined distance laterally from the central axis of the
link.
The construction that I provide next includes axially shiftably
longitudinally adjustable central bearing support means B between
the link L and lever A. The means B can vary considerably in form
or construction. In the preferred carrying out of my invention, and
as illustrated in the drawings, the means B includes a
semispherical support ring 30 slidably engaged on and about the
link L and establishing semi-universal, sliding, bearing engagement
in and with the bore of the lever. The support ring 30 is provided
with or carries a set screw 31 to releasably secure the ring
longitudinally of the link. The screw 31 can be an Allen head
screw, is accessible at the exterior of the ring and is accessible
through a radial access opening 32 provided in the wall of the
lever A. The opening 32 is normally closed by a closure band 33
releasably engaged in an annular recess 34 formed in the exterior
of the lever, as illustrated in the drawings.
With the structure thus far described, it will be apparent that the
link L is pivotally connected with the crank C and is slidably,
pivotally supported between its ends in the lever A. It will be
further apparent that by and through the means of the set screw 31,
the axial or longitudinal positioning of the bearing ring 30 on the
link L and the resulting central pivotal axis of the link can be
easily and conveniently varied and adjusted, as desired and as
circumstances require.
In practice, since it is an object of the link L and its related
bearing support means B to afford a mechanical advantage for the
cam means and a related spring means, to be later described, it
should be presently noted that the bearing means B for the link L
is preferably spaced a predetermined, desired distance forward of
the central radial plane of the link, whereby the lever arm portion
of the link, rearward of the central pivotal axis of the link is
longer than the lever arm portion of the link forward of said
axis.
The instant invention next includes a cylindrical slide block D
with flat front and rear ends 35 and 36 slidably engaged in the
bore in the lever in spaced relationship from the rear end 21 of
the link. The front end 35 of the block D has a flat, forwardly
disposed rear cam seat R, which seat opposes the front seat F on
the link. The seat R is similar to the seat F, being formed or
defined in the same or similar manner as the seat F is, and, like
the seat F, is chaacterized by laterally spaced, vertical shoulder
25', which shoulders are disposed forwardly and laterally
inwardly.
The present invention next includes a cubical cam block E, between
the seats F and R. The block E has front and rear faces 40 and 41
corresponding in size with the seats F and R and normally in flat
bearing engagement on and with said seats. The block E has opposite
vertical sides which join with the faces 40 and 41 to define
vertical edges on the block, at the opposite sides of the faces
thereof, which edges establish pivotal engagement in the vertical
corners established by the seats and their vertical side
shoulders.
With the above structure, which establishes the previously referred
to cam means M, it will be apparent that when the slide block D is
urged forwardly and axial pressure is exerted upon the cam block E,
the faces 40 and 41 establish and are maintained in stable, flat
bearing engagement with their opposing seats.
It will further be noted that when the rear end of the link L is
urged and caused to move laterally in the lever A, by the
application of forces on and through the head H and the crank C,
the cam block E is caused to turn or rock, out of seated engagement
with the seats F and R, in the manner illustrated in dotted lines
in FIG. 4 of the drawings. When the cam means is caused to shift
from its normal position to its actuated position, as described
above, the vertical edges or corners of the cam block E pivotally
seat and bear in the corners established by the seats and their
related shoulders.
When the structure is actuated, as above set forth, the rear end of
the link engages, strikes and is stopped by the bore of the lever A
before the cam block E is rotated an extent to cause it to shift
over or about its center and so that when the forces which caused
the rear end of the link to move laterally are released or removed,
any slight forwardly applied force on the slide block D will urge
the cam block E back to its normal position, which movement will in
turn, urge the link L, crank C and head H, back to their normal
positions.
When the construction is urged from its normal to its actuated
position, as set forth above, and as the cam block is caused to
rock or turn, slide block D is urged and caused to move and shift
rearwardly in the lever, against forwardly directed force applied
thereto.
The present invention next includes spring means S in the lever,
rearward of and engaging the rear end 36 of the slide block D and
normally yieldingly urging the slide block forward in the lever A
with limited or controlled predetermined force. The means S is
shown as including an elongate helical compression spring in the
lever A, with a front and seated on the rear end of the block D and
its rear end, stopped in the rear end of the lever A by a spring
stop member or means.
In practice, the spring stop member or means can be fixed or can,
as shown in the drawings, include a suitable manually operable
adjusting means O, which means is operable to vary the axial
pressure normally exerted onto the spring S and to thereby vary the
pressure of the block D and transmitted to and through the cam
means M.
The manually operable spring pressure adjusting means O provided by
this invention and illustrated in FIGS. 1, 2 and 5 through 10 of
the drawings includes a carrier block 50 fixed in the lever in
spaced relationship rearward of the spring S, an elongate axially
shiftable adjusting screw 51 threaded in and through the carrier
block 50 to project forwardly and rearwardly from the block 50,
concentrically and freely in the lever A. The screw 51 is shown in
the form of an elongate threaded bolt, with a head 52 at its
forward end. The head 52 of the screw 51 is engaged by a rearwardly
projecting teat 53 on an anti-friction washer 54 in the lever A,
which washer can engage and seat with the rear end of the spring S
or can, as shown, engage a cylindrical spacer 55 arranged between
the washer 54 and the spring S.
The rear end portion of the screw 51 carries an elongate polygonal
drive sleeve or nut 56 which nut projects freely from the rear end
of the screw and is shiftable longitudinally of the screw for
adjusting purposes and is secured in locked, fixed position on the
screw by a lock screw 57 engaged in the nut from the open rear end
thereof and either engages the rear end of the screw directly or,
as shown, engages a binding pin 58 arranged between the two noted
screws.
The means O next includes an elongate manually engageable driver 60
axially and rotatably engaged in and about the rear end portion of
the lever A and axially shiftable about the drive nut 56, from a
normal, forward, locked position, where it is locked against
rotation relative to the lever A and is out of driving engagement
with the nut 56, to a rear, operating position, where it is out of
locked engagement with the lever A and in driving engagement with
the nut.
The driver 60 is preferably a unitary cast or molded part of
durable plastic or the like and is characterized by an outer
cylindrical, manually engageable outside sleeve portion 61,
rotatably and slidably engaged about the rear portion of the lever
A, in bearing support therewith, and a central core portion 62
projecting concentrically in the sleeve portion 61 and into the
rear portion of the lever A. The rear end of the driver 60 normally
projects a short distance from the rear end of the lever A and the
portions 61 and 62 thereof join at said rear portions. The rear end
portion, for example, about the rear quarter of the core portion 62
is polygonal in exterior cross-section or is splined, as indicated
at 63. The rear portion of the bore in the lever A is polygonal or
splined, as at 64 to cooperatively engage the splined portion 63 of
the core when the driver 60 is in its normal forward position, as
shown in FIGS. 5 and 7 of the drawings and so that the driver and
the lever A are in rotary locked relationship with each other.
When the driver is moved rearwardly relative to the lever A, to its
rear, actuated or operating position, the splines 63 and 64
disengage and the driver is free to be manually rotated relative to
the lever.
The central core portion 62 of the driver 60 has an elongate
central opening with a polygonal front portion 65 to slidably
receive and establish driving engagement with the nut 56 when the
driver is in its rear actuated position, as shown in FIGS. 6 and 10
of the drawings, and an enlarged, normally rearwardly opening rear
portion 66 to freely accommodate the nut 56 when the driver is in
its forward normal position, as clearly shown in FIG. 5 and FIG. 7
of the drawings.
The inner forward end of the rear portion 66 of the opening in the
core portion defines a rearwardly disposed stop shoulder 67. The
rear end portion of the nut 56 is provided with an annular,
radially outwardly opening groove 68 in which a snap-ring type stop
ring 69 is releasably engaged. The stop ring 69 normally
establishes sliding friction engagement in the rear cylindrical
portion 66 of the central opening in the driver, to prevent it from
shifting freely axially. The stop ring further engages the shoulder
67 when the driver is shifted to its rear actuated position, to
prevent undesired disengagement of the driver from the remainder of
the construction.
In practice, the rear portion 66 of the central opening in the
driver 60 can be provided with an orienting groove 70 in which the
stop ring yieldingly seats when the driver is in its forward normal
position.
The rear end of the central opening in the driver is preferably
normally closed by a removable plug 71.
The forward end portion of the outer sleeve portion 61 of the
driver 60 is forwardly and inwardly tapered as at 75 and is
provided with suitable circumferentially spaced calibrating
reference marks or lines 76. That rear portion of the lever A,
which is normally covered by the driver 60 when it is in its normal
forward position and which is and/or can be exposed and/or
uncovered when the driver is in its rear, actuated position is
provided with and carries longitudinally spaced calibrating
reference marks or lines 77 with appropriate symbols and with which
the calibrating marks 76 on the driver are adapted to be
related.
In the preferred carrying out of my invention and as illustrated,
the portion of the lever A with which the marks 77 are related is
recessed as at 78 and the marks are applied to a band 79, as by
printing, which band is arranged and fixed in the recess 78.
The calibration and/or marks 76 and 77 can vary widely in practice
and are, for example, such that when certain of the marks 76 are
registered with certain of the marks 77, as by axial and rotary
movement of the driver relative to the lever A, the registered
marks indicate that force at which the wrench construction will
operate to indicate or signal the operator and thereby advise him
that desired, predetermined force has been exerted, through the
wrench onto a related piece of work.
In operation, when it is desired to adjust and set the wrench to
operate at a particular applied force, the driver is moved from its
normal, locked, forward position to its rear, unlocked, driving,
actuated position. When so positioned, the driver is rotated
relative to the lever A, rotating the nut 56 and screw 51 to
advance the screw 51 forwardly or rearwardly and to thereby
increase or decrease the axial compression of the spring S and
increase or decrease the force exerted by the spring onto and
through the cam means proportionately. As the nut and screw
assembly is moved axially relative to the lever A in the manner set
forth above, the axial position of the driver relative to the
lever, when the driver is in its rear actuated or operating
position is varied proportionately and the calibration of the above
described calibrating means is, also, varying proportionately.
In and during operation and use of my new wrench construction after
the adjusting means O has been adjusted and set to effect operation
of the wrench at a desired, predetermined force, when the head H of
the wrench is engaged with a related piece of work and the desired
force is applied onto the work, by manually applied force on and
through the hand grip portion of the driver 60 and the lever, the
crank C is caused to swing laterally in the lever, left or right,
depending upon the direction of applied force. As the crank swings
laterally about the axis of the pin P, it drives and swings the
forward end of the link L laterally in the same direction and the
rear end of the link in the other or opposite direction about the
central pivotal axis of the link, established by the bearing
support means B of the link. As the link is pivoted in the above
manner, the central pivotal axis of the link must and is free to
shift axially forwardly in the lever, a short but necessary
distance. As the rear end of the link is urged and moved laterally
in the above manner, the cam means M is operated and the slide
block is urged rearwardly against the resistance of the spring S,
as previously described.
Since, as previously noted, the rear portion of the link is longer
than the forward portion of the link, that is, since the rear lever
arm portion of the link, rearward of its central pivotal axis is
longer than its forward lever arm portion, the force applied to the
forward end of the link by the crank must be greater than the force
afforded by the spring S and cam means M, which resists lateral
shifting of the rear end of the link. As a result, the force of the
spring, acting upon and through the cam means can be and is
materially less than the spring force that would be required if the
link L was not provided and the front cam seat F was at the rear
end of the crank, as is common practice in the prior art.
It will be further apparent that by manually adjusting the
longitudinal position of the central pivotal axis of the link L, as
by shifting the ring 30 of the means B, the differential of the
front and rear movement or lever arms of the link can be adjusted.
Such adjustment of the link L and/or means B can be exercised to
fine adjust the wrench structure when new, to fine adjust said
structure to compensate for wear and the like, after it is used and
can be exercised to adjust the construction to operate in and
throughout different ranges of forces, which the spring S and/or
the adjusting means O therefor could not otherwise handle or be
employed for.
By virtue of the lighter spring force required in carrying out my
invention, as compared with such forces required in the wrenches
provided by the prior art, it will be apparent that the cam means M
and all other parts and means of my construction rearward of the
cam means are subjected to materially less spring applied, internal
forces, that the construction is therefore easier to operate, will
not wear or fatigue so rapidly and can be expected to have a
noticeably longer period of usefulness.
Having described only one preferred form and carrying out of my
invention, I do not wish to be limited to the specific details
herein set forth, but wish to reserve to myself any modifications
and/or variations which appear to those skilled in the art and
which fall within the scope of the following claims:
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