Note: Descriptions are shown in the official language in which they were submitted.
DIMINISHING ARM TOGGLE LINKAGE
BRIEF_SUMMARY OF THE INVENTION
This invention relates to an improved diminishing arm
toggle linkage for plier type hand tools and hand or power
operated bench presses used for crimping, riveting or staking
operations and the like. More particularly, the invention
relates to such a linkage in which the force work site is
disposed within the geometry of the toggle rather than external
to it. In preferred embodiments the invention includes auto~
matic shifting, on demand, from a pivoting mode of operation to
a rolling mode as the load at the work site increases.
The prior art includes a variety of simple plier, compound
leverage and toggle actuated staking, crimping and riveting
tools which have extremely heavily loaded pivot pins subject to
friction, wear and galling with attendant dimensional deteriora-
tion, all compounded by the number of pivot stages involved.
These tools run the g~mut from inexpensive, hard to operate
tools to e~pensive easier to operate tools. In all such toagle
actuated tools of which I am aware the work or crimping site is
external to the toggle arm geometry and the grips are not
adapted for one-handed operation.
My invention eliminates many of the aforementioned prior
art problems. Staking - crimping tools embodying my invention
w
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72
includ~ la) an output/input force curve ratio allowing easy,
single stroke, one-handed operation in staking a workpiece;
~b) a clear, easily entered open-sided work site to accept the
workpiece when the tool is wide open; (c) a comfortable, single-
handed grip on the wide open handles; (d) provision for remov-
able, interchangeable staking tooling; ~e) provision for auto-
matically changing from a pivoting mode of operation to a
rolling mode as the load at the work site increases; ~f~ a
staking tool site within the geometrical boundary of the toggle
linkage to take greatest advantage of the di~.inishing arm toggle
feature; (g) minimum size and weight consistent with the tool
function; (h) a geometrically diminishing rate tool opening
return spring; (i) a late acting tool-kick-open spring which
takes e~fect after the peak input force is passed and does not
cause the last portion of the input curve to exceed the already
pas~ed peak force; and (j) economical manufacture.
In accordance with the invention, I provide a diminishing
arm toggle linkage comprising (a) first and second elongated
force applying members having their longitudinal axes aligned,
said force applying members each having an inner and an outer
end, said inner ends being adjacent to each other on the axial
line, said force applying members being mounted for axial
movement toward and away from each other between a closed
abutting position and an open spaced apart position to thereby
define a work space between said inner ends which diminishes
Hadden - 3
;72
axially when said force applying members are moved toward each
other; (b) a third elongated member attached for pivotal motion
at its one end to a point on said second force applying member
spaced from said inner end thereof; (c) a fourth elongated
member attached for pivotal motion at its one end to a point
near said outer end of said first force apply~ng member; Id) the
other end of said third member being attached for pivotal motion
to said fourth member at a point spaced from said one end of
said fourth member; (e) the distance between attachment pOl:l~S
on said third and fourth members respectively defining first and
second toggle arms; (f) the distance between the attachment
point on said first force applying member and the attachment
point on said second force applying member defining a third
toggle arm, the length of which varies by the distance from
open to closed position9 of said first and second force applying
members; and (g) the length of said second toggle arm being
substantially e~ual to the length of said first toggle arm plus
the length of said third toggle arrn in the closed position.
In a preferred embodiment, I provide a tool for forming a
work piece to a predetermined shape and size, comprising (a) an
elongated chassis member; (b) a first die member fi~edly mounted
in said chassis member near a first end of said chassis member;
~c) a second die member mounted in said chassis member for
sliding movement toward and away from said first die member
along a common aY.is which is parallel to the longitudinal axis
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~ ~6~57%
of said chassis member; (d) said first and second die me~bers
having complementary mating surfaces shaped so that when said
mating surfaces meet they form a cavity having said predeter-
mined size and shape of said work piece; (e) a first elongated
toggle arm member having one end connected for pivotal movement
to said first end of said chassis member at a first pivot site;
and (f) a second elongated toggle arm member having one end
connected for pivotal movement to said second die member at a
second pivot site and the other end connected for pivotal
movement to said first toggle arm at a third pivot site spaced
from said one end of said first toggle arm, wherein the distance
between pivot sites on said first toggle arm is substantially
equal to the distance between pivot sites on said second toggle
arm plus the distance between the pivot site on said chassis and
the pivot site on said second die member when said mating
surfaces of said die members are tightly abutting, and wherein
each pivot site includes a pivot axis which is perpendicular to
said longitudinal axis of said chassis member, all said plvot
axes being parallel to one another.
Preferably, my tool includes first stop means for limiting
to a predetermined length the distance by which said second die
member can be moved away from said first die member and second
stop means for stopping movement of said second die member
towards said first die ~ember at a point short of that at which
all three said pivot points are in ctraight alignment along said
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~6~i72
axis of sliding movement~ the tool being open when said first
stop means is engaged and closed when said second stop means is
engaged.
In order to assure complete deformation of work pieces, my
tool may include anti-reversing means restricting movement of
said second die member to one direction only when said second
die member is at any point between the open and closed
positions.
In a useful embodiment my tool includes spring biased means
for adding lubrication to at least one pivot site on each cycle
of said tool from open to closed and back to open.
In an especially preferred embodiment, the connection for
pivotaI movement at at least one of said pivot sites includes a
cylindrical cross pin affixed to one of the two pivoting members
and an ob-round hole formed in the other pivoting member, said
cylindrical cross pin having predetermined diameter D1 and
having its longitudinal axis congruent with the pivot axis at
that pivot site, at least a portion of the length of said cross
pin being positioned within said ob-round hole, said ob-round
hole having two semicircular ends of predetermined diameter D2
and two parallel straight sides, the width of said ob-round hole
being equal to D2, the overall length of said ob-round hole
being up to about 1.5 times D2, D2 being from about 1.001 to
about l.01 times D1, said ob-round hole being so oriented that
when said tool is in the closed position the long dimension of
Hadden - 6
~6~ 2
said ob~round hole is substantially perpendicular to both ~aid
pivot axes and said longitudlnal axis of said chassis member.
Preferably, all three connections for pivotal movement inclu~e
said cyllndrical cross pins and ob-round holes.
In order to provide automatic.shifting on demand from
pivotin~ to rolling modes of operation, my tool may preferably
include, at each pivot site, spring biasing means biasing said
cylindr cal cross pin to one end of said ob-round hole when sai~
tool is in the open position, said one end being opposite an end
lQ a' which said cross pin is located when said tool is in the
closed position after having formed a work piece positioned
be'~een said mating sur'aces of said first and second die
.embers.
In one embodiment, the anti-reversing means co~prises (a) a
first elongated bar having a longitudinal axis in the direction
of the lon~i.tudinal axis of said chassis member and having one
end pivo~ably attached to said chassis me~ber at a point spaced
a distance from said second die mem~er and a lesser distance
from said second pivot site; (b~ a second elongated bar having a
longitudinal axis parallel to the longitudinal axis of said
first bar and having one end pivotably attached to said first
to~gle arm me~ber at a point ~et~een said first and third pivot
s'.' es; (c) said first and second bars each having a longitudinal
s~rface, at least a portion of said longitudinal surface of said
~5 ri~ ar be ng in con-act wi~h at least a portion of sai~
Hadden - 7
57;~
longitudi.;lal surface of said second bar for sliding movemen. of
said bars relative to each other in the direction of their
longitudinal axes, one of said longitudinal surfaces including
an enlongated recess in the longitudinal directîon, said recess
being of uniform depth except for a generally V-shaped
transverse wedge protruding toward the other longitudinal
surface at the longitudinal center of said recess, the other
said longitudinal surface including two transverse spaced apart
depressions; (d) means for limiting sliding movement of said
first and second bars relative to each other so that said
elongated recess is always opposite either one of said
transverse depressions or the portion of said other surface
between said transverse depressions; ~e) a rolling member having
circular transvers~ cross section of predetermined diameter D3
and radius R3 positioned within said elongated recess in said
one longitudinal surface and in contact with a point on said
other longitudinal surface; (f~ spring biasina r.eans within said
elongated recess tending to maintain said rolling member in
contact with a surface of said V-shaped wedge; and (g) means for
maintaining said portions of said longitudinal surfaces in
slidina contact and retaining said rolling r,er.~er and spring
biasing means ~lithin said elongated recess, wherein the distance
between said other longitudinal surface and the tip of said
V-shaped wedge is less than D3, the distance between said other
longitudinal surface and the deepest surface of said recess is
Hadden - 8
~Z~ 7~
greater than D3, and the distance from the deepest surface ~
each of said spaced apart depressions to the tip of said V-shaped
wedge is greater than D3 when said V-shaped wedge is opposite
said depression.
In a preferred embodiment, the anti-reversing means com-
prises (a~ a first e]ongated bar having a longitudinal axis in
the direction of the longitudinal axis of said chassis member
and having one end pivotably attached to said chassis member ~t
a point spaced a distance from said second die member and a
lesser distance from said second pivot site; (b) a second
elongated bar having a longitudinal axis parallel to the longi-
tudinal axis of said first bar and having one end pivotably
attached to said first toggle arm member at a point between said
~irst and third pivot sites; (c) said first and second bars each
having a longitu~inal surface, at least a portion of said
lonqltudinal surface of said first bar being in contact with at
least a portion of said lonyitudinal surface of said second bar
for sliding movement of said bars relative to each other in the
direction of their longitudinal a~es, one of said longitudinal
surfaces including an elongated recess in the longitudinal
direction, said recess being of uniform depth except for a
generally V-shaped transverse wedge protruding toward the other
longitudinal surface at the longitudinal center of said recess,
the other said longitudinal surface including a series of
adjacent transverse scallop-like depressions, each of said
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572
depressions except those at each end of said series being of
generally arcuate contour, each pair of adjacent depressions of
said series meeting at a peak, all said arcuate depressions
being of substantially equal depth, the depression at each end
of said series being wider in the longitudinal direction and
deeper ~han said arcuate intermediate depressions; (d) means for
limiting sliding movement of said first and second bars rela.ive
to each other so that said elongated recess is always opposite
at least a portion of said series of depressions; (e~ a rolling
member having circular transverse cross section of predetermined
diameter D3 and radius R3 positioned within said elongated
recess and in contact with a point on the surface of said series
of depressions; (f) spring biasing means within said elongated
recess tending to maintain said rolling member in contact with a
surface of said V-shaped wedge; and (g) means for maintaining
said portions of said longitudinal surfaces in sliding contact
and retaining said rolling mel~ber and spring biasing means
within said elongated recess, wherein the distance from the
deepest point of each said arcuate intermediate depression to
the tip of said V-shaped wedge is less than D3 when said V-shaped
wedge is opposite said arcuate depression, the distance from
said peak between any two of said depressions to the deepest
surface of said recess is greater than D3 when said peak is
opposite said deepest surface, and the distance from the deepest
surface of each said depression at each end of said series to
Hadden - iO
~2i6~l57~
the tip of said V-shaped wedge is greater than D3 when said
V-shaped wedge is opposite said end depression. In this embodi--
ment I prefer that (a) the depth of each said arcuate depression
is about 0.1 D3 and Ib) the curved surface of each said arcuate
depression has a radius of curvature equal to from R3 to about
1.1 R3 and subtends a predetermined angle of A degrees. In
order to totally prevent reverse movement I may provide that the
included angle between the sides of said V-shaped transverse
wedge be at least [180 - 2 (A/2 + Arc Tan C)] degrees, where C
is the coefficient of sliding friction between the surface of
said wedge and the surface of said rolling member.
The output force of a tool according to the invention is
determined by the work required to be performed and can be
charted as a curve of output force vs. tool movement (or work-
lS piece deformation). In the case of forming a rivet head, such a
curve will sweep upward exponentially as the area of the rivet
head increases during the heading operation. In the case of
- crimping a sleeve upon the end of a wire, the connection being
formed is confined within a crimping nest which prevents growth
of area; hence, the force curve will increase substantially
linearly until the material of the workpiece deforms to fill all
interstices. At this point, the pressure will equal the compres-
sive strength of the materials being joined. The output force
c~rve will then level off as slight continued compression causes
the workpiece material to extrude slightly out of the crimping
Hadden - 11
5~
nest resulting in a reduction of cross-sectional area of the
workpiece. For the purpose of this disclosure, the output force
curve will rise abruptly as the orming die impinges upon the
workpiece, and will continue to rise in a straight line upward
slope terminating in a short level extension representing the
compressive limit of the workpiece materials. Using known force
relationships a toggle coeficient can be calculated for each
de-r~en_a s~ep (abscis~a3 of ~ he diminishing toygle arm~ ~c
the output force at each abscissa is divided by that abscissa's
toggle coefficient and the resulting value marked upon the same
abscissa according to a selected reduced force scale, an input
force curve can be plotted. Such a plot shows that a peak input
force occurs intermediate the curve ends and diminishes there-
after (similar to a trajectory curve) although the output curve
continues upwardly. The peak input force may be arbitrarily
established or it may be subjectively judged to be within
acceptable limits. In either case, a linkage can be developed
to satisfy the desired output/input ratio. The forces on the
abscissas for the input peak and the output maximum are pertin~
ent for s.ress and vector analysis of the ascociated tool
elements and functions.
The toggle coefficient is not pursued to infinity, i.e.,
the toggle linkage is mechanically stopped before its pivot
points come into straight alignment.
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72
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings,
Fig. 1 is a side elevation, with portions cut away for
clarity, of a plier type crimping tool in the full open position
showing one embodiment of a toggle linkage according to the
invention;
Fig. 2 is a side elevation of the tool of Fig. 1 showing
the tool partially closed with the crimping heads in position to
impinge upon a workpiece;
Fig. 3 is a side elevation of the tool of Fig. 1 showing
the tool in the fully closed position wherein the toggle linkage
produces its maximum force;
Fig. 4 is a bottom view of the tool of Fig. 3 taken along
the line 4--4 of Fig. 3 and illustrating the nesting relation-
ship of various tool components;
Fig. S is a side interior elevation of another fully open
plier type crimping tool embodying a toggle linkage according to
the invention and including a novel anti-reversing ratchet
assembly;
Fig. 6 is a side interior elevation of the tool of FigO 5
showing the tool in nearly closed position just as a kick-open
spring transiers its tip bearing ~rom the toggle ~t-ut to -~he
edge of the sidewall;
Fig. 7 is a side interior elevation of the tool of Fig. 5
in its fully closed position wherein the toggle linkage produces
its maximum force according to the invention;
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~6~%
Fig. 8 is a bottom interior view of the tool of F;g. 7
taken along the line 8- 8 of Fig. 7., illustrating the nesting
relationships of various tool components and the relation of the
kick-open spring to the toggle strut and chassis sidewall edge;
Fig. 9 is a simplified diagram of a basic unequal arm
toggle in normal orientation, and is included for illustrative
purposes in connection with calculations discussed hereinbelow;
Fi~ is a sim~li~ e~ ~iiagram of a toggle '~a ~,e ~c-~o~'-
ing to the invention with force and dimensional elements identi-
fied for deriving data pertinent to the invention;
Fig. 11 illustrates an output/input force relationship
curve in a toggle according to the invention.
Fig. 12, 13 and 14 are partially cut away side views of
three different positions of a novel alternate anti-reversing
ratchet assembly similar to that in the tool of Figs. 5 through
8.
DETAILED DESCRIPTION OF THE PREFERRED E~BODIMENTS
With more particular reference to the accompanying draw-
ings, in which like numbers refer to like parts, Figs. 1 through
4 illustrate a crimping tool according to the invention. The
tool has a ch-;-.nel form chassis member 2 ;~a~i~g f_~ed ~i.hin it
another channel form me~ber 3 the web 4 of which cooperates with
chassis member 2 to form a rectangular section tunnel 5 with
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4S72
near and far sidewalls 6. A crimping head holder 7 is fixed
within the end portion of tunnel 5 by means of a hardened pin 8
press fitted in chassis member 2; pin 8 also passes through an
ob-round hole 9 in the "C~ frame end 10 of handle member 11,
pivotally ,etairing the end lO within tlle clevis 12 of holder 7.
A rectangular tunnel 13 is a continuation of tunnel 5 having
been in~errupted by cutout portion 14, 15. A slidable crimping
head holder 16 is positioned within tunnel 13 and pivotally
connected at its clevis portion 18 to one end of toggle strut 17
by means of hardened pin 19 through an ob-round hole 20 in strut
17. The other end 21 of strut 17 is pivotally connected in the
clevis portion 22 of handle 11 by means of another hardened pin
23 press fitted in handle 11 but pivotally operative in strut
end 21 through ob-round hole 24. Upstanding flanges 25 of
chassis channel 2 prevent entrapment of a worker's fingers
thereby guarding against injury. A fixed crimping head 26 is
fastened to fixed holder 7 by means of screws 27 which may
protrude through chassis sidewall 6 as shown in Fig. 4. A
movable crimping head 28 is fastened to slidable holder 16 by
means of screw 29. Crimping heads 26 and 28 cooperate, when
fully engaged, to deform a wire inserted in the wire barrel of a
wire terminal so that a secure attachment is permanently pro-
duced between the wire and its terminating piece. The crimping
heads 26 and 28 could be integral with the holders 7 and 16, but
t~e arrangement shown permits interchangeability OI crimping
Hadden - l5
S72
heads and also allows adjustment with shims if necessary. The
web 4 of inner channel part 3 does not extend to either end of
the part 3 so as to avoid interference with the IlC~ frame
portion 10 of handle ll and the end 30 of toggle strut 17. The
remainina sidewall extensions 31 and 32 provide positioning for
holder 7 and tracking guidance for slidable holder 16. A
staple-like wire loop 33 is fixed near end 30 of strut 17 to
serve as an anchor point for one end of a return coil spring 34
The other end 35 of the spring is anchored by means of a cross
pin 36 press fitted in holes in the sidewalls of chassis 2. At
the nose of the tool 1 a bowed leaf spring 37 is held in posi-
tion by tab 38 engaged in hole 39 in chassis 2. At the tail end
21 of toggle strut 17 another bowed leaf spring 40 is held in
position by means of screw 41 and rectangular washer 42. Near
the center of the tool a coil spring 43 has one end attached to
a sprag 44 pivotally mounted on pin 45 in sidewall 6 of chassis
2; the other end of spring 43 is anchored by pin 46, also flxed
in the sidewall 6 of chassis 2. Spring 43 urges the sprag into
frictional engagement with a true arcuate edge surface 47 which
is part of handle 11. The arc of surface ~7 is described about
the center of pin 8. It will now be noted that the bias springs
37 and 40 and the biasing effect of the return spring 34 serve
to position the ob-round holes 9, 20 and 24 in the off-center
relationship shown with their respective pivot pins 8, 19 and
Hadden - l6
72
23~ This off-center relationship will be maintained and pins 8,
19 and 23 will slip, as in a sleeve bearing, while the tool is
closing under a no-load condition and until crimping head 28
impinges upon a workpiece positioned within crimping head 26
At impingement, an increasing bearing load begins to occur
between pins 8, 19 and 23 and their respective ob-round hoies 9,
20 and 24. When this bearing load becomes great enough to
overwhelm the biasing capability of leaf springs 37, 40 and the
geometrically diminishing bias effect of coil spring 34, pins 8,
19 and 23 develop traction within their ob-round holes 9, 20 and
24 and the relative turning motion is transferred to rolling
rather than slipping. Thus, an increasing load on the toggle
linkage causes the mode of operation to transfer automatically,
upon demand, from a pivotal to an almost frictionless rolling
mode. With this feature a much greater rolling load capacity is
provided by the relatively large diameter pins 8, 19 and 23 than
could be provided by needle bearings surrounding the same
diameter pins, as the capacity with needle bearings would be
limited by the basic dynamic capacity of the needle bearings.
It will be evident that the initiation of the pivot "rolling
action on demand" is related to the tension of the bias springs
that bias the pivot pins to the primary ends of the ob-round
holes; i.e., the greater the bias tension, the later the rolling
action starts and the less rolling action takes place.
Hadden - 17
~f~
~eferring now to Fig. 2, it will be noted that partial
closure of the tool 1 has closed the crimping heads 26, 29 such
that a wor~piece would be captive in their qr-p. At this point
the tool has not yet undergone its transfor~ation from pivotal
to rolling mode as witnessed by the same pin/ob-round hole t8,
9; 19~ 2Q; 2~, 2~) relationship as appeared in Fig. 1. ~t will
also be noted that the sprag 44 has assumed an angular position
dicta`ed bv its engagement with the arcu~te edge element 47
which has swuno into its present position 2S the tool ~ecame
?ar_ial~y close~. The angle that sprag 44 ~.akes with a ra~ius
of ~rc ~7 is the "pressure angle" and is shown here exaagerated.
As is well-known in the art, in order to have a zero back-lash,
non-slip sprag function the pressure angle must be arranged so
that its tanaer.~ is equal to or less than the coefficient of
riction ~etween the associated parts 4~ and 47 (the contacting
sur,aces of 44 and 47 are preferably hard enough to resist
brinelling and ~ear). By choosing a pressure angle with a
tanqent slightly above the coefficient of friction, a reversing
sprag function can be obtained in which the moving surface 47
sli~s very easily in one direction - e.g. the direction of too'
closure b~-' w ~h cor.siderable difficulty in the reverse ~irec-
tion - e.s. 'he di-ec'ior. of tool open ng Tn the position
s~Awn in Fia. 2, he s?raa se~ves the desired $unction of
nC~r no co~?le,e tool closure - i.e., cer.ifies a valid cri~ -
2'~ wh-le still a' lowing the tool to be forced o?en without da~ase
Hadden - 18
should it be necessary to remove a mal-positioned workpiece. In
use a crimping tool is normally completely closed for each crimp
and the sprag function, though present, is not noticed. The
sprag comes into play only if the tool operator fails to complete-
ly close the tool. An alternative reversing ratchet sometimes
used in prior art crimping tools includes a spring-centered pawl
cooperating with a toothed rack; this arrangement, which cannot
be forced open without damage to the parts, is also commonly
used in vending machine coin slide mechanisms.
Fig. 3 shows the tool 1 completely closed. The l'C" frame
10 is just deep enough to clear the inside web of channel 3.
During the final closing phase, the following events occur:
handle 11 stops at pin 36 preventing the centers of pins 8, 19
and 23 from coming into common alignment; crimping heads 26 and
28 achieve their design closure so as to complete the prescribed
crimp upon a workpiece; the spring centered reversing sprag 44
completes its traverse of arcuate surface 47 and, at closure,
assumes a centered position from which it will take a position
opposite that of Fig. 2 on opening the tool and thus allow the
tool to be opened easil~l; bias springs 37, 40 and the biasing
effect of spring 34 are overcome by the traction of ob-round
holes 9, 20 and 24 rolling upon their pins 3, 19 and 23 as
demonstrated by the deflection appearing in leaf spring 37; and
very importantly, the pin-slot rolling action actually takes
place as cle~onstr~te~ by the slot end clear~ce ~i~rations to
Hadden ~ 19
i72
the opposite sides of pins 8, 19 and 23. An added interesting
feature of the tool of Fig. 1 is that return spring 34 extends
only slightly throughout the entire closure, indicating that it
can be a high rate (heavy preload) spring with low rate (small
active deflection) characteristics to insure against fatigue.
Fig. 4 shows the clevis arrangement of th~ "C" frame element 10
of handle 11 disposed within clevis 12 of crimping head holder
7, the disposition of end 30 of toggle strut 17 within the
clevis portion 19 of slidable crimping head holder 16, and the
straddling relationship of the sides of handle 11 with the other
end 21 of toggle strut 17. It can also be seen that the mount-
ing screws 27 of the fixed crimping head 26 extend through the
wall 6 of chassis 2 tand could even protrude more should it
become desirable to mount a crimped workpiece alignment fix-
ture); however, mounting screw 29 of the movable crimping head
28 cannot protrude beyond the surface of head holder 16 because
if it does protrude it interferes with the reciprocating motion
of head holder 16 within the tunnel portion 13 of chassis 2 in
combination with fixed wall 4 of channel member 3. Although not
shown as such, members 2 and 3 may be fixed to each other by
means of riveting, spotwelding, soldering, brazing, or the like.
Referring now to Figs. 5 through 8, there is shown another
preferred embodiment of a toggle operated tool designated
generally 51, which uses the same basic toggle linkage system as
,
}7adden - ~0
i72
the tool described in Figs. 1 through 4. In this embodiment,
however, a trade-off has been made; instead of having the head
pin positioned in an ob-round hole where rolling action can
occur, the pin pivots in a hearing bore with an automatic
5 lubrication replenishment system described later. The tool of
Figs. S through 8 has a channel form chassis member 52 with
upstanding sidewalls 53 and 54. Fixed within chassis 52 is
channel form member 55 having upstanding sidewalls 56 and 57 in
faying relationship with 53 and 54. The channel assembly just
described is pivotally fastened in opposed relationship to a
shell form member 59 by means of a hardened pin 58~ Shell form
member 59 has sidewalls 60 and 61 and end wall 62. The near
sidewalls 53 and 57 are coped out as shown at 63, 64 to accept,
in nesting fashion/ a control linkage 65 more fully described
later. The sidewalls 60 and 61 are coped out at 66 and 67 to
form a "C" frame member. The depth of this coping need only
clear the widest workpiece with which the tool is to be used and
the coping is thus shallower than the coping in member 10 of the
tool of Figs. 1 through 4. This shallow "C" frame 66, 67 allows
~0 member 59 to be lighter than "C" frame 10 of Figs. 1 through 4
while having equivalent strength. In order to avoid having ob-
round holes in the head end of sheet metal "C" frame ~here they
would be vulnerable to the entrance of foreign particles, and
findinq that it may be impracticable to trans~ose the pin-slot
function into the ~ixed crimping head holder 68 because of a
l3adden - 21
7~
spring biasing problem, a trade-off was adopted. The hard pin
58 is press fitted int~ "C" frame area 60', 61' of shell 59 and
has a running fit with a hole 69 through holder 68. Note that
the bearing area in holder 68 is not diminished by a clevis _ut
and therefore provides a generous area for the lubricated pin 58
to bear upon. To lessen the compromise of the tr~de-off, an oil
hole 70 is provided and i5 filled with an oil saturated felt
wick 71. A leaf spring 72 covers the oil hole 70 and also uraes
pin 58 against the unloaded sidewall ~9' of hole 69 so that the
lubrication film that is present is automatically displaced to
the opposite (work load) side of the bearing hole whenever the
tool is unloaded. Thus, the bearing is relubricated on its load
bearing surfaces prior to each work cycle. Although the load is
heavy, the durability of the hardened parts should be satisfac-
tory since the rotary motion (surface velocity~ is very slow and
the angular displacement (peripheral travel) is short. Of
course, an alternative to the lubricated head bearing and pivot
pin may be to fix the head pin against rotation in the handle
shell and to provide an ob-round slot through the frame and
stationary ~rimping head holder (block) for the pivot pin to
roll in when rollinq is initiated by the demand of the workload.
As the head pin rolls in the ob-round ~lot, the toggle linkage
geometry changes slightly and, in effect, experiences an imper-
ceptible decrease in force multiplication.
Hadden - 22
12~;~S72
~,prin~ 72 is retained in place by its engagement over a
cross pin 73 press fitted in holes in sidewalls 60 and 61 of
shell member 59. Channel 55 fixed within channel 52 provides a
rectangular section tunnel 74 which houses a fixed crimpi~g ~^32
holder 68. A crimping head 75 is mounted to holder 68 by means
of screws 76 which pass through but not beyond sidewall 54 of
chassis 52, as seen in Fig. 8. A slidable crimping head holder
78 reciprocates within tunnel 74, and a crimping head 77 is
mounted to the s].idable holder 78 by means of screw 79. Crimp-
ing heads 75 and 77 are shown as inserts but could, alterna-
tively, be integral with the holders 68 and 78. The back end of
the slidable holder 78 has a clevis portion 80 to cooperate with
end 81 of toggle strut 82 in a pivotal manner by virtue of
hardened pin 83 in ob-round hole 84. The pin 83 may be a light
push fit in holes 85 in clevis portion 80 of toolholder 78 (Fig.
8). Near one end 81, strut 82 holds a staple-like wire loop 86
to engage the extended end hook 87 of a return (tool opening)
spring 88. The other end 89 of spring 88 is hooked around a pin
90 press fitted in holes in sidewalls 56 and 57 of chassis 52.
The other end 91 of toggle strut 82 is pivotally conr.ected to
the shell 59 in handle zone 92 by means of another hardened pin
58 press fitted in holes in the side walls of handle zone 92 and
passing through an ob-round hole 93 in end 91 of strut 82. At
end 91, strut 82 is centrally located between the sidewalls
Hadden - 23
60 and 61 of shell 59 by means of tubular spacers 94. A "kick-
open" hairpin spring 95 partially surrounds and is thereby
anchored upon one of the spacers 94. Also, at end 91 of strut
82 there is another staple-like loop 96 which engages one end 97
of a bias spring 98; the other end of spring 98 is anchored to a
cross-pin 99 press fitted in holes in the sidewalls 60 and 61 of
the shell ? S handle portion 92. As shown in Fig. 8, the working
end of hairpin spring 95 is shaped into hook 100, the straight
end 101 of which extends to the inner surface of sidewall 61 so
as to overlie the edge of sidewall~54 for a purpose to be
described later.
A reversing ratchet control linkage 65 includes a flat bar
lOq with an offset end 105, a short extension bar 107 and a
channel-form cage member 106 fixed to bar 107. The o~fset end
105 of bar 104 is pivotally secured to sidewalls 53 and 54 of
chassis 52 by means of cross pin 103 pressed into holes in the
sidewalls, while the end of bar 107 is pivotally secured to
sidewalls 60 and 61 of shell 59 by means of cross pin 102
pressed into holes in those sidewalls. Bar 104 slip fits
through the channel form cage member 106 in sliding relationship
to the extension bar 107. Bar 107 has an elongated recess 108
in the portion of its one edge within cage 106, and the recess
108 has a raised transverse "VEE" wedge 109 at its midpoint. A
sprag roller 110 and centering springs 111 are positioned within
recess 108, the spring serving to position roller 110 in the
7ladden - 24
~6~7~
center of recess 109 whenever one of notches 112 and 113, out in
the faying edge 114 of bar 104, is opposite the protuberant
wedge 109. Notches 112 and 113 axe so spaced on bar 104 that
the described centering action occurs at each end of the tool
stroke as occasioned by the telescoping in and out of bar 104
through cage 106. Excessive extension (tool openin~) is prevent-
ed by a shoxt protruding cross pin 115 in the free end 116 of
oar i0~ n of~center hole 117 in one side of caqe 10~ permits
easy assembly and disassembly of the sprag roller 110 and its
centering springs 111.
Fig. 5 shows the tool 51 in wide open position as limited
by the pin 115 or ratchet control linkage 65. In use, a work
piece (not shown) is located within the shaped recess 118 in the
fixed crimping head 75 and the tool is closed until the movable
crimping head 77 g~ntly touches and captures the workpiece
within recess 118. After a stripped wire to be terminated Inot
shown) is inserted and held in place in the workpiece the tool
is closed until the chassis edges 119 are stopped against the
tubular spacers 94 (Fig. 7). As the tool is closed the follow-
ing events occur: bar 104 slides through cage 116 and its notch
112 will move the sprag roller 110 away from its central posi-
tion and against one of its centering springs 111. Once this
happens, the motion cannot be reversed (allowing the tool to
open prematurely) until closure is complete because such reversal
would immedia~ely cause sprag roller 110 to wedge aaainst one
Hadden 25
~2~72
slope of the wedge 109 thus effectively locking the action. In
order for this zero-backlash, non-slip wedging action to occur,
the tangent of the pressure angle between the roller 110 and the
wedge 109 must be equal to or less than the coefficient of
riction between the- har~ened parts. The closing action con-
tinues under practically a no-load condition until crimp head
77 impinges upon the workpiece. During this phase, bias sprln~
98 and the biasing runction of return spring 88 hold the pins 58
and 83 in the relationship shown in Fig. 5, with pin 83 at one
end of ob-round hole 84 and pin 58 at one end of ob-round hole
93; in this phase of operation pins 83 and 58 simply rotate
lightly at one end of their respective ob-round holes ~lubrica-
tion, low speed, no load, no wear). During the same phase, the
hairpin "kick-open" spring 95 is subject to gradual loading by
~irtue of its engagement over toggle strut 82; the third order
leverage in this action is so great that the spring loading
effect at handle 92 is virtually imperceptible. ~hen the
movable crimp head 77 impinges upon the workpiece, the second
phase of motion begins and the tool experiences a work load.
This loading is felt at the togale pivot pins 58 and 83 result-
ing in traction in the ob-round holes 84 and 93 so that from
here on the pivoting action in these holes is purely a rolling
action. The bearing surfaces of the ob-round holes are hardened
by known means to minimize rolling friction and wear. On
experiencing the working load, the small clearance bet~een the
~adden - 26
7;~
pin 58 and its bearing bore 69 is transferred from one side of
the pin to its opposite side against the resistance offered by
bias leaf spring 72; it is at this time of hole clearance
transfer that the above-mentioned hole relubrication feature
functions~
Fig. 6 shows the tool at nearly closed position. It will
be noted that the pin/ob-round hole relationships have already
reversed indicating that the purely rolling action is in pro-
gress. At the point shown in Fig. 6, tip 101 of hairpin spring
95 has its bearing transferred from strut 82 to the upper edge
of sidewall 54, where it can exert its full force to kick the
tool open once the full closure has been achieved and the
operator's grip has relaxed. The transfer of spring tip lO1
occurs so late in the action that the tool's peak squeezing
force (input curve) has long since been passed; thus the late
additive effect of the spring 95 is negligible and the descend-
ing end of the input curve stays well below its aforementioned
peak. An additional feature of the dual engagement of spring 95
between strut 82 and sidewall 54 is that spring 95 never emerges
from the protection of handle zone 92 and is thus not exposed to
snagging or damage.
Fig. 7 sho~s the tool at full closureO The sprag roller
110 is recentered within notch 113 in bar 104 so that tool
opening can now take place and the completed worX piece removed
from the tool. During opening of the tool, bias leaf spring 72
Hadden - 27
i;72
retrans)-ers the hole clearance at pin 58 and relubrication
occurs. Also, the hairpin spring tip 101 transfers from ~he
edge of wall 54 back onto the strut 82 and its spring effect is
accordingly diminished by the third order leverage of strut 82.
Fig. 8 is an upward looking internal plan arrangement
showing the interrelationship of the parts and the broad uninter-
rupted bearing surface of hole 69 which appears in hatched
lines. The hardened pin 58 may be pressfitted into the
sidewalls 60 and 61 of shell 59 as shown or it may be fitted
with spring retaining rings in suitable grooves.
Figs. 12, 13 and 14 show in three positions a novel pre-
ferred ratchet control linkage 165, the overall dimensions,
parts and connecting relationships of which correspond to those
of linkage 65 shown in Figs. 5 through 7. h~en used in tool 51
of Figs. 5 through 7, linkage 165 is mounted on pins 102 and
103, which are shown in Figs. 12 through 14 for reference. It
will also be noted during the following description that many of
the features of linkage 65 appear in identical form in linkage
165.
The linkage 165 includes a flat bar 204 which has an offset
end 205 and a series of scallop-like trans~erse depressions,
including deep depression~ 212, 213 and sh2110w intermediate
arcuate depressions 221, cut into its faying edge 214. Bar 204
slip fits through a channel form cage member 206 which is fi~ed
to and encloses a short extension bar ~07. Pin 215, inserted
~adden - 2~
ii72
through end 216 of bar 204, prevents the bar from sliding out of
cage 2Q6 and also limits the extension of linkage 165. Bar 207
has an elongated recess 208 in its inner edge; at the midpoint
of the recess is a raised transverse "VEE" wedge 209. A roller
210 and centering bias springs 211 are positioned within the
recess 208. When the arcuate depressions 221 are opposite the
wedge 209 (see Fig. 13), the roller 210 cannot pass under the
~VEE". However, when one of the deep depression~ 212 and 213
comes opposite wedge 209 5see Figs. 12 and 14), the roller 210
can underpass the wedge, thus allowing a reverse travel of the
bar 204 through cage 206. It is preferred that the springs 211
be at their free length (no preload) when roller 210 is centered;
in fact, the springs 211 need not actually touch roller 210 at
that point. With this arrangement travel reversal can occur
only at the fully extended or contracted modes of linkage 165,
i.e. at stroke completion. As was the case with linkage 65,
this insures that the tool 51 cannot be reopened until it has
fully compressed a workpiece in the tooling recess 118 to its
specified size.
When the linkage is telescoping in one direction, roller
210 bears against one of bias springs 2110 The sprins ~ields to
allow the roller to cam from scallop to scallop 221; thus, a
stepping ratchet obtains. In the event of an attempted stroke
reversal when the roller is over an arcuate depression, the bias
Hadden - 29
spring causes the roller to jam immediately between the wedge
and whichever depression is under the roller at the time.
Holes 217 in the sidewalls of cage 206 permit installation
and removal of roller 210 and springs 211. Smaller holes 220
opposite holes 217 admit a probe tool (not shown~ to eject the
roller 210 if necessary for disassembly.
Calculations and experiments with the linkage of Figs. 12
through 14 have shown that, given a diameter D3 and radius R3 of
roller 210, the following relationships can be stated:
(a) The preferred relative dimensions for the arcuate
depressions 221 are depth about O.lD3 and radius of curvature
R3 to about l.1 R3; with these relative dimensions each
depression subtends an angle A of about 76 to 80 degrees.
(b) In order to totally prevent unwanted reversal,
i.e. to cause the roller 210 to jam immoveably if reverse
mOVelTlellt i5 attempted, the angle included between the sides of
the "VEE~ wedge 209 must ~e at least 1180 - 2 ~A/2 ~ Arc Tan C)]
degrees, where A is the angle subtended by each of the arcuate
depressions 221 and C is the coefficient of friction between the
surface of wedge 203 and the surface of roller 210. Smaller
included angles will allow reversal of movement, albeit with
much greater effort than movement in the for~ard direction.
Fig. 9 is a basic diagram of classic unequal arm toggle
mechanics, in which F2 represents input force, P2 represents
output force (more precisely, reaction to output forces) and the
~ ~adden - 30
~7~6~
relationship between the twv is shown in the formula for P2 set
~orth. The basic rel2~iollsnips of Figs. 9 w~re used to derive
the information shown in Fig. 10, which illustrates and applies
to crimping tools embodying toggle linkages according to the
invention. In Fig. l0, P represents the output or crimping
force resulting from application of input force Fl, to the grips
or handles of the crimping tool. Also, in Fig. 10, as in Fig.
~, ~he toggle coefficient is equal to aa/bb.
Referring to Fig. 10, two short "extension leverage" arrows
will be seen emanating from the tip of arrow "Fln. One arrow is
normal to an extension of leg l~n and the oiher is nor._l o an
extension of leg "c". The extended arrow of "Fl" bisects the
angle formed by the aforementioned short arrows and intersects
an extension of leg "b" at a point spaced from the apex of angle
"A" by a distance equal to that between "Fl" and the apex of
angle "An. It is assumed that the "grip points" of any plier-
like tool are preferably equidistant from the pivot point.
Sides l'b" and "c" (handles) may be extended as desired to
increase the input leverage.
When the size of product being crimped or staked and the
force required to properly perform the desired work are known,
along with basic dimensions of the toggle linkage being used
~e.g. leg lengths a, b and c), 'igs. 3 and 10 ~nd their
associated formulas can be used to develo~ force/displacement
curves such as are shown in Fig. 11. Fig. 11 is a plot of
- I ", ., ., . ., .. ", ', J .J ~
Hadden - 31
~fi~7~
foxce/displacement obtained from one crimping tool according to
the invention. It should be noted in Fig. 11 that the length of
arm "b~ decreases as crimping progresses - i.e. as the distance
between crimping heads ~e.g. 26 and 29 in Fig. 1) decreases.
In Fig. 11, dividing the output force at any abscissa by
the toggle coefficient for that abscissa results in a figure
equal to the input force for *hat abscissa, which can then ~e
entered as a point on the input curve. After input force values
for a number of abscissa have been so derived, an input curve
can be plotted. For the tool to which Fig. 11 applies it will
be noted that peak input force occurs just past the midpoint of
the input curve; it is thus apparent that a late acting "kick-
open" spring force of, for example, two pounds more or less will
not he significant during the latter descent of the curve.
Selection of dimensions and materials for tools according
to the invention is deemed to be well within the purview of
skill in the art and is based on the size of -the tool, the force
necessary to properly crimp and the linkage functional require-
ments discussed above. In designing and fabricating a crimping
tool according to the invention, toggle arm lengths are
established for the appropriate series o~ coefficients to deal
with the given output force requirement. The stroke from open
to closed position must provide adequate opening space to admit
the given workpiece and the tool should have a "handle-open"
span small enough for a comfortable hand grip. Desirably-the
Hadden - 32
;i7;~:
angles ~ , "B" and the complement of "C" ~Fig. 10) are noted at
the instant when the load induces traction in the ob-round pivot
holes, and rolling displacement can then be made equal in
degrees to angular displacement at the respective pivots.
Rolling, sl dincj and st~tic bearing pressures and stress analysis
of all elements may be calculated for each linkage considered in
order to verify its validity. The return (opening) spring
should be so sized that it does not itself induce enough loadina
to overcome the bias springs' function and initiate premature
pivot traction. Finally, the relubricaton featuxe of Figs. 5
through 8 can if necessary be used at one or all of the toggle
pivot joints. All such considerations are deemed to be within
the skill of a competent mechanical design engineer and are
therefore not discussed in detail here.
While I have shown and described certain present preferred
embodiments of the invention, it is to be distinctly understood
that the invention is not limited thereto, but may be otherwise
variously embodied within the scope of the following claims.
