Note: Descriptions are shown in the official language in which they were submitted.
;6
BACKGROUND OF_TIIF INVENTION
This invention relates to a tool Eor the installation
of items that require tensioning and mor~ particularly to a tool for
the installation o~ fas-teners such as cable ties.
Cahle tie fasteners are commonly installed, for example,
by wrapping their straps around groups of artlcles and then threading
the straps -through locking heads. The ins-talla-tion is completed by
pulling on the free ends of the straps until l,he articles are
securely bundled. To achieve a suitable installation i-t is desirable
to use a tool which grips and tensions the free end of the strap.
The free end is then se~-ered in the vicinity oE the head when a
specified level of tensioning has been reached.
Installatio~ tools in common use contain a trigger
actuated mechanism that tensions the strap to a predetermined level
and actuates a cutter to sever the strap.
Such tools commonly require the application of a
relatively high operating force to the trigger through an appreciable
interval. In some cases there is a considerable span between the
hand grip of the gun and the trigger. The result is that the tools
can be difficult to operate and can cause undue user fatigue.
Another characteristic of existing installation tools
is that the cutoff mechanism produces a significant shock effect.
At the instant of severing there is a pronounced snap which, at high
tension levels, can even sting the user. In addition there is the
ob~ectionable tendency for the severed end of the strap ~o be ejected
from the tool towards the user. Another objection is the tension
level adjusting mechanism is often unreliable and difficult to
operate.
According to one broad aspect, the present invention
relates to an installation tool comprising: a tensioning member;
an actuator mechanism including collapsible tensioning links; a sever
mechanism; and means for operating said tensioning member through
said links of said actuator mechanism while maintaining said
colIapsible tensioning links in relative alignment until a prescribed
level of tensioning is applied to said member, whereupon said links
collapse and operate said sever mechanism and thereby said tool.
According to another broad aspect, the present
invention relates to an installation tool comprising: a
: ~ - 2 ~
~: i . ' : .''
. .
7~i6
t isi~ning member; an ac-tua-tor mechanism including collapsible
tensioning links forming a pivoted toggle connected to saicl
tensioning member; said toggle constit~lting a fi.rs-t link member
pivotally connected to said tensioni.ng member; and a second link
member pivotally connec-ted to said first link member and operable
from a tri.gger source; and means for applying force to the pivotal
connection of said first link member with said second link member and,
thereafter, applying fur-ther force to said tr:Lgger source whereupon
said links collapse and operate said sever mechanism and thereby said
tool.
Illustrative installation tools of the prior art are
disclosed in U. S. patents 3 ~ 735 / 784; 3 ~ 712 / 346; 3 ~ 661~ 187;
3~433/275; 3~344~815; 313321454; 3/284~076; 3~173~456; 3~169~560
(Re. 26~492); 3~168~119; 3~154~114; 2~72~r994; 2~882~934; and
2 ~ 175 r 478.
DESCRIPTION OF T~IE DRA~INGS
Other aspects of the invention will become apparent
after consid~ring various illustrative embodiments, taken in
conjunction with the drawings in which
FIG. 1 is a perspective view of a tool in accordance
with the invention being used in the installation of a cable tie;
FIG. 2 is a perspective view of the tensioning and
sever mechanisms in the installation tool of FIG. l;
FIG. 2B is a schematic represen-tation of the tensioning
and severing mechanisms of FIG. 2A during tensioning;
FIG. 2C is a schematic representation of the tensioning
and severin~ mechanism of FIG. 2A during severing;
. FIG. 3A is a perspective view of a compression spring
cage for the adjustment of tension in accordance with the invention;
~30 FIG. 3B is a perspective view of the interior of the
cage oE FIG~ 3A;
FIG. 4A is a view of the installation tool of FIG. 1
with portions broken away to show the placement of constituents
- pictured in FIGS. 2A through 3B;
: FIG. 4B is an end view of the tool of FIG. 4A, and
E`IG. 4C is a top view of the tool of E`IG. 4A~
DETAILED DESCRIPTIO~
Turning to the drawings, an installation tool 1~ in
- 3 -
-
'
,. , : ' . :
.
rdan~e wi-th the invention is formed by a spli-t-cover housing lOh
containing a -tensioning assemblage 11 and a pivotted cutoff levex 12,
which is visible through a viewing aperture o:E a cutter guard 12g and
mounts a cutter blade 12b.
As illustrated in FIG. 1, the tool 10 can be used to complete
the installa-tion of an item such as a cable tie 20. The strap
portion 21 of the tie 20 is wrapped around articles that are to be
bundled, for example the individual wires W of a cable C. A Eree
end 22 of the tie 20 is inserted through the head 23 of the strap
into the mouth of the tool 10 between gripper constituents llp
and lla of the tensioning assemblage 11.
When force Ft is applied to a trigger 13 of the tool 10, it
is transmitted through levers and linkages (not visihle in EIG. 1~ to
the tensioning assemblage 11, causing the assemblage to be drawn
towards the rear of the gun. This frees a pivotted and spring-loaded
pawl llp which rotates against the portion 22 of the strap and
grips it with respect to a stud lla.
The initial rearward motion of the tensioning assemblage 11
caused by the force F.t tightens the portion 21 o:E the strap around
the wires W of the cable C, with the head 23 o:E the cable tie 20 in
close abutment with the tool 10. Further movement of the tensioning
assemblage 11 increases the tension applied to the gripped portion
22 o~ the tie 20 until a predetermined tension level is reached. At
that point, as explained below, the force -transmitted to the tension-
ing assemblage 11 from the trigger 13 causes a collapse of the inter-
: vening linkage which acts upon the cutoff lever 12 and pivots itupwardly, bringing the blade 12b into sever position with respect to
the gripped end portion 22 of the cable tie 20.
In the typical operation of an installation tooI the sever
action produces a signi~icant shock impact. However, in accordance
with the invention this impact is significantly reduced because of
the particular way in which the cutoff lever 12 is operated, as
explained in conjuction with FIGS. 2A through 2C.
A perspective view showing the relationship between the
tensioning assemblage 11 and the cutoff lever 12 is given in ~IG. 2A.
: ~he tension.ing assemblage 11 is maintained in a normally forward
position in the tool. 1~ by a compression spring llc. The tensioning
assemblage is connected to the trigger 13 through a set ~E actuator
lin~ages including toggle linkages 14 and an internal actuator lever 15.
. .
:
.
~.
'
When the trigger force Ft is applied, it is -transmitted
~hrough a trigger link 13t to the ac-tuator lever 15 which is pivotally
mounted wi-thin the handle 16 oE the tool 10. The upper portion oE
the actuator lever 15 is pivotally connectecl-to -the toggle linkages
14, ~hich are, in turn, pivotally connec-ted -to the bar llb of -the
tensioning assemblage 11. rt~o maintain the toggle linkages 14 in
position to -transmi-t the trigger force Ft, a countervailing force
Fc is applied to -the midpoint 14m of the -toggle through a toggle arm
l~a. *When -the -tensioning Eorce applied Erom -the -trigger 13 exceeds
the countervailing force F , t,he toggle collapses by pivoting with
respect to both the actuator lever 15 and the tensioning bar llb and
engages a cam surface 12c of the cutoff lever 12. Since the operation
of the cutoff lever takes place while the actuator lever is
moving to the rear, there is, in effect~ a cushioned impact of the
collapsed toggle linka~es 14 against the cutoff lever 12. It is
believed that this cushioning limits the shock loading that LS pro-
duced when the strap 22 is severed.
In addition, an ejector'spring 17, in the form of a leaf 17f
with a curvature 17c extending into the mouth oE the tool, is included
~- to reduce any tenden~,y for the severed end of the strap to be
propelled toward the user.
As the tensioning bar llb is drawn towards the rear of the
gun 10, the curved portion 17c of the ejector spring 17 tends to be
flattened against the adjoining housing wall. When the pawl reaches
a cam sur~ace llc (shown in FIGS. 1 and 2A), with the strap 22 under
tension, the cam acts upon the pawl and par-tially releases it. In
addltion, as noted in FIG. 1, the housing lOh has a shield lOs -that
extends at the top of the gun to the vicinity of the ejector spring 17.
Consequently when the strap is under tension, with the pawl llp
30 partially released and the spring 17 partially deflected, and the cutter
blade 12b is operated to sever the strap, the severed portion tends to
be propelled laterally out of the housing, instead of towards the user.
The desired lateral propulsion is promoted by contributions from the
shield lOs, the partial pawl release provided by the cam llc and the
ejector spring 17. This is by contrast with the tools of the prior
art in which the pawl tends to be fully embedded in the leading
portion of the s-trap at the moment of sever and there is no shield lOs,
or ejector spring 17, so tha-t when the strap is severed the accompany-
*The toggle is never completely straight; there is always a slight,,~a~ngular inclination, in the rest position, towards the force Fc.
..~ . 7
- 5 -
. - ., . ~ '
: ' ' '' ' :: . ~.
,,. . . :, '' ' : '
. .
~ tj~
ing release of tension tends -to pivot the severed portion o-f the
s-trap abou-t the pawl and -towards -the user.
A schematic representation oE the tensioning and sever
operation is illustrated in FIGS. 2B and 2C. Ini-tially as shown in
FIG. 2B the individual links oE the toggle assemblage 14 are in
alignment. For simpllcity the ~oggle assemblage 1~ in FIG. 2B is
formed by the first lin]~ 14-1 tha-t is pivotally connected to the
tensioning bar llb and a second link 14 2 that is pivotally connected
to the actuator lever 15. The actuator and sever links 14-1 and 14-2
are in turn pivotally joined. It is a-t -this point of joinder 14m
that the countervailing force F is applied. To keep the counter-
vailing force from driving ~he links 14-1 and 14-2 of the toggle
assemblage out of alignment, the illustrative tensioning bar llb in
FIG. 2B includes an integral stop llt. For the embodiment of FIG.
2A, the upward motion of the linkages is limited by the use of a slot
lls in the draw bar llb as shown in FIG. 4A. The various ways of
applying the countervailing force Fc to the toggle assemblage 14 are
discussed below.
When the tension applied to the strap by the bar llb exceeds
the value of the countervailing force Fc applied at the pivot center
14m of the toggle asse~lage 14, that latter collapses as shown in
FIG. 2C. This collapse brings a bearing surface 14b of the toggle
into engagement with a cam surface 12b at the rear o-f the cutoff
lever 12. Since the toggle assemblage 14 is formed by pivotally
connected me~ers, the force transmitted to the cutoff lever is com-
posed of both horizontal and vertical components, by which a cushioned
impact is applied to the cutoff lever 12, instead of a direct impact,
so that impac-t shock loading is avoided.
In addition, as is evident from FIG. 2B, the use of the
trigger 13 in con~unction with the actuator lever 15 provides a
mechanical advantage so that the amount of operator force applied to
the toggle is considerably less than that needed with conventional
installation tools. The use of the actuator lever 15 also permi-ts
the desired tensioning force to be applied over a relatively small
arc of operation of the trigger 13.
The countervailing force ~c that is applied to the toggle
1~ may be realiYed in a wide variety of ways. As shown in FIG. 2A
the force Fc is applied at the end of the toggle arm l~a. This
-- :
- : .
,
- ' ~. '
upward component of countervail:ing thrust may be achieved by the
use of a spring (not shown) which is hooked to the end of the lin]cage
14a. However, such a spring tends to be mechanically unrel:iable and
in accordance with the invention -the desired countervailing force
Fc can be realized using a compression spring cage 30 of the kind
shown in FIGS. 3~ and 3B. As indica-ted in FIG. 3A the end of the
toggle linkage 14a is connected by a pivot pin 31p to an upper part
31 of the cage 30, which is slideably movable with respect to a
lower part 32. Since the upper part 31 oE the cage 30 applies the
desired countervailing force Fc to the toggle arm 14a and is
therefore relatively immovable, since the arm initially cannot push
the toggle links 14 beyond their co-linear position.
As noted in conjunction with FIG. 2B the upward movement
of the toggle linkage 14 is controlled by a stop member llt which is
an integral part of the tensioning bar llb. To adjust the tension
applied through the toggle arm 14a an adjusting member 32a is
threaded into the bottom portion 32 of the case 30 as shown in
FIG. 3B by rotation of a tension control knob 33. This moves the
lower portion 32 of the case 30 of FIG. 3A upwardly with respect to
the upper portion 31 and carries with it the indicator 32r that moves
within a slot 31s of the upper portion 31 and simultaneously causes
compression of the tension control spring 3~s. rrhis arrangement
achieves precise control`over tension and a high degree oE mechanical
stability.
A partial sectional view of the entire installation tool
of FIG. 1 is shown in FIGS. 4A throu~h 4C to indicate the
relative positioning of the internal constituents of the tool, as
well as the interrelations among those constituents.
Thus in the tool 10 as shown in FIGS. 4A and 4B the toggle
assemblage 14 is ~ormed by four linkages (FIG. 4C) 14-1 through 14-4.
The link 14-1 is sea-ted on a hub llh of the tensioning bar llb. The
link 14-1 is in turn pivotally connected to the arm 14a that extends
to the compression ~age 30. The arm 14a is connected to the lever
15 by a link 14-2, as well as by a further link 14-3. There is also
pivotal connection between the hub llh of the tensioning bar llb and
the arm l~a by a li~k 14-4. It is the latter link that limits the
upward movement of -the toggle assemblage due to the application of
the compression force Fc through the arm 14a. This is because, as
- 7 -
~ "
~ . '; . ''. . ' . . .
.
- . . . .
' ' '' ' ''..... " ~':
seen in FIG. 4A, the Eour-th linkage 14-4 (FIG. 4C) rides in a slot lls
(FIG. 4A) of the tensioning bar llb. Initially with the full compres-
sion force Fc applied to the arm 14a -the individual links oE -the
toggle assemblage are in alignment and the link 14-4 is seated in the
upper part of the recess lls. When the tension applie~ to the strap
exceeds the countervailing force F -the toggle assemblage collapses
as described previously and the link 14-4 moves out of the slot lls
to contact the cam surface 12c and operate the sever lever 12.
Also indicated in E`IGS. 4A and 4B iS the placement of the
cam llc that provides partial release of -the pawl llp before sever.
Details of the compression cage 30 are illustra-ted in
FIGS. 4A and 4C.
While various aspects of the invention have been set forth
by the drawings and the specification, it is to be understood that
the foregoing detailed description is Eor illustLation on:Ly and -that
various changes in parts, as well as -the substitution of equivalent
constituents for those shown and described, may be made wlthout
departing from the spirit and scope of the inven-tion as set forth in
the appended claims.
~ O _ _
: .
. ..
.~,
- 8 -
,
:: -
