U.S. patent number RE30,996 [Application Number 06/100,119] was granted by the patent office on 1982-07-20 for strap tension sensing and cut off mechanism.
This patent grant is currently assigned to Thomas & Betts Corporation. Invention is credited to Charles Dolgos, Walter Pobuta.
United States Patent |
RE30,996 |
Pobuta , et al. |
July 20, 1982 |
Strap tension sensing and cut off mechanism
Abstract
A tension sensing and cut off control mechanism which operates
independently of the mechanism for drawing tight a closed loop
bundling strap placed about objects to be bundled. Within a
stationary block, affixed to one end of a tool housing, is placed a
movable block held stationary by a displaceable pin. Adjustable
loading means engage said pin to control its movement based on the
tension to be applied to the strap. Below the established load a
separate pawl mechanism draws the strap up about the bundle. When
the load on the pin is exceeded, the movable block is moved by the
strap head causing a blade means to sever the strap adjacent the
head and all parts return to their original positions.
Inventors: |
Pobuta; Walter (Elizabeth,
NJ), Dolgos; Charles (Linden, NJ) |
Assignee: |
Thomas & Betts Corporation
(Raritan, NJ)
|
Family
ID: |
26796823 |
Appl.
No.: |
06/100,119 |
Filed: |
December 4, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
776489 |
Mar 10, 1977 |
04064918 |
Dec 27, 1977 |
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Current U.S.
Class: |
140/123.6 |
Current CPC
Class: |
B65B
13/027 (20130101) |
Current International
Class: |
B65B
13/02 (20060101); B65B 13/00 (20060101); B21F
009/02 () |
Field of
Search: |
;100/29
;140/93A,93.2,123.5,123.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Combs; Ervin M.
Attorney, Agent or Firm: Rodrick; Robert M. Woldman;
Jesse
Claims
We claim:
1. A strap tension sensing and cut off mechanism comprising:
stationary block means having a first end and a second end and an
intermediate wall intermediate said first and second ends; movable
block means having a first end and a second end, said movable block
means first end adjacent said stationary block means first end and
said movable block means second end adjacent said intermediate
wall; means for applying a force to said first end of said movable
block means; pin means having a first position in engagement with
said movable block means to prevent the movement of said movable
block means in response to the force applied thereto and a second
position out of engagement with said movable block means to permit
movement of said movable block means in response to the force
applied thereto; and selectively presettable means coupled to said
stationary block means for applying a selected restraining force to
said pin means to position said pin means in said first position;
said pin means moved from said first to said second position when
the force applied to said first end of said movable block means
exceeds the selected restraining force upon said pin means.
2. A strap tension sensing and cut off mechanism as defined in
claim 1 wherein said stationary block means further comprises an
end wall adjacent said second end and said mechanism further
comprises spring means coupled between said end wall and said
second end of said movable block means to establish an initial
position of said movable block means with respect to said
stationary block means.
3. A strap tension sensing and cut off mechanism as defined in
claim 1 wherein said selectively presettable means comprises a
spring member to bias said pin means to said first position.
4. A strap tension sensing and cut off mechanism as defined in
claim 1 wherein said selectively presettable means comprises a beam
member to bias said pin means to said first position.
5. A strap tension sensing and cut off mechanism as defined in
claim 1, wherein said selectively presettable means comprises an
adjustable cam surface and a beam member having a first end and a
second end; said beam member first end coupled to said stationary
block means; said beam member second end engaging said cam surface
and said beam member being engaged by said pin means intermediate
said first and second ends of said beam member.
6. A strap tension sensing and cut off mechanism as defined in
claim 5, wherein said selectively presettable means further
comprises a notched wheel having segments corresponding to portions
of said cam surface and a detent for engaging the notches of said
notched wheel and retaining a selected cam surface portion adjacent
said beam member second end.
7. A strap tension sensing and cut off mechanism as defined in
claim 1, further comprising crank means pivotably coupled to said
movable block means, said crank means having a first leg and a
second leg, said second leg engageable with said intermediate wall
of said stationary block member to pivot said crank.
8. A strap tension sensing and cut off mechanism as defined in
claim 7, further comprising a severing blade coupled to said
movable block means and engaged by said crank means first leg to
sever said means for applying a force to said first end of said
movable block means.
9. In a strap tightening and cut off tool of the type having a
housing, a fixed grip coupled to said housing, a movable trigger
coupled to said housing for relative movement with respect to said
fixed grip; a pull bar having a pawl at one end to grip a strap
inserted in said tool, said pull bar coupled at its second end to
said movable trigger, said movable trigger causing said strap to be
further drawn into said tool as said movable trigger is moved
towards said fixed grip and permitting said pawl to nonengagingly
move with respect to said strap as said movable trigger moves away
from said fixed grip; a strap tension and cut off mechanism
comprising: movable block means having a first position relative to
said housing and a second position relative to said housing, said
second position being closer to said housing than said first
position; said movable block means engaged by the head of a strap
and having a force exerted thereon by said strap head as said strap
is drawn into said tool, said force tending to move said movable
block means from said first position to said second position; blade
means for severing the strap adjacent the head thereof; control
means selectively presettable to any one of a plurality of
positions for applying a selected restraining force to said movable
block means to prevent said movable block means from moving from
said first position to said second position; and movable link means
coupled to said movable block means and moved in response to the
movement of said movable block means from said first position to
said second position, said movable link means also coupled to said
blade means to operate said blade means to sever the strap when the
force applied to said movable block means by the head of the strap
is greater than the restraining force applied to said movable block
means by said control means permitting said movable block means to
move towards said second position thereby causing said movable link
to move said blade means and sever the strap.
10. A strap tension and cut off mechanism as defined in claim 9
further comprising resilient means coupled to said movable block
means for moving said movable block means to its first position
after the strap is severed.
11. A strap tension and cut off mechanism as defined in claim 9
further comprising compression means coupled to said movable block
means for moving said movable block means to its first position
after the strap is severed.
12. A strap tension and cut off mechanism as defined in claim 9,
further comprising spring means coupled to said blade means for
returning said blade means to an initial position upon severance of
the strap.
13. A strap tension and cut off mechanism as defined in claim 9,
further comprising compression means coupled to said movable block
means for moving said movable block means to its first position;
and spring means coupled to said blade means for returning said
blade means to an initial position; said compression means and said
spring means both operating upon the severance of the strap.
14. A strap tension and cut off mechanism as defined in claim 9,
further comprising a stationary block partially surrounding said
movable block means; said stationary block having a first wall; and
compression means coupled to said movable block means and said
first wall of said stationary block to move said movable block
means to its first position after the strap is severed.
15. A strap tension and cut off mechanism as defined in claim 9,
further comprising a stationary block partially surrounding said
movable block means; said stationary block having a first wall and
a second wall; compression means coupled to said movable block
means and said first wall of said stationary block to move said
movable block means to its first position after the strap is
severed; and a crank pivotally coupled to said movable block means,
said crank having a first leg coupled to said blade means and a
second leg to contact said second wall of said stationary block;
whereby when said second leg of said crank contacts said second
wall, said crank pivots to cause said crank first leg to move said
blade means into severing engagement with a strap being drawn into
said tool.
16. A strap tension and cut off mechanism as defined in claim 9,
further comprising a nose member coupled to said movable block
means; said nose member having a first surface positioned adjacent
the path of movement of said blade means; and a slot in said nose
member to align a strap placed in said tool with said blade means
to facilitate severance of the strap.
17. A strap tension and cut off mechanism and defined in claim 9,
wherein said control means comprises a pin engageable with said
movable block means and means to control the movement of said
pin.
18. A strap tension and cut off mechanism as defined in claim 9,
wherein said control means comprises a pin engageable with said
movable block means to control movement of said movable block
means; cam means selectively positionable; and lever means engaging
said cam means and said pin to determine the amount of force the
head of the strap must exert upon said movable block means to cause
severance of the strap.
19. A strap tension and cut off mechanism as defined in claim 9,
wherein said control means comprises a pin engageable with said
movable block means to control movement of said movable block
means; a rotatable disk having a periphery slotted at predetermined
positions and having a cam formed on one of the planar faces of
said disk; detent means engageable with said slots to permit said
disk to be locked at predetermined positions, positioning said cam
accordingly; and lever means engaging said cam and said pin to
determine the amount of force the head of the strap must exert upon
said movable block means to cause severance of the strap.
20. A strap tension and cut off mechanism as defined in claim 9,
wherein said control means comprises a pin having a tapered end
engageable with a complementarily tapered portion of said movable
block means to control movement of said movable block means; a
rotatable disk having a periphery slotted at predetermined
positions and having a cam formed on one of the planar faces of
said disk; detent means engageable with said slots to permit said
disk to be locked at predetermined positions, positioning said cam
accordingly; indicia on the second planar face of said disk to
identify the position of said cam; and lever means engaging said
cam and said pin to determine the amount of force the head of the
strap must exert upon said movable block means to cause severance
of the strap.
21. A strap tightening and cut off tool for tightening a strap
about a plurality of objects to be bundled and severing the excess
tail portion comprising: a housing having a first end and a second
end; a pull bar having a first end and a second end, said pull bar
coupled to said housing and movable with respect thereto; drive
means coupled to said pull bar second end for moving said pull bar
with respect to said housing; pawl means capable of gripping a
strap when moved in a direction towards said housing second end and
nonengagingly moving over a strap when moved in a direction towards
said housing first end; said pawl means coupled to said pull bar
first end; stationary block means coupled to said housing first
end; movable block means within said stationary block means, said
movable block means being engaged by the head of a strap to be
tightened, the head of the strap applying a force to said movable
block means tending to move same towards said housing second end;
blade means coupled to said movable block means; control means
selectively presettable to any one of a plurality of positions for
applying a restraining force to said movable block means to prevent
the movement of said movable block means in response to the force
applied by the head of the strap; and movable link means coupled to
said movable block means and moved in response to the movement of
said movable block means, said movable link means also coupled to
said blade means to operate said blade means to sever the strap
when the force applied to said movable block means by the head of
the strap is greater than the restraining force applied to said
movable block means and said movable block means is moved.
22. A strap tightening and cut off tool as defined in claim 21,
wherein said control means comprises a presettable cam and a lever
coupled to said cam and said stationary block means to prevent
movement of said movable block means until the force applied by the
head of the strap upon said movable block means exceeds the
restraining force placed upon said movable block means. .Iadd. 23.
Strap tightening and cut off apparatus for tightening a strap about
a plurality of objects to be bundled and severing the excess tail
portion of the strap, said apparatus comprising: a housing defining
an inlet for receiving such strap tail portion; strap pulling means
supported in said housing interiorly of said inlet for grippingly
engaging said strap tail portion and drawing said strap through
said inlet; tension sensing means supported in said housing for
contiguous engagement with said strap at a location between said
inlet and the location of engagement of said strap pulling means
and said strap; and cutting means in said housing for cutting said
strap upon sensing of predetermined strap tension by said tension
sensing means. .Iaddend..Iadd. 24. The apparatus claimed in claim
23, wherein said tension sensing means comprises a sensor element
adjacent said inlet engaging said strap contiguously, said housing
supporting said sensor element for movement in the direction of
such drawing of said strap therein. .Iaddend..Iadd. 25. The
apparatus claimed in claim 24, wherein said tension sensing means
includes bias means for biasing said sensor element in a direction
opposite such drawing direction. .Iaddend..Iadd. 26. The apparatus
claimed in claim 25, wherein said tension sensing means includes
releasable detent means for preventing movement of said sensor
element in said drawing direction on strap tension less than said
predetermined strap tension. .Iaddend..Iadd. 27. The apparatus
claimed in claim 26, further including means responsive to movement
of said sensor element to operate said cutting means.
.Iaddend..Iadd. 28. The apparatus claimed in claim 23, further
comprising a fixed grip coupled to said housing, a movable trigger
coupled to said housing for relative movement with respect to said
fixed grip; a pull bar in said strap pulling means having a pawl at
one end to grip a strap inserted in said inlet, said pull bar
coupled at its second end to said movable trigger, said movable
trigger causing said strap to be further drawn into said tool as
said movable trigger is moved towards said fixed grip and
permitting said pawl to nonengagingly move with respect to said
strap as said movable trigger moves away from said fixed grip.
.Iaddend..Iadd. 29. The apparatus claimed in claim 23, wherein said
housing has a first end and a second end; said strap pulling means
includes a pull bar having a first end and a second end, said pull
bar coupled to said housing and movable with respect thereto, drive
means coupled to said pull bar second end for moving said pull bar
with respect to said housing and pawl means capable of gripping a
strap when moved in a direction towards said housing second end and
nonengagingly moving over a strap when moved in a direction towards
said housing first end, said pawl means coupled to said pull bar
first end; said tension sensing means includes a stationary block
coupled to said housing first end; a movable block within said
stationary block, said movable block being engaged by a strap to be
tightened; and said cutting means includes blade means coupled to
said movable block for severing the strap upon movement of said
movable block. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to the field of bundling discrete objects
into bundles. For example, forming a bundle of discrete drill rods,
welding rods, etc. and more particularly to the bundling of a
plurality of wires into a harness for simpler movement and
attachment than would be possible with the wires handled alone.
2. Description of the Prior Art
In prior art tools of the type shown in U.S. Pat. No. 3,344,815
issued Oct. 3, 1967 for a "Strap Tightening and Cutting Tool" to G.
R. Lawson et al and assigned to the assignee of the instant
invention, the mechanism for sensing the strap tension and for
initiating cut off are remote from the tool nose piece where the
strap enters the tool and adjacent which the cut off blade travels.
Accordingly, each tool must be separately designed and the optimum
conditions for each mechanism compromised in the final tool. The
handle 25 pivots about pivot 26 as the step 24 is drawn into the
tool by the pawl engagement with the strap 24. Once the preset
tension in spring 18 is exceeded the handle 25 pivot shifts from 26
to the pivot 31 and the rocker arm 15 is lifted by plate 21 causing
cut off adjacent nosing 40. The various assemblies are placed at
convenient locations not necessarily the best locations.
SUMMARY OF THE INVENTION
The present invention overcomes the difficulties noted above with
respect to prior art devices by providing a mechanism for the
sensing of strap tension and for severing the excess tail end
portion beyond the strap head. Such mechanism is separate and apart
from the housing, grips, triggers and pull bars, etc. which make up
the remainder of the tool. The remainder of the tool can be
mechanical as in a hand tool or may include pneumatic or hydraulic
mechanisms as in bench tools.
The mechanism for setting the strap tension and for severing the
excess tail end portion does not come into play until the strap
about the bundle is drawn tightly enough such that the tension in
the strap approaches the desired tension level set into the
mechanism. In operation, the operator places the strap about the
articles to be bundled and draws the strap up, tightening the strap
loop about the bundle. The free tail end portion is then inserted
into the tool through a slot in the nose piece, through the
mechanism into the pawl mechanism. The operation of the trigger
causes the pawl mechanism to draw the loop tighter. One or more
trigger strokes may be used depending upon how tightly the operator
draws the strap up manually. On release strokes of the trigger, the
pawl mechanism travels non-engagingly over the strap to its initial
position without affecting the strap. Once the strap tension
approaches the tension setting of the mechanism, the mechanism is
actuated to sever the free tail end portion of the strap beyond the
strap head.
The mechanism for the sensing of the strap tension and for severing
the excess tail end portion of the strap comprises a rigid,
stationary block partially enclosing a movable block and having
spring means to establish the initial position of said movable
block with respect to said stationary block. The movable block
carries a crank on a pivot pin and a severing blade on a further
pivot pin. One arm of the crank engages the severing blade for
operating the blade from its initial position out of contact with
the strap to its strap severing position. The second arm of the
crank is arranged to contact a shoulder of the stationary block.
The movable block is contacted by the head of the stray without
effect as long as the tension in the strap is less than a preset
value, being prevented from moving with respect to the stationary
block by a pin. The pin is free to move if the force which the
movable block exerts on one end of the pin equals the force applied
to the second end of the pin.
The force presetting mechanism comprises a segmented disk having
slots extending inwardly from the outer periphery. Into these slots
a detent is placed to hold the disk at any preset segment. On one
surface of the disk is placed a cam surface varying in a linear
fashion from the disk height to some greater height. A beam
anchored at one end to the stationary block has its other end
positioned on the cam. As a result of the position of the cam the
beam places different forces upon the pin which rests on the beam
at some point intermediate the beam ends. When the force on the top
end of the pin exceeds the force on the lower end of the pin, the
pin is displaced and the movable block is permitted to move in the
stationary block, bringing the second arm into contact with the
shoulder of the stationary block causing the crank to rotate about
its pivot pin and move the severing blade into and through the
strap. The severance of the strap removes the tension from the
strap tail end portion and the movable block is free to return to
its initial position under the influence of the spring means. It is
an object of this invention to provide an improved tool.
It is an object of this invention to provide an improved tool for
tightening a strap about objects to be bundled and severing the
excess tail end portion.
It is another object of this invention to provide a mechanism for
sensing the tension in a strap.
It is another object of this invention to provide a mechanism for
sensing the tension in a strap and severing the excess strap
portion.
It is another object of this invention to provide a presetable
mechanism for sensing the tension in a strap.
It is still another object of this invention to provide a
presetable mechanism for sensing the tension in a strap and
severing the excess strap portion.
It is still another object of this invention to provide a mechanism
for sensing the tension in a strap apart from the mechanism for
drawing a strap tightly about a bundle.
It is yet another object of this invention to provide a mechanism
for sensing the tension in a strap and severing the excess strap
portion.
It is still another object of this invention to provide a
presettable mechanism for sensing the tension in a strap and
severing the excess strap portion apart from the mechanism for
drawing a strap tightly about a bundle.
Other objects and features of the invention will be pointed out in
the following descriptions and claims and illustrated in the
accompanying drawings, which disclose, by way of example, the
principles of the invention, and the best modes which have been
contemplated for carrying them out.
BRIEF DESCRIPTION OF THE DRAWING
In the drawings in which similar elements are given similar
reference characters.
FIG. 1 is a side elevational view of a hand tool including a strap
tension sensing and cut off mechanism constructed in accordance
with the concepts of the invention.
FIG. 2 is a top plan view of the tool of FIG. 1.
FIG. 3 is a side elevational view of the tool of FIG. 2 taken along
the lines 3--3.
FIG. 4 is a side elevational view of the pull bar and pawl assembly
of the tool of FIG. 1.
FIG. 5 is an enlarged side elevational view of the pawl assembly of
the tool of FIG. 1.
FIG. 6 is a front elevational view of the pawl assembly of FIG.
5.
FIG. 7 is a top plan view of the pull bar of FIG. 4 with the pawl
assembly omitted.
FIG. 8 is a side elevational view, partially cut away and partially
in section of the shroud of the tool of FIG. 1.
FIG. 9 is a front elevational view of the shroud of FIG. 8.
FIG. 10 is a bottom plan view of the shroud of FIG. 8.
FIG. 11 is a fragmentary bottom plan view, partially in section, of
the tension selection dial and the stationary block of the tool of
FIG. 1.
FIG. 12 is a side elevational view of the tension selection dial of
FIG. 11.
FIG. 13 is a side elevational view of the stationary block of the
tool of FIG. 1.
FIG. 14 is a side elevational view, partially cut away and
partially in section, of a strap tension sensing and cut off
mechanism assembly constructed in accordance with the concepts of
the invention.
FIG. 15 is a front elevational view of the movable block of the
assembly of FIG. 14.
FIG. 16 is a side elevational view of the movable block of FIG.
15.
FIG. 17 is a fragmentary, sectional view of the engagement between
the stationary block and the tool housing.
FIG. 18 is a front elevational view of the nose piece of the tool
of FIG. 1.
FIG. 19 is a side elevational view of the crank of FIG. 14.
FIG. 20 is a front elevational view of the severing blade of the
tool of FIG. 1.
FIG. 21 is a side elevational view of the severing blade of FIG.
20.
FIG. 22 is a fragmentary, partially sectional view of the severing
blade assembly.
FIG. 23 is a front elevational view, partially in section, of the
assembly of FIG. 14.
FIG. 24 is a side elevational view, partly cut away and partially
in section, of a further tool employing the strap tension sensing
and cut off mechanism.
FIG. 25 is a fragmentary side elevational view of the tool of FIG.
1 in its initial condition with the free tail end portion of a
looped strap introduced into the tool.
FIG. 26 shows the positions of the parts of FIG. 25 in an advanced
position.
FIG. 27 shows the positions of the parts of FIG. 25 just prior to
strap cut off.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIGS. 1 to 7, a tool 30 having a strap tension
sensing and cut off mechanism 100 is shown. Tool 30 has a generally
pistol configuration with a housing 32 ending in a fixed grip 34.
The grip 34 may have a recessed area 36 and openings 38, 40 to make
the overall tool 30 light in weight and well balanced. (See FIG.
1.) A movable trigger 42 is pivotally mounted to housing 32 (See
FIG. 3) by pivot pin 44. The movable trigger 42 is coupled by pin
46 to a pull bar 48. The pull bar 48 has a slot 50 to accept pin 46
and a slot 52 to accept pivot pin 44. (See FIG. 4.) The slots 50,
52 permit the free movement of the pull bar 48 without regard for
the position of the movable trigger 42.
Pull bar 48 has at its extreme left end 54 (see FIG. 4) a pawl
assembly 56 mounted upon a tab 58 extending perpendicularly to the
plane of the pull bar 48. Pin 60 pivotally connects pawl 62 to the
tab 58 (see FIG. 5). Pawl 62 has a nose portion 64 and teeth 66. A
torsion spring 68 has one arm 70 which engages pawl 62 and a second
arm 72 which grips a marginal edge of the tab 58 to bias the teeth
66 of pawl 62 into contact with portion 53 of the pull bar 48. As
will be evident below, when the pawl assembly 56 is in the position
shown in FIG. 1, the nose portion 64 of pawl 62 will be in contact
with a shoulder to cause the pawl 62 to rotate in the direction of
the arrow 74 as it appears in FIG. 5. This pawl 62 rotation creates
a space between the upper surface of portion 53 of pull bar 48 and
the teeth 66 sufficient to permit the unimpeded entrance of a strap
end portion. As movable trigger 42 is moved towards fixed grip 34,
pin 46 is slot 50 likewise causes the rightward movement of pull
bar 48 with pawl assembly 56. The termination of contact between
nose portion 64 with the contact shoulder permits the pawl 62 to
rotate in a direction opposite to the arrow 74 in FIG. 5 to bring
teeth 66 in contact with the strap body holding it securely between
the pawl 62 and portion 53 of pull bar 48. Any further movement of
trigger 42 will pull a strap more tightly about articles to be
bundled, as will be described below.
A tab 76 is affixed to the underside of pull bar portion 53 which
engages a compression spring 78 in recess 80. One end of spring 78
engages tab 76 while the other end engages shoulder 82 of recess
80. Thus the pull bar 48 and pawl assembly 56 are always urged
towards the initial position shown in FIG. 1. An aperture 84 (see
FIG. 3) can receive the end of a wire (not shown) for cutting. This
is accomplished by the sharpened V-notch blade 86 at the rightmost
end of pull bar 48. The material of the housing 32 provides the
supporting anvil for the cutting by blade 86.
In the description of the tool 30, a fully mechanical, hand tool is
described. It is not necessary to power the pawl assembly 56 by
hand power, instead a pneumatic or hydraulic cylinder can be used.
In FIG. 24 there is shown a housing 88 containing a pneumatic
cylinder. A grip 90 has a fitting 92 thereon for coupling to a
source of pneumatic fluid. A pull bar 48 having a pawl assembly 56
thereon operates as described above with respect to pull bar 48.
FIG. 24 also shows the opening of pawl assembly 56 to receive a
strap. Nose portion 64 of pawl 62 is in contact with shoulder 96
which deflects pawl 62 in the direction of arrow 74 of FIG. 5. The
nose portion 64 is urged against the shoulder 96 by a reset
compression spring such as 78 in FIG. 3.
A further structure, the strap tension sensing and cut off
mechanism 100, is also found adjacent the end 54 of the pull bar
48, however, mechanism 100 is coupled to housing 32 and does not
move as a unit either with respect to pull bar 48 or housing 32.
The mechanism 100 is not responsive directly to the tool 30 but
only to a by-product of its operation. As will be described below
in greater detail, a desired tension level is set into mechanism
100 and the tail end portion of a strap to be tightened to a preset
tension is passed through the mechanism 100 into the pawl assembly
56. The head of a strap contacts the face of the mechanism 100 but
does not move it until the tension in the strap reaches that preset
at which time a movable block overcomes the detent mechanism and
engages a lever to operate the severing blade to cut off the excess
tail end portion.
Turning now to FIGS. 8 to 23, the details and operation of the
strap tension sensing and cut off mechanism 100 is set out. A
stationary block 102 (see FIG. 13) has a long tab 104 containing
mounting aperture 106 and a further aperture 108 whose function
will be described below. A short tab 110 extends above tab 104. The
stationary block 102 is connected to a portion of the tool 30
housing 32 by means of a fastener 112 extending through an aperture
in housing 32 into the aperture 106 (See FIG. 17). The tab 110
rests atop a flange 33 of housing 32 to give greater stability to
the mechanism 100. A cavity 114 (See FIG. 13) faces away from
housing 32 and contains recesses 116 and 118 to each receive a rest
spring as will be described below. An extension 120 has an undercut
portion 122. Placed inside of the cavity 114 is a movable block 124
shown best in FIGS. 15 and 16. Movable block 124 has a slot 126 in
a front face thereof to receive a nose piece as will be described
below. Recesses 128,130 are placed in a rear face of movable block
124 to receive the second ends of rest springs 132,134 (See FIG.
14) which extend between the movable block 124 and the stationary
block 102. Spring 132 is received in recess 116 of stationary block
102 and recess 128 of movable block 124. Spring 134 is received in
recess 118 of stationary block 102 and recess 130 of movable block
124. The springs 132,134 establish the initial position of movable
block 124 with respect to stationary block 102.
A slot 136 in movable block 124 permits a strap to freely pass
through block 124. A pivot pin 138 for the crank lever extends from
the side of block 124 (See FIG. 15). An aperture 140 to receive one
end of a torsion spring and an aperture 142 to receive a pivot pin
for the serving blade are contained in the front face of movable
block 124. Movable block 124 has a recess 143 having a front wall
145, a rear wall 147 and a perpendicular wall 149. The lower edge
of front wall 145 is chamfered as at 144 which will engage a
similarly tapered portion of a pin to be described below.
A nose piece 146 (see FIG. 18) has a leg 148 (See FIG. 14) for
insertion in the slot 126 in the movable block 124 which together
with pin 150 which passes through slot 152 anchors nose piece 146
to movable block 124 and sets its position therewith (See FIG. 22).
Slot 155 permits passage of the strap through nose piece 146. The
nose piece 146 provides a broad area which is placed in contact
with a strap head and permits the response of the mechanism 100 to
cause cut off of the excess strap portion. To prevent the movement
of movable block 124, under the influence of a strap head as it is
being pulled up or tightened, a pin 154 is employed (see FIG. 14).
Pin 154 has a tapered end portion 156 which is complementary to the
chamfered edge 144 of movable block 124. As will be described, when
chamfered edge 144 places sufficient force on pin 154, pin 154 will
be displaced downwardly in the direction of arrow 158 in FIG. 14
permitting movable block 124 to move towards the stationary block
rear wall 159. The lower edge of pin 154 is rounded as at 160. The
rounded edge 160 of pin 154 is made to bear against a beam 162 one
end of which is supported in undercut 122 of stationary block 102
and the other edge upon a cam surface to be described. As will be
evident below, the beam end on the cam surface will load the beam
and thereby apply a force to the pin 154 resisting its movement in
the direction of arrow 158. The resistance of pin 154 to movement
will continue until the force transmitted by chamfered edge 144 of
the movable block 124 to pin 154 exceeds the loading of the beam
162 at which time the pin 154 will be displaced.
The mechanism for presetting the strap tension at which cut off
will take place is described with reference to FIGS. 11, 12 and 14.
A wheel 163 (see FIG. 11) has a plurality of slots 164 extending
inwardly from the outer peripheral edge. Affixed to one planar
surface 166 is a cam surface 168 (see FIG. 12) extending from the
level of planar surface 166 to a maximum height 169. Beam 162 is
anchored at one end in undercut 122 (see FIG. 13) and at its
opposite end on the cam surface 168. As the beam 162 end is placed
on a higher point of the cam surface 168, the beam 162 builds up a
resisting force partially countering the downward force exerted by
pin 154 upon beam 162 and thus requiring a greater force to
displace pin 154 in the direction of arrow 158. The position of the
cam surface 168 is identified by the indicia 170 on the opposite
planar face of wheel 163 from that containing cam surface 168. The
indicia is visible through a window in the shroud, to be described
below. To hold the wheel 163 in its desired position a detent 172
is provided. Detent 172 has a finger 174 which can enter the slots
164 and prevent accidental movement of wheel 163. Wheel 163 is
mounted upon pin 176 extending into aperture 108 of tab 104 of the
stationary block 102.
Once the resistance force on pin 154 is overcome, the movable block
124 is now able to move within cavity 114 towards rear wall 159 of
stationary block 102. A crank 178, shown in FIG. 19, has a first
leg 180 to engage the severing blade and a second leg 182. The
crank 178 is free to rotate about pivot pin 138 of the movable
block 124. As the movable block 124 moves towards rear wall 159 of
stationary block 102, the arm 182 of crank 178 contacts shoulder
184 of stationary block 102 and causes the crank 178 to rotate
clockwise about the pivot pin 138 raising the first leg 180 of
crank 178. Severing blade 186 (see FIGS. 20 and 21) has a sharp
knife edge 188 and is pivotally mounted to the movable block 124 by
the pin 150. Below the knife edge 188 is a slotted area with a
shoulder 190, a slot 192 and a tab 194. As first leg 180 of crank
178 is raised it contacts shoulder 190 of blade 186 causing the
blade to rotate counterclockwise about pin 150 cutting a strap
passed above knife edge 188. The blade 186 is restored to its
initial position, after crank 178 is reset by the torsion spring
198. One end of torsion spring 198 is positioned in aperture 140 of
the movable block 124 and the other end rests upon tab 194, as is
best seen in FIG. 22.
A shroud 200 is shown in FIGS. 8, 9, 10 and 14. Shroud 200 retains
the various portions of mechanism 100 in place and provides for
easy access thereto by the strap. The shroud 200 is formed of a
single piece of metal having a bottom portion 202 having a window
204 and an aperture 206. The indicia 170 upon wheel 163 are visible
through window 204, one at a time so that the operator knows the
tension setting of the tool 30. Fastener 112 (see FIG. 17) passes
through aperture 206 to hold the shroud 200 to housing 32. Side 208
has a slot 210 therein with the marginal edges 212, 214 contoured
to provide a simple lead-in to slot 210 (see FIG. 9). Bent down tab
218 from top portion 216 and bent up tab 220 from bottom portion
202 sets the limit for the movement of movable block 124 away from
rear wall 159 of stationary block 102, as is evident from FIG.
14.
Turning now to FIGS. 25, 26 and 27 the operation of the tool 30 of
FIG. 1 is summarized. A strap 216 having a head end portion 218, a
tail end portion 220 and a strap body portion 222 therebetween is
looped about a plurality of discrete articles 224 to be formed into
a bundle. The loop is formed by threading tail end portion 220 of
the strap 216 through an aperture in head end portion 218. Also
located in the head end portion 218 is a one way locking device
(not shown) which will permit the strap 216 to be drawn up on the
articles 224 but prevent the loop from being opened by a force
applied to the strap 216. The tail end portion 220 is pulled up to
a hand tight condition and then inserted through slot 210, slot 155
of nose piece 146, slot 136 of movable block 124, slot 161 of
stationary block 102 to the space between the portion 53 of the
pull bar 48 and the toothed portion 66 of pawl 62. The pawl 62 is
being held away from the portion 53 of pull bar 48 by the contact
of nose portion 64 of pawl 62 with shoulder 96 of stationary block
102. It is assumed that the wheel 163 has been set to the desired
tension level.
Forces are now applied to movable trigger 42 to move it towards
fixed grip 34. This causes pull bar 48 to move to the right as
shown in FIG. 26. The termination of contact between nose portion
64 of pawl 62 and shoulder 96 of stationary block 102 permits the
pawl 62 to rotate clockwise under the influence of torsion spring
68 and grip the strap 216 and pull the loop tighter about the
articles 224. One or more strokes of movable trigger 42 may be
required to pull up strap 216 to the desired tension. The release
of the movable trigger 42 and its movement away from fixed grip 34
causes the pawl 62 to pass over the strap 216 in a non-engaging
manner. The parts of tool 30 are maintained in the positions shown
in FIG. 26 until the desired strap tension is sensed. At this time,
as is shown in FIG. 27, the pin 154 is pushed out of its at rest
position and the movable block 124 is permitted to move towards
stationary block 102. The force for moving the movable block 124 is
provided by the pull bar 48 and is applied by head portion 218 of
strap 216 engaging the nose piece 146. Once movable block 124 is
moved towards stationary block 102 the second leg 182 of crank 178
engages shoulder 184 to cause the crank 178 to move the blade 186
to the severing position. Once cut off has been completed the
absence of force upon nose piece 146 permits the springs 132,134 to
return movable block 124 to its initial position.
While there have been shown and described and pointed out the
fundamental novel features of the invention as applied to the
preferred embodiments, it will be understood that various omissions
and substitutions and changes of the form and details of the device
illustrated and in their operation may be made by those skilled in
the art, without departing from the spirit of the invention.
* * * * *