Note: Descriptions are shown in the official language in which they were submitted.
:~26~3~3~
This application is a divisional of Canadian application
No. 409,360 filed August 13, 1982.
The invention relates -to -the harnessiny of the items and
more particularly to the realization of efficient, low-cost, high
strength harnessing devices which are easy to use.
Harnessing devices are widely used for the bundling of
objects. Such devices are typically formed wi-th a serrated strap
that is fitted to an apertured head containing an internal pawl or
locking tang that engages the serrations of the strap. Other
harnessing devices are in the form of an apertured strap fitted to
a buckle-like head with a tongue -that enters the apertures of the
strap.
Harnessing devices with serrated straps have the
disadvantage of being only as secure as their pawls. Where the
items that are harnessed are heavy or are subjected to rough
handling, the items can become accidentally released, for example,
by pawl failure. Attempts have been made to strengthen serrated
strap devices, without achieving the desired end result of
providing enhanced security against accidental release of
harnessed items. Similar objections apply to harnessing devices
with buckle-like heads. In these devices, a tongue which enters
the strap apertures rests against the head of the buckle near its
opening and is deflected by the strap. The tongue is typically a
cantilever attachment to the buckle-like head, which is inadequate
in most harnessing applications.
Representative harnessing devices are disclosed in U.S.
patents 515,747; 2,977,145; 3,030,131; 3,102,311; 3,106,028;
3,127,648; 3,140,139; 3,189,961; 3,339,246; 3,368,247; 3,486,201;
æ
3~
3,457,598; 3,537,146; Re 26,492, 3,542,321; 3,588,962; 3,598,442;
3,6Q5,199; 3,627,300; 3,654,~69; 3,660,8~9; 3,731,347; 3,766,608;
3,816,878; 3,840,246; 3,872,547 3,887,965; 3,906,593; 3,908,233;
3,949,449; 3,952,373; 3,965,538; 3,991,444; 3,996,646; 4,001,898;
4,003,106; 4,0~3,288; 4,128,919; 4,135,749; 4,136,148; and
~,137,606.
In order to avoid and overcome many o-E -the difficulties
associated with the foregoing kinds of harnessing devices, ladder
straps and associated locking tangs have been developed of the
kind disclosed in U.S. patent 3,766,608, which issued October 23,
1973. The ladder strap device represents a significant
improvement over the serrated strap and other harnessing devices.
It can accomplish substantially the same functions as a serrated
strap device at a considerably lower cost. The ladder strap can
be produced with a significant saving in material and can be
strengthened by stretching.
Notwithstanding its advantages, however, the ladder strap
is not suitable for every bundling application. The precision
with which the ladder strap tie can be adjusted is controlled by
~0 the spacing between its rungs. Since it is advantageous for the
ladder tie to be stretched in order to reorient its molecules, the
stretching often produces a separation of subsequent rungs which
reduces the precision with which such a tie can be used in the
bundling of objects. In addition the ladder tie typically makes
use of a deflectable pawl which extends between adjoining rungs.
The locking of the pawl with -the strap results in the application
of substantially shear pressures to the pawl.
~26~)Z3~
Accordingly, it is an object of the invention to provide
for the secure harnessing of items. A related object is to
achieve secure harnessing without the need for a complex harness
configuration. Other related objects are to ac'nieve a
cost-effective, light-weight, material saving, and precisely
adjustable device.
A further object of the invention is to provide a
harnessing device which is efficient, accurate and rapid to use.
A related object is to provide a suitable structure without an
undue increase in bulk~ Another related object is to overcome -the
difficulties associated with harnessing devices. Still another
related object is to produce a structure that has sufficient mass
for efficient use while being sufficiently light in weight so as
not to interfere with harnessing operations.
A further object of the invention is to achieve secure
anchoring of the strap in the head.
Still another object of the invention is to achieve
precision control over the strap configuration in order to realize
precise bundling of objects.
SUMMARY OF THE INVE~TIO~
In accomplishing the foregoing and related objects -the
invention provides a harnessing device with a locking head and an
attached strap. The device is fabricated by molding. At least
one side of the strap desirably includes a set of teeth with a
profile that is controlled by stretching. When the strap is
unstretched it can be locked in the head by virtue of the profile
of the teeth on the strap, or the configuration of a locking pawl
in the head.
;~26az3~
In accordance with one aspec-t of the invention the head
contains a locking pawl for wedging the strap in the head. The
pawl is desirably deflectable but can be stationary when
appropriately proportioned.
In accordance with another aspect of the invention -the
pawl includes a tooth that is engageable with the strap. A
plurality of teeth are desirably located on the pawl. At least
one pawl tooth is used for setting the strap with respect to the
head and at least another pawl tooth is used for effecting -the
desired wedging of the strap within the head. The use of a
plurality of wedging teeth is particularly desirable since this
distributes the load among the wedging teeth.
In one advantageous embodiment of the invention the first
wedging tooth occupies an intermediate position on the portion of
the pawl facing the entry channel for the strap. A second wedging
tooth is provided at the end of the pawl. The pawl advantageously
includes a ramp that extends from the channel entry position of
the head to the first pawl tooth.
The setting tooth or teeth on the pawl preferably acts to
~0 achieve pivoting or pawl rotation during strap insertion. The
wedging teeth preferably are not subjected to any significant load
during strap insertion. This reduces the possibility of damage to
the wedging teeth.
In accordance with still another aspect of the invention
the pawl is desirably secured to the locking head by a hinged
neck. The hinged neck advantageously is at an intermediate
position on the lower portion of the pawl to provide a locking
ledge with respect to the head for both forward and reverse thrust
~26;C~3~
motions of the strap~ The hinged neck is provided wi-th specified
and distinctive pivot points for respective strap insertion and
loading.
The pivot point for strap insertion is on a surface of
the neck facing the channel for strap insertion~ Conversely the
pivot point for strap loading is on the opposite side of the
hinged neck. Each of the pivot points is defined by the
intersection of a linear segment and curvilinear segment. During
loading the operational pivot point is floating in the sense that
as rotation takes place about the pivot point, the latter moves
towards the front of the head and downwardly.
In accordance with yet another aspect of the invention
the channel in the locking head for the entry of the strap
advantageously includes side ledges that facilitate guidance of
the strap in the channel. The locking head also can include, in
the upper wall of its channel, at least one tooth for engagement
with the strap to enhance the locking effect that is achieved
using the locking pawl.
In accordance with a further aspect of the invention the
pawl includes at least one tooth with a trailing edge that is a-t
less ~han a right angle to the principal axis of the channel in
the head. The trailing ramp of the pawl is advantageously at an
acute angle of declination with respect to the principal axis of
the head when the pawl is in its equilibrium rest position.
In accordance with a still further aspect of the
invention the harnessing device includes a pawl connected in the
head channel by a hinged neck at an intermediate lower profile
position. The associated strap of the device does not need to be
~6~z3~
stretched, but advantageously has teeth with a profile that is
controlled by stretching. The hinged neck is desirably near the
lower mid-position of the pawl to provide a locking ledge for both
forward and reverse thrust motions of the strap. The hinge
configuration preferably provides maximum flexibility and suitable
strength, with the remaining pawl design and related structure
providing the necessary strength.
In accordance with still another aspect of the invention
the strap contains a double set of teeth, one on each side of the
strap, each with profile that can be controlled by s-tretching. It
is desirable for the teeth to be symmetrical with respect to the
principal axis of the strap, and for the strap to include side
rails at its edges. Although the side rails can be omitted from
one or both sides of the strap, the side rails serve an important
function in molding or guiding the molten plastic to suitable
portions of the strap. This is particularly important where the
finally stretched strap will have thin webbed sections between
adjoining teeth.
In accordance with an additional aspect of the invention,
when one or more side rails are included at the edges of a
stretchable strap, they ha~e a higher profile than the teeth prior
to stretching. It is desirable for the strap to be stretched so
that the side rails become tangen-tial to the peaks of the teeth
after stretching.
In accordance with still another aspect of the invention
the teeth of the strap have a curved trailing edge which is
desirably produced by stretching a trailing edge that is
substantially at a right angle with respect to the principal axis
~ 2~C)23~
of the strap. It is also desirable for the teeth of the strap to
have inclined ramp leading edges. Successive ones of the teeth
are interconnected by a web which is narrower than the maximum
height of ~he teeth. The connecting web advantageously has a
substantially uniform thickness. It is particularly desirable for
the web to lie along the central axis of the strap and to be
symmetrical]y positioned.
In accordance with ye-t another aspect of the invention
the harnessing device is fabricated by a rnolding operation in
which teeth are provided on opposite sides of the strap. The
molding can also provide for the formation of side rails at one or
more edges of the strap, with a higher profile than the associated
teeth. The strap can then be subjected to a stretching step to
reduce the profile of the rails relative to the -teeth. In an
advantageous embodiment the strap is stretched until the profile
of the side rails is tangential to the peaX of at least one tooth.
In accordance with a still further aspect of -the
invention the strap is molded with teeth having a partial flat
that is parallel to the axis of the strap and is converted to a
rounded profile by stretching. The partial flat serves the
important role of allowing the strap to be realized with teeth of
substantially uniform height. The molding step desirably includes
provision for molding of the strap with successive teeth connected
by a web which is narrower than the maximum height of the teeth.
Molding can be followed by the step of stretching the strap to
elongate the web that interconnects successive ones of the teeth.
When stretching during production is accomplishedl strap
flexibility is readily achieved during use. Thus, the strap will
)23~
stretch to a degree when wrapped around a bundle, and when the
wrapping force is released, the stretched strap will retract
thereby more ef~ectively achieving the locking action
characteristic of the design.
The strap is used to encircle items to be bundled and
desirably extends at an angle from the locking head with respect
to the principal axis of the guide channel in the head. The
profile of the teeth on the strap is shaped to reduce the force
required for insertion of the strap in the head and to limit the
tendency of thrust applied to the head to fracture the pawl.
In accordance with still another aspect of the invention,
the teeth located on the strap near the head are spaced so that
the stretched strap is operative even with respect to teeth that
lie at or near the transition between the head and the toothed
portion of the strap. For that purpose the spacing of the
initially positioned teeth is increased above that of the
remaining teeth on the strap.
In one embodiment of the invention the intertooth
interval of the unstretched strap is about 0.020 of an inch, while
the intertooth interval of the preliminary teeth near the end of
the strap is increased by 0.005 of an inch to 0.025 inch for the
preliminary teeth of the strap. The result upon stretching is an
effective intertooth interval at the end portion of the strap
which is substantially the same as the intertooth interval along
the intermediate portion of the strap. It is to be noted that the
effective intertooth interval for the teeth nearest the head is
- not the same as the spacing between teeth, but instead is the
usable interval between teeth taking into account the curvature
that occurs with the preliminary teeth on stretching.
With the foregoing discussion in mind, in a broad aspect,
the present invention relates to a harnessing device comprising:
a locking head containing a pawl, and a strap attached to said
head, said pawl containing a plurality of teeth and said strap
containing a plurality of teeth engagable with the teeth of said
pawl to lock said strap in said head, the pitch and surface
profile of the teeth on said strap being substantially different
than the pitch and surface profile of the teeth on said pawl.
DESCRIPTION OF THE D~AWINGS
Other aspects of the invention will become apparent after
considering several illustrative embodiments taken in conjunction
with the drawings in which
FIGURE lA is a perspective view of a bundling device in
accordance with the invention;
FIGURE lB is an enlarged plan view of a fragmentary portion of
the head region of the strap of FIGURE lA in its stretched
condition illustrating the spacing of the initial teeth on the
strap to permit tight bundling;
FIGURE lC is a fragment of an unstretched strap corresponding to
FIGURE lB showing the intertooth interval of the preliminary
teeth as compared with the intertooth interval of the remaining
teeth on the strap;
FIGURE 2A is a plan view of the device of FIGURE 1 in its
extended unbundled condition before the stretching of its strap;
~26V23~
FIGURE 2B is an enlarged fragmen~ary plan view of the head
portion of the strap;
FIGURE 3 is a side sectional view of the bundling device o~
FIGURE 2, including an enlarged fragment showing the unstretched
teeth of the strap;
FIGURE 4 is a side sec~ional view of the strap portion of FIGURE
3, after stretching, showing the control exercised over the
profile by stretching;
FIGURE 5A is a side sec~ional view of the head portion of the
bundling device showing its strap in the course of being
inserted;
FIGURE 5B is a side sectional view of the head portion of FIGURE
-9a-
3~
5A showing the strap in its equilibrium condition after insertion;
FIGURE 5C is a side sectional view of the head por-tion of FIGURE
5B showing the interrelation between the teeth of the strap and
the locking pawl when reverse thrust is applied to the strap; and
FIGURE 6 is an enlarged cross sectional view of a portion of the
head of the strap shown in FIGURES lA, 2A, 3 and 5A through 5C
showing constructional details for the interrelationship among the
head tooth, the pawl setting tooth, the pawl wedging teeth, and
the pivots for the hinged neck of the pawl.
DETAILED DESCRIPTI0~1
As shown in FIGURE 1, a harnessing device 10 in
accordance with the invention includes a head 20 and an attached
strap 30. The strap 30 is in the form of a toothed structure with
a set of teeth 32-1 on one side of the strap and a mating set of
teeth 32-2 on the opposite side o the strap. The free end 31 of
the strap 30 includes a tail portion 33 which is insertable into a
channel 21 of the head 20 to bring the strap into engagement with
an internal locking tang or pawl 22.
The preliminary teeth 32-a shown in detail in FIGURE lB
~0 are provided with a deliberate curvature k so that the working
interval d for the preliminary teeth 32-a is the same as for the
rectilinear teeth 32-b on the remaining portion of the strap.
This result is achieved as indicated in FIGURE lC by providing a
greater space between the unstretched teeth 32-a' than for the
remaining teeth 32-b'. Since the teeth of the set 32-a' nearest
the head are subjected to stretching forces along the strap which
are greatest in the vicinity of the side rails 34-1' and decrease
towards the center of the strap, as a consequence of the mass of
--10--
~26~23~
the tab located between the -teeth and the head, the curvature k
illustrated in FIGURE lB results upon stretching of the strap. In
an illustrative embodiment of the invention the first four
preliminary unstretched teeth 32-a' have an intertooth interval of
.025 inch as compared with an intertooth interval of .020 inch for
the remaining unstretched teeth 32-b'. It has been discovered
that in the stretching process the preliminary teeth 32-a' near
the head are subjected to greater strPtching along the side rails
34-1 and 34-2 than along the central portion of the strap 30. The
result is the curved bow with the curvature k shown in FIGURE lB.
It will be appreciated that the number of teeth that are subjected
to irregular stretching depends upon the transition from the head
to the teeth of the strap as shown in FIGURE lB. In some
situations it is desirable to graduate the spacing among the
preliminary teeth by, for example providing an interval of .025
inch for the first two teeth, followed by a successively reduced
interval, e.g. .024; .023; .022; .021 and finally a constan-t
interval of .020 for the remaining teeth.
It is to be noted further that the tail portion 33 as
shown in FIGURE lA includes a plurality of stretching anchors
illustratively three in number designated 33a which serve as
anchor points for the strap with respect to the head during
stretching. The stretching anchors 33a are of the same width as
the rails and are configured to prevent any inadvertent deflection
of the pawl upon insertion of the strap into the channel of the
head. Only the stretching anchors on one side of the strap are
visible in FIGURE lA; it will be understood that a similar set,
symmetrically positioned, is disposed on the other side of the
~llZ6;(~23~
strap.
As indicated in FIGURES 2A and 3 the pawl 22 is desirably
joined to a lower wall 23-1 of the head 20 by a neck 22n. The
neck 22n is connected to the pawl 22 at an intermediate position
to reduce any shear tendency by the pawl during the applica-tion of
either a forward or reverse thrust to it. This i5 in part by
virtue of the bulges of the pawl 22 extending beyond either side
of the neck 22n.
Referring in particular to FIGURE 2A, it will be noted
that the neck 22n includes side surfaces positioned adjacent side
wall shoulders 24. In accordance with a preferred form of the
invention, the side surfaces are disconnected from the shoulders
to provide maximum flexibility for the pawl as indicated in de-tail
in FIGURE 2B. While this would appear to sacrifice pawl strength
in that there is a reduced cross section of material connecting
the pawl to the head this is not in fact the case. Pawl strength
is not of significant concern during the insertion of the strap
into the head, and in fact the preferred design of FIGURE 2B helps
to reduce the minimum insertion force. During loading, upon strap
~0 release, the support afforded by the wedging teeth provide a
sufficiently strong coupling of the strap to the head that there
is little danger of pawl failure.
As a result, the deliberate disconnection of the pawl
from the side wall shoulders 24 at positions 26 as shown in detail
in FIGURE 2B enhances pawl flexibility without any detrimental
reduction in pawl strength.
The teeth 22t-1, 22t-2, and 22t-3, which serve respective
'`setting" and "wedging" functions are shown in detail in FIGURE 3
-12-
23~
on the upper profile of the pawl 22. The setting tooth 22t-1 is
trapezoidal. It has a leading point formed by the intersection of
a ramp surface with a flat that is desirably parallel to the axis
of insertion of the strap. The trailing edge of -the tooth 22t-l
is substantially vertical. The tooth 22t-l serves to properly
position the strap, after insertion, with respect to the upper
wall 23-2 of the head 20.
Following the setting tooth 22t l is the first wedging
tooth 22t-2 which lies at an intermediate position of the pawl 22
before a second wedging tooth 22t-2 at the trailing edge of the
pawl. The first wedging tooth 22t-2 has a tip formed by an
intermediate flat of the pawl and a trailing edge which is at an
angle less than 90 when the pawl is in equilibrium, i.e. with no
strap inserted. The second wedging tooth 22t-3 at the trailing
edge of the pawl is at the intersection of a trailing flat or ramp
of ~he pawl, which in equilibrium slopes downwardly from the axis
of insertion for the strap. The trailing edge of the second
wedging tooth 22t-3 is also at an equilibrium angle less than 90,
with the angle for the second wedging tooth 22t-3 being less than
for the first wedging tooth 22t-2. It is the wedging teeth 22t-2
and 22t-3 which provide the desired wedging function by which the
strap 30 is properly located in the head 20.
The opposite wall 23-2 of the head 20 includes a locking
tooth 23t. This tooth has a trapezoidal profile similar to that
of the setting tooth 22t-1 on the pawl 20, except that it is
stationary. Accordingly the locking tooth 23t has a leading point
formed by the intersection of a downwardly inclined ramp and a
flat, and a trailing point formed by the intersection of the flat
-13-
3~
with a trailing edge that is perpendicular to the axis of
insertion of -the strap 31.
In use, the harnessing device 10 is looped about objects
to be bundled, with the strap 30 assuming the initial
configuration shown in FIGURE 1. To complete the bundling the
tail portion 33 is inserted into the channel 21 of the head 20, as
explained in detail below with reference to FIGURES 5A through 5C.
In order to promote the wedging of the teeth of the strap
within the head, as well as the engagement of the strap with the
teeth 22t-1, 22t-2, 22t-3 and 23t, the teeth 32-1 and 32-1 are of
a controlled configuration which is determined by the way in which
the strap is stretched during manufacture.
The individual teeth of the unstretched strap of FIGURE 3
have a prescribed profile with respect to the principal axis of
the strap. There is a trailing vertical edge 32v', a flattened
upper edge 32f' and a sloping leading edge 32s'. The angle of
slope of the edge 32s' is desirably about 45 with respect to the
principal axis of the strap 30. The flattened portion 32f' of the
tooth is about 1/3 of the overall tooth depth. The height of the
vertical portion 32v' is greater than approximately 1/2 of the
width of the web 32w'. The side rails 34-1 and 34-2 extend beyond
the respective sets of teeth 32-1' and 32-2' to provide a margin
which is approximately the same as the height of the unstretched
trailing edge 32v' with respect to the surface of the web 32-w'.
Also shown in FIGURE 3 in section is a comparison of the
preliminary unstretched teeth 32-a' with the remaining teeth
32-b'. As noted previously in conjunction with FIGURE lC the
first four teeth of -the preliminary set 32-a' have a greater
-14-
~z~
spacing than the remaining teeth 32-b'. It is this facing which
produces the result illustrated for the teeth 32-a, as compared
with the teeth 32-b in FIGURE lB.
The strap 30' molded as shown in FIGURE 3 can be used
with the locking head 20 if suitably modified. However, the
proportions shown for the locking head 20 in FIGURES 2 and 3 are
intended for accommodating the strap 30' after stretching. The
result o stretching is indicated in FIGURE 4, providing a
reduction of the profile of the side rails 34-1 and 34-2 to be
approximately tangential wi-th the peaks of the stretched teeth
32-1 and 32-2. It is to be noted that the unstretched side rails
34-1' of FIGURE 3 are significantly wider than the unstretched
tooth portion of the strap. This increase in width is desirable
to facilitate the filling of th~ mold. A significant problem that
is encountered in molding is the provision of a sufficiently large
cavity to fill the entire mold. The enlarged unstretched side
rails 34-1' provide suitable channels for assuring the filling of
the entire mold and the realization of the stretched strap with a
web 34w (as indicated in FIGURE 4) which imparts the desired
~0 flexibilty to the strap. It will be appreciated that the control
over mold filling is readily accomplished with the side rails
34-1' by increasing their lateral dimension to the extent desired
for proper filling. Thus the width of the side rails can be
altered to accommodate the filling of any length of strap and a
corresponding change in the head to accommodate the widened side
rails is made. The trailing edge 32v' of FIGURE 3 becomes rounded
trailing edge 32v in FIGURE 4. A similar rounding effect takes
place to convert the flat surface 32f' of FIGURE 3 into the
--15--
23~Z
rounded tangential surface 32f of FIGURE 4. The sloping surface
32s' of FIGURE 3 is merely extended by the stretc'ning and becomes
the extended sloping surface 32s of FIGURE 4. The web 32w' is
reduced in width forming the stretched web 32w which extends
between adjoining teeth.
The strap teeth configuration is preferably not
complementary in either spacing or shape when compared with the
teeth 22t of the pawl. The strap engaging edges of the respective
teeth 22t-1, 22t-2, and 22t-3 are more closely spaced than
corresponding points of adjacent strap teeth 32f. Moreover, the
pawl teeth edges are relatively sharp when compared with the
rounded teeth of the strap. In practice, the spacing of the pawl
teeth comprises from 50 to 90 per cent of the spacing of the strap
teeth, preferably between 60 to 80 per cent. It will be
appreciated that the relative spacing can be varied depending upon
the degree of stretching imparted to the strap.
The consequences of inserting the stretched strap 30 into
the locking head 20 are illustrated in FIGURES 5A through 5C.
FIGURE 5A shows the strap 30 in the course of being fed through
the channel 21 in the direction indicated by the arrow A. The
engagement of the sloping surface 32s of the teeth 32-1 with ramp
surface 22r of the locking tang 22 causes the locking tang to
pivot about its neck portion 22n so that the lower surface 22s of
the pawl 22 approaches the surface of the wall 23-1. During
insertion of the strap 30 the side rails 34-1 tend to be guided by
the shoulders 24 of the head 20 as shown in FIGURE 5A and in
FIGURE 2.
-16-
~L2~;~23~
During strap insertion, the setting tooth 22t-1 also
serves as the means for achieving pivoting or rotating of the pawl
22. As successive strap teeth 32 engage the pawl, the pivoting
movement substantially prevents contact of a preceding strap tooth
32 with wedging tooth 22t-1. Accordingly, there are little or no
forces applied to the wedging tooth during strap insertion whereby
damage to the wedging tooth is avoided. The tooth is, therefore,
exclusively used for the locking function.
When the forward motion of the strap into the loclcing
head is terminated the locking tang 22 returns to its equilibrium
position as shown in FIGURE 5B. In this position the strap 30 has
its outer side rails 34-2 pushed towards upper ledges 25 that
straddle the internal tooth 23t in the head 20 as shown in FIGURE
2. As further indicated in FIGURE 5 the setting tooth 22t-1 of
the pawl 22 is positioned between two of the teeth 32, while the
locking tooth 23t in the head 20 is similarly positioned between
corresponding upper teeth 32-2.
The first wedging tooth 22t-2 has its tip in approximate
alignment with the lower surface of the side rail 34-1. The
~0 remaining wedging tooth 22t-3, when the pawl 22 is in its
equilibrium position as shown in 5B, is sligh-tly below the ledge
24. It will be seen that the ledge 24 is positioned with respect
to the channel of insertion to permit a tight clearance of the
head tooth 23t (FIGURE 5A) in order to prevent any adverse
retrograde activity with respect to the pawl while simultaneously
permitting clearance of the head tooth 23t. The result as shown
in FIGURE 5B is that the ledge 24 is positioned well below the
lower surface 34-1 of the strap 30 when the pawl 22 is in its
-17-
12~iV23~
equilibrium position wi-th the strap inserted.
Reverse thrust is applied in the direction C as shown in
FIGURE 5C, as when the strap 30 inserted into the head 20 is
released under load. The deflectable pawl 22 pivots in a
counterclockwise direction about the pivot point P2 of the neck
22n. This brings the flat of the first wedging tooth 22t-2 into
contact with the first tooth 32f. Further loading tends to
produce compression of both the upper and lower portions of the
~irst tooth 32f. The lower compression is by the flat of -the
setting tooth 22t-1 and the upper compression is by the flat which
trails the head tooth 23t. Simultaneously the pivot P2 floats
downwardly and towards the front of the head 20. When the loading
action is completed, the first wedging tooth 22t-2 is locked into
the web of the strap 30 and the second wedging tooth 22t-3 i5
locked into the web following the succeeding tooth, while the
setting tooth 22t-1 becomes slightly disengaged from the strap.
The wedging action of the wedging pawl teeth 22t-2 and 22t-3 also
produce a corresponding wedging action of the locking tooth 23t in
the upper portion of the web 32w. In the usual wedging situation,
the pawl 20 has a position similar to that indicated in FIGURE ~C,
with the trailing edge surface 27 of the pawl (forming the
trailing surface of the wedging tooth 22t-2) occupying a position
that is substantially perpendicular to the axis of insertion of
the strap. The setting tooth 22t-1 also tends to be in alignment
with the locking tooth 23t. If there is an appreciable increase
in reverse thrust (due to an unusually heavy load) the pawl 20
continues its counterclockwise rotation and the wedging action of
the teeth 22t-2 and 22t-3 is accentuated. The gap 29 between the
-18-
:
32
front of the pawl and the neck 22n tends to be reduced until it is
eliminated.
The setting, wedging and locking functions of the teeth
22t-1 and 22t-2 on the pawl 22 and the too-th 23t in the head 20
are clearly evident from FIGURES 5A-5C, particularly 5C. As seen
in FIGURE 5C the setting tooth 22t-1 serves for the proper
positioning of the strap 30 against the locking tooth 23t in the
upper wall 23-2 of the head 20. In addition the wedging teeth
22t-2 and 22t-3 assure the proper locking action of the strap
against the head by biting into the web 32w and acting with the
flat of the pawl to force an upper tooth 32f against the locking
tooth 23t. The teeth 22t-2 and 22t-3 bite into wedge portions 32w
as opposed to engaging a tooth 32f because of the
non-complementary tooth spacing previously discussed.
The setting, wedging and locking actions are particularly
important in the case of a stretched strap. The stretching
operation controls the profile of the teeth 32-1 and 32-2 and
forms them to facilitate proper positioning of the strap in the
head. In addi-tion the stretching operation lengthens the web 32w
and increases its tensile strength so that the wedging teeth 22t-2
and 22t-3 promote the locking of the strap in the head by contact
of the web as shown in FIGURE 5C. Finally, the stretching
substantially reduces the thickness of the web so that a preferred
configuration is achieved wherein the web has a substantially
uniform thickness, extends substantially uniformly between
adjacent teeth, and is narrower than the maximum height of a
tooth.
It is to be noted that the locking action of the tooth
--19--
3,~
23t in the upper wall of the head 20, and of the teeth 22t-1,
22t-2 and 22t-3 in the upper surface of the pawl 22, are merely
advantageous and not necessary for suitable operation of the
harnessing device. With any or all of the teeth 23t, 22t-1, 22t-2
and 22t-3 eliminated the pawl 22 still produces a wedging action
by virtue of its forcing the upper surfaces of the teeth 32-2
against the wall surface 23-2. There is a similar wedging against
the upper face of the pawl 22.
A particularly advantageous configuration of the pawl 22
with respect to the head 20 is shown in detail in FIGURE 6. The
setting tooth 22t-1 has a ramp surface 22r which desirably forms
an angle of about 45 with respect to the axis of insertion I for
the strap. The flat associated with the second tooth 22t-2 is
substantially parallel with the axis of insertion I and is
desirably at a slight angle of declination on the order of 1/4.
The angle formed by the trailing edge for the first setting tooth
22t-2 is on the order of 80 with respect to the axis of
insertion. The flat associated with the second setting tooth
22t-3 has an angle of declination on the order of 4 and the angle
formed by the trailing surface is on the order of 30. The pivot
point Pl which is operative as the strap is inserted lies at the
intersection of a rectilinear segment forming an angle of
approximately 8 with respect to the axis of insertion and a
radius of curvature which extends to a line segment positioned
with an angle of declination of approximately 15. The floating
pivot P2 which comes into operation during loading of the strap
(see FIGURE 5C) is at the intersection of a flat which is
substantially parallel with the axis of insertion I and a circular
-20-
3~
arc whlch opens to approxima-tely 45 with respect to the ramp 22r.
The knee of -the ramp 22r is rounded to provide a suitable loading
surface for extreme loading of the strap where maximum revexse
thrust is applied. Entry of -the strap is facilitated by a
downwardly positioned ramp 20r which forms an angle of
approximately 15 with respect to the axis of insertion. The flat
following the head tooth 23t is desirably at a slight angle of
elevation on the order of 1/4 with respect to the axis of
insertion.
It is to be noted further that the head 20 and the pawl
22 are merely exemplary and that a harnessing device with an
unstretched strap having the profile shown in FIGURE 3 or a
stretched strap having a profile like that of FIGURE 4 can be used
with a wide variety of other locking heads, including locking
heads in which the pawl is stationary. Such a pawl can be
temporarily deformed by pressure without requiring actual
pivotting of the pawl about a neck.
In providing the harnessing device of FIGURE 1, the
unstretched device of FIGURE 2 is molded of stretch orientable
material, such as nylon, polypropylene, polyurethane and the like.
The teeth, strap and side rails are proportioned to permit
subsequent stretching, which takes place by applying stretching
stress between the tip 33 and the head 20 along the major axis of
the strap. The results are the controlled tooth profile strap of
FIGURES 1 and 4.
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 for
-21-
~26~)Z3~
illustration only and that various changes in parts, as well as
the substitution of equivalent constituents for those shown and
described, may be made without departing from -the spirit and scope
of the invention as set forth in the appended claims.
-22-
.
