Note: Descriptions are shown in the official language in which they were submitted.
103860Z
BACKGROUND AND SUMMARY OF THE INVENTION
The present application is related to my U.S. Patent 3,712,655
dated January 23, 1973 and is a division of Canadian application
Serial No. 174,955 filed June 26, 1973.
The above-mentioned patent related to an improved plastic
seal which was relatively tamper proof and which could be manufactured
in a single moIaing operation~ One of the important features of the seal
of the above-mentioned patent related to the configuration of the housing
bore surrounding the locking socket as open at both ends and with a
ratio of length to diameter such as to substantially impede access to
the locking prongs when the seal is in the closed condition. The con-
struction of the housing bore as open at both ends facilitated the single
step molding operation, since no additional steps were needed to close
off the ends of the housing and socket bore. The construction of the
length to diameter ratio so as to be~sufficiently large made it rather
difficult to obtain access to the locking head andlor locking prongs to
wiggle the locking head free from the locking prongs without being
detected. The above-mentioned patent also disc~;osed an arrangement
of longitudinally extending flutes arranged in the housing bore to abutt- -
ingly engage the sides of the locking head when in the lacked position so
as to substantially preclude transverse~movement of the locking head in
the event access to the locking head was obtained by a pencil, ballpoint
pen or theelike.
My invention disclosed and claimed in the above-mentioned patent ex-
hibited a substantial i~provement over prior art arrangements with respect
to simplicity of manufacture combined with tamper proofness.
The invention of the above~mentioned patent was particular ad-
vantageous in substantially precluding undetectable transverse movement of
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either the locking head or the locklng fingers. A further
possibility of tampering with such a ~eal involves the applica-
tion of very large axial forces on the locking head with respect
to the socket housing to physically force the locking head past
the locking fingers in a direction substantlally opposite the
locking direction. For example, if a sufficiently firm backing
coult be provided at the socket housing and a sufficiently
large axial force could be applied on the locking head, a seal
could, in some instances, be forced open in spite of provisions
preventing transverse move~ents of the locking head and locking
fingers.
The present invention is concerned with improving the
tamper proofness of a seal of the general type disclosed ln the
above-mentioned patent, while still maintaining the simple
single molding step manufacturing possibilitles. The present
invention is particularly directed to improving tamper proof-
~ess with respect to unlocking by application of axial forces
in the direction of the longitudinal centerline of the socket
snd locking head. The improved tamper proofing means of the
present invention invol~e several constructional features of
the socket and of the locking head, which features operate alone,
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in con~unction with one another, and in conjunction with features
of the above-mentioned patent, to substantially imprave the
tamper proofness of a seal having a bore extending completely
through the socket housing.
To ~his end the invention consists of a seal comprising:
hou81ng means, a bore extending in said housing means with first
and second bore ends, locking socket means arranged in said bore
ln said housing means, a tie member having a free end and an end
operatlvely connected to said housing means, and a locking head
means at the free end of said tle member~ sald locking head
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means being insertable into tlle socket means by way of said
flrst bore end to lock the seal, the socket means includlng
at least one inwardly pro~ecting locking element and the head
means including a head portion with a locking shoulder formed
between the head portion and an ad~oining section with smaller
cross-section, said head portion being dimensioned to elastically
teflect the at least one locking element durin~ insertion of
said head portlon in a locking direction so that the locking
shoulder snaps in behind locking surface portions of the at
least one locking element when the head portion is inserted
into said socket ~eans, wherein weakening means are provided
ad~acent the extre~e free end of said head portion, said
weakening means including means assuring that said head portion
expands transversely to said locking direction in response to
force components in a direction opposite the locking direction.
The present invention will become more apparent from
the following description. Other aspects of the apparatus
disclosed are claimed in the parent application referred to
above. The following description is to be ta~en iD con~unction ~-
~20 with the accompanying drawings, which shows, for purposes of
illustration only, a single embodiment in accordance with the
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BRIEF DESCRIPTION OF THE DRAWIN~S
Figure 1 is an elevational view of an all-plastic padlock seal in accord-
ance with the present invention, illustrating the socket and housing thereof in
axial longitudinal cross-section~
Figure 2 is a bottom plan view of the seal of Figure l;
F~gure 3 is a partial cross-sectional view taken along line III-III of
Figure l;
Figure 4 is a view similar to Figure 2, and showing certain details
thereof on an enlarged scale;
Figure 4a is a cross-sectional view taken along line IV-IV of Figure
3; and
Figure 5 is a partial cross-sectional view taken along line V-V of : :
Figure 4.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawings, wherein like reference numerals are ~:
used throughout the various views to designate like parts, a~d more partic-
ularly to Figures 1 to 3, a flexible tie-member 1 has one end connec~ed to
a housing 2 and the other free end connected to a locking head 3. The housing ~:
2 is provided with a longitudinally extending bore 4 extending completely through .:
2~ the housing 2 and arranged symmetrically with respect to longitudinal center_
line 5. Near the end of the housing 2 attached to the tie-member 1, a locking
socket arrangement is provided for lockingly accepting the locking head 3
during locking of the seal.
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The locking head 3 includes a cylindrical stop member portion 6 which
exhibits stop surface 6' engageable with correspondingly shaped stop shoulder
surfaces 7 of the locking socket. Immediately outwardly of the stop member 6,
a cylindrical section 8 is provided on the~locking head 3. A conical part 9 is
arranged between the cylindrical part 8 and the locking shoulders 10. A
second cylindrical portion ll extends from shoulders lO outwardly to the planar
end surface 12 of the locking he ad. This planar surface 12 extends at an angle
of approximately 45 or less (steeper incline than 45) with respect to the
longitudinal centerline 5 when in the seal locking position. A weakened section
13 in the form of a transverse hole is provided in the cylindrical part ll between
tapered surface 12 and locking shoulder 10.
The housing 2 is formed of a cylindrical sleeve 14 open at the bottom -
end and provided at the top with a flaring section 15. The thickness of the
housing walls at the extreme end of the flaring section 15 are such that any
substantial "backing forces" BF (Figure 1) will show visible tampering signs.
Since~flaring section tapers to cylindrical sleeve 14, no transverse backing
shoulder is provided. The upper po~tion 16 of the longitudinal bore 4 has a
diametric dimension slightly larger than the diametric dimension of stop
shoulder 6. Intermediste portion 17 of bore 4 is delimited by the edges of
lo~king fingers 18 and has a diametric dimension slightly larger than the -~
maximum diametric dimension of the cylindrical part 11 of the locking head,
but smaller than the diametric dimension of the stop 6 such that the locking head
3 can be inserted into the bore 4 with the head por~ion 11, 12, tapering section9 and cylindrical section 8 until the stop 6 abuts against the stop shoulder 7 of
the housing. The prong-like locking fingers 18, each of which defines on the
inside thereof a par~ of a frustro-conical surface co~plementary to the surface
of section 9, extend inwardly and downwardly within the housing 2, thus forming -
a circumferentially interrupted tapering section 19 of frustro-conical shape. The~
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1038602
length of the frustro-conical section 19 formed by the locking fingers is
substantially equal to or very slightly larger than the length of the taperings
section 9 and the length of the cylindrical section 17 is substantially equal
to or very slightly larger than the length of the cylindrical section 8 so
that the head portion 11, 12 snaps into its locked position with the locking
shoulder surface 10 engaging against the end surfaces 18' of the prong-like
fingers 18 when the stop member surfaces 6' are in abutting engagement
with stop shoulder 7.
Since the bore 4 in seal housing 3 extends completely through the
housing, there is a possibility that one could gain access to the tip of the
locking head to attempt to unlock the seal without showing any signs of
tampering. In the above-mentioned patent, the ratio of the length L to the
diameter D (see Figure 3) was made relatively large, for example greater
than 5:2, to preclude access to the prongs 18, particularly if the diametric
dimension D is relatively small, for example, of the order of a quarter
inch or less. The above-identified patent also suggested the provision of
longitudinally extending inwardly pro~ecting flutes 21 arranged at least ;-
imm~diately ad~acent the inserted locking head portion to limit traasverse -~
movement of the locking head. The above-mentioned patent also suggested
that a tapering part~ correspoinding to part 9, could lead to a weakened
portion causing intentional failure in the event of excessive force on the high
member and locking head.
The present invention includes further tamper proofing structural
features and above and beyond those suggested in the above-mentioned patent.
First, the tapering end surface section 12 of the locking head precludes the
application of a large force in the direction of the longitudinal centerline to
unlock the head. That is, a pin or other member inserted through the lower
end of the housing bore 4 would merely slip off the steeply inclined surface 12
making it very difficult to engage the locking head at its centerline to apply
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103866)Z
axial unlocking forces. Forces (EF in Figure 2) at the junction of housing
and tapered section would tend to tilt (dash lines) the locking head to further
prevent unlocking. Also, even if one were able to en8age a pin or the like into
the inclined surface 12 at the centerline ~CF in Figure 2), it would be very
difficult to force the locking head in^only the axial direction since such a pin
would practically always also impart some transverse force components to
cause tilting a jamming of the locking head.
The transverse aperture 13 arranged immediately adjacent the tapering
surface 12 provides for an intentional expansion of the locking head (see dash
lines Figure 2) in the event of excessive tampering forces (EF or CF) on the
tapering surface 12. Consequently, even if one were able to engage the surface
12, the expansion of the locking head would prevent forcing of the locking head
in the axial direction past the locking fingers. Also9 failure of the head at
13 would provide visible evidence of tampering upon a cursory inspection of
the seal.
By arranging the cross-section of stop shoulder 6 to correspond with
cross-section 16 of the upper part of bore 4, both radial and axial ~ovement
of the locking head is precluded by engagement of stop member 6 with shoulder
7~iand ~idewalls 16. Further9 by arranging the longitudinal dimension x of
sldewall portion 16 as no less tha~ the longitudinal dimension y of stop member
6, access to the stop member 6 from outside of the housing is substantially
limited, thereby further precluding radial and axial movement of the locking - -
head with ~espect to the housing.
The connection between the tie-member 1 and the housing 2 is con-
veniently made im~ediately below the level of the tapering section 15 aDd in
liDe with the shoulder 7 so as to minimize the co~plexity of the mold required
for manufacture. An intentional failure aperture 22 may also be provided in
the tie-member immediately ad~acent the stop shoulder 6 so as to cause an
103t36~Z
intentional failure at that point in the event excessive forces are applied to
the tie-member in attempts to pull the locking head out of the houslng by
way of the tie-member. In addition, the weakened section formed by
aperture 22 facilitates intentional breaking of the tie-member when one
wishes to unlock the seal.
It will be readily recognized from the above that the improved seal
according to the present invention provides a substantially completely tamper-
proof structure which can be manufactured by single molding step. ~ny known
suitable synthetic resinous material may be used for the plastic seal of the
present invention and any suitable known molding techniques may be used for
the purpose of molding the same.
While I have shown and described bu~ a single embodiment in accordance
with the present inventionS it is understood that the same is not limited thereto, -
but is susceptible of numerous changes and modifications as known to those
skilled in the art. For example, the var~ous tamper proofing features, such
as the tapered end section 12, the weakened section expansion at 13, and
the thin walled and conically flared housing end 15 could be provided each
alone, or in any combination with one another or with the features of the
above identif~ed patent ~o optimize the tamper proofness of the seal, Further,
the weakened section 13 could be formed by other than cylindrical apertures.
Also, the cross-section of the various parts of the locking head could be of
polygonal construction, rather than cylindrical~ with corresponding polygonal
shaped recesses and openings in the housing 2 as~shown in the above-identified
patent. Thus, it is obvious that the present invention is not limited to the de-
talls descr~bed and show here~n, and I therefore do not wish to be limited to
the same, but intend to cover all such changes and modifications as are en- ~
compassed by the scope of the appended claims. ~ -
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