CA1038602A - Plastic seal - Google Patents

Abstract

IMPROVED PLASTIC SEAL
Abstract of the Disclosure The specification discloses a seal having a housing, a bore extending into the housing, a locking socket in the bore, a tie member having a free end and an end connected to the housing, and a locking head at the free end of the tie member. The locking head can be inserted into socket through one end of the bore to lock the seal. The socket has an inwardly projecting locking element and the locking head has a head portion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section.
The head portion is dimensioned to elastically deflect the locking element during insertion of the head portion in a locking direction so that the locking shoulder snaps in behind locking surface portions of the locking element when the head portion is inserted into the socket. Weakening means are provided adjacent the extreme free end of the head portion ensuring that the head portion expands transversely to the locking direction in response to force components in a direction opposite the locking direction. This provides a tamper proof seal which can be manufactured by a simple single molding step.

Description

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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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, .
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 . . .
~ -present invention.
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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~

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 _6-103866)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. ~ -- . ~ . .

Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A seal comprising: housing means, a bore extending in said housing means with first and second bore ends, locking socket means arranged in said bore in said housing means, a tie member having a free end and an end operatively connected to said housing means, and a locking head means at the free end of said tie member, said locking head means being insertable into the socket means by way of said first bore end to lock the seal, the socket means including at least one in-wardly projecting locking element and the head means including a head potion with a locking shoulder formed between the head portion and an adjoining section with smaller cross-section; said head portion being dimensioned to elastically deflect the at least one locking element during insertion of said head portion 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 means, wherein weakening means are provided adjacent the extreme 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 di-rection.

2. A seal according to claim 1, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said bore, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

3. A seal according to claim 1, wherein said weakening means is a transverse bore through said head portion, and wherein that part of said head portion adjacent said transverse bore expands trans-versely in response to said force component opposite said locking direction.

4. A seal according to claim 3, wherein the extreme free end of said head portion which faces said second bore end with said head means in a seal locking position includes portions which are angularly inclined with respect to a centerline through said bore, said angularly inclined head portions being arranged to provide a non-symmetrical spacing of points of the surface of said extreme free end of said head portions from said second bore end with respect to said centerline.

5. A seal according to claim 2, wherein the housing means is con-structed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

6. A seal according to claim 4, wherein the housing means is con-structed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

7. A seal according to claim 6, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

8. A seal according to claim 1, wherein the housing means is constructed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetect-able application of backing forces at said housing means adjacent said first bore end.

9. A seal according to claim 3, wherein the housing means is con-structed with thinner walls surrounding said bore adjacent said first bore end than adjacent the socket means so as to limit undetectable application of backing forces at said housing means adjacent said first bore end.

10. A seal according to claim 3, wherein said bore is a longitudinally extending bore, and wherein said at least one locking element includes a plurality of prong-like locking elements symmetrically arranged with respect to the centerline of said bore.

11. A seal according to claim 1, wherein the housing means is con-structed such that when in a seal locking position, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.

12. A seal according to claim 6, wherein the housing means is con-structed such that when in a seal locking position, the ratio of the distance between the innermost end of the extreme free end of said head portion and the second bore end and the smallest cross-section dimension of said second bore end is such as to substantially preclude access to the locking elements from said second bore end.

13. A seal according to claim 1, wherein the housing means is provided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking element for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said locking direction.

14. A seal according to claim 6, wherein the housing means is pro-vided in said bore means with inwardly projecting means at least in the area behind the locking surface portion of the at least one locking ele-ment for substantially minimizing the freedom of movement of the head portion in the bore means, when in the locked position thereof, in a direction transverse to said locking direction.

15. A seal according to claim 1, wherein said housing means has a substantially longitudinally extending cylindrical outer configuration, and wherein said tie member is constructed as a flat member having a maximum dimension corresponding to the diameter of the housing means, said housing being provided with a stop shoulder in said socket means for limiting the extent of insertion of said locking head means into said socket means, said tie member being attached to said housing means in the plane of the stop shoulder.

16. A seal according to claim 10, wherein said bore is of cylindrical stepped cross-section along the length thereof from said first bore end to said locking elements.

17. A seal according to claim 3, wherein said bore in said housing means extends completely through said housing means with both said first and second bore ends opening to the outside of said housing means.

18. A seal according to claim 1, wherein said weakening means Includes a weakening bore extending transversely through said head portion, said weakening bore serving as an intentional transverse expansion section for said head portion in the event of excessive tampering forces on said extreme free end of said head portion.

19. A seal according to claim 18, wherein said bore in said housing extends completely through said housing means with both said first and second bore ends opening to the outside of said housing means.