US3827125A

US3827125A - Threadless fastener system

Info

Publication number: US3827125A
Application number: US00332796A
Authority: US
Inventors: G Matthews
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1973-02-16
Filing date: 1973-02-16
Publication date: 1974-08-06
Anticipated expiration: 1991-08-06

Abstract

A threadless fastener system in which the leaves of a leaf spring fastener radiate from an aperture and are inclined to securely engage a locking shaft inserted into the aperture to prevent manual removal of the shaft. Unlocking of the fastener to permit reuse thereof is provided by an unlocking tongue having an axially slotted hollow cylinder which fits around the locking shaft of the fastener and is moved axially to engage and radially deflect the locking leaves of the fastener to disengage the same from the locking shaft.

Description

0 llnlted States Patent 1191 1111 3,827,125 Matthews 1451 Aug. 6, 1974 [54] THREADLESS FASTENER SYSTEM 3,110,093 ll/l963 Johnson 29/20() H x 3 2. [75] Inventor: Gary B. Matthews, Maplewood, juhmon a 29/200 D Primary Examiner-Thomas H. Eager [73] Assignee: Minnesota Mining and Attorney, Agent, or Firm-Alexander, Sell, Steldt &

- Manufacturing Company, St. Paul, DeLaHunt Minn.

[22] Filed: Feb. 16, 1973 [57] ABSTRACT 211 App] 332 796 A threadless fastener system in which the leaves of a leaf spring fastener radiate from an aperture and are inclined to securely engage a locking shaft inserted [52] US. Cl 29/200 D, 29/200 H, 29/268, into the aperture to prevent manual removal of the 40/20 A shaft. Unlocking of the fastener to permit reuse [51] Int. Cl B23p 19/00, B23p 19/04 thereof is provided by an unlocking tongue having an [58] Flew of Search 29/200 200 200 axially slotted hollow cylinder which fits around the 29/268; 40/20 A locking shaft of the fastener and is moved axially to engage and radially deflect the locking leaves of the [56] References Cted fastener to disengage the same from the locking shaft. UNITED STATES PATENTS l4 Clams 7 Drawi Fi res 3,006,063 10/196] Linan 29/268 X I ng g 1 THREADLESS FASTENER SYSTEM FIELD OF THE INVENTION BACKGROUND OF THE INVENTION Shoplifting is a serious problem both to the merchant whose goods are stolen and to the average consumer who must ultimately bear the expense of the thefts through higher prices. The annual loss in the United States alone is in the billions of dollars. It has been estimated as being between one and four per cent of gross sales.

The most promising anti-pilferage systems presently available utilize a sensitized marker element secured to each object to be detected by instruments which sense signals produced by the marker elements. Such systems are disclosed in US. Pat. Nos. 3,292,080; 3,493,955; 3,665,449 and 3,697,996. These sophisticated systems are capable of detecting the marker elements utilized therewith without causing false alarms.

Obviously, for such anti-pilferage systems to effectively prevent shoplifting it is essential that the marker elements, if visible, be rigid, tough and firmly attached to the goods they protect to prevent their removal by a shoplifter either by hand or with tools that are readily available or easily concealed. US. Pat. No. 3,628,267 is directed to providing such a marker element and attachment. At the same time it is highly desirable that the marker elements be readily removable by a clerk in a manner which permits reuse of both the marker elements and the fasteners.

Until now no such fastening system has been available. Some marker elements have been as easily removed by a shoplifter as by the clerk; others have been extremely difficult to remove both by the shoplifter and the clerk; and some have even remained with the goods when purchased. Where fastener and marker removal have been provided, the fastener either has not been reusable or it has not been replaceable on the marker element when damaged.

SUMMARY OF THE INVENTION The present invention provides a threadless fastener system comprising a leaf spring fastener having a sheet metal base formed with a circular aperture from which a plurality of similar locking leaves radiate, the leaves being inclined to permit insertion of a locking shaft into the aperture perpendicular to the base and movement thereof in only one direction relative to the base. A cylindrical locking shaft is engageable with the locking leaves upon insertion into the base aperture to prevent manual removal of the locking shaft. An unlocking tongue is formed with a longitudinal slot at one end to fit around the locking shaft and a hollow cylinder extends perpendicular to the longitudinal slot and has an axial slot aligned with the longitudinal slot to receive the locking shaft coaxially with the hollow cylinder. The cylinder has an external radius less than the distance the locking leaves radiate from the aperture in the sheet metal base and means are provided for applying a force to move the unlocking tongue with respect to the sheet metal base axially of the hollow cylinder to engage and radially deflect the locking leaves to disengage the same from the locking shaft.

A threadless fastener system is thereby provided in which the fastener is manually engageable, cannot be removed by tools a shoplifter might ordinarily carry and in which the removal tool provided is not readily available or concealed. A marker element or other identification tag can be easily attached and legitimately detached from an article with the fastener being reusable.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawing:

FIG. 1 is a perspective view of a spring leaf fastener unlocking tool constructed in accordance with the present invention;

FIG. 2 is an exploded perspective view of a threadless fastener;

FIG. 3 is a longitudinal elevation cross-sectional view of the threadless fastener of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 3;

FIG. 5 is a longitudinal elevation cross-sectional view of the end of the tool of FIG. 1 and the fastener of FIGS. 2 4 comprising a fastener system constructed in accordance with the present invention;

FIG. 6 is a longitudinal elevation cross-sectional view of a second threadless fastener and FIG. 7 is an elevation view, partially in section, showing a third threadless fastener.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In each of the illustrated embodiments the fastener comprises a sheet metal base 10 and a cylindrical locking shaft 12. The sheet metal base is disk shaped and formed with a central circular aperture 14 from which four similar locking leaves 15 radiate. The locking shaft 12 is preferrably formed of a material having a hardness less than that of the sheet metal base 10 and the locking leaves 15 are inclined to the remainder of the fastener base 10 to permit insertion of the locking shaft 12 into the aperture perpendicular to the base. Upon insertion of the locking shaft into the base aperture 14 the ends of the leaves 15 are pushed back by the locking shaft 12 thereby permitting manual insertion of the locking shaft. Upon attempted manual retraction of the locking shaft 12 the locking leaves 15 gall or score the shaft 12 thereby preventing manual removal thereof from the base 10.

A hand tool 17 for unlocking the illustrated fasteners is illustrated in FIG. 1. The tool 17 is constructed as a pair of pincers with specially formed jaws l9 and 20. The lower jaw 19 is a flat elongate unlocking tongue formed with a longitudinal slot 22 at its free end to fit around the fastener locking shaft 12 and a hollow cylinder 24 extending perpendicular to the slot and the faces of the tongue 19. The hollow cylinder 24 has an axial slot 25 extending its entire length and aligned with the longitudinal slot 22 to receive the fastener locking shaft 12 coaxially with the hollow cylinder 24. The cylinder 24 has an external radius less than the distance the locking leaves 15 radiate from the aperture 14 in the sheet metal base 10. The hollow cylinder 24 will, therefore, engage and radially deflect the locking leaves 15 to disengage the same from the locking shaft 12 when the unlocking tongue is moved with respect to the fastener sheet metal base in a direction axially of the hollow cylinder 24.

The upper jaw 20 comprises means for engaging the fastener to apply a force around the periphery of the leaves in opposition to the unlocking tongue 19. In the illustrated embodiments the fastener includes a protective cap 29 or 52 (see FIGS. 2 and 7) into which the sheet metal base 10 is inserted and secured so that the cap extends over the face of the sheet metal base from which the locking leaves 15 are inclined. The

protective cap

29 or 52 thus engages the sheet metal base 10 around the periphery of the locking leaves 15. And, the upper jaw is a flat elongate tongue which in use engages the top of the protective cap and which through the cap applies a force around the periphery of the leaves 15 in opposition to the unlocking tongue 19. The unlocking tongue 19 is thereby movable relative to the fastener base 10 to deflect the locking leaves and unlock the fastener. Within the scope of the present invention the fastener may comprise the sheet metal base 10 without a protective cap and the upper jaw 20 of the tool 17 may then be formed with structure similar to the protective cap illustrated in FIGS. 2 through 6 to engage and apply a force around the periphery of the locking leaves 15.

Adjacent its pivot pin the tool 17 is formed with interfering surfaces permitting pivotal movement of the jaws l9 and 20 through only a very small angle. The

jaws

19 and 20 are urged apart by a leaf spring 27 between the handles of the tool 17. The illustrated tool 17 is constructed for use with each of the illustrated fasteners, the spacing between the sheet metal base 10 and the top of the

protective cap

29 or 52 in all of the fasteners being the same and access for the lower jaw 19 being provided at the same distance from the top of the protective cap. Thus, the greatest spacing between the upperjaw 20 and the top of the hollow cylinder 24 of the lower jaw 19 is just sufficient to insert the lower jaw 19 beneath the sheet metal base 10 with the hollow cylinder 24 surrounding the locking shaft 12 and the upper jaw 20 extending over the protective cap of the fastener. And, the approach of the jaws l9 and 20 together by squeezing of the handles of the tool 17 is sufficient to move the unlocking tongue 19 with respect to the sheet metal base 10 in a direction axially of the hollow cylinder 24 to engage and radially reflect the locking leaves 15 to disengage the same from the locking shaft 12. Obviously, it makes no difference in unlocking the fastener whether the unlocking tongue 19 or the sheet metal base 10 is moved so long as there is relative movement between the two. For example, the unlocking tongue 19 may be stationarily supported as a cantilevered beam with the fastener being forced against it to release the locking shaft 12.

Referring now to FIGS. 2 through 5 there is illustrated a first embodiment of a fastener. In this embodiment the sheet metal base 10 is press fit into a protective cap 29 such that the exposed face of the base 10 is coplanar with the peripheral edge of the protective cap 29. The locking shaft 12 is terminated by a head 31 to form a tack 32. And, this embodiment includes an axial stand-off or access spacer for the unlocking tongue 19 of the tool 17, which axial stand-off is formed on an identification tag or marker element 33 that it is desired to attach to an article, for example, an article of clothing.

The marker element 33 comprises two layers of a tough rigid plastic between which is sandwiched a sensitized marker material. The upper layer of the marker 33 is formed at one end with a longitudinally extending slot 35 corresponding in width to the flat portion of the unlocking tongue 19. The thickness of the upper layer of the marker element 33 is slightly greater than the maximum height of the unlocking tongue 19 measured at the hollow cylinder 24 to assure access space for the unlocking tongue 19 in the slot 35.

symmetrically with the longitudinal slot 35 the marker 33 is formed with a retaining rail 37 having an overhanging lip to engage the upper surface of a pcripheral rim 38 formed around the protective cap 29. The protective cap 29 is releasably retained on the marker element 33 by the retaining rail 37 when it is slid in from the open end of the retaining rail 37 with its rim 38 under the lip of the retaining rail. Thus, the thickness of the upper layer of the marker 33 at the longitudinal slot 35 therein defines an axial stand-off for the fastener which always permits access to the locking shaft 12 by the unlocking tongue 19 of the tool 17. The lower layer of the marker element 33 is formed with an aperture 40 coaxial with the axial stand-off and the aperture 14 in the sheet metal base 10 to permit insertion of the locking shaft 12 through the marker aperture 40 and into the fastener aperture 14.

A flexible link 42 is provided to link the locking shaft 12 to the marker 33 when it is unlocked and removed from the fastener base 10. The illustrated linking material is a flexible plastic formed at one end with a cross bar which may be bent to pass it through an opening 44 through the marker and which then lays in a transverse recess 45 formed in the upper layer of the marker 33 to attach the link 42 to the marker. The opposite end of the link 42 is formed with a disk which is punctured by the locking shaft 12 to retain the parts together as a single unit.

ln use, it may be desired to utilize the marker 33 to identify an item of clothing 47. The marker element 33 with the protective cap 29 and the fastener base 10 releasably retained thereby is placed against one face of the clothing, the tack 32 is grasped and the locking shaft 12 thereof is inserted through the clothing with the flexible link 42 extending around the edge of the clothing. After insertion through the clothing 47 the locking shaft 12 is inserted through the marker aperture 40 and then into the fastener aperture 14 and engaged by the locking leaves 15 which prevent manual removal of the locking shaft 12 (see FIG. 3). It thus becomes virtually impossible for the marker 33 to be removed from the clothing by the use of ordinary tools without damaging the clothing 47.

When the item of clothing 47 has been sold a clerk may easily remove the marker 33 from the clothing by maneuvering the tool 17 to position the jaws l9 and 20 as illustrated in FIG. 5 and then squeezing the handles of the tool 17 to move the unlocking jaw 19 upward with respect to the sheet metal base 10 of the fastener to engage and radially deflect the locking leaves 15 from the locking shaft 12. The tack 32 may then be removed by pulling on the head 31 thereof. After removal of the tack 32 the flexible link 42 will retain the marker and both parts of the fastener as a single unit for ease of reuse.

After several uses the locking shaft may become scored to an extent which might damage clothing and it may and should then be replaced. And, after many uses the leaves 15 of the sheet metal base may become deformed and it is for this reason that the base 10 and its protective cap 29 are releasably retained on the marker 33 to permit replacement thereof. Since it is unlikely that the protective cap 29 will be damaged beyond use it is also within the scope of the present invention to form the protective cap as a part of the identification tag with the sheet metal base 10 being releasably retained to permit replacement thereof alone.

In one specific example of the embodiment illustrated in FIGS. 2 through 5 the sheet metal base 10 of the fastener was formed of a 0.04 inch thick heat treated spring steel having a hardness of about 35 Rockwell C and the cylindrical locking shaft 12 was formed of a steel having a hardness of about 30 Rockwell C. The locking leaves were inclined 25 to the remainder of the base 10, the diameter of a circle around the periphery of the leaves being 0.25 inch and the diameter of the fastener aperture 14 being 0.045 inch. The cylindrical locking shaft 12 had a diameter of 0.046 inch. The unlocking tongue 19 of the tool 17 was formed with a hollow cylinder 24 having an internal diameter of 0.065 inch, and an external diameter of 0.1 1 inch and the axial slot 25 therein was 0.06 inch. With these dimensions the locking shaft 12 was effectively locked by the locking leaves 15 preventing manual removal thereof while not overly scoring the locking shaft or deforming the locking leaves 15. The tool 17 easily released the locking shaft 12 from the locking leaves 15 with a total movement of the

jaws

19 and 20 of 0.1 inch.

Referring now to FIG. 6, there is illustrated a second embodiment of the fastener. In this embodiment the sheet metal base 10, the protective cap 29 and the marker element 33 are constructed the same as in the embodiment of FIGS. 2 through 5 and like numerals are used to designate the like parts. However, in this embodiment the cylindrical locking shaft 12 is defined by the end of a flexible metal wire 49 linking the locking shaft 12 directly to the marker 33. The cross bar attachment described above for attaching the flexible link 42 to the marker 33 is also used to attach the linking wire 49 to the marker element 33. The flexible link 42 and tack 32 of the FIGS. 2 through 5 embodiment thus is interchangeable with the linking wire 49 of the FIG. 6 embodiment. The linking wire 49 is preferably of a very tough metal such as piano wire to deter cutting thereof. In fact, within the scope of the present invention the locking shaft 12 may be of a tougher material than the sheet metal base 10 if it is formed for unidirectional engagement by the locking leaves 15, for example by being formed with axially spaced circumferential ribs. In use, the linking wire 49 may be looped around some part of an item such as the handle of a ladies handbag, inserted through the marker aperture 40 and into the fastener aperture 14 to firmly attach the marker element 33 to the item. Removal of the marker 33 is accomplished in the same manner as described with respect to the FIGS. 2 through 5 embodiment.

Referring now to FIG. 7 there is illustrated a third embodiment of the fastener. In this embodiment the sheet metal base 10 is the same as described with respect to the previous embodiments and the locking shaft 12 includes a head 31 to define a tack 32 as described with respect to the embodiment of FIGS. 2 through 5. However, in this embodiment the axial stand-off for the sheet metal base 10 is formed by extending the peripheral edgewall of the protective cap 52 beyond the plane of the sheet metal base 10 a distance slightly greater than the height of the locking tongue 19 of the tool 17 at the hollow cylinder 24 thereof. A peripheral slot 54 is formed in the edgewall of the protective cap 52 from the plane of the sheet metal base 10 to the edge of the protective cap 52 and having a width slightly greater than the width of the unlocking tongue 19 of the tool 17 to provide access to the locking shaft 12 for release of the fastener. With this fastener a flat surfaced identification tag 56 may be securely attached to an article 58 to be identified and it may be easily removed by the tool 17 in the same manner as described with respect to the embodiment of FIGS. 2 through 5.

I claim:

1. A threadless fastener system comprising:

a leaf spring fastener having a sheet metal base formed with a circular aperture from which a plurality of similar locking leaves radiate, said leaves being inclined to permit insertion of a locking shaft into said aperture perpendicular to said base and movement thereof in only one direction relative to said base,

a cylindrical locking shaft,

an unlocking tongue formed with a longitudinal slot at one end to fit around said locking shaft and a hollow cylinder extending perpendicular to said longitudinal slot and having an axial slot extending its length and aligned with said longitudinal slot to receive said locking shaft coaxially with said hollow cylinder, said cylinder having an external radius less than the distance said locking leaves radiate from said aperture in said sheet metal base, and

means for applying a force to move said unlocking tongue with respectto said sheet metal base in a direction axially of said hollow cylinder to engage and radially deflect said locking leaves to disengage the same from said locking shaft.

2. The threadless fastener system of claim 1 wherein said means for applying a force comprises a pair of pincers in which said unlocking tongue comprises one jaw and the second jaw comprises means for engaging said fastener to apply a force around the periphery of said leaves in opposition to said unlocking tongue.

3. The threadless fastener system of claim 2 wherein said fastener includes a protective cap secured to the periphery of said sheet metal base and extending over the face of said sheet metal base from which said locking leaves are inclined.

4. The threadless fastener system of claim 3 wherein said second jaw comprises a flat tongue.

5. The threadless fastener system of claim 1 including means defining an axial stand-off around the periphery of said leaves, said stand-off extending from the plane of said sheet metal base away from the face of said base oppositethe face thereof from which said leaves are inclined a distance greater than the height of said unlocking tongue along the axis of said cylinder thereof, said stand-off being formed with at least one peripheral slot for access by said unlocking tongue and movement thereof to unlock s'aid fastener.

6. The threadless fastener system of claim 5 wherein said means defining an axial stand-off comprises the peripheral edgewall of a protective cap secured to the periphery of said sheet metal base and extending over the face of said sheet metal base from which said locking leaves are inclined.

7. The threadless fastener system of claim wherein said means defining an axial stand-off is formed on an identification tag that is desired to be attached to an article by said fastener, said identification tag being formed with a locking shaft aperture coaxial with said axial stand-off to receive said locking shaft.

8. The threadless fastener system of claim 7 wherein said identification tag is formed with means for releasably retaining said fastener coaxially with said locking shaft aperture.

9. The threadless fastener system of claim 8 including flexible linking means for linking said locking shaft to said identification tag while permitting insertion of said locking shaft through said locking shaft aperture and into engagement with said locking leaves of said fastener whereby a one piece identification tag and fastener is provided.

10. The threadless fastener system of claim 9 wherein said locking shaft comprises the free end of said flexible linking means.

11. The threadless fastener system of claim 1 wherein said locking shaft is formed of a material having a hardness less than that of said sheet metal base.

12. A tool for unlocking a threadless leaf spring fastener having a sheet metal base to permit removal of the locking shaft therefrom, comprising:

an unlocking tongue formed with a longitudinal slot at one end to fit around the locking shaft and a hollow cylinder extending perpendicular to said longitudinal slot and having an axial slot aligned with said longitudinal slot to receive the locking shaft coaxially with said hollow cylinder, said cylinder having an external radius less than the distance the leaves of the fastener radiate from the locking aperture in the sheet metal base thereof, and

means for applying a force to move said unlocking tongue with respect to the sheet metal base of the fastener in a direction axially of said hollow cylinder to engage and radially deflect the locking leaves to disengage the same from the locking shaft.

13. The tool of claim 12 wherein said means for applying a force comprises a pair of pincers in which said unlocking tongue comprises one jaw and the second jaw comprises means for engaging said fastener to apply a force around the periphery of said leaves in opposition to said unlocking tongue.

14. The tool of claim 13 wherein said second jaw comprises a flat tongue for use with a threadless fastener including a protective cap secured to the periphery of the sheet metal base and extending over the face of the sheet metal base from which the locking leaves are inclined.

Claims

1. A threadless fastener system comprising: a leaf spring fastener having a sheet metal base formed with a circular aperture from which a plurality of similar locking leaves radiate, said leaves being inclined to permit insertion of a locking shaft into said aperture perpendicular to said base and movement thereof in only one direction relative to said base, a cylindrical locking shaft, an unlocking tongue formed with a longitudinal slot at one end to fit around said locking shaft and a hollow cylinder extending perpendicular to said longitudinal slot and having an axial slot extending its length and aligned with said longitudinal slot to receive said locking shaft coaxially with said hollow cylinder, said cylinder having an external radius less than the distance said locking leaves radiate from said aperture in said sheet metal base, and means for applying a force to move said unlocking tongue with respect to said sheet metal base in a direction axially of said hollow cylinder to engage and radially deflect said locking leaves to disengage the same from said locking shaft.

5. The threadless fastener system of claim 1 including means defining an axial stand-off around the periphery of said leaves, said stand-off extending from the plane of said sheet metal base away from the face of said base opposite the face thereof from which said leaves are inclined a distance greater than the height of said unlocking tongue along the axis of said cylinder thereof, said stand-off being formed with at least one peripheral slot for access by said unlocking tongue and movement thereof to unlock said fastener.

7. The threadless fastener system of claim 5 wherein said means defining an axial stand-off is formed on an identification tag that is desired to be attached to an article by said fastener, said identification tag being formed with a locking shaft aperture coaxial with said axial stand-off to receive said locking shaft.

12. A tool for unlocking a threadless leaf spring fastener having a sheet metal base to permit removal of the locking shaft therefrom, comprising: an unlocking tongue formed with a longitudinal slot at one end to fit around the locking shaft and a hollow cylinder extending perpendicular to said longitudinal slot and having an axial slot aligned with said longitudinal slot to receive the locking shaft coaxially with said hollow cylinder, said cylinder having an external radius less than the distance the leaves of the fastener radiate from the locking aperture in the sheet metal base thereof, and means for applying a force to move said unlocking tongue with respect to the sheet metal base of the fastener in a direction axially of said hollow cylinder to engage and radially deflect the locking leaves to disengage the same from the locking shaft.