US3353230A

US3353230A - Shoe fastener

Info

Publication number: US3353230A
Application number: US479729A
Authority: US
Inventors: Ralph E Jones; Mahler Hugh; Charles E Weller
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-08-16
Filing date: 1965-08-16
Publication date: 1967-11-21
Anticipated expiration: 1984-11-21

Description

NOV. 21 1967 JONES ET AL SHOE FASTENER 2 Sheets-Sheet 1 Filed Aug. 16, 1965 mww w 5 MJHEA m2 a I /H W HAze/s, Mac/1, RussELL 6: AEE/v Nov. 21:, 1967 R. E. JONES ET SHOE FASTENER 2 Sheets-Sheet 2 Filed Aug. 16, 1965 M/l/EA/TOES United States Patent 3,353,230 SHOE FASTENER Ralph E. Jones, 4150 Bedford Drive, San Diego, Calif.

92116; Hugo Mahler, 10030 Sunset Ave., La Mesa,

Calif. 92041; and Charles E. Weller, 77 Puritan Drive,

Warwick, RI. 02888 Filed Aug. 16, 1965, Ser. No. 479,729 Claims. (Cl. 24-77) ABSTRACT OF THE DISCLOSURE A fastener for use with a shoe upper having two spaced flaps one provided with a transverse strap overlying the second, the fastener securing the strap to the second flap. The strap carries a hook-like tongue insertable into an opening on a base carried by the second flap. The hooklike tongue on the strap forms part of a shell through which the strap extends and which is provided with prongs engaging the strap to fix the position of the shell thereon. A flat cruciform spring carried by the shell biases the strap into engagement with the prongs. Interfitting surfaces on the shell and the base limit relative movement thereof to linear movement in inserting the hook-like tongue on the shell into the opening in the base, and in withdrawing it therefrom.

This invention relates to a fastening device and more particularly to a fastener for shoes, boots, and the like. The shoe fastener disclosed herein is particularly suited for use with a shoe of the type that includes an upper having two spaced flaps one of which is provided with a transverse closure strap of a length to span the space between the flaps and to overlie the other of the flaps. The shoe fastener functions to releasably secure the closure strap to the other flap. Although the fastener is particularly adapted for this type of shoe, it may also be used for boots, in which case it may be necessary to employ a plurality of these fasteners on each boot.

Cross-references to related applications The subject matter described herein is related to an invention by the same co-inventors which is described in application Ser. No. 344,386, filed Feb. 2, 1964, now Patent No. 3,228,079, issued Jan. 11, 1966, and to another invention by two of the same inventors which is described in application Ser. No. 199,077, filed May 31, 1962, now Patent No. 3,206,819, issued Sept. 21, 1965.

Summary and objects of invention An object of this invention is to provide a shoe fastener which is easily and quickly fastened and adjusted, yet difficult to inadvertently unfasten.

Another object of this invention is to provide a shoe fastener which is durable, of simple design, and which can be manufactured at a relatively low cost.

A further object of this invention is to provide a shoe fastener including a shell and a base in which relative movement between the shell and the base is substantially precluded except for an unlatching movement. According to another object of this invention various surfaces on the shell and the base are engageable to substantially preclude such movement. More particularly, the base is seated against the upper surface of one of the shoe flaps and has a substantially flat elevated portion and opposed longitudinal edges. The shell includes two spaced downwardly extending side walls connected by a crosspiece. Interengaging means releasably secures the shell to the base so that the crosspiece overlies the elevated portion of the base. In this closed or latched position the side walls are fitted closely to and engageable with the two longitudinal edges of the elevated portion of the base to prevent rotary or lateral motion of the shell with respect to the base. Latching elements prevent upward and rearward longitudinal movement of the shell relative to the base. Thus, only an unlatching motion in which the shell is moved forwardly and longitudinally of the base is permitted. By making the under side of the crosspiece generally flat, the stability of the connection is further improved.

Another object of this invention is to provide a shoe fastener which permits a very fine adjustment of the force applied thereby to the shoe and the foot of the wearer. More particularly, an object of this invention is to provide novel means for adjustably securing a shoe closure strap to the shell of the shoe fastener. Such means may include at least one projection extending upwardly from the crosspiece of the shell and engaging the closure strap to prevent the closure strap from slipping longitudinally with respect to the shell. Preferably the projections are integral with and stamped from the crosspiece of the shell and penetrate the closure strap to secure the latter tothe shell. Another object is to provide means including a generally flat spring to apply downward pressure to the closure strap to hold it against the projections. The sharp projections may pierce the closure strap at any point along the length thereof and thus fine adjustment of the strap length is provided. For some applications it may be desirable to replace the sharp projections with a plurality of pins having enlarged heads and to provide apertures in the closure strap to receive the pins to releasably secure the closure strap to the shell.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings.

Description of drawings In the drawings:

FIG. 1 is a perspective view of a shoe having a preferred form of the fastener of this invention secured thereto in the fastened or wearing position;

FIG. 2 is an enlarged perspective view of the base;

FIG. 3 is an enlarged perspective view of the shell;

FIG. 4 is an enlarged perspective view of the spring;

FIG. 5 is an enlarged fragmentary sectional view taken along line 55 in FIG. 1;

FIG. 6 is a fragmentary sectional view taken along line 66 in FIG. 5;

FIG. 7 is a fragmentary plan view of the fastener in the closed position;

FIGS. 8 and 9 are perspective views of a base and a shell respectively of a second embodiment of this invention; and

FIGS. 10 and 11 are perspective views of a base and a shell respectively of a third embodiment of this invention.

Detailed description of preferred embodiments of invention Referring to the drawings and in particular to FIG. 1 thereof, reference numeral 15 designates a shoe including an upper 16 having two spaced flaps 17 and 18. The flap 17 has fastened thereto a closure strap 19 of a length to span the space between the flaps 17 and 18 and to overlie the flap 18. A shoe fastener 21 serves to connect the closure strap 19 and the flap 18 to thereby fasten the shoe.

The shoe fastener 21 includes an integral base 22 (FIG. 2) which is secured by a plurality of rivets 23 (FIG. 5) to the flap 18 and an integral shell 24 *(FIG. 3) which is adjustably connected to the strap 19 and may be releasably connected to the base. The base 22 is preferably an integral metal structure having two end portions or

flanges

25 and 26 which are seated against the upper surface of the flap 13 (FIG. Between the

flanges

25 and 26 is an integral channel-shaped portion 27 having a generally flat top wall or elevated portion 28 and a curved front wall 29 depending therefrom toward the flap 18. A generally rectangular aperture or latching element 31 is formed on the front wall 29 and terminates in a seating surface 32. The base 22 also has generally opposed longitudinally extending

edges

33 and 34.

Open ings

35 and 36 are formed in the

flanges

25 and 26, respectively, for receiving the rivets 23.

The shell 24 (FIG. 3) is adjustably secured to the strap 19 and includes a central crosspiece 37 connecting spaced generally opposed depending and diverging

side walls

38 and 39, the side walls being spaced a sufficient distance to straddle the

longitudinal edges

33 and 34 of the base 22. A front crosspiece 41 and a rear crosspiece 42 are spaced longitudinally from the central crosspiece 37 and extend between the

side walls

38 and 39 to define two strap-receiving

slots

43 and 44, respectively, of equal width.

The

crosspieces

41 and 42 are integral with the

side walls

38 and 39 and the lower surfaces thereof are slightly above the upper surface of the crosspiece 37.

The shell 24 also includes a latching element or latching means. Such means includes a hook-shaped tongue 45 depending from the forward edge of the central crosspiece 37 and lying between two curved depending

tabs

46 and 47 which also depend from the central crosspiece.

As shown in FIG. 5, the tongue 4-5 is received by the aperture 31 of the base and the

tabs

46 and 47 snugly embrace and hook on the front wall 29 to hold the fastener 21 in the closed or fastened position.

Projection means extend generally upwardly from the crosspiece 37 for engaging the strap 19 to secure it to the shell. Such projection means includes a plurality of projections 48 integral with and stamped from the crosspiece 37 and having sharp upper ends 49 for penetrating the strap. Any suitable number of the projections 48 may be utilized; however, six projections forming two parallel transverse rows of three each have been found particularly satisfactory.

Means are provided for holding the strap 19 against the projections 48 to allow the latter to secure the strap to the shell 24. Such means includes the

crosspieces

41 and 42 and a spring member 51 (FIG. 4). As shown in FIG. 5, the strap 19 extends through the

slots

43 and 44 and engages the lower surfaces of the

crosspieces

41 and 42 and the upper surface of the crosspiece 37.

The spring member 51 is formed from resilient metal and includes o posed longitudinal arms 52 and opposed transverse arms 53, each of the former having a shoulder or shouldered portion 54 adjacent the end thereof and each of the latter having an end tip or downwardly extending flange 55 formed at the end thereof. As shown in FIGS. 5-7, the shoulders 54 extend under the

crosspieces

41 and 42, respectively, and the flanges 55 embrace the longitudinal edges of the strap 19. A central portion 56 of the spring 51 overlies the crosspiece 37. The strap 19 is inserted through the

slots

43 and 44 and between the spring member 51 and the crosspiece 37. The spring member 51 biases the strap 19 downwardly, thereby firmly holding the strap in the position shown in FIG. 5. Preferably an end portion 57 of the strap 19 extends longitudinally beyond the crosspiece 41 to provide a gripping member for use in opening and closing the fastener 21.

FIGS. 5 and 6 illustrate how the base 22 and the shell 24 cooperate to fasten the shoe 15. By grasping the end portion 57 of the strap 19, the strap and shell may be pulled away from the flap 17 toward the base 22 against the outward force which will be exerted on these flaps by the wearers foot. Such movement of the shell 24 should be continued until the tongue 45 clears the top wall 28 and the diverging

side walls

38 and 39 straddle the

longitudinal edges

33 and 34 of the base. By releasing the shell at this instant, the force exerted on the flaps 17 and 18 by the wearers foot will cause the tongue 45 to enter the aperture 31 to close the fastener.

Closing of the fastener is facilitated by the diverging

side walls

38 and 39 which serve to guide the shell 24 onto the base 22. Preferably each of the

side walls

38 and 39 forms an angle of about 15 with a plane perpendicular to the crosspiece 37 and the junctures between the side walls and the

crosspieces

37, 41, and 42 are along the

longitudinal edges

33 and 34. In this fastened position, various surfaces on the base 22 and the shell 24 cooperate to provide a stable and secure connection. For example, as illustrated in FIGS. 5 and 6, the interior surfaces of the

side walls

33 and 39 engage the

longitudinal edges

33 and 34 of the base 22 to substantially prevent transverse and rotary movement of the shell relative to the base. The tongue 45 and the aperture 31 cooperate to prevent upward movement of the shell relative to the base. Longitudinal movement of the shell 24 toward the flap 17 is prevented by the engagement of the tongue 45 with the seating surface 32. As shown in FIG. 5, the lower surface of the crosspiece 37 is generally flat and engages the upper surface of the elevated portion 28 to lend additional stability to the fastener. Thus, the only movement of the shell 24 relative to the base 22 which can occur is the unfastening or unclosing motion in which the shell 24 is moved longitudinally to the right as viewed in FIG. 5.

The shell 24 may be secured to the closure strap 19 at any one of an infinite number of points along its length. Accordingly, the tension or force exerted by the shoe on the wearers foot may be adjusted to conform precisely with the amount of tension desired. To accomplish this adjustment, the spring 51 is removed from the shell 24 and the strap 19 is separated from the projections 48. The shell 24 may then be moved longitudinally along the strap to the desired position. When the desired position is reached, the strap 19 is pushed downwardly on the projections 43 until the projections pierce the strap to releasably secure the strap to the shell. The spring 51 is then replaced.

FIGS. 8 and 9 illustrate a second embodiment of this invention. FIG. 8 shows a base 58 which is similar to the base 22, corresponding elements being designated by corresponding reference numerals.

The base 58 has a front wall 59 which is substantially flat in contradistinction to the front wall 29 of the base 22 which is arcuate. A latching element or tongue 61 is stamped from the front wall 59 thereby leaving an opening 62 in the central portion of the front wall. The tongue 61 preferably lies below the plane of the top wall 28. In all other respects the base 58 is identical with the base 22.

FIG. 9 illustrates a shell '63 for use with the base 58 which is similar to the shell 24 of FIG. 3, corresponding elements being designated by corresponding reference numerals. The shell 63 includes a flange 64 depending from the forward edge of the crosspiece 37 and having a rectangular aperture or latching element 65 therein. Thus, in the shell 63 the tongue 45 and the

tabs

46 and 47 are eliminated. In all other respects, the shell 63 is identical to the shell 24.

The shell 63 cooperates with the closure strap 19 in substantially the same manner as the shell 24. In latching the fastener of FIGS. 8 and 9, the shell 63 is placed over the base 58 in the same manner as described above in connection with the embodiment of FIGS. 1-7. In the latched position, the tongue 61 protrudes through the aperture 65 and the flange 64 abuts the front wall 59 to securely hold the fastener in the closed position. In all other respects, the shell 63 and the base 58 cooperate in the same manner as the shell 24 and the base 22.

FIGS. and 11 illustrate a third embodiment of this invention. FIG. 10 shows a base 66 similar to the base 22, corresponding elements being designated by corresponding reference numerals. The base 66 includes a channel-shaped portion 67 including a top wall or elevated portion 68 and a front wall 69. The front wall 69 is generally planar and has a centrally positioned relatively large rectangular aperture 71. A recess 72 of less width than the aperture 71 is formed in the top wall 68 and communicates with the aperture 71. The recess 72 terminates in a seating surface 73. In all other respects the base 66 is identical with the base 22.

FIG. 11 illustrates a shell 74 which is similar to the shell 24, corresponding elements being designated by cor responding reference numerals. The shell 74 includes a crosspiece 75 having a recess 76 at the forward end thereof and a depending tongue 77 with opposed laterally extending flanges 78. The transverse dimension of the tongue 77 across the flanges 78 is sufficiently small so that the tongue can pass through the aperture 71 in the base 66 but is sufficiently large to prevent the tongue 77 and the flanges 78 from moving upwardly through the recess 72.

Projections or pins 79 (two being shown) are riveted to the crosspiece 75 and extend upwardly therefrom. Each of the pins 79 has an enlarged spherical head 81 at the upper end thereof. A strap 82 having two transversely spaced longitudinally extending rows of apertures or perforations 83 is provided. The diameter of the apertures 83 is less than the diameter of the spherical heads 81 so that the heads can be forced through the apertures to adjustably secure the strap 82 to the shell 74. The position of the shell 74 relative to the strap 82 is longitudinally adjustable by insertion of the pins 79 into different ones of the longitudinally arranged apertures 83. It should be understood that other numbers and arrangements of the pins 79 may be used if the strap 82 is appropriate ly perforated to accommodate them. The primary advantage of using a plurality of the pins 79 in lieu of a single pin is that a lesser force is exerted on each portion of the strap defining the apertures 83, thereby reducing the likelihood of tearing the strap and allowing closer longitudinal spacing of the apertures 83 to permit a finer adjustment of the effective strap length.

The shell 74 may be releasably secured to the base 66 by causing the flanged tongue 77 to pass through the aperture 71 to allow the tongue to engage the seating surface 73. The flanges 78 extend laterally a sufficient distance so that they prevent the tongue from passing upwardly through the recess 72. In all other respects, the shell 74 and the base 66 cooperate in the same manner as the shell 24 and the base 22.

Many changes, modifications, and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

What is claimed is:

1. A shoe fastener for use with a shoe of the type that includes an upper having two spaced flaps one of which is provided with a transverse closure strap of a length to span the space between said flaps and to overlie the other of said flaps, said shoe fastener being capable of releasably securing said closure strap tosaid other flap and including the combination of:

a base having two end portions adapted to be seated against the upper surface of said other flap, said base having a central elevated portion which is substantially flat, and means for securing said end portions to said other flap;

a shell including two spaced, downwardly extending side walls connected by two spaced end crosspieces and a central crosspiece interposed between said two end crosspieces, said central crosspiece being ad- 6 justably connected to said closure strap and adapted to overlie said base;

a first latching element carried by said shell;

a second latching element carried by said central elevated portion of said base and engageable with said first latching element to releasably secure said shell to said base to close the fastener;

said central elevated portion having two generally opposed edges, said side walls fitting closely to said two edges of said central elevated portion of said base when the fastener is closed, this degree of closeness along said two edges serving to prevent any substantial rotary motion and lateral motion of said shell with respect to said base;

said closure strap being adapted to lie in a position wherein it is below the two end crosspieces of said shell and above said central crosspiece; and

means for adjustably attaching said closure strap to said shell including at least one projection extending upwardly from said central crosspiece of said shell, said projection being adapted to engage said closure strap to prevent said closure strap from slipping longitudinally with respect to said shell.

2. A shoe fastener according to claim 1 wherein said two side walls of said shell diverge as they extend downwardly to form an angle of about 15 with a line perpendicular to saidcentral crosspiece of said shell, thus providing steering elements suitable for steering said shell and said base extremely quickly and easily into the fastened position.

3. A shoe fastener according to claim 1 wherein said first latching element includes a tongue on said shell and said second latching element includes a slot in said base for receiving said tongue.

4. A shoe fastener according to claim 1 wherein said first latching element includes a slot in said shell and said second latching element includes a tongue projecting from said base and adapted for entry into said slot.

5. A shoe fastener according to claim 1 wherein said means for attaching said closure strap to said shell includes a plurality of upwardly extending projections integral with and stamped from said central crosspiece of said shell, said projections penetrating said closure strap, and wherein said shoe fastener has a generally flat spring having two opposed longitudinal arms with shoulder portions adjacent the ends thereof which extend respectively slightly under the two end crosspieces of said shell to apply downward pressure to said closure strap to retain said closure strap against said projections,

said generally fiat spring also having two opposed transverse arms, each of said transverse arms having an end tip extending downwardly adjacent a longitudinal edge of said closure strap, said shoulder portions and end tips serving to prevent said generally flat spring from becoming inadvertently disengaged from said shell.

6. A shoe fastener according to claim 1 wherein said means for attaching said closure strap to said shell includes a pin having an enlarged curved head at the upper end thereof and at least one aperture in said closure strap, said head being of larger diameter than said aperture, said pin and said head being receivable by said aperture to releasably secure said closure strap to said shell.

7. A shoe fastener according to claim 6 wherein said means for attaching said closure strap to said shell includes a plurality of said pins on said central crosspiece of said shell and a row of said apertures in said closure strap for receiving said pins.

8. A shoe fastener for use with a shoe of the type that includes an upper having two spaced flaps one of which is provided with a transverse closure strap of a length to span the space between said flaps and to overlie the other of said flaps, said shoe fastener being capable of releasably securing said closure strap to said other flap and including the combination of:

a base seated against the upper surface of said other flap and having a pair of longitudinal edges;

connecting said side walls, and projection means extending generally upwardly from said crosspiece for engaging the strap to secure it to said shell;

interengaging means on said crosspiece and said base, and responsive to relative longitudinal movement of said crosspiece and said base, in a direction parallel to said longitudinal edges of said base, for releasably connecting said shell to said base, said side walls straddling said base and being engageable with said longitudinal edges, during said relative longitudinal movement of said crosspiece and said base, to prevent transverse and rotary movement of said shell relative to said base when said shell is connected thereto; and

means for holding said strap against said projection means to allow said projection means to secure said strap to said shell.

9. A shoe fastener for use with a shoe of the type that includes an upper having two spaced flaps one of which is provided with a transverse closure strap of a length to span the space between said flaps and to overlie the other of said flaps, said shoe fastener being capable of releasably securing said closure strap to said other flap and including the combination of:

a base seated against the upper surface of said other a shell including a crosspiece and at least one projection on said crosspiece having a sharp upper end for penetrating the strap to secure the strap to said shell;

interengaging means on said crosspiece and said base for releasably connecting said shell to said base; and

a generally flat spring member having ends inserted under portions of said shell spaced from and located on opposite sides of said crosspiece, and having a portion thereof overlying said crosspiece, the strap being insertable between said spring member and said crosspiece and being firmly held in engagement with said projection by said spring member.

10. A shoe fastener for use with a shoe of the type that includes an upper having two spaced flaps one of which is provided with a transverse closure strap of a 3 length to span the space between said flaps and to overlie the other of said flaps, said shoe fastener being capable of releasably securing said closure strap to said other flap and including the combination of:

a base seated against the upper surface of said other flap and including a generally flat surface spaced upwardly from said other flap and a pair of longitudinal edges;

a shell including a crosspiece connecting spaced generally opposed depending side walls, said side walls being spaced a sufficient distance to straddle said longitudinal edges of said base;

a first latching element carried by said shell; a second latching element carried by said elevated portion of said base and engageable with said first latching element, in response to relative longitudinal movement of said latching elements in a direction parallel to said longitudinal edges of said base, to releasably secure said shell to said base to close the fastener;

said side walls straddling and engaging said longitudinal edges of said base to substantially prevent transverse and rotary movement of said shell relative to said base during said relative longitudinal movement of said latching elements and when said fastener is closed;

said crosspiece having a generally fiat lower surface which overlies said generally fiat surface of the base when the fastener is closed; and

means on said base and said shell for preventing upward movement of said shell relative to said base when the fastener is closed.

References Cited UNITED STATES PATENTS 831,090 9/1906 New 24180 1,255,240 2/ 1918 Stamm 24201 1,696,586 12/1928 Simons 2477 FOREIGN PATENTS 10,541 2/1908 Denmark. 1,193,277 4/1959 France.

45 OTHELL M. SIMPSON, Primary Examiner.

E. SIMONSEN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,353,230- November 21, 1967 Ralph E. Jones et a1.

error appears in the above numbered pat- It is hereby certified that t the said Letters Patent should read as ent requiring correction and tha corrected below.

Column. 1,.bef0re 'line 29, insert. as a heading Backgroun of Invention. w-; line 44; for "Feb. *2, 1964" read Feb. 12, 1964 column 3, line '10', for "on" read in column 7, line 3, for "walls; 'read walls,

Signed and sealed 'this 31st day of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

Claims

1. A SHOE FASTENER FOR USE WITH A SHOE OF THE TYPE THAT INCLUDES AN UPPER HAVING TWO SPACED FLAPS ONE OF WHICH IS PROVIDED WITH A TRANSVERSE CLOSURE STRAP OF A LENGTH TO SPAN THE SPACE BETWEEN SAID FLAPS AND TO OVERLIE THE OTHER OF SAID FLAPS, SAID SHOE FASTENER BEING CAPABLE OF RELEASABLY SECURING SAID CLOSURE STRAP TO SAID OTHER FLAP AND INCLUDING THE COMBINATION OF: A BASE HAVING TWO END PORTIONS ADAPTED TO BE SEATED AGAINST THE UPPER SURFACE OF SAID OTHER FLAP, SAID BASE HAVING A CENTRAL ELEVATED PORTION WHICH IS SUBSTANTIALLY FLAT, AND MEANS FOR SECURING SAID END PORTIONS TO SAID OTHER FLAP; A SHELL INCLUDING TWO SPACED, DOWNWARDLY EXTENDING SIDE WALLS CONNECTED BY TWO SPACED END CROSSPIECES AND A CENTRAL CROSSPIECE INTERPOSED BETWEEN SAID TWO END CROSSPIECES, SAID CENTRAL CROSSPIECE BEING ADJUSTABLY CONNECTED TO SAID CLOSURE STRAP AND ADAPTED TO OVERLIE SAID BASE; A FIRST LATCHING ELEMENT CARRIED BY SAID SHELL; A SECOND LATCHING ELEMENT CARRIED BY SAID CENTRAL ELEVATED PORTION OF SAID BASE AND ENGAGEABLE WITH SAID VATED PORTION OF SAID BASE ANE ENGAGEABLE WITH SAID FIRST LATCHING ELEMENT TO RELEASABLY SECURED SAID SHELL TO SAID BASE TO CLOSE THE FASTENER; POSED EDGES, SAID SIDE WALLS FITTING CLOSELY TO SAID TWO EDGES OF SAID CENTRAL ELEVATED PORTION OF SAID BASE WHEN THE FASTENER IS CLOSED, THIS DEGREE OF CLOSENESS ALONG SAID TWO EDGES SERVING TO PREVENT ANY SUBSTANTIAL ROTARY MOTION AND LATERAL MOTION OF SAID SHELL WITH RESPECT TO SAID BASE; SAID CLOSURE STRAP BEING ADAPTED TO LIE IN A POSITION WHEREIN IT IS BELOW THE TWO END CROSSPIECES OF SAID SHELL AND ABOVE SAID CENTRAL CROSSPIECE; OF SAID MEANS FOR ADJUSTABLY ATTACHING SAID CLOSURE STRAP TO SAID SHELL INCLUDING AT LEAST ONE PROJECTION EXTENDING UPWARDLY FROM SAID CENTRAL CROSSPIECE OF SAID SHELL, SAID PROJECTION BEING ADAPTED TO ENGAGE SAID CLOSURE STRAP TO PREVENT SAID CLOSURE STRAP FROM SLIPPING LONGITUDINALLY WITH RESPECT TO SAID SHELL.