CA1248793A - Fastening element - Google Patents

Abstract

ABSTRACT

An improved fastening element for securement within an opening and of the type comprising (a) a head portion; (b) a connecting portion comprising a body dis-posed centrally upon and upstanding from the head portion and a pair of opposed pillar-like parts, for insertion into such opening; and (c) at the end of said connecting portion remote from the head portion, locking parts movable between a collapsed position in which the fastening ele-ment is insertable into the opening and an expanded posi-tion in which the locking parts are effective in coopera-tion with an elongated retaining element inserted into the fastening element to preclude removal of the fastening element from the opening. The improvement of the inven-tion resides in the locking parts which comprise:
(i) a pair of substantially rigid arms each pivotally connected to a respective one of said pillar-like parts at radial locations substantially adjacent to or within the radius of the body portion in the expanded position and each having a distal and a proximal end portion, wherein said proximal end portions are cantilevered and adapted for en-gagement with an elongated retaining element and disposed to pivot with respect to each other in a plane which includes the longitudinal axis of said body, whereby the arms are movable toward each other to a collapsed position and away from each other to an expanded position; and (ii) a pair of substantially rigid arms with each having a proximal and a distal end, and with each being pivotally connected to a respective one of arms (i) and pivotally connected to each other on the longitudinal axis of the body portion for engagement with the elongated retaining element, whereby such arms (ii) are movable toward each other to a collapsed position and away from each other to an expanded position. Each arm is substantially longer than the maximum transverse dimension of the body. The arms (i) and (ii) are conjointly movable in symmetric pantographic con-figuration between the collapsed and expanded posi-tions in a plane which includes the longitudinal axis of the body.

Description

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FASTEI`~ G ELEt~lEl~T

DESCRIPTION

T-echnical ~ield .

This invention relates to ~astening elements and, more particularly~ to integrally molde~ plastic fastening elem~nts of ennanced 102d bearing capabili.y and ezse of labrication.
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Back~round Art Inteyrally molded plastic fastening eleme~s of the type disclosed in tJ.S. Pat. No. ~,65l,734, issued to the present inventor on ~larch 28, 1972r are rapidly gaining commercial acceptance, both here and abroad.
These fastening elements co.,prise, in subctOnce? a head ~` for disposition at one end o~ an opening, expansible lockinq means for location a. the other end of the open-ing, and flexible, spaced apart connectors ex~tending therebetween.

~ ore specifically, the above prio~ art fastenin~
elements typically utilize relatively long ~onnectors which extend radially outward far beyond the edges of the opening when the fastening element is in its expanded, .

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locking position. The locking means typically comprises a pair of toggle members pivotally connected together at their adjacent ends so that they are moveable between a collapsed position in which they can be inserted through an opening and an expanded position in which they secure the fastener within the opening. The connectors are joined to the toggle members at locations on the toggle members such that when the toggle embers are moved into the expanded position, the connectors are forced apart relatively far from their conformation in the collapsed condition so that they e~tend radially outward far beyond the edges of the opening. In this structure, much of the load on the fastening element is borne by the relatively long, relatively flexible connector elements.

While the aforesaid fastening elements have proven to be highly satisfactory in a wide variety of applications, the present invention is directed to devices having features particularly use~ul in applications requiring high load-bearing capability.

Disclosure of the Invention In applicant's Canadian Patent No. l,091,96~, issued December 23, 1980, there is shown an integrally molded plastic fastening element which comprises a head portion, a body portion extending longitudinally from the head portion and having a pair of longitudinally extending pillar-like parts, and a pair of substantially rigid locking arms pivotally connected or pivotally disposed with respect to each other at their adjacent ends.
~he rigid locking arms are each pivotally connected to the body portion at the ends of the respective pillar-like parts at locations radially adjacent the cross-section of the body so that the rigid arms bear the bulk of the load applied to the fastener. The advantages of this structure include enhanced load bearing capability and ease of fabrication. In a preferred embodiment, the body is provided with a central passageway and the pillar-like parts are curved radially inwardly in order to ~`

37~3 spring b-ias the walls of the passageway against an elongated retaining member inserted therein and to spring bias the arms in an over-center locking position.
In accordance with the present invention, the fastener generally as described in the aforesaid Canadian Patent No. 1,091,964 comprises a further novel feature wherein the locking means comprises four more or less rigid arms arranged in a specific manner with respect to one another so as to create a symmetric pantographic configuration, i.e., a quadrilaterial or four-sided polygon, in which three of the four angles or vertices are formed by flexible linkages and are each less than 180 when the fastener is installed. The fourth vertex, which is the one closest to the body portion, is formed between two opposed cantilever arms and about which such arms are pivotally disposed and engageable with an elongated retaining element (e.g., a screw), and is at least equal to or preferably slightly greater than 180 when the fastener is installed. The pair of arms forming the flexible linkage at the opposite apex are also engageable with such retaining element. The term "retaining element" or "elongated retaining element" is used in the specification to refer to any fastening device which has means for attachment to the load and an elongated engagement means suitable for insertion into and reten-tion by the fastening elements of the present invention.
The fastening elements described herein can be fabricated of any convenient material. Desirably, the present fasteners can be formed of moldable, corrosion-resilient thermoplastic material, such as polyethylene, nylon, polyolefin, and the like. A preferred material is polypropylene, particularly high density or isotactic polypropylene, in view of its attractive mechanical properties including the ability to form so-called "living hinges", and its ability to be readily injection moded. Techniques for forming the fastening elements described herein will become apparent to those skilled in the art having the benefit of the present disclosure before them.

~ 4 _ ~2~ 3 Brief Description of the Drawings The nature, advantages~ and various additional features of the invention will appear m~re *ully ~pon consideration o* the illustrati~e embodiments described S below in connection with the accompanying drawings, whexein.
YIG. 1 is a schematic cross-sec~ion of a typical prior ~rt molded plastic fastening element in the open or as-molded (solid line) and closed or collapsed (dotted line) position;
FIG. 2 is a side elevation of the fastening element of this invention in the open or as-molded (solid line~
and partially closed or collapsed (dotted line~ position;
FIGo 3 is a top plan view of the fastener ~f FIG. 2;
FIG. 4 is a bottom plan Yiew of the fastener of FIG. 2;
FIG. 5 is a 5ide elevation of a further novel and in~entive fastening element in the open or as-molded (solid line) and partially c~osed or collapsed (do~ted line) position; and .
FIG. 6 is a bottom plan view of the astener of FIG . ~ O

For convenience of refex~nce, the same structural elements are designated by tne same rPferenc~ numeral~ thxouyh;
out the drawings~

B~st Mode For Carrying Out The Invention Prior Art -(FIG. ~1) Ref~rring to FIG. 1, the pri9x art molded plastic fastening element shown therei~ compri5es, i~ substance, a head 1 for disposition at one end of an opening 20 an expansible locking means in ~he form of toggle arm~ 3a and 3b for location at the other end of the opening, and flexible spaced apart connectors 4a and 4b extending therebetween.

37~

Toggle arms 3a and 3b are pivotally connected together at their adjacent ends so as to be movable between a collapsed position 5 in which they can be inserted through opening 2, and the expanded position in which they secure the fastener within the opening.

The connectors _ and 4b are typically joined to the toggle arms 3a and 3b substantially inflexibly and at remote locations 6a and 6b such that when the toggle arms move into expanded position, the connectors are forced apart and outward relatively far from their radial lccations or situs in the collapsed condition so that the connectors extend far beyond the edges of the opening.

While fastening elements of this type have proved highly satisfactory in a great variety of applications r the present invention provides improved load bearing capability and ease of fabrication. With respect to load bearing capability, it can be seen by reference to FIG. 1 that the major portion of the load on the fastening element is borne by the long, flexible connectors 4a and 4b. Moreover, the toggle arms 3a and 3b are relatively thin throughout the major portion of their length because they, in the collapsed state, must share the limit available space in opening 2 with the long connectors 4a and 4b. These features necessarily limit the load bearing capability of such prior fastening element, especially when they are made of resilient plastic - material.

With respect to ease of fabrication, it can be readily appreciated that remote joining locations 6a and 6b require thin knife edge components in the mold in order to define and create spaces 7a and 7b. Molding around such thin, knife edge components presents one of the more difficult aspects of fabrica-ting these devices; and, because heat concentrating at the points of the knife-edges tends to weaken the material being molded, particularly in the case of plastic, the molding step introduces points of potential weakness in the product.

FIGS. 2 to 4 The fastener 200 of FIGS. 2 through 4, like those of the aforesaid Canadian Patent No. 1,091,9~4, comprises a head portion 10 of generally flanged disc-like form, and a shank or body portion 12 disposed centrally upon and upstanding 5 from the head portion. However, fastener 200 represents a departure from the fasteners of the aforesaid patent in that it comprises a novel and unusual locking means having a configuration which differs from the locking means of the fasteners of the aforesaid patent, while possessing certain 1~ advantages as described hereinbelow:

The body portion 12, as can be seen in ~IGS. 2, 3 and 4, is of a generally quadrilateral, e.g., square, cross-section, and whose upper end segues into a pair of opposed pillar-like portions 14 described more fully hereinafter.
Spaced about the body 12 are fins 16, in this particular embodiment there being four such fins. Extending through head 10 and through body 12 is a central bore or passage 18.

37~

The novel locXing means of this ~urLher inven-tive embodiment comprises a-~irst pair of generally similar rigid arms 201 each substantially greater in length than the lateral or transverse dimensions of body 5 portion 12. The adjacent inner ends of the arms 201 terminate in cantilevers 211 whose ends are separated by a gap 202 about which the arms are pivotally movable relative to each other in a vertical plane which includes the longitudinal axis of body portion 12. Alternatively, in lieu of gap 2~2, t~e cantilevered adjacent inner ends

2 of arms 201 can be joined by a flexible integral strap of sufficient elasticity to permit the aforesaid pivotal movement of arms 201. Such a strap, if used, should have an opening coaxial with passage 18 to permit the passage therethrough of a suitable ret~ining element such as a screw (not shown).

The rigid arms 201 are each joined to the pillar-like portions 14 or body 12 in the general regions of points A and B, sala plllar-like portions 14 being somewhat flexible to accommodate the movement of arms 201 about pivot points A and B.

As can be seen in FIG. 2, the upper end of body 12, i.e., that end of the body closest to rigid arms 201 r terminates in a cavity 38 which can accommodate the ad~acent or proximal cantilevered ends 211 of said arms as the locking means are folded (dotted line) in the direction of the collapsed conformation.

The loc~ing means further comprises a second pair of generally eaual-lenqth rigid a~ms 203 whose proximal ends are pivotally interconnected by means, e.g., of a relatively thin, flexible, integral strap 204 and whose distal ends are pivotally connected to the upper .

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, surfaces of arms 201, also by means, e.g., of relatively thin, flexible, integral straps 205. The interconnection of arms 203 at 204 is such that the center thereof coin-cides with the longitudinal axis of body portion 12, and the interconnections of arm~ 203 with arms 201 at 205 are essentially equidistant from said longitudinal axis. In this way, arms 203 are movable in concert with arms 201 in the manner of a symmetrical pantograph in a vertical plane which includes the longitudinal axis of body 12. The flexible strap 204 is advantageously provided with a through opening 206 which can best be seen in FIG. 3 .

In operation, when the fastener 200 is to be inserted into a hole or aperture in a structure such as a panel or hollow wall, arms 201 are folded around points A
and B with _ as the pivot, so that the upper surfaces of these arms, i.e., those surfaces rernote from base 10, are brought into face-to-face relationship, while at the same ~
time the lower surfaces of arms 203, i.e., those surfaces closest to base 10, are likewise brought into face-to-face relationship by the pivotal movement of these arms about ~04, as shown by the arrows in FIG. 2 , both pairs of arms being thereby disposed generally parallel to the longi-tudinal axis of body portion 12. In such closed confor-mation, arms 203 are accommodated or nested within re-cesses 207 provided in the upper surfaces o~ arms 201, thereby permitting all four arms to share the limited space available in the opening tllrough which the fastener is inserted~
During insertion of fastener 200 through a hole, as the folded or collapsed arms 201 (with folded arms 203 nested therein) clear the opposite end of the hole (until the flange of head 10 abuts the outer surface of the panel or the fixture to be secured tllereto), the _~.' , ' ~ . .

37~3 arms will unfold somewhat and, in the manner of a panto-graph, tend to move toward t~heir expanded positions, with adjacent arms 201 and 200 forming re~erse acute angles with vertices at 205. A rigid elongated3 preferable corrosion-resistant retaining element or member designed to engagearms 203 at pivot point 204 and the cantilevered end portions 211 of arms 201 at pivot 202, e.g., a threaded screw (not shown), is then inserted into fastener 200 thus installed within the hole. A critical feature of this invention is that when the retaining element is tightened in place, the aforementioned acute reverse angles formed by arms 201 and 203 are reduced to a minimum value, while the obtuse an~le ormed by arms 203 is increased to a more or less maximum value (but less than 180), depend-ing on the relative lengths of arms 201 and 203, as can bereadily envisioned bv reference to FIG. 2 . At the same time, the angle formed by arms 201 with vertex at 202 is increased from an amount less than 180 to a maximum value of at least equal to or slightly greater than 180. In this way, the retainin9 member will, with its leading end portion engaging strap 204 and its shank engaging the proximal cantilevered ends 211 of arms 201, secure the fastener in its open, load-bearing conformation by virtue of the cooperative forces or purchase exerted (in -the upward direction in the drawing) by the retainin~ member upon strap 204 and upon cantilevered ends 211 r which gives rise to and maintains the abutting force of arms 201 against the inner surface of the panel and the opposed abutting force of the flange of head 10 against the outer surface of the panel. When the retaining member is removed, the fastener 200 remains in place for re~use~
Alternatively, the fastener can be removed from the hole by withdrawing the retaining member and then pulling the fastener out of the hole in the opposite direction in which it was inserted.
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In the embodiment shown in FIGS. 2 , 3 and 4 , all of the various structural features of the fasteners described hereinabove can be incorporated therein to the extent consistent with the structure and mode of function of the present further invention, as will be apparent to those skilled in the art having the benefit of the present disclosure before them.

FIGS. 5 and 6 FIGS. 5 and 6 illustrate another fastener embodiment 212 of the novel structural principles de-scribed in connection with the fastener shown in FIGS.
2 through 4 . In the present embodiment, rigid equal length arms 203 are joined at their distal ends to the respective distal ends 210 of rigid equal length arms 201 by means of flexible linkages 205 in the form of rela-tively thin integral straps. The base 10, body portion 12, pillar-like portion 14 and fins 16 are of a con-figuration essentiallv the same as that described inthe aforementioned Canadian Patent NoO l,09l,964.

In the operation of fastener 212, as the locking means are folded (dotted line) in the direction of their closed position prepa.ratory to insertion throug~
a hole or aperture in a st~ucture such as a panel or hollow wall, arms 201 and 203 rotate pivotally to achieve the movement of a symmetrical pantograph in the ~anner . indicated by the arrows in FIG. 5 until both pairs of arms are aligned in sequential fashion parallel to the longitudinal axis of body portion 12~ In such conforma-tion, the cantilevered proximal ends 211 of arms 201 are accommodated within space 38 formed at the upper end of body 12.

During insertion of fastener 212 through a hole, as the folded or collapsed pairs of arms 201 and 203 clear the opposite end o~ the hole (until the flange of head 10 abuts the outer surface of the panel or the 5 fixture to be secured thereto), the arms will unfold somewhat and, in the manner of a pantograph, tend to move toward their expanded positions, with adjacent arms 201 and 203 forming reverse acute angles with vertices at 205. An elongated retaining element or member, e.g~, a 10 threaded screw, such as a sheet metal screw (preferably made of stainless steel or suitably coated on plated metal for corrosion res-s~a..~e), is then inserted into fastener 200 thus installed within the hole. As in the case of the fastener of FIGS. 2 - 4 / a critical feature of the inven 15 tion here is that when the retaining member is tightened in place, the aforementioned reverse acute angles formed by arms 201 and 203 are reduced.to a minimum value, while the obtuse angle formed by arms 203 is increased to a more or less maximum value (but less than 180), depend-20 ing on the relative lengths of arms 201 and 203, as can bereadily envisioned by reference to FIG. ~ . At the same time, the angle formed by arms 201 with vertex at 202 is increased from an amount less than 180~ to a maximum value of at least equal to or slightly greater than 180 . In 25 this way, the retaining member will, with its.leading end portion engaging strap 204 and its shank engaging the proximal cantilevered ends 211 of arms 201, secure the fastener in its open, load-bearing conformation by virtue of the cooperative forces or purchase exerted (in the 30 upward direction in the drawing,) by the retaining member upon strap 204 and upon cantilevered ends 211, which gives rise to and maintains the a~utting force of arms 201 against -the inner surface of the panel and opposed abutting form of the flange of head 10 against the vuter surface of the 35 panel. ~hen the retaining mem~er is removed, the fastener ~; = '"' .. ' ' 212 remains in place for re-use. Alternatively, the fastening element can be removed from the hole by with-drawing the retaining member and then pulling the fastener out of the hole in the opposite direction in which it was nserted .

In the embodiment shown in FIGS. 5 and 6 , all of the various structural features of the fasteners described hereinabove can be incorporated therein to the extend consistent with the structure and mode of function of the present further invention, as will be apparent to those skilled in tne art naving tne benefit of the present disclosure before them.
The flexible straps 204 and 205 referred to in connection with FIGS. 2 through 5 , when the fastener is molded from therrnoplastic, particularly polypropylene, form so-called "living hinges". These are formed by reducing the molded thickness of the respective arms 2 and 203 at the ends where they are joined. The thicknesses of the hinges are a matter of design choice, a thinner hinge being more 1exible but less durable (in terms of number of flexings before failure~
; and vice versa.

While the invention has been described in connection with a number of ~pecific embodiments, it is to be understood that these are merely illustrative of the many ways in which the principle of the in~ention described in connection with FIGS. 2 through 6 can be utilized. ~or example, while the body portion of the ~= fastener has been described as being either basically parallelepiped or cylindrical in shape, this is merely a matter of convenience and such body can take any of several forms depending upon the particular opening or . _ -7~3 aperture through which the body is to be passed and uponmolding considerations. It will also be appreciated that while the embodiments illustrated hereinabove are specifi-cally designed to provide anchors for screws, they can be readily adaoted fcr v2-icuc o~her uses ranging from simple cuff link-type structures to hook devices, depending upon the result required. Thus, numerous and varied devices can be made by those skilled in the art without departing from the scope of the invention which is defined in the following claims.

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Claims (17)

I CLAIM:

1. A fastening element for securement to a wall panel on opposite sides of an opening therein comprising (a) a head portion; (b) a connecting portion comprising a body extending longitudinally from the head portion and a pair of opposed pillar-like parts, for insertion into such opening; and (c) at the end of said connecting portion remote from the head portion, locking means for engagement with the inner surface of said panel, said locking means being movable between a collapsed position in which the fastening element is insertable into and partially through the opening and an expanded position in which the locking means is effective, in cooperation with an elongated retaining element inserted into the connecting portion, to preclude removal of the fastening element from the opening, wherein said locking means comprises:
(i) a pair of first substantially rigid arms pivotally connected to the pillar-like parts at radial locations substantially adjacent to or within the radius of the body in the expanded position and disposed to pivot with respect to each other in a plane which includes the longitudinal axis of said body, whereby the arms are movable toward each other to a collapsed position for insertion thereof through said opening, and away from each other to an expanded position, for supporting engagement thereof with said inner surface, each arm being of substantially greater length than the maximum transverse dimension of the body portion; and (ii) a pair of second substantially rigid arms, each pivotally connected to one of first arms, and pivotally connected to each other on the longitudinal axis of the body for engagement with said elongated retaining element whereby such second arms are movable toward each other to a collapsed position and away from each other to an expanded position, so as to be engageable with said elongated retaining element, the improvement comprising said first and second arms being conjointly movable in symmetric pantographic configuration between said collapsed and expanded positions in a plane which includes the longitudinal axis of the body and wherein said first arms have proximal end portions which are cantilevered inner extensions of said first arms and are arranged for engagement with said elongated retaining element in said expanded position, with said first arms forming an angle between them of 180° after moving through said pantographic configuration into said expanded position, and wherein said second arms are engaged with said elongated retaining element, in said expanded position, with said second arms forming an obtuse angle between them.

2. A fastening element for securement to a wall panel on opposite sides of an opening therein comprising (a) a head portion; (b) a connecting portion comprising a body extending longitudinally from the head portion and a pair of opposed pillar-like parts, for insertion into such opening; and (c) at the end of said connecting portion remote from the head portion, locking means for engagement with an inner surface of said panel said locking means being movable between a collapsed position in which the fastening element is insertable into and partially through the opening and an expanded position in which the locking means is effective, in cooperation with an elongated retaining element inserted into the connecting portion, to preclude removal of the fastening element from the opening, characterized in that said locking means comprises:

(i) a pair of first substantially rigid arms pivotally connected to the pillar-like parts at radial locations substantially adjacent to or within the radius of the body in the expanded position and wherein said fastening element is adapted to be engaged with said elongated retaining element at a position between proximal end portions of said arms, said arms being disposed to pivot with respect to each other in a plane which includes the longitudinal axis of said body, whereby the arms are movable toward each other to a collapsed position, for insertion thereof through said opening, and away from each other to an expanded position, for supporting engagement thereof with said inner surface while forming an angle between them at least 180°, each arm being of substantially greater length than the maximum transverse dimension of the body portion, and (ii) a pair of second substantially rigid arms, each pivotally connected to one of the first arms and pivotally connected to each other on the longitudinal axis of the body for engagement with said elongated retaining element, whereby such arms are movable toward each other to a collapsed position and away from each other to an expanded position, so as to be engageable with said elongated retaining element, and said first and second arms being conjointly movable in symmetric pantographic configuration between said collapsed and expanded positions in a plane which includes the longitudinal axis of the body and wherein each of the second arms is pivotally connected at its distal end to one of the first arms at locations intermediate the ends of said first arms and equidistant from the longitudinal axis of the body.

3. A fastening element for securement to a wall panel on opposite sides of an opening in a panel comprising (a) a head portion; (b) a connecting portion comprising a body extending longitudinally from the head portion and a pair of opposed pillar-like parts, for insertion into such opening; and (c) at the end of said connecting portion remote from the head portion, locking means for engagement with an inner surface of said panel, said locking means being movable between a collapsed position in which the fastening element is insertable through the opening and an expanded position in which the locking means is effective, in cooperation with an elongated retaining element inserted into the connecting portion, to preclude removal of the fastening element from the opening, characterized in that said locking means comprises:
(i) a pair of first substantially rigid arms pivotally connected to the pillar-like parts at radial locations substantially adjacent to or within the radius of the body in the expanded position and wherein said fastening element is adapted to be engaged with said elongated retaining element at a position between proximal end portions of said arms, said arms being disposed to pivot with respect to each other in a plane which includes the longitudinal axis of said body, whereby the arms are movable toward each other to a collapsed position, for insertion thereof through said opening, and away from each other to an expanded position, for supporting engagement thereof with said inner surface while forming an angle between them of at least 180°, each arm being of substantially greater length than the maximum transverse dimension of the body portion; and (ii) a pair of second substantially rigid arms, each pivotally connected to one of the first arms and pivotally connected to each other on the longitudinal axis of the body for engagement with the elongated retaining element, whereby such second arms are movable toward each other to a collapsed position and away from each other to an expanded position, so as to be engageable with said elongated retaining element, and said first and second arms being conjointly movable in symmetric pantographic configuration between said collapsed and expanded positions in a plane which includes the longitudinal axis of the body and wherein each of the second arms is pivotally connected at its distal end to one of the first arms at locations intermediate the ends of said first arms and equidistant from the longitudinal axis of the body and wherein each second arm is adapted to become completely recessed within one of the first arms when all said arms are in the collapsed position.

4. The fastening element according to claim 1 wherein each of the second arms is pivotally connected at its distal end to the distal end of one of the first arms, said first being of equal length and said second arms being of equal length.

5. The fastening element according to claim 1, 2, or 3 wherein:
each of the second arms is pivotally connected to one of the first arms, by a flexible integral strap; and the second arms are connected to each other at their proximal ends by a flexible integral strap.

6. The fastening element according to claim 1 wherein a central region of the body adjacent to said locking means is recessed to accommodate the proximal cantilevered inner extensions of the first arms when the locking means are in the collapsed position.

7. The fastening element according to claim 6 wherein the cantilevered inner extensions of the respective first arms are separated by a space in order to facilitate their entry into and accommodation within the recessed region of the body.

8. The fastening element according to any of claims 1, 2, or 3 wherein the body includes a central passageway for receiving the elongated retaining element.

9. The fastening element according to any of claims 1, 2, or 3 wherein the fastening element is integrally molded from thermoplastic material.

10. The fastening element according to any of claims 1, 2, or 3 wherein the fastening element is integrally molded from polypropylene.

11. A screw anchor for securement to a wall panel on opposite sides of an opening, in cooperation with a retaining element in the form of a screw inserted therein, said anchor being molded of synthetic plastic material and comprising:
A. a shank constituted by a pair of first arms and a pair of second arms, said second arms being hinged together at a front apex having an opening therein, said second arms being joined to respective of said first arms by side apex hinges, and B. a body attached to said shank adjacent said rear apex by a pair of normally diverging resilient pillar-like parts that merge with said rear end parts of said first arms, said pillar-like parts having a resilience resulting in the return of the pillar-like parts to their normal state when the pillar-like parts are flexed and thereafter released, whereby when said shank is folded into a collapsed conformation, it is capable of being inserted through said opening, making it possible to position said body therein, said folded shank, after passing through the opening, then being caused by the pillar-like parts to unfold towards its original configuration in which the first and second arms diverge, said pillar-like parts having a length permitting hinging thereof adjacent an inner surface of said panel at a point determined by the length of the body relative to the thickness of said panel, said body having a bore in registration with said front apex opening; and C. the improvement comprising said first and second pairs of arms being conjointly movable in a symmetric pantographic configuration when said shank is being folded into said collapsed conformation and returned toward its original configuration after said insertion in said opening, said anchor being adapted such that, after said insertion, said screw is turnable into said bore, and is threadably engaged thereby, with said screw then advancing to engage rear end extensions of said first arms and spreading them apart to begin transforming the shank into a truss whose bottom chord is formed by said first arms and which is pressed against the inner surface of said wall panel to prevent removal of said anchor, said truss being completed when said advancing screw then enters and threadably engages the opening in the front apex hinge, while remaining in engagement with the rear end extensions of said first arms, and said bottom chord is formed, with said screw thereby defining a central strut, between the front apex of the truss and the first arms, wherein said front apex and the end extensions of said first arms are engaged with said screw, whereby said arms are prevented from conjointly moving in said pantographic configuration, and whereby the truss may be collapsed by withdrawal of the screw to permit said movement of said pairs of first and second arms in said pantographic configuration for removal of the anchor from the opening.

12. An anchor as set forth in claim 11, wherein said body has a front flange which lies against the outer surface of the wall panel.

13. An anchor as set forth in claim 12, wherein said flange has a mounting fixture integral therewith for supporting an object.

14. An anchor as set forth in claim 11, wherein said body is provided with longitudinally extending fins which cut into the wall panel surrounding said opening to prevent rotation of the anchor but which do not resist axial withdrawal thereof.

15. An anchor as set forth in claim 11, wherein said plastic material is polypropylene.

16. An anchor as set forth in claim 11, wherein the front ends of the second arms are joined together by a flexible integral strap of sufficient elasticity to permit said movement in a pantographic configuration, with said strap having said front apex opening therein to accommodate the screw received in the body.

17. An anchor as set forth in claim 11, wherein said panel has a predetermined thickness and said pillar-like parts have a length causing a portion of the pillar-like parts in the event the body is shorter than the wall hole, to act as an extension of the body to make up the shortage.