EP1961690A1

EP1961690A1 - Rotable lifting eyelet

Info

Publication number: EP1961690A1
Application number: EP07425102A
Authority: EP
Inventors: Roberto Frigerio
Original assignee: Stamperia Carcano Giuseppe SpA
Current assignee: Stamperia Carcano Giuseppe SpA
Priority date: 2007-02-26
Filing date: 2007-02-26
Publication date: 2008-08-27

Abstract

A fastening device comprises:
a fastening element (5) which presents a connection eyelet (4) and a base (3), integral therewith, having an opening (7) adapted to accommodate a screw, a screw (1) adapted to secure said element to an object to be lifted or fixed, said screw having a head (8) wider than said opening and a threaded stem (9) adapted to be introduced through said opening, characterised in that it comprises a bushing (2) adapted to be accommodated in said opening and interposed between said screw and said base, said bushing being adapted to be compressed between said screw head and a surface of said object when the screw is screwed into said object.

Description

FIELD OF THE INVENTION

The present invention relates to a fastening device, of the type comprising a screw for the fixing to an object and a rotational lifting eyelet.

PRIOR ART

There are known fastening devices for the lifting of heavy objects of various type, comprising an eyelet adapted to fix and lift by means of means of various type, such as ropes, chains, hoists or other. The eyelet is secured to the object in various manners, e.g. by means of threaded pins or screws. The eyebolt is appropriately rotational about the pin or screw, so as to allow a correct alignment thereof with respect to the direction of the force acting on it by the aforementioned lifting fixing means.
EP 0 654 611 describes a lifting eyelet having a base and an opening for fixing in an object to be lifted by means of a screw. The screw, an Allen screw, presents a flange at the head for withholding the base of the eyelet against the object to which the eyelet must be secured. Underhead, the screw presents a non-treaded portion, of larger diameter with respect to the threaded end (and such that it allows an adequate clearance with the opening of the base of the eyelet) and of such a length that, by completely screwing the threaded end into the object to be fixed, there is a sufficient clearance between the flange, the base of the eyelet and the surface of the object. This allows to completely screw the screw, with a suitable tightening torque, and allows the free rotation of the eyelet about the axis of the screw, without risk of feeding and loosening of the latter.
The examined solution is not entirely satisfactory as regards constructive simplicity. A particular type of screw is indeed required, specifically adapted to the type and to the dimensions of the eyelet to which it must be applied, and consequently not commonly available on the market. Furthermore, the machining of such a screw is more complex. The screw exemplified in the mentioned document, moreover, in order to allow the non-threaded frontal surface (normal to the screw axis) to be adequately pressed against the surface of the object to be fixed, presents a relief groove between the non-threaded portion and the threaded end; this groove increases machining complexity and contributes to weakening the screw.

SUMMARY

The above-identified problems have been solved according to the present invention by a fastening device comprising:

a fastening element which presents a connection eyelet and a base, integral therewith, having an opening adapted to accommodate a screw, a screw adapted to secure said element to an object to be lifted or fixed, said screw having a head wider than said opening and a threaded stem adapted to be introduced through said opening, characterised in that it comprises a bushing adapted to be accommodated in said opening and interposed between said screw and said base, said bushing being adapted to be compressed between said screw head and a surface of said object when the screw is screwed into said object.

The bushing is dimensioned so that between said head and said element there is a sufficient clearance to allow the rotation of the fastening element about the bushing also when the screw is completely fastened (this means that one free end of the stem which protrudes from the bushing is completely screwed) into the object. The bushing is preferably cylindrical and its internal diameter is, obviously, such to accommodate the stem of the screw, the external diameter is such to allow a sufficient clearance with the walls of said opening.
The screw must be able to be tightened in the object, compressing the bushing, with a torque suitable for the intended use of the device, generally such that it prevents the undesired loosening thereof. Therefore, the length of the stem must be sufficient so that the part of the stem protruding from the base of the element and from the bushing, part which is actually screwed into the object, is of sufficient length.
According to a preferred embodiment, the bushing presents a flange at one end and the opening presents a seat intended to accommodate said flange and, optionally, at least part of the screw head.
It is a particular object of the invention the content of the accompanying claims.

LIST OF THE FIGURES

The present invention will now be illustrated by means of the detailed description of preferred, but not exclusive, embodiments provided by way of example only, with the aid of the accompanying figures in which:

figure 1 schematically shows a perspective view of a device according to the present invention, wherein the base is shown in partial section;
figure 2 schematically shows a section view of a device according to the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

The figures show a device according to the present invention. The device presents a fastening element 5 which comprises connection eyelet 4, adapted to the passage of other means for securing the object, to which the object is adapted to be fixed. Such means may be, for example, chains, ropes, hooks or the like. Base 3, whose lower surface 6 is intended to face the surface of the object, belongs to element 5, integral with the eyelet. Said base presents an opening 7, preferably a cylindrical hole, intended to accommodate stem 9 of a screw 1 and a bushing 2. According to a preferred embodiment, the opening has an axis of symmetric essentially parallel or preferably contained on the plane on which the eyelet lays (plane perpendicular to the eyelet axis). The screw presents head 8 and threaded stem 9, whose free end, protruding from bushing 2, is intended to be screwed into a corresponding threaded hole in the object. Bushing 2 is adapted to be compressed between the surface of the object and the screw head. Its length is sufficient to allow a suitable clearance between the screw head or, as in the case shown and explained in better detail below, between flange 10 at the end of the bushing, base 3 and/or between base 3 and the surface of the object when the screw is fastened with suitable torque into the latter. It is apparent that this clearance, and a suitable clearance further existing between the external side walls of the bushing and the wall of opening 7, imparts to the element the freedom to rotate about the screw axis and with respect to the object, so as to adapt to the load direction.
According to a preferred embodiment, bushing 2 presents a flange 10, facing screw head 8; the screw head presses directly onto it; said flange is adapted to withhold fastening element 5, when the device is secured to the object, although allowing it to rotate as described above. It is however possible for the screw head to withhold element 5 with a portion radially exceeding the bushing, e.g. if the bushing presents no flange.
According to a possible embodiment of the invention, a seat 11 adapted to accommodate screw head 8, bushing flange 10 where contemplated, preferably both, may be obtained in base 3. Seat 11 may be, according to a particular embodiment of the invention, a cylindrical cavity coaxial with opening 7, but obviously wider. In such case, surface 12 delimited between the wall of opening 7 and the wall of seat 11 will interfere with the flange or screw head to withhold element 5 against the object.
Otherwise, the screw head may protrude from the opposite side with respect to the object, if preferred. In any case, the dimensioning of the various parts must allow the access with appropriate screwing and unscrewing means, also considering that the screw must generally be tightened with a predetermined torque.
There may be contemplated other screwing and unscrewing systems if required, secured to the fastening element, which may be connected to the screw so that the fastening element may rotationally drive it for screwing and unscrewing and which may be disconnected when the free rotation of the fastening element is required. Such systems are described, for example, in EP 0 654 611 . However, it may be preferable to use screwing and unscrewing means which are completely separate from the device, to avoid the accidental connection of such means with the screw, when the device is operative.
According to a preferred embodiment, the screw is an Allen screw, which makes its manoeuvre easier also in case of presence of seat 11. However, screws of other type may be used, for example hexagonal or square headed screws, accessible for example with socket wrenches, if required.
Devices for preventing the removal of the screw and of the bushing, when the device is not secured to an object, may be contemplated. This prevents the replacement with unsuitable components.
One of more protrusions (13) may be contemplated on the surface of the fastening element, in appropriate position, such as at the upper edge of seat 11. During assembly, they may be clinched so as to create interference lips, after the insertion of screw and bushing. The removal thereof is thus only possible by applying a force such as to compromise the integrity of the element itself (breakage of the interference lips), not obtainable involuntarily or without the aid of specific tools.
The width of base 3 is preferably sufficient so that an external edge of surface 6 may touch the surface of the object and exchange forces therewith, in case of a load applied to eyelet 4, specifically onto its top, in direction parallel to the axis of the eyelet itself (horizontal and laying on the plane of the drawing in figure 2), such as to consequently be able to generate the maximum possible bending force on the screw and/or on the bushing. Thus, the bending load acting on the screw and/or on the bushing may be reduced also in the unfavourable orientation conditions which the eyelet may assume in certain cases, despite its freedom of rotation as described above. A person skilled in the art will know how to dimension the base also according to the clearance left between surface of the object and flange or screw head, so as to allow a suitable contact between edge and surface of the object, with an arm such as to generate an adequate load torque in all cases. This is also considering the high safety coefficients (values even equal to 4) which many standards prescribe for dimensioning, for mechanical stress resistance, of devices of this type. The width of the base is appreciable from the drawings.
The device according to the present invention allows the use of screw of marketed type and solves the above-identified problems of the known devices.

Claims

A fastening device comprises:
a fastening element (5) which presents a connection eyelet (4) and a base (3), integral therewith, having an opening (7) adapted to accommodate a screw, a screw (1) adapted to secure said element to an object to be lifted or fixed, said screw having a head (8) wider than said opening and a threaded stem (9) adapted to be introduced through said opening, characterised in that it comprises a bushing (2) adapted to be accommodated in said opening and interposed between said screw and said base, said bushing being adapted to be compressed between the head of said screw and a surface of said object when the screw is screwed into said object.
A device according to claim 1, characterised in that the bushing presents a flange (10) at one end intended to face the screw head.
A device according to any preceding claim, characterised in that said base comprises a seat (11) adapted to accommodate said flange and/or the head of said screw.
A device according to any preceding claim, characterised in that said screw is an Allen screw.
A device according to any of the preceding claims, characterised in that said bushing is dimensioned so as to allow, with the screw being completely tightened into the object, a suitable clearance between said bushing, said base and said member to allow the rotation of said element about said bushing.
A device according to any of the preceding claims, characterised in that it comprises means adapted to prevent the undesired removal of the bushing and the screw from the opening, said means comprising protrusions (13) provided on said fastening element adapted to be clinched to generate interference lips capable of interfering with the screw head in a removal attempt.
A method for obtaining a device according to any of the claims from 1 to 5, comprising clinching, in a device according to claim 6 of said protrusions with the screw and bushing inserted in the opening.
A device according to any of the claims from 1 to 5, obtainable by the method according to claim 7.