GB2240810A - Snap hook with projection - Google Patents

Abstract

A snap hook (7) is formed by a body comprising at its rear end a means (20) for connection with a link and at its front end an open hook (5), an elastic tongue (16) and at least one internally projecting stop (22) disposed on the inner surface (12) of the upper, continuous limb (13) of the body of the snap hook (7). The stop (22) is disposed substantially opposite the zone (23) of contact of the tongue with the inner end of the hook and the length of the chord (24) of the flexible tongue (16), maintained in contact with the inner surface (12) of the body (21) of the snap hook, is smaller than the distance between the stop (22) and the root (26) of the tongue, such that the tongue clears the stop - see fig. 3. The stop prevents a hooked item of dia. d, intruding into the region behind the tongue - see fig. 2. <IMAGE>

Description

SNAP HOOK WITH A STOP The present invention relates to a snap hook used to suspend or hook up two components, one being fastened to the rear end of the snap hook body and the other being designed to be hooked to the loop of the snap hook.

Various types of snap hook are known; some are formed by several members which may be of different materials and are assembled after manufacture; others are cast in one piece from a variety of materials, especially plastic.

In use, the snap hook is fastened at its rear end to one of the components by a connection means and at its front end to the other component which is formed by an element which slides into the inner space of the snap hook body. This element may, for example be the end of a loop borne by a strap or a fixed component such as a spindle or finger rigid with an article of luggage, clothing, etc.

The two components are thus connected by the snap hook and may be separated by disconnecting the element of the second component from the hook of the snap hook. When tension is being exerted between the components connected by the snap hook, the element of the second component is located in the space defined by the inner shape of the hook. When no tension is present, the element may move freely anywhere in the space defined by the inner surface of the snap hook body and the inner surface of its tongue. When tension is re-applied, the element may remain jammed in the rear end zone of the inner space of the snap hook; this leads to inadequate holding by the snap hook and the need to relieve the pressure between the connections so that the element can be replaced in an appropriate position for correct holding by the snap hook.Moreover, if the distance between the inner surface of the upper portion of the hook body and the inner surface of the tongue decreases from the front to the rear end of the snap hook, the element may become trapped in a particular position such that the dimension of one of the sections of the shank of the element is equal to or slightly greater than the distance which separates this inner surface of the tongue and the inner surface of the upper portion of the snap hook body. The element is thus trapped in the wrong position and it is no longer possible to depress the tongue fully to unhook the element. It is then necessary to release the element, which may be difficult and time-consuming.Since the element of the hooking member is not restrained from moving in the inner space of the snap hook, the use of this type of snap hook may lead to incorrect holding of the element as a result of its movement and have undesirable effects in order to achieve the desired result, i.e. a reliable and practical hooking and unhooking means which satisfactorily holds two links or components.

German Patent Specification DE 1 730 871 discloses two types of snap hook whose tongue is provided with a catch which is vertical with respect to the tongue bounding the housing of the element of the hooking member in the space defined by the inner shape of the hook. In the first case, the catch must be able to pass through the upper wall during the bending of the tongue into the open position, which entails risks of injury when the fingers come into contact with the catch passing through the snap hook, especially if the catch is of metal. In the second case, the vertical catch of the tongue is limited to the level of the horizontal median plane of the snap hook body and is joined by an extension from the snap hook body parallel to this catch which is slightly offset towards the inner space of the hook whose free end limits the opening stroke of the tongue.As a result of this, the dimension of the section of the element which can slide within the snap hook body is also limited, as it is a function of the opening stroke of the tongue. In this case, the element is housed in the space defined by the inner shape of the hook with considerable play.

The present invention provides a snap hook using simple and efficient means for locking the said element in the space defined longitudinally by the inner profile of the hook, while allowing the element the possibility of limited freedom which is sufficient to allow a rotary movement within the hook.

In a preferred embodiment of the present invention, the snap hook comprises a stop projecting from the inner surface of the continuous limb of the snap hook body. The projecting stop is located substantially opposite the zone of contact of the free end of the tongue with the inner surface of the hook.

When the tongue is in contact with the inner surface of the continuous limb of the snap hook body, the chord of the flexible tongue is smaller than the distance between the stop and the root of the tongue. Consequently, in the open position, the maximum cross-section of the element of the hooking member is not limited by the opening stroke of the tongue, but is a function of the height of the projecting stop which determines the distance between the end of the projecting stop and the end of the inner surface of the continuos limb of the snap hook body.

This projecting stop limits the range of movement of the element of the hooking member, but it allows the shank some freedom of movement in its housing and provides a simple, reliable and practical hooking and unhooking means for two links. This range of movement of the shank is defined by the space bounded jointly by the stop, the free end of the tongue in the closed position and the inner surface of the hook. The cross-section of the element is limited by the height of the projecting stop and not by the opening stroke of the tongue as taught by the prior art.

The snap hook may be formed by different components of the same or of different materials, but is preferably moulded in one piece in plastic material with at least one projecting stop.

The accompanying drawings show an embodiment of the snap hook of the invention with a hooking member by way of example.

For simplification purposes, the said element of the member to be hooked is shown by a round section in the drawings, although it is possible to use hooking members whose shank section is of any shape (triangular, octagonal, etc.).

Fig. 1 is a side view of a snap hook of the prior art; Fig. 2 is a side view of the snap hook of the invention with an element of a hooking member located in its housing region; Fig. 3 is a side view of the snap hook of Fig.

2 showing the insertion of the element of the hooking member into the hook of the snap hook; Fig. 4 is a top view of the snap hook; Fig. 5 is a section through the impression of the snap hook of the invention on one lateral flank in its mould.

In Fig. 1, the element or shank 1 of the hooked member 2 is not held in the space 3 bounded longitudinally by the inner surface 4 of the hook 5 shaped as a half-loop and may move into the inner space 6 of the snap hook 7 from one end position 8 to the other end position 9 in the direction of the arrow 10.

Consequently, when no tension is being exerted on the components 2, 11 joined by the snap hook 7, the shank 1 may be trapped in a given position in which the distance between the inner surface 12 of the continuous limb 13 of the snap hook body and the inner surface 14 of the tongue 16 is equal to the diameter of the shank 1 or is slightly smaller than this diameter as a result of the partial deformation properties of the surfaces in contact and the elasticity of the tongue 16.When tension is exerted on the links 2, 11 connected by the snap hook, the shank 1 may be trapped and the greater the distance between the trapped shank 1 and its initial position 3, the more there is a risk of incorrect holding by the snap hook, i.e. the more, for instance, the horizontal longitudinal median axis 17 of its body intersects the direction of the forces F, F' exerted on the snap hook by the links/components subject to loads.

Moreover, the unhooking of the shank 1 is not hindered if the latter is not located in its initial housing 3; the opening of the snap hook 7 is then blocked and it is necessary to reposition the shank 1 in its proper position 3 so that it can then be unhooked and the link/component 2 connected thereto can be released.

Figs. 2, 3 and 4, the snap hook 7 by the present invention comprises at its front end 18 an open hook in the form of a semi-circle and at its rear end 19 a means 20 for connection with a flexible link. This connection means 20 may take different forms: in the present case it is a loop 20 whose width is equal to that of the body 21 of the snap hook. It further comprises an elastic tongue 16 and at least one projecting stop 22 located on the inner surface 12 of the continuous limb 13 of the body 21 of the snap hook and opposite the contact zone 23 of the flexible tongue 16 with the inner end of the hook 5.When the flexible tongue 16 is maintained in contact with the inner surface 12 of the continuous limb 13 of the body of the snap hook 7, the chord 24 which it forms is smaller than the distance between the position 25 of the stop 22 and the point 26 of bending of the tongue 16, i.e. the root of the tongue.

In the method of construction envisaged, the projecting stop 22 is formed in one piece with the body 21 of the snap hook 7 but may also be secured by any known assembly means (screws, adhesive, etc). For the insertion of the shank 1 of the member to be hooked in its housing 3 defined longitudinally by the inner shape of the hook, the smallest dimension of the section d of the shank 1 is selected such that it is smaller than or equal to the distance h between the end 27 of the inner surface 12 of the hook and the end 28 of the projecting stop.

In order to keep the shank 1 in its housing 3, the distance h' between the inner surface 14 of the free end 29 of the tongue in the closed position and the end 28 of the projecting stop 22 is smaller than the smallest dimension of the section d of the shank.

Consequently, the end 29 of the shank, as a result of its thickness e, also acts as a stop to keep the shank 1 in the zone 3 defined by the inner shape of the hook 5.

Consequently, as a function of the smallest dimension d of the section of the shank, the distances h and h' described above are selected such that the distance h is equal to the distance h' plus the thickness e of the free end 29 of the tongue 16.

The projecting stop 22 is preferably shaped as a right-angled triangle, one of whose adjacent sides extends perpendicularly from the inner surface 12 and determines the height of the end 28 of the stop 22. In order to facilitate the insertion of the shank 1, the hypotenuse 30 of the triangle more advantageously faces towards the interior of the open hook 5 which facilitates the insertion and sliding of the shank 1 of the hooking member into its proper position 3.

The projecting stop 22 also extends at least partially over the width of the body of the snap hook 7 perpendicular to its longitudinal median axis 38 as shown in Fig. 4. However, the snap hook may comprise two projections located on either side of the horizontal longitudinal median axis 38 starting from each of the lateral sides of the body of the snap hook and thus defines a median zone free from any stop.

The snap hook af the invention is formed by known moulding methods, especially by injection moulding. Fig. 5 shows a moulding tool for the snap hook. The fundamental difference with respect to the moulds used previously to obtain snap hooks lies in the orientation of the component to be moulded with respect to the various portions forming the mould. The snap hook is moulded with the impression of its tongue in an outwardly open position 31, the latter having a parabolic shape with respect to the longitudinal horizontal median plane 39 of the snap hook body. The mould comprises three portions: a movable portion 32, a fixed portion 33 and at least one slide 34.The fixed portion 33 bears the impression of the upper portion of the body 21 of the snap hook; the moving portion 32 of the mould bears the impression of the lower portion of the body 21 of the snap hook and the outer surface 37 of the open tongue 31. The slide 34 which moves transversely to the direction of opening of the mould determines the inner profile of the snap hook body and the stop 22 and extends up to the free inner end 35 of the open tongue 31. The co-operation and complementary nature of the shape of the movable portion 32 and the slide 34 determine the parabolic form of the impression of the open tongue 31 and its thickness e. Use is preferably made of two slides making it possible to obtain a moulded snap hook in which the edges of the inner profile of the body may be rounded or bevelled on both sides.

When unmoulded, the tongue 31 of the snap hook is in an outwardly open position spaced from the hook and has a parabolic shape with respect to the longitudinal median plane 39 of the body 21 of the snap hook. The tongue 31 is then brought by manual or mechanical elastic deformation into the bearing position on the inner end of the hook. This operation is facilitated in particular if carried out immediately on discharge from the mould, since the plastic material is still warm and therefore more readily deformable. The region at the inner end 35 or root of the tongue 31 and the region of the outer end 36 of the hook 5 are preferably of a rounded shape thereby facilitating the sliding of the tongue 31 on the inner end of the hook 5.

Claims (10)

1. A snap hook formed by a body comprising at its one end a means for connection with a link and at its opposite end an open hook, an elastic tongue, at least one projecting stop disposed on the inner surface of the continuous limb of the body of the snap hook and wherein the stop is disposed substantially opposite the zone of contact of the tongue with the inner end of the hook and in that the length of the chord of the flexible tongue when pressed into contact with the said inner surface, is smaller than the distance between the position of the stop and the root of the tongue.

2. A snap hook as claimed in claim 1, wherein the projecting stop is integral with the snap hook body.

3. A snap hook as claimed in claim 1, wherein the projecting stop is formed separately and connected by any known assembly means to the body of the snap hook.

4. A snap hook as claimed in any one of claims 1 to 3, wherein the projecting stop extends at least partially over the width of the snap hook body and perpendicular to its longitudinal median axis.

5. A snap hook as claimed in any one of claims 1 to 4, comprising two of said projecting stops located to either side of the longitudinal median axis of the snap hook body and defining a median zone free from any stop.

6. A snap hook as claimed in any one of claims 1 to 5, wherein the stop has a cross-section in the form of a right-angled triangle, one of whose sides extends perpendicularly from the inner surface and determines the height of the end of the stop.

7. A snap hook as claimed in claim 6, wherein the hypotenuse of the said triangle faces the interior of the open hook.

8. A snap hook as claimed in any one of claims 1 to 7, wherein the distance between the inner surface of the free end of the tongue in its closed position and the end of the projecting stop, is smaller than the smallest dimension of the cross-section of the shank of the member to be hooked into the space defined by the inner shape of the hook.

9. A method for the production of the snap hook as claimed in any preceding claim, using a mould comprising a fixed portion, a movable portion and at least one slide, wherein the fixed portion (32) of the mould bears the impression of the continuous limb (13) of the body (21) of the snap hook (7), the movable portion (33) of the mould bears the impression of the opposite portion of the body (21) of the snap hook (7) and the outer surface (37) of the open tongue (31), and at least one slide (34) moving transversely to the direction of opening of the mould which determines the inner shape of the snap hook and the shape of the projecting stop (22) and extends up to the free inner end (35) of the tongue (31) in the open position thereby defining the inner surface of the tongue (31).

10. A snap hook substantially as herein described with reference to Figs. 2, 3 and 4 of the accompanying drawings.