GB2026080A

GB2026080A - Jam cleat with movable clamping jaws

Info

Publication number: GB2026080A
Application number: GB7830913A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-07-24
Filing date: 1978-07-24
Publication date: 1980-01-30
Also published as: GB2026080B

Abstract

A jam cleat, particularly for sailboats, comprises two movable clamping jaws 13 which between them form a clamping gap 23. The jaws 13 have one or more rollers 17 which cooperate with the sheet, the rollers having a toothed formation and an axially symmetrical addendum envelope. The rollers 17 are freely rotatably mounted on spindles 16 which extend parallel to the plane of movement of the clamping jaws. The sheet is pressed into the clamping gap 23 by rotating and separating the rollers 17, and it is held in the gap in mating relationship therewith and in a positively mechanical manner, but can be readily released therefrom. Under the usual load, the sheet is locked in the direction of pull 22, and in the opposite direction the sheet can be easily retightened. An additional effect is that of reducing or avoiding damage to the sheet. A plurality of pairs of rollers may also be present. An adjustable supporting surface and a likewise adjustable guide element for the sheet are provided as possible accessories. <IMAGE>

Description

SPECIFICATION Jam cleat with movable clamping jaws The invention relates to a jam cleat having two oppositely disposed toothed clamping jaws movable apart against the action of return springs tending automatically to narrow the gap between the jaws.

Jam cleats of this kind are used for exam ple, on sailboats and serve to belay,i.e. secure, a sheet (rope), for example the foresheet. The clamping jaws are so designed and are movable in such a way that the gap between them tends to narrow and to secure the sheet when the latter is hauled in one direction, whereas a pull in the opposite direction widens the gap at least to such an extent that the sheet can be drawn through it substantially without hindrance. To cater for the sailing manoeuvres that have to be carried out, the sheet should be capable of being inserted and removed as rapidly as possible and without difficulty.

A known jam cleat is what is called the "Currey cleat". This cleat consists of two clamping jaws pivotably secured to a support plate. The jaws are positioned with their oppositely disposed toothed surfaces inclined towards each other, so that between them they form a narrow progressively widening Vshaped or dovetail-like gap in which the sheet can be placed. The clamping jaws can be swung outwards about swivel pins so that the gap between them can be widened to enable the sheet to be inserted. After the sheet has been inserted, the clamping jaws are swung back again by means of return springs so that the toothed clamping faces then grip the sheet between them. The clamping action is considerably intensified by pulling on the sheet in the direction for closing the jam cleat (self-clamping, as it is called).With such a jam cleat it is possible to pull the sheet further towards the narrow opening (tip of the V) of the gap, i.e. to shorten the sheet, while it is unable to move in the opposite direction.

In the case of a cleat of this kind,it is known to facilitate insertion of the sheet by increasing the depth of the clamping jaws and by providing the additional clamping surface so obtained with a series of grooves arranged obliquely one after the other. At the upper boundary of the clamping face the grooves form an undulating slanting surface. On application of pressure to the sheet, the latter slides over the slanting surface into the interior of the clamping gap without the need for pulling on the clamping jaws.

Cleats of this kind suffer from the serious disadvantage that release of the sheet in an emergency is frequently very troublesome. In stormy wind conditions a sheet is often subjected to a tensile load of several times 100 kg, so that a person standing on the opposite side of the boat has to apply a very great iever action in order to lift the sheet and so release it from the cleat. Add to this the fixed pressure of the clamping jaws of the sheet, then loss of time can often occur that is critical as to whether the boat capsizes or not.

Furthermore, the sheet is eventually damaged by being pulled out of the toothed cleat so that it usually has to be replaced at latest by the end of the season.

The object of the invention is to provide a jam cleat, from which the sheet can be rapidly and easily released in an emergency, and in which the sheet is not subjected to damage even when pulled vigorously and suddenly.

According to the invention there is provided a jam cleat having two oppositely disposed toothed clamping jaws movable apart against the action of return springs tending automatically to narrow the gap between the jaws, wherein each clamping jaw comprises at least one roller having a toothed profile and freely rotatably mounted on a spindle which extends parallel to the plane of movement of the jaws.

In principle, therefore, the invention consists mainly in replacing the known "static" toothed formation on the clamping jaws by a "movable"formation.

The sheet can be inserted in a jam cleat of this kind by means of light pressure, and it can be likewise easily removed therefrom by being pulled in the transverse direction. The sheet is nevertheless reliably secured when subjected to tensile loading in the direction for jamming since, in the rest position, its longitudinal axis lies below a plane that extends through two oppositely disposed roller spindles. This means that the rollers and therefore the clamping jaws require to be slightly separated when removing the sheet, and such separation is possible because of the rolling action requiring little expenditure of force. Premature wear by rubbing over the edges of the teeth is thus largely precluded.

A particularly simple and effective construction of a jam cleat of this kind is obtained if the clamping jaws are formed as pivotable Cshaped or bowed elements, of which at least one limb is traversed by the spindle carrying the roller. A particular advantage accrues if the clamping jaws are secured on a support plate by hinge pins extending at right angles to the support plate, the roller spindles being disposed in a plane or planes at right angles to the hinge pins.

The oppositely disposed roller spindles lie in the same horizontal plane. They may be disposed parallel to each other or diverge from each other to form a V, so that the rollers themselves form a progressively widening clamping gap.

If a plurality of pairs of rollers is superposed in each of the clamping jaws, the roller spindles are preferably fitted at approximately the same distance apart in the vertical direc tion and are arranged parallel to each other. A plurality of pairs of rollers offers the additional advantage that a number of cavities is formed between them, these cavities being disposed one above the other in the manner of the storeys of a building. If the sheet requires to be firmly secured it can be readily forced under slightly greater pressure into the next lowest cavity.

In a further very advantageous arrangement, the clamping jaws may form housings which enclose half or more than half the width of the rollers. Each roller can be mounted in its housing in such a way that the roller spindle is located approximately in an imaginary plane forming the outer limit of the housing. In this case one half of the roller is hidden in the housing, whereas the other half is always readily visible. However, the roller spindle can be set back into the interior of the clamping jaw or housing to an extent such that only a small portion of the surface of the roller is readily visible. These possible ways of mounting the roller spindle are referred to as "middle spindle mounting" and "inner spindle mounting".

The rollers can be of any shape suitable for the purposes of the invention. Thus for example, the surface of the rollers can be composed of frusto-conical configurations which combine to form a saw-tooth contour. However, the surface of the rollers can be in the form of a saw-tooth screw-thread. The addendum envelope of this surface may be of cylindrical, ellipsoidal, spindle-like, barrelled or frusto-concial shape. In the case of a cleat having a dovetail-shaped clamping gap, the ellipsoidal or spindle-like shape is particularly suitable, whereas for a V-shaped clamping gap, the fursto-conical shape of surface is especially suitable.

Apart from an axially symmetrical or a helical form of toothing, use can also be made of a completely irregular toothed arrangement in the form of grooving. Interengagement of the toothed formations on the oppositely disposed rollers is not necessary. Insertion of the sheet may even be facilitated if the gaps between the teeth of one of the oppositely disposed formations are narrower than those of the other by up to 1 mm, for example. The teeth on the surfaces of the rollers are advantageously relatively blunt so as to avoid damage to the sheet.

The spindles of the rollers in each of the clamping jaws are preferably secured by rivetting or screwing, or they can be fitted in a readily detachable manner so that the rollers can be exchanged without difficulty. Preferred materials for the rollers are light metals or a relatively soft plastics material, such as polyamide or phenolic resin. This offers the advantage of low production costs and of minimum damage to the sheet. Furthermore, the total weight of the jam cleat is thus reduced compared with that of known jam cleats. Since a boat normally has twenty or more jam cleats, this results in a saving in weight which is of considerable importance to people who treat sailing as a sport.

Release of the sheet from the jam cleat of the invention is a simple matter since it merely involves reversel of the procedure used for belaying it. Whereas, when belaying the sheet, the latter is first moved over the curved faces of the rollers above the spindles, thus causing the rollers also to move, and then, simply by the application of slight pressure which separates the clamping jaws, the sheet has to push its way through the narrowest portion of the gap where the two rollers are closest to each other, conversely, when lifting the sheet, the latter moves into the gap at the lower side of the rollers and then simply has to push its way upwardly through the narrowest part of the gap again, for which purpose relatively small expenditure of force suffices.

Particular advantage is obtained if the support plate is provided with an adjustable supporting surface for the sheet between the oppositely disposed rollers and below the spindles of the bottom rollers (when more than one pair of rollers is used). This supporting surface can advantageously be provided by a slide member which has an inclined bearing surface in contact with a complementarily inclined surface of the support plate and which is connected to an adjusting device acting in the direction of the downward slope forming the inclined surface. In this way the sheet, in its bottom portion, can be moved into optimum relationship with the clamping jaws and rollers. Furthermore, the jam cleat can be adjusted to suit different diameters of sheet.

Yet another advantage is achieved if a vertically displaceable guide element for the sheet is provided at that side of the space between the clamping jaws, that faces away from the direction in which the sheet is jammed, and beyond the ends of the rollers. This guide element is preferably a screw having a mushroom-shaped head which can be screwed out of and into the support plate. If this guide element is suitably set, the sheet can be released more readily in case of emergency, particularly when its end is looped through 1 80"C. This situation occurs, for example, when the sheet is secured to what is known as a traveller carriage. By means of a gentle pull on the sheet, the guide element causes the sheet to be released from the clamping jaws.

Some preferred embodiments of a jam cleat according to the invention will now be described by way of example, reference being made to the accompanying drawings in which: Figure 1 is a perspective illustration of a jam cleat in accordance with the invention and comprising two rollers having a barrelled addendum envelope; Figure 2 is a plan view of a clamping jaw comprising a roller having a frusto-conical addendum envelope; Figure 3 is a plan view of a clamping jaw comprising a roller having a cylindrical addendum envelope; Figure 4 is an end view, looking in the direction in which the clamping gap narrows of a jam cleat comprising two superposed pairs of rollers; Figure 5 is a plan view of the jam cleat of Fig. 4; Figure 6 is a side view of part of a clamping jaw providing a housing extending over half the periphery of a roller;; Figure 7 is an end view of part of two clamping jaws, the rollers of which are enclosed over more than half their periphery, an inserted sheet also being shown; Figure 8 is a plan view of a single roller having a surface resembling a saw-tooth screw-thread and a barrelled addendum envelope similar to that shown in Fig. 1; and Figure 9 is a vertical section along the axis of symmetry through a modification of the Fig. 1 arrangement comprising an adjustable supporting surface and a vertically displaceable guide element for the sheet.

Fig. 1 shows a support plate 10 of substantially trapezoidal shape which is provided with two hinge pins 1 2 near its longer end 11.

Pivotably mounted on each hinge pin is a clamping jaw 1 3 which is bowed or C-shaped in plan and has two limbs 14 and 1 5. A spindle 16, on which a roller 1 7 is freely rotatably mounted, passes through the limbs 14 and 15 of each jaw 13.

Near its limb 1 5 each clamping jaw 1 3 has a hole 18 (Figs. 2 and 3) by means of which it is mounted on the hinge pin 1 2 by a screwbolt 1 9. The axes of the hinge pins 1 2 and of the screw-bolts 1 9 are perpendicular to the support plate 10 so that the clamping jaws 13, the common plane of symmetry of which extends perpendicular to the support plate 10, can be pivoted in a plane parallel to the support plate 10, in the directions indicated by the two double-headed arrows 20.The spindles 1 6 extend parallel to the support plate 1 0. As viewed in Fig. 1, the pivot axes of the clamping jaws are located forwardly of the end faces 21 of the rollers 1 7. The effect of this arrangement is that when a pull is exerted in the direction of the arrow 22 by a sheet (not shown) laid between the rollers 1 7 in the position where said arrow is drawn, the gap 23 formed between the rollers 1 7 tends to narrow. Conversely, force applied in the direction opposite that indicated by the arrow 22 tends to increase the width of the gap 23.

Provided in the zone of the hinge pins 1 2 and the screw-bolts 1 9 are return springs (known per se) which are not shown in Fig. 1 and by means of which the clamping jaws 1 3 are biassed in a direction causing narrowing of the gap 23.

The one-piece rollers 1 7 each have a surface which can be thought of as being made up of frusto-conical elements, the flat end faces of which face in the direction indicated by the arrow 22 and providing the rollers with teeth 27. The addendum envelope of the rollers can be described as being ellipsoidal or barrelled.

The clamping jaws 1 3 shown in Figs. 2 and 3 differ from those of Fig. 1 only in that the roller 1 7a (Fig. 2) has a frusto-conical addendum envelope, whereas the roller 1 7b (Fig. 3) has a cylindrical addendum envelope.

Referring to Fig. 4, the support plate 10 carries two clamping jaws 1 3a in each of which is arranged two superposed rollers 1 7.

The spindles 1 6 of these rollers are parallel to each other and to the plane of the support plate 1 0. The rollers 1 7 arranged in each clamping jaw 1 3a lie in a plane at right angles to the support plate 10, the two vertical planes forming a V as shown in Fig. 5.

Fig. 6 shows part of a clamping jaw 1 3b which is designed as a housing to enclose half of the roller 17, the halving plane coinciding with the axis of the spindle 1 6.

Fig. 7 shows parts of two clamping jaws 13e which are likewise designed as housings and enclose more than half of each of the rollers 1 7. A sheet 24 is shown between the rollers 1 7 and rests on the support plate 10 in contact with the two rollers 1 7. The axis of the sheet 24, extending at right angles to the plane of the drawing, lies below a plane extending through the spindles 1 6. In order to bring the sheet 24 into this position or to release it therefrom, it must pass through the narrowest part of the gap between the two rollers 17, for which purpose the clamping jaws 13 c must be moved apart in the direction indicated by the two arrows 25.

Fig. 8 shows a roller 1 7c, the surface of which resembles a saw-tooth screw-thread, the substantially flat end faces 26 of the sawtooth contour thus formed facing in the opposite direction to that (arrow 22) in which the sheet pulls. In the same way as with the rollers shown in Figs. 2 and 3, the roller 1 7c of Fig. 8 forms teeth 27, the outer edges of which are slightly rounded so as to avoid damage to the sheet. The addendum envelope of the teeth 27 in Fig. 8 is elliptical or barrelled.

Fig. 9 illustrates a support plate 10a which, between oppositely disposed rollers 1 7 and below the spindles 1 6 of these rollers, i.e. in the vertical plane of symmetry of the jam cleat as a whole, is provided with an adjustable supporting surface 28 for the sheet 24, which here is shown only in broken lines. The supporting surface 28 forms part of a slide 29 having an inclined surface 30 which is in contact with a complementarily inclined surface 31 of the support plate 10a. By displac ing the slide 29 in the directions indicated by the double-headed arrow, the distance between the supporting surface 28 and the upper surface 32 of the support plate 1 0a can be infinitely varied so that the jam cleat can be adjusted to suit clamping requirements and/or different diameters of sheet 24.The slide 29 is displaced by means of an adjusting device 33 which consists of a threaded spindle 34 which is mounted in the support plate 1 0a and which is in meshing engagement with the slide 29 and does not impede up and down movement of the slide since a slot connection 35 is provided. Also provided in the carrier plate 1 Oa is a vertically displaceable guide element 36 for the sheet 24. Element 36 is located at the end of the clamping gap that faces in the direction opposite to that in which the sheet 24 pulls and is located beyond the ends of the rollers 1 7. Guide element 36 is a screw 37 having a mushroom-shaped head 38 that can be screwed out of and into the supporting plate 1 0a. It will be understood that, by means of the guide element, the sheet 24 can be deflected away from the support plate 1 0a into different levels, it being possible to adjust the level so that a gentle pull in the direction indicated by the arrows 39 enables the sheet to be withdrawn from the clamping gap.

Claims

1. A jam cleat having two oppositely disposed toothed clamping jaws movable apart against the action of return springs tending automatically to narrow the gap between the jaws, wherein each clamping jaw comprises at least one roller having a toothed profile and freely rotatably mounted on a spindle which extends parallel to the plane of movement of the jaws.

2. A jam cleat according to Claim 1, wherein the clamping jaws comprise pivotable C-shaped or bowed elements of which at least one limb is traversed by the spindle.

3. A jam cleat according to Claim 2, wherein the clamping jaws are pivotally mounted on a support plate by means of hinge pins extending at right angles to the support plate, and the spindles are disposed in a plane or planes at right angles to the hinge pins.

4. A jam cleat according to Claim 1, wherein the spindles of oppositely disposed rollers are relatively angularly oriented to form a V.

5. A jam cleat according to Claim 1, wherein a plurality of rollers are mounted one above the other on parallel spindles in each clamping jaw.

6. A jam cleat according to Claim 1, wherein the clamping jaws are formed as housings to envelope half of the periphery of the rollers.

7. A jam cleat according to Claim 1, wherein the clamping jaws are formed as housings to envelope more than half of the periphery of the rollers.

8. A jam cleat according to Claim 1, wherein the addendum envelope of each roller is ellipsoidal.

9. A jam cleat according to Claim 1, wherein the addendum even lop of each roller is frusto-conical.

10. A jam cleat according to Claim 1, wherein the addendum envelope of each roller is cylindrical.

11. A jam cleat according to Claim 1, wherein each roller is composed of a stack of frusto-conical elements which together form a saw-tooth contour, the substantially flat end faces of the saw-tooth profile facing in a direction opposite to that in which the sheet is jammed.

1 2. A jam cleat according to Claim 1, wherein the surface of each roller is in the form of a saw-tooth screw-thread having substantially flat faces facing in a direction opposite to that in which the sheet is jammed.

1 3. A jam cleat according to Claims 1 to 3, wherein the support plate is provided with an adjustable supporting surface for the sheet in the gap between oppositely disposed rollers and below the spindles of the or the bottom rollers.

14. A jam cleat according to Claim 13, wherein the supporting surface is provided by a a slide member having an inclined bearing surface in contact with a complementarily inclined surface of the support plate, and the slide member is connected to an adjusting device acting in the longitudinal direction of the clamping gap.

15. A jam cleat according to Claims 1 to 3, wherein a vertically displaceable guide element for the sheet is located at that end of the clamping gap that faces in the direction opposite to that in which the sheet is jammed, and beyond the ends of the rollers.

1 6. A jam cleat according to Claim 15, wherein the guide element is a screw having a mushroom-shaped head and displaceable out of and into the support plate.

1 7. A jam cleat substantially as hereinbefore described with reference to the accompanying drawings.