GB2060090A

GB2060090A - Headsail Furling Gear for Sailboat and Ball Bearing Joint Therefor

Info

Publication number: GB2060090A
Application number: GB8030776A
Authority: GB
Original assignee: Vanguard Inc
Current assignee: Vanguard Inc
Priority date: 1979-09-26
Filing date: 1980-09-24
Publication date: 1981-04-29
Also published as: FR2465642B1; GB2060090B; FR2465642A1; DE3034482C2; DE3034482A1

Abstract

A swivel joint for disposition at each end of a luff wire of a jib or headsail of a sailing boat to enable the hoisted jib or headsail to be rolled up about the luff wire has a central shaft (10) disposed in a tubular body (12). The shaft and body have a number of opposed annular grooves (24 and 28) which define annular races each containing a plurality of bearing balls (31). The bearing balls support the shaft and tubular body in a spaced relationship and openings (32) are provided in the tubular body to allow loading of balls into the assembly. <IMAGE>

Description

SPECIFICATION Headsail Furling Gear for Sailboat and Ball Bearing Joint Therefor This invention relates to a swivel joint for a jib furling system.

Jib furling gear is a well known arrangement on a sailing boat for rolling up a jib around its luff wire while the jib is hoisted. Each end of the luff wire of the headsail or jib, which extends between the mast and the bow is provided with a swivel joint so that the luff wire can be rotated about its axis to roll up the sail. A winding drum is attached to the lower swivel joint near the tack of the sail, and a line is wrapped around the drum when the sail is unfurled. In order to furl the sail, the drum is rotated by pulling out the line, which causes the luff wire to rotate. In order to unfurl the jib, the jib sheet attached to the clew of the sail is trimmed while slacking or easing the drum line.

Conventional jib furling gear, although extremely convenient and useful, utilizes heavy and bulky swivel joints, which because of their location, result in undue windage and weight up on the mast and at the bow, which reduces the sailing performances of the boat. Also, since the jib luff wire carries very considerable loads under sailing conditions, conventional swivel joints do not offer sufficient ease of performance under heavy tension.

In view of the foregoing considerations, it would be desirable to provide swivel joints for furling gear that are extremely light and compact and yet capable to turning freely under heavy tension.

Various yacht fittings utilize ball bearings to improve ease of performance, as shown and described in U.S.A. Patents No. 3 528 645, No.

074 892 and No. 4 160 541, and other types of ball bearing systems are shown in the references cited therein.

In accordance with the present invention, a swivel joint assembly for sail furling gear comprises an elongate shaft having a plurality of annular grooves in its outer surface, a tubular member having a plurality of annular grooves in its interior wall, said shaft being received in said tubular member in a coaxial relation therewith so that the grooves of said shaft oppose respective grooves of said tubular member to define a plurality of annular spaces between said shaft and said tubular member, connection means secured to said shaft at one end of said assembly, connection means secured to said tubular member at the other end of said assembly, and a plurality of ball bearings in said annular spaces, said ball bearings supporting said shaft and tubular member in a spaced relationship for relative rotating therebetween.

The grooves from bearing races and the ball bearings maintain the inner and outer parts in a spaced relationship such that all of the thrust or axial loads between the parts are entirely borne by the balls.

Since the bearing races are an integral part of the assembly, it is possible to have a large number of bearing races and sets of ball bearings closely adjacent in a compact relation along the axis of the swivel for maximum support. The arrangement also allows the diameter of the races to be kept at a minimum relative to the axis, thus providing a minimum of bulk without sacrifice to the trust bearing properties of the assembly, particularly with regard to tension between the telescoping parts.

The race-defining parts of the assembly may be constructed from low density metals, and the balls may be composed of a durable light-weight polymer to minimize weight without undue sacrifice of strength. Openings may be provided in the outer part in communication with the races to allow loading and unloading of the balls, and a sleeve can be provided around the assembly for added integrity.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a combination reel and swivel joint assembly of the present invention for use at the lower end of the luff wire; Figure 2 is a perspective view of a swivel joint assembly of the present invention for use at the upper end of the luff wire; Figure 3 is a vertical sectional view of the assembly shown in Figure 1; Figure 4 is a schematic view of the bow portion of a sailing boat illustrating the furling gear; and Figure 5 is a schematic view of the sailing boat illustrating the partial furling of the jib.

Figures 1 and 2 show, respectively, the lower end upper portions of jib furling gear. Since the working parts of swivel joint assembly of each portion is identical, only the assembly shown in Figure 1 will be described in detail.

As shown in Figures 1 and 3, the swivel joint assembly comprises an elongated cylindrical shaft 10 having one end received through an end opening of a hollow cylindrical tube 12 and spaced therefrom. The end of the tube 12, opposite the open end, is closed and terminates in suitable connecting means such as a clevis 14 having an aligned pair of holes 1 6 for receiving a removable pin 18 for connection to a support or appropriate part of the boat. The outer end of the shaft 10 also terminates in a similar clevis 20 having similar holes and a removable pin 22.

As shown in Figure 3, the inner end portion of the shaft 10 encompassed by the tube 12 has a plurality of closely spaced, outwardly facing annular grooves 24 formed therein, said grooves preferably being equi-sized and perpendicular to the shaft. Each of the grooves 24 includes side walls 26 which diverge outward from each other from the base of the groove.

The interior wall of the tube 12 surrounding the shaft 10 has a plurality of inwardly facing annular grooves 28 formed therein, said grooves corresponding in size, profile and number with the respective shaft grooves 24 and also having diverging side walls 30.

The sets of grooves 24 and 28 define a plurality of annular spaces between the shaft 10 and the tube 12 and from the respective inner and outer races of the bearing assembly so constituted. A plurality or circle of ball bearings 31 is provided in each of the annular spaces to substantially fill such spaces and bear between the shaft and the tube. It will be noted that the balls separate the shaft 10 and the tube 12 and support these parts in an entirely spaced relation, and the height of the grooves is less than one-half the diameter of the balls. The outwardly diverging side walls 26 and 30 of the respective grooves 24 and 28 substantially improve the thrust load bearing qualities of the assembly.It may be seen that if the shaft 10 and tube are put under tension in opposite axial directions, the shaft recesses tend to urge the balls outward while the tube recesses tend to urge the balls inward whereby the balls are compressed between the parts rather than being placed in shear along the parting line between the shaft and the tube. Regardless of the thrust or tension exerted between the shaft 10 and the tube 12, these parts are free to rotate around their common axis relative to each other due to the universal nature of the ball bearings.

It may be seen that the swivel joint assembly as shown provides numerous distinct advantages.

First, the races are formed within and as an integral part of the two connecting parts that must rotate relative to one another under tension, thus eliminating the need for the usual extraneous parts such as bearing cages, retainers, separators, press-fitted parts and the like. Second, any number of groups of ball bearings may be employed, simply by using a longer shaft and tube and forming additional grooves therein, thus providing a means for adding or subtracting as much thrust capacity as required, depending upon the particular need. Third, the assembly is optimized for providing maximum bearing area in a very compact arrangement around an axis thus reducing bulk and undesirable windage on a sailing boat.

In addition, the swivel joint assembly may be very light in weight and yet support extremely heavy loads because of the multiple cooperating bearing groups. The shaft 10 and tube 12 may be made from a light weight metal or alloy, such as magnesium or aluminium. The balls 31 may be composed of a light weight polymer or plastics material. Suitable polymers include, for example, acetal homo- or co- polymers which have good load-bearing properties and have low-friction surfaces.

A further advantage is that the bearing system is self-lubricating and does not require external lubrications. The bearing system is not unduly affected by corrosion and other foreign elements such as dust, sand, salt and the like and may be cleaned by flushing with clear water.

In as much as the tube 12 is preferably continuous, means are provided for loading the balls 31 into the annular races of the assembly.

For this purpose, a plurality of round openings 32 may be provided along a line through the wall of the tube 12 and communicating with the grooves 28 thereof, said openings being sufficiently large to permit insertion or removal of individual balls.

The openings 32 may be provided in a recessed keyway 34 in the outer wall of the tube 12, and a suitable key 36 to the other strip-like material may be disposed in the keyway to prevent the balls from falling out. It will be noted that due to the bearing configuration employed, the balls do not bear against the key 36, which serves primarily as a retainer, when the swivel joint assembly is under tension, which is normally the case.

A bushing or sleeve 38 (see also Fig. 2) is preferably snugly slidably disposed around the tube 12 and is retained thereon by suitable means, such as a restricted end retained by a snap ring 40. The assembly shown in Figures 1 and 3 has parts in addition to the bushing 38, which will now be described in detail.

As shown in Figures 1 and 3, the swivel joint assembly may be formed with the additional of the components of a reel which is used as the lower component of a jib furling assembly. As shown, a cup-shaped member 50 has an opening 52 in the cup base 53 which is secured around the shaft 10 at a location outside of the bearing assembly. The upper portion of the cup-shaped member 50 overlies the outer sleeve 38, is spaced therefrom, and is segmented in the form of a plurality of spaced fingers as shown in Fig. 1.

A first disc 56 is secured to the tube 12 adjacent the open end thereof and extends radially outwardly thereof, terminating short of the inner cylindrical wall of the cup-shaped member 50 and being disposed generally parallel to the cup base 53. A second disc-like member 58 is secured to the tube 12 near the opposite end thereof, said second disc having an overtuned flange 60 overlapping the ends of the fingers 54 of the cup-shaped member 50.

From the foregoing, it may be seen that the discs 56 and 58 rotate with the tube 12 and the sleeve portion 38 of the bearing, and the cupshaped member 50 rotates with the shaft 10, if the latter should be rotated. The parts together define a semi-enclosed reel, wherein one end of a line may be secured to the sleeve 38 or secured through an opening (not shown) in one of the discs. Upon rotation of the clevis 14 connected to the tube 12, the line will wrap around the outer surface of the sleeve 38 within the confines between the discs 56 and 58 and the segmented cup-shaped member 50. Normally, the cupshaped member 50 and associated shaft 10 would be connected to the deck fitting of a sailing boat and would remain stationary, while the tube portion is rotated during furling. The segments in the cup-shaped member 50 allow a line to be lead out and away from the assembly to a convenient location.

Figures 4 and 5 illustrate the use of the presently described swivel assemblies in the furling of a headsail 70 on a sailing boat 72. As shown, the upper assembly 74 corresponds to that shown in Figure 2 and is connected between an upper portion of the mast 76 and the head 77 of the sail 70. The lower assembly 78 is connected between the tack 80 of the sail and the deck of the boat 72. The luff wire 82 extends rigidly between the two swivel joint assemblies 74 and 78 and supports the mast and the luff of the sail. A line 84 is wrapped around the reel of the lower assembly 78 when the sail is unfurled and flying.

As shown in Figure 5, in order to furl the sail 70, the reel of the swivel joint assembly 78 is rotated by pulling on the line 84, which causes the luff wire 82 to rotate between the swivel joint assembly, whereupon the sail winds up on the luff wire. In order to unfurl the sail, the jib sheet (not shown), which is attached to the clew 86 of the sail, is trimmed, causing the sail to unwind while the line 84 is again wound up on the reel of the assembly 78.

Claims

1. A swivel joint assembly for sail furling gear, said swivel joint assembly comprising an elongate shaft having a plurality of annular grooves in its outer surface, a tubular member having a plurality of annular grooves in its interior wall, said shaft being received in said tubular member in a coaxial relation therewith so that the grooves of said shaft oppose respective grooves of said tubular member to define a plurality of annular spaces between said shaft and said tubular member, connection means secured to said shaft at one end of said assembly, connection means secured to said tubular member at the other end of said assembly, and a plurality of ball bearings in said annular spaces, said ball bearings supporting said shaft and tubular member in a spaced relationship for relative rotation therebetween.

2. A swivel joint assembly as claimed in claim 1, wherein the tubular member has an opening therethrough leading into said annular spaces, said opening being sufficiently large to receive individual ball bearings for loading said ball bearings into said annular spaces.

3. A swivel joint assembly as claimed in claim 2, wherein means are provided for covering said opening.

4. A swivel joint assembly as claimed in claim 1,2 or 3 wherein a sleeve is disposed around said tubular member.

5. A swivel joint assembly as claimed in any preceding claim, wherein the connection means at each end of the assembly comprises a clevis.

6. A swivel joint assembly as claimed in any preceding claim, wherein each of the annular grooves of the shaft and tubular member has a base and side walls extending from said base and diverging outwardly from the base.

7. A swivel joint assembly as claimed in any preceding claim further comprising a reel assembly in combination therewith, said reel assembly comprising a pair of discs extending outwardly from said tubular member and rotatable therewith.

8. A swivel joint assembly as claimed in claim 7, wherein a cup-shaped member having a base is disposed around said pair of discs, said cupshaped member being rotatable with said shaft.

9. A swivel joint assembly as claimed in claim 8, wherein said cup-shaped member comprises a plurality of spaced segments.

10. A swivel joint assembly for sail furling gear, said swivel joint comprising a cylindrical shaft having a clevis at one end and a first plurality of spaced annular grooves around the shaft at the other end, a cylindrical member having a clevis at one end and a cylindrical hollow portion at the other end with a second plurality of annular grooves in said hollow portion, the grooved end of said shaft being received in the hollow portion of said cylindrical member in a coaxial relation therewith the annular grooves of one facing respective annular grooves of the other and therebetween defining annular spaces, and a plurality.of ball bearings disposed in said annular spaces, said ball bearings supporting said shaft and tubular member in a spaced relation.

11. A swivel joint assembly as claimed in any preceding claim, in which the ball bearings comprise polymeric material.

12. A luff wire for a jib sail having a swivel joint assembly as claimed in any of claims 1 to 6 or 10 at its upper end and a swivel joint assembly as claimed in claim 7, 8 or 9 at its lower end.

13. A swivel joint assembly for sail furling gear, constructed substantially as herein described with -reference to and as illustrated in the drawings.