GB2294736A - Linear bearing for mounting a sail - Google Patents

Abstract

A linear bearing 8, 10 for use in mounting a sail 16 for vertical movement with respect to a mast 2 comprises a carriage 24 adapted to co-operate with a track 6 formed on or affixed to the mast. The track has at least one groove 38 disposed to face substantially fully in the aft direction. The carriage comprises complementary grooves 34 to define passageways 35 to receive an array of balls. Further passageways 28 allow the balls to recirculate. By this arrangement, there is direct load transmission in a direction normal to the mast. Lateral recirculating ball passageways 30 may also be provided. <IMAGE>

Description

A LINEAR BEARING SYSTEM This invention relates to linear bearing systems and is particularly concerned with such systems which have re-circulating ball bearings. A particular, but not exclusive use for the system of the invention is in the raising and lowering of sails in sailing boats.

It is known to use a re-circulating ball bearing device in the system for hauling the boom of a yacht from one side or the other and this device is known as a traveller car. The balls circulate from a groove formed between the car and the lateral edges of a track fixed transversely of the yacht and a closed passage formed in the car, the two tracks and passages being connected in known fashion by connecting passages formed in end plates of the car. As the car travels across its track during manipulation of the boom it transmits an upward loading through the balls of the system to the track and such a system is found to operate adequately.

With the advent of so-called battened mainsails on yachts, it is found that the mainsails have become more powerful than previously experienced. A disadvantage of this is that additional drive forward and friction is put into the mast which has made hoisting and lowering the sail more difficult when the mast incorporates conventional plastics slideways.

Attempts have been made to overcome this problem by converting roller ball cars of the type used on boom systems and causing them to run on the lateral edges of a metal track secured to the rear face of the mast. Although this does work to some extent and is a measure of improvement over the use of plastics slideways, it is found that the loading which it incurs drives forwardly and pushes the batten hard against the mast. Raising and lowering the battened mainsail is still found to be slow and laborious due to the friction factor.

It is an object of this invention to provide a re-circulating linear ball race for use in a sail raising and lowering system which attempts to provide improvements in relation to the problems and shortcomings enumerated above, and/or to further provide improvements generally.

In accordance with the invention there is provided a device for use in moving a sail with respect to a mast, the device incorporating a carriage adapted to co-operate with a track formed on or affixed to the mast and a number of balls, the carriage having therein grooves which co-operate with grooves formed in the track to form together first passages to receive an array of the balls and second passages formed solely within the carriage, further passages interconnecting the first and second passages to provide continuous endless passages through which the balls can be circulated, two of the first passages being constituted by grooves formed in the lateral edges of the track and a further two of the first passages including grooves formed in the rearmost face of the track.

The carriage may be provided with means for pivotal connection to the sail and the pivotal connection may be located adjacent battens associated with the sail.

The carriage may be provided with end caps secured thereto having passages formed therein to align with the first and second passages.

In accordance with the second aspect of the invention there is provided a device for use in moving a sail with respect to a mast, together with the combination of such a device with a batten sail or the like. In accordance with this aspect of the invention the device is constructed so that a groove on a track to be mounted on the mast is disposed so as, in use, to face substantially fully in the aft direction, and the corresponding or complementary groove formed in the carriage of the device defines with the first mentioned groove a track to receive an array of balls.

By this arrangement the advantage is provided that there is direct load transmission in a direction generally normal to the mast or approximately horizontally (in calm water), whereby effective load transmission between the carriage and the track is achieved. In a preferred embodiment the batten of the sail is attached directly to the carriage for load transmission purposes, and this aspect of the invention provides the combination of a sail having such a batten, and a device for use in moving the sail.

In a preferred embodiment of the invention the device for use in moving a sail comprises four sets of recirculating ball bearings, two of these being disposed generally in the manner which has previously been tried in relation to controlling the boom on a yacht, and the additional two tracks are disposed as defined above. As a result, the inherent limitations of previously proposed forms of the cars or devices are substantially eliminated. These limitations arise from the fact that in the previous proposals for use of these cars the loading has been generally upwards or outwards in relation to the car whereby the relative disposition of the grooves formed in the track and the carriage, together with the associated recirculating balls are such that outward loads are resisted. As a direct consequence, inwardly-directed loads are not well catered for.This is due simply to the general geometry of the device arising from the above-recited facts. These factors are further aggravated by the fact that, due to the general conditions encountered when sailing, namely the presence of sea water and sand, the practical fact is that devices of this kind cannot operate in a closetolerance engineering laboratory manner, but tend to be operated with substantial clearances and slackness whereby it can often happen that the non-rotational parts on the carriage and/or the track can contact each other thereby producing a high friction situation. By the provision of the additional ball race disposed in a particular and different orientation from the ball races of the previously proposed devices, these disadvantages are appreciably reduced.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which Fig 1 is a side view of a sail mounted for vertical movement with respect to a mast of a yacht; Fig 2 is an exploded perspective view of a recirculating ball bearing carriage according to the invention; Fig 3 is a horizontal section view through the carriage and a track associated therewith; Fig 4 is a section view on the line IV-IV of Fig 3; Fig 5 is a section view on the line V-V of Fig 3; Fig 6 is a scrap view of parts seen in Fig 3 but to a larger scale.

As seen in Fig 1 of the drawings a mast 2 of a yacht has a rear face 4 to which is secured a track 6 on which a number of carriages 8, 10 are slideably mounted. As illustrated in Fig 1 the uppermost carriages 8 have pivotally mounted thereto a coupler 12 to which is mounted a head-board plate 14 secured to the apex of a sail 16.

In accordance with the present practice the sail is reinforced with a number of horizontal battens, one of which is shown as 18 within a hem 20 machined in the sail material. A batten receptacle 22 secured to the batten is pivoted to the carriage 10 for universal movement. Although only one batten is illustrated in Fig 1, other horizontal battens are secured at spaced locations heightwise of the sail.

Referring now to Figs 2 to 6 which show the construction of the carriages 8 and 10 and the track 6, a carriage 10 comprises a body 24 which is formed with a longitudinal passages 26 and 28 which are circular in cross-section and, although not fully closed are sufficiently closed to retain therein a number of steel balls 30, 31.

Also formed in the body 24 are shallow grooves 32 and 34.

The track 6 is formed with longitudinal shallow grooves 36 and 38.

The grooves 32 in the body and grooves 36 on the side edges of the track co-operate to provide passages 33. Similarly the grooves 34 in the body and grooves 38 on the rear face of the track combine to provide passages 35.

At each of the upper and lower ends of the body 24 are capping plates 40, 42 secured by screws 43 and each capping plate has formed therein connector passageways as follows.

A passageway 44 connects each of the passages 26 with its adjacent passage 33, see Fig 4. Similarly a passageway 46 connects each of the passages 28 with its adjacent passage 35, see Fig 4. Although not seen in the drawings it is to be understood that connecting passageways similar to those referred to as 44 and 46 in the lower capping plate 40 are also present in the upper capping plate 42.

Referring to Fig 4, it is clear that the balls 30 can pass downwardly along the passage 33 into the connecting passageway 44 in the lower capping plate 40 and thence upwardly along passage 26 to re-circulate through the connecting passageway 44 in the upper capping plate 42 and again enter passage 33.

Similarly, referring to Fig 5, the balls 31 can circulate through passage 28, passageway 46 in the lower capping plate 40, passage 35, returning through passageway 46 in the upper capping plate to re-enter the passage 28.

The low friction bearing afforded by the balls 31 in the passages 35 provides a smooth operation in raising or lowering of the mainsail when it is under thrust from the wind force.

The body 24 is preferably formed from a short length of extruded lightweight metal alloy, and the track 6 is also an extruded metal section, although high density plastics material may be used instead of metal alloys.

Claims (10)

C=NS

1 A device for use in moving a sail with respect to a last, the device comprising a carriage adapted to co-operate with a track, formed on or affixed to the mast; the track having a groove disposed, in use, so as to face substantially fully in the aft direction; and the carriage comprising a corresponding or complementary groove, to define, with the first mentioned groove, a passageway to receive an array of balls.

2 A device according to claim 1 wherein two grooves are provided in the track to co-operate with two grooves provided in the carriage

3 A device according to claim 2 wherein the track comprises two further grooves formed in its lateral edges and which are adapted to co-operate with corresponding or complementary grooves provided in the carriage.

4 A device for use in moving a sail with respect to a mast, the device incorporating a carriage adapted to co-operate with a track formed on or affixed to the mast and a number of balls, the carriage having therein grooves which co-operate with grooves formed in the track to form together first passages to receive an array of the balls and second passages formed solely within the carriage, further passages interconnecting the first and second passages to provide continuous endless passages through which the balls can be circulated, two of the first passages being constituted by grooves formed in the lateral edges of the track and a further two of the first passages including grooves formed in the rearmost face of the track.

S A device according to any on. of the preceding claims wherein the batten of the sail is attached directly to the carriage for load transmission purposes.

6 A device according to claim 5 wherein the carriage is provided with means for pivotal connection to a sail.

7 A device according to claim 6 wherein the pivotal connection is located adjacent battens associated with the sail.

8 A device according to any one of the preceding claims wherein the carriage is provided with end caps secured thereto having passages formed therein to align with the passages formed by the co-operating grooves.

9 The combination of a device according to any one of the preceding claims with a batten sail or the like.

10 A device for use in moving a sail with respect to a mast substantially as herein described with reference to the accompanying drawings.