Patent Application
20070137542
Since fairly long time sailboats are partly outfitted with mechanical furler systems that help hoisting, reefing and stowing sails on board. The general advancements of these systems are that the sail area while partly furled can be adjusted according to the wind pressure and that the sails are easily stowed when furled around a mandrel. Whereas jibs are furled around a rigid or flexible forestay, mainsails are rolled around a tube as a mandrel that is held by bearings either inside or outside vertically along a mast or horizontally inside a boom shell. There are also systems without a boom shell, then the mandrel is the boom.
Roller reefing systems are most critical components for the safety of a sailboat at sea. The sails are the main power system that determine speed, course and heel of a boat and—without an auxiliary engine—they are the only power source to drive the boat. For safe sailing a reef system must ensure that sails can be hoisted, reefed and stowed under any condition.
Although the further described invention can be adapted for every kind of roller reefing system, the following text and drawings will cover only an application for a boom furl system.
Up to date roller reef systems enable hoisting of a sail by pulling its halyard either manually or with help of a motorized winch while the sail unfurls freely from the turning boom (mandrel). The boom can be stopped and fixed at any position and the sail will then be close hauled by tightening the halyard and belaying it. For reefing or stowing of the sail the boom will be turned counterclockwise to furl the sail in. Commonly the boom is turned by a handle with a shaft through the mast or by a reef drum fixed at either end of the boom while the reef line is led from the drum over sheaves to the cockpit where it is pulled to turn the mandrel and furl the sail in. Heaving the sail will feed the reef line around the drum again. To accommodate long reef lines, relative big drums are needed. So, placing the drum between mast and sail requires an unfavorable wide luff-track to connect the sail to the mast, whereas placing it at the aft of the boom would need more power to furl it from the cockpit, due to more line turns. Therefore, sometimes an endless looped reef line turning a sheave connected to the boom is used; but a loose endless line will produce only enough grip to turn small sails onto the boom. Turning of the boom is sometimes also accomplished by an electric or hydraulic drive that replaces the reef drum at the aft of the boom. However, these can only support to reef or stow the sail and the halyard needs to be fed by hand to prevent the sail from sliding down and being blown-out by a wind gust. While feeding, the sailor also has to apply a proper amount of tension to the halyard to ensure clean layers of sail around the mandrel. For hoisting the sail, the halyard needs to be pulled manually or with help of a winch and the mandrel has to be controlled to prevent a blow-out of the sail in a gust. The halyard then has to be detached and belayed manually for a secure fixed sail position. Thus, to set or haul sails, the reef line has to be operated separately from the halyard rope at the same time, making it difficult for a sole person to handle.
To ease setting and reefing one would like to handle only one line, preferable the halyard, that would be connected to the reef line drum, allowing it to give the same length of way as the sail is heaved. This is what the invention is about.
The new furl system utilizes either a manually operated system with a worm drive mounted between gooseneck and boom or a combined system with either an electric or hydraulic motor coupled to the manually operated system. Except that the electric or hydraulic drive unit replaces a frictional bearing element
The manual system uses a winch handle that inserts into the worm screw shaft 30 to drive the halyard sheave and the coupled synchronizing mechanism, whereas the motorized version is driven by an electric or hydraulic drive with attached gear that are mounted inside the mandrel. Both systems drive a halyard sheave that is coupled and synchronized to the boom. To establish sufficient grip on the sheave a tensioned endless halyard loop is utilized. Connecting both line ends at the sails head and running via another sheave at the masthead back to the driven sheave between boom and mast. Due to design space limitations the synchronizing mechanism is also placed inside the front section of the boom. To save further critical space between mast and and boom, the worm wheel of the gear is worked out with a contoured passageway for the halyard, thus combining both.
Turning the halyard sheave in one direction will heave the sail, unfurling it from its boom. Reversing the direction will drive the boom and furl the sail onto it. Because the sails head is connected to the looped halyard, the rotational speed of the halyard sheave with its smaller given radius and the rotational speed of the boom with its wider and changing radius of furled layers of sail on it have to be synchronized. Although sails are preferably set with the ships bow toward the wind, the mechanism nonetheless prevents a sudden blow out of the sail in a wind gust while heaving the sail. And because furling systems are prone to jamming if the layers of the sail are not tensioned, it is important that the synchronizing mechanism tightens the sail being furled onto the boom. The synchronizing mechanism also locks the halyard sheave to the boom when hoisting is stopped automatically. The new system enables one-action or push-button operation, thus leaving the sail in a secure position without belaying it manually.
Because the manual driven system differs from the electric or hydraulic motorized version principally only by replacing the motor drive unit by a shaft that holds the lead screw in a frictional bearing and because the motorized system can be operated manually also as it is, the ongoing text and all drawings will mainly refer to an electrical driven system with an attached planetary gear that is mounted inside a boom as mandrel.
The invention relates to a new sail furl mechanism where the mandrel on which the sail is furled and a halyard sheave are driven and interconnected by a mechanism that enables synchronized hoisting, reefing and stowing of sails, including automatic tightening and fixing sails at a secure position The drive can be an electric or hydraulic motor that is placed inside the mandrel or combined with a manually operated system with a crank that engages to a worm gear with integrated halyard sheave outside but near one end of the mandrel. The manual drive can overrun the installed motor drive. Principal the new furl mechanism can be used for every sail that can be furled around a mandrel being either a tube ore a wire that is connected to a mast or on deck and can be also adapted to existing furl systems.
The following description relates to a new sail furl mechanism where the mandrel 3 on which the sail is furled and the halyard 7 that pulls the sail up are interconnected by a synchronizing mechanism. The drive 10 can be an electric or hydraulic motor that is placed inside the mandrel or an external crank that engages to a worm screw shaft 30 outside near the front end of the mandrel. Principal the new furl mechanism can be used for every sail that can be furled around a mandrel, either a tube or a wire that is connected to a fix point at mast or on deck. The following description however relates to a sail furl system where the sail furls around a boom that at one end is connected to a worm gear case 13/14 that itself is mounted to a non rotatable shaft 17 to a joint at the boat and is held at the other end by a topping lift 5 and a vang line 6. The joint for example can be a gooseneck and in the ongoing description I will assume so. For systems where the mandrel is mounted within a hollow boom shell with a slot on the upper surface that permits to enter the sail, it is common to distinguish between mandrel and boom shell, then called boom. Because the ongoing description relates to a system where the mandrel is mounted without support of a boom shell, mandrel and boom will mean the same.
To understand the synchronizing function it is best to describe the motorized force flow first and explain the manually induced function later. Shaft 12 is worked out as or mounted to a lead screw with high pitch and several starts, allowing to transmit high torque but less longitudinal forces. In a motorized version it drives a combined element 18 with an outer spline 19, further called lead-nut-spline. The combined lead-nut-spline distributes torque power between the halyard sheave and the boom. Consisting of three sections, its inner left sided section is worked out as a lead screw nut that is engaged to the drive's lead screw output shaft 12a. The outer profile of this first section is worked out as a spline profile 19, permitting it for longitudinal axial movement within and transmitting torque to a spline hub 21 mounted to a hollow shaft 16 that is fixed to the halyard sheave 13 inside the worm gear housing. The middle section of the combined lead-nut-spline is worked out as, or mounted to a flange with a clutch lining 22 attached to its backside. A cylindrical part worked out as bearing shaft 23 at the aft side of the flange allows the lead-nut-spline to be turned and moved axially along this section. In its continuation the shaft is flattened to key fit to a disk 24 with radial sectional cut out openings. The disc will be turned by the shaft and can be moved along the flattened section of it. At the end the flattened shaft is further worked out as a screw shaft to hold a spring 25 by a nut 26 against the radial cut out disc.
A cylindrical element of low friction material, further called inner-mandrel-flange 27, is radially mounted inside to the boom 15. It keeps the lead-nut-spline 18 with clutch lining 22 to its front side and the sectional cut out disc 24 to its back side. Its inner bore allows the plain cylindrical part of the lead-nut-spline to turn and move axially. The flat front side of the inner-mandrel-flange is worked out to fit to the clutch lining and its surface permits to act with it. The back side of the inner-mandrel-flange is formed out with serrations 28 that match and fit into the sectional openings of the disc 24. The spring 25, held by the nut 26 keeps the sectional cut out disk flexible along the flattened section of the shaft. It allows the disc to moved axially and to rotate in right hand direction (seen from lead screw shaft) and to glide above the serrations. A contrary rotation will engage the serrations into the openings of the disc and block the disk from turning against the inner-mandrel-flange 27 and the boom connected to it.
Acting as an overrun the sectional cut out disc 24 and the inner-mandrel-flange 27 are not able to rotate against each other now. So a sudden wind blow on the sail will not cause the boom to turn faster and unfurl excessive sail. However constant wind pressure on the sail while heaving would turn the boom at the same speed as the halyard sheave. Because of its wider diameter it would then unfurl more sail length than halyard line is pulled, bulging the sail. To hinder the boom to turn with same speed as the halyard sheave under constant wind pressure, the bearing at the aft of the boom (not shown) held by the topping lift 5 and vang line 6 must be frictional or a preferably adjustable and unidirectional brake has to be employed here.
If no manual or machine power is applied, back rotation of the boom induced by sail weight on the halyard or wind pressure on the sail will be blocked, because the sectional cut out disk is still engaged onto the serrations of the inner-mandrel-flange, hindering any rotation of the boom against the halyard sheave.
When the drive turns left, it will move the lead-nut-spline 18 backwards until its clutch lined flange presses on the front of the inner-mandrel-flange as shown in
While furling the sail onto the boom, a sudden wind blow on the sail might stop or even momentarily force the boom to a contrary rotation, but furling on, the system will soon compensate for it. To lock the system and secure the sail position a short reverse turn of the drive is necessary to disengage the slide clutch and engage the sectional cut out openings again into the serrations of the inner-mandrel-flange.
The synchronized furl mechanism will function likewise, when the halyard sheave is turned manually by a crank (not shown), engaged to the worm screw shaft 30. Turning the halyard sheave 13 and the hollow shaft with mounted spline hub by the worm screw will move the lead-nut-spline also back or forward, enabling the same functions as when it is driven by a motor. The drive 10 with gear 11 needs to rotate free but with some frictional resistance to put enough counterforce to the lead screw to move axial. Whereas an electric drive can be turned manually, a hydraulic drive has to be equipped with a bypass valve that when opened allows its hydraulic liquid to circulate.
Replacing the electric or hydraulic drive for a frictional bearing or slide clutch that holds the lead screw would provide a manual only operating system.
An aerodynamic critical section of any sailboat is the wind flow between mast and sail. Usually the sail should be in a track as near a possible to the mast. System inherent, boom furl systems with reefing drums, heavy boom shells, locking mechanism and the mechanics for manual operation are requiring more space to be accommodated than common reefing systems where the sails are just folded down onto the boom. Moreover, common slides and luff wires can hardly be used because they would build up too high being furled, needing excessive space. The necessity for a boom to have a free radius to the mast and that the goosenecks pin axis has to be vertically aligned to the sail luff are further limiting design space. Most systems therefore use a rigid or flexible second luff track that prolongs the original sails luff and allows for more distance between mast and sail luff.
Other objections that are solved by the new furl system are:
Implementing a synchronized manual mechanism in addition to a powered system needs even more room, making it difficult to upgrade it for existing systems. So, the new boom furl must not use more design space than a common roller reef drum.
And to keep the distance between mast and sail luff as short as possible the worm drive wheel is worked out to accommodate the halyard, thus combining halyard sheave with the wheel drive.
Even modern high-tech ropes do stretch. Therefore a mechanism that operates a long endless halyard that functions only properly under high line tension, must be able to compensate for elongation.
To compensate for elongation the gear housing of the new system incorporates a second sheave 32 that can be moved and set by a screw drive 33. Deviating the line 34 with the second sheave enables line length compensation.
Feeding a halyard around a sheave would put only a half turn of rope around it and would certainly not enable enough grip to heave a sail. As the grip of a line around a sheave depends on line pressure, surface friction and contact length around the sheave, these parameters have to be optimized.
Moving the second sheave 32 towards the driven halyard sheave 13 pulls more rope around it and will apply more tension to the halyard. To add further grip, the combined worm wheel/halyard sheave
The manual worm gear mechanism is an easy to use back-up system to override electric, hydraulic or mechanical failures. However if the system is mechanically blocked as could be caused by a broken spur gear or axis, the manual back-up system using the same synchronization will not work either.
To bypass a blocking mechanic and to set or reef a sail in spite of it, the second sheave 32 is retracted until the halyard is loosened and slips freely around its main sheave 13. Now the halyard with sail can be pulled manually to its desired position. Tightening the second wheel will squeeze the out coming and in coming part of the halyard together against the housing, blocking any further movement and keeping the sail in its position. If the tension doesn't allow to turn the sheave that much way inside, a small block of material 37 can be placed between the lines, before screwing the sheave in.
Known Disadvantages of the New Boom Furl System:
Handling the system by the manual driven worm drive in case of an electric or hydraulic failure will need to turn the drive with its gear also manually. This might add considerable resistance to overcome if the gear ratio of the motor drive is high. However this applies only for a motor driven system where the manual drive is a backup device. A manual only driven system would have an adjusted frictional bearing that would need less force to overcome. And having only one turn at masthead a looped halyard would not induce too much friction either.
Because one would like to leave the worm screw permanently mounted inside the gear housing, it is always driven while the system is operated. To avoid unnecessary power loss the gear should therefore be of a low ratio. Although a special crank with an attached worm screw might be usable, it would be more practical to use a common winch handle as a crank for engaging into and turning the worm screw.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13612999 | May 2005 | DE | national |
