U.S. patent application number 11/419087 was filed with the patent office on 2007-06-21 for synchronized roller furl system for hoisting, reefing and storing of sails.
Invention is credited to Wolfgang Falb.
Application Number | 20070137542 11/419087 |
Document ID | / |
Family ID | 38171946 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137542 |
Kind Code |
A1 |
Falb; Wolfgang |
June 21, 2007 |
Synchronized Roller Furl System for Hoisting, Reefing and Storing
of Sails
Abstract
The invention describes a combined manually and motorized driven
roller-furl sail system that enables synchronized hoisting, reefing
and stowing of sails, including automatic tightening and fixing
sails at a secure position by turning a halyard sheave manually or
setting a motor switch for Push-Button operation. Except for the
halyard sheave and manual override, the compact unit is placed
inside its mandrel and can be adapted to existing furl systems.
Inventors: |
Falb; Wolfgang;
(US) |
Correspondence
Address: |
Wolfgang Falb;Life Marine
Guido Schneble Strasse 8
Munich
80689
DE
|
Family ID: |
38171946 |
Appl. No.: |
11/419087 |
Filed: |
May 18, 2006 |
Current U.S.
Class: |
114/104 |
Current CPC
Class: |
B63H 9/1042 20130101;
B63H 2009/1057 20130101 |
Class at
Publication: |
114/104 |
International
Class: |
B63H 9/04 20060101
B63H009/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2005 |
DE |
13612999 |
Claims
1. A furling device for a sail of a sailboat having at least one
drive and a mechanic that synchronizes different rotational
movements of a halyard sheave and a mandrel, coupled by a looped
halyard, the furling device comprising: (a) a non rotatable shaft
that at one end is worked out to hold to a non rotatable joint and
that is axially contoured and extends into a sleeve like tube to
provide housing for a drive or a frictional bearing; (b) a
frictional bearing worked out of 2 cylindric elements one with a
centric bore, that fit together, forming an inner space to
accommodate disc springs and a flange of a lead screw shaft, the
device mountable into the hollow housing section of the non
rotatable shaft; (c) a flange fitting into the housing of the
frictional bearing, being part of it, with attached clutch linings
at front and backside, mounted to a lead screw with plain shaft
parts; (d) a synchronizing element, named lead-nut-spline
consisting of a front section with inner bore worked out as lead
nut profile and its outer surface as a spline profile, a middle
section with a flange with an attached clutch lining on its back
side and an outer section with a cylindric formed shaft that
continues into a flattened shaft with a screw profile at its end;
(e) a disc that has radial sectional openings and a centric hole
that encloses the flattened shaft of the said lead-nut-spline and
is able to move axially along the shafts flattened section; (f) a
spline hub of low frictional material, with a bore partly worked
out as a spline profile with a smaller forward portion of the bore
that is worked out as bearing against the said non rotatable shaft
and with an outside end worked out as outer bearing against the
inner-mandrel-flange; (g) a hollow shaft with a flange on its
forward side to mount the combined worm wheel/halyrd sheave and
that is backwards mounted around the said spline hub; (h) a worm
drive with facility to engage a winch handle into its worm screw
shaft with a housing consisting of a front and a back part, mounted
between mast and mandrel on and enclosing the said non rotatable
shaft and its worm wheel bored by the non rotatable shaft; (i) a
worm wheel where the middle section of its teeth are cut and
contoured for a V-shaped line passageway with radial bores at the
base, to form a combined worm wheel/halyard sheave and that is
bored onto the non rotatable shaft and centrical mounted to the
flange of the said hollow shaft; (j) a cylindric element of low
friction material, named inner-mandrel-flange, mounted inside the
mandrel, with bores of two different diameters with the wider one
at front bearing the outer surface of the said spline hub and the
smaller one bearing on the plain cylindrical part of the said
lead-nut-spline, the element with its front area suitable to match
the said flange with clutch lining and a backside that is formed by
serrations that fit into the radial sectional openings of the said
disc; (k) a mandrel where the foot or tacks of the sail are fixed
onto and with an inner diameter wider than the said hollow shaft
and an attached plain bearing at its inner front side; and (l) a
sheave inside the worm gear housing, partly encased in a housing
with a nut bore above the sheaves diameter for a screw with a
flange enclosed by the two housing parts of the worm gear and by
that the sheave can be moved horizontally to deviate or jam the
halyard.
2. The device of claim 1, wherein the said frictional bearing (b)
is replaced by an electric or hydraulic drive with gear and has a
lead screw formed output shaft to fit into the lead-nut-spline.
3. The device of claim 2, where the said non rotatable shaft
incorporates a funnel to provide hydraulic liquid for an hydraulic
drive or space for an electric cable for a electric motor.
Description
BACKGROUND OF THE INVENTION
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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 FIG. 2,
functionality and all remaining parts are the same. The combined
unit comprises an in-boom motorized driven sail furl system that
can be manually operated as well.
[0007] 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.
[0008] 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.
[0009] 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. [0010]
U.S. Pat. No. 5,493,988 from Feb. 27, 1996 refers to a worm gear
drive attached to a stay or mast with an at least partly inside the
worm screw mounted hydraulic drive. [0011] U.S. Pat. No. 3,608,511
shows a similar arrangement with a crank inserted inside the worm
screw. [0012] Whereas GB A 2,226,800 shows a sail driving
arrangement with an electric drive partially accommodated in a worm
screw, more specifically in the gear casing. [0013] But none of
these arrangements are able to synchronize the more complex task of
setting and reefing sails. Until now there are no synchronized
roller reef systems for medium and middle seized sailing boats
available. To the knowledge of the applicant, only few, complex
systems for super yachts are able to operate synchronized hoisting,
reefing and stowing sails by use of distinctive captive drives
mounted under or above the deck.
BRIEF SUMMARY OF THE INVENTION
[0014] 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.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015] FIG. 1 shows a general basic layout of a rig with a sail
partly furled around a boom as a mandrel.
[0016] FIG. 2 depicts a partly sectional view of the frictional
bearing with the lead screw shaft.
[0017] FIG. 3 shows a section view of the described invention with
combined worm gear, drive unit and synchronizing mechanism with
part section of a boom.
[0018] FIG. 4 shows an exploded isometric view of the lead screw
shaft, spline hub, combined lead-nut-spline, serrated
inner-mandrel-flange and cut out wheel with spring and nut.
[0019] FIG. 5A shows a enlarged partial sectional view of FIG. 3
with retracted lead-nut-spline and disengaged slide clutch but
engaged serration for heaving the sail.
[0020] FIG. 5B shows a enlarged partial sectional view of FIG. 3
with forward moved lead-nut-spline and engaged slide clutch but
disengaged serration for reefing the sail.
[0021] FIG. 6 shows an isometric view of the worm gear with a
section of the combined worm wheel/halyard sheave with line and the
case for the second sheave. For a better view the front side part
of the gear housing is omitted.
[0022] FIG. 7 shows an isometric view of the combined worm wheel,
worked out as halyard sheave with radial bores.
DETAILED DESCRIPTION OF THE INVENTION
[0023] 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.
[0024] FIG. 1 depicts a schematic layout of a boom 3 connected to
the mast 1. At the aft end 4 the boom incorporates a bearing with a
housing (not shown) that is held by the topping lift 5 and the vang
6. With raised or partly reefed sail 6, the topping lift is slack
and the boom is held by the sail and pulled down by the boom vang
line. Because the main sheet (not shown) has also to be connected
to the bearing case and the small angle between boom and vang line
is unfavorable to hold the boom down. This simple layout may not be
an optimal solution, but it is chosen here to simplify the drawings
and descriptions.
[0025] FIG. 3 shows that the forward side of the boom 15 is bored
around a hollow shaft 16 that itself is bored around a non
rotatable shaft 17 shown here with a pin hole to be mounted to the
gooseneck bracket. The case 14 of a worm gear drive with an
integrated halyard sheave is fix mounted to the non rotatable
shaft. An optional electric or hydraulic drive unit 10 with or
without a gear 11 with a lead screw 12a as output, is mounted
inside the hollow section of the non rotatable shaft. In a manual
only version the lead screw shaft 12b will be bored in a frictional
bearing FIG. 2. An endless looped halyard 7 is leads from the
halyard sheave 13 at the front of the boom to a mast top sheave 8
and from there back to the halyard sheave 13 again. The sail head 9
is attached to the looped halyard where the two ends of the loop
are connected and the sail foot is fixed to the boom.
[0026] 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.
[0027] 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.
[0028] FIG. 5A shows the function for heaving the sail assuming a
right handed lead unit is used. Applying power and turning the lead
screw output shaft 12a to the right will retract the
lead-nut-spline first. Because for this axial movement it needs to
overcome only some frictional force that will be less than the
force to turn the spline hub 21 with hollow shaft 16 and halyard
sheave 13. The drive will start rotating the lead-nut-spline FIG.
5A only after its inner bore ground 29 has reaches the output
shaft. The openings of the sectional cut out disc 24 that had been
lifted above the serrations before, are now engaged and flexible
held on to the serrations 28 of the inner-mandrel-flange 27. In a
right hand rotation the disc will move up and glide over the
serrations, acting as an overrun clutch. That is necessary because
the halyard sheave 13 with its smaller diameter has to rotate
faster to move the same length of halyard as sail is pulled by it
from the boom with its wider mandrel diameter and layers of sail.
The spline section of the lead-nut-spline 19 now turns the outer
spline hub 21 that is connected to a hollow shaft 16 that leads
forward into the worm gear housing 14 where it is mounted to the
halyard sheave 13. The looped halyard 7 on its sheave will heave
the sail 6, drawing it from the free turning mandrel or boom.
[0029] 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.
[0030] 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.
[0031] 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 FIG. 5B. The pitch of the lead
screw together with the layout and surface of the linings contact
area must be properly adjusted to apply sufficient friction for
turning the boom. Because the boom can only furl as much sail as
line is given by the halyard sheave 13 that is connected to the
lead-nut-spline, the clutch has to act as a slide clutch. It
overruns the inner-mandrel-flange 27 and the amount of frictional
force to do so will apply favorable tension to the sail being
furled. The overrun is enabled because the backward moving
lead-nut-spline 18 has lifted the sectional cut out disk 24 above
the serrations of the inner-mandrel-flange, allowing it to rotate
against it.
[0032] 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.
[0033] 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.
[0034] 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. FIG. 2 depicts a frictional bearing
in a housing 43/44 that preferably has the same dimensions as a
drive flange would have. The lead screw shaft is mounted to a
flange 12a inside of the housing. To the front and backside of the
lead screw flange are clutch linings 47 attached. The friction
force is then adjusted for example by mounting different kinds or
number of disc springs 45 to the amount that is needed to move the
lead-nut-spline. The disk springs can also used to adjust the
pressure of the lead nut spline to the inner-mandrel-flange.
[0035] 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.
[0036] Other objections that are solved by the new furl system
are:
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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 FIG. 7 is worked out with a V-profile 35 between the
(remaining) teeth with radial bores 36 at the profile base. The
resulting contours at the base and sides are adding considerable
edging length. They are of a favorable geometry also and can be
efficiently machined into the wheel.
[0043] 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.
[0044] 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.
[0045] Known Disadvantages of the New Boom Furl System:
[0046] 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.
[0047] 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.
* * * * *