[0001] The present invention relates to a pulling tackle comprising at least two blocks,
each having a number of pulleys, a tackle fall having two end portions and extending
between the blocks and being passed over the pulleys thereof, and a releasable locking
device associated with one of the blocks for releasably locking the fall in relation
thereto.
[0002] Such pulling tackles are used for example on board in sailing boats or ships, in
hoists, as wire stretchers, or, more generally, in cases where a manually or possibly
mechanically generated pulling force is to be augmented a certain number of times.
In the known pulling tackle one end portion of the tackle fall - the so-called standing
part - is fixed to one of the blocks, while the other end portion of the tackle fall
- the so-called hauling part - is to that which the manual or mechanical pulling force
is applied. In principle, both tackle blocks may be moveably or loosely arranged.
However, normally the block from which the free end of the hauling part extends, is
fixed, while the other block is moveable or loose. As mentioned above, tackles of
the above type may be used on board in sailing ships, for example for stretching ropes
and wires, for moving the boom, etc. In this connection it is known to provide the
fixed block with a releasable locking device for releasably locking the end of the
hauling part. This known locking fastening device comprises a channel for receiving
the hauling part and defined between a pair of swingably mounted locking members or
excentrics allowing movement of the hauling part along the channel in the direction
of a pulling force applied to the free end of the hauling part, but preventing movement
of the hauling part in the opposite direction. When it is desired to ease off or slack
the hauling part, the hauling part may be moved out of the channel defined between
the locking members while a pulling force is applied to the hauling part.
[0003] The known locking device described makes it possible to lock the hauling part and
thereby maintain a desired total length of the tackle also when the tackle blocks
are exposed to oppositely directed pulling forces. Furthermore, it is possible to
make a quick adjustment of the tackle length either by pulling the hauling part of
the tackle fall in order to reduce the length of the tackle, or by releasing the hauling
part from the locking device and slacking the hauling part so as to increase the length
of the tackle.
[0004] The mechanical advantage of the tackle, which means the ratio between the manual
or mechanical pulling force applied to the hauling part of the tackle fall, and the
pulling force provided by the moveable or loose tackle block, is dependent on the
number of pulleys in the blocks. Thus, the mechanical advantage obtainable by means
of a certain tackle cannot be changed rightaway. This is rather disadvantageous, because
the resistance or force to be overcome by means of the tackle may vary substantially,
for example because it is desired to use the tackle as a hoist for lifting loads of
rather different weights, or the tackle is used for moving the boom of a sailing ship.
In the last mentioned case the wind resistance which must be overcome in order to
move the boom may vary rather substantially, and, furthermore the resistive force
which must be overcome by the tackle for a given wind force, may vary during the swinging
movements of the boom due to variations of the vertical distances between the forces
and the rotational axis.
[0005] Therefore, when tackles of the above known type are used it is necessary to select
a tackle having a mechanical advantage which is sufficient to secure that the user
of the tackle will be able to apply a sufficient pulling force to the free end of
the hauling part of the tackle fall when the tackle is exposed to a maximum load.
However, a big mechanical advantage of the tackle also means that a relatively long
length of the hauling part has to be hauled in in order to obtain a desired reduction
of the the tackle length or a desired movement of the tackle blocks towards each other.
Thus, for example, a doubling of the mechanical advantage of the tackle means a doubling
of the length of the hauling part to be hauled in for obtaining a certain movement
of the tackle blocks towards each other. This means, that the time which is necessary
for obtaining a certain reduction of the length of the tackle will be disproportionate
for smaller tackle loads, and correspondingly, the time necessary for obtaining a
desired increase of the tackle length by releasing the hauling part of the tackle
fall will be relatively long. When tackles are used for maneuv- ring sailing boats
the prolongation of the "reaction time" is, of course, especially disadvantageous.
[0006] The present invention provides a tackle of the type described above, which makes
it possible to halve the "reaction time" or the time it takes to operate the tackle,
when the tackle load is equal to or smaller than half the estimated maximum load of
the tackle.
[0007] The tackle according to the invention is characterized in that the releaseable locking
device is adapted to lock both end portions of the fall and to selectively release
any of these end portions.
[0008] When the tackle according to the invention is used for overcoming a load exceeding
half the predetermined maximum load, the tackle may be shortened like a conventional
tackle by applying a pulling force to one of the end portions of the tackle fall,
while the other end portion is maintained in a locked position by the locking device.
However, if the force to be overcome by the tackle is about half the estimated maximum
load or less, a pulling force may simultaneously be applied to both of the end portions
of the fall. The pulling force to be applied by the user is then the double of that
necessary when only one of the end portions is hauled, but the length of -the free
end portions to be hauled in is simultaneously halved, whereby the operating time
will be reduced. If it is desired to slacken the fall and increase the distance between
the tackle blocks, both end portions of the fall may be released simultaneously irrespective
of the tackle load condition. The tackle may then be extended at least double as quickly
as if only one end portion had been released, because the pulleys in one of the blocks
need not rotate, whereby the frictional resistance is reduced.
[0009] The said locking device may be constructed in any suitable manner allowing a quick,
selective locking and release of any of the end portions of the tackle fall. As an
example, the locking device may comprise a spring biased clamping device combined
with an easily operatable actuating mechanism, which may, for example, be of an electromagnetic
type. As a tackle is able to transfer pulling forces only, in its locking position
the locking device is preferably adapted to allow movement of each of the fall end
portions in relation to the locking device in a direction tending to reduce the length
of the tackle and to prevent movement of the end portions in the opposite direction.
The length of the tackle may then be reduced even when the locking device is in its
locking position, by hauling in one or both of the fall end portions.
[0010] In its preferred embodiment the locking device defines a pair of adjacent channels
for receiving a respective one of the fall end portions therein, at least one of the
opposite wall portions of each channel including a fall engaging surface part formed
on a locking member mounted moveably so as to prevent movement of the respective fall
end portion in relation to the channel in a direction towards the associated block
and so as to allow movement of said end portion in the opposite direction. As explained
above, any of the fall end portions may be hauled in so as to reduce the length of
the tackle while the end portions remain in their respective channel. However, when
the user releases his hold of the end portion or portions so that the respective fall
end portion tends to move in the channel towards the associated block, the frictional
forces generated between the fall end portion and the engaging surface part of the
locking member cause the locking member to move so as to wedge the fall end portion
in the channel. If it is desired to slacken the fall so as to obtain a quick extension
of the tackle, one and preferably both of the fall end portions are pulled out from
the channel or channels and released.
[0011] The said end portions of the tackle fall may be in the form of separated free end
portions. However, the free ends of the fall end portions are preferably interconnected
so as to form an endless tackle fall. Thereby it may be obtained that the tackle fall
is displaced in relation to the locking device during repeated uses of the tackle
so that the wear of the fall caused by the locking device will not always take place
at the same location of the fall.
[0012] The locking device may be mounted stiffly in relation to the associated block. Thus,
the tackle block and the locking device may be fastened to the same body such as the
hull·of a ship or boat. Alternatively, the locking device may form part of or be fastened
directly to the associated tackle block which may then be swingably or otherwise moveably
mounted on the hull of a ship or another supporting structure or body, if desired.
In that case the relative position between the locking device and the associated tackle
block cannot change during use of the tackle.
[0013] However, in certain cases it may be desirable to allow a certain mutual movement
of the locking device and the corresponding tackle block. This may, for example, be
the case when a person operating the tackle wants to remain at the same position,
even if the position of the free or loose tackle block and, consequently, also the
direction in which the tackle extends, is changed during use. As an example, the situation
occurs when the tackle is used for moving the boom or other moveable parts of a sailing
boat or ship. In order to allow such a limited relative movement the locking device
and the associated block may be interconnected by resilient connection means.
[0014] It should be understood, however, that although normally not preferred, the locking
device and the associated block may be even more freely moveable in relation to each
other. Thus, for example, the locking device may be fastened to the hull of a ship
or another supporting structure while the associated tackle block is connected to
that structure only by means of the tackle fall.
[0015] The invention will now be further described with reference to the drawings, wherein
Figs. 1 and 2 are perspective view showing tackles according to the invention with
different mechanical advantages,
Fig. 3 is a tackle corresponding to that shown in Fig. 1 and operated by hauling one
of the end portions of the tackle fall,
Fig. 4 is a tackle with a bigger mechanical advantage being operated by hauling both
of the fall end portions simultaneously, and
Fig. 5 is a further embodiment of the tackle according to the invention with a mechanical
advantage corresponding to that of the tackle in Fig. 1.
[0016] All of the embodiments of the tackle according to the invention shown in Fig. 1-4
comprise a fixed tackle block 10 and a loose or free tackle block 11. Each of the
tackle blocks comprises one or more rotatably mounted pulleys or sheaves 12,13, and
14, and a so-called fall 15 is passed over these pulleys or sheaves so that free end
portions 16 and 17 thereof extend out from the fixed tackle block 10.
[0017] The fixed tackle block 10 may comprise an eye 18 which may be swingably connected
to a mounting member 19 (Fig. 1) which may be fastened to a stationary object or structure
such as the deck of a boat or ship. Similarly, the loose or free tackle block 11 may
comprise an eye 20 swingably connected to a mounting member 21, which may be fastened
to a moveable part, such as a boom of a sailing boat or ship. The free block 11 of
the embodiments shown in Figs. 2-4 may in a corresponding manner be fastened to a
moveable part by means of an eye 20, while the fixed block 10 may be stationarily
fastened by means of a joint 22 or another device allowing a certain restricted movement
of the block.
[0018] In the embodiment shown in Figs. 1-4 a locking device 23 for releaseably locking
the free end portions 16 and 17 of the fall is mounted on the fixed block. The fastening
device defines a pair of channels for receiving a respective one of the end portions
16 and 17, and these channels are defined between a stationary central part 24 and
a pair of swingably mounted eccentrics 25, vide Figs. 1 and 5. The opposite side surfaces
of the central part 24 as well as the inner surfaces of the eccentrics 25 are serrated
so as to increase friction, and the eccentrics 25 are formed and mounted so that the
end portions 16 and 17 of the fall may simultaneously or separately be pulled outwardly
as indicated by arrows and as illustrated in Figs. 3 and 4. However, the end portions
cannot be moved in the opposite direction, because such movement will cause the respective
eccentric to be moved so as to wedge the end portion between the serrated surface
part of the eccentric and the opposite serrated surface part of the central part 24.
When it is desired to release one or both of the fall end portions 16 and 17 this
may be obtained by pulling t-he end portion or. portions outwardly and simultaneously
in a direction towards U-shaped bridging members 26 bridging the channels so as to
pull the end portion or portions out of engagement with the eccentrics 25. Provided
that the tackle is exposed to tension, the tackle may be extended by easing off or
completely releasing one or both of the fall end portions. When the tackle has obtained
the desired length the end portion or portions of the fall may be reintroduced into
the channel or channels and brought into engagement with the central part 24 and the
eccentrics 26 so as to be locked automatically.
[0019] In the embodiments shown in Figs. 1-4 the locking device 23 is mounted on the tackle
block 10 by means of a pair of arms 27 allowing adjustment of the position of the
locking device 23 in relation to the block 10: Thus, the arms 27 may be swung about
a pin 28 and locked in a desired position by inserting a locking pin 29 into one of
a plurality of holes 30 formed in the arms 27.
[0020] In the embodiment shown in Fig. 1 the fixed tackle block 10 is provided with three
sheaves or pulleys of which two pulleys 12 are arranged coaxially, while the third
pulley 13 is arranged at the inner end of the block and in a plane forming right angles
with the plane defined by the pulleys 12. However, the free tackle block 11 is provided
with only two coaxial pulleys 12, and, consequently, the tackle is a double luff.
If a pulling force is applied to only one of the end portions 16 and 17 of the fall
the ratio between the pulling force applied to the end portion and the force generated
by the tackle will be 1:4. This means that the tackle increases the normally manual
pulling force applied to one of the end portions 16 and 17 fourfold. In return, the
length of the tackle is reduced only by 1/4 of the length of the fall being hauled
through the channel of the locking device 23. If, alternatively, a pulling force is
simultaneously applied to both of the end portions 16 and 17 of the fall, the mechanical
advantage of the tackle will be 1:2, which means that the tackle will only double
the total pulling force applied to the two end portions of the fall. In return, the
length of the tackle will be reduced by half the length of the fall end portion being
hauled through the channel of the locking device 23. It is understood that one and
the same tackle allows for choosing between two different mechanical advantages, because
it is possible to pull either one of the fall end portions or both of the fall end
portions simultaneously. Thus, it is possible to choose the mechanical advantage being
the most preferred in a certain situation in view of the force which is to be overcome
by means of the tackle.
[0021] In the embodiment shown in Fig. 2 the free tackle block 11 comprises only a single
sheave or pulley 13, while the fixed tackle block 10 comprises two coaxially arranged
pulleys 12. If only one of the fall end portions 16 and 17 of this embodiment is pulled,
the tackle will double the pulling force applied to the end portion, and if both end
portions are pulled simultaneously, the mechanical advantage will be 1:1, which means
that the pulling force supplied to the fall end portions will not be increased by
the tackle.
[0022] The tackle shown in Fig. 3 is a double luff like that shown in Fig. 1, and in Fig.
3 it is illustrated how one of the fall end portions 16 may be pulled, whereby the
tackle will multiply the pulling force applied to the fall end portion by four.
[0023] In the embodiment shown in Fig. 4 the free tackle block 11 comprises two coaxially
arranged sheaves or pulleys 12 and a sheave or pulley 13 arranged at the end of the
block just like the fixed block 10 shown in Fig. 1, and in Fig. 4 the fixed block
10 is provided with four sheaves or pulleys 12, which are coaxially mounted in pairs
and rotatably about parallel axes. Thus, the tackle shown in Fig. 4 is a threefold
tackle. If only one of the fall end portions is pulled, the tackle will multiply the
pulling force applied to the end portion by six. If, however, both of the fall end
portions 16 and 17 are pulled simultaneously as illustrated in Fig. 4, the pulling
force applied to the fall end portions will be multiplied only by three.
[0024] The tackle shown in Fig. 5 is a double luff just like that in Fig. 1. However, the
tackle shown in Fig. 5 comprises in addition to the fixed tackle block 10 with the
coaxial sheaves or pulleys 12 a further fixed tackle block 31, which has only one
sheave or pulley, and which is fastened to a fixed rail 32. The fall 15 is passed
over a pair of coaxial sheaves or pulleys mounted in a further tackle block 33 which
is fastened to a moveable part, such as a boom 35 by means of a mounting member 34.
The fixed tackle block 10 may then be mounted on the hull or deck (not shown) of a
sailing boat or ship, while the rail 32 may, for example, be arranged on the roof
on the deckhouse, and the tackle block 31 may be arranged displaceably along the rail
32, if desired. The locking device 23 is mounted on an arm 36 swingable around a vertical
stud to the upper end of which the fixed tackle block 10 is moveably connected, for
example by means of a universal joint. The tackle block 10 is biased in an upward
direction and is maintained in an upright position by a coil spring 37, which is arranged
between the arm 36 and the block, and which surrounds the stud, so as to allow a certain
relative movement between the locking device 23 and the tackle block 10. When one
of the fall end portions 16 and 17 is pulled, the boom 35 will be influenced by a
pulling force which is four times the force applied to the fall end portion. If both
of the fall end portions 16 and 17 are pulled simultaneously, the force applied to
the fall end portion is only doubled.
[0025] The tackle block 10 in Fig. 5 may be a so-called ratchet block having sheaves or
pulleys which may rotate only in the direction in which the fall end portions are
pulled in order to reduce the length of the tackle. Consequently, the frictional resistance
between the fall and these pulleys are substantially increased when the fall end portions
are pulled in the opposite direction after having been released from the locking device
23. If desired, the ratchet block may be changed to function as a normal block by
operation a change-over member 38. While the tackle according to the invention is
especially being described in connection with its use on board in a boat or ship it
should be understood that the tackle according to the invention may advantageously
be used also within other fields, where tackles are normally used, for example in
hoists, as wire stretchers, etc. It should also be noted that the pulling force applied
to the end portions 16 and 17 of the fall need not necessarily be provided manually,
but may also be provided mechanically. Furthermore, the locking device 23 shown in
the drawing may be replaced by any other type of locking device allowing an easily
releasable and selective locking of one or both of the end portions of the fall. Even
though the fall end portions are shown as free end portions in the drawing, it may
in some cases be desirable to interconnect the free ends of the fall end portions
so as to obtain an endless tackle fall.
1. A pulling tackle comprising at least two blocks (10,11,33), each having a number
of pulleys (12-14), a tackle fall having two end portions (16,17) and extending between
the blocks and being passed over the pulleys thereof, and a releasable locking device
(23) associated with one of the blocks for releasably -locking the fall in relation
thereto,
characterized in that the releasable locking device (25) is adapted to lock both end
portions (16,17) of the fall and to selectively release any of these end portions.
2. A tackle according to claim 1, -
characterized in that in its locking position the locking device is adapted to allow
movement of each of the fall end portions (16,17) in relation to the locking device
in a direction tending to reduce the length of the tackle and to prevent movement
of the end portions in the opposite direction.
3. A tackle according to claim 2,
characterized in that the locking device (23) defines a pair of adjacent channels
for receiving a respective one of the fall end portions (16,17) therein, at least
one of opposite wall portions of each channel including a fall engaging surface part
formed on a locking member (25) mounted moveably so as to prevent movement of the
respective fall end portion (16 or 17) in relation to the channel in a direction towards
the associated block (10), and so as to allow movement of the said end portion in
the opposite direction.
4. A tackle according to claim 3,
characterized in that the moveably mounted locking member (25) is swingable about
an axis eccentrically positioned in relation to the fall engaging surface part thereof.
5. A tackle according to any of the claims 1-4,
characterized in that the free ends of the fall end portions (16,17) are interconnected
so as to form an endless tackle fall (15).
6. A tackle according to any of the claims 1-5,
characterized in that the locking device (23) is mounted stiffly in relation to the
associated block (10).
7. A tackle according to any of the claims 1-6,
characterized in that the locking device (23) and the associated block (10) are interconnected
by resilient connecting means (37).