Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: DYNAMIC BRAKE FOR A WINCH
FIELD OF THE INVENTION
The present invention pertains to winches and more particularly, it pertains
to fail-safe brakes for winches.
BACKGROUND OF THE INVENTION
Because of the consequences of a malfunction of a cable hoist or a winch,
there is always a need for improvement in these devices. Various
mechanisms have been used in the past to prevent a reverse rotation of a
winch drum in use. However, it is believed that the brake systems in the
prior art are subject to wear and deterioration from extended use and from
aging of its components.
Examples of common brakes on winch drums are described in the
following documents.
US Patent 2,181,359 issued on November 28, 1939 to A. M. Barrett,
discloses a hoist with a mechanism to slow down the descent of a load on
the hoist cable. This braking mechanism is made of a friction brake pad
mounted inside a brake drum.
US Patent 2,590,610 issued to G. S. Grosch on March 25, 1952, discloses
a braking mechanism for a winch including pawls coacting with a sun
wheel mounted in a planetary gear system.
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US Patent 2,649,281 issued to R. Hastings, Jr. on August 18, 1953,
discloses a winch including a pawl which engages the teeth of a stationary
cylinder for braking the rotation of the drum in a reverse direction.
US Patent 3,109,525 issued to A. L. Welch on November 5, 1963,
discloses a winch including a brake band surrounding a ring gear to prevent
the cable drum from rotating backwards.
US Patent 3,572,638 issued on March 30, 1971 to M. T. Funabashi,
discloses a winch and a brake. This braking mechanism comprises three
pawls engaging with a ring gear. The pawls are operated by cams and
springs to prevent reverse rotation of the winch drum. A pair of levers are
used to disengage the pawls and to allow free rotation of the winch drum.
US Patent 4,328,954 issued to A. T. Logus on May 11, 1982, discloses
another winch including a fail-safe disc-type friction brake.
US Re 36,216 issued to T.M. Telford on June 1, 1999, discloses a winch
with an automated brake including cone-shaped brake shoes mounted on
the driving shaft to cause a braking action to the drum.
Winches and hoists are often subjected to stresses beyond their safety
ratings. Winches and hoists are used in all kind of weather conditions and
can be stored away for long periods of time between uses. Therefore, in
addition to failure in use from excessive strain, these equipments are
susceptible of failure by aging of their components.
Although the winches and hoists of the prior art deserve undeniable merits,
there is a need in this field for a winch brake that has few moving parts;
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that is not subject to wear or to aging, and that does not require periodic
adjustment.
SUMMARY OF THE INVENTION
In the brake systems according to the present invention, however, there are
few moving parts. A positive drum-locking arrangement is provided to
prevent a rotation of the winch drum whenever there is no torque applied
to the input shaft of the winch.
In a first aspect of the present invention, there is provided a brake system
for a planetary gear assembly. The planetary gear assembly referenced
herein has a ring gear; an input shaft mounted coaxially with the ring gear;
a pair of pinion gears mounted in a planetary chassis rotating about the
input shaft. The brake system includes a sun gear fixedly mounted to the
input shaft inside the planetary chassis, between the pinion gears. The sun
gear is mounted inline with the centres of the pinion gears. The sun gear
has teeth protruding from its circumference surfaces on both sides thereof,
diametrically opposite from each other. The circumference surfaces on the
sun gear near the teeth are diametrically spaced a smaller distance than a
spacing between the pinion gears. The teeth are aligned in such a way that
when the sun gear is turned to a neutral position, the teeth are engaged with
the pinion gears, preventing a rotation of the pinion gears, and when the
sun gear is rotated away from the neutral position, the teeth are disengaged
from the pinion gears, allowing the pinion gears and the planetary chassis
to rotate. The sun gear has a finger extending radially therefrom. The
planetary chassis has a stopper therein for engaging with the finger and for
holding the finger and for preventing rotation of the sun gear when the
teeth are disengaged from the pinion gears. The stopping of the finger is
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also used for transmitting a torque from the input shaft to the planetary
chassis and to the pinion gears.
In another aspect of the present invention, there is provided a gearing-and-
brake system. This combination includes the brake system described above
and a movable ring gear. In this arrangement, the ring gear included in the
brake system firstly described is a stationary ring gear, and the movable
ring gear is mounted side-by-side with the stationary ring gear about the
input shaft. In this arrangement, the planetary pinion gears are wide enough
to engage with both the stationary ring gear and the movable ring gear. The
movable ring gear has fewer teeth than the stationary ring gear. In use, the
engagement of the finger with the stopper is used for transmitting a torque
from the input shaft to the planetary pinion gears and for rotating the
movable ring gear relative to the stationary ring gear. The movable ring
gear is mounted to the drum of the winch. The torque transmitted from the
input shaft is transmitted to the winch drum with a substantial mechanical
advantage.
In yet another aspect of the present invention, there is provided a brake
system for a planetary gear assembly. The planetary gear assembly
referenced herein has a ring gear; an input shaft mounted coaxially with the
ring gear; a pair of pinion gears mounted in a planetary chassis rotating
about the input shaft. The brake system includes a sun gear movably
mounted to the input shaft inside the planetary chassis, between the pinion
gears. The sun gear is mounted to the planetary chassis diametrically inline
with the centres of the pinion gears. The sun gear has teeth protruding from
its circumference surfaces on both sides thereof, diametrically opposite
from each other. The circumference surfaces on the sun gear near the teeth
are diametrically spaced a smaller distance than a spacing between the
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pinion gears. The teeth are aligned in such a way that when the sun gear is
turned to a neutral position, the teeth are engaged with the pinion gears,
preventing a rotation of the pinion gears, and when the sun gear is rotated
away from the neutral position, the teeth are disengaged from the pinion
gears, allowing the pinion gears and the planetary chassis to rotate.
=
The sun gear has at least one pair of spring seats thereon, facing opposite
directions. The planetary chassis has a pair of torsion springs mounted
thereto and acting in opposite directions against the spring seats, for
resiliently retaining the sun gear in its neutral position.
The planetary chassis is keyed to the input shaft and rotates with the input
shaft. A rotation of the input shaft forces the pinion gears to rotate and to
push the sun gear out of its neutral position for allowing the operation of
the winch.
In use, the torsion springs urge the sun gear against the trailing side of the
pinion gears to produce a pawl-and-latch noise. This audible sign is
advantageous for reassuring a user of the proper operation of the brake
system.
The word "dynamic" is used herein to designate a brake that is connected
directly to the input shaft of the winch and wherein a locking of the winch
occurs immediately upon a release of any torque on the input shaft in either
direction of rotation of that shaft. The brake is also immediately applied
when the torque on the input shaft is insufficient to overcome the torque
applied to the winch drum by the load. In other words, the brake is
associated in a most direct manner to the torque on the input shaft.
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This brief summary has been provided so that the nature of the invention
may be understood quickly. A more complete understanding of the
invention can be obtained by reference to the following detailed description
of the preferred embodiments thereof in connection with the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of a dynamic brake system for a winch are illustrated in
the attached drawings. In these drawings the same numerals are used to
identify the same elements. In the drawings;
FIG. 1 illustrates a perspective view of a winch with a brake assembly
according to the first preferred embodiment of the present invention;
FIG. 2 is a perspective view of a winch with the cover plate and handle
removed to show the first preferred dynamic brake mechanism;
FIG. 3 is a first partial elevation view of the dynamic brake mechanism
according to the first preferred embodiment, shown in a "locked-
drum" position;
FIG. 4 is a second partial elevation view of the dynamic brake mechanism
according to the first preferred embodiment, shown in an
"unlatched" position;
FIG. 5 is a perspective view of the second preferred dynamic brake
mechanism with the cover plate partly cut away to show the internal
components thereof;
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FIG. 6 is a first partial elevation view of the dynamic brake mechanism
according to the second preferred embodiment, shown in a "locked-
drum" position;
FIG. 7 is a second partial elevation view of the dynamic brake mechanism
according to the second preferred embodiment, shown in an
"unlatched" position.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
While this invention is susceptible of embodiment in many different forms,
there are shown in the drawings and will be described in details herein two
specific embodiments of a dynamic brake for a winch. It should be
understood that the present disclosure is to be considered as examples of
the principles of the invention and is not intended to limit the invention to
the embodiments illustrated and described.
Referring firstly to FIG. 1, the winch 20 with a brake according to the first
preferred embodiment of the present invention has a winch body 22; an
input shaft 24; a handle 26 mounted to the input shaft 24, a differential gear
box 28 and a winch drum 30, on which a cable or a belt (not shown) is
wound. The winch body 22 has a pair of guide rollers 32 on one side
thereof in front of the drum 30, between which the cable or belt is guided
to the drum 30. Still in FIG. 1, there can be seen the differential gear box
28 having a gearbox housing 40, a stationary ring gear 42 and a drum-drive
ring gear 44.
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Although a handle 26 is shown in FIG. 1, it will be appreciated that an
electric motor; a pulley; a sprocket or a gearbox may be used to apply
torque on the input shaft 24. Therefore, the winch with a dynamic brake 20
described herein is not limited to manual winches.
The gearbox housing 40 and the stationary ring gear 42 are fixed to the
winch body 22, and the drum-drive, or movable ring gear 44 is affixed to
the winch drum 30 and causes the winch drum 30 to rotate. The winch
drum 30 is free to rotate about the input shaft 24.
Referring now to FIG. 2, the differential gear box 28 will be described. As
it will be understood, the gearbox housing 40 is bolted to the winch body
22 in use. The winch body 22 has been removed in FIG. 2 for clarity.
Therefore, the gearbox housing 40 is considered to be stationary in FIG. 2.
The stationary ring gear 42 is also stationary as it is affixed to the gearbox
housing 40. The drum-drive, or movable ring gear 44 is mounted next to
the stationary ring gear 42. A pair of planetary pinion gears 50 are
mounted to a planetary chassis 52. The planetary chassis 52 is mounted on
bearings on the input shaft 24. One of these bearings is labelled 54 in FIG.
2. The planetary chassis 52 is free to rotate about the input shaft 24. Each
planetary pinion gear 50 has a width that is twice as much as the stationary
ring gear 42 so as to engage with both the stationary ring gear 42 and the
drum-drive ring gear 44.
The drum-drive ring gear 44 has a differing number of teeth that the
stationary ring gear 42, and the pitch of these teeth allows for the
engagement of the planetary pinion gears 50 with both ring gears 42, 44.
Because of the difference in the number of teeth in both ring gears 42, 44,
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and because of the planetary pinion gears 50 engaging both ring gears 42,
44, a rotation of the planetary chassis 52 and of the planetary pinion gears
50 causes the drum-drive ring gear 44 to rotate relative to the stationary
ring gear 42, with a significant mechanical advantage.
Referring now to FIGS. 2, 3 and 4 simultaneously, the operation of the
dynamic brake according to the first preferred embodiment of the present
invention will be explained. In FIGS. 3 and 4, in particular, the wall of the
planetary chassis 52 closest to the viewer has been removed to show the
sun gear 58 inside the planetary chassis 52. The sun gear 58 is also referred
to herein as the sun gear dial 58 to distinguish it from its equivalent in the
second preferred embodiment of the present invention, to be described
later. The sun gear dial 58 is keyed to the input shaft 24, and rotates with
the input shaft 24.
The input shaft 24, the sun gear dial 58 and the planetary pinion gears 50.
are inline with each other, along line 59 in FIG. 3 more specifically. The
sun gear dial 58 has locking gear teeth 60 protruding from its
circumference surfaces 62, diametrically opposite from each other. The
circumference surfaces 62 of the sun gear dial 58 near the teeth 60 are
diametrically spaced a distance that is smaller than a spacing between the
pinion gears 50. When the sun gear dial 58 is in a neutral position as
shown in FIG. 3, with no torque on the input shaft 24, the locking gear
teeth 60 on the sun gear dial 58 engage with both planetary pinion gears 50
and prevent a rotation of the planetary pinion gears 50, thereby preventing
a rotation of the winch drum 30. This neutral position is referred to as the
locked-drum position.
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When the sun gear dial 58 is rotated to either side from its neutral position,
such as shown in FIG. 4, the locking gear teeth 60 are moved away from
their engagement with the planetary pinion gears 50, thereby allowing the
planetary pinion gears 50 to rotate.
The sun gear dial 58 has a finger 64 along a radius thereof, at a right angle
with the alignment of the locking gear teeth 60. This finger extends
between two stoppers 66 on the planetary chassis 52. When the sun gear
dial 58 is rotated in either direction, through the handle 26 and the input
shaft 24, the finger 64 on the sun gear dial 58 abuts against one of the
stoppers 66. The finger 64 pushing against the stopper 66 causes the
planetary chassis 52 to rotate. Of course, the rotation of the planetary
chassis 52 causes the planetary pinion gears 50 to rotate in the direction of
the torque, thereby turning the winch drum 30.
A leaf spring 68 or any other device to achieve the same result, is provided
on the sun gear dial 58 or on the input shaft 24 as shown, to bring back the
sun gear dial 58 into its neutral position when no torque is applied to the
shaft 24.
Because of the large mechanical advantage obtained from the pair of ring
gears 42, 44, and because of the nature of this gearing system, a torque on
the winch drum 30 from a load cannot rotate the planetary pinion gears 50
backward and cause the locking gear teeth 60 to creep out of engagement
from the planetary pinion gears 50. However, for more certainty, the leaf
spring 68 provides a sufficient force between the sun gear dial 58 and the
planetary chassis 52, to further retain the sun gear dial 58 in its locked-
drum or neutral position.
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Referring now to FIGS. 5, 6 and 7, the brake system according to the
second preferred embodiment of the present invention will be described.
In the second preferred embodiment, the entire brake mechanism 70 is
keyed to the input shaft 24, by way of D-shaped openings 72 in the cover
plates 74, 76 of the brake mechanism 70. In this embodiment, the input
shaft 24 is modified to engage into the D-shaped openings 72.
A pair of planetary pinion gears 50 are mounted to respective axles 78 that
are retained to the cover plates 74, 76. The rotation of the cover plates 74,
76 causes the planetary pinion gears 50 to rotate with the cover plates 74,
76, and to drive the winch drum 30.
As in the previous embodiment, the planetary pinion gears 50 rotate inside
the stationary ring gear 42 and the drum-drive ring gear 44 to rotate the
winch drum 30 with a substantial mechanical advantage.
In this second preferred embodiment, the sun gear dial mentioned before
is replaced by a tilting block 80 which is referred to herein as the sun gear
block 80. The sun gear block 80 has diametrically opposite locking teeth
82. The sun gear block 80 is mounted to the input shaft 24 with a free
sliding fit, and is free to rotate about the input shaft 24. The sun gear
block 80 is held in a locking position, with the locking teeth 82 engaged
with the planetary pinion gears 50, by four torsion springs 84. The torsion
springs 84 are acting against four spring seats 86 on the sun gear block 80.
Two of these spring seats 86 are shown in dashed lines in FIG. 7, for being
on the hidden side of the sun gear block 80.
Both the sun gear dial 58 and the sun gear block 80 are also referred to
herein as the sun gear, for being mounted at the centre of the planetary gear
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system and for having a common function of preventing the rotation of the
planetary pinion gears 50.
Although four torsion springs 84 are illustrated, it will be appreciated that
a single pair of torsion springs 84 acting in opposite directions are
sufficient in most applications to move the sun gear 80 to its neutral
position.
The operation of the sun gear block 80 is substantially the same as for the
sun gear dial 58 described herein before. The teeth in both sun gears 58,
80, are diametrically opposite relative to the input shaft 24 and are movable
to be diametrically inline with a line 59 defined by the axes of the planetary
pinion gears 50, so as to engage with the teeth of the planetary pinion gears
50; to lock the position of the pinion gears 50 and to brake the winch drum
30.
The teeth on both sun gears 58,80 are also movable away from the teeth of
the pinion gears 50 to allow a rotation of the pinion gears 50 and to allow
the rotation of the winch drum 30.
The torsion springs 84 are respectively mounted on four posts 88 extending
between both cover plates 74, 76. The fixed ends of the torsion springs 84
are held in grooves 90 on the end of respective spacers 92. The fixed ends
of the torsion springs 84 are held between one of the cover plates 74, 76
and aforesaid grooves 90.
Referring now to FIG. 7, the operation of the dynamic brake 70 according
to the second preferred embodiment will be explained.
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In use, when a torque is applied to the cover plates 74,76 by the input shaft
24, in the direction of arrow 100 for example, this torque causes the
planetary pinion gears 50 to rotate in the opposite direction, in the
direction
of arrow 102.
The rotation of the planetary pinion gears 50 in the direction of arrow 102
causes the tilting of the sun gear block 80 about the input shaft 24,
substantially as shown in FIG. 7. This causes the locking teeth 82 to
disengage from their locking positions against the planetary pinion gears
50. The displacement of the locking teeth 82 away from the planetary
pinion gears 50 allows the winch drum 30 to rotate as previously explained.
In use, the torsion springs 84 maintain a reverse torque on the sun gear
block 80. Because of this reverse torque, the locking teeth 82 are urged
against the trailing side of the planetary pinion gears 50 causing a pawl-
and-latch noise. The locking teeth 82 drag against each teeth of the
planetary pinion gears, snapping against the trailing side of every tooth on
the planetary pinion gears 50, producing the pawl-and-latch noise. For
most users, this pawl-and-latch noise indicates a proper functioning of the
winch. This pawl-and-latch noise at times, may not be present in the brake
mechanism according to the first preferred embodiment.
The displacement of the sun gear block 80 from a locking position to a
disengaged position is easily done when a torque is applied to the crank
handle 26. However, because of the mechanical advantage produced by
the planetary pinion gears 50 and the double ring gears 42, 44, a torque on
the winch drum 30 cannot overcome the force of the torsion springs 84 and
cannot displace the sun gear block 80 from a locking position.
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Although FIG. 7 illustrates a movement of the sun gear block 80 in a
clockwise direction, the movement of the sun gear block 80 in the other
direction is a mirror movement which occurs when the input shaft 24 is
rotated in the opposite direction. The position of the torsion springs 84 and
the location of the spring seats 86 are mirror images of each other.
Therefore, the displacements of the sun gear block 80 to one side or to the
other relative to the planetary pinons 50 are mirror movements with mirror
actions and a same result.
The operation of the brake system in the second preferred embodiment is
the same as in the first preferred embodiment. Both brake systems are
connected directly to the input shaft 24 of the winch. The locking of the
winch occurs immediately upon a release of any torque on the input shaft
24 in either direction of rotation of that shaft. Both brake systems are also
immediately applied when the torque on the input shaft 24 is insufficient
to overcome the torque applied to the winch drum by the load.
Equivalents for the components of this winch are possible and therefore the
components and arrangements described and illustrated herein should not
be considered as limitation to the present invention.
Lastly, a pawl and latch mechanism may be provided to disengage the
brake mechanism 28 or 70 from the winch drum 30, to allow a free rotation
of the winch drum 30 if required This optional mechanism has not been
illustrated because it is not the focus of the present invention.
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