Note: Descriptions are shown in the official language in which they were submitted.
CA 02304440 2000-04-13
TITLE OF THE INVENTION
BELT HOIST
BACKGROUND OF THE INVENTION
This application is a division of Canadian Patent Application Serial
Number 2,209,536 filed on July 3, 1997. The claims of this application are
directed to a belt hoist to satisfy unity of invention requirements of the
Canadian
Patent Office. However, in order to assist the reader to readily understand
the
overall invention including all features which are inextricably bound up in
one
and the same inventive concept, the teachings of those features and the broad
objects relating thereto are all retained in the present disclosure as they
were
in the disclosure of the parent application aforesaid but the claims are
limited to
the features identified hereinbefore.
Field of the Invention
The present invention relates to a belt hoist wherein a winding member
for winding a belt thereon is rotationally supported between a pair of
opposing
side plates.
Description of the Prior Art
Belt hoists of this kind are known as disclosed by Japanese Laid-Open
Utility Model Publications No. Hei 6(1994)-25290 and No. Hei 5(1993)-32386,
for example. The belt hoists disclosed by these publications are so structured
that a flat belt retaining a hook or equivalent at its front end portion is
wound
around the winding member rotationally driven by a normal and reverse rotation
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motor. The belt is taken up on or paid out from the winding member to hoist up
and down or drag a load through the belt.
Further, the belt hoist disclosed by the Japanese Laid-Open Utility Model
Publications No. Hei 5(1993)-32386 is so structured that parts to be detected
are fitted to the belt at several points along a lengthwise direction thereof
and
an overwinding detecting sensor and an over-lowering detecting sensor are
retained to a fixed member of the hoist with spacing from the belt at a
specified
interval to be opposite to the parts to be detected at the time of the
overwinding
and over-lowering of the belt. When the respective sensors are opposite to the
related parts to be detected, rotation of the motor is stopped according to
the
output from the sensors to prevent the overwinding of the belt.
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This constructed belt hoist of conventional type has the advantage that
various kinds of components of the hoist can be prevented from breakage
resulting from the overwinding of the belt at the time of hoisting up and down
or
dragging a load through the belt, but it has disadvantages that parts count
increases and thus structure is complicated, due to the structure that the
parts
to be detected are provided at several points of the belt and the sensors are
provided at the fixed member. In addition, since this conventional type belt
hoist has no means for preventing the belt from being taken up with twisted,
the
belt may sometimes be coiled randomly.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a belt hoist
which enables the belt to be prevented from taken up in a twisted state and
from being overwound, with simple structure.
This invention is directed to a belt hoist which comprises a winding
member around which a belt is wound; drive means for driving the winding
member; a random coil preventing member pressed against the belt wound
around the winding member to prevent a random coil of the belt, the random
coil preventing member being movable in response to changes in circle
diameter of the belt; and control means for controlling drive of the drive
means
in association with the random coil preventing member when the circle diameter
becomes a specified diameter.
According to this invention, when the belt wound around the winding
member is wound or unwound by the winding member being rotationally driven
by the drive means at the time of raising or lowering or dragging a heavy load
with the hoist, the belt is kept on being pressed against the winding member
by
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the random coil preventing member which is movable in response to changes in
circle diameter of the belt resulting from the raising or lowering of the
load.
Thus, the random coil preventing member is always pressed against the belt so
that the belt can be wound on the winding member in a proper posture at all
times without being twisted, thus preventing the random coil of the belt
against
the winding member.
Further, the drive of the drive means is controlled via the control means
associated with the random coil preventing member movable in response to
changes in circle diameter of the belt. The drive means is kept on driving to
wind and unwind the belt until the circle diameter of the belt becomes a
specified diameter and is stopped when the circle diameter reaches the
specified diameter, by the control of the control means associated with the
random coil preventing means. Thus, the overwinding of the belt and the
resulting breakage of the components of the hoist can be prevented.
Besides, the prevention of the overwinding of the belt is effected through
the use of the random coil preventing member which is associated with the
control means for controlling the drive of the driving means. This can provide
the advantages that the prevention of the random coil and overwinding of the
belt can be achieved with reduced parts count and simplified structure, and
the
hoist can be manufactured at reduced costs as a whole.
Further, it is preferable in this case that the random coil preventing
member is so supported to the winding member as to be swingable outwardly
with respect to a radial direction of the winding member and is always biased
toward an outer periphery of the winding member by a biasing spring.
With this construction in which the random coil preventing member is so
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supported as to freely swing and also is biased to the outer periphery of the
winding member by the biasing spring, although the circle diameter of the belt
changes in response to the winding or unwinding of the belt wound around the
winding member, variations in the biasing force acting to the belt can be
minimized to effectively prevent the belt from being twisted no matter what
circle diameter of the belt is. Also, the random coil preventing member can be
surely swung in response to changes in circle diameter of the belt to
accurately
control the drive of the drive means with the aid of the random coil
preventing
member.
Desirably, the belt hoist further comprises (i) protrusions provided at an
axial end portion of a pivot shaft on which the random coil preventing member
is pivotally supported and (ii) detection switches capable of operation by
contact with the protrusions when the circle diameter of the belt reaches a
specified diameter.
The protrusions and detection switches serving as the control means are
provided at the axial end portion of the pivot shaft of the random coil
preventing
member, and the protrusions are brought into contact with the switches via
which the drive of the driving means is controlled when the circular diameter
of
the belt reaches a specified diameter. This arrangement can provide the
advantage in that the protrusions and the switches can be located at an
outside
of a support member supporting the random coil preventing member so that
maintenance of the detection switches can be easily performed without
affecting the random coil preventing member and the winding and unwinding of
the belt. Besides, the use of these protrusions and detection switches
enables the control means to be simplified in structure and also enables the
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drive of the drive means to be surely controlled by the control means.
Further, this invention is also directed to a belt hoist comprising a
winding member around which a belt is wound spirally in a multilayer
configuration, said winding member being rotatably supported between two
s opposing side plates; and a belt guide having a belt guide portion which is
arranged between said two side plates, said belt guide being freely slidable
along a radial direction of said winding member in response to variations in
the
circle diameter of said belt wound around said winding member whereby the belt
is continually pressed against said winding member, so as to allow a winding
to action of the belt onto said winding member.
According to this invention, since the belt is guided by the belt guide
portion of the belt guide when taken up or paid out from the winding member,
the belt can be prevented from being wound in a randomly coiled state or
particularly can be wound onto the winding member in a good posture at all
15 times, thus preventing possible breakage resulting from the random coil of
the
belt.
Besides, since the belt guide, which is supported in such a slidable
manner as to allow the winding of the belt around the winding member, is slid
relative to the side plates in response to changes in circle diameter of the
belt
ao wound around the winding member, the belt guided by the belt guide can be
smoothly wound on or unwound from the winding member while twist in the belt
can be surely prevented by the belt guide.
Preferably, the belt hoist includes a loose belt sensor for detecting
looseness in a part of the bE:lt to be guided which is arranged on a moving
path
as along which the part of the belt to be guided into the belt guide portion
moves.
With this construction including the loose belt sensor, the loose belt sensor
works when the belt paid out loses its tension, due to a hook at the free end
of
the belt being in contact with the ground or being caught on an obstacle in
the
course of the unwinding of the belt or any other reason, and rotation of the
3 o winding member can be stopped immediately in accordance with the
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detected result of the loose belt sensor. Thus, the random coil of the belt
resulting from the winding member being rotated in the state that the belt
being
paid out has lost in its tension can be prevented. Further, a reverse winding
of
the belt resulting from the winding member being kept on rotating even after
the
wound belt is paid out entirely can also be prevented.
Further, it is advantageous that one of the belt guide and the side plates
is provided with engaging projections and the other of the belt guide and the
side plates is provided with guide slits engageable with the engaging
projections and extending at least from an inner position at which the belt of
a
minimum circle diameter hangs down to an outer position at which the belt of a
maximum circle diameter hangs down.
This construction including the engaging projections and the guide slits
allows the belt guide to well slide in a standard range from the inner
position to
the outer position in response to changes in circle diameter of the belt. This
provides the result that whenever wound or unwound, the belt is put into place
to be vertically hung down from the winding member, and thereby the belt guide
can be effectively escaped from load applied from a hanging heavy load. This
enables the durability of the belt guide to be enhanced increasingly and also
enables frictional resistance between the belt guide and the belt to be
reduced
increasingly, thus providing the advantage that the winding and unwinding of
the belt onto and from the winding member can be more smoothly performed.
Further, in a case where the guide slit is adapted to have a length somewhat
larger than the abovesaid standard range, that could provide the result that
when the belt is slanted in front or in behind with respect to the side plates
by a
heavy load dragged, the slope of the belt at the belt guide can be made gentle
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by the belt guide moving along the guide slit to an extent beyond the standard
range. This can provide the advantage that a dragging work by use of the belt
can be well done, while twist in the belt is being prevented.
Further, it is preferable in this case that the engaging projections are
shaped into a non-circular form so that the belt guide is non-rotatable
relative to
the side plates.
This allows the belt guide to be slid without being rotated relative to the
side plates. By virtue of this, a possible accident that the belt guide may be
rotated to cause the belt to bulge between the belt guide and the winding
member when the belt is paid out in a nearly unloaded state in an unwinding
direction by a driving force applied from the winding member side can be
prevented from happening, to ensure a smoothly paying out of the belt.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the accompanying
drawings wherein:
Fig. 1 is a vertically sectioned, side view of the belt hoist according to the
invention;
Fig. 2 is a partly cutaway rear view of the same;
Fig. 3 is a front view of part of a detection switch; .
Fig. 4 is a side view of Fig. 3;
Fig. 5 is a partly omitted front view of a belt guide and a loose belt sensor;
Fig. 6 is a sectional view taken on line X-X of Fig. 5;
Fig. 7 is a sectional view taken on line Y-Y of Fig. 5;
Fig. 8 is a partly omitted plan view of the belt hoist; and
Fig. 9 is a rear view of the entire structure of the belt hoist.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the accompanying drawing figures, an example of the
preferred embodiment of the invention is described below. It is to be
understood, however, that the scope of the invention is by no means limited to
the illustrated embodiment.
A belt hoist shown in Figs. 8 and 9 is provided with a pair of spaced apart,
opposite first and second side plates 1 A, 1 B; a normal and reverse rotation
motor 2 serving as drive means, arranged at an outside of the first side plate
1A
and covered with a cover 2A; and a reduction gear mechanism 3 including an
over-loading prevent mechanism 3B and a mechanical brake 3C, arranged at
an outside of the second side plate 1 B and covered with a cover 3A.
Further, a cylindrical winding member 5, around which a flat belt 4 fitting a
hook 40 at the utmost end portion thereof is wound and which is associated
with the reduction gear mechanism 3, is rotatably supported via bearing means
between the side plates 1A, 1 B. In the inside of the winding member 5, a
drive
shaft 31 having a first gear of the reduction gear mechanism 3 is rotatably
supported via bearings. The drive shaft 31 is connected with a motor shaft 21
extending from the motor 2 at one end thereof so as to be associated in
operation therewith so that the winding member 5 can be rotated by drive of
the
motor 2 in the normal direction or in the reverse direction through the motor
shaft 21, the drive shaft 31 and the reduction gear mechanism 3.
The winding member 5 is rotated in the normal direction by the motor 2 to
wind the belt 4 around the winding member 5 so as to hoist up a heavy load
through the belt 4 or is rotated in the reverse direction to pay out the belt
4 from
the winding member 5 so as to hoist down the heavy load through the belt 4
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In the illustrated embodiment, a pair of disc-like flanges 50, 50 are fitted
to the winding member 5 at the both,lengthwise ends thereof, and the belt 4 is
wound onto the periphery of the winding member 5 between the pair of flanges
50. Further, as shown in Fig. 9, a retaining fixture 1 C of a hook is fixed
between the side plates 1 A, 1 B at the top portion thereof, and a control
unit 1 D
for controlling the winding member 5 to rotate in the normal direction or in
the
reverse direction is connected with the cover 3A.
As shown in the embodiment of Figs. 1 and 2, the abovesaid belt hoist
includes a random coil preventing member 6, swingably supported on a pivot
60 between the first and second side plates 1A, 1 B at a radially outward
position of the winding member 5, for normally pressing the belt 4 against the
periphery of the winding member 5 to prevent random coil of the belt 4; and a
control means 7 for controlling the drive of the motor 2 by swinging motion of
the random coil preventing member 6 in response to changes in circle diameter
of the belt 4 wound around the winding member 5.
The random coil preventing member 6 comprises a pair of spaced apart,
opposite arms 61, 61 which are mounted on the pivot 60 rotatably supported
between the first and second side plates 1A, 1 B; a rotary element 62 in the
form
of a roller which is rotatably supported to the arms 61 at the front end
portion
thereof via bearing means and is contactable with the belt 4; and a biasing
spring 63 for biasing the arms 61 to the outer periphery of the winding member
5 so that the rotary element 62 can be always pressed against the belt 4. In
the Fig. 1 embodiment, the biasing spring 63 is in the form of a coiled spring
having a coiled portion 63a and spring legs 63b extending tangentially from
both ends of the coiled portion 63a. With the spring legs 63b rested on the
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arms 61 and a rod 1 E extending between the side plates 1 A, 1 B,
respectively,
the rotary element 62 is always pressed against the belt 4 wound around the
winding member 5 through the arms 61.
The control means 7 is arranged in the following way, as shown in Figs. 2,
3 and 4. One lengthwise end portion 60a of the pivot 60 is projected outward
from the side plate 1 A. First and second protrusions 71, 72, each being
formed by protruding one radial end portion of a boss having a fitting bore
outward in generally semicircle, are arranged on the projected end portion 60a
with a specified phase difference in the circumferential direction and are
secured thereto with screws so as to be changeable in position. At positions
near the projected end portion 60a at the side plate 1 A and on swinging paths
along which the first and second protrusion 71, 72 movable in response to the
turning of the pivot 60 are swung, first and second detection switches 73, 74
are so arranged as to be adjustable in position, respectively. As depicted in
a
two-dot chain line in Fig. 1, the first detection switch 73, which is formed
by a
limit switch and the like, is brought into contact with an edge of the first
protrusion 71 to stop the drive of the motor 2 when length of the belt 4 wound
around the winding member 5 decreases with the unwinding of the belt 4 and
circle diameter of the belt 4 decreases below a specified circle diameter. As
depicted in a solid line in the same figure, the second detection switch 74,
which is formed by a limit switch and the like, is brought into contact with
an
edge of the second protrusion 72 to stop the drive of the motor 2 when the
length of the belt 4 wound around the winding member 5 increases with the
winding of the belt 4 and the circle diameter of the belt 4 increases over a
specified circle diameter. In the illustrated embodiment, at the outside of
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side plate 1 A, a cover 1 F for covering the protrusions 71, 72 and the
detection
switches 73, 74 is detachably fitted to the side plate 1A with fastening
screws.
Next, operation of the random coil preventing member 6 effected by the
abovesaid construction will be described below. When the motor 2 drives the
winding member 5 to rotate so as to wind up and down the belt 4 wound around
the winding member 5, the belt 4 is kept on being pressed by the rotary
element
62 of the random coil preventing member 6 on biasing force of the coiled
spring
63, so that although the circle diameter of the belt 4 on the winding member 5
varies as the belt 4 is wound up and down, the rotary element 62 is moved
toward the belt 4 in response to the variation in the circle diameter. Thus,
the
belt 4 is prevented from being twisted by the rotary element 62 no matter what
circle diameter is, and thereby the belt 4 can be wound on the winding member
5 in a proper posture at all times without being twisted.
As depicted in a two-dot chain line in Fig. 1, when length of the belt 4
wound around the winding member 5 decreases with the lowering of the belt 4
and circle diameter of the belt 4 decreases below a specified circle diameter,
the rotary element 62 is moved inward by the coiled spring 63 in response to
the decreasing circle diameter, to drive the pivot 60 to rotate via the arms
61.
With the rotation of the pivot 60, the first protrusion 71 mounted on the
pivot 60
actuates the first detection switch 73 to stop the drive of the motor 2. On
the
other hand, as depicted in a solid line in the same figure, when the length of
the
belt 4 wound around the winding member 5 increases with the winding of the
belt 4 and the circle diameter of the belt 4 increases over a specified circle
diameter, the rotary element 62 is moved outward in response to the increasing
circle diameter to drive the pivot 60 to rotate. With the rotation of the
pivot 60,
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the second protrusion 72 mounted on the pivot 60 actuates the second
detection switch 74 to stop the drive of the motor 2. The motor 2 is kept on
being driven to wind or unwind the belt 4 until the protrusions 71, 72 are
brought into contact with the related detection switches 73, 74.
As mentioned above, since the drive of the motor 2 is stopped via the
protrusions 71, 71 and the detection switches 73, 74 when the circle diameter
of the belt 4 increases over or decreases below a specified diameter, both of
the overwinding and the over-unwinding of the belt 4 and the resulting
breakage of the components of the hoist can be prevented. Besides, since
the prevention of the overwinding and over-unwinding of the belt 4 is effected
through the use of the random coil preventing member 6 whose movement
drives the protrusions 71, 72 to actuate the detection switches 73, 74 to
control
the drive of the motor 2, reduction in parts count and simplification in
structure
can be achieved.
Moreover, with the arrangement in which the first and second protrusions
71, 72 are fixed to the projected end portion 60a of the pivot 60 which is
projected outward from the side plate 1 A and the detection switches 73, 74 to
be actuated by means of the protrusions 71, 72 are arranged at positions close
to the projected end portion 60a at the outside of the side plate 1 A, any of
the
protrusions and switches are not an obstruct to the swinging motion of the
random coil preventing member 6. Also, such an arrangement has no bad
effect on the winding and unwinding of the belt 4 on and from the winding
member 5 with which the random coil preventing member 6 is always contacted.
Thus, both of the winding and unwinding of the belt 4 on and from the winding
member 5 and the random coil prevention of the belt 4 effected by the random
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coil preventing member 6 can be well accomplished. In addition to this, the
arrangement can also provide the advantage that maintenance of the detection
switches 73, 74 can be easily made without affecting on the random coil
preventing member 6 and the winding and unwinding of the belt 4. Further,
the combination of the protrusions 71, 72 with the detection switches 73, 74
enables the controlling means 7 to be simplified in structure and also ensures
the controlling of drive of the motor 2.
Further, in the Fig. 1 embodiment, a recess 51 is formed on a part of the
periphery of the winding member 5 and an end portion of the belt 4 to be fixed
is
fixed in the recess 51 via a belt holder 52 and fastening screws 53.
In the aforesaid embodiment in which there are provided the first and
second protrusions 71, 72 and the first and second detection switches 73, 74,
one of the two protrusions 71, 72 and one of the two detection switches 73, 74
may only be provided by omitting the others.
Further, the random coil preventing member 6 in the aforesaid
embodiment may alternatively be provided to be movable in a radial direction
of
the winding member 5 against a biasing spring, rather than to be swingable, so
as to always press the rotary element 62 against the belt 4 wound around the
winding member 5.
Further, in the illustrated embodiment, a belt guide 8 having a belt guide
portion 80, which allows the belt 4 to be guided to freely pass with being
prevented from being twisted, is supported between the side plates 1 A, 1 B at
a
position on a moving path along which the belt 4 moves toward or from the
winding member 5. The belt guide 8 is arranged so slidably as to allow the
belt 4 to be wound onto the winding member 5.
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Specifically, as shown in the embodiment of Figs. 2 and 5-7, the belt
guide 8 is provided, at both sides thereof opposite to the side plates 1A, 1B,
with engaging projections 81, 81 having a rectangular cross section and
extending outward. The side plates 1A, 1 B are provided with guide slits 82,
82
in which the engaging projections 81, 81 are slidably inserted and which at
least extends within a standard range from an inner position at which the belt
of
a minimum circle diameter hangs down to an outer position at which the belt of
a maximum circle diameter hangs down.
In the illustrated embodiment, each of the guide slits 82 is in the form of
an elongate slot which extends horizontally to intersect the belt 4 hung down
vertically from the winding member 5. When the belt 4 is wound onto or
unwound from the winding member 5, the engaging projections 81 is moved
along the elongate slots to drive the belt guide 8 to be horizontally slid in
the
standard range between the inner position and the outer position, thereby
allowing the belt 4 to be wound on or unwound from the winding member 5 with
being guided by the belt guide 8.
The guide slits 82 are formed of positions near lower edge portions of the
side plates 1A, 1 B supporting the winding member 5 at the center portion
thereof so that the belt guide 8 can be supported to the guide slits 82 via
the
engaging projections 81 with its lower edge portion being substantially in
alignment with the lower edge portions of the side plates 1A, 1B. With this
arrangement, the belt 4 guided by the belt guide portion 80 of the belt guide
8
can be prevented from being brought into direct contact with components of the
hoist such as the side plates 1 A, 1 B to be damaged at the time of winding or
unwinding of the belt. In particular, when a heavy load is dragged through the
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belt 4, the belt 4 is often slanted rightwards or leftwards with respect to a
direction for the side plates 1A, 1 B to be vertically hung down, but can
nevertheless be protected from direct contact with the side plates 1 A, 1 B to
be
surely prevented from being damaged.
Further, as shown in Figs. 5-7, the belt guide 8 is so structured that a
guide plate 8D is connected to one side of a body 8A having at its opposite
ends the engaging projections 81, 81 by two opposing screws 8C, with a spacer
8B interposed between the guide plate 8D and the one side of the body 8A.
The belt guide portion 80 is defined between the guide plate 8D and the body
8A.
The body 8A has an accommodating space 84 closed by a cover plate 83
at its rear surface at the opposite side to the belt guide portion 80. In the
accommodating space 84, a loose belt sensor 9 for detecting looseness in a
portion 4A of the belt 4 to be guided into the belt guide portion 80 and a
controller~10 of a limit switch which is turned ON by the action of the loose
belt
sensor 9 to stop the drive of the motor 2 are secured.
The loose belt sensor 9 comprises a freely rotatable roller 91 which is
located on the moving path of the portion 4A of the belt to be guided and is
contactable with the portion 4A of the belt which is under tension; and a
roller
carrier 92 for supporting the roller 91 in such a manner as to freely move
within
a specified range in a thickness direction of the portion 4A of the belt to be
guided. The roller carrier 92 is supported on the body 8A via two opposing
horizontal shafts 93, 93 so as to be freely swingable on its hooking portions
94.
Between the roller carrier 92 and free ends of the horizontal shafts 93 are
interposed elastic members 95 of coiled springs which bias the roller carrier
92
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in a direction in which the roller 91 is always contacted with the portion 4A
of
the belt to be guided.
When the portion 4A of the belt to be guided is under tension as depicted
in a chain line in Figs. 1 and 6, the roller 91 is contacted with the portion
4A of
the belt to be guided, and the roller carrier 92 is swung against the elastic
member 95, so that the controller 10 is OFF. When the portion 4A of the belt
to be guided which is under tension is loosened as depicted in a two-dotted
chain line in Figs. 1 and 7, the roller carrier 92 biased by the elastic
member 95
is swung on the hooking portions 94 and is brought into full contact with a
rear
surface of the body 8A. This brings the controller switching ON to stop the
drive of the motor 2 electrically connected to the controller 10.
Thus, the belt 4 inserted into the rectangular hole-like belt guide portion
80 at the belt guide 8 is guided by the belt guide portion 80 at its both
widthwise
edges so as to be prevented from breakage resulting from its directly
contacting with components of the hoist such as the side plates 1 A, 1 B.
Further, each of the engaging projections 81 is in the form of a square
pole whose side is slightly smaller than a breadth of the guide slit 82 so as
to be
movable along but non-rotatable with respect to the guide slit 82. By the
engaging projections 81 slidably inserted in the elongate slots, the belt
guide 8
is rendered non-rotatable with respect to the side plates 1 A, 1 B. This can
provide the result that undesirableness that the belt guide 8 is rotated to
cause
the belt 4 to bulge between the belt guide 8 and the winding member 5 when
the winding member 5 is rotated in an unwinding direction to pay out the belt
4
with nearly unloaded can be effectively prevented and a smoothly paying out of
the belt can be ensured. It is noted that the engaging projections 81 may be
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formed into hexagon or non-circular e.g. oval, in addition to rectangular in
cross
section.
Next, operation of this constructed belt guide 8 will be described below.
When wound on or unwound from the winding member 5, the belt 4 is freely
passed through the belt guide portion 80 of the belt guide 8. Thus, the belt 4
is wound on or unwound from the winding member 5 with being guided by the
belt guide 8 and thus is surely prevented from being taken up in a twisted
state
or in a randomly coiled state. This enables the belt 4 to be wound on the
winding member 5 in a proper posture at all times, so that the belt 4 is
prevented from breakage resulting from its being randomly coiled.
Besides, the belt guide 8 is provided at its both sides with the engaging
projections 81, 81, and the side plates 1 A, 1 B are provided with the guide
slits
82, 82 which extend horizontally intersecting the belt 4 hanging down
vertically
from the winding member 5 and in which the engaging projections 81 are
inserted. When the belt 4 is wound on or unwound from the winding member
5, the belt guide 8 is horizontally slid in the standard range from its inner
position to its outer position in response to changes in circle diameter of
the
belt 4 around the winding member 5. This constructed belt guide 8 enables
twist in the belt 4 to be surely prevented and also allows a smooth winding
and
unwinding of the belt 4 onto and from the winding member 5.
Here, the guide slits 82 in the Fig. 1 embodiment are each adapted to
have a length somewhat larger than the standard range between the inner
position and the outer position. This can provide the result that when the
belt
is slanted in front or in behind with respect to the side plates 1A, 1 B by a
heavy
load dragged, for example, the slope of the belt 4 at the belt guide 8 can be
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made gentle by moving the belt guide 8 along the guide slits 82 to an extent
beyond the standard range. By virtue of this, a dragging work can be done
well by use of the belt 4 while the belt 4 is being prevented from being
twisted.
Also, when the belt 4 being unwound is loosened at its portion 4A to be
guided due to the hook 40 being contacted with the ground or being caught on
an obstacle in the course of the unwinding of the belt or any other reason,
the
roller carrier 92 is swung on the hooking portions 94 and is brought into full
contact with the rear surface of the body 8A, bringing the controller 10
switching ON to stop the drive of the motor 2. Thus, the random coil of the
belt
4 on the periphery of the winding member resulting from the winding member 5
being rotated in the state that the unwound belt 4 is not under tension can be
prevented. Further, the reverse winding of the belt resulting from the winding
member 5 being kept on rotating even after the wound belt 4 is paid out
entirely
can also be prevented.
In the embodiment described above, the guide slits 82 for guiding the
engaging projections 81 thereinto are in the form of the elongate slots formed
in
the side plates 1 A, 1 B, but need not necessarily be limited to the elongate
slots.
The guide slits 82 may be in the form of grooves which extend along a sliding
direction of the engaging projections 81 and in which the engaging projections
81 are slidable in the specified range mentioned above. In addition, the
direction for the guide slits 82 to extend intersecting the belt 4 hanging
down
vertically from the winding member 5 may not necessarily be limited to the
regular horizontal direction. The guide slits 82 may be slightly slanted with
respect to the horizontal direction. In short, it is essential that the guide
slits
82 are so formed that the belt guide 8 can be slide in response to increase or
18
CA 02304440 2000-04-13
decrease in circle diameter of the belt 4 wound around the winding member 5
so that the belt 4 can be wound or unwound smoothly and easily without
hindering the winding or unwinding of the belt on or from the winding member
5.
Further, in the illustrated embodiment, the engaging projections 81 and
the guide slits 82 in which the engaging projections 81 are inserted may be
provided at the side plates 1A, 1 B and at the belt guide 8, respectively.
Also, instead of the motor 2 used in the above embodiment, a hand-
operated lever or chain may be used as the drive means for driving the winding
member 5, as in a lever type chain block or a hand chain type chain block.
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