Information
-
Patent Grant
-
6224039
-
Patent Number
6,224,039
-
Date Filed
Tuesday, October 19, 199924 years ago
-
Date Issued
Tuesday, May 1, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Marcou; George T.
- Kilpatrick Stockton LLP
-
CPC
-
US Classifications
Field of Search
US
- 254 352
- 254 353
- 254 346
- 254 365
- 254 369
- 254 376
- 254 372
-
International Classifications
-
Abstract
A chain block which can ensure free rotation of a hand wheel when the hand wheel is rotated in a hoisting direction in the state in which an overload protection mechanism is in operation and also can ensure the lowering of a load when the hand wheel is rotated in a lowering direction. The chain block includes an one-way mechanism that permits the hand wheel to freely rotate in the hoisting direction with respect to the first hub of the hand wheel and restricts the hand wheel freely rotating in the lowering direction. The one-way mechanism is composed of a spring and a pin received in a recess and a receiving portion formed in the inner periphery of the boss of the hand wheel and forming therein a slanted surface for guiding the pin received in the receiving portion to the inner periphery of the boss when the hand wheel is rotated in the hoisting direction and a retaining surface for retaining the pin in the inside of the receiving portion when the hand wheel is rotated in the lowering direction.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chain block and, more particularly, to a hand operated chain block wherein a load sheave is rotated to wind up and down a load chain passing over the load sheave by the operation of a hand chain passing over a hand wheel.
2. Description of the Prior Art
In general, hand operated chain blocks of this type comprise a load sheave supported between two opposed side plates via bearings; a hand wheel disposed at the outside of one side plate to drive the load sheave through a drive shaft and a reduction gear mechanism; and a transmission mechanism having a mechanical brake which is interposed between the hand wheel and the load sheave to apply a given brake and are so structured that a load suspended from a hook of the load chain passing over the load sheave can be hoisted up and lowered down by the operation of a hand chain passing over the hand wheel.
Of these known chain blocks, some are provided with an overload protection mechanism that permits the hand wheel to freely rotate in the hoisting direction when a load in excess of a rated load of the chain block is applied to the load sheave, for preventing the hoist of the load more than the rated load.
The overload protection mechanism comprises, for example, a hub member threadedly mounted on the drive shaft and supporting thereon the hand wheel in a freely rotatable manner; a load setting mechanism, arranged at an axially outside end portion of the hub member, for setting a rated load; and two lining plates interposed in a freely rotatable manner between the hub member and the hand wheel and between the hand wheel and the load setting mechanism, respectively. The overload protection mechanism is so structured that when the hand wheel is rotated in the hoisting direction in the state in which a load more than a rated load as is preset by the load setting mechanism pressing the lining plates is being applied, slippage of the hand wheel can be caused between the two lining plates placed at both sides of the hand wheel to permit free rotation of the hand wheel with respect to the hub member.
On the other hand, for example when the overload protection mechanism is put into action in the hoist of the load by the application of a load more than the rated load, the hand wheel is held slipped between the two lining plates placed at both sides thereof, and as such cannot permit the lowering of the load. For permitting the lowering of the load in such a situation, the hub member is provided, in an outer periphery thereof, with a recessed portion in which a pin and a biasing spring for biasing the pin radially outwardly are housed and also a boss of the hand wheel is provided, in an inner periphery thereof, with a receiving portion that can permit the pin to be retained therein only when the hand wheel is rotated in the lowering direction, whereby an one-way mechanism that permits free rotation of the hand wheel with respect to the hub member only in the hoisting direction and restricts the free rotation of the hand wheel in the lowering direction is formed so that the lowering of the load can be permitted even when a load more than the rated load is applied.
With this arrangement, when the hand wheel is rotated in the lowering direction in the state in which it is being slipped between the two lining plates placed at the both sides of the hand wheel by the action of the overload protection mechanism, the pin is smoothly received in the receiving portion but is sometimes caught in the receiving portion even when the hand wheel is rotated in the hoisting direction, depending on the form of the receiving portion. As a result of this, despite the load being more than the rated load, the load is sometimes hoisted in an unstable state, or the pin and the receiving portion are sometimes damaged. Also, there is presented a disadvantage that the hand wheel, when rotated, may rattle to cause damage to the hub member and the hand wheel. In the hand operated chain block of this type, in particular, even a little pulling of the hand chain may cause the hand wheel to rotate a couple of turns, and as such will give increased opportunities of the pin and the receiving portion to confront each other, thus significantly expanding the influence of the disadvantages above. Further, when it comes to a small-sized chain block having the hand wheel of a small diameter, even the little pulling of the hand chain will give further increased opportunities of the pin and the receiving portion to confront each other, thus further significantly expanding the influence.
SUMMARY OF THE INVENTION
To solve the problems mentioned above, the present invention has been made. It is the object of the present invention is to provide a chain block that can ensure free rotation of a hand wheel when the hand wheel is rotated in a hoisting direction in the state in which an overload protection mechanism is in operation and also can ensure the lowering of a load when the hand wheel is rotated in a lowering direction.
The present invention provides a novel chain block comprising a load sheave with which a load chain is engageable; a hand wheel with which a hand chain is engageable; a transmission mechanism including a mechanical brake interposed between the hand wheel and the load sheave; an overload protection mechanism that supports the hand wheel and permits the hand wheel to freely rotate in a hoisting direction when a load more than a rated load is applied to the load sheave; and a drive shaft, passed through the load sheave, the transmission mechanism and the overload protection mechanism, to transmit drive applied from the hand wheel to the load sheave, wherein the overload protection mechanism includes a hub member threadedly engaged with the drive shaft and supporting thereon the hand wheel in a freely rotatable manner; and an one-way mechanism that permits the hand wheel to freely rotate in a hoisting direction with respect to the hub member and restricts the hand wheel freely rotating in a lowering direction; wherein the one-way mechanism includes a recess formed in an outer periphery of the hub member; an engaging member provided in the recess and normally biased radially outwardly; and a concave receiving portion, opening in an inner periphery of a boss of the hand wheel, to receive the engaging member therein; and wherein the receiving portion includes a slanted surface extended obliquely to guide the engaging member received in the receiving portion to the inner periphery of the boss of the hand wheel when the hand wheel is rotated in the hoisting direction; and a retaining surface, extended substantially along a radial direction of the inner periphery of the boss, to permit the engaging member received in the receiving portion to be retained in an inside of the receiving portion when the hand wheel is rotated in a lowering direction.
With this arrangement, when a load more than a rated load applied to the load sheave is tried to be hoisted by rotating the hand wheel in the hoisting direction, the hand wheel is permitted to freely rotate with respect to the hub member threadedly engaged with the drive shaft. Thus, the hoist of any load more than the rated load of the chain block is prevented. During the free rotation of the hand wheel with respect to the hub member, every time the engaging member of the one-way mechanism faces the receiving portions formed in the inner periphery of the boss of the hand wheel, the engaging member which is normally biased radially outwardly or toward the inner periphery of the boss of the hand wheel is received in the receiving portions, while on the other hand, the as-received engaging member is smoothly guided again to the inner periphery of the boss of the hand wheel along the slanted surface formed in each of the receiving portions.
This can produce the results that a possible problem that the engaging member may be caught in the receiving portion so that a load more than a rated load may be hoisted in an unstable state or a possible damage of the engaging member and the receiving portion can be minimized. Also, the rattling of the hand wheel that may be caused when rotated can be minimized and a possible damage to the hub member and the hand wheel can be minimized.
On the other hand, for example, when the overload protection mechanism is put into action in the hoist of a load by the application of load more than a rated load, the hand wheel can be restricted freely rotating in the lowering direction with respect to the hub member by the engaging member of the one-way mechanism being received in the receiving portion. This can permit the lowering of even a load more than the rated load. At that time, the engaging member received in the receiving portion is well retained by the retaining surface formed in the receiving portion.
This arrangement that enables the engaging member received in the receiving portion to be well retained by the retaining surface formed in the receiving portion when the hand wheel is rotated in the lowering direction can provide the result that the free rotation of the hand wheel with respect to the hub member can reliably be restricted and thereby the lowering of even a load more than a rated load can be ensured.
According to this invention, it is preferable that the slanted surface formed in the receiving portion is extended along a tangential direction to the inner periphery of the hand wheel and also is smoothed out at a boundary between the inner periphery of the boss of the hand wheel and the slanted surface.
With this arrangement, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, every time the engaging member received in the receiving portion faces the receiving portion, the engaging member is smoothly guided again to the inner periphery of the boss of the hand wheel along the tangential direction to the inner periphery of the hand wheel and along the slanted surface smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel. On the other hand, when the hand wheel is rotated in the lowering direction, the engaging member is smoothly received into the receiving portion along the tangential direction to the inner periphery of the hand wheel and along the slanted surface smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel.
In this arrangement, since the slanted surface of the receiving portion is so formed as to extend along the tangential direction to the inner periphery of the hand wheel and is smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, the engaging member received in the receiving portion can be guided smoothly to the inner periphery of the boss of the hand wheel just the way it is, without causing the engaging member received in the receiving portions to rattle. Also, when the hand wheel is rotated in the lowering direction, the engaging member can be received into the receiving portion smoothly without causing the engaging member to rattle.
Thus, for example in a hand operated chain block in which even a little pulling of the hand chain in the hoisting direction causes the hand wheel to rotate with respect to the hub member a couple of turns during which the engaging member confronts the receiving portions several times, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, smooth free rotation of the hand wheel with respect to the hub member can be ensured, while also, when the hand wheel is rotated in the lowering direction, the engaging member can smoothly be received in the receiving portion to ensure the smooth lowering of load.
According to this invention, it is preferable that there are provided receiving portions which are opened in the inner periphery of the hand wheel at positions opposed to each other and of which slanted surfaces are formed to be substantially parallel to each other.
With this arrangement, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, the engaging member is received in each of the receiving portions provided at the opposed positions every time the hand wheel is rotated one turn. Even when the engaging member is received in any of the receiving portions, since the slanted surfaces in the receiving portions are so formed as to be substantially parallel to each other, the engaging member received is guided to the inner periphery of the boss of the hand wheel along the slanted surface under the same condition. On the other hand, when the hand wheel is rotated in the lowering direction, the engaging member is received in any of the receiving portions provided at the opposed positions during one-turn of the hand wheel.
This can provide the result that in the chain block in which even a little pulling of the hand chain causes the hand wheel to rotate a couple of turns, so as to give several opportunities of the engaging member to confront the receiving portions, since the receiving portions are provided at the opposed positions and also the slanted surfaces are so formed as to be substantially parallel with each other, even when the engaging member is given many opportunities to confront the receiving portions, the engaging member is received cliclically in the receiving portions as the hand wheel rotates and is guided to the inner periphery of the boss of the hand wheel along the slanted surfaces under the same condition. Thus, regular operations can be ensured. On the other hand, when the hand wheel is rotated in the lowering direction, since the engaging member is received in any of the receiving portions during one-turn of the hand wheel, the engaging member is brought into engagement in the receiving potion to permit the lowering of load until the hand wheel rotates one turn.
Thus, for example, in a small-sized chain block having the hand wheel having a small diameter in which even a little pulling of the hand chain causes the engaging member to confront the receiving portions many times, good operation of the engaging member and the receiving portions can be ensured and, thus, improved durability and reliability of the one-way mechanism can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described with reference to the accompanying drawings wherein:
FIG. 1
illustrates in longitudinal section a small-sized hand operated chain block as one embodied form of a chain block of the present invention;
FIG. 2
is a side view of a hand wheel of the chain block shown in
FIG. 1
;
FIG. 3
is a front view of the hand wheel shown in
FIG. 2
;
FIG. 4
is a side view of a first hub of the chain block shown in
FIG. 1
;
FIG. 5
is a front view of the first hub shown in
FIG. 2
;
FIG. 6
illustrates in longitudinal section a principal part of one embodied form of a chain block which is not equipped with an overload protection mechanism;
FIG. 7
illustrates in side elevation a principal part of an one-way mechanism; and
FIG. 8
illustrates in side elevation a principal part of the one-way mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the accompanying drawing figures, an example of the preferred embodiment of the invention is described below.
Referring to
FIG. 1
, there is shown a longitudinal section of a small-sized hand operated chain block of one embodiment of the present invention. In the chain block, a load sheave
3
over which a load chain
61
passes in engaging relation is rotatably supported between opposed left and right side plates
1
,
2
via two bearings
4
,
5
.
A drive shaft
6
is inserted in a shaft hole of the load sheave
3
in freely rotatable relation, and a transmission mechanism
10
having a mechanical brake
9
and an overload protection mechanism
8
are supported by the drive shaft
6
at the outside of the right side plate
2
in an inserted state. A hand wheel
7
over which a hand chain
62
passes in an engaging relation is supported in the overload protection mechanism
8
. As will be mentioned later, the drive shaft
6
is substantially the same as a drive shaft used in a chain block which is not equipped with the overload protection mechanism
8
.
The transmission mechanism
10
includes a second hub
11
connected to the drive shaft
6
in a non-rotatable relation (in a threaded connection in FIG.
1
); a third lining plate
17
, an anti-reverse gear
12
; and a fourth lining plate
18
.
The second hub
11
is formed in one piece having a flange portion and a cylindrical portion extending axially therefrom. The anti-reverse gear
12
, the third lining plate
17
and the fourth lining plate
18
are rotatably supported on the cylindrical portion of the second hub
11
in such a manner that the third lining plate
17
is interposed between the anti-reverse gear
12
and a first hub
13
of the overload protection mechanism
8
mentioned later and the fourth lining plate
18
is interposed between the flange portion of the second hub
11
and the anti-reverse gear
12
.
A pawl shaft
14
is provided on the right side plate
2
and an anti-reverse pawl
15
engageable with the anti-reverse gear
12
is swingably pivoted on the pawl shaft
14
. Further, a pawl spring
16
for biasing the anti-reverse pawl
15
toward the anti-reverse gear
12
is provided between the anti-reverse pawl
15
and the right side plate
2
. The mechanical brake
9
of the transmission mechanism
10
is composed of the second hub
11
, the anti-reverse gear
12
, the anti-reverse pawl
15
, the third lining plate
17
and the fourth lining plate
The hand wheel
7
has on the outer periphery side thereof a plurality of pockets
20
for receiving therein chain links of a hand chain
62
and also has on the base side thereof a boss
22
in which a receiving hole
58
for receiving therein the first hub
13
of the overload protection mechanism
8
mentioned later is formed, as shown in
FIGS. 2 and 3
. Formed at both sides of the boss
22
are a second recess
56
and a third recess
57
formed in the recessed form for receiving therein a first lining plate
23
and a second lining plate
24
mentioned later, respectively. The second recess
56
and the third recess
57
are formed in circular, in side configuration, of slightly larger in diameter than the outer diameters of the first lining plate
23
and the second lining plate
24
and formed with a depth substantially equal to a thickness of the first lining plate
23
and the second lining plate
24
.
The overload protection mechanism
8
includes the first hub
13
of a hub member threadedly engaged with the drive shaft
6
, the load setting mechanism
21
for setting a rated load, the first lining plate
23
acting as a brake disc, the second lining plate
24
acting as the brake disc and one-way mechanism
25
that permits free rotation of the hand wheel
7
in the hoisting direction with respect to the first hub
13
and restricts the free rotation of same in the lowering direction, as shown in FIG.
1
.
The first hub
13
is formed in one piece having a flange portion
19
, a large-diameter cylindrical portion
30
extending axially outwardly from the flange portion
19
and a small-diameter cylindrical portion
31
extending axially outwardly from the large-diameter cylindrical portion
30
and being smaller in diameter than the large-diameter cylindrical portion
30
, as shown in
FIGS. 4 and 5
. The small-diameter cylindrical portion
31
has on an end surface thereof a first recess
32
opening in the form of a recessed portion. The first recess
32
is formed in circular, in side configuration, of not less in diameter than a set nut
34
mentioned later and formed with such a depth as to receive at least a part of the set nut
34
. The small-diameter cylindrical portion
31
is externally threaded.
The hand wheel
7
, the first lining plate
23
and the second lining plate
24
are rotatably supported on the large-diameter cylindrical portion
30
of the first hub
13
in such a manner that the first lining plate
23
is interposed between the boss
22
of the hand wheel
7
and a lining keep member
26
of the load setting mechanism
21
mentioned later and the second lining plate
24
is interposed between the flange portion
19
of the first hub
13
and the boss
22
of the hand wheel
7
. As a result of this, the first lining plate
23
and the second lining plate
24
are fitted in the second recess
56
and the third recess
57
formed at the both sides of the boss
22
of the hand wheel
7
, respectively.
The load setting mechanism
21
is composed of the lining keep member
26
, a belleville spring
27
serving as a biasing means, a locking member
28
and a tightening nut
29
. With contacting with the first lining plate
23
, the lining keep member
26
is rotatably supported on the large-diameter cylindrical portion
30
of the first hub
13
, as aforesaid. For biasing the lining keep member
26
toward the first lining plate
23
, the belleville spring
27
is supported on the small-diameter cylindrical portion
31
of the first hub
13
, with contacting with the lining keep member
26
. For adjusting the biasing force of the belleville spring
27
, the tightening nut
29
is threadedly engaged with the small-diameter cylindrical portion
31
of the first hub
13
, with pressing the belleville spring
27
through the locking member
28
.
Thus, when the tightening nut
29
is screwed forward along the small-diameter cylindrical portion
31
of the first hub
13
, the first lining plate
23
, the hand wheel
7
and the second lining plate
24
existing between the tightening nut
29
and the flange portion
19
of the first hub
13
are pressed through the lining keep member
26
by the belleville spring
27
so strongly that even when a heavy load is hoisted, the hand wheel
7
can be prevented from slipping over the first lining plate
23
and the second lining plate
24
, thus permitting the setting of an increased rated load. On the other hand, as the tightening nut
29
is screwed backward along the small-diameter cylindrical portion
31
of the first hub
13
, the pressing force of the belleville spring
27
to the first lining plate
23
, the hand wheel
7
and the second lining plate
24
between the tightening nut
29
and the flange portion
19
of the first hub
13
decreases, so that when a heavy load is hoisted, the hand wheel
7
can be slipped over the first lining plate
23
and the second lining plate
24
, thus permitting the setting of an decreased rated load.
The set nut
34
used as a restricting member is threadedly engaged with an end portion of the drive shaft
6
on which the overload protection mechanism
8
is mounted, with spaced at a predetermined interval from the first hub
13
threadedly mounted on the drive shaft
6
. In the first recess
32
opening in the end surface of the small-diameter cylindrical portion
31
of the first hub
13
, the set nut
34
is fixed to the end portion of the drive shaft
6
by a set pin
59
so that it cannot be moved in the axial direction. The axial movement range of the first hub
13
is restricted by the set nut
34
, with a washer
33
interposed between the set nut
34
and a bottom of the first recess
32
.
On the other hand, the drive shaft
6
is supported by the bearing
35
at the other axial end portion thereof, and the reduction gear mechanism
36
having a plurality of reduction gears is provided between the bearing
35
and the load sheave
3
and at the outside of the left side plate
1
. The reduction gear mechanism
36
is composed of the first gear
37
integrally formed on the axial end portion of the drive shaft
6
, the second gear
38
and the third gear
39
supported on a pair of intermediate shafts and engageable with the first gear
37
(which are not shown and only one of the second gear
38
and the third gear
39
is shown in
FIG. 1
) and the fourth gear
40
connected with an extended portion of the load sheave
3
and engageable with the third gear
39
. The drive from the drive shaft
6
is transmitted from the first gear
37
to the second gear
38
engaged with the first gear and then transmitted to the fourth gear
40
from the intermediate shaft supporting the second gear
38
thereon through the third gear
39
supported on the same intermediate shaft. Thus, the drive from the drive shaft
6
is transmitted to the load sheave
3
at a predetermined reduction ratio.
A gear cover
41
for covering the reduction gear mechanism
36
and a wheel cover
42
, opening at one side thereof, for covering the hand wheel
7
are detachably mounted on the left side plate
1
at the outside thereof and the right side plate
2
at the outside thereof, respectively, with three stay bolts connecting between the left side plate
1
and the right side plate
2
(only two stay bolts
43
,
44
are shown in FIG.
1
). Provided between the right side plate
2
and the hand wheel
7
is a brake cover
45
for covering a circumferential portion of the anti-reverse gear
12
. Further, a chain split
46
is provided between the left side plate
1
and the right side plate
2
at lower portions thereof, and a chain guide
47
for guiding the load chain
61
is provided between the left side plate
1
and the right side plate
2
at upper portions of the load sheave
3
. Provided above the chain guide
47
is an upper hook
48
for suspending the chain block.
According to the illustrated chain block thus structured, the set nut
34
can be fixed in the first recess
32
opening at the small-diameter cylindrical portion
31
of the first hub
13
to share the use of substantially the same drive shaft
6
as the one used in a chain block having the same specification as the illustrated chain block but the overload protection mechanism
8
, such as, for example, the chain block whose principal part is shown in FIG.
6
. This can permit the component sharing between the chain block with the overload protection mechanism
8
and the chain block having the same specification but having no overload protection mechanism, for simplifying the manufacturing operation or process and reducing costs. Especially, even a small-sized chain block whose drive shaft
6
is intended to have a reduced length for size reduction of the entire chain block can share the use of the drive shaft
6
substantially the same as that of the chain block having the same specification but having no overload protection mechanism
8
, so that the effect is particularly significant.
It is noted that the chain block shown in
FIG. 6
has the same specification as the chain block of the embodied form of the invention, except the provision of the overload protection mechanism, and the same members are indicated by the same reference numerals in FIG.
6
. Though not shown in
FIG. 6
, one end portion of the drive shaft
6
is extended through the shaft hole of the load sheave
3
, and the second hub
11
of the transmission mechanism
10
having the mechanical brake
9
is coupled with the drive shaft
6
in such a manner as to be non-rotatable relative thereto. Immediately at the axial outside of the second hub
11
, the boss
22
A of the hand wheel
7
A is threadedly engaged with the drive shaft, instead of the first hub
13
of the overload protection mechanism
8
. Also, the set nut
34
is threadedly engaged with the axial end portion of the drive shaft
6
, with spaced at a predetermined interval from the boss
22
A of the hand wheel
7
A threadedly engaged with the drive shaft
6
. The set nut
34
is fixed to the end portion of the drive shaft
6
by the set pin
59
so that it cannot be moved in the axial direction. The axial movement of the hand wheel
7
A is restricted by the set nut
34
, with a check washer
60
splined to the drive shaft
6
between the set nut
34
and the boss
22
A of the hand wheel
7
A.
According to the chain block of this embodied form of the invention, the first lining plate
23
and the second lining plate
24
of the overload protection mechanism
8
are received in the second recess
56
and the third recess
57
formed in the boss
22
of the hand wheel
7
, respectively, so that the overload protection mechanism
8
can be reduced in size in the axial direction thereof by an amount corresponding to the thickness of the first and second lining plates
23
,
24
. Thus, combination of the arrangement of the set nut
34
being fixed in the first recess
32
opening at the small-diameter cylindrical portion
31
of the first hub
13
with the arrangement of the first and second lining plates
23
,
24
being received in the second and third recesses
56
,
57
can produce the advantageous effect that even a small-sized chain block having a considerably shortened drive shaft
6
can share the use of the drive shaft
6
substantially the same as that of the chain block having the same specification but having no overload protection mechanism
8
.
For provision of the overload protection mechanism
8
combined with the hand wheel
7
, it is necessary that the hand wheel
7
be rotatably supported on the first hub
13
. Accordingly, the hand wheel separate from the hand wheel
7
A of the chain block with no overload protection mechanism
8
must be prepared. The specific arrangement that the first recess
32
, the second recess
56
and the third recess
57
are formed in only the part of the first hub
13
and the hand wheel
7
enables the sharing of the drive shaft
6
substantially the same as that of the chain block having the same specification but having no overload protection mechanism
8
. Thus, the component sharing of the chain block, e.g. a small-sized one mentioned above, is intended by the manufacturing of minimum component counts and thereby significant simplification of the manufacturing operation or process of such a small-sized chain block and cost reduction are intended.
Further, since the first lining plate
23
and the second lining plate
24
are received in the second recess
56
and the third recess
57
formed in the boss
22
of the hand wheel
7
, the first lining plate
23
and the second lining plate
24
are prevented from being out of position with respect to the boss
22
of the hand wheel
7
. Therefore, a reliable braking of the hand wheel
7
can be achieved by the first and second lining plates
23
,
24
to provide improved reliability of the overload protection mechanism
8
.
According to the chain block of embodied form of the invention, in particular, since the first lining plate
23
and the second lining plate
24
placed at the opposite sides of the hand wheel
7
are received in the second recess
56
and the third recess
57
formed in the boss
22
of the hand wheel
7
at the both sides thereof, respectively, the overload protection mechanism
8
can be reduced in size in the axial direction thereof by an amount corresponding to the thickness of the first and second lining plates
23
,
24
. This can produce the result that even a small-sized chain block having a shortened drive shaft
6
can share the use of the drive shaft
6
substantially the same as that of the chain block having the same specification but having no overload protection mechanism
8
. Also, since the hand wheel
7
can reliably be braked by both of the first lining plate
23
and the second lining plate
24
, improved reliability of the overload protection mechanism
8
is yielded.
Next, the usage of the thus-constructed chain block thus constructed of the embodied form of the invention will be described.
First, description will be given on the hoist of or the lowering of a load which is less than a rated load preset by the load setting mechanism
21
. The load is suspended from a lower hook (not shown) provided at the end of the load chain
61
. When the hand chain
62
is operated to rotate the hand wheel
7
in the hoisting direction for the hoist of the load, the first hub
13
of the overload protection mechanism
8
which is in the state of rotatable with the hand wheel
7
is screwed forward along the drive shaft
6
to press the third lining plate
17
of the transmission mechanism
10
, and thereby the drive shaft
6
is driven in the normal rotation direction through the second hub
11
of the transmission mechanism
10
coupled with the drive shaft
6
in such a manner as to be non-rotatable relative thereto. When the drive shaft
6
is driven, the drive is transmitted to the load sheave
3
through the reduction gear mechanism
36
and thereby the load sheave
3
is rotated in the direction for the load to be hoisted up. As a result of this, the load suspended from the lower hook provided at the end of the load chain
61
running over the load sheave
3
is hoisted up. The suspended load is kept in its hoisted position by the operation of the mechanical brake
9
or by the engagement of the anti-reverse pawl
15
with the anti-reverse gear
12
.
When the hand chain
62
is operated to rotate the hand wheel
7
in the lowering direction for the lowering of the load, the first hub
13
of the overload protection mechanism
8
which is in the state of rotatable with the hand wheel
7
is screwed backward along the drive shaft
6
. Then, the engagement between the flange portion
19
of the first hub
13
and the third lining plate
17
of the transmission mechanism
10
is disengaged to release the mechanical brake
9
, and as such can allow the drive shaft
6
to freely rotate. As a result of this, the drive shaft
6
is rotated in the reverse rotation direction under the weight of load, so that the load is lowered down. On the other hand, the reverse rotation of the drive shaft
6
causes the first hub
13
of the overload protection mechanism
8
threadedly engaged with the drive shaft
6
to be screwed forward again along the drive shaft
6
, to press the third lining plate
17
of the transmission mechanism
10
. As a result of this, the mechanical brake
9
acts again to prevent the rotation of the drive shaft
6
in the reverse rotation direction. Thus, when the load is lowered down, the mechanical brake
9
is made active and inactive alternately so that the load sheave
3
can be allowed to rotate in the lowering direction little by little. The suspended load is lowered down in this manner.
When a load more than a rated load as preset by the load setting mechanism
21
is tried to be hoisted by the operation of the hand chain
62
to rotate the hand wheel
7
in the hoisting direction, slippage of the hand wheel
7
between the first lining plate
23
and the second lining plate
24
is caused by the action of the overload protection mechanism
8
to permit free rotation of the hand wheel
7
with respect to the first hub
13
. Thus, the hoist of any load more than the rated load of the chain block is prevented.
On the other hand, for example when the overload protection mechanism
8
is put into action in the hoist of a load more than the rated load, the hand wheel
7
is held slipped between the first lining plate
23
and the second lining plate
24
, and as such cannot permit the lowering of the load. In this situation, the hand wheel
7
can be restricted by the one-way mechanism
25
freely rotating in the lowering direction with respect to the first hub
13
to permit the lowering of even the load more than the rated load.
Referring now to
FIGS. 7 and 8
, there are shown sectional views of a principal part of the one-way mechanism
25
for illustration thereof. In the following, the description on the one-way mechanism
25
will be given with reference to
FIGS. 2
,
7
and
8
.
In
FIG. 2
, the one-way mechanism
25
is composed of a recess
49
formed in the outer periphery of the large-diameter cylindrical portion
30
of the first hub
13
, a pin
50
of an engaging member provided in the recess
49
, a spring
51
of an biasing means for biasing the pin
50
radially outwardly, and concave receiving portions
52
opening in the inner periphery of the receiving hole
58
in the boss
22
of the hand wheel
7
to receive the pin
50
therein.
The recess
49
is formed in rectangle in side configuration, opening from the outer periphery of the large-diameter cylindrical portion
30
into the radial inside of the same. The spring
51
is inserted in the recess
49
and the column-like pin
50
is disposed at a free end of the spring
51
, such that the pin
50
is biased radially outwardly of the large-diameter cylindrical portion
30
by the biasing force of the spring
51
. On the other hand, two receiving portions
52
are formed in the inner periphery of the boss
22
of the hand wheel
7
at positions that are opposed to each other or shifted from each other at 180°.
The receiving portions
52
are each composed, as shown in
FIGS. 7
,
8
, of a slanted surface
53
, extended obliquely, for guiding the pin
50
received in the receiving portion
52
to the inner periphery of the boss
22
when the hand wheel
7
is rotated in the hoisting direction; a retaining surface
55
, extended substantially along the radial direction of the inner periphery of the boss
22
, for permitting the pin
50
received in the receiving portion
52
to be retained in the inside of the receiving portion
52
when the hand wheel
7
is rotated in the lowering direction; and a flat surface
54
, extending continuously to the slanted surface
53
and the retaining surface
55
, for holding the pin
50
received in the receiving portion
52
.
Each slanted surface
53
is extended along a tangential direction to the inner periphery of the boss
22
of the hand wheel
7
and also is smoothed out at the boundary between the inner periphery of the boss
22
of the hand wheel
7
and the slanted surface
53
. The slanted surfaces
53
of the receiving portions
52
that are located in opposition to each other are formed to be parallel with each other.
According to the one-way mechanism
25
thus constructed, when the hand wheel
7
is rotated in the hoisting direction for the hoist of a load more than a rated load, the hand wheel
7
is freely rotated with respect to the first hub
13
. During this, every time the pin
50
of the one-way mechanism
25
faces the receiving portions
52
formed in the inner periphery of the boss
22
of the hand wheel
7
, the pin
50
which is normally biased radially outwardly or toward the inner periphery of the boss
22
of the hand wheel
7
is received in the receiving portions
52
, while on the other hand, the as-received pin
50
is smoothly guided again to the inner periphery of the boss
22
of the hand wheel
7
along the slanted surface
53
formed in each of the receiving portions
52
(this state is shown in FIG.
7
). Since the pin
50
is smoothly guided again to the inner periphery of the boss
22
of the hand wheel
7
through the slanted surfaces
53
which are each extended along a tangential direction to the inner periphery of the boss
22
of the hand wheel
7
and smoothed out at the boundary between the inner periphery of the boss
22
of the hand wheel
7
and the slanted surface
53
, the pin
50
received in the receiving portions
52
can be guided smoothly to the inner periphery of the boss
22
of the hand wheel
7
just the way it is, without causing the pin
50
received in the receiving portions
52
to rattle.
As a result of this, a possible problem that the pin
50
may be caught in the receiving portion
52
so that a load more than a rated load may be hoisted in an unstable state or a possible damage of the pin
50
and the receiving portion
52
can be minimized. Also, the rattling of the hand wheel
7
that may be caused when rotated can be minimized and a possible damage to the first hub
13
and the hand wheel
7
can be minimized.
On the other hand, for example, even when the overload protection mechanism
8
is put into action in the hoist of a load by the application of load more than a rated load, such that the hand wheel
7
is held slipped between the first lining plate
23
and the second lining plate
24
, the hand wheel
7
can be restricted freely rotating in the lowering direction with respect to the first hub
13
by the pin
50
of the one-way mechanism
25
being received in the receiving portion
52
. This can permit the lowering of even a load more than the rated load. At that time, the pin
50
received in the receiving portion
52
is well retained by the retaining surfaces
55
formed in the receiving portion
52
(this state is shown in FIG.
8
). Thus, the free rotation of the hand wheel
7
with respect to the first hub
13
can be reliably restricted and thereby the lowering of even a load more than a rated load can be ensured.
When the hand wheel
7
is in the state in which it freely rotates in the hoisting direction with respect to the first hub
13
, every time the hand wheel
7
rotates one turn, the pin
50
is received in the receiving portions
52
provided at the opposed positions. Since the receiving portions
52
have the slanted surfaces
53
which are so formed as to be substantially parallel with each other, the pin
50
, even when received in any of the receiving portions
52
, is guided into the inner periphery of the boss
22
of the hand wheel
7
along the slanted surfaces
53
under the same condition. For example, in the hand operated chain block of the embodied form of the invention in which even a little pulling of the hand chain
62
causes the hand wheel
7
to rotate a couple of turns with respect to the first hub
13
, so as to give several opportunities of the pin
50
to confront the receiving portions
52
, since the receiving portions
52
are provided at the opposed positions and also the slanted surfaces
53
are so formed as to be substantially parallel with each other, even when the pin
50
is given many opportunities to confront the receiving portions
52
, the pin
50
is received cliclically in the receiving portions
52
as the hand wheel
7
rotates and is guided to the inner periphery of the boss
22
of the hand wheel
7
along the slanted surface
53
under the same condition. Thus, regular operations can be ensured, and as such can produce improved durability and reliability of the one-way mechanism
25
.
On the other hand, when the hand wheel
7
is rotated in the lowering direction, the pin
50
is received in either of the receiving portions
52
provided in the opposed positions during one-turn of the hand wheel
7
. Thus, the pin
50
is surely brought into engagement in the receiving potions
52
until the hand wheel
7
rotates one turn, thus enabling the immediate lowering of load.
Thus, even in a hand operated chain block, like the chain block of the embodied form of the invention, in which even a little pulling of the hand chain
62
in the hoisting direction causes the hand wheel
7
to rotate with respect to the first hub
13
a couple of turns during which the pin
50
confronts the receiving portions
52
several times, when the hand wheel
7
is rotated in the hoisting direction, smooth free rotation of the hand wheel
7
with respect to the first hub
13
can be ensured, while also, when the hand wheel
7
is rotated in the lowering direction, the pin
50
can smoothly be received in the receiving portions
52
to ensure the smooth lowering of load.
Especially, in a small-sized chain block having the hand wheel
7
having a small diameter, like that of the embodied form of the invention, in which even a little pulling of the hand chain
62
causes the pin
50
to confront the receiving portions
52
several times, good operation of the pin
50
and the receiving portions
52
can be ensured by the inventive arrangement above and, thus, further improved durability and reliability of the one-way mechanism
25
can be provided.
While the two receiving portions
52
in the one-way mechanism
25
of the embodied form of the invention are formed in the inner periphery of the receiving hole
58
of the boss
22
of the hand wheel
7
at the opposed positions, the receiving portions may alternatively be formed at different positions from the opposed positions. Further, one or three or more receiving portions may alternatively be formed. It should be noted, however, that too many receiving portions
52
would cause an increased rattling of the hand wheel
7
with respect to the first hub
13
, while on the other hand, only one receiving portion
52
could not provide the immediate lowering of load as mentioned above. In view of this, it is most preferable for the small-sized chain block like that of embodied form of the invention that two receiving portions be formed at opposed positions, in terms of improvement in operability, durability and reliability of the chain block.
While in the embodied form of the invention the second recess
56
and the third recess
57
are formed in the boss
22
of the hand wheel
7
at the both sides thereof, the recess may alternatively be formed in the boss at either side thereof. Further, instead of the pin
50
, a ball may be used in the one-way mechanism
25
.
While the illustrative embodiments of the present invention is provided in the above description, such is for illustrative purpose only and it is not to be construed restrictively. Modification and variation of the present invention that will be obvious to those skilled in the art is to be covered in the following claims.
Claims
- 1. A chain block comprising:a load sheave with which a load chain is engageable; a hand wheel with which a hand chain is engageable; a transmission mechanism including a mechanical brake interposed between said hand wheel and said load sheave; an overload protection mechanism that supports said hand wheel and permits said hand wheel to freely rotate in a hoisting direction when a load more than a rated load is applied to said load sheave; and a drive shaft, passed through said load sheave, said transmission mechanism and said overload protection mechanism, to transmit drive applied from said hand wheel to said load sheave, wherein said overload protection mechanism includes a hub member threadedly engaged with said drive shaft and supporting thereon said hand wheel in a freely rotatable manner; and a one-way mechanism that permits said hand wheel to freely rotate in a hoisting direction with respect to said hub member and restricts said hand wheel freely rotating in a lowering direction; wherein said one-way mechanism includes a recess formed in an outer periphery of said hub member; an engaging member provided in said recess and normally biased radially outwardly; and a concave receiving portion, opening in an inner periphery of a boss of said hand wheel, to receive said engaging member therein; wherein said receiving portion includes a slanted surface extended obliquely to guide said engaging member received in said receiving portion to said inner periphery of said boss of said hand wheel when said hand wheel is rotated in said hoisting direction; and a retaining surface, extended substantially along a radial direction of said inner periphery of said boss, to permit said engaging member received in said receiving portion to be retained in an inside of said receiving portion when said hand wheel is rotated in a lowering direction; and wherein said slanted surface formed in said receiving portion is extended along a tangential direction to said inner periphery of said hand wheel and also is smoothed out at a boundary between said inner periphery of said boss of said hand wheel and said slanted surface.
- 2. A chain block according to claim 1, wherein there are provided two receiving portions which are opened in said inner periphery of said hand wheel at positions opposed to each other and of which slanted surfaces are formed to be substantially parallel to each other.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-301896 |
Oct 1998 |
JP |
|
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Name |
Date |
Kind |
5305989 |
Nishi et al. |
Apr 1994 |
|
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Nishi et al. |
Oct 1994 |
|
5472171 |
Nishi et al. |
Dec 1995 |
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JP |
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Jul 1978 |
JP |
7-12912 |
Feb 1995 |
JP |
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Mar 1995 |
JP |
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JP |