Chain lever hoist

The most commonly used spring type chain lever hoists suffer from a major drawback in that, if the chain is drawn quickly over the load sheave while it is set for free running operation, the brake will automatically be applied and the free running movement terminated. Similarly, if a light load is suspended from the chain, the weight of the load may be insufficient to activate the brake with the result that the load will be wound down dangerously quickly, leading on occasion to accidents. The present invention is designed to resolve these potentially fatal flaws by enabling a hub, which screws freely onto a spindle in the conventional manner, to be rotated through a few degrees into a prescribed lock position relative to the spindle and then locked there either temporarily or permanently as required.

BACKGROUND OF THE INVENTION 
1. FIELD OF THE INVENTION 
The invention relates to a chain lever hoist (hereafter "lever hoist") with 
a load chain and that can be manually operated by means of a lever, for 
example, to wind goods up or down or to pull them along. 
2. DESCRIPTION OF THE PRIOR ART 
Generally speaking, this kind of lever hoist must not only to be capable of 
winding goods up and down (hereafter "winding operation") by means of a 
lever-operated load chain, but must also allow the chain to move freely 
under no-load conditions. In other words, it is normally held to be 
essential that the chain hoist should be provided with what is sometimes 
called a "load sheave" to allow for the free running of the chain. 
Of the conventional types of lever hoist in current use, one of the best 
known and most commonly used types is structured such that the load 
sheave, which is fitted to the main framework of the apparatus, is also 
joined to a spindle to which a fixed friction plate is secured, said 
spindle also being screwed into a hub incorporating a device for switching 
between upward and downward winding operations, the part of the spindle 
between the fixed friction plate and the hub being also fitted with a 
ratchet gear which has brake linings on both sides and which is able to 
slide and rotate freely on said spindle such that the distance between 
said fixed friction plate and said hub can be varied by screwing the hub 
up or down the spindle in such a way as to squeeze or release said ratchet 
gear and brake linings, such action being also assisted by the fitting, 
for example, of a coil spring in extended condition between said fixed 
friction plate and said hub such that the hub is ordinarily pressed 
outwards by the force of the coil spring, thereby easing the contact 
pressure of the hub on said brake linings and, in so doing, preventing the 
brake from being applied. In lever hoists of the type described above, it 
is common for a heavy duty hoist with a load capacity of 0.5 tons or more 
to have its load sheave and spindle linked through the medium of a 
plurality of reduction gears but for a light hoist with a load capacity of 
less than 0.5 tons to have its load sheave and spindle connected to each 
other directly. Spring lever hoists of the type outlined above suffer from 
a significant drawback, however, in that when the chain is moved quickly 
while the load sheave is in free running operation, the spindle turns but 
the hub does not turn with it and, since the spindle and the hub are 
linked by a threaded connection, the space between the fixed friction 
plate and the hub is automatically narrowed and the brake applied, thereby 
eliminating the capacity for free movement. The hub thus has to be rotated 
manually back each time this happens in order to re-open the gap between 
the hub and the fixed friction plate and release the brake. 
Another problem with the conventional type of spring lever hoist is that, 
when winding down a light object, the force with which the spindle is 
being screwed into the hub is sometimes weaker than that with which the 
coil spring is pressing the hub outwards. In this sort of case, the object 
being lowered is sometimes let down too quickly and this has in the past 
led to accidents, some of which have been fatal. In other words, 
conventional spring lever hoists have what we might call a reciprocal 
problem in that, if the coil spring is fairly powerfully extended, this 
will ensure that there is plenty of play in the hub and spindle but there 
will also be a risk that light objects may be lowered too quickly, leading 
to accidents. On the other hand, if the spring is only weakly extended, 
this will help prevent accidents when lowering light objects but, 
conversely, any rapid movement of the chain while running freely over the 
load sheave will immediately cause the brake to operate, thus interfering 
with the free movement of the chain. There are, of course, a variety of 
mechanisms that can be used to ensure the free running of a load sheave. 
These include a mechanism whereby, in lever hoists equipped with reduction 
gears of the type referred to above, the reduction gear spindle can be 
caused to slide as a means of shifting the gear teeth out of line with 
each other, thereby permitting the load sheave to rotate freely. Another 
such mechanism disconnects the pawl from the ratchet gear and this again 
has the effect of allowing the load sheave to rotate freely. The use of 
these types of mechanism certainly helps prevent the sorts of problems 
outlined above but, at the same time, the complexity of these mechanisms 
can in itself be a source of problems in that the smooth operation of the 
apparatus is rendered more problematic. There is also a concomitant loss 
of reliability in that the apparatus tends to break down more often. 
Moreover, the change from a free running to a winding action always 
requires a single action. 
SUMMARY OF THE INVENTION 
The inventors have experimented with a variety of different ways of 
resolving the sorts of problems outlined above and have eventually come to 
the conclusion that one answer would be to ensure the free movement of the 
lever hoist by causing the spindle and the hub to rotate as one, thereby 
preventing activation of the brake mechanism. The object of the present 
invention is thus to provide a means of enabling the hub to be rotated 
manually through just a few degrees in relation to the spindle and then 
fixed in a prescribed lock position in relation to the spindle, such that 
the hub does not exert contact pressure on the ratchet gear and brake 
linings, and then to ensure that the relationship between the spindle and 
the hub is maintained in this condition, thereby enabling the load sheave 
to rotate freely. In order to achieve the above object, we made use of a 
structural configuration whereby the main framework was fitted with a load 
sheave, in such a way as to enable it to rotate freely, and a spindle, 
also in such a way as to enable it to rotate freely along with said load 
sheave. Said spindle was also fitted with a fixed friction plate and was 
screwed into a hub. A ratchet gear and brake linings were also fitted onto 
said spindle in such a way as to enable them to slide and rotate freely in 
between said fixed friction plate and said hub. The main framework was 
also fitted with ratchet pawls positioned such as to enable them to engage 
the teeth of said ratchet gear, and a position locking mechanism which 
enables the hub to rotate through a few degrees away from the winding 
operation position into a prescribed lock position in relation to the 
spindle in which it is then be held steady. 
The operation of a lever hoist configured in the above manner is such that, 
if the apparatus is set for upward winding and the winding lever, or 
similar mechanism, is then used to turn the hub to wind the apparatus 
upwards, the torque generated by the combination of the weight of the 
suspended load and the force applied to turn the hub causes the hub to 
screw on to the spindle and, in so doing, to squeeze the aforementioned 
ratchet gear and brake linings between the hub and the fixed friction 
plate such that, if the hub is then turned further in the same direction, 
the force of the rotation is transmitted from the hub to the ratchet gear 
and brake linings and from there to the fixed friction plate, the spindle 
and the load sheave, thereby turning the spindle in such a way that the 
ratchet gear engages the ratchet pawls and the load sheave is wound 
upwards. When the apparatus is Wound downwards, on the other hand, 
although the torque generated by the weight of the suspended load causes 
the hub to screw onto the spindle, again squeezing the ratchet and brake 
linings between the hub and the fixed friction plate, if the lever is then 
used to wind the hub as for a downward winding operation, the torque 
generated by the rotation of the hub in this case tends rather to offset 
the force generated by the suspended load and, in so doing, to mitigate 
the squeezing force with the result that a measure of slippage is secured 
between the ratchet gear and brake linings on the one hand and the fixed 
friction plate on the other and the load sheave duly winds down in line 
with the rotation of the hub. When the apparatus is set to free running 
operation, the hub is first rotated manually through just a few degrees 
until it reaches the prescribed lock position, namely the position in 
which the hub exerts no contact pressure on the ratchet gear and brake 
linings. At this point, it is then locked by the aforementioned position 
locking mechanism, which sets the spindle and hub in positions relative to 
each other in which the brake will not be activated, and this enables the 
load sheave to be spun freely and quickly without activating the brake. 
It is possible, therefore, in the lever hoist of the present invention, to 
create a space between the fixed friction plate and the hub by shifting 
the hub into a prescribed lock position in which the contact pressure on 
the ratchet gear and brake linings is released and then using a position 
locking mechanism to set the hub in said prescribed lock position such 
that the spindle and the hub are then held in positions relative to each 
other in which the brake will not be activated, thereby enabling the 
apparatus to run freely and steadily without any risk that the brake will 
be activated before the operation is completed. Again, since, unlike the 
conventional type of spring lever hoist, there is no coil spring or 
associated parts maintaining constant outward pressure on the hub, when 
the aforementioned position locking mechanism is released, the hub will 
immediately exert contact pressure on the ratchet gear and brake linings 
with the result that the danger of light loads being wound down 
dangerously quickly through failure to activate the brake mechanism is 
completely eliminated. Furthermore, if the holding strength of the 
position locking mechanism is set to a level less than that of the torque 
applied to the hub to wind the load chain up, the winding function of the 
apparatus can be activated simply by initiating the winding action.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 through 5 illustrate the first embodiment of the invention. In FIG. 
1, 1 is the main framework, 2 is a load sheave fitted to the main 
framework 1 in such a way as to enable it to rotate freely, 3 is a load 
chain Which loops over said load sheave 2, 4 is a spindle which is fitted 
to the main framework 1 in such a way as to enable it to rotate freely and 
which also has a threaded section 4a at one end and a spindle gear 4b at 
the other end, said spindle gear 4b engaging the load sheave 2 gear 2a 
through the medium of a set of reduction gears G. 5 is a disc-shaped hub 
with a threaded hole in the center into which is screwed the externally 
threaded section 4a of the aforementioned spindle 4. Said hub 5 
incorporates a friction plate 5b, a switch gear 5a and a boss 5c on the 
outer surface. In this case, the outer surface of the hub 5 also acts as a 
knob to enable the manual rotation of the hub 5. This knob could just as 
easily be made entirely separate and subsequently fitted to the outer 
surface of said hub 5. 6 is a fixed friction plate secured to the spindle 
4. A ratchet gear 7 and one or more brake linings 8 are mounted in such a 
way as to allow them to rotate and slide freely on the spindle 4 in 
between the aforementioned friction plate 5b and the fixed friction plate 
6. The ratchet gear 7 and the brake linings 8 can be tightened or eased by 
rotating the hub 5 manually in order to vary the size of the gap between 
the fixed friction plate 6 and said hub 5. 
Also in FIG. 1, 7a is a pair of ratchet pawls that are fitted to the main 
framework 1 and that engage the aforementioned ratchet gear 7, and 9 is a 
lever that is fitted in such a way that it pivots about the spindle 4. 10 
is a knob for switching between a winding operation and a free running 
operation, which is fitted to the lever 9 in such a way as to enable it to 
rotate freely and which has a U shaped switch claw 10a on its inside end 
that engages the aforementioned hub 5 at switch gear 5a. 11 is a plate 
spring shaped like a fan, as shown in FIG. 2, and secured to the spindle 4 
in such a way that it is able to rotate around said spindle 4, said plate 
spring 11 and the aforementioned boss 5c together comprising a position 
locking mechanism. 
FIG. 2 shows a condition in which the hub 5 has been rotated in a clockwise 
direction to screw it onto the spindle 4. In this condition, the boss 5c 
makes pressure contact with the plate spring 11, as shown in FIG. 4, in 
such a way that boss 5c is able to slide against said plate spring 11. 
FIG. 3 shows the hub 5 moved manually counterclockwise through a few 
degrees and then set at a prescribed lock position. The counterclockwise 
movement of the hub serves to disengage the boss 5c from the plate spring 
11, as shown in FIG. 5, and allows it to come to rest against the 
counterclockwise edge of said spring 11, thereby temporarily preventing 
the hub from rotating back in a clockwise direction. 
Next, we will describe the basic operation of a lever hoist configured in 
the manner outlined above. When carrying out an upward winding operation, 
first the aforementioned knob 10 is flipped in a clockwise direction so 
that the left hand tooth of the switch claw 10a, shown in FIG. 2, engages 
the switch gear 5a. If the aforementioned lever 9 is now rotated in a 
clockwise direction, the combination of the weight of the suspended load 
and the torque applied by said lever 9 will cause the hub 5 to screw onto 
the spindle 4 and, in so doing, to squeeze the aforementioned ratchet gear 
7 and brake linings 8 between the hub 5 and the fixed friction plate 6. At 
this point, the boss 5c is in pressure contact with the plate spring 11 as 
shown in FIGS. 2 and 4. If the aforementioned lever 9 is now turned 
repeatedly in a clockwise direction, the turning force will be transmitted 
from the hub 5 through the ratchet gear 7, the brake linings 8, the fixed 
friction plate 6 and the spindle 4 to the load sheave 2 and, as the 
ratchet gear 7 turns, riding repeatedly up over the ratchet pawls 7a, so 
the load sheave 2 will also rotate and wind up the load chain 3. When 
carrying out a downward winding operation, on the other hand, first the 
aforementioned knob 10 is flipped in a counterclockwise direction so that 
the right hand tooth of the switch claw 10a, shown in FIG. 2, engages the 
switch gear 5a. The torque generated by the suspended load will again 
cause the hub 5 to screw onto the spindle 4 and, in so doing, to squeeze 
the aforementioned ratchet gear 7 and brake linings 8 between the hub 5 
and the fixed friction plate 6. At this point, the boss 5c is again in 
pressure contact with the plate spring 11. However, if the aforementioned 
lever 9 is now turned repeatedly in a counterclockwise direction, as it 
turns, the torque generated by the lever 9 will be sufficient to mitigate 
the squeezing force described above and, in this way, to allow the fixed 
friction plate 6 on the one hand and the aforementioned ratchet gear 7 and 
brake linings 8 on the other sufficient freedom to slide against each 
other, thereby enabling the load sheave 2 to rotate and wind down the load 
chain 3. 
When the chain is to be allowed to run freely over the load sheave, the 
knob 10 is first set to the neutral position, as shown in FIG. 3. in order 
to disengage the switch claw 10a from the switch gear 5a and enable the 
hub 5 to be manually rotated counterclockwise through a few degrees and 
temporarily secured in the prescribed lock position. In other words, the 
boss 5c has been disengaged from the plate spring 11, as shown in FIGS. 3 
and 5, and has come to rest against the counterclockwise edge of said 
spring 11, thereby preventing the hub from rotating back in a clockwise 
direction. In this position, the contact pressure of the hub 5 on the the 
ratchet gear 7 and the brake linings 8 is eased and the spindle 4 and the 
hub 5 are held in fixed positions relative to each other, thereby 
preventing the brake from being applied. This has the effect of allowing 
the load sheave 2 to rotate freely and, at the same time, of preventing 
the brake from being applied even if the load sheave 2 is spun round 
quickly. 
Again, since there is no coil spring or associated parts maintaining 
constant outward pressure on the hub 5, as would be the case with a 
conventional spring lever hoist, when the temporary lock secured by means 
of the aforementioned position locking mechanism is released, the hub 5 
will immediately reassert contact pressure on the ratchet gear 7 and brake 
linings 8 with the result that the danger of light loads being wound down 
dangerously quickly through failure to activate the brake mechanism is 
completely eliminated. When switching back from a free running operation 
to a winding operation, if the knob 10 is flipped in a clockwise direction 
so as to cause the left hand tooth of the switch claw 10a to engage the 
switch gear 5a and the aforementioned lever 9 is then wound in a clockwise 
direction, the torque generated by said lever 9 will exceed the force 
exerted by the plate spring 11 to prevent the boss 5c from moving and said 
boss 5c will force the plate spring 11 upwards, thereby allowing the hub 5 
to rotate back in a clockwise direction to return to the condition 
illustrated in FIG. 2. With the mechanism in this condition, the winding 
operation can be started immediately. 
Next, we will describe the second, third and fourth embodiments of the 
invention. In these alternative embodiments, the differences from the 
first embodiment are confined in each case to the position locking 
mechanism. 
FIG. 6 shows the second embodiment of the invention. In the first 
embodiment, the plate spring 11 was shaped like a fan pivoting about the 
spindle. In the second embodiment, by contrast, the plate spring 11' is 
shaped like a disc centered on the spindle and containing a single narrow 
groove 11'a cut in a radial direction from part way along an imaginary 
line extending from the center of rotation of the spindle. In other words, 
FIG. 6 illustrates a condition in which the hub 5 has been screwed in a 
clockwise direction onto the spindle 4 and the boss 5c is in pressure 
contact with the plate spring 11'. If the hub 5 is then manually rotated 
counterclockwise through a few degrees, the boss 5c slips into the groove 
11'a in the plate spring 11', thereby preventing the hub 5 from rotating 
back in a clockwise direction and, in so doing, temporarily locking the 
hub 5 in its prescribed lock position relative to the spindle 4. 
FIGS. 7 and 8 illustrate the third embodiment of the invention. In this 
embodiment, the outer surface of the hub 5 incorporates an indented 
section 12 within which a disc 13 is also secured to the spindle 4, the 
circumference of said disc 13 containing a notch 13a. The indented section 
12 is also fitted with a bar spring 14 with a U shaped projection 14a part 
way along, said bar spring 14 being secured at one end to the inside 
circumference wall of the indented section 12 such that the bar spring 14 
projection 14a presses on the outer edge of the disc 13. FIG. 7 shows the 
hub 5 screwed onto the spindle 4 in a clockwise direction such that the 
projection 14a is pressing on the outer edge of the disc 13. Next, in FIG. 
8, the hub 5 has been manually rotated counterclockwise through a few 
degrees such that the projection 14a has now slotted into the notch 13a on 
the circumference of the disc 13 with the result that the hub 5 cannot now 
be rotated further and the hub 5 and spindle 4 are thus temporarily locked 
into their prescribed lock positions relative to each other. For the 
purposes of the present embodiment, we have assumed that the bar spring 14 
is secured at one end only to the inside circumference wall of the 
indented section 12, but the bar spring 14 could equally be secured in 
this same way at both ends. 
FIGS. 9 and 10 illustrate the fourth embodiment of the invention. In this 
embodiment, the outer surface of the hub 5 incorporates an indented 
section 12 within which a disc 13' is also secured to the spindle 4, the 
circumference of said disc 13' being fitted with a pair of cylinders 15,15 
projecting outwards from the edge of the disc in diametrically opposite 
directions. The outer tip of each cylinder 15 is fitted with an ball 
embedded on the end of a compressed coil spring contained within the main 
body of each cylinder 15. The inside circumference wall of the indented 
section 12 incorporates two notches 16,16 also diametrically opposite each 
other. FIG. 9 shows the hub 5 screwed onto the spindle 4 in a clockwise 
direction such that the balls embedded in each cylinder 15 are pressing on 
the inside circumference wall of the indented section 12 of the hub 5. 
Next, in FIG. 10, the hub 5 has been manually rotated counterclockwise 
through a few degrees such that the balls embedded in the cylinders 15,15 
have now slotted into the notches 16,16 in the indented section 12 with 
the result that the hub 5 cannot now be rotated further and the hub 5 and 
spindle 4 are thus temporarily locked into their prescribed lock positions 
relative to each other. 
FIGS. 11 and 12 illustrate a fifth embodiment of the invention. In 
embodiments 1 to 4, springs or similar devices were used to hold the hub 
and spindle temporarily in their fixed positions relative to each other. 
In the fifth embodiment of the invention, by contrast, when the hub and 
spindle are shifted into their relative fixed positions, they are then 
clamped securely into those positions. In other words, in this case, 17 is 
a cap which is spline jointed in such a way that it can move only in an 
axial direction in relation to the spindle 4. On the back of said cap 17, 
there are two rods 18,18 positioned diametrically opposite each other. 
There are also two holes 19,19 similarly positioned diametrically opposite 
each other in the side of the hub 5. FIG. 11 shows the hub 5 screwed 
clockwise onto the spindle 4 in such a way that the rods 18,18 and the 
holes 19,19 are out of alignment with each other. Next, in FIG. 12, the 
hub 5 is shown after manual rotation counterclockwise through a few 
degrees such that the rods 18,18 slot into the holes 19,19, thereby 
preventing the hub 5 from turning further and effectively securing it 
firmly in its prescribed lock position in relation to the spindle 4. There 
is also a Coil spring (not shown in the drawings) fitted in between the 
hub 5 and the cap 17 such that the cap 17 is constantly being pulled in 
the direction of the hub 5. The coil spring also acts as a torsion spring 
in that it is constantly trying to screw said cap 17 round in a clockwise 
direction. Thus, when the user wants to return the apparatus from a free 
running operation as shown in FIG. 12 to a winding operation, he needs 
only pull the cap 17 forward and it will immediately snap back into the 
winding operation position illustrated in FIG. 11. 
As will be clear from the above, one of the essential characteristics of 
this invention is that, in order to maintain the free running operation of 
the load sheave 2, it ensures that the positions of the hub 5 and the 
spindle 4 can be fixed either permanently or temporarily in relation to 
each other so that they then rotate together in line with the movement of 
the load chain 3. 
One of the merits offered by the first four embodiments of the invention is 
that, since the position locking mechanism exerts only a fairly weak 
temporary holding force on the apparatus, any application of a specified 
level of external force in the form of, for example, the lever 9 torque 
will be sufficient to break the hold of the locking mechanism and 
effectively make the apparatus immediately ready for a winding operation. 
There is no need for the position locking mechanisms of the invention to be 
confined to those described in connection with the embodiments outlined 
above and any mechanism that serves to lock the hub either temporarily or 
permanently in position after it has been rotated manually through a few 
degrees into its prescribed lock position would be acceptable. The wide 
variety of mechanisms that could conceivably serve this sort of purpose 
has not been illustrated or described in the body of the text. There is 
equally no reason why the hub and spindle structures of the invention 
should necessarily be different from conventional hub and spindle 
structures. The hub, for example, could be structured in accordance with 
convention and the pitch of the spindle thread could be made to increase 
gradually in size towards the outer end of the spindle, unlike a 
conventional spindle. In this sort of case, when the hub is manually 
rotated along the spindle, it will inevitably catch on the unusually 
formed part of the spindle and, in this way, become temporarily locked.