Endless belt power transmission systems or components – Friction drive pulley or guide roll – And additional coaxial surface for engaging same belt in...
Reexamination Certificate
1999-11-24
2001-07-31
Green, Mary Ann (Department: 3682)
Endless belt power transmission systems or components
Friction drive pulley or guide roll
And additional coaxial surface for engaging same belt in...
C474S175000
Reexamination Certificate
active
06267702
ABSTRACT:
BACKGROUND OF THE INVENTION
Pulleys to facilitate hoisting and lowering of loads and general products are well known. These pulleys are especially used in the building and construction sectors and are normally handled by two persons, one of them being placed at the top where the pulley is fastened and the other at floor level.
This pulley consists of a disk with a supporting groove or race guiding the rope, idling around its shaft supported by a yoke equipped with a fastening device.
These pulleys have no protective device to prevent the load from falling down when the pull leg of the rope is released by the operator at floor level. Some pulleys have been provided with a safety ratchet gear blocking the load and consisting of a gear wheel keyed onto the disk shaft and a ratchet but this safety system has several drawbacks, the most important of which is the fact that this ratchet gear has to be released for each operation and this is extremely dangerous.
SUMMARY OF THE INVENTION
This invention has the aim to eliminate this drawback and to provide the pulley with an automatic safety brake. This braking system consists of a double walled rocker arm having the shape of a right-angled triangle, its hypotenuse being slantwise located at the top, its smaller acute angle (&agr;) located at the bottom towards the load leg of the rope, whereas the greater acute angle (&bgr;) is located at the upper end of the manual pull leg of the rope.
This rocker arm is secured to the outside of the pulley yoke by means of transverse axle pivot pins, slightly offset with respect to the shaft axis of the pulley sheave in the direction of the manual pull rope. A snatch block is fastened at a right-angle (&ggr;) level of the rocker arm at the bottom towards the pull rope, whereas an adjustable counterweight is mounted at the level of the smaller acute angle (&agr;). At the level of the greater acute angle (&bgr;), a transverse axle pin bearing a grip wedge may be inserted between the rope lodged in the pulley race and a bushing supported by a transverse pin fixed onto the yoke thus blocking the rope in the pulley race.
In this way, the brake is operating as follows:
When the load is applied to the lifting or lowering rope, the pull rope handled at floor level by the operator, will push against the snatch block located at the right-angle (&ggr;) of the triangle. This thrust will override the action of the counterweight and will force the rocker arm to rotate (clockwise in the drawing) so as to remove the wedge and keep it outside, so that the rope can freely move.
If action on the pull rope is lacking for any reason whatsoever, the counterweight will cause the snatchblock to move in the opposite direction (counter-clockwise in the drawing) and the wedge will slip between the bushing of the yoke and the rope thus blocking any rope movement. Usually, the gripping surface of the wedge in touch with the rope will be rifled or toothed so as to heighten the reciprocal blocking action.
When the load leg of the rope is unloaded, this load leg has only to be moved outwards in order to push a pawl which will cause the rocker arm to rotate clockwise, thus pulling out the grip wedge so that the rope can run downwards.
This proves that the automatic brake, subject matter of this invention, will ensure an absolutely safe operation of the pulley during its load lifting and lowering motion without any risk whatsoever of dropping the load.
REFERENCES:
patent: 3881361 (1975-05-01), Newell
patent: 3915268 (1975-10-01), MacDonald
patent: 4040305 (1977-08-01), McCabe
patent: 4327881 (1982-05-01), Fohl
patent: 4538703 (1985-09-01), Ellis et al.
patent: 5052523 (1991-10-01), Ericson
patent: 5513607 (1996-05-01), Doragrip et al.
patent: 050363 (1982-08-01), None
IBM Technical Disclosure Bullitin, (NN55041080) “Power Platen Indexing Mechanism”, Apr. 1965.*
IBM Technical Disclosure Bullitin, (NN78112411) “Lever Control Mechanism For a Doc. Stacker”, Nov. 1978.
Olani Angelo
Ravaglia Giovanni
Charles Marcus
Goldberg Richard M.
Green Mary Ann
Tornomeccanica S.r.l.
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