Static structures (e.g. – buildings) – Machine or implement
Reexamination Certificate
1999-02-27
2001-01-23
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Machine or implement
C059S060000, C059S060000, C059S060000
Reexamination Certificate
active
06176063
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a panel lifter. More particularly this invention concerns a panel lifter with antidrop protection.
BACKGROUND OF THE INVENTION
A standard panel lifter used, for instance, to raise gypsum sheets and hold them against ceiling joists while they are nailed or screwed to the joists, normally has a base, a mast extending upward from the base and including at least one lower section fixed in the base and at least one movable section telescoping with the lower section and having a laterally directed section face, a panel-support rack mounted at an upper end of the mast, and a crank mechanism on the base and a cable connected between the mechanism and the mast for vertically extending the mast by raising the movable mast section upward relative to the base. The rack can normally pivot at least limitedly about a horizontal axis so that the panel can be pressed against a ceiling that is inclined to the horizontal. Such devices are described in French patents 1,237,967, 2,308,760, 2,538,437, 2,552,478, and 2,623,546.
A particular hazard with such machines is that if the cable or crank mechanism fails, the panel, which can weigh in the neighborhood of 100 lbs for a 12-ft sheet of firecode gypsum board, and the rack will drop precipitously and can seriously injure the workers who are perforce underneath. The problem is compounded by the fact that it is standard to tension the cable and stress the crank mechanism considerably by pressing the panel tightly against the ceiling joists so that it can be easily attached in place.
Thus above-cited French patent 2,538,437 proposes a system where the mast is provided with an antidrop system. Two such devices are provided which act respectively between the lower and middle and between the middle and upper sections of the normally three-part mast. Such a system comprises a wedge that can pivot on the respective mast section and that is urged into a position wedged between the mast sections by a spring, while the cable, when tensioned, holds it out of contact with the mast sections. Thus if the cable breaks, the spring pushes the wedge into position to inhibit relative sliding of the respective mast sections.
The disadvantage of this system is that it often cannot provide sufficient braking force when a particularly heavy panel is being lifted, mainly because it only contacts the section it is intended to brake over a relatively limited surface area. In addition the brake is relatively expensive and complex. Furthermore since it is built in, inside the mast, it is not apparent to the user and gives no assurance that it is there and working.
In addition German utility model 295 01 130 and French patent 1,377,926 describe mast blocking systems describe systems not intended for use with crank-operated system, but instead have a pivotal latching member traversed by the math and making in effect point contact with the mast. These systems are mainly aimed at resisting horizontal stresses and are not aimed at providing antidrop action. They are not readily installed on a panel lifter.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved panel lifter.
Another object is the provision of such an improved panel lifter which overcomes the above-given disadvantages, that is which has an improved antidrop system.
SUMMARY OF THE INVENTION
A panel lifter has a base, a mast extending upward from the base and including at least one lower section fixed in the base and at least one movable section telescoping with the lower section and having a laterally directed section face, a panel-support rack mounted at an upper end of the mast, and a crank mechanism on the base and a cable connected between the mechanism and the mast for vertically extending the mast by raising the movable mast section upward relative to the base. According to the invention a brake jaw at an upper end of the lower section has a jaw face and is pivotal about a horizontal axis below the jaw face between a braking position with the jaw face bearing laterally on the section face and a freeing position with the jaw face pivoted back out of contact with the section face. An actuating handle projecting generally radially of the axis from the jaw is provided so that the jaw can be moved between its positions via the handle. A biasing system urges the jaw into the braking position.
With the system of this invention the brakes are therefore always in effect. Unless manually operated, they will block dropping of the mast so that the user is obligated to actuate the release lever in order to lower the panel rack. Thus the system will respond to failure of the crank mechanism or of the cable. Even if the cable remains taut, for instance if it breaks but remains pinched somewhere, the one-way brakes of this invention will be effective. In fact the system is particularly effective for lowering the panel since the operator can simply release the latch dog of the crank and then, by operating the release levers of the antidrop mechanisms, rapidly lower the mast.
According to the invention the lower section has at its upper end a collar on which the jaw is pivoted. In addition the biasing unit includes at least one tension spring having an upper end engaged with the jaw above the axis and a lower end connected to the lower section below the axis. Alternately the biasing unit includes a counterweight mounted on the jaw.
The lower section in accordance with the invention has at its upper end a collar on which the jaw is pivoted and carrying at least one wheel over which the cable is reeved. There is, nonetheless, no functional connection between the cable and the brake.
With the system of this invention two such brakes of substantially identical construction are provided, one between the lower mast section and the middle mast section, and the other between the middle mast section and the upper mast section. This extremely simple structure makes the panel lifter very safe and quite easy to use. Its operation and existence are obvious to the user who can easily operate it.
REFERENCES:
patent: 5913783 (1999-06-01), Weener et al.
patent: 1237967 (1960-06-01), None
patent: 1377926 (1964-09-01), None
patent: 2538437 (1982-12-01), None
patent: 2552478 (1983-09-01), None
patent: 2623546 (1987-11-01), None
Dorsey Dennis L.
Friedman Carl D.
Tradition de l'Outil a Main T.O.M.
LandOfFree
Panel lifter with antidrop protection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Panel lifter with antidrop protection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Panel lifter with antidrop protection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2531469