Handling: hand and hoist-line implements – Hoist-line slings
Reexamination Certificate
2001-06-20
2002-09-10
Kramer, Dean J. (Department: 3652)
Handling: hand and hoist-line implements
Hoist-line slings
Reexamination Certificate
active
06447035
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to slings used for lifting large, heavy objects, and more specifically to a sling with a circular strap that passes through one or more rings. The ring(s) aid in attaching the sling to a crane and they float freely around the strap.
The type of sling described in this application is not of the type that David used to slay Goliath, i.e., not a weapon. Rather, the present invention relates to the type of sling that is used for cradling and hoisting objects. These types of slings typically include a rope, strap, chain or cable that can be looped around an object. Straps are commonly made of a webbing material that can be man-made or natural. Lengths of rope, straps, chains or cables (herein after “straps”) each have the ability to loop back on itself. With minor adjustments or with the addition of a small amount of hardware straps can also make a slip noose. A slip noose is a useful feature because the noose tightens around the object by pulling on the end opposite of the loop. When the loop of a sling is placed around an object the sling can be used as a support, a cradle or to hoist the object.
Slings have traditionally been used to haul and lift heavy, awkward objects. Their pliable material can conform to the shape of the object to be lifted, making them versatile. Industries such as forestry, utility and logging commonly use slings to move trees, poles and logs.
Because the present sling uses a circular design the number of straps, or support legs, is doubled compared to traditional single strap slings. In other words, when a loop is formed at one end of the present sling and the opposite end is used to hoist the object, there are actually two straps that are supporting the object. In the preferred method of using the present sling, both ends of the slings are used for lifting or supporting and thus four straps, support legs, are actually involved.
The preferred method for using the present sling is a modified double basket. A double basket is a well known lifting technique traditionally involving a long single strap that is wrapped one and a half times around a log or pole and then both ends of the strap are used to lift the object. A double basket is beneficial in two ways. First, it provides slip noose like gripping capabilities with no modifications to traditional single strap slings. Second, since both ends of the strap are involved in lifting the log, as much as twice the amount of weight can be lifted compared to the single strap's lifting maximum. Each of these benefits however, is also accompanied by a failing when a traditional sling is employed. First, the slip noose like grip of the traditional double basket does not provide as tight of a grip as a traditional slip noose, per square inch. Second, each support leg is still only as strong as a single strap. The present modified double basket method eliminates both of these failings. The present sling, used in the preferred method, provides better gripping ability than a slip noose and each support leg provides twice the strength of a single strap. Thus, the well known double basket lifting method can still be used by those in the field but, with the present sling the lifting method will be more efficient, simply by employing a slight but important modification.
The rings that may float freely around the present sling also provide a novel feature. They are designed to provide a quick and easy stress test that indicates when the strap has lifted too much weight and therefore should be discarded. Each ring has an associated stress ball that is a solid ball designed to pass through the middle of its associated ring, when the ring is in good operating condition. The inside diameter of the floating ring is roughly equal to the diameter of its associated stress ball. In the event that the strap has been over stressed either by lifting too heavy of a load or because of stress over time, the ring will dis-form inward and the stress ball will no longer be able to pass through the middle of the ring. If a user tries to pass a stress ball through its associated ring and the stress ball cannot fit through the middle of the ring, then the ring and therefore the strap has failed the stress test and that floating rings sling should be discarded.
The present sling can be used in other methods besides the preferred modified double basket method. For example, the sling can be used in a single basket lifting method and in a traditional slip noose. In the slip noose method, one of the rings is looped through the circular strap or a second larger ring in order to create the noose. The circular strap and rings can be provided in a variety of sizes and the strap can have one or more floating rings. Thus, many more uses are made possible by the present sling and are not limited to the above examples.
SUMMARY OF THE INVENTION
The present invention provides a circular strap used for lifting objects wherein one or more metallic rings float freely around the circular strap and at least one of the rings is used as a connection point that is connected to a lifting force, such as a crane or winch. The circular strap can be used in well known lifting techniques that normally employ a single strap sling, as well as other techniques that are not possible with a single strap sling. In the preferred embodiment, the strap has a uniform width and is made of a man made webbing material. In alternative embodiments, the strap is made of other materials. The one or more rings are made of metal or a metal alloy and each ring has an associated stress ball that provides a quick and reliable stress test for the sling. Rings in good operating condition allow the stress ball to pass through their middle freely. A ring indicates that the sling has been over stress by dis-forming and not allowing the stress ball to pass through its middle.
A new lifting method is also disclosed. The new modified double basket lifting method is made possible by the present floating rings sling. In this preferred method, the circular strap is provided with two rings. The first ring is attached to a crane, or other lifting force, and the second ring leads the strap under a log, for example, up around the other side, over the top of the log, and then back under the log for a second time and then finally back up to attach to the crane. During the second pass under the log, the second ring passes through the middle of the double strap thereby forming a noose around the log. This lifting technique provides better gripping and a dramatically increased lifting maximum compared to the traditional double basket method.
REFERENCES:
patent: 1686288 (1928-10-01), Meals
patent: 2152096 (1939-03-01), Russell
patent: 2569912 (1951-10-01), Andersen
patent: 3583750 (1971-06-01), Norton
patent: 5330240 (1994-07-01), Barra
patent: 626635 (1961-08-01), None
patent: 2678918 (1993-01-01), None
patent: 423391 (1935-01-01), None
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