Patent Grant
9656836
This disclosure relates to a safety device adapted to be placed between a hoisting rope and a tie back attachment point when the hoisting rope is not in use. The hoist rope is typically part of a hoisting machine, such as a crane or an electric mining shovel.
Crane ropes with overhaul balls, lift blocks or end rigging at the end of hoist ropes are usually secured or tied back to the structure of the crane when not in use, or when transporting the crane. The purpose of the tie back is to prevent injury to personnel or damage to crane components resulting from uncontrolled swinging of the crane hook or rigging.
It is a relatively common situation, where a crane operator, due to some temporary inattentiveness, does not remove the tied back line or forgets that such lines are tied back by some type of rigging, and begins to advance or raise the boom or line on a RT crane, or boom down or advance the line on a crawler crane. This causes the secured line or rigging or structure to break once its ultimate fracture strength is exceeded. When this happens, part of the hoist machine rigging can be released and fly through the air with destructive force.
It is therefore advantageous to provide an indication to the crane operator, to forewarn the crane carrier operator, and any bystanders, of a potentially destructive and dangerous situation involving an overload condition.
Disclosed is a safety device adapted to be placed between a hoisting rope and a tie back attachment point when the hoisting rope is not in use. The safety device comprises two straps, the first strap being of a shorter length and a smaller fracture strength, and the second strap being of a longer length and a larger fracture strength, with one end of the first strap and one end of the second strap being adapted to be attached together to the hoisting rope, and the other end of the first strap and the other end of the second strap being adapted to be attached together to the tie back attachment point.
In one embodiment, the safety device straps are made from weaved synthetic material, the second strap having an inner portion folded back upon itself so that the folded length of the second strap is the same as the first strap. A loop is formed at the end of each and every strap, the second strap being wider than the first strap, and the second strap being thicker than the first strap.
Before one embodiment of the disclosure is explained in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Further, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upward”, “downward”, “side”, “top” and “bottom”, etc., are words of convenience and are not to be construed as limiting terms.
Disclosed in the drawings is a safety device 10 adapted to be placed between a hoisting rope 14 and a tie back attachment point 18 when the hoisting rope 14 is not in use. The safety device 10 comprises two straps, the first strap 22 being of a shorter length and a smaller fracture strength, and the second strap 26 being of a longer length and a larger fracture strength. One end 34 of the first strap 22 (see
In order to make the overall length of both straps the same, the second strap 26 has an inner portion 30 folded back upon itself, as shown in
The one end of the safety device 10 intended to be attached to the hoist rope 14 can be attached to the hoist rope through hoist rope rigging, for example, a crane hook 16 or rigging chains, or any other means typically present at the end of one or more hoist ropes.
As illustrated in the drawings, a loop 32 is formed at the end of each and every strap by having a strap end piece folded back upon a near portion of the strap. More particularly, where the strap end piece is folded back upon the near portion of the strap, it is secured in place by stitching, as illustrated in
In one embodiment, each strap is made from weaved synthetic material, such as nylon. In other embodiments (not shown), other materials and other shapes may be used for the straps, as long as the fracture strength of each strap can be reasonably predicted.
In order to provide each weaved strap with the indicated fracture strengths, the second strap 26 is wider than the first strap 22, and the second strap 26 is thicker than the first strap 22, as shown in
To further provide a solid appearance to the safety device 10, a cloth device cover 42, as shown in
The advantage then of the disclosed safety device 10 is that it can be employed to tie back one or more hoist ropes. As described above, a machine operator may inadvertently start to operate the machine, forgetting that the hoist rope is in a tied back situation. When this occurs, the cover tears open. Then if the overload situation persists, then the first strap fractures, i.e., ruptures, once the load on the safety device 10 meets the first strap fracture strength. For example, the cover fracture strength may be 4,000 or 10,000 pounds of pull. Different fracture strengths are appropriate for different hoist machines, for a substantial load is applied to the safety device by virtue of the weight of hoisting rope and its rigging, such as rigging chains or crane hooks.
After the cover tears and the first strap fracture strength is exceeded, the first strap 22 will fracture. And in view of the load on the safety device 10, the second strap 26 will become extended; the folds 30 of the second strap 26 becoming unfolded. Since the fracture strength of the second strap 26 is greater than the current load on the safety device 10, the second strap 26 should remain in tack, and not fracture. This near immediate extension of the safety device 10 results in a momentary slack situation in the hoist rope 14. This momentary slack situation results in a jerk in the hoist rope, one that often produces noise and exceptional vibration in the hoisting machine, alerting bystanders to the potential danger. If the operator senses one or both of the noise and vibration, the machine operator can stop any further movement of the hoist machine.
If the operator does not sense the immediate extension of the safety device however, then eventually the fracture strength of the second strap may be exceeded, with the result that the hoist rope is no longer tied back.
Various other features of this disclosure are set forth in the following claims.
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| Number | Date | Country | |
|---|---|---|---|
| 20150266705 A1 | Sep 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61995008 | Mar 2014 | US |
