The present invention relates generally to self retracting lifelines or SRLs. In particular, the present invention generally relates to an SRL that can be pretensioned in order to limit cable payout.
Self Retracting Lifelines (SRLs) have been well known in the fall arrest industry. Workers use SRLs as a safety means to arrest a dangerous or potentially life-threatening fall, particularly in high rise construction and maintenance. A worker or other user typically wears a safety harness with an aperture (e.g., a D-ring) that is connected to a hook at one end of the SRL. The other end of the SRL is secured to a permanent structural member of the building or work site. The SRL includes a housing that contains a cable that is wrapped around a central reel body. The cable, being connected to the hook on one end, can “pay out” through an aperture of the housing and retract back on itself through the use of a power spring. SRLs utilize an active braking system positioned within the housing that can quickly stop the cable from paying out when a particular velocity or G-force is detected. Most SRL braking systems have incorporated some form of ratchet/pawl mechanism in which a pawl engages a tooth of a ratchet when the braking system senses sufficient G force or revolutions denoting quick cable pay out. A typical ratchet/pawl braking system is illustrated in U.S. Pat. No. 4,589,523 to Olson et al.
Fall arrest equipment is inherently “active,” meaning that it stops a user in the act of a fall. Fall restraint is “passive,” such as a rope or barrier to keep a user from falling in the first place. OSHA mandates fall protection for workers in such applications where the work surface is over 6 feet off the ground. This can include either type of system. However, most high rise applications use fall arrest equipment and, particularly, SRLs.
Most SRLs are of industry standard sizes, e.g., 65′, 50′, or shorter. Because of the predefined length of the cable, various sized products must be used in accordance with the particular work environment and the distance a worker needs to complete a task. For example, a 65′ retractable may not be used on a job site in which the safe fall range exceeds that distance. However, it is expensive and not always practical to have varying size SRLs on each job site or in storage for use in large contractor warehouses.
Further, there is no known attempt at creating an active SRL that can be adapted for variable fall restraint (passive) protection. With little doubt, it is much safer for a user to avoid falling altogether—even if the worker falls with appropriate fall arrest equipment. This is because a falling worker with active fall restraint equipment will stop with a sudden jerk and the fall and sudden stop can cause panic, discomfort, and possible injury. However, OSHA guidelines will not allow a purely passive restraint system to be utilized where active fall arrest is required. There is no known commercial solution to combine an active fall arrest SRL with a passive restraint feature into one device in which the cable payout distance cannot physically go past a particular job-site requirement (e.g., the falling point off a ledge or roof edge of a building), as well as the possibility of using a single SRL (e.g., 65′ SRL) in a multitude of work environments.
The present invention is directed to an active self-retracting lifeline (SRL) having an active braking system that also includes a passive cable pay out limiting feature that functions independently of the active braking system. In the present invention, the SRL is adapted to include a pretension assembly that allows a user to pretension the cable take-up a set amount prior to use. For example, a 65′ SRL could be pretensioned to effectively limit cable payout to 30′ for a particular application. Once the SRL is pretensioned to the desired length, the user can only move about the distance that the user intended (in the example, 30′) as there is no additional cable to allow movement past this distance. In this way, the worker virtually avoids the need for the active braking system of the SRL as the user is unlikely to find himself or herself in a fall situation.
The SRL of the present invention include a cable length that is wrapped around a central reel body. A power spring that retracts the cable back when paid out can pay out or take in before binding in on itself. This can be measured in the revolutions that the spring can make or “turns.” The user can limit the number of turns that the spring can make by winding up the power spring, in which a portion of the spring is rendered immobile by fixing it to an arbor, which is ordinarily directly or indirectly fixed to an interior portion of the housing and the other portion of the spring is connected to the reel body that rotates about an arbor. The amount of turns the power spring is wound without any cable being paid out is called “pretension.”
To artificially pretension the power spring, the pretension assembly functions to temporarily mobilize the arbor so that the arbor can rotate when a force is applied to it. The rotating arbor pretensions the power spring a number of desired turns.
According to a first embodiment, the pretension assembly may include an actuator and a pair of engaged aligned plates that are capable of being disengaged when a force is applied to at least one of the plates. One of the plates is directly or indirectly attached to the SRL housing. A portion of the arbor is prohibited from rotational movement relative to the other plate when the plates are engaged. When the actuator is activated, it temporarily mobilizes the arbor because the aligned plates are separated through tension force, which may be a tension spring. According to one aspect of the invention, the aligned plates are a lock ring and a mating lock ring plate. According to another aspect of the invention, the lock ring may include a plurality of sides or faces, such as in the shape of a hexagon, that mate with a similar shaped lock ring plate. The number of faces may vary, but the number can be used to determine the resolution of the distance limiting function.
According to one aspect of the invention, one of the aligned plates is to the housing through a perch or perch ring.
According to another embodiment, the pretension assembly may include a pair of aligned plates in which the plates are connected through a plurality of pins and corresponding apertures or plates with corresponding mating splines/teeth that prohibit rotational movement of the arbor until the plates are disengaged. One of the plates is secured to the housing and may itself be a perch or perch ring.
According to yet another aspect of the invention, the actuator may be a quick release cammed actuation lever having a handle. The cammed actuation lever and handle allow the user to immediately see if the actuation lever is in the open position or not. Further, the handle makes it easier to determine the number of turns that are to be made in the field in order to limit the cable pay out to a set distance.
In use, the actuator is activated and applies a force on the tensioner to disengage the pair of aligned plates. The arbor, which is connected to one of the aligned plates, is then temporarily mobilized and may be rotated to pretension (or take up) the power spring, which necessarily limits the cable pay out by the number of turns the power spring is pretensioned. Once the user sets a desired cable payout length, the actuator is deactivated and the aligned plates are again engaged in a mating relationship and the arbor is once again rendered immobile relative and can no longer rotate.
Another embodiment of the invention includes an overtensioning assembly. According to one aspect of this overtensioning assembly, a pair of fittings on the opposite end of the arbor in order to prevent the power spring from being over-tensioned through human error. One fitting, such as a spin stop fitting with a shape to correspond to a threaded nut head, may be affixed to the other end of the SRL housing. A corresponding spinnable fitting, such as threaded nut head, may be mounted at the end of the arbor. The arbor may rotationally move within the spin stop fitting via the threaded head nut which can laterally slide within the spin stop fitting until it hits an abutment, such as an end plate, indicating that the power spring should not be further tensioned.
These and other advantages will become more apparent upon review of the Drawings, the Detailed Description of the Invention, and the Claims.
Like reference numerals are used to designate like parts throughout the several views of the drawings, wherein:
The present invention is directed to a self-retracting lifeline (SRL) 10 in which the cable payout can be limited to a desired length in the field to allow maximum usage from a single device.
Referring to
The SRL of the prior art contains an active fall arrest braking system 9, such as the kind shown in afore-mentioned U.S. Pat. No. 4,589,523, that may include a set of pawls 10 and ratcheted ring 11 in which the pawls engage teeth 12 of the ratchet ring when a sufficient force is quickly applied to the end of the cable (such as a worker in a state of fall).
Now referring to
The cable 34 externally pays out from the housing 22 through an aperture 40 of the housing 22. The SRL of the present invention further includes an active braking mechanism 42 that may be like the type known in the prior art (such as a brake ring 44 and a set of pawls 46, as illustrated). Such active braking systems are well known to those of skill in the art and are not further discussed in detail.
SRL 10 further includes a power spring 48 that provides a rotating force to the central reel body in order to enable the cable to retract when the cable is paid out. The power spring is connected at one end to the arbor 28, and at the other end to the central reel body 26. The power spring can only make so many revolutions before it binds in on itself. The number of revolutions the power spring can turn before it binds in on itself is measured in terms of “turns.” The present invention is directed to pretensioning the number of turns that the power spring can make in order to prelimit the distance the cable can payout to a desired distance.
Now referring also to
According to another aspect of the invention, the actuator is a cammed quick release lever 66 that can easily open and close the actuator and the handle portion 68 allows the user to easily make the desired number of turns in order to pretension the power spring.
The actuator 60 is secured to the other aligned plate that is not affixed to the housing at one end and to the arbor 28 at the other end. According to one aspect of the invention, the actuator has an end portion 70 of a size and shape to mate with a generally central opening 72 of the other aligned plate (the lock ring 54, as illustrated). In this way the arbor is engaged with the lock ring and can not rotate without the plates being disengaged.
The lock ring plate and lock ring of the present invention may have a set number of mating faces 74 (six are shown) such that lock ring plate and lock ring are joined. The lock ring cannot rotate as long as the lock ring plate is secured to the housing. When the tensioner (compression spring 58) abuts the lock ring to move it away from the lock ring plate, the arbor, of which end is secured to the actuator, and in turn is secured to the lock ring, can rotate when a force is applied to it.
In use, and referring to
Again referring to
One complete turn would limit the cable payout by the circumference of cable wrapped around the reel. However, because the somewhat helical and spiral nature of a cable wrapped around a reel, this number is not a constant. In the illustrated embodiment, there are roughly 40 turns of cable on the reel body. Each ⅙th of a rotation of the quick release handle roughly translates into ⅙th of the circumference of the cable being taken up in length. Using a rough linear estimate, each revolution of the handle decreases cable length by 65/40 of 1.625 feet. However, in reality, the regression of turns to amount of cable limited would more likely resemble a logarithmic regression with a currently unknown coefficient.
As stated above, the interior 76 of the power spring 48 is connected to the arbor 28. This is best illustrated in
Referring to
When the plates are disengaged, such as through a quick release handle 66 and actuator 60 via a tensionser, such as a compression spring 58, the combined actuator/arbor 28/60 is no longer fixed to the house and may rotate or spin. Because the arbor is connected to the power spring, rotating the arbor rotates the power spring and pretensions the cable.
In the embodiment illustrated in
Another embodiment of
A second SRL embodiment 20′ of the invention is best illustrated in
As illustrated, the fittings are a spin stop fitting 100 and a spin stop nut 102 in which the exterior shape of the spin stop nut corresponds to the interior shape of the spin stop fitting. An end plate 104 and a fastener 106 abut the end of the spin stop fitting 100. The spin stop fitting 100 is affixed to the SRL housing 22 (illustrated affixed to back plate 32 through a plurality of fasteners 108). According to one aspect of the invention, the spin stop nut is a hex nut and the interior space 110 of the spin top fitting 100 is of a size and shape to receive the hex head nut and to keep it from rotational, but not lateral, movement. However, other geometrical shapes beyond a hexagonal shape may be used and the use and interchangeability of other shapes are well within the scope of one of skilled in the art.
The anterior end 110 of the fastener can abut the other end 112 of the arbor 28, which may be threaded, and can engage the spinnable threaded nut 102 as illustrated in
Because the passive restraint system functions independently of the active braking mechanism, the SRL includes both an active braking system for fall arrest and a passive fall restraint system. In use, such as illustrated in
Advantages of the present invention include having a single device that can provide both active fall arrest and a passive restraint. If the wearer is passively restrained, the wearer is that much less likely to have need for true fall arrest protection even though such protection exists in a fully functioning mode. This invention provides an additional safety feature for workers in hazardous locations. Further, the present invention allows for a single active fall arrest device that can be used in a multitude of applications as a commercialized 65′ retractable can also function as 50′ foot or less retractable by pretensioning the cable pay out to a desired length. Thus, users and contractors will not have to stock as many variations and parts and construction and maintenance companies can save on inventory costs without sacrificing on safety.
The illustrated embodiments are only examples of the present invention and, therefore, are non-limitive. It is to be understood that many changes in the particular structure, materials, and features of the invention may be made without departing from the spirit and scope of the invention. Therefore, it is the Applicants' intention that their patent rights not be limited by the particular embodiments illustrated and described herein, but rather by the following claims interpreted according to accepted doctrines of claim interpretation, including the Doctrine of Equivalents and Reversal of Parts.