Patent Grant
10004927
Not applicable.
This invention relates generally to retractable lanyards, and more particularly to a mechanical clutch locking mechanism for a retractable lanyard that is configured to further ensure that the fall arrest lanyard will not fail to lock in a fall situation even if the locking components become fouled or frozen in place.
Self-retracting lanyards (retractables) are safety devices that are designed to reduce the risks of a fall for an individual who is working at what would otherwise be dangerous or deadly heights. Each retractable comprises a cable, known as a lifeline, that is held in the retractable on a reel or drum. When the lifeline is pulled from the retractable at a relatively slow rate, such as when the user is moving about but not falling, the retractable clutch lock mechanism allows the reel or drum to rotate to unwind and the lifeline to extend from the retractable housing. However, when the lifeline is pulled from the retractable at a very rapid rate such as when a user is falling, a clutch or shock absorber or other similar clutch lock mechanism in, or associated with, the retractable reel or drum will automatically engage and slow and/or stop the reel or drum from rotating to slow or stop the unwinding of the lifeline. This halts the individual's fall after only a very brief interval.
One such retractable has an internal clutch system in which a pawl plate has a stack of friction discs on each side of a clutch plate to which the drum is connected and which can apply up to approximately 3000 pounds per square inch of compressive force to each side of the plate. This creates normal forces on friction pads that can slip under load, thus softly stopping the release of the lifeline.
Lock mechanisms for retractables also can be made in which the mechanisms that sense a fall has occurred can be activated either by sensing displacement, velocity, or acceleration. Most retractable lanyards lock up using the principal of a pivoting pawl which moves upon rotation of the drum to engage a locking wheel (commonly referred to as a sperrad) that is connected to the clutch plate.
In locking mechanisms that use “displacement,” a rotating cam engages the pawl. As the drum rotates, the cam raises and lowers the pawl into an engagement zone with the sperrad. If the drum turns fast enough (as in a fall), the cam will rotate so quickly that it will cause the pawl to leave the cam surface and rise sufficiently to engage a stationary sperrad. This stops the rotation of the drum, and causes the clutch plate to begin rotating between the friction disks, allowing for a slow deceleration and eventual stopping of the decent of the falling worker. Clutch lock mechanisms are usually designed to limit the arrest forces to 900 lbs. average (or less).
In locking mechanisms that use “velocity” to determine pawl activation, the pawl is pivotally mounted on the drum. The pawl will have a pointed end and possibly a counterweighted end. The counterweighted end may be lighter or heavier than the pointed end depending on whether the pawl swings outwardly or inwardly to engage the sperrad. The pawl is restrained from engagement with the sperrad at low rotational speed of the drum by use of a spring which keeps the pointed end of the pawl out of the sperrad's engagement zone until the drum has reached a fall arrest velocity. When that rotational velocity is reached, the pawl will swing out into the engagement zone and engage the tip of the sperrad to create lockup, and thus stop rotation of the drum.
In most retractables, when a pawl is driven using velocity (i.e., “centrifugal forces”) to engage a sperrad, under certain circumstances the pawl may not engage the sperrad, such as if the pawl is fowled with debris, or frozen (either due to ice or thermal contraction). This results in a situation in which the lanyard locking components may become frozen in a non-engaging position that can allow the lifeline to freely unwind from the lanyard drum without stopping. Should a user be attached to a lanyard in this condition and fall, the lifeline may continue to discharge to its full length, thereby causing serious injury or even death to the user. This condition can occur regardless of whether the lockup mechanisms use displacement, velocity, or acceleration to activate the pawl. It is only possible to substantially guarantee lockup between the pawl and the sperrad in mechanisms that use displacement (i.e., cam driven pawls) to drive the pawl tip into an engagement zone that is beyond the sperrad tip diameter. The spring then is used to pull the pawl tip out of the engagement zone just prior to passing the sperrad tip. This mechanism of using a cam driven pawl in which the cam pushes the pawl tip into an engagement zone creates a pawl mechanism in which nearly any failure of pawl rotational freedom guarantees lockup.
It would therefore be desirable to have a lanyard that comprises a clutch locking mechanism that allows for the proper operation of the lanyard but that will operate to stop a fall even if the clutch lock mechanism is subjected to conditions that may foul or freeze the locking components.
As will become evident, the retractable disclosed below provides benefits over the existing art. The disclosure is directed only to retractables that rely on displacement as the locking mechanism. With a displacement type of locking mechanism, a camming action is always used to move the pawl into the sperrad's engagement zone. A retraction spring is used to pull the pawl back out of the engagement zone just before passing (or being passed by) the sperrad tip or tooth. In this way, the locking mechanism is substantially “fail safe”, in that the disclosed locking mechanism will substantially ensure that the locking mechanism will result in the pawl engaging the sperrad to stop rotation of the drum during a fall. The pawl must be able to pivot freely under just the force of the retraction spring, or it cannot move out of the way of the sperrad tip. The loss of a pawl spring, contamination restricting the return rotation of the pawl or sperrad, or physical damage that restricts pawl rotation will result in lockup of the retractable. Thus, if a worker pulls on the retractable cable and it will not come out of the retractable, the retractable is informing the worker that it has internal damage. In other words, if the retractable is damaged in any way, it prevents the worker from being able to use it.
Briefly stated, a clutch lock mechanism for a retractable is disclosed. The clutch lock mechanism comprises a sperrad, at least on pawl, and a biasing member. The sperrad comprising a plurality of teeth extending from an edge of the sperrad, wherein each tooth defines an engagement pocket with the sperrad edge, the tips of the engagement teeth defining an engagement circle, and the space between the engagement circle and the sperrad edge defining an engagement zone. The at least one pawl comprises a central portion, an engagement tip extending from one side of the central portion and a trailing tip extending from an opposite side of the central portion. The pawl is pivotable about a pivot axis at the approximate center of the pawl central portion. Additionally, the pawl is substantially symmetrical about a line extending through the pivot axis from an approximate center of an inner edge of the pawl to an approximate center of an outer edge of the pawl. The at least one pawl is positioned in the retractable such that the engagement tip faces the engagement pocket of the sperrad and is pivotable between an engagement position in which the engagement tip of the pawl is in the engagement zone and an non-engagement position in which the engagement tip of the pawl is not in the engagement zone. The biasing member is operatively connected to the at least one pawl to bias the at least one pawl to the non-engagement position.
In use, the sperrad rotates about an axis relative to the at least one pawl or the at least one pawl moves circumferentially relative to the sperrad; such that as the sperrad moves relative to the at least one pawl or as the at least one pawl moves relative to the sperrad, the at least one pawl engages or is engaged by the sperrad to positively move the engagement tip into the engagement position without reliance on centrifugal forces, such that the engagement tip of the sperrad is in the engagement zone. Thus, if the sperrad and at least one pawl is moving relative to the other of the sperrad and at least one pawl greater than a predetermined speed, the engagement tip of the at least one pawl will engage the engagement pocket of the sperrad before the biasing member can return the at least one pawl to the non-engagement position.
In accordance with an aspect of the clutch lock mechanism the at least one pawl comprises a cam surface. The spring biasing the at least one pawl such that the cam surface of the at least one pawl engages the sperrad teeth. The teeth of the sperrad are shaped to move the at least one pawl from the non-engagement position to the engagement position as the sparred teeth move past the at least one pawl or as the at least one pawl moves past the sparred teeth.
In accordance with an aspect of the clutch lock mechanism, the sperrad is stationary and the at least one pawl moves circumferentially relative to the sperrad.
In accordance with an aspect of the clutch lock mechanism the biasing member urges the cam surface of the at least one pawl into engagement with the sperrad tooth.
In an embodiment with an aspect of the clutch lock mechanism, the sperrad comprises a rotatable central member and the sperrad teeth extend from an outer edge of the central member. In this embodiment, the at least one pawl is circumferentially fixed relative to the housing, and the inner edge of the pawl facing the sperrad teeth and defining a radius. The spring element biasing the at least one pawl to the engagement position in which the trailing tip is in the engagement zone. In this embodiment, when the sperrad rotates in an unwinding direction, at least one of the sperrad teeth will engage the inner edge of the at least one pawl causing the at least one pawl to pivot about its pivot axis and to move the engagement tip of the at least one pawl into the engagement zone.
In accordance with an aspect of this embodiment, the radius defined by the inner edge of the at least one pawl corresponds generally to the radius of a circle defined by tips of the sperrad teeth.
In another embodiment, the at least one pawl is mounted to a rotatable pawl plate. In this embodiment, the sperrad comprises a positionally fixed sperrad ring surrounding the pawl plate, and the sperrad teeth extend from an inner edge of the sperrad ring. Here, the pawl plate rotates relative to the sperrad ring, and hence the at least one pawl moves circumferentially, relative to the sperrad ring.
In accordance with an aspect of this embodiment, the at least one pawl is mounted to the pawl plate proximate a circle defined by the sperrad teeth. The at least one pawl has an outer edge and is biased by the spring element towards the non-engaging position, such that the outer edge of the at least one pawl faces the sperrad teeth and the trailing tip of the pawl is in the engagement zone when the at least one pawl is in the non-engagement position. In this embodiment, as the at least one pawl passes a sperrad tooth, the outer edge of the at least one pawl engages the tooth to cause the at least one pawl to move from the non-engagement position to the engagement position in which the engagement tip of the at least one pawl is in the engagement zone.
In accordance with an aspect of this embodiment the pawl plate defines at least one guide path for the at least one pawl. The guide path comprises at least one slot defining a radius. In this instance, the at least one pawl comprises a pin which is slidably received in the slot.
In accordance with an aspect of the clutch lock mechanism, the sperrad and at least one pawl are positioned relative to each other such that engagement of the sperrad with the at least one pawl urges the leading tip of the pawl outwardly, and the pawl has a length at least slightly longer than the tip distance on the sperrad teeth (i.e., the distance between the tips of adjacent sperrad teeth).
In accordance with an aspect of the clutch lock mechanism, the sperrad defines a ring surrounding the pawl plate, and the pawl plate rotates relative to the sperrad.
In accordance with an aspect of the clutch lock mechanism, the sperrad and at least one pawl are positioned relative to each other such that engagement of the sperrad with the at least one pawl urges the leading tip of the pawl inwardly. The pawl has a length less than the tip distance on the sperrad teeth (i.e., the distance between the tips of adjacent sperrad teeth). In this instance, when the sperrad is rotationally mounted in the housing, the at least one pawl is pivotally mounted in a fixed circumferential position relative to the sperrad, such that the sperrad rotates relative to the at least one pawl.
The clutch mechanism is incorporated in a housing for a retractable lifeline assembly. The housing comprises a first half and a second half which, in combination, define a drum receiving space for rotatably receiving a drum having a lifeline wound thereon. The housing defines a nozzle through which the lifeline can extend and retract and an attachment zone for connection of an anchor to the housing. The housing is made from a non-structural, lightweight material, and includes a reinforcement comprising opposed side reinforcing members, a upper reinforcement and a lower reinforcement. The side reinforcing members extend around the drum area from the nozzle to the attachment zone; the lower reinforcement surrounds the nozzle and connects bottom ends of the side reinforcing members; and the upper reinforcement connects upper ends of the side reinforcing members together and defines a passage through which a shaft of the anchor extends. The anchor further includes a stop at a bottom of the shaft sized to prevent the shaft from being pulled from the housing. The reinforcement is made from a structural material, whereby, during a fall, substantially all forces from the fall are transferred to, and carried by, the reinforcement, rather than by the housing.
The illustrative embodiments of the present invention are shown in the following drawings which form a part of the specification, in which:
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
While the invention will be described and disclosed in connection with certain preferred embodiments, the description is not intended to limit the claimed invention to the specific embodiments shown and described herein, but rather the claimed invention is intended to cover all alternative embodiments and modifications that fall within the spirit and scope of the invention as defined by the claims included herein as well as any equivalents of the disclosed and claimed invention.
A retractable 10, shown in
In the embodiment shown, the housing is made of a light-weight non-structural material, such as a plastic, to reduce the weight of the housing. The housing defines a channel around the perimeter of the housing which receives a handle-side reinforcing member 20 and a nozzle-side reinforcing member 22. The side reinforcing members 20, 22 each include an attachment area portion 20a, 22a and a perimeter portion 20b,22b. The attachment portions 20a,22a of the side reinforcing members each extend the height of the housing attachment point 16, and are positioned approximately 180° apart to be on opposite sides of the attachment point 16. The perimeter portions 20b,22b of the side reinforcing members extend from a bottom of their respective attachment portions 20a,22a around a portion of the perimeter of the housing to the nozzle 18. The two perimeter portions have ends that are opposite each other at the nozzle.
An upper reinforcement 24 comprises a pair of substantially identical facing upper reinforcement members 26, each of which comprises a U-shaped central portion 26a with a pair of arms 26b extending from the central portion 26a. The two upper reinforcement members 26 face each other, such that their respective central portions are aligned and define a generally circular passage. The arms 26b of the reinforcement members 26 are fixed to the attachment area portions 20a,22a of the reinforcement members 20,22. An anchor member 28 for the retractable includes a shaft 28a which extends through the passage defined by the upper reinforcement members 26. An eye or loop 28b secured to the top of the shaft is sized to be connected to a carabineer or the like. The anchor member further includes a stop 28c at the bottom of the shaft. This stop has a dimension greater than the diameter of the passage defined by the upper reinforcing members to prevent the shaft from being withdrawn from the housing attachment point. The stop can, for example, be a bolt which is threaded onto the shaft, one or more pins which extend through the shaft, or a plate which is fixed to, or formed as part of, the shaft. Additionally, the housing includes lower reinforcing members 29 which extend around the nozzle and connect the lower ends of the side reinforcing members 20,22. As can be appreciated, the reinforcing members 20, 22, 26, and 29 defines a reinforcement that extends fully around the housing. The housing, as noted above, is made from a light-weight, non-structural material, such as plastic. The reinforcing members, on the other hand, are made from a structural material, such as steel. The reinforcing members can, for example, be up to ⅛″ thick. In a normal fall situation, the forces of the fall will be borne or carried by the plastic housing. However, should the housing be cracked or damaged, any forces not capable of being carried by the housing will be borne by the reinforcing members 20, 22, 26 and 29. This allows for the housing itself to be made from a light-weight, non-structural material, such as plastic without fear of catastrophic failure. In the event of a failure of the structural integrity of the plastic housing, the metal reinforcing members will prevent the cable and drum from disconnecting from the anchor support.
The lock mechanism 30 for the retractable is contained within a housing 12, as noted above. In this embodiment, the lock mechanism includes a stationary sperrad ring 32 positionally fixed in the housing and a rotatable pawl plate 40 having pivotable pawls 44 mounted thereon. The pawl plate with the pivotable pawls rotates in the housing relative to the sperrad ring 32. The sperrad ring 32 includes a plurality of inwardly directed teeth 34 evenly spaced about an inner edge of the sperrad ring. Twelve teeth 34 are shown, but more or fewer could be provided if desired. The teeth do not extend radially inwardly. Rather, the teeth face or point in a clock-wise direction (with reference to
The pawl plate 40 is operatively connected to the cable drum to rotate in the housing around an axle 41. The pawl plate is concentric with the sperrad ring 32. The pawl plate 40 is free to rotate at least in the direction of the arrow A. The pawl plate 40 has a diameter at least as large as the diameter of the circle E to enable the locking pawls 44 to be mounted near the edge E of the engagement zone EZ. In
A spring 51 (only one spring is shown in
The symmetry of the pawl allows for the pawl to be generally equally balanced centrifugally. Since in this embodiment, the pawl pivots about the pin 52, any imbalance would overcome the pawl spring and cause the pawl to either lock too early or too late.
In operation, the pawl plate 40 will rotate with the drum in a direction toward the sperrad teeth 34 when the lifeline is being extended or withdrawn from the housing 12. With reference to
In non-emergency situations (such as when a worker is walking and extending the lifeline), the pawl plate 40 is rotating at a speed that will allow for the spring 51 to pivot the pawl 44 to a non-engaging position wherein the tip of the leading wing is not in the engagement zone. However, during a fall, the pawl plate is rotating more quickly because the lifeline is being pulled out quickly. In this instance, the engagement tip of the leading wing 44b will rise up and, due to rotational momentum, dwell long enough in the engagement zone EZ to engage the pocket 36 of a sperrad tooth 34 before the spring can move the pawl 44 to the non-engaging position.
An alternative lock mechanism is shown in
A plurality of pawls 112 are mounted in the housing 101 to pivot about a pivot axis defined by a pawl pin 116 outside of the circle E. The pawls 112 are evenly spaced about the sperrad. The clutch lock mechanism 100 is shown to have to have three pawls (i.e., one-half the number of sperrad teeth), but could have more or fewer pawls if desired. Each pawl has an inner edge 112a, a first side edge 112b, and a second side edge 112c. The inner edge 112a is convex, and the side edges 112b,c are both slightly convex to meet at an apex 113. Thus, the pawls are generally triangularly shaped with a radiused concave base (inner edge 112a) and slightly convex legs (side edges 112b,c). The junction of the first side edge 112b with the inner edge 112a defines a leading or engaging tip 128 of the pawl; and the junction of the second side edge 112c with the inner edge 112a defines a trailing or cam tip 130. The sides 112b,c are of substantially equal length, such that a triangle defined by the apex and the leading and trailing tips is substantially an isosceles triangle, and so that the apex 113 is located approximately midway between the leading and trailing tips 128, 130. The pawl is thus substantially symmetrical about a line extending through the pivot point from the approximate middle of the bottom edge 112a to the apex 113. This keeps the pawl centrifugally balanced so that it does not imbalance the loads on the pawl spring 150. The pawl is pivotally mounted to the pivot pin in the area between the apex 113 and the inner edge 112a, such that movement of one tip in one direction causes the same amount movement of the other tip in the opposite direction. Finally, the radius defined by the curvature of the inner edge 112a is substantially equal to the radius of the circle E. Additionally, the pawl is positioned such that a point of the inner edge 112a of the pawl directly below the apex 113 is substantially on the circle E, such that the center of the pawl inner edge is just slightly above the circle defined by the sperrad teeth.
The pawls 118 and the sperrad 112 are mounted in the housing to be substantially co-planar. A spring 150 is associated with each pawl 112 to urge the trailing tip 130 of the pawl into engagement with the side edge or surface of the sperrad. This allows the sperrad to not only provide an engagement tip, but also allows the sperrad to act as a cam surface to drive the pawl. The springs 150 are shown to be torsion springs, with one end connected to the housing and the other end connected to the pawl in the vicinity of the trailing tip 130. The torsion springs thus operate to positively push (rather than pull) the trailing tip 130 into engagement with the surface of the sperrad. As can be appreciated, other types of spring elements could be used. For example, compression springs, torsion springs, tension springs or leaf springs could be used. Alternatively, the springs could be replaced with a biasing element (such as an appropriately designed pad) which would operate to push the trailing end 130 of the pawl 112 into engagement with the edge of the sperrad 112.
The two lock mechanisms are each shown with three pawls, but different numbers of teeth. The number of pawls could be changed if desired. At a minimum, there must be one pawl. The maximum number of pawls, at a maximum capacity, could equal to one-half the number of sperrad teeth. Thus, the maximum number of pawls for the locking mechanism of
For all pawl mechanisms, a spring must be used to bias the pawl's trailing edge against the surface of the sperrad so that the sperrad may act as a cam to drive the displacement (pivoting) of the pawl. This spring type in most designs is a typical coiled tension spring. The tension spring is prestressed by mounting it to a screw or post that is located some distance from the pawl. The lock mechanism of
For this reason, an improved spring method is used on the retractable of
Because the spring 150 biases the trailing end 130 of the pawl against the edge of the sperrad 118, the inner edge 112a of the pawls face generally towards the sperrad teeth 120 (as can be seen with the bottom two pawls in
This operation of the locking mechanism 100 is demonstrated in
As with the locking mechanism 30 (
In both lock mechanisms 30 and 100, the size (strength) of the spring, the width of the pawl and the distance between on tooth tip (or root) and the preceding tooth tip (or root) are selected such that during normal (non-emergency) operation, the spring can pivot the engaging end of the pawl out of the engagement zone before a sperrad tooth engages the pawl engagement tip. Further, because the pawl is pivoted into the engagement zone by its engagement with the sperrad, the locking mechanisms 30, 100 positively moves the pawl engagement tip via a camming action into the engagement zone EZ of the sperrad. The locking mechanisms thus do not need to rely upon centrifugal forces to urge the pawl engagement tip into the engagement zone, as occurs with many currently available clutch lock mechanisms. Additionally, should the pawl become locked-up or otherwise frozen in position, operation of the lanyard will be prevented, and the user will know that the lanyard should not be used. This is especially true if the pawl is locked in the engagement position of the top pawl in
The pawls 44, 112 of the lock mechanisms 30, 100 are symmetrical about an axis extending through their pivot axes from their bottom edges to their top edges. Thus, the opposite ends of the pawls are substantially identical in three dimensions (i.e., width, length, and height), and thus have substantially similar weights. This substantial identically (or mirror image-ness) of the opposed wings of the pawls substantially reduces, if not eliminates, the impact of any centrifugal forces upon the pawls. Thus, the lock mechanisms 30, 100 do not rely upon centrifugal forces to move the engagement tips of the pawls into the engagement zone. Rather, the contact or interaction between the sperrad (or sperrad ring) and the pawls substantially ensures that the engagement tip of the pawl is in the engagement zone, to substantially ensure that a sperrad tooth will engage the engagement tip of a pawl (or vice versa) to stop rotation of the retractable during a fall.
While we have described in the detailed description multiple configurations that may be encompassed within the disclosed embodiments of this invention, numerous other alternative configurations, that would now be apparent to one of ordinary skill in the art, may be designed and constructed within the bounds of our invention as set forth in the claims.
For example, the sperrad teeth need not be shaped as shown, but may be any variety of differing shapes so long as they properly interact with the engagement tips of the pawls. Still further, the clutch lock mechanism need not have exactly three pawls, but may have a single pawl or many more than three, again, so long as the pawls enable the clutch lock mechanism to operate as described herein. Also, the sperrad is not restricted to having a set of exactly six teeth at uniform intervals, nor that the teeth must all be of uniform shape and size and uniformly oriented in the same rotational direction. Rather, there may be more or less than six teeth on the sperrad 18, and the teeth 20 may be of varying sizes and shapes, so long as they properly operate as part of the clutch lock mechanism as outlined in this disclosure. In fact, the sperrad ring 32 (
Additional variations or modifications to the configuration of the clutch lock mechanism of the present invention, may occur to those skilled in the art upon reviewing the subject matter of this invention. Such variations, if within the spirit of this disclosure, are intended to be encompassed within the scope of this invention. The description of the embodiments as set forth herein, and as shown in the drawings, is provided for illustrative purposes only and, unless otherwise expressly set forth, is not intended to limit the scope of the claims, which set forth the metes and bounds of my invention.
This application claims priority to U.S. App. No. 62/168,106 filed May 29, 2015, entitled “Retractable Lanyard Lock Mechanism.” In addition, this application is related to application Ser. No. 14/094,422 filed Dec. 2, 2013 which claims priority to U.S. App. No. 61/738,981 filed Dec. 18, 2012, and U.S. App. No. 61/732,400 filed Dec. 2, 2012. All of said applications are incorporated herein by reference.
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| 20140151155 | Choate | Jun 2014 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20160346572 A1 | Dec 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62168106 | May 2015 | US |
