Retractable safety cage

[0002] This application claims priority to U.S. Provisional Application Serial No. 60/235,949, filed Sep. 26, 2000.

[0003] The present invention relates generally to safety cages for ladders. More particularly, the invention relates to a slideably retractable safety cage enclosure that can be mounted either to the ladder itself or a wall, and can provide a safety enclosure around the top of the ladder to prevent passersby from falling in near the opening.

[0004] Fixed ladders find wide utility throughout industry, generally in permanent installations where periodic access to a different level is required for the purposes of maintenance, equipment operation, equipment inspection, or the like. Such fixed ladders are most often used in situations where sufficient lateral space is not available to enable the use of more conventional stairways, or where the frequency or type of use does not economically dictate employment of these more conventional stairways. Fixed ladders find particular applicability when mounted on the side of manholes or other vertical tunnels; to the exterior or interior of fluid containing tanks; or to the exterior or interior of buildings, towers, or other set structures. Manhole ladders that are permanently fixed to the inside wall of a manhole are typically wholly located within the manhole below its upper rim so that the manhole entrance can be covered with a manhole plate or grate. The fact that the ladder does not extend above the manhole entrance makes it difficult for a user to mount and dismount the top end of the ladder. Therefore, the manhole user must support and balance himself from the rim of the manhole during entry until his body is almost entirely within the manhole. Only then can the user grasp the top rung of the manhole ladder. This safety problem occurs upon exiting the manhole as well. This entry and exit situation is dangerous since users can slip and fall during these maneuvers. This danger is augmented in normal operation when the user must carry tools, equipment, and the like into and out of the manhole.

[0005] A further complication of these types of fixed ladders is that when the manhole opening is uncovered for use of the ladder, the opening itself presents a danger to anyone in the vicinity. In particular, the result of the typical manhole design is that when the cover is open, the hole is completely exposed and presents a fall hazard for passersby. For safety purposes, users typically must place some sort of warning sign or barricade, or must rope off the opening to alert persons in the vicinity that such fall hazard exists.

[0006] Several prior art devices have attempted to solve some of the many problems inherent in manhole design. The majority of the prior art devices have addressed the safety issues related to the ladder user, while failing to address the safety issues related to the manhole opening. In general, some of these devices provide a rail or auxiliary support that is extendable from the ladder so that the ladder user can grasp this extended rail, thus improving his balance and stability while entering and exiting the manhole. These prior art devices, while perhaps assisting the ladder user, have proven to be cumbersome, complicated to use, and time-consuming. In addition, these devices often defeat the purpose of fixed vertical ladders in that the safety devices have fixed, vertically-extending members that, when retracted, occupy an inordinate amount of space near the upper end of the manhole ladder within the manhole. This arrangement impedes user operation and versatility of the manhole. Furthermore, many manholes simply do not have the space required of the extendable supports of the prior art devices. In addition, many entities (for instance, cities, municipalities, industrial work sites, and so forth) own so many manholes that they choose not to purchase prior art safety cages as a result of the extreme costs involved in purchasing a separate safety cage for each and every manhole.

[0007] In short, prior art devices have failed to address the needs of both the ladder user and persons in the vicinity of the ladder or manhole opening. In particular, prior art devices do not adequately provide both an extendable safety support for the ladder user and a retractable safety cage that provides an adequate enclosure around the opening to prevent accidental falling into the opening. And, prior art devices have not provided a safety cage that can be completely, but easily, removed from the manhole.

[0008] As a result, there is a need for a retractable safety cage device that provides adequate safety support for a user entering and exiting a ladder opening, while at the same time providing a safety enclosure for completely protecting the opening of the manhole, thus providing safety for all persons in the vicinity. There is a further need for such a device that can accomplish these goals while at the same time being mountable on either the ladder itself or the vertical wall, and which does not block or impede the ladder entrance or the space surrounding the top of the ladder. And, there is a need for a safety cage that can be removed from the manhole so that one cage can be employed in numerous manholes that are fitted with the guide bracket.

[0009] Accordingly, the present invention is directed to a retractable safety cage device that is mounted on or near the top of a ladder and provides an extendable support for the ladder user, as well as a retractable safety cage to protect the opening near the top of the ladder. The device is mounted either on the ladder or on a structure near the ladder and does not block or impede the space near the top of the ladder in either its extended or retracted position. The invention is usable not only in ladder applications, but also in access holes and access ports that have no ladder therein. An example of such a situation is a subsurface observation port, for instance a maintenance pit observation port, and other ports where, for safety reasons, persons are not allowed inside the pit while the subterranean machinery is in operation. Other pits that find use for the invention are pits containing hazardous materials, drive motors, rotating machinery, and so forth where persons must be able to view the machinery from above the surface of the pit without physically descending into the pit. In such situations, the need exists for a retractable safety cage that, in its extended position, provides a safety enclosure around the opening to prevent persons from falling into the pit. Additionally, the device has the ability to be retractable in a permanent installation or in a removable installation, depending on the needs of the user.

[0010] A retractable safety cage for mounting on a wall or a ladder is provided comprising one or more adjustable guide brackets attached to either the wall or the ladder wherein the guide brackets have a portion containing a sleeve through which a rail can slide. At least two main, typically vertical, rails each having a proximal end and a distal end are slideably mounted within the sleeves of the adjustable guide brackets for sliding between a retracted position and an extended position. A locking mechanism is further provided that can releasably lock the retractable safety cage in either the extended or the retracted position. Furthermore, one or more counterbalances are provided that provide a bias force in the direction of the extended position of the retractable safety cage. In addition, a fixed first periphery rail having a first end and a second end each connected to the proximal end of the main rails, is attached to the main rails.

[0011] The teachings of the present invention can be readily understood by considering the following detailed description of the preferred embodiment in conjunction with the accompanying drawings, in which:

[0012] FIG. 1 is a perspective view of a rectactable safety cage in the extended position, according to an embodiment of the invention;

[0013] FIG. 2 is a side elevation partial cutaway view of a retractable safety cage in the extended position, according to an embodiment of the invention;

[0014] FIG. 3 is a front elevation view of a retractable safety cage in the extended position, according to an embodiment of the invention;

[0015] FIG. 4 is a front elevation view of a retractable safety cage in the retracted position, according to an embodiment of the invention;

[0016] FIG. 5ais a side elevation view of a main rail according to an embodiment of the present invention;

[0017] FIG. 5bis a front elevation of the main rail of FIG. 5a;

[0018] FIG. 6ais a side elevation view of a guide bracket according to an embodiment of the invention;

[0019] FIG. 6bis a top plan view of the guide bracket of FIG. 6a;

[0020] FIG. 7ais a side elevation view of a guide bracket and coupling foot assembly according to an embodiment of the invention;

[0021] FIG. 7bis a partial cutaway side elevation view of the guide bracket of FIG. 7a;

[0022] FIG. 8ais a top plan view of an alternative embodiment of the guide bracket according to the invention;

[0023] FIG. 8bis a side elevation view of the guide bracket of FIG. 8a;

[0024] FIG. 9 is a side perspective view of the coupling foot according to the preferred embodiment;

[0025] FIG. 10ais a side elevation view of the releasable locking mechanism according to preferred embodiment;

[0026] FIG. 10bis a front elevation view of the releasable locking mechanism of FIG. 10a;

[0027] FIG. 11ais a top view of a fixed top rail according to an embodiment of the invention;

[0028] FIG. 11bis a top view of a support plate of the fixed top rail of FIG. 11a;

[0029] FIG. 11cis a top view of a mounting bracket according to an embodiment of the invention;

[0030] FIG. 11dis a front elevation view of the mounting bracket of FIG. 11c;

[0031] FIG. 12ais a top plan view of a retractable safety cage according to an alternative embodiment wherein front portion is a solid rigidly attached member;

[0032] FIG. 12bis a front elevation view of the retractable safety cage of FIG. 12a;

[0033] FIG. 13ais a top plan view of a floating periphery rail according to an embodiment of the invention;

[0034] FIG. 13bis a top view of a support plate of the fixed top rail of FIG. 13a;

[0035] FIG. 13cis a is a perspective view of a bushing for the floating rail of FIG. 13a;

[0036] FIG. 13dis a top view of a collar for the periphery rail of FIG. 13a;

[0037] FIG. 14 is a side elevation view of the adjustable guide bracket and releasable locking mechanism according to an alternative embodiment of the invention;

[0038] FIG. 15 is a side elevation view of an optional emergency egress frame for mounting on the retractable safety cage according to an alternative embodiment of the invention; and

[0039] FIG. 16 is a front elevation view of the optional emergency egress frame of FIG. 15.

[0040] While the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which particular embodiments and methods are shown, it is to be understood from the outset that persons of ordinary skill in the art may modify the invention herein described while achieving the functions and results of this invention. Accordingly, the descriptions which follow are to be understood as illustrative and exemplary of specific embodiments within the broad scope of the present invention and not as limiting the scope of the invention.

[0041] FIG. 1 depicts a typical installation of a retractable safety cage 10 of the present invention. Although the invention is useable in many applications and for many different types of ladders, the common manhole application is depicted in the drawings for ease of discussion. In the typical scenario, a manhole 11 comprises a front face 12, a rear face 13, and at least two side faces, 14, 15. Typically, a manhole ladder 16 is attached in some means to the front face 12 of the manhole 11. The manhole ladder 16 further comprises a plurality of rungs 17, which are typically horizontally disposed, and at least two rails 18 which are typically substantially vertically disposed. The manhole 11 is usually fitted with a manhole cover 19 that prevents persons from falling into the manhole 11 when the manhole ladder 16 is not in use.

[0042] FIGS. 1-4 depict a retractable safety cage 10 according to a preferred embodiment of the present invention. In FIGS. 1, 2, and 3, the safety cage 10 is shown in its extended position, and comprises slideable or extendable main rails 20, 80 that are slideably received in guide brackets 30, 38. Guide brackets 30, 38 are connected, depending upon the design of the manhole 11, either to the manhole ladder 16 or the front face 12 within the manhole 11. In the preferred embodiment, main rails 20, 80 are substantially identical, one being a left main rail 20 and one being a right main rail 80, both of which are substantially vertically disposed. As a result, for the sake of brevity, only one main rail 20 will be further described herein, it being understood that similar structural elements are present on both main rails. Similarly, guide bracket 30 and 38 of the preferred embodiment are substantially identical in structure, with the exception of one being designed for the left main rail 20 and one being designed for the right main rail 80. As a result, for the sake of brevity, only guide bracket 30 will be further described, it being understood that guide bracket 38 comprises similar structure.

[0043] Referring to the Figures it can be seen that main rail 20 has a proximal end 21 and a distal end 22. The distal end 22 of the main rail 20 preferably has an opening 24 for receiving a retaining pin 160 (to be described below) when the retractable safety cage 10 is in its extended position. Similarly, the proximal end 21 of the main rail 20 may optionally have an opening 23 for receiving the retaining pin 160 when the retractable safety cage 10 is in its retracted position. The main rail 20 further comprises a first side 25, a second side 26 opposite said first side 25, a third side 27, and a fourth side 28 opposite said third side 27 all of which define an interior space 29 within the main rail 20. In the preferred embodiment, the third side 27 of the main rail 20 near the distal end 22 is swaged or bent inward toward the interior space 29, best shown in FIG. 9. This creates a sort of ramping effect that guides the retaining pin 160 into the opening 24. Many materials are suitable for the main rail 20 including, but not limited to pipe, square tube, rectangular tube, angle iron, or flat iron, all of which can be made from various materials such as stainless steels, mild carbon steels, high tensile strength steels, non-sparking metals, aluminum, titanium, high strength plastic, and basically any other materials capable of withstanding the loads applied. In the preferred embodiment, the main rail 20 is made from standard 1×2 inch thin walled (14 gauge) carbon steel tubing in any length. Typical lengths, however, are approximately 30 to 70 inches, depending upon the application. The main rail 20 obviously must be long enough so that when the retractable safety cage 10 is in its fully extended position, the retractable safety cage 10 is located at the desired height above the surface. Therefore, the greater the desired height above the surface, the longer the main rail 20. In the preferred embodiment, the main rail 20 is approximately 55 inches long.

[0044] Referring to FIGS. 1-3, and 6, a guide bracket 30 having a proximal end 350 and a distal end 351 is mounted either to the top portion of ladder rails 18 or to the front face 12 of the manhole 11. Guide bracket 30 preferably comprises a slide housing 31 attached to one or more guide bracket extensions 32. The slide housing 31 is a tubular or other generalized cylindrical or body having a first side 310, a second side 311 opposite said first side 310, a third side 312 and a fourth side 313 opposite said third side 312, all of which define an interior space 314 extending through the slide housing 31. The third side 312 further comprises at least one opening 35 therethrough that receives a retaining pin 160. The opening 35 aligns with the opening 24 in the distal end 22 of the main rail 20 when the retractable safety cage 10 is in its extended position. Similarly, the opening 35 in the slide housing 31 aligns with the opening 23 in the proximal end 21 of the main rail 20 when the retractable safety cage 10 is in its retracted position.

[0045] Referring to FIGS. 6 and 7, guide bracket extensions 32 are preferably elongated plate-like members. In the preferred embodiment, guide bracket extension 32 further comprises a mounting plate 70 for receiving a counterbalance 60, as shown in FIG. 7. The guide bracket extension 32 has a length, L, that provides adjustability in the mounting location. The guide bracket extension 32 optionally can have a plurality of openings 33 therethrough at spaced-apart intervals. These openings 33 receive fasteners that connect the guide bracket 30 to the ladder rail 18 (or, alternatively, to the front face 12). The length L, and optionally the plurality of openings 33, allows adjustability in the positioning of guide bracket 30, and therefore positioning of the retractable safety cage 10 (as will be more fully described below).

[0046] In use, the slide housing 31 slideably receives the main rail 20 so that main rail 20 is slideable from a retracted position (wherein the proximal end 21 of the main rail 20 is located near the top of the manhole ladder 16 and below the manhole cover 19), and an extended position (wherein the distal end 22 of the main rail 20 is located near the top of the manhole ladder 16 and the proximal end 21 of the main rail 20 extends above the manhole cover 19).

[0047] Preferably, slide housing 31 is a tubular member that contains therein a bushing 39 made from a variety of materials such as polymers, composites, ceramics, or glasses, or other material with low coefficient of friction to facilitate movement of the main rail 20 within the slide housing 31. Sample materials that could be used include, but are not limited to, the following: linear polymers such as polyethylene, polypropylene, polytetrafluoroethylene, polystyrene, polyvinylchloride, polymethylmethacrylate and nylon; cross-linked polymers including polyesters and formaldehyde-based plastics; and composites of carbon, cellulose, and glass; to name but a few. The preferred material is nylon. In the preferred embodiment, bushing 39 comprises two substantially L-shaped longitudinal nylon members having an external lip 81 at both its proximal end 82 and its distal end 83, as shown in FIG. 8. Bushings 39 are designed such that their length between each external lip 81 corresponds to the length of the slide housing 31. The external lip 81 on the proximal end 82 and distal end 83 retains the bushings 39 within the slide housing 31. Because the preferred bushings 39 are substantially L-shaped, when they are fitted within the slide housing 31 they provide a substantially rectangular inner surface 84 through which the main rail 20 slides, as best shown in FIGS. 6, 7 and 8. The opening 35 in the slide housing 31 is collinear with an opening 390 in the bushing 39 to allow the retaining pin 160 to protrude through both the slide housing 31 and the bushing 39 when the retaining pin 160 is engaged.

[0048] In the most preferred embodiment, the retractable safety cage 10 is not only slideably retractable, but is also easily removable from the manhole 11. This is achieved by additional structure coupled to the distal end 22 of the main rail 20, as will now be described. In this preferred embodiment shown in FIGS. 7 and 9, the guide bracket 30 further comprises a foot 90 comprising a stop 100, a rail extension 110, and at least one longitudinally extending tab 120. The foot 90 serves to couple the retractable safety cage 10 to the guide bracket 30 so that the cage 10 can be completely removed from the guide bracket 30. This results in the foot 90 and the main rail 20 sliding as one unit with little or no relative movement therebetween. Embodiments that are retractable but not completely removable comprise a guide bracket 30 that does not contain foot 90, such as the guide bracket 30 shown in FIG. 6.

[0049] The rail extension 110 is preferably made from the same material as that of the main rail 20. The rail extension 110 has a proximal end 111 and a distal end 112, and a first side 113, a second opposite side 114, a third side 115, and a fourth side 116 which, together, define an inner surface 117. The distal end 112 of the rail extension 110 is fixedly attached to the stop 100, preferably by welding or similar technique. The stop 100 further comprises a protrusion 101 extending a predetermined distance away from the second side 114 of the rail extension 110, and a portion 102 that extends longitudinally toward the proximal end 111 of the rail extension 110. A through-hole 103 is located in the portion 102 and receives a hook that is connected to a strap 61 of a counterbalance 60 (to be described below). The proximal end 111 of the rail extension 110 is preferably open in order to receive the tab 120. The tab 120 is fixedly attached to the inner surface 117 of the rail extension 110 and extends longitudinally outwardly from the proximal end 111 of the rail extension 110. The tab 120 is insertable into the interior space 29 of the distal end 22 of the main rail 20. The distance that the tab 120 extends outwardly from the distal end 112 of the rail extension 110 is variable, but should at least be great enough so as to create a secure coupling when the distal end 22 of the main rail 20 is fitted onto the tab 120. This minimum distance is approximately 2 inches. In the preferred embodiment, this distance is approximately 3 inches. However, it may be beneficial to manufacture the tab 120 so that it protrudes outwardly from the proximal end 350 of the guide bracket 30. In the preferred embodiment, this would render the tab 120 approximately 4 inches to 10 inches in length, depending on the length of the slide housing 31 and the rail extension 110. In this situation, the tab 120 provides a convenient and effective guide for an operator to manually place the main rail 20 of a removable retractable safety cage 10 onto the foot 90, thereby slideably and removably attaching the cage 10 to the guide bracket 30. It should be noted that an equivalent means of coupling the foot 90 to the main rail 20 could be made by placing the tab 120 at the distal end 22 of the main rail 20, and have the tab 120 removably fit within the inner surface 117 of the rail extension. Any form of male/female fittings known in the art may work.

[0050] A releasable locking mechanism 130 is mounted on the third side 312 of the slide housing 31, preferably toward the distal end 351 thereof. Obviously many designs for the releasable locking mechanism 130 are possible, it being the goal of providing a releasable latch mechanism that can engage and disengage the main rail 20. To name but a few examples, cotter pins, keys, spring pins, sliding latches, pins with ball detents, and many other common forms of latches could be used. Indeed, FIG. 14 depicts an alternative embodiment of the retaining pin assembly 130 comprising a lever 131 having a proximal end 132 and a distal end 133. The distal end 133 is pivotally connected to a retaining arm 134 having a substantially trapezoidal shape. The retaining arm 134 is pivotally connected to the guide bracket 30 at pivot 135. When a user desires to retract the retractable safety cage 10, he simply pulls the distal end 132 of the lever 131, thereby making retaining arm 134 pivot about pivot 135 and removing the portion of retaining arm 134 that blocks the distal end 352 of the slide housing 31. This allows the main rail 20 to move from its extended position to its retracted position. Referring to FIG. 10, the releasable locking mechanism 130 of the preferred embodiment is shown, and further comprises a fulcrum 140, a lever 150, a retaining pin 160, and a spring 170. The fulcrum 140 comprises a base 141 that is fixed, preferably welded, to the guide bracket 30, and a free end 142 that extends in a radial direction outwardly from the guide bracket 30. The lever 150 is pivotally attached to the free end 142 of the fulcrum 140, and further comprises a handle portion 151 disposed opposite a pin portion 152. The retaining pin 160 has a fixed end 161 and, an engaging end 162. The pin portion 152 of the lever 150 is fixed to the fixed end 161 of the retaining pin 160. The spring 170 is mounted on the slide housing 31 beneath the handle portion 151 of the lever 150 so as to provide a spring bias force in a direction that tends to force the engaging end 162 of the retaining pin 160 farther into the interior space 29 of the main rail 20.

[0051] As a result, the retaining pin 160 may be inserted through the opening 35 in the slide housing 31 and through the opening 24 in the distal end 22 of the main rail 20 when the retractable safety cage 10 is in its extended position, thus locking the retractable safety cage 10 in its extended position (FIG. 2). Likewise, the retaining pin 160 may be inserted through the opening 35 in the slide housing 31 as well as through the opening 23 in the proximal end 21 of the main rail 20 when the retractable safety cage 10 is in its retracted position, thus locking the retractable safety cage 10 in its retracted position (FIG. 4). The materials that are suitable for the main rail 20 are also suitable for the guide bracket 30. In the preferred embodiment, the slide housing 31 is made from standard 1½×2½ inch thin-walled (14 gauge) steel tubing approximately 7½ inches in length. Attached thereto are the guide bracket extensions 32 that are made from ¼×2×7¼ inch plate steel.

[0052] Referring now to FIGS. 1 and 11, a first periphery rail 40 is affixed to the proximal end 21 of the main rail 20, and is preferably horizontally disposed. The method of fixation can be any of a number of methods suitable for the materials employed in the retractable safety cage 10, including, but not limited to, welding, bolting, other threaded connections, geometric connections (that is, containing mating male and female geometric shapes) and so forth. FIG. 11 depicts a mounting bracket 45 that is welded to the first periphery rail 40 and comprises openings 47 therethrough for bolting the first periphery rail 40 to the main rail 20. First periphery rail 40 preferably comprises at least a back portion 41 and two side portions 42, 43, thus creating a peripheral enclosure having at least three sides (that is, enclosing approximately 270° of the opening). The side portions 42, 43 are spaced apart preferably at least 23 inches to accommodate stretchers and other devices that often need to be placed in the manhole 11. Because standard manhole ladders 16 are typically only 18 inches wide, it can be seen that the first periphery rail 40 creates a perimeter that is larger than typical prior art ladder extensions that merely extend the ladder rails 18. The preferred three-sided periphery provides not only support for the ladder user for entering and exiting the manhole 11, but also provides a peripheral safety cage that substantially surrounds the opening of the manhole 11, thus providing a safety barrier therearound. An optional front portion 44 can also be employed to provide a four-sided, or approximately 360° enclosure. However, when the optional front portion 44 is employed, some means of opening and closing the front portion 44 must be utilized if the retractable safety cage is used for a manhole 11 having a ladder 16. Examples of such opening and closing means could include hinged connections, slideable connections, retractable connections, or removable pieces that must be removed and separately stored. The preferred embodiment does not utilize the optional front portion 44. FIG. 3 shows a retractable safety cage 10 wherein front portion 44 is a chain. FIG. 12 shows a retractable safety cage 10 wherein front portion 44 is a solid, rigidly attached member for applications requiring only visual access to subterranean areas.

[0053] The retractable safety cage 10 is designed such that when it is in its extended position, the first periphery rail 40 is situated above the surface of the ground in the typical manhole application at heights that are approved by local, state, or federal safety regulations (such as OSHA). In the preferred embodiment, when the retractable safety cage 10 is in its extended position, the first periphery rail 40 is situated approximately 39 to 42 inches above the surface. Basically, the same materials that are suitable for the main rail 20 are also suitable for the first periphery rail 40. Anticipated applied loads include the dead weight of the cage 10 plus the weight of a ladder user suspending himself from the first periphery rail 40. In the preferred embodiment, the first periphery rail is made from standard 1×2 inch thin-walled (14 gauge) steel tubing. This material provides both a good welding material as well as a material that is suitable for bolted connections.

[0054] Referring now to FIGS. 1 and 13, at least one floating periphery rail 50 is slideably received on the main rail 20. The floating periphery rail 50 preferably has the same shape as the first periphery rail 40. Namely, floating periphery rail 50 preferably comprises a back portion 51 and at least two side portions 52, 53. It should be stated at this point, however, that the actual geometric shape of the first periphery rail 40 and the floating periphery rail 50 is a matter of design choice dependent in part on the shape of the manhole 11, it being more important that the shape provide a perimeter enclosure about substantially all sides (for example, at least approximately 270°) of the manhole 11 opening, and yet still provides sufficient space for inserting things into the manhole 11. In other words, the first periphery rail 40 and the floating periphery rail(s) 50 may take a substantially circular shape or any substantially polygonal shape, to state but a few examples. The floating periphery rail 50 has a collar 54 that slideably receives the main rail 20. As with the slide housing 31, the collar 54 preferably has a bushing 55, of similar material as that of bushing 39 that facilitates slideable movement along a length of the main rail 20. The preferred bushing 55 is made of nylon.

[0055] Basically, the same materials that are suitable for the first periphery rail 40 are also suitable for the first periphery rail 50. Anticipated applied loads include the dead weight of the cage 10 plus the weight of a ladder user suspending himself from the first periphery rail 50. In the preferred embodiment, the first periphery rail is made from standard 1×2 inch thin-walled (14 gauge) steel tubing. This material provides both a good welding material as well as a material that is suitable for bolted connections.

[0056] Referring again to FIGS. 1, 11 and 13, floating periphery rail 50 is connected to the first periphery rail 40 so that when the retractable safety cage 10 is in its extended position, the floating periphery rail 50 slides to a preselected distance from the first periphery rail 40. In the preferred embodiment this is achieved by attaching non-rigid connectors 56 to both the first periphery rail 40 and the floating periphery rail 50. In the preferred embodiment, the connectors 56 comprise chains that are coupled to eye bolts and support plates 46, 57 connected to the first periphery rail 40 and the second periphery rail 50 respectively. As the retractable safety cage 10 is moved from its extended position to its retracted position, the non-rigid connectors 56 allow the floating periphery rail 50 to slide closer to the first periphery rail 40. This arrangement occupies a minimum amount of space and therefore is suited for manholes 11 that have appurtenances or the like near the manhole opening that would prohibit the use of prior art extending devices. In particular, as best shown in FIG. 4, the horizontal disposition of the first periphery rail 40 and the floating periphery rail 50 allows the retractable safety cage 10 to be installed in manholes 11 having very little vertical clearance between the top of the manhole 11 and other structures that may be in the vicinity of the upper regions of the manhole ladder 16. Many other alternative non-rigid connectors 56 are possible, including but not limited to cables, straps, ropes, telescoping members, sliding diagonal members, and so forth. Again, referring to FIG. 4, by using non-rigid connectors 56, when the retractable safety cage 10 is in its fully retracted position, the floating periphery rail 50 rests in close proximity to the underside of the first periphery rail 40. By contrast, referring to FIGS. 1-3, when the retractable safety cage 10 is in its fully extended position, the floating periphery rail 50 drops to a position below the first periphery rail 40, wherein this position is located at a distance below the first periphery rail 40 that is equal to the length of the non-rigid connectors 56 and the eye bolts connected to both the first periphery rail 40 and the floating periphery rail 50.

[0057] In an alternative embodiment, floating periphery rail 50 may be rigidly attached to the first periphery rail 40 by using rigid connectors 56 and omitting the collar 54. Because this embodiment requires greater space near the upper region of the manhole ladder 16 this embodiment is not preferred.

[0058] Referring again to the Figures, the preferred embodiment of the retractable safety cage 10 further comprises at least one counterbalance 60 that is mounted on the mounting bracket 70 on the guide bracket extension 32 near the distal end 22 of the main rail 20. The counterbalance 60 can be any standard spring, pneumatic, or hydraulic balancing or return mechanism standard in the mechanical industry. In the preferred embodiment, the counterbalance 60 is a spring counterbalance having a pressed steel casing that encloses a type 304 stainless steel tape 61 which is wound on a removable drum. A steel spring holds the tape 61 with uniform tension, and the mechanism is permanently greased inside and zinc coated outside. Depending on the length of travel needed between the extended position and the retracted position, the preferred spring counterbalance 60 is an overhead style, 46 inch tape travel spring counterbalance available from McMaster-Carr Industrial Supply, model number 1053A38, having a capacity of 27 to 29 pounds. For applications requiring greater tape travel, the preferred model is model number 1053A57, having a 54 inch tape travel and rated at 30 to 32 pounds. The counterbalance 60 provides a force on the main rail 20 that slightly biases the rail 20 towards an extended position. Ideally, the amount of bias force on the main rail 20 is sufficient to maintain the dead weight of the safety cage 10 in its extended position, but not great enough to move the retractable safety cage 10 from its extended position to its retracted position without the application of a minimum force applied by the user. This prevents the safety cage 10 from slamming into its retracted position when the retaining pins 160 are disengaged. In addition, this bias force toward the extended position assists the user in moving, that is lifting, the retractable safety cage 10 from its retracted position to its extended position.

[0059] Referring again to the Figures, the method of using the retractable safety cage 10 will now be described. The guide bracket 30 (FIGS. 6 and 7) is mounted to either the two rails 18 of a manhole ladder 16, or alternatively to the front face 12 of the manhole 11. The length L of the guide bracket extension 32 provides the user with adjustability in the mounting location for the retractable safety cage 10. Specifically, the user may position the guide bracket extension 32 vertically and horizontally within the manhole 11 so that the retractable safety cage 10, when extended, maintains a very close clearance near the front face 12 of the manhole 11. In the preferred removable embodiment of the retractable safety cage 10, each guide bracket 30 further comprises a foot 90 (FIGS. 7 and 9). Each counterbalance 60 is mounted to the mounting bracket 70 on the guide bracket extension 32, and the strap 61 of the counterbalance 60 is connected to the through-hole 103 in the stop 100, preferably with an S hook. Typically, one guide bracket 30 and counterbalance 60 assembly is required for each rail 18 of the manhole ladder 16.

[0060] Now, the guide brackets 30 are ready to receive the remaining structure of the retractable safety cage 10, comprising main rails 20 that are connected to a first periphery rail 40 and a floating periphery rail 50 (FIGS. 1, 11, 13). The user can then simply open the manhole cover 19 and insert the distal end 22 of each main rail 20 into the inner surface 84 within the bushing 39. As the main rails 20 are slid downwardly within the inner surface 84, the retaining pin 160 will engage the opening 24 in the distal end 22 of the main rail 20. This then places the retractable safety cage 10 into its extended position. When the user desires to retract the retractable safety cage 10, he simply depresses the handle portion 151 of the lever 150, thereby moving retaining pin 160 from its engaged position to its disengaged position (FIG. 10). This then allows the retractable safety cage 10 to slide from its extended position to its retracted position. Once the retractable safety cage 10 moves into its retracted position, the retaining pin 160 will, under the spring bias force, move from its disengaged position to its engaged position in the opening 23 that is located near the proximal end 21 of the main rail 20 (FIG. 5). This then releasably locks the retractable safety cage in its retracted position, wherein the entirety of the retractable safety cage 10 resides below the surface of the manhole cover 19 (FIG. 4). When the user desires to again extend the retractable safety cage 10 he simply disengages the retaining pin 160 in a similar fashion, and manually lifts the main rail 20 until the retaining pin 160 engages opening 24 in the distal end 22 of the main rail 20. If the user then desires to completely remove the removable safety cage 10, he simply again disengages the. retaining pin 160 from opening 24, and further raises the main rails 20 until stop 100 engages the distal end of the guide bracket 30 (or, the external lip 81 of the bushing 39). Once this occurs, further lifting of the main rails will separate the distal end 22 from the coupling engagement with the tab 120 of foot 90 (FIGS. 7 and 9). This allows the user to then take the assembly of main rail 20, first periphery rail 40, and floating periphery rail 50 and insert it into any manhole 11 that has been fitted with this type of guide bracket 30.

[0061] In yet another alternative embodiment shown in FIGS. 15 and 16, an optional emergency egress frame 78 may be attached to the retractable safety cage 10 at proximal end 21 of the main rail 20 or to the first periphery rail 40. The emergency egress frame 78 may take many shapes, including an A-frame assembly. The emergency egress frame 78 preferably comprises at least three supporting members 71, 72, 73 that are connected at their distal ends to the retractable safety cage 10, and are connected at their proximal ends to each other via a common joint or plate. Affixed to one of said support members 71, 72, 73 is a winch 74 having an extendable cable 75. The cable 75 preferably is routed across one or more pulleys 76 and terminates in a retrieval mechanism 77. In the preferred embodiment, the retrieval mechanism 77 is a hook. During use, the emergency egress frame 78 may be attached to the retractable safety cage 10 and the winch 74 may be operated so as to lower the retrieval mechanism 77 into the manhole 11. A person situated within the manhole 11 may then attach the retrieval mechanism 77 to either himself or an injured person. An operator on the surface then may operate the winch 74 so as to remove the injured person from the manhole 11. The emergency egress frame 78 is typically comprised of the same materials as the retractable safety cage 10.

[0062] While there has been described and illustrated particular embodiments of a retractable safety cage, it will be apparent to those skilled in the art that variations and modifications are possible without deviating from the broad spirit and principle of the present invention, which shall be limited solely by the scope of the claims appended hereto.