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BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to safety devices for the upper ends of ladders. 
         [0003]    2. Brief Description of the Prior Art 
         [0004]    Accidents involving ladders, such as both portable extension ladders and non-extension ladders, can occur when the ladder shifts either because the climber is off balance to one side of the ladder, or because the climber accidentally moves the ladder when climbing off or onto a roof. The most dangerous time when using a ladder to descend is when stepping off of a roof onto a rung of the ladder. The climber is precariously perched, and must cautiously move himself with one foot on the roof and the other on the ladder before bringing the other foot onto the ladder. Standard portable ladders extend above the roof line and the climber must swing step around the extension to exit the ladder. 
         [0005]    Additionally, a climber may lose a hand grip or his foot may slip off of a rung, or his foot may engage another object while climbing any of which may result in the climber falling, Ladder falls generally result in serious injury, and often result in death or paralysis. 
         [0006]    Various solutions have been proposed to make the ladder more stable and ladder climbing safer. Inman, U.S. Pat. No. 8,439,163, fixes a ladder shoe to extend away from the ladder to engage a gutter. This shoe extends outwardly from the ladder. It limits how far the extension ladder can be collapsed, and also makes stacking the ladder more difficult for storage. Hastreiter, U.S. Pat. No. 6,394,229, proposes curved pole extensions bolted to each side rail of the ladder with a series of clamps. The distal end of each pole has a foot resting on the roof surface. These pole extensions must be carefully mounted on the outside of the ladder side rails each time the ladder is used. Otherwise the ladder is very cumbersome to move about or store. 
         [0007]    The clamping required by Hastreiter is time consuming to install. While the pole extensions permit a walk-through climbing on and off the ladder, they are also intended to keep the ladder rails from contacting a gutter. This creates a space between the side rails of the ladder and the roof or roof gutter. In so doing, the pole extensions must bear the entire weight of the climber at an obtuse angle which requires them to be strong enough to hold against the bending forces thereby increasing their cost. Also, such pole extensions generally reduce the load capacity of the ladder. 
         [0008]    Gabriel, U.S. Pat. No. 8,136,632, creates a step through extension ladder with a collapsible platform at its upper end. The platform collapses into a rung-free area at the upper end of the ladder side rails. When extended, this platform rests on the pitch of a roof with the ladder side rails resting against the roof edge or gutter. This requires a custom ladder re-configuration. 
         [0009]    It is has long been suggested for safety, a ladder when leaning against a building or platform, is to be at an angle of about 75 degrees from horizontal. This means that the ladder side rails of each of the above ladders are pitched at an angle of about 15 degrees from vertical when above the roof or platform. This pitch makes climbing back from the roof onto the ladder safer. A steep pitch may promote fall back. A lesser pitch may produce slide out or “pancaking.” 
         [0010]    Ellis, U.S. Pat. No. 6,095,283, shows a vertically upright ladder, permanently attached to a building, with a walk-through design having a wider ladder profile in the walk-through section at the top of the ladder. Two box-shaped elongate sleeves slide down over the top ends of the ladder side rails which side rails, are flared outward to widen the opening between side rails sufficiently to accommodate a climber and a plurality of inwardly extending horizontal grab rungs. The sleeves are positioned above the side rail flaring and secured to the side rails once in position. The location of the top of the sleeves is proximate to the top of the ladder side rails. The permanently flared outward side rails create an awkward structure for moving about and when storing the ladder. 
         [0011]    Ellis, U.S. Pat. No. 6,347,685, shows a vertically upright ladder for permanent attachment to a structure with a walk-through area having two handhold cages providing recommended horizontal grab bars secured permanently to the top end of a respective ladder side rail. For ladders with flared out side rails, the grab cage is attached to the inside face of each side rail. For straight rails, the grab cage is attached to the outside face of each side rail. 
         [0012]    Walk-through ladders have the advantage of providing a safer transition for the climber from the ladder to a roof and from a roof to the ladder. Permanently attached vertical walk-through ladders as shown by Ellis provide a safer transition region for the climber. The climber can first grasp one of the grab bars within box-like frameworks while safely standing on the roof. He can then turn and additionally grasp the second cage. While safely gripping both cages he can step onto the first ladder rung and then begin to transfer his hands to the grab bars. 
         [0013]    OSHA regulations require that the base of an extension ladder, which OSHA considers as a portable ladder, be positioned away from the structure against which the extension ladder rests at a distance of about one-fourth of the working length of the ladder. That equates to about an angle of 75.5 degrees from the horizontal. OSHA regulations also state that no ladder should be used to gain access to a roof unless the top of the ladder shall extend at least three feet above the point of support. OSHA also wants each climber to face the ladder the entire ladder distance when climbing up or descending down, and to maintain a three-point control (two hands and a foot or two feet and a hand) resulting from holding rungs horizontally is much stronger and safer than holding side rails where a climber&#39;s hand can slide when on a ladder. 
         [0014]    Because of the walk-through configuration at the top of the ladder, walk-through ladders are difficult to store and difficult to stack for travel on a vehicle. It is therefore desirable to provide a walk-through configuration at the top end of an extension ladder which is easily removable when the ladder is to be stored or stacked. 
         [0015]    As safety is the first concern, it is desirable to provide a removable walk-through structure for a ladder which can be securely attached to the ladder upper end when the ladder is in use, and is easily removed when the ladder is to be stored or stacked for travel on a vehicle, or moved about. 
         [0016]    It is also desirable that this structure is embodied in a safety device which can be easily attached to and removed from a standard ladder, such as a standard extension ladder. 
         [0017]    Additionally, it is desirable to provide such a walk-through safety device which does not require any modification of a standard extension ladder, albeit, the walk-through safety device will be sized for the size of the ladder side rails which can vary with the materials from which the ladder is made, e.g., steel, aluminum or fiberglass, and in some cases wood, and for a specific ladder length and capacity ladder. 
         [0018]    It is also desirable to have the walk-through safety device include a grab bar (handhold) cage, which will not interfere with the movement of a climber, and where the orientation of the safety grab (handhold) cage is upright and the handholds are horizontally oriented at the recommended spacing, when the ladder properly rests against a structure. The horizontal rung hand hold is intuitive for most climbers to grip and hold successfully in a dynamic fall. A fall become “dynamic” once a body is in motion. Once a fall has begun, grabbing a portion of a ladder results in forces on the hands which are increased greatly, making arrest difficult. If the handhold (rung) is horizontal, sliding is avoided. 
       SUMMARY OF THE INVENTION 
       [0019]    The objectives of the invention are realized in a removable walk-through safety device for the top of conventional design portable ladders including both extension ladders and straight (non-extension) ladders. The safety device has two complementary shaped members mountable on respective ladder side rails. These paired members provide horizontal grab bars (handholds) in a framework positioned outboard of the ladder side rails and canted upward to the vertical when the ladder rests against a structure or wall at the recommended OSHA angle of the main ladder (75.5 degrees). 
         [0020]    Research has shown that in climbing ladders, it is important to hold horizontal grab surfaces like round rungs and not vertical surfaces. The transfer between a roof and a standard extension ladder is a dangerous task as there is no good way to side step off of a ladder and onto a roof and back which requires walking around the ladder side rails when the OSHA requirement for 30 inch extension is met. The present invention permits a climber to step through the top section of ladder which presents a clear passageway for the climber to move onto a roof and back. It converts a standard extension ladder or other ladder to enable step through instead of step-around movements, which can be destabilizing for the climber. 
         [0021]    The pair of removable walk-through ladder members fit over the top end of the side rails of a commercially available extension ladder. The shapes of these members are mirror images of each other, with the paired members being positioned, one each, juxtaposed at the top end of each respective side rail of the ladder. 
         [0022]    Each member preferably includes a box-shaped sleeve (rectangular tube) with an open lower end and a flat wall closing off the top end. Each sleeve&#39;s cross-section is preferably sized slightly larger than the side rail cross-section of an extension ladder to permit it to slide over the respective side rail while limiting the amount of play there between. In conformance with the shape of the side rail of a conventional ladder, each sleeve preferably has two opposing wider sidewalls and two opposing narrower sidewalls, Each sleeve is preferably sized in length to extend over the top rung and to terminate at the position proximate the second rung. 
         [0023]    Preferably, the distance between the members when mounted on a ladder is from about 23 to 26 inches, permitting a person to easily walk through the safety device while maintain a firm grasp on the safety device. 
         [0024]    A longitudinal slot preferably extends along the inside wider sidewall of each sleeve from its open bottom. The slot preferably has a top which rests against the top rung of the ladder when the safety device is installed, and preferably conforms to the shape of the rung. The outside wider sidewall of each sleeve preferably has a cutout opening which provides a clearance for the outward projection of the second rung beyond the outside face of the rail. The cutout preferably conforms to the shape of the second rung, such as a semi-circular cut out for a rung having a circular cross-section. 
         [0025]    A tubular support post is preferably welded to the outside face of each sleeve to flair outwardly and then upwardly from the longitudinal axis of a sleeve at an angle of about 15 degrees, preferably, 14.5 degrees. Preferably, attached to this tubular post is a series of tubular handles, such as a series of three handles, which are used as climber grab bars (handholds) by a climber, and which extend outwardly perpendicularly to the plane of the outside face of the sleeve. Attached to the outside end of each tubular handle (handhold) is a support bar which with the grab bars and the tubular post form a handhold framework. When the ladder rests against a structure at the recommended OSHA safety angle, each handhold framework extends vertically, is outboard of, and is perpendicular to, each rail. 
         [0026]    The three grab bars (handholds) are preferably spaced on 12 inch centers and preferably no more apart than 14 inches. The tubular sleeve, support post and handhold frameworks are sized so that the top grab bar (handhold) is about three-feet above the rest point of the ladder against the structure or wall and the handhold framework extends vertically when the ladder is properly rested against a structure, It is noteworthy that about one-half of OSHA&#39;s ladder citations are based on a failure to extend three feet over a dismount level or platform. 
         [0027]    Each of the two sleeves is preferably securely mounted on a side rail with the sleeve sidewall elongate slot resting on the top rung of the ladder. A clamping pressure is preferably exerted between the sleeve and the adjacent face of the side rail. This clamping pressure is preferably obtained with a securing tab plate being forced against the side rail by a knob operated screw, whereby the securing tab plate is preferably moved with a clamping force against the side rail. This securing tab plate is preferably implemented as an elongate rectangular flat bar with an end box-shaped rectangular shoe. The shoe is preferably forced into a mating opening in the smaller sidewall of the sleeve where it is securely held in a friction fit. 
         [0028]    A triangularly shaped plate preferably acts as a rung engaging pivot lock. This pivot lock is preferably attached to the inside wider face of the sleeve to pivot out of the way when the sleeve slides past the top rung, and to return to its original position when it has passed the top rung. In its original position the lock plate preferably extends to an orientation in which it would engage the bottom surface of the top rung if the sleeve moved upwardly. In this original interference position, the pivot lock preferably prohibits the removal of the sleeve from the ladder as it engages the top rung to prohibit further upward movement of the sleeve off of the side rail. 
         [0029]    The pivot lock plate preferably has two tabs. The first tab (the locking tab) preferably extends perpendicular to the plane of the plate across the smaller face of the sleeve. A tempered spring plate is preferably attached to the inside face of the sleeve to engage the lock plate perpendicular tab to spring bias the lock plate into the original position. The second tab preferably extends upwardly in the plane of the plate. This second tab is preferably used to manually pivot the lock plate from an interference engagement with the ladder top rung when the sleeve is to be removed from the side rail. A triangular side-profiled locking tab cover plate preferably covers the locking tab and spring plate movement and to protect these structures from damage by repeated climbers. 
         [0030]    The labeled safety device left-hand and right-hand members are preferably easily assembled on the side rail ends of a conventional straight or extension ladder and easily removed. The knob operated screw is preferably tightened to remove the slackness when the ladder is in use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is perspective view of a conventional extension ladder, with the safety device of the present invention having two members installed, the ladder resting against a structure with a climber about to step upon a roof. 
           [0032]      FIG. 2  is a partial perspective view of the extension ladder of  FIG. 1  showing the left hand and right hand members of the safety device. 
           [0033]      FIG. 2 a    is a partial perspective view with each member support pole having a releasable hinge. 
           [0034]      FIG. 2 b    is a partial rear perspective view showing the extension ladder and safety device of  FIG. 1 . 
           [0035]      FIG. 2 c    is a climber&#39;s face view of a foldable safety device in the upright position and folded position. 
           [0036]      FIG. 3  is a partial side view of the ladder of  FIG. 2 . 
           [0037]      FIG. 4  is a partial side view of the right-hand member of the safety device of the present invention about to be installed on the upper end of an extension ladder. 
           [0038]      FIG. 5  is a view of the member of  FIG. 4  with the right-hand member moved downwardly on the ladder side rail, wherein the rung pivot lock is being rotated by the top rung to remove the interference function of the pivot lock. 
           [0039]      FIG. 6  is a view of the right-hand member of  FIGS. 4 and 5  with the member being fully down so that the top rung abuts the top of the slot and the pivot lock has returned to is original position in an interference orientation with the top rung. 
           [0040]      FIG. 7  is a left side view of the sleeve and handhold framework of the right-hand member of the present invention. 
           [0041]      FIG. 8  is a front view of the sleeve and handhold framework of  FIG. 7 . 
           [0042]      FIG. 9  is a perspective view of the right-hand member sleeve. 
           [0043]      FIG. 10  is a perspective view of the securing tab plate. 
           [0044]      FIG. 11  is a perspective view of a rung pivot lock for the right-hand member of  FIG. 5 . 
           [0045]      FIG. 12  is a perspective view of the locking tab cover plate. 
           [0046]      FIG. 13  is a side view of the locking tab cover plate of  FIG. 12 . 
           [0047]      FIG. 14  is a perspective view of a gutter shoe ladder support. 
           [0048]      FIG. 15  is a perspective view of the safety device and ladder of  FIG. 2  at rest against the gutter shoe of  FIG. 14 . 
           [0049]      FIG. 16  is a climbers face view of a ladder with an alternate embodiment being a “zigzag” shaped grab bar safety device. 
           [0050]      FIG. 17  is a side view of the ladder and safety device of  FIG. 16 , 
           [0051]      FIG. 18  is a side view of the ladder of  FIG. 16  with an alternate embodiment being a releasable hinge which permits the grab bar safety device to fold forward. 
           [0052]      FIG. 19  is a perspective view of the ladder and safety device of  FIG. 16  showing the ladder and safety device positioned on the side of a truck trailer. 
           [0053]      FIG. 20  is a perspective view of the ladder and safety device of  FIG. 1  showing the ladder and safety device positioned against a building wall to permit access to a window in the wall for window maintenance or repair. 
           [0054]      FIG. 21  is a perspective view of the safety device and truck trailer of  FIG. 19 , showing the trailer with a load being secured by an operator using the safety device to access straps to secure the load to the trailer. 
       
    
    
     DETAILED DESCRIPTION 
       [0055]    The features, advantages and operation of the present invention will become readily apparent and further understood from a reading of this detailed description with the accompanying drawings, in which like numerals refer to like elements, and in which: 
         [0056]    In one presently preferred embodiment the present invention provides a safety device preferably to be mounted onto the top or distal end of an extension ladder, such as a conventional extension ladder, to add a walk-through configuration having handhold grab framework to the ladder extending vertically above the extension ladder, preferably at the OSHA-recommended distance. The safety device  23  of the present invention can be used with conventional fixed (non-extendable) ladders, conventional extension ladders, articulated (collapsible) ladders, fire rescue ladders, etc. 
         [0057]    The safety device  23  is preferably formed from a high strength material, such as steel or aluminum, and more preferably, a high strength light weight material such as aluminum. 
         [0058]    As can be seen in the perspective view of  FIG. 1 , an extension ladder  21  rests against a building  20  at the OSHA-recommended angle of 75.5 degrees and is being climbed by a user about to climb upon the roof of the building  20 . A safety device  23  is fitted to the top end of the extension ladder  21 . 
         [0059]    Advantageously, it is the top end of the extension ladder  21  that contacts the surface of the surface of the wall or building  20  against which the ladder  21  bears (although the top ends of the sides of the ladder may be covered by a portion of the safety device as shown below). Thus, no force is being transmitted through the upwardly extending portions of the safety device when a ladder  21  fitted with the safety adapter  23  is positioned against the building  20 . 
         [0060]    The safety device  23  preferably includes both a left-hand member  25  and a right-hand member  27 . The left-hand member  25  and the right-hand member  27  are mirror images of each other. Each of the members  25 ,  27  includes a respective handhold framework  29   a,    29   b.  In this embodiment, each handhold framework  29   a,    29   b  has three successive horizontally extending handhold bars  31 , preferably spaced by about 12 inches from each adjacent bar  31 . Preferably, the diameter of each bar  31  is about one inch to one and one-half inches (runglets) such that the bars can be easily grasped by a person climbing the ladder, and which helps avoid falling. Each of the handhold bars  31  extend from an inward support pole  45  to a corresponding outward support bar  47 . The inward support pole  45  and the outward support bar  47  are preferably parallel to one another, and the inward support pole  45 , handhold bars  31 , and outward support bar  47  of each of the handhold frameworks  29   a,    29   b  preferably all lie in the same plane, which extends vertically above the extension ladder  21 . 
         [0061]    Each of the support poles  45  has an inward facing surface and an outward facing surface. A pad  43  ( FIG. 2 b   ,  FIG. 7 ) formed from a slip-resistant material is secured, such as by an adhesive material, to the inward facing surface of each of the support poles  45 , such that when the safety device  23  is mounted on a ladder  21  and the ladder  21  is positioned against a building or wall the slip-resistant pad  43  contacts the surface of the building or wall to help prevent slippage of the ladder  21  in a direction perpendicular to the ladder  21 . Examples of suitable slip-resistant materials include natural rubber and synthetic elastomers. 
         [0062]    As best seen in the perspective view of  FIG. 2 , the left-hand member  25  and the right-hand member  27  are each mounted to a respective left side rail  33  and right side rail  35  of the upper section  37  of the extension ladder  21 . When the extension ladder  21  is positioned at a predetermined leaning angle, such as the OSHA-recommended leaning angle, where the distance from the wall to the base of the ladder is a distance which is  25  percent of the working length of the ladder, the frameworks  29   a,    29   b  extend approximately vertically, preferably for a predetermined distance, such as the recommended distance of about three feet, above the resting point of the ladder, In the present specification and claims, “vertical” means extending upward approximately 90 degrees from horizontal, but can vary plus or minus 10 degrees therefrom depending on conditions. The two support poles  45  and the uppermost rung of the ladder collectively form an opening or window  46  though which the climber can pass though onto a roof or other surface when the ladder  21  and safety device  23  are positioned such that the safety device  23  extends above the roof or other surface. Further, when ladder  21  with the safety device  23  mounted thereon are positioned against a wall or other vertical surface, the two support poles  45  and the uppermost rung of the ladder  21  frame a window  46  on the surface in which a climber can safely perform work, such as maintenance tasks including painting the surface of a window or other architectural feature provided on the surface, such as depicted in  FIG. 20 . The ladder  21  with the safety device  23  can be centrally positioned on the window permitting a climber to work without the destabilizing leaning that can occur when using most other ladders and ladder extensions. Preferably, the safety device  23  and ladder  21  are positioned such that there is a least about an inch of clearance between the safety device  23  and the wall or window frame for gripping the safety device. 
         [0063]    Depending on the configuration of the ladder sides, the support poles  45  may be canted in the plane of the ladder to provide the frameworks with the desired vertical extension. For example, when the upper ends of the ladder sides are flared outwardly, the support poles may be canted or bent inwardly such that the outward support bars extend vertically and the grab bars extend horizontally (not shown). Similarly, when the upper ends of the ladder sides are flared inwardly, the support poles may be canted or bent outwardly such that the outward support bars extend vertically and the grab bars extend horizontally (not shown). 
         [0064]    In another embodiment of the present invention, the safety device is formed integrally with the ladder, such that the support poles are mounted permanently on the upper ends of the ladder, or are formed integrally therewith (not shown). The support poles  45  can be fitted with a releasable hinge  99 , such as depicted in 
         [0065]      FIG. 2 a   , which permits the upper end of each safety device member  25 ,  27  to fold down on itself and onto the ladder  21 . Examples of releasable ladder hinges which can be employed are disclosed for example in U.S. Pat. Nos. 4,407,045, 4,666,150, 7,093,311, and 7,306,075, each incorporated herein by reference. Depending upon where the hinge  99  is positioned, the length of the safety device members  25 ,  27  to folded back can be about 28 to 34 inches. The safety device members  25 ,  27  can be folded back when the ladder  21  is laid on the ground. The folded members permit the ladder  21  to be moved about more easily and stored in a workshop, or loaded on a rack mounted on a work truck more easily. The hinges  99  can be positioned so that the member handhold frameworks  29   a,    29   b  also swing onto the ladder  21 , such as depicted in  FIG. 2 b   .  FIG. 2 b    shows the frameworks  29   a,    29   b  in the extended position  101  (shown in phantom) and swung into the folded position  103 . 
         [0066]    It is suggested for safe operation to set an extension ladder  21  at the OSHA recommended parameters. The extension ladder  21  with the safety device  23  mounted thereupon is preferably set to lean against a building or wall at an angle from horizontal of 75.5 degrees, as shown in the partial side view of  FIG. 3 . To have the handhold frameworks  29   a,    29   b  extend completely vertically upright when the ladder is at 75.5 degrees, the frameworks  29   a,    29   b  are canted (angled) upward at an angle of about 15 degrees  41  (preferably 14.5 degrees) from the longitudinal axis  43  of the ladder  21 . Each framework  29   a,    29   b  is held outboard of the ladder side rails  33 ,  35  and beyond the top end of the ladder extension section  37  by a support tube or pole  45  (best seen in  FIG. 2 ). This support pole  45  forms the inside member of each framework  29   a,    29   b  from which each of the handhold bars  31  extend. The outboard ends of each handhold bar  31  are attached to a flat outside support bar  47 . When the ladder  21  is properly positioned, each of the handhold grab bars  31  extends horizontally providing an optimal horizontal handhold. 
         [0067]    Each member  25 ,  27  preferably includes a respective tubular, generally rectangular, sleeve  49 , as shown for the right-hand member  29   b  in  FIGS. 4-6 . This sleeve  49  has a closed outer top end  51  and an open bottom end  53  to slide over the respective side rail  35  of the extension ladder  21 . A slot  55  is formed on the inside face of the sleeve  49  (best seen in  FIGS. 4 and 5 ) to extend from the open bottom  53  and to terminate in the upper half of the sleeve  49  in a curved surface  57 . The curved surface  57  is adapted to rest upon ladder rungs having a generally circular cross-section. However, the shape of the surface  57  may be, for example, rectangular, to rest upon extension ladders having rungs with rectangular cross-sections (not shown). Preferably, positioned inside the sleeve  49  is an elongate securing tab plate  61  (best seen in  FIGS. 4 and 10 ) held to a generally rectangular slot  60  in the adjacent wall  59  by a shoe  63  formed at one end of the securing tab plate  61 . A rung pivot lock  65  is preferably pivotally connected to the slotted side of the sleeve  49 .  FIG. 4  is a partial perspective view showing the right-hand member  27  positioned just above and coaxial with the right side rail  35  of the ladder extension end  37  in preparation for slipping the right-hand member  27  over the right side rail  35  of the ladder extension end  37 . 
         [0068]      FIG. 5  is a side view showing the sleeve  49  partially mounted over the ladder extension end  37  of the side rail  35  of the extension ladder  21 , the top rung  67  of the ladder extension  37  has passed almost to the top of the slot  55  and the side rail  35  almost abuts the closed top  51 . In this position, the side rail  35  has pushed the securing tab plate  61  back against the inside of the sleeve  49 . Preferably, a knob-operated manual turn screw  69  extends through the wall of the sleeve  49  to bear against the securing tab plate  61  which in turn clamps against the side rail  35  when secured by an operator, the screw  69  preferably being peened to prevent inadvertent removal from the safety device  23   
         [0069]    The second rung  71  is preferably positioned below the open bottom end  53  of the sleeve  49 . In moving the sleeve  49  onto the side rail  35  the top rung  67  engages the rung pivot lock  65  (best seen in the perspective view of  FIG. 11 ) which is preferably triangularly shaped to provide a tapered camming surface  73  which operates against the top rung  67  to pivot the lock  65  out of the way of the top rung  67 . The lock  65  is biased to an interference position by a spring plate  75  which is covered by a ramp-shaped locking tab cover plate  77 , best seen in  FIGS. 5, 12 and 13 . 
         [0070]    When the sleeve  49  is fully inserted over the side rail  35 , as can be seen in  FIG. 6 , the top rung  67  is seated against the curved surface  57  at the top of the slot  55  and the second rung  71  is adjacent the open bottom  53  of the sleeve. The rung pivot lock  65  has rotated to its original rung interference position where, if the sleeve  49  is attempted to be moved outward off of the side rail  35 , the abutment surface  79  of the rung pivot lock  65  engages the top rung  67  and stops the movement. 
         [0071]    Preferably, as best seen in the front elevation view of  FIG. 8  showing the right-hand member  27  the handhold bar frameworks  29   a,    29   b,  preferably have handhold bars  31  spaced on 12 inch centers, as are the rungs of the ladder  21 . The side elevation view of the right-hand member of  FIG. 7  and the perspective view of the right-hand sleeve of  FIG. 9  show that the opposite side of the sleeve  49  from the slotted side can have a half-circle cutout at the open bottom  53 . This cutout accommodates the second rung  71  where the spacing between rungs may vary. In so accommodating the second rung  71  the abutment of the top rung  67  against the top of the slot  55  is assured, 
         [0072]      FIG. 9  also shows a rectangular cutout opening  83  in the slot adjacent sidewall  59 . This opening  83  accommodates the shoe  63  at the one end of the securing tab plate  61 ,  FIG. 10 , in a friction fit. 
         [0073]    The rung pivot lock  65 ,  FIG. 11 , has two outwardly extending tabs, a first tab  85  extending perpendicular to the plane of the lock to extend under the lock tab cover plate  77  to engage the spring plate  75 . This spring plate  75  biases the lock  65  to the original interference position. The second tab  87  assures that the lock does not bind and is useful for when manually moving the lock to a non-interference position. 
         [0074]    The lock tab cover plate  77 ,  FIGS. 12, 13  has an upright wall  89  and a sloped top wall  91  supported on one end by the upright wall  89 . The other end of the sloped wall  91  terminates in a pair of rectangular tabs  93 . These tabs  93  engage a smaller rectangular slot  95  adjacent the opening  83  in the sleeve wall,  FIG. 9 . A bolt  97 ,  FIG. 5 , can secure the tabbed end of the cover  77  to the sleeve  49 . 
         [0075]    A gutter docking station  105 ,  FIG. 14 , (Roofer&#39;s World, Ottawa, Ont.), has a box-shaped structure  107  which fits inside of a building&#39;s gutter, and has a pair of channels  109  which extend over and downward on the outside face of the gutter. These two channels  109  receive the respective side rails  33 ,  35  of a ladder  21 , or when the safety device is installed on the ladder  21 , the channels receive the safety device members  25 ,  27 ,  FIG. 15 , and resist the ladder sideways movements. 
         [0076]    In another embodiment of the present invention, the safety device is integrally formed with, or permanently attached to, a ladder, rather than being detachable (not shown). 
         [0077]    In a further embodiment,  FIGS. 16 and 17 , a ladder  110  has the rectangular shaped grab bar frameworks  29   a,    29   b,  replaced with “zigzag” shaped grab bar sections  111   a  and  111   b.  Each grab bar section  111   a  and  111   b  has three horizontal handholds  113  supported by a support pole  115 . The support pole or tube  115  is mounted outside of the ladder  110  side rails so that the handholds  113  are outside of the line of ladder permitting a walk-through passage. This support pole  115  need bend only one direction so that the grab bar sections  111   a,    111   b  are upright (vertical) when the ladder is at the proper angle when resting against a truck,  FIG. 17 . Advantageously, the ladder  110  can be positioned to rest against the truck trailer, such as shown in  FIG. 19 . When a truck trailer is being loaded, tie-down straps must typically be thrown over the load from the first side upon which they are fastened to the truck body to the opposite side, and the ends must be grasped at elevation typically about eight feet above the ground. Similarly, when tarps are used to cover a load, “bungee” cords are often employed to fasten to eyelets provided in the tarp to secure the tarp to the truck body, and the tarp edges often cannot be grasped without standing on a ladder. 
         [0078]      FIG. 21  provides a perspective view of the safety device and truck trailer of  FIG. 19 , showing the trailer with a load being secured by an operator using the safety device to access straps to secure the load to the trailer. Conventional straight ladders employed to reach and grasp the tie-down straps may have to be placed against the load rather than the truck body, a less secure practice than employing a ladder according to the present invention. 
         [0079]    If the hinge  99  is further adjusted, the grab bar sections  29   a,    29   b  or  111   a,  and  111   b,  can be folded approximately in alignment with the ladder  21  (or ladder  110 ), as shown in  FIG. 18 . The folding scheme works better with shorter ladders and it extends the length needed to carry or store the ladder. 
         [0080]    Many changes can be made in the above-described invention without departing from the intent and scope thereof. it is therefore intended that the above description be read in the illustrative sense and not in the limiting sense. Substitutions and changes can be made while still being within the scope and intent of the invention and of the appended claims.

Summary:
Walk-through safety devices for ladders meeting ANSI and OSHA standards are positioned at the top end of the ladder and are comprised of two, juxtapose-position, mirror image members. One each is mounted on a respective ladder side rail, Each member includes a sleeve (or rectangular tube) which slides down over a respective ladder side rail, a pressure bar which is tightened against the side rail with a knob operated screw, a pivoting engaging lock plate, and a lock plate tab cover plate. A horizontal hand grip framework is held outboard of the ladder side rails vertically upward, being at an angle of about 14.5 degrees upward from the longitudinal axis of the sleeve and side rail when resting against a structure. The framework is held in that position by a flared tube which is bent in two directions.