Abstract:
A manually-releasable apparatus for arresting a hunter&#39;s fall from a tree stand is described herein. The apparatus comprises a satchel with two compartments, one compartment containing a controlled descent device and the other compartment containing a reel upon which a safety strap is wound. The safety strap is attached to the tree and passes through the controlled descent device and then is wound onto the reel. The hunter&#39;s safety harness is attached by means of a tether to an eye in the controlled descent device, which is attached to a safety belt secured to a tree. The apparatus quickly arrests a hunter&#39;s fall and then allows the hunter to manually release the braking mechanism within the controlled descent device once the hunter has freed himself from obstructions and is in a position to descend to the ground.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    It is often advantageous while hunting with a bow or rifle in wooded areas to sit in an elevated position. Tree stands in a variety of designs are used for this purpose. The devices are lightweight and compact and consist of a support structure affixed to the trunk of a tree and a seat for the hunter. They allow a hunter to sit high in a tree for long periods of time while hunting. Because many hunters spend long periods of time in the tree stand, it is not uncommon for them to doze off while they are suspended high above the ground. Also, a hunter&#39;s attention may be so focused when aiming for a shot that he falls from the relatively small seat. The dangers of falling while perched in a tree stand are manifest. 
         [0004]    To address this safety issue, hunters typically wear a safety harness that is attached to some form of fall arresting device. Many of these fall arresting devices use some form of inertia reel assembly, which lock the safety line or belt when a fall occurs. Although these devices save the hunter from a fall, they create their own problems, chief among which is suspension trauma. 
         [0005]    Suspension trauma, also known as orthostatic intolerance, occurs when blood pools in the legs and lower extremities. It results from being suspended or confined in an upright position without the ability to move. Such conditions occur when standing at attention for long periods of time without being able to lie down, or being suspended in a harness. Under normal conditions, the leg muscles when walking or moving assist the heart muscle in pumping blood from the lower extremities. However, when the body is upright while suspended in other situations where the legs are unable to provide this assistance, the heart is unable to pump blood from the lower extremities. 
         [0006]    Suspension trauma deprives the brain of blood and therefore can, in extreme cases, be fatal. Typically, a person experiencing suspension trauma will go into shock initially, then faint. Under normal circumstances, when a person faints, they fall in a horizontal position, which allows blood to flow back into the brain. However, if a person is suspended upright or confined in an upright position without the ability to move, blood flow to the brain does not occur. As a result, if the situation is not corrected, an upright suspension condition can be fatal. 
         [0007]    Suspension trauma typically occurs when a fall arresting device saves a hunter from a fall, but leaves a hunter, literally, dangling. The problem with prior art fall arresting devices is that the inertia reel can only be unlocked when the tension on the belt or cable is released. For a hunter dangling from a safety line, this tension is usually difficult, if not impossible, to release because the fall arrest system is located out of reach of the fallen person. In many cases, a hunter will have fallen in an awkward position that is difficult to get out of. Moreover, the hunter may be hung up or even impaled in some fashion on a tree branch or other protrusion. If a hunter is alone in the wilderness without a means of releasing the suspension and controllably lowering himself to the ground, he faces death or serious injury from suspension trauma, exposure, or from injuries suffered during the fall. 
         [0008]    What is therefore needed is a fall arresting device with a locking mechanism that allows a hunter to controllably lower themselves to the ground. 
         [0009]    There are a number of fall arresting devices on the market and in use today. For example, the Escape-Rite® is a fall arresting device for use by firemen, linemen, and other workers who work at heights. Petzl® makes a number of rope grab devices for climbers that will arrest vertical falls. 
         [0010]    However, these devices do not take account of the conditions faced by hunters who have fallen from a treestand, namely, the presence of obstructions upon which a hunter may become entangled or even impaled. What is needed is a device that will quickly arrest the fall of a person that can be also manually-released to allow a hunter who has fallen out of a tree stand to lower himself to the ground. U.S. Patent Application Publication US20060113147A1 to Harris describes a fall protection system that allows a controlled descent; however, the mechanism used to accomplish the descent is more complex than the apparatus described herein. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The apparatus described herein allows a hunter who has fallen from a tree stand to lower himself to the ground in a completely controlled fashion. A controlled descent device and a reel for a safety strap are contained in a satchel. One free end of the safety strap is anchored to a tree, the safety strap then passes through the controlled descent device and the excess length of the safety strap is wound onto the reel. The hunter connects his safety harness to an eye in the baseplate of the controlled descent device that protrudes from the bottom of the satchel. The satchel itself is usually suspended 2-3 feet above the hunter&#39;s head, so a suspension release strap attached to the hunter&#39;s harness is used to release the braking mechanism of the controlled descent device after a fall. 
         [0012]    The controlled descent device allows a hunter to controllably lower himself to the ground. The controlled descent device contains a spring-tensioned cam brake. Spring tension keeps the cam brake&#39;s braking surface engaged with the safety strap, preventing free travel of the safety strap through the device, thereby arresting a hunter&#39;s fall. Prior art cam buckles operate on a similar principle; however, these buckles require a user to release the cam by pressing directly on the lever of the cam. However, because the apparatus described herein is usually attached to a tree at least 2 feet above the hunter&#39;s head, directly releasing the cam buckle when a hunter has fallen is nearly impossible. The addition of two rollers within the controlled descent device permits the safety strap to double back over the cam brake lever and apply pressure to the cam brake lever when the hunter pulls on the non-tensioned portion of the safety strap. Thus, a hunter who has fallen and is suspended by the safety strap releases the cam brake by simply pulling on the non-tensioned portion of the safety strap, without actually having to touch the cam brake itself. Releasing the cam brake allows the safety strap to travel freely through the controlled descent device. Because one end of the safety strap is attached to the tree, releasing the cam buckle causes the controlled descent device to trolley along the safety strap, thereby allowing the apparatus and hunter to descend in a controlled fashion to the ground. 
         [0013]    The relatively simple structure of the apparatus allows it to be lightweight, easy to replace, and inexpensive, unlike prior art fall arresting devices. 
         [0014]    Although hunters are the preferred embodiment&#39;s primary user, it will be obvious that the apparatus described herein is suited for use by any person working at heights where falling is a risk. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will be more fully understood from the detailed description given below and from the accompanying drawing of the invention, which however, should not be taken to limit the invention to the specific embodiments enumerated, but are for explanation and for better understanding only. Furthermore, the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Finally, like reference numerals in the figures designate corresponding parts throughout the several drawings. 
           [0016]      FIG. 1  shows side ( FIG. 1-1 ), front ( FIG. 1-2 ), and top ( FIG. 1-3 ) cutaway views of the satchel, showing the reel and the controlled descent device. 
           [0017]      FIG. 2  shows bottom ( FIG. 2-1 ) and top ( FIG. 2-2 ) exterior views of the satchel. 
           [0018]      FIG. 3  shows side and front views of the reel. 
           [0019]      FIG. 4  is a perspective view of the controlled descent device with the cover installed, showing the baseplate and safety strap. 
           [0020]      FIG. 5  is a side view of the controlled descent device with the cover, baseplate, and other components removed for clarity, showing the key internal components of the controlled descent device. 
           [0021]      FIG. 6  shows the internal components of the controlled descent device from the opposite side of  FIG. 5 . 
           [0022]      FIG. 7  shows the entire apparatus in use, including satchel, controlled descent device, reel, and safety belt. 
           [0023]      FIG. 8  shows a detailed view of a typical satchel and safety strap configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The apparatus claimed herein is comprised of a round satchel  1  partitioned into two compartments  2 ,  3  separated by a fabric partition  4  as shown in  FIG. 1 . One compartment  2  contains controlled descent device  5 , and a second compartment  3  contains reel  6  upon which safety strap  15  is spooled. Satchel  1  is canvas or nylon in the preferred embodiment, but can be any appropriate material. In the preferred embodiment, the diameter of reel  6  is such that 40 feet of safety strap can be wound on the reel, although a greater length can be accommodated if the size of the reel is increased commensurately. However, 40 feet was chosen for the preferred embodiment because the majority of tree stands are used no higher than 40 feet. It is important that the reel be sized exactly, as friction between the reel&#39;s screw channels  7  and safety strap  15  holds the safety strap on the reel snugly, yet allows the hunter to release and unwind the safety strap from the reel after a fall, as will be explained below. 
         [0025]    Referring now to  FIG. 2-2 , the top of satchel  1  has a single hole  8  allowing the portion of the safety strap that will be attached to the tree to exit the satchel. Holes  9 ,  10 , and  11  are in the bottom side of satchel  1 , as shown in  FIG. 2-1 . Holes  9  and  10  allow eye  17  of controlled descent device  5  and safety strap  15   b  to pass out of compartment  2 , respectively. Hole  11  in the bottom of satchel  1  permits the second end of safety strap  15   b  to pass into compartment  3 , where it is wound around reel  6 . In this paragraph, “top” and “bottom” refers to the satchel&#39;s orientation when the apparatus is in use, as shown in  FIG. 8 . 
         [0026]    Reel  6  is made of 2 circular aluminum plates  12  with a freely rotating core  13  with a slot  14  into which the end of the second end of safety strap  15   b  is inserted, as shown in  FIG. 3 . As described above, the diameter of the plates  12  is dependent on the length of the safety strap to be wound around the reel. Safety strap  15   b  is then wound onto the core until it is held snugly by the three screw channels  7  spaced  120  approximately degrees apart around the perimeter of the reel. The safety strap is wound onto the reel so that the friction between screw channels  7  and the safety strap prevents the safety strap from unwinding from the reel. However, when the safety strap is pulled firmly the safety strap will come loose and begin to unwind from the reel freely. That is, the core of the reel is designed so that continuing to pull on the safety strap once it has broken loose will cause the safety strap to unwind rapidly from the reel under its own weight. 
         [0027]    The weight-bearing end of safety strap  15   a  is attached securely to the tree. This tensioned end passes through hole  8  in the top of the satchel and into controlled descent device  5 . 
         [0028]    Safety strap  15  in the preferred embodiment is made of nylon fiber and is 1″ wide. Although seatbelt-type webbing was originally considered, webbing containing ridges oriented perpendicular to the direction of strap travel was found to be most effective in allowing the cam grip to engage. Although the safety strap can be wider than 1″, it was found that 1″ wide nylon weave was sufficient to support loads of up to 400 lbs. 
         [0029]    A first portion of safety strap  15   a  is the weight-bearing portion of the safety strap. It is attached to the tree (or onto another strap fastened to the tree) and passes into controlled descent device  5  through hole  8  in the top of satchel  1 . It then passes into the controlled descent device through hole  18  in cover  20  as shown in  FIG. 4 . It is engaged by braking surface  21   a  of cam brake  21 , as shown in  FIGS. 5 and 6 . 
         [0030]    Referring again to  FIGS. 5 and 6 , a second portion of the safety strap  15   b , will be referred to as the releasing end or non-tensioned end. It begins at cam brake  21  and passes around roller  22 , over cam lever  21   b , around roller  23  and over guide  24  before passing out of the controlled descent device  5  through hole  19  in cover  20  as shown in  FIGS. 4 and 6 . The releasing end  15   b  then passes out of compartment  2  through hole  10  and into compartment  3  through hole  8 , where its excess length is wound around reel  6 . 
         [0031]    Controlled descent device  5  is comprised of several components. Base plate  16  shown in  FIG. 4  is made of mild steel approximately 0.120″ in thickness in the preferred embodiment. Baseplate  16  features an eye  17 , which serves as the attachment point for tether  28  that is attached to the hunter&#39;s safety harness. In the preferred embodiment, eye  17  is coated with Line-X® or other comparable protective coating to prevent metal-on-metal contact. Nested within the baseplate are rollers  22  and  23 , cam brake  21 , guide  24 , and torsion spring  25 . The rollers  22  and  23 , cam brake  21 , and torsion spring  25  are held in position using pins and rivets to baseplate  16 . In the preferred embodiment, these pins and rivets are zinc, although other suitable materials known to the art may be used. 
         [0032]      FIGS. 5 and 6  show the internal components of controlled descent device  5  with base plate  16 , cover  20 , pins, and rivets removed for clarity. Spring-tensioned cam brake  21  is positioned between rollers  22  and  23 . Cam brake  21  has a braking surface  21   a  and a lever  21   b . Braking surface  21   a  engages the first portion of safety strap  15   a  so that when the safety strap is travelling freely—as during a fall—braking surface  21   a  will engage the safety strap by pinching the safety strap between it and the baseplate. Braking surface  21   a  may be textured in any manner known to the art to maximize gripping and braking efficiency while minimizing damage to the nylon strap; in the preferred embodiment, a “waffle iron” type pattern is used for braking surface  21   a.    
         [0033]    Referring now to  FIG. 6 , torsional spring  25  tensions cam brake  21  so that the braking surface  21   a  rests lightly against the safety strap  15   a  and engages when there is any sudden travel in the safety strap (as during a fall). In the preferred embodiment, cam  21  is made of zinc alloy, although any suitable material known to the art may be used. 
         [0034]    Continuing to refer to  FIGS. 5 and 6 , rollers  22  and  23  are cylindrical and made of Delrin® plastic with a zinc alloy pin holding the rollers in position on the baseplate. In the preferred embodiment, the Delrin® rollers have a ¼″ inside diameter and a ½″ outside diameter and extend across the entire width of the baseplate. 
         [0035]    This arrangement of the components within controlled descent device shown in  FIGS. 4 and 5  allows a fallen hunter to controllably lower himself to the ground. Tensioned end of safety strap  15   a  passes into the controlled descent device through hole  18  in cover  20  and is engaged by cam braking surface  21 , which grips the textured surface of safety strap  15   a  and prevents its travel through the controlled descent device. Cam brake  21  is spring-loaded and designed so that the more force is applied to the tensioned end of safety strap  15   a , the tighter braking surface  21   a  will grip. However, when the user desires to release the brake, the configuration of rollers  22  and  23  allows the user to release the brake without applying pressure directly to the cam lever  21   b . This is accomplished when the user pulls on the releasing end of safety strap  15   b . Roller  23  redirects the tension force applied by the user so that the strap causes cam lever  21   b  to move downward, thereby causing braking surface  21   a  to disengage and allow safety strap  15  to travel freely through the controlled descent device. If the user subsequently releases the tension on non-weight-bearing portion of safety strap  15   b , torsional spring  25  causes the braking surface  21   a  to reengage, stopping travel of the safety strap through the controlled descent device. 
         [0036]    Having described the configuration of its components, use of the apparatus will now be described. Referring to  FIGS. 7 and 8 , weight bearing end of safety strap  15   a  is attached to the tree. In the preferred embodiment, the free end of safety strap  15   a  is attached to a carabiner, which is then attached to a line or strap that is fastened or anchored securely to the trunk of tree  29 . Tether  28  is typically 24″-36″ long. One end of tether  28  is attached to eye  17  and the other end is attached to the hunter&#39;s safety harness. The tether should be adjusted so that its length is minimized. With the hunter  26  in the normal sitting position shown in  FIG. 7 , the apparatus should be above the hunter&#39;s head, with little or no slack in the tether. 
         [0037]    A first end of release strap  27  is attached to the loop of safety strap  15   b  that is outside the satchel, while the second end is attached to tether  28  where the hunter can easily reach it. The release strap is used in the event of a fall and is required because once a hunter has fallen, the apparatus will typically be out of reach of the hunter. When the hunter has freed himself from any entanglements and is ready to begin a controlled descent, the first step is to pull release strap  27 , which frees releasing end of safety strap  15   b  and cause it to unspool from reel  6 . As mentioned above, a firm pull of several pounds force should be sufficient to break safety strap  15   b  free from the reel. After only a small amount of safety strap  15   b  is pulled free using release strap  27 , the safety strap&#39;s own weight will cause the entire length of the safety strap  15   b  on the reel to quickly unwind. The releasing end of safety strap  15   b  that is inserted into slot  14  should come free once the safety strap has unwound from the reel, allowing the length that was wound around the reel to fall toward the ground. Once the releasing end of safety strap  15   b  has been released and allowed to unwind to the ground, the hunter gathers up the entire length of safety strap  15   b  and arranges it so that it runs over one shoulder front of his body, and through one or more belt loops at the waist of his full body harness. At this point, it is important to note that the hunter is being suspended by tether  28 . 
         [0038]    When the hunter is ready to lower himself to the ground, he reaches above his head with one hand and grabs the releasing end of safety strap  15   b . Simultaneously, his other hand should grip the portion of the safety strap near his waist. The hunter then releases the braking surface  21   a  of controlled descent device  5  by firmly pulling safety strap  15   b  with the hand above his head. As described above, this tension on safety strap  15   b  actuates the cam lever  21   b  causing braking surface  21   a  to disengage and allow safety strap  15  to travel through the controlled descent device. The controlled descent device and the satchel then trolley&#39;s along the safety strap until the hunter has reached the ground. The hunter controls his rate of descent by squeezing on the safety strap with the hand near his waist belt loops. The tighter the hunter squeezes, the slower the rate of descent. Descent can also be arrested entirely by releasing tension on safety strap  15   b  with the overhead hand and allowing cam brake  21  to re-engage. 
         [0039]    While the present invention has been disclosed in terms of a preferred embodiment and variations thereof, the invention is not limited to the specific embodiments described herein. The scope of the invention is limited only by the appended claims and their legal equivalents and may encompass additions, deletions and modifications to the disclosed embodiments and its variations.