Abstract:
A litter comprising two arm shafts. The first arm shaft being the lock receiving frame arm and having a first locking member and a locking shaft having a second locking member. The second and first members interact to releasably retain the two arm shaft adjacent one another. Strap retaining means, each interacting with a strap, are place separately along the first arm shaft. The second arm shaft is a strap receiving arm with at least one ratchet dimensioned to receive a strap. A one torque limiter prevents each strap from being tightened beyond a preset tension point. A ratchet shaft, with a handle, is within the second arm shaft and in rotatable connection with each ratchet. Each arm shaft has a lockable handle rotatable around each end, able to rotate to serve as handles or legs.

Description:
FIELD OF INVENTION 
     This invention relates to a medical stretcher with improved loading/securing mechanism, and improved dragging mechanism. 
     BACKGROUND OF THE INVENTION 
     A stretcher is a medical device used to carry casualties or an incapacitated person from one place to another. Various embodiments of stretchers are known and used in the art. 
     The evacuation of injured or incapacitated persons in rural, underdeveloped, disaster, and war affected terrains, where commercial medical stretchers are incompatible or useless has been a unresolved problem. Currently available stretchers for rural, underdeveloped, disaster and war affected terrains, including those currently used by the U.S. military, require two persons to effectuate an evacuation. Furthermore, these stretchers are excessively bulky, heavy, and difficult to operate under normal extreme conditions presented in disaster and war affected terrains. 
     In civilian use, many people enjoy participating in outdoor activities such as running, hiking, mountain climbing and the like, and one of the drawbacks of many of these activities is the danger of serious injury or illness in an area that is difficult for emergency personnel to reach. When an injury or serious illness does occur in a remote or hard to reach location, it can be very difficult to safely transport the injured or incapacitated person from the remote location to a medical facility. 
     During combat, medical treatment facilities are typically located in a secure area separate from the battlefield. To receive medical care, the injured and wounded must be transported from the battlefield using conventional military issued litters. The survival and recovery of these individuals significantly depends upon extraction time; therefore it is desirable to design a litter that can be easily carried and quickly assembled under combat conditions to facilitate the extraction process and enable patients to more quickly obtain medical treatment. 
     Current U.S. military issued litter systems are heavy, bulky, often difficult to assemble and can be a substantial liability to the extraction process. These litter systems typically remain on transport vehicles during field exercises because of their prohibitive large weight and size. Therefore, litters are often not readily available to the military unit while on combat missions. 
     Although lighter weight structures have been designed the remaining issues to be resolved. The disclosed stretcher provides a number of advantages over prior art stretchers, with the primary improvements being in the strapping system and adjustable legs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a top isometric view of the entire stretcher using the lock, strap spreader, and ratchet system. 
         FIG. 2  is an isometric view of a frame arm with a lock. 
         FIG. 3  is an isometric view of the lock, straps, and strap spreader. 
         FIG. 4  is an isometric view of frame arm with strap ratchets. 
         FIG. 5  is an isometric view of a strap ratchet. 
         FIG. 6  is a side view of the internal ratchet shaft and ratcheting lever. 
         FIG. 7  is a side view of the internal ratchet shaft and handle lever. 
         FIG. 8  is an isometric view of a handle. 
         FIG. 9  is an isometric view of two handles mounted on frame arms. 
         FIG. 10  is a front cutaway view of the handles as legs. 
         FIG. 11  is a front cutaway view of the handles as stabilizing legs. 
         FIG. 12  is a front cutaway view of the handles as handles. 
         FIG. 13  is a front cutaway view of the handles as connectors for blankets or a helicopter. 
         FIG. 14  is an isometric view of the stretcher with handles as connectors with a ballistic blanket. 
         FIG. 15  is an isometric view of the stretchers with the handles as connectors for a helicopter. 
         FIG. 16  is a side view of a handle with shock-absorbing springs. 
         FIG. 17  is a top view of a handle and frame arm with connectors. 
         FIG. 18  is a top view of a handle and frame arm with connectors. 
         FIG. 19  is a top view of a handle and frame arm with connectors. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows the disclosed stretcher  100  in a lock and closed position. The body straps  202 ,  204 , and  206  have been pulled from the lock arm  200 , adjacent to frame arm  102 , to extend across the stretcher  100  to be secured at their appropriate places on the second frame arm  302 . 
     As illustrated in  FIG. 2 , the stretcher has a lock-receiving frame arm  102 , which has the receiving end of a lock  104 . The frame arms  102 ,  200  and  302  are preferably metal, but can also be any material of sufficient strength and rigidity such as composite, plastic or carbon fiber. The receiving end of the lock  104  can be built directly into the frame arm  102  for increased strength, but it is preferred for the receiving end of the lock  104  to be attached to a sleeve  106  that wraps the frame arm  102 . This is similar to existing stretchers. The sleeve  106  can be of any material of sufficient strength, including metal, plastics and fabrics such as nylon or polyester. Because the stretcher uses a single-point lock rather than multiple locking points like traditional stretchers, the lock  104  will be taking more weight, and will need to be of sufficient build to support all of the occupant&#39;s weight without failing. A three-prong plastic snap lock and a car seatbelt lock are two examples of sturdy simple locks, although almost any style of lock can be used as long as it is quick to secure. 
     The lock arm  200 , as shown in  FIG. 3 , is designed to space the body straps  202 ,  204 ,  206  since there is only a single locking point. By spreading the straps over the length of the body, the stretcher occupant is better secured. The unit is not limited to three straps, and can use one or more straps. The lock arm  200  can be metal for increased rigidity, alternatively other materials such as plastic, composits or heavy fabric such as multiple layers of stiff nylon can be used to provide a lighter lock arm  202  while retaining durability and rigidity. The lock arm  200  has a lock  208  that connects to the lock  104  on the lock-receiving frame arm  102 . 
     The second frame arm is the strap-receiving frame arm  302  shown in  FIG. 4 . The strap-receiving frame arm  302  is connected to the lock arm  200  by the body straps  202 ,  204 ,  206 . The straps  202 ,  204 ,  206  connect to the strap-receiving frame arm  302  at ratchets  402 ,  FIG. 5 , built into the strap-receiving frame arm  302 . The ratchet system is similar to standard ratchet tie down straps used with vehicles. A standard home-use ratchet strap is rated for several thousand pounds, and will be more than adequate to secure a person, even one in full military gear. An important feature in the ratcheting system as used here is the use of a torque limiter. While less common than a standard ratchet, they are freely available on the market. Examples include the Ancra Torque Limiting Ratchet. 
     A torque limiter allows the strap tension to be set, and no matter how much ratcheting is done, the strap will not tighten beyond that preset tension point. This is important for two reasons. The first is that when two or more straps are used on the stretcher, due to the shape of the body the two straps will not be in the secured position at the same time. That is to say that the two straps will need to be different lengths, so a standard ratchet will not work as when one strap is secure, the others will be too tight or too loose. With a torque limiter on each ratchet, if there are three straps, each strap will stop tightening at the appropriate point, allowing the remaining straps to continue tightening until all of the straps are secure. The second reason this is important is that it removes all human error for tightening the straps. A human can tighten the straps too much, further injuring the occupant, or too little leaving them poorly secured. By having a torque limiter ratchet, each strap will be perfectly secured every time. 
     Shown in  FIG. 6 , one or more ratchets  511  are connected by a ratchet shaft  502  that runs through the strap-receiving frame arm  302 . At the end of the ratchet shaft  502  is a handle  504  that is used to turn the shaft  502 . In  FIG. 6 , the shaft  502  is turned by raising the handle into an upright position  505  and lowering it into a lowered position  504 . A variety of handles are possible, with an up/down handle as used by a standard ratchet strap being the most preferable. A turn-crank handle is another ideal example. In an alternate embodiment of  FIG. 6 , as shown by  FIG. 7 , the handle  602  is connected directly to the ratchet shaft, such that the section to be gripped when carrying the stretcher acts as the stretcher handle and ratchet handle which potentially eliminates the need for the changing gears  506  which redirect the handle movement to turn the shaft. 
     An additional benefit to this design over a traditional strap is that during a combat situation, the rescuer can tighten the straps while in a prone position, rather than having to stand over the body to adjust the straps. While in the prone position, the rescuer can tighten the straps without looking, and yet can never over-tighten the straps and injure the occupant. This makes the ratchet system potentially life-saving for the rescuer. 
     The ratchet system is designed to also be compatible with collapsible stretchers. In a collapsible stretcher the frame arms are made of several hinged shafts that lock together. Because there are multiple pieces, a single shaft  502  cannot be used. To solve this issue, at each break point in the strap-receiving frame arm  302  the shaft  502  ends in a toothed gear  507  and  509 . While there are multiple forms of gears that can be used, in the preferred embodiment the gear teeth are in the same plane as the shaft opening, and the gears have angled teeth. This will allow the two gears  507  and  509  to connect together and automatically align when the frame arm is put together. This forms a single shaft that that will turn all ratchets in the stretcher at once. Springs within the frame arm pushing the gears  507  and  509  towards the frame opening can be used to create additional tension and further secure the shaft sections into a whole. 
       FIGS. 8 through 13  show the handle system. The handle  802  rotates around the arm shafts  302 ,  102  into multiple positions. The curved  804  shape of the handle is important of use when dragging to prevent the handle from getting caught on ground obstacles. For further dragging performance, one or more wheels can be added to the handle. 
     Using the fabric body  1004  as a plane of reference, the handles  803  can be rotated into numerous positions. When the handle is at an approximately 270 degrees (“down”) angle, it is a leg handle  1002  and the handles act as legs for the stretcher, raising it from the ground. It should be noted that the stretcher can have other, shorter permanent legs as well. When the handle greater than 180 degrees (“horizontal) and less than 270 degrees (“down”) it is a stabilizing leg handle  1102 . The purpose of the stabilizing leg handle  1102  is to create a wider base for the stretcher when it is being dragged along the ground. As shown in the figure, a vertical leg  1103  has a much narrower base  1104  than the extended leg  1102 . This helps prevent the stretcher from flipping, and the rounded shape of the handle promotes easy dragging. If a stretcher is 2 foot wide, and has 6″ legs  1102 , by rotating the legs, we can add approximately 30-40% more width to the base over a traditional stretcher, dramatically improving stability. As shown in  FIG. 16 , if the stretcher is used for dragging, a handle  1602  can be fitted with springs  1604  to act as shock-absorbers. 
     When the handle is in an approximately 180 degree angle (“horizontal”) it is a handle  1202  that provides an easy grip for carrying the stretcher. It should be noted that in all positions the handles can be used for carrying. They can be individually adjusted to provide a range of heights to keep the stretcher level when people of different heights are carrying the stretcher. They different handle positions can also be used when, for example, the stretcher needs to be dragged low to the ground such as in a military situation where the rescuer must remain under cover. With a traditional stretcher of this style, it would be difficult to get a grip on the handle, whereas here the handle would simply be put into a 180 degree or less position. When the handle is at 180 degrees or less, it acts as a connection handle  1302 . As depicted in  FIG. 14 , thermal or ballistic blankets  1404  can be attached to the connection handle  1302  to cover the occupant and provide protection or comfort to the occupant. As shown in  FIG. 15 , a helicopter with a rescue cable  1502  can attach two straps  1504  (such that the stretcher is vertical) or four straps  1504  and  1406  (such that the stretcher is horizontal) connections to the connection handles  1302  for transportation. 
     It should be noted that while four handles would be the most common, two handles can be used, as can six or more. Also, each handle is independent of the other, such that the “rear” two legs could be in a wide position for dragging, and the “front” two legs in a horizontal position for easy grip by the rescuer(s). 
     The handle  803  is secured into the above positions via a locking mechanism. The locking mechanism can take many forms, but must be sturdy enough for use when all of the stretcher and occupant weight is being held by the handles and handle locks. It must also be quick to change the position of the handles. The locking mechanism must also not be such that it can accidently be released during transport of the stretcher. 
       FIG. 17  shows a spring push button  1704  on the arm  1706  and receiving holes  1702  on the handle.  FIG. 18  shows holes  1804  in the arm  1806  and a spring-loaded locking bar  1802 .  FIG. 19  shows an arm  1906  with holes  1904  with a handle having a grip-button  1902  that activates a spring-connected rod  1903  that connects to the holes  1904 . 
     While the above systems use springs and buttons with holes to connect, other systems are potentially viable. Tension can be used to attach the handle to the arm, for example with a system similar to a pipe clamp where the tightening screw is tightenable by hand with no tools.