Patent Application
20060061050
This invention is in the field of mechanical and molded plastic devices, and relates to a convenient and lightweight sled for use by military or rescue personnel in transporting injured people, or by hunters, rural dwellers, and others for hauling heavy loads, such as firewood, deer or other heavy game, etc.
People in various situations could benefit substantially from having a simple, convenient, inexpensive, collapsible and easily-transported device that can help transport an injured person, or drag a heavy load.
As one class of circumstances, people such as soldiers, rescue workers, and emergency medical technicians often need a lightweight transporting device that can be hand-carried over uneven terrain (such as through a forest or wetland, down an embankment, etc.), to locations where wheeled gurneys cannot reach, without the weight and cumbersome inconvenience of large and stiff “backboards” of the type carried by ambulances. As one example, soldiers on foot patrol in a hostile area cannot realistically carry or drag around a backboard, for evacuating someone who has been injured by a bomb or attack; similarly, if a rescue person or team must carry a backboard a mile or more into dense woods, to rescue an injured hunter, the weight and awkwardness of the backboard can lead to serious fatigue in the rescuer(s).
In addition, people who live in rural areas, and people who hunt, could benefit from having a simple, convenient, inexpensive, collapsible and easily-transported device that can help an unaided person haul and drag a heavy load. For example, someone who owns a farm, ranch, or cabin may need to haul firewood, from a dead tree, a substantial distance through woods or fields that cannot be crossed by a car or truck, to reach a dwelling, shelter, or vehicle. As another example, a hunter who has killed a deer in a forest may be miles from the nearest road.
Currently available devices for assisting in that type of hauling and dragging are inadequate. As one example, “game haulers” for transporting deer and other large game have been developed, which are comparable to a wheelbarrow except with a frame, rather than a basin. These typically are made of tubular or angled bars made of steel or aluminum, with air-pressured tires that typically have diameters of at least about 15 inches, to help a hunter pull a deer carcass over logs, ruts, and other obstacles. Such wheeled-and-framed devices can be readily purchased over the Internet, and photographs can be obtained by a search for “game hauler”, using any general search engine. A similar framed device with hinges that make it collapsible is illustrated in U.S. Pat. No. 3,912,290 (Rich 1975). However, even if collapsed into a smaller size for transport, framed sleds or carts with large runners or wheels would occupy a major portion of the cargo space in a pickup truck bed, or in a sport utility vehicle, and likely weigh at least about 15 to 20 pounds, unless made of extremely expensive high-tech materials. Since the difficulties of pulling that type of bulky, awkward, and cumbersome device through a forest having numerous fallen trees, small creeks and ravines, and other obstacles are formidable and quite tiresome, no hunter wants to go dragging and pulling that type of sled for miles through a forest, without even knowing whether a hunt will be successful. Nevertheless, despite their drawbacks and disadvantages, those types of bulky and cumbersome wheeled-frame devices are among the most widely used “game haulers” available today, and hunters who hunt in groups often use cell phones, walkie talkies, and “global positioning satellite” (GPS) devices to allow one or two hunters to go trekking to a truck or car to get the “game hauler”, while one or two other hunters prepare the deer carcass (as used herein, terms such as “carcass” can also include body parts, meat, etc.).
U.S. Pat. No. 6,408,962 (Ryckman 2002) proposes an even larger, heavier, more elaborate, and more expensive type of powered sled. This proposed system has a heavy battery and a battery-powered motor, continuous belts around the wheels (for bulldozer-type traction), and a carrying platform that appears to be fairly high off the ground (which can lead to instability, tipping, and other problems, if a heavy load must be carried across a hillside or ravine, or over or under a fallen tree trunk). Anyone who looks at the drawings of that patent will wonder how many hunters have both the means and the desire to haul that type of system along with them, every time they go hunting. With regard to other uses such as hauling firewood, it would appear that wheeled carts that can be towed behind all-terrain vehicles have already satisfied the large majority of any needs for the type of powered sled shown in U.S. Pat. No. 6,408,962. Accordingly, that type of sled apparently has never been commercialized, and is not available.
A different type of transport device is sold by a company called Skedco, Inc. (www.skedco.com), and what appears to be an earlier and similar version of this sled is shown and described in U.S. Pat. No. 4,283,068 (Keyser 1981). This type of transport device was developed for rescuing and transporting people who have been injured. Briefly, it comprises a flexible sheet of a plastic material that has been provided with securing straps and handle straps. The straps generally pass through metal grommets to reduce the risk of tearing the plastic, and reinforcing devices near the “head” of the plastic sheet (apparently by rivets) reduce the risk of tearing the sled if a person being rescued must be lifted out of a dangerous location in a near-vertical orientation, or if a loaded sled must be pulled and dragged across a rough surface or over a long distance.
The “Sked Rescue System” is the closest prior art known to the Inventors herein. However, that system also suffers from certain shortcomings that limit its use, including its weight and bulk. According to Skedco's 2004 product catalog, the “Sked Basic Rescue System” weighs 19 pounds, and photographs in the catalog make it appear that the unit, when rolled up and stuffed into a carrying sleeve, approaches the size and bulk of a golf bag. Clearly, no hunter would want to hike into the woods, searching for deer, carrying an extra set of equipment that weighs nearly 20 pounds and is nearly the size of a golf bag. Similarly, soldiers on foot patrols in hostile areas are already heavily weighed down by weaponry, protective equipment, communications gear, and enough supplies to cope with a range of emergencies and contingencies, and it is not feasible or realistic to require soldiers under those types of conditions to carry an additional 19-pound load that is nearly the size of a golf bag.
In addition, if a natural disaster, terrorist bombing, or other major crisis occurs that causes numerous casualties, most types of vehicles (such as armored vehicles, helicopters, etc.) could not easily carry more than a few such devices, in addition to everything else they would need to be carrying.
For these and other reasons, although the plastic sleds made by Skedco have become important in rescue and retrieval operations, they rarely are carried into field situations as a matter of routine, before they are known to be needed. Instead, they normally are stored at supporting sites (such as field hospitals for military use, and police, fire, or ranger stations for civilian use). If and when they are carried in land vehicles, the vehicles rarely carry more than one sled, because each unit takes up substantial space and volume.
It also should be noted that the starting price (without any additional options) for a Sked Basic Rescue Unit is over $500. While that price might be justified for military or other rescue use, or for keeping a unit available at a ranger station or other remote location on a “standby” basis, hunters would not pay over $500 for a sled that weighs roughly 20 pounds and would need to be carried or dragged for miles, without knowing whether it would even be needed on a hunting trip. Therefore, Skedco-type sleds are not advertised, sold, or used for hauling firewood, heavy game, or other loads that have nothing to do with rescues or emergencies.
Accordingly, one object of this invention is to disclose and provide an improved design for a convenient and lightweight sled for use by hunters, rural dwellers, and others, for hauling game, firewood, or other heavy loads through areas that may be heavily forested with difficult terrain.
Another object of this invention is to disclose and provide an improved design for a thin, flexible, lightweight hauling sled that will take up very little space and cause no significant inconvenience, if placed in the bottom of a truck bed or SUV or other cargo compartment of a vehicle, before other equipment and supplies are loaded on top of it, and which can also be used to provide a waterproof cover and/or a rooftop carrier on a car or truck, if secured on top of other equipment and supplies.
Another object of this invention is to disclose and provide a hauling sled that is so lightweight and flexible that it can be rolled up and carried easily, for miles, by any healthy and vigorous hunter or hiker, in a manner comparable to a bedroll tied to a backpack.
Another object of this invention is to disclose and provide a hauling sled that is lightweight and flexible, and that can also be adapted and used for additional purposes during a hunting or camping trip, such as to provide a lightweight insulated groundcover device that can keep a sleeping bag warmer on frozen ground.
Another object of this invention is to disclose and provide a combination of a hauling sled, and a harness that can be affixed around the chest or waist, to allow a person to drag a heavy load on the sled without tiring the arms, hands, or shoulders, and while instead exerting maximum pulling force by using the legs and hips.
Still another object of this invention is to disclose and provide an improved type of lightweight, inexpensive, and convenient hauling sled that can be adapted for rescue, evacuation, or other emergency use, such as for transporting injured people, invalids, or people in similar need of assistance.
These and other objects of the invention will become more apparent through the following summary, drawings, and detailed description.
Improved lightweight and inexpensive sledding devices are disclosed, for transporting injured people or heavy loads. These sleds are made primarily from a single sheet of tough but flexible plastic or similar material. Two approaches are disclosed for reducing the risk of tearing the plastic during use, in ways that allow such sleds to be lighter and more compact than previously available.
One approach involves passing a rope or strap through a hole in the plastic sheet, and affixing the rope or strap directly to a load, such as one or more pieces of firewood, a deer carcass, etc. This approach imposes the towing forces directly on the loaded material, while keeping the sled affixed to the underside of that material. These types of sleds are referred to herein as “ultra-light” sleds.
The other approach, which can provide stronger sleds referred to herein as “rescue sleds”, uses a strong strap that passed through slots around the periphery of the sled. This enables a looped strap to distribute tensile loads and stresses around and across a sheet of plastic, in ways that avoid tearing the plastic sheet. A strong peripheral strap can also provide secure handholds around the sled, allowing several people to lift and carry an injured person in a manner comparable to a “backboard”, but without the bulk, weight, or inconvenience of backboards.
These enhancements allow major reductions in the weight and size of either type of sled. For example, a complete rescue sled (including straps and buckles) weighs only about 6 pounds, compared to nearly 20 pounds for prior plastic rescue sleds. In addition, rescue sleds as disclosed herein can be rolled into a thickness smaller than a standard roll of paper towels; by contrast, prior plastic rescue sleds have carrying sizes that resemble conventional golf bags.
The reduced size and weight of both types of sleds can allow hunters, soldiers, and others to carry these sleds for miles, on foot, secured to a conventional backpack, thereby making them available, on site, immediately when they are needed. By contrast, prior types of rescue sleds usually must be kept in a vehicle or base site, which can lead to substantial and even fatal delays before a sled can be delivered to the site of an emergency so it can be used.
In one preferred embodiment of this invention, illustrated in
After this type of sled was developed and tested, the Inventors recognized that it could be enhanced in ways that provide greater strength and adaptability, to a point of enabling a new and different use, for emergency, rescue, or similar transport of people who have been wounded, injured, etc. For convenience, this type of enhanced and strengthened sled is referred to herein as a “rescue sled”. It is created by using a combination of: (i) a layer of plastic, which can be thicker and stronger than would be preferred for an ultra-light sled, and (ii) a strong strap, such as a nylon strap with a width of half an inch or more, which can have hundreds or even thousands of pounds of tensile strength. The strap is laced through a series of holes cut through the main sheet, in a way that securely affixes the strap around the periphery of the sled. This type of sled is described below under the heading, “Rescue Sleds with Peripheral Straps”.
Both classes of sled devices disclosed herein are substantially lighter than any previous similar known devices. Weight is a crucial factor for such sleds, and rescue sleds can weigh significantly less than about 5 kilograms (about 11 pounds); indeed, a preferred rescue sled, including the reinforcing strap, weighs only about 6 pounds, which is less than 3 kg. Such sleds also can be rolled into cylindrical form with a diameter less than about 25 cm (10 inches); indeed, a preferred rescue sled can be rolled into a cylinder than 15 cm (6 inches) thick.
In either type of sled, the plastic or polymer sheet can be made from high-density polyethylene (HDPE) or other low-cost plastics or polymers. Sheets of HDPE and various other plastics that can be evaluated for use as disclosed herein are readily available in a range of suitable thicknesses, including sheets that already have both: (i) a smooth surface on one side, which can provide a bottom sled surface that will minimize friction and drag; and (ii) a knurled or otherwise textured surface on the other side, which can reduce and minimize slippage, sliding, and other unwanted motion by a person or other load riding on the sled.
Alternately, the sheet that comprises the main component of either type of sled can be made from a strong synthetic fabric that has been coated or impregnated with a plastic material; as an example, a search of any Internet search engine using “420D” and “nylon” will lead to manufacturers and sellers of “ripstop” nylon fabrics that are impregnated or coated with a waterproof plastic, having one smooth side and one textured side, available in various thicknesses.
Still other materials with greater toughness or other elevated or even extreme performance traits also can be used, and may be preferred for military or other uses involving high levels of danger and risk. As examples, materials made from polyaramids (widely sold under the trademark KEVLAR) and “ballistic nylon” are strong enough to be used in bulletproof vests and other devices. Accordingly, a sled as described herein might be exceptionally useful in helping soldiers protect themselves if ambushed, pinned down in a firefight, exposed to gunfire if they try to rescue someone, or otherwise placed in danger. In addition, if desired, a sled as disclosed herein can be provided with, or accompanied or supplemented by, one or more optional frame or support components, to allow the sheet of material to be used for various additional purposes (such as, for example, a cot for sleeping, a shield, a windbreak, etc.).
In either ultra-light or rescue sleds, any of various means can be used, if desired, to reinforce any holes or slots that are punched, drilled, cut, or otherwise passed through the sheet of material that is used to make a sled. For example, conventional grommets (also called eyes, eyelets, or similar terms) can be inserted into such holes. Typically, grommets made of a metal such as brass are secured by placing two halves with different shapes on different sides of a sheet, and using compression to press the two halves together in a way that causes either or both of the pieces to permanently bend, while grommets made of yieldable plastic typically use “snap” fittings, in which a ring or ridge on one piece fits into a groove on the accommodating piece. Alternately, reinforcements for the holes or slots can be provided by using ultrasonic energy, heat, or glue to securely affix O-rings made of flat plastic to either or both sides of the sheet of material that provides the main body of a sled.
As another optional means for reinforcing holes that pass through a sheet of plastic, such holes can be made by using a heated punch or blade, comparable to a soldering iron. A small quantity of plastic that is heated by the hot punch or blade will melt, during the punching or cutting operation; then, after the heated punch or blade is removed, the melted plastic will cool and solidify, forming a thickened ring of plastic surrounding the hole that has been created.
It also should be recognized that HDPE plastics and most other types of materials contemplated for use herein can be coated or impregnated with chemicals and/or films to provide various traits and benefits, if desired. For example, various known chemicals can reduce friction on the bottom surface of a sled; other known chemicals can render a material more resistant to degradation by ultraviolet radiation or chemicals; and various film-type coatings can make a surface highly reflective, which can allow warming uses (using reflected sunlight), use as a windshield screen to keep the interior of a vehicle from becoming too warm, or use in signaling, to draw the attention of a search or rescue vehicle that may be a long distance away.
It should also be recognized that ultra-light sleds, and rescue sleds, effectively establish a range of useful and convenient lightweight sleds made of flexible plastic sheets. Accordingly, after ultra-light and rescue sleds are described below, various types of “midpoint” sleds are described that can combine and/or balance certain components and traits of the two “endpoint” embodiments, to provide additional options and alternatives.
Throughout the discussion below, descriptive terms that tend to suggest physical shapes for conventional and well-known devices (such as strap, slot, etc.) are used for convenient description of preferred embodiments, and are not intended to limit the invention to certain particular types of components. As one example, in rescue sleds, nylon straps at least about ½ inch wide (preferably about ⅝ to 1 inch, with relatively flat cross-sections for reduced weight and bulk) are generally preferred over ropes with circular cross-sections. There are two reasons for this preference: (i) wide straps can be grabbed by uncovered hands and pulled, lifted, and carried over longer distances, with less discomfort and fatigue in the hands, compared to ropes; and, (ii) if handled properly, widened straps can help distribute tensile and tearing stresses across a wider area of plastic surrounding a hole, thereby reducing the risk that a hole will become torn.
However, despite the preference for straps over ropes, anyone skilled in the art will recognize that any type of rope, cable, lightweight chain, or similar item that can withstand the tensile stresses involved can be sufficient for carrying out the roles and functions of straps as described herein. In addition, it must be recognized that there are overlaps between various terms that describe physical objects of this class. For example, people can argue about the implications of terms such as straps versus belts, and whether the real difference between them depends on the type of buckle or other connector that is used, rather than on the tensile member itself; similarly, if a braided strap/rope has (or can adopt) an oval cross-sectional shape, somewhere between the circular shape of a rope and the flattened shape of a strap, it might be called either a rope or a strap.
Accordingly, to avoid unhelpful disputes over semantics while describing and claiming the invention as clearly as possible, the description herein uses various terms (such as “strap”) to refer to certain preferred embodiments, while the claims in some cases use other terms (such as “tension-bearing reinforcing component”, which encompasses and includes straps, ropes, belts, cables, chains, etc.).
Similarly, the description herein uses the term “slot” to describe the preferred type of elongated hole that passes through a sheet of material, which enables a strap to pass through the sheet of material. However, slots also can be referred to by other terms, such as holes, openings, slits, gaps, passages, etc. (they might also be referred to as orifices, apertures, or other terms, although some people might argue that “aperture” requires that an opening must be adjustable in size, and “orifice” requires that some type of fluid or other material must pass through the opening). Accordingly, the term “hole” is used in the claims, since it is a broad term that is not limited to any particular size, shape, or structure. In general, “hole” is used broadly in the claims, to include any type of passageway that has been cut, drilled, stamped, molded into, or otherwise created or provided in a way that enables a strap, rope, or similar item to pass through a sheet of material.
Despite their exceptionally light weight, these sleds can be very tough and durable, even when made of an inexpensive plastic such as HDPE. To provide a “benchmark” standard for toughness that can distinguish rescue sleds from the types of flexible plastic toy sleds that are sold for children to play on after a snowfall, a strength and durability test is set forth herein, which should be regarded as specifying a minimum level of toughness to allow a sled to be suitable for potential use in rescue operations. According to this threshold text, a sled should be strong, tough, and durable enough to allow a distributed load (as can be provided by several sandbags, arranged on the sled in a manner that roughly resembles the torso, head, and legs of a person), weighing an aggregate of 90 kilograms (about 200 pounds), to be dragged across conventional asphalt paving (i.e., an asphalt composite having exposed bits of gravel, as used for conventional street paving) a distance of at least 200 meters.
Asphalt paving, with exposed bits of gravel, acts in a manner comparable to a super-coarse sandpaper, and it will actively and aggressively grind and cut at the underside of a sled carrying a 200-pound load. Therefore, it poses a tougher challenge than will be encountered in most types of outdoor use (such as dragging a load through a forest, across ground surfaces such as dried leaves, grass, etc.). However, in military situations, if a sled must be used to pull a wounded soldier to safety during an ambush or other attack, a dragging distance of 200 yards would almost always be sufficient to allow the wounded soldier to be dragged to an intermediate position of relative safety, where he can be kept sheltered from bullets, shrapnel, or shells while an armored or emergency vehicle attempts to reach him. For both reasons, the durability test specified above provides a “benchmark” level, for evaluation and comparison purposes, that is fully reasonable.
In addition, “dragging distance” tests, using sandbags to determine how many meters or yards a 90 kilogram distributed load can actually be dragged across asphalt paving before a hole with a fixed diameter (such as 2 cm) is worn through the sled, can be used to provide a simple and direct numerical indicator of how tough and durable a sled (or a candidate sled material) actually is, under reasonable conditions reflecting usage.
Ultra-Light Sleds with No Peripheral Straps
As summarized above, an “ultra-light” sledding device 100, illustrated in FIGS. 1 and 2, comprises a flexible sheet 102, which can be rolled up and carried easily above or beneath a conventional backpack. For example, such sheets can be made of HDPE plastic, plastic-coated fabric, or similar materials, with a thickness that allows the sled to be rolled into a tube with a diameter of about 4 inches or less, weighing about 4 pounds or less.
This type of sled is designed mainly to aid in the dragging and hauling of inert loads, such as a load of firewood, a deer carcass, etc. One of the features of ultra-light sleds is that a rope, strap, or other device (such as a lightweight chain, which can be carried by all-terrain vehicle) can be secured directly to the load, rather than to sheet 102. This effectively allows the rope, strap, etc. to directly pull and drag the load, while sheet 102 is merely strapped and held in place beneath and partially on the sides of the load. This approach is very different from tying a rope or strap to a sled, and exerting a strong pulling force on the front of the sled itself, since a strong force pulling directly on a relatively thin sheet of plastic or similar material would create a high risk that the material would tear.
Accordingly, ultra-light sled 100 is designed and suited for use with loads that will not be damaged or injured, if a rope or strap is secured directly to the load.
As illustrated in
In a preferred embodiment that would be useful for a majority of intended uses, ultra-light sled 100 can be roughly 1.7 to about 2.2 meters long (about 68 to about 86 inches), and roughly 0.6 to 1.0 meters (about 24 to 39 inches) wide, not including any side handles. The overall shape can be created by various known means, such as die cutting or stamping, guided-cutting using a blade, scissors, or laser beam, etc.
While the details of construction can be varied, one preferred design, described for illustrative purposes, can use a single sheet of HDPE or other selected plastic that has sufficient tear resistance, puncture resistance, and preferably stain resistance. If HDPE is used, it preferably should have a thickness of about 0.03 to about 0.1 inch (roughly equal to 1 to 2 millimeters), for most uses; however, it should also be recognized that thicker and heavier materials can be used if desired, and can be designed to also provide additional advantages. For example, a layer of low density foam-type material coated with a toughened “skin” layer on either or both sides can be used if desired, and this type of sled can also provide insulation and warmth in cold weather, since its size and shape will render it well-suited for providing a slightly padded insulating layer that can be placed beneath a sleeping bag, on top of frozen ground or a cot or other surface.
A knurled or other roughened surface preferably should be provided on the upper surface 110 (i.e., the load-contacting surface) of sled 100, to decrease the risk that a carcass or other heavy load will slip or slide across surface 110. Bottom surface 112 preferably should be smooth, to minimize friction, drag, and resistance while a load is being dragged or hauled.
A plurality of reinforced side handles 120 is provided along both of the two opposed side edges 122 and 124 of the main body of sled 100. These handles normally will not need to withstand heavy tensile stresses, since they will not be used for dragging, and instead will be used mainly for pulling up the sides of the sled around a deer carcass, load of firewood, etc. Proper securing of ropes or straps to the side handles 120 will effectively wrap sled 100 into a roughly cylindrical configuration, to minimize friction and drag during a hauling operation.
Since the side handles 120 do not need to withstand heavy tensile loads, they can be provided by the same sheet of plastic used to create the main body of sled 100, if desired. One suitable design, shown in
The step of securing the sled to an inert load can be carried out in any suitable manner, by the person using the sled. For example, a deer hunter walking into a forest can carry a bundle of thin but strong nylon cord, along with a hunting knife. If the hunter bags a deer, he or she will cut off and use as many segments of cord as deemed necessary to secure the sled to the deer carcass (or to any segments of meat that have been cut from the carcass).
As another example, if a farmer, rancher, or cabin-owner wants to obtain a load of firewood from a dead tree (after the tree has been safely felled and cut, using a chainsaw), the person is likely to drive a pickup truck, tractor, farm cart, all-terrain vehicle, or other vehicle as close as possible to the load of firewood, and then use ropes, chains, cables, bungee cords, or any other available means to secure the sled to each of several loads of wood. In this type of operation, the farmer, rancher, or other person may use a rope that can be up to hundreds of yards long, to reach a fairly long distance into a wooded area or other location where a pickup truck or other vehicle cannot be driven. The sled will be used, not to drag the load of wood all the way back to a house or barn, but merely to drag it to a location where the wood can be loaded onto a truckbed, trailer, cart, etc. Similarly, a sled can enable a rancher, farmer, or cabin owner to use muscle power to drag a load of wood to a spot where a rope or cable from a vehicle or winch can reach the sled. At that point, the person connects the rope or cable to the sled, and lets the vehicle or winch do the rest of the towing work, to drag the load to a spot where it can be loaded onto the vehicle.
In either case, the securing of the sled to the load can use simple or adjustable knots, belts or straps with buckles or other adjustable securing devices, or any other suitable means.
One of the features of sled 100 is that the two towing holes 140 and 142, near the front of the sled, do not need to be heavily reinforced. Instead, one end of a rope or strap 190 can be passed through either of the two holes 140 or 142, and then wrapped securely and/or tied around some part of the load (such as the neck or hindquarters of a deer). The end of the rope is then passed through the second towing hole 140 or 142. Both ends of the rope or strap will be tied or otherwise affixed, in any suitable manner, to any suitable type of handle, harness, vest, belt, or similar device (or to a loop, clip, or other affixing means at the end of a rope or cable that is attached to a nearby vehicle or winch). In this manner, when rope 190 is pulled hard enough to drag the load, the large majority of the tension will be exerted on the load, rather than on the relatively thin sheet 102 of sled 100.
As mentioned above, additional towing holes 144 and 146 can be provided near the back end 106 of sled 100. This would allow sled 100 to simply be turned around, reversing the front and back ends, if either or both of front end towing holes 140 and 142 ever become torn (alternately, an owner or user can simply cut new holes through the flexible sheet, near the tail end, if the need arises). In some cases, this can effectively double the useful life of a sled (or increase it even more, by warning a user that a certain load is too heavy to haul in one load, and needs to be divided into smaller loads before the operation is commenced again).
Rescue Sleds with Peripheral Straps
After the “ultra-light” sled system described above was developed and tested, the Inventors recognized that it could be enhanced, in ways that provide greater strength, to a point of enabling a new and different type of use, for emergency transport of people who have been wounded or injured, or who otherwise need emergency, rescue, or similar transport.
This type of enhanced sled (referred to herein as a “rescue sled”) can be provided by combining: (i) a somewhat thicker and stronger sheet of material than would be preferred for most types of “ultra-light” sleds, with (ii) a strong strap, such as a nylon strap having a width of half an inch or more. The strap is “laced” through a series of slots or other holes that have been cut through the sled, in a way that securely affixes the strap around the periphery of the sled.
This arrangement provides two major benefits: (1) it allows a strap, which can withstand hundreds or even thousands of pounds of tensile force, to distribute any tensile stresses and forces around the periphery and area of a flexible sheet, in ways that minimize any tearing or other stresses that are imposed on any specific part of the flexible sheet; and, (2) it allows strap segments which are exposed on the upper surface of the sled to be used as handles, in a way that can allow a team of two, three, or four people to lift and carry an injured person (or other load) on the sled.
Accordingly,
While rescue sleds 200 and 300 are designed and suited for uses such as emergency transport of an injured person, they also can be used for transporting other loads, such as firewood, a deer carcass, building materials, etc.
Sled 200 in
The spacing of strap slots 220 is important, and requires attention to both: (i) smaller “spacing segments” 222 between each of the two slots in a pair of strap slots 220, having a width or length designated as variable “A” in
The width “A” of the smaller spacing segments 222 is important, because segments 222 will effectively provide the means by which the sled body 212 hangs from, and is lifted and supported by (or is pulled and dragged by), a peripheral strap 320 as shown in
In analyzing the numbers and spacings of strap slots 220 that should be provided for a lightweight rescue sled, it is assumed that the main body of the sled is created by simply cutting slots into a sheet of HDPE or other plastic, without using grommets, welded O-rings, or other devices to reinforce the slots. This approach is entirely feasible, and can provide highly useful sleds with minimal cost, weight, and bulk when rolled up and carried. However, the strap slots can be reinforced if desired, and if such reinforcements are provided, any numbers and spacings suggested herein can be adjusted accordingly.
It should also be noted that a slot can be cut in a way that will generate one or two small flaps, which will remain attached on either or both sides of the slot. If this is done, the small flaps can be scored and folded back, in a way that can help reinforce the slots.
For illustrative purposes, to avoid rendering the drawing more complicated,
Preferred numbers of paired slots for most rescue sleds will range from at least 9 pairs (which can provide 4 handholds on each side, to allow a team of 4 people (two people on each side) to lift and carry a sled with an injured person on it), preferably at least 11 pairs, and even more preferably at least 13 pairs, up to a maximum of about 15 or possibly even more pairs. If more than about 15 or possibly 17 pairs of slots are provided, they will tend to reduce and limit the “handle segments” 224 (which have the “B” widths shown on
As indicated above, each pair of strap slots 220 creates a relatively small “spacing segment” 222 between those two slots. Preferred widths “A” for spacing segments 222 will depend to some extent on the strength of the material used to make the sled; for materials such as unreinforced HDPE, the width of each spacing segment 222 generally should be in a range from about 3 to about 5 inches.
If the number of paired slots is fixed, larger widths for spacing segments 222 are not likely to provide major increases in strength and durability for the sled, because tearing actions will not be affected substantially by the widths of spacing segments 222. Instead, tearing forces will focus on a corner or edge of a spacing segment, and a tear will begin if the forces (which will be increased by jostling motions) exceed a certain level, regardless of how far the tear might need to travel before it can break completely through a spacing segment. Accordingly, the number of paired slots (and spacer segments) will have more direct and important effects on tearing and durability than the widths of the spacer segments. As a result, the highest practical and “comfortable” number of paired slots will be preferable, and a preferred embodiment of the sled herein uses 15 slots.
That number may vary, for sleds made of other types of materials, and for sleds having reinforced strap slots. Accordingly, it is possible to carry out computer modeling, to determine optimal numbers and spacings of paired slots around the periphery of a rescue sled made of any particular type or thickness of material. However, that type of modeling can only approximate a number of variables that will arise under field conditions, especially in emergencies. Therefore, any optimization of exact sled dimensions, for any particular type of sled made of a particular material with known dimensions, preferably should be carried out by testing under realistic field conditions, such as by using soldiers or others to haul and drag, or to lift and carry, volunteers or weighted loads over substantial distances in various types of terrains.
The reference to a “peripheral” strap 320 is descriptive of the preferred and illustrated embodiment, but it is not intended to be limiting. In particular, any of several variations could be chosen and used, which would raise questions as to whether the resulting strap is still “peripheral”. As one example, a strap could take a “shortcut” across the back end of a sled, at a location that could be 10, 20, or even 30% of the distance toward the front of the sled. As another example, a reinforcing strap could be provided in two parallel segments that would travel down the sides of the sled, but which would not traverse the sled and link together with each other at the tail end of the sled. These approaches generally are not preferred, since they would not provide the same level of strength and reinforcement as the truly peripheral arrangement shown in
References herein to a reinforcing strap that is “coupled” to a sled or sheet of plastic are intended to indicate that suitable means are used to attach, affix, secure, or otherwise couple a strap to a sled with sufficient strength to enable and cause the sled to be lifted, dragged, or otherwise moved and transported, when the strap is moved. Such means can be provided conveniently and inexpensively by lacing strap 320 through strap slots 220, as illustrated in
Towing Straps, Loops, Handles, and Belts
Any of various types of straps, ropes, or similar devices, which can be provided with various types of handles, loops, clips, or other gripping, coupling, or securing means, can be adapted for pulling and dragging a loaded sled as disclosed herein.
For example, a handle made of a relatively hard material that can be grasped by both hands, and that will not collapse and squeeze the hands (such as commonly used to tow water skiers), can be adapted for use as disclosed herein. However, handles that are gripped by the hands will cause tiring and fatigue of the hands, shoulders, and arms, especially if used to pull a load that may weigh hundreds of pounds over substantial distances.
Accordingly, a better class of towing device can be provided by a strap having a width of at least about 1 inch, with a small loop in the end. A much larger loop having any desired overall size can be created merely by pushing a segment of strap through the small loop. If desired, a person's head and one arm can be inserted through the loop, effectively creating a shoulder harness that will rest next to the person's neck. This type of shoulder harness can be a major improvement over a hand grip, and if one shoulder gets tired, the loop can be shifted to the other shoulder. However, a shoulder strap also can cause fatigue of the neck and shoulders.
In addition, any efforts to drag a heavily-loaded sled by imposing a load on the arms, shoulders, or chest of a person doing the work will increase, rather than reduce, the amount of work that must be performed to cover a fixed distance. By way of analogy, if a segment of elastic material (such as a bungee cord) is inserted into a tow rope, a person using that rope to drag a heavy load a long distance would end up using energy to stretch the elastic in ways that don't help move the load. The elastic segment becomes a “damping” device that partially absorbs, dissipates, and wastes the energy that is spent stretching it. In a similar manner, if a man tries to use his arms and shoulders to tow a sled, his arm and shoulder muscles will not reduce the amount of work his legs must do; instead, the arms and shoulders will be like semi-elastic damping devices, inserted into a chain that would work better without them. Rather than helping, they will impede the translation of work (by the legs) into results.
Accordingly, a preferred method for dragging and pulling a loaded sled can be accomplished by placing a strap loop directly around the hips, preferably using a rolled-up blanket, vest, towel, or similar device to provide padding. Alternately, an oversized and/or padded belt which is ideally suited for this type of work can be provided by adapting the types of belts that have already been developed for supporting backpacks. Such belts are illustrated, in color photographs, on websites such as www.backpacking.net. Ideally, that type of oversized padded belt can be provided with up to four different attachment rings or clips, on the back, front, left, and right sides of the belt.
When the towing strap or rope is attached to a ring or clip on the back of such a belt, it will allow a person to exert maximum traction and pull while leaning and moving forward. However, if a difficult obstacle (such as a fallen tree, large rock, etc.) requires the person to turn around and watch what is happening while a loaded sled must be somehow pulled over, under, around, or through the obstacle, the rope can be uncoupled from the back ring and attached to the front ring. This will allow the person to pull the load while walking backward, watching and monitoring the sled as it maneuvers past the obstacle.
Similarly, if a heavy load must be dragged a long distance, the user can secure the rope or strap to either of the two side rings, and use a leaning-type walking for a while, similar to a swimmer doing a sidestroke for a while to rest the muscles that are used in freestyle (crawl) or backstroke.
Nothing can make it simple and easy to drag a large and heavy deer carcass (or a heavy load of firewood) a distance of a mile (or even several miles), through a heavily wooded area. Even under the best of conditions, that type of work can exhaust even a large, strong, vigorous man who is accustomed to physical labor. Accordingly, the goal of this invention is to provide a lightweight sled that will help someone drag a load as far as possible, under any given set of conditions, before having to stop and rest. Therefore, if a user can alternate a towing rope or strap between different attachment rings on different sides of a belt (alternately, if a simple loop in a strap in a rope is used, the user can simply relax and loosen the lop for a moment, and rotate his/her body to any desired angle), the person will be able to vary the loads and stresses that are imposed on different sets of leg, buttock, and hip muscles. This can allow someone to drag a heavy load a longer distance, before needing to stop and rest.
It should also be recognized that the type of towing and pulling motion that will be exerted on a sled as described herein will usually tend to lift up the leading edge of the sled, in a manner that will generate a curled or otherwise slanted, tapered, and/or rounded leading edge. This can make a dragging operation easier, while avoiding or minimizing any scooping, trenching, or similar unwanted actions in which the leading edge of the sled might catch or snag on dirt, leaves, stumps, branches, crop remnants, or other obstacles.
“Midpoint” Sleds, Halfway Between Ultra-Light and Rescue Sleds
In an alternate preferred embodiment, various types of “midpoint” (or hybrid, etc.) sleds can be designed and fabricated that will combine components and advantages from both of the two embodiments discussed above.
As an example, one type of “midpoint” sled can be provided with a relatively thin and lightweight peripheral strap or cord, such as a nylon strap having a width of only about ¼ inch, or a nylon cord or rope having a thickness (diameter) of only about ⅛ inch. Even though they are relatively thin, such straps or cords made of a material such as nylon can have tensile strengths of hundreds of pounds. Accordingly, they can provide additional strength to a sled without major increases in cost or weight, and they also can provide additional options for securing a bulky, cumbersome, and awkward load to a sled.
Other types of “midpoint” sleds can be created by “welding” a reinforcing strip of plastic (or a set of reinforcing rings) to the peripheral rim of a sled, to provide additional reinforcement for the slots or holes that will penetrate the main layer of the sled and provide coupling means for a peripheral strap. This type of plastic “welding” can be done using ultrasonic energy input, which has been widely adopted in recent years for affixing two pieces of plastic to each other.
Similarly, metal or plastic grommets or similar devices can be used to reinforce any or all of the slots or holes that will penetrate the main layer of a sled.
Alternately or additionally, a heated tool (comparable to a soldering iron or heated blade) can be used to cut and/or melt a slot or hole through the main layer of a sled, in a way that creates a melted ring of plastic material around the heated tool. When the ring of melted plastic cools and hardens after the tool is removed, it will create a ring of hardened reinforcing plastic around the slot or hole, thereby reducing the risk of tearing.
Thus, there has been shown and described a new and useful class of lightweight and flexible sleds for transporting inert loads, or humans in need of transport. Although this invention has been exemplified for purposes of illustration and description by reference to certain specific embodiments, it will be apparent to those skilled in the art that various modifications, alterations, and equivalents of the illustrated examples are possible. Any such changes which derive directly from the teachings herein, and which do not depart from the spirit and scope of the invention, are deemed to be covered by this invention.
This application claims priority under 35 USC 119(e) based on provisional application 60/611,255, filed on Sep. 20, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60611255 | Sep 2004 | US |
