Patent Application
20160331605
The invention relates to patient litters.
In medical emergencies and even in routine care it is often necessary to transport a patient from the location of the accident or injury to a place of medical care. This transport can take place in several stages, often starting with hand carrying by medical workers, then transitioning to a ground or air vehicle. During these different modes of transport, the patient must be secured under varying types of accelerations and loading. The types of loading include both handling loads and vehicle accelerations. During transport by hand, the loads are typically vertical and lateral jostling with the loads being supported at the litter handles. During transport by vehicle, the highest loads are forward and lateral generated by vehicle accidents with the loads being supported by the litter-to-vehicle restraints.
In addition to supporting the weight of the patient and the associated medical gear through the transportation loads, the litter must fold compactly when it is not being used. Current litter technology is based on frame structures. Frame structures are structures in which the majority of the loads are carried through bending of local components. These bending loads result in local stress concentrations which must be accommodated with additional structural material, resulting higher overall litter weight.
The military has long used the foldable “Talon” litter which includes two spaced foldable longerons supporting a bed and interconnected by foldable bars. Because such a litter is based on a framed structure, it is relatively heavy. Moreover, in testing, the litter fails when subject to high accelerations. Various other litter designs are shown in U.S. Patent Application and Publication Nos. U.S. 2010/0138999; U.S. Pat. Nos. 3,886,606; 6,842,923; 7,043,785; 2,360,371; and 3,555,578 all incorporated herein by this reference.
The present invention relates to an unfoldable litter that forms a lightweight truss structure to support the patient's weight both during nor anal transport and in the event of an accident of the transporting vehicle. Truss structures are more weight efficient than frame structures because the predominant loads are supported in compression and tension rather than in bending. The direction of the loading from weight of the patient allows several of the truss elements can be made of flexible materials allowing for more compact packaging and lighter overall litter weight. The forces required to restrain the patient to the litter are best transferred directly to the restraints that hold the litter to the transport vehicle.
The subject invention preferably utilizes a series of truss structures to support the loads applied by the patient's weight as the patient is transported both by hand and by vehicles. The truss structures translate the applied loads into tension and compression loads in the individual elements. By avoiding global bending loads, the individual components have evenly spread and predictable stresses. This allows the component elements to be smaller, thinner, and made of lighter materials. The reduced component size reduces the packaged size. The combination of reduced size and lighter materials reduces the weight of the litter required to support a given set of patient mass and accelerations.
To further reduce the weight and stowed volume, the subject invention also takes advantage of the observation that in litters, some of the applied loads are always in the same direction. This directionality means that some of the elements are always in tension and never in compression. This, in turn, means that these components can made of flexible, high strength-to-weight materials such as aramids and Ultra-high-molecular-weight polyethylene. The use of these flexible, high strength elements, allow the further reduction of the stowed size and the overall system weight.
In an analysis of the loads experienced by a military litter, the observation is that the highest accelerations that are seen are during aircraft and ground vehicle accidents. During transport by the vehicles, the litters are restrained and the patient is, in turn, restrained by the litter. In current litter technology, the litter-to-vehicle restraint attaches to a different location than the litter-to-patient restraint. This results in substantial loads being transferred through the litter structure and designing for this load transfer adds substantial system mass. In contrast, the subject invention co-locate of the litter-to-vehicle restraint interface and the litter-to-patient restraint interface. This nearly direct load transfer reduces the loads applied to the litter structure reducing the mass of material that must be incorporated into the design.
Featured is a lightweight foldable patient litter comprising spaced compression longerons each foldable at, for example, first, second, and third spaced legs and a bed between the compression longerons. A longitudinal truss structure on each side of the litter includes a compression longeron and a flexible tension member extending from at or proximate one end of the compression longeron to at or proximate the bottom of each leg and then to an opposing end of the compression longeron.
Each longitudinal truss structure may further include a diagonal flexible tension member between the second leg and the first leg and between the second leg and the third leg. The diagonal flexible tension members preferably extend from at or proximate the bottom of the second leg to at or proximate the top of the first and third legs.
The litter may further include one or more lateral truss structures including opposing legs on each side of the litter. One lateral truss structure may include a foldable compression bar pivotably connected to each opposing leg, a flexible tension member extending from at or proximate the bottom of one leg across the litter to at or proximate the bottom of an opposing leg, and diagonal flexible tension members extending from at or proximate the bottom of one leg diagonally across to at or proximate the top of an opposing leg. The lateral truss structure may further include a flexible tension member extending from at or proximate the top of one leg across the litter to at or proximate the top of an opposing leg. In one design, there is a lateral truss structure between each pair of opposing legs.
The litter may further include a foldable compression bar pivotably connected between the spaced compression longerons on each end of the bed and a bed truss structure defining bed truss panels between adjacent foldable compression bars. Each panel may include flexible diagonal tension members.
The litter may further include a handle on each end of the compression longeron extending beyond the bed. Preferably a patient restraint is connected to nodes of a litter truss structure and a litter restraint is connected to the same nodes.
Also featured is a longitudinal truss structure on each side of a litter including a foldable compression longeron, a plurality of legs, and flexible tension members extending from at or proximate one end of a compression longeron to at or proximate the bottom of each leg and then to an opposing end of the longeron and one or more lateral truss structures between opposing legs of the litter.
In one preferred example, a patient litter includes spaced compression longerons each foldable at spaced legs, a bed between the compression longerons, a longitudinal truss structure on each side of the litter each including a longeron, its spaced legs, and one or more flexible tension members connected thereto, one or more lateral truss structures each including opposing legs on each side of the litter and one or more flexible tension members connected thereto, and a bed truss structure including one or more tension members.
The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
Litter 10,
One or more truss structures are configured to support loads applied by the patient's weight. By utilizing a series of truss structures to support the loads applied by the patient's weight as the patient and the litter are transported both by hand and vehicles enables the truss structures to translate the applied loads into tension and compression loads in the individual truss structure elements. By avoiding global bending loads, the individual components have evenly spread and predictable stresses. This allows the component elements to be smaller, thinner, and made of lighter materials. The reduced component size reduces the folded package size. The combination of reduced size and lighter materials reduced the weight of the litter required to support a given set of patient mass and accelerations. The military and other users are is in need of lighter, portable, foldable litters and weight reductions, in particular, are important for man packable litters and litters transported via aircraft.
Shown in
The resulting longitudinal truss structure enables the applied downward loads to be supported by components either entirely in either compression or tension with only the handles having to support a bending load. The outermost compression bars terminate at the handles so the litter can be carried by lifting at both ends or dragging by lifting at one end.
In sharp contrast, the litter of U.S. Pat. No. 2,360,371 has elements loaded in bending and the litter shown in U.S. Pat. No. 3,555,578 results in an incomplete truss structure with outer nodes and rail elements still loaded in bending and which thus must therefore be made larger and heavier to prevent deformation. The litter design shown in U.S. Published Application No. 2010/0138999 is based on a frame design and includes nodes which must support bending to prevent deformation.
The foldable litter shown in the examples of the invention preferably also includes a series of second truss structures lying in the lateral axis to support the patient's weight and resist applied torsional and shear loads. The nodes of these truss structures are held apart by a foldable compression bar and the patient is supported by a tensioned bed which is reacted by a lower tension element. The nodes are prevented from shearing by a pair of cross laced diagonal tension elements.
The example of the lateral truss structure shown in
In sharp contrast, the designs of U.S. Pat. Nos. 3,555,578 and 2,360,371 include nodes which have to be made heavier to support bedding loads to prevent deformation. The design of U.S. Patent Publication 2010/0138999 includes cross lace elements which must support bending loads to prevent deformation.
One preferred foldable litter preferably also includes a top or bed truss structure including, as shown in
The longitudinal side trusses are held apart by the lateral trusses and by the outer compression bars at either end. These compression elements react to the tension loads of the bed and the cross legs diagonal elements of the bed complete the truss structure to prevent shear during loading from both hand carrying and vehicle transport operations.
In sharp contrast, U.S. Pat. Nos. 3,555,578 and 2010/0138999 fail to include any diagonal elements and as a consequence the nodes have to be made heavier to support bending loads to prevent deformation. The structure shown in U.S. Pat. No. 2,360,371 fails to disclose a truss structure and the central nodes have to be made heavier to support bending loads to prevent deformation.
In addition to the use of truss structures, the subject invention also reduces structural mass required by transferring the patient's lateral and forward loads directly to the restraints holding the litter to the transport vehicle. The patient restraint shoulder straps preferably connect directly to the truss nodes at one end and the lap belt straps connect directly to nodes at the other end. The lap belt also connects directly to the nodes. Similarly, the ankle belt is anchored to the nodes. In this way, the patient lateral and forward/app accelerations during transportation are transmitted directly to the nodes of the litter truss structure. The tension lines of the litter restraint hold the litter down to a transport vehicle tie down point and also anchor directly to the same litter nodes as or very nearly as the same as the patient restraint harness. This arrangement results in a direct load transfer greatly reducing the structural loads that must be borne directly by the litter and also facilitates the load transfer through the truss structure.
Thus, in one particular example, shoulder strap 60,
The result is unfoldable litter that forms a lightweight truss structure to support a patient's weight during normal transport and in the event of an accident with a transport vehicle.
Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments.
In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended.
Other embodiments will occur to those skilled in the art and are within the following claims.
