Lightweight foldable patient litter

Abstract

A lightweight flexible patient litter includes, in one example, spaced compression longerons each foldable at spaced legs, a bed between the compression longerons, and 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 may each include opposing legs on each side of the litter and one or more flexible tension members connected thereto. A bed truss structure may include one or more tension members.

Claims

1. A lightweight foldable patient litter comprising: spaced compression longerons each foldable at first, second, and third spaced legs; a bed between the compression longerons; and a longitudinal truss structure on each side of the litter including one of the compression longerons and a flexible, foldable tension member extending from at or proximate one end of said compression longeron to at or proximate the bottom of each leg to an opposing end of said compression longeron, the flexible, foldable tension members supporting loads only in tension and not supporting loads in compression or bending.

2. The litter of claim 1 in which each longitudinal truss structure further includes a diagonal flexible tension member between the second leg and the first leg and between the second leg and the third leg.

3. The litter of claim 2 in which the diagonal flexible tension members extend from at or proximate the bottom of the second leg to at or proximate the top of the first and third legs.

4. The litter of claim 1 further including one or more lateral truss structures between the spaced compression longerons and including an opposing pair of said legs.

5. The litter of claim 4 in which the lateral truss structure includes 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.

6. The litter of claim 5 in which the lateral truss structure further includes 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.

7. The litter of claim 4 in which there is a said-lateral truss structure between each opposing pair of said legs.

8. The litter of claim 1 further including a foldable compression bar pivotably connected between the spaced compression longerons on each end of the bed and also including bed truss panels between adjacent foldable compression bars.

9. The litter of claim 8 in which each panel includes flexible diagonal tension members.

10. The litter of claim 1 further including a handle on each end of the compression longeron extending beyond the bed.

11. The litter of claim 1 further including a patient restraint connected to nodes of a litter truss structure.

12. The litter of claim 11 further including a litter restraint connected to the same nodes.

13. A lightweight foldable patient litter comprising: a longitudinal truss structure on each side of the litter including a foldable compression longeron, a plurality of legs, and flexible, foldable tension members extending from at or proximate one end of said compression longeron to at or proximate the bottom of each leg and then to an opposing end of said compression longeron; and one or more lateral truss structures between opposing legs of the litter; the flexible, foldable tension members supporting loads only in tension and not supporting loads in compression or bending.

14. A lightweight flexible patient litter comprising: 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 one of the compression longerons, its spaced legs, and one or more flexible, foldable tension members connected thereto; one or more lateral truss structures between said spaced compression longerons and each including an opposing pair of said legs and one or more flexible, foldable tension members connected thereto; and bed truss panels including one or more tension members, the flexible, foldable tension members supporting loads only in tension and not supporting loads in compression or bending.

15. The litter of claim 14 in which each longitudinal truss structure includes a diagonal flexible tension members.

16. The litter of claim 14 in which said lateral truss structure further includes a foldable compression bar pivotably connected between opposing legs, 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.

17. The litter of claim 16 in which said lateral truss structure further includes 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.

18. The litter of claim 16 further including a foldable compression bar pivotably connected between the spaced compression longerons on each end of the bed.

19. The litter of claim 14 in which each panel includes flexible diagonal tension members.

20. The litter of claim 14 further including a patient restraint connected to nodes of a litter truss structure.

21. The litter of claim 20 further including a litter restraint connected to the same nodes.

22. A lightweight foldable patient litter comprising: spaced compression longerons each foldable at spaced legs; a bed between the compression longerons; truss structures including flexible, foldable tension members supporting loads applied to the bed by a patient; a patient restraint connected to nodes of the a truss structure; and a litter restraint connected to the same nodes; the flexible, foldable tension members supporting loads only in tension and not supporting loads in compression or bending.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) 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:

(2) FIG. 1 is a schematic three dimensional top view of a litter in its deployed state in accordance with an example of the invention;

(3) FIG. 2 is a schematic three dimensional view of the bottom of the litter shown in FIG. 1;

(4) FIG. 3 is another schematic three dimensional view of an example of a litter;

(5) FIG. 4 is a schematic side view of a litter showing the longitudinal truss structure thereof;

(6) FIG. 5 is a schematic cross sectional end view showing a lateral truss structure in accordance with an example of the invention;

(7) FIG. 6 is a schematic top view showing a bed or top truss structures of the litter;

(8) FIG. 7 is a schematic view showing a patient restrained to the litter itself restrained to a vehicle in accordance with examples of the invention; and

(9) FIGS. 8A-8E shown the primary steps associated with deploying a litter in accordance with examples of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(10) 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.

(11) Litter 10, FIGS. 1-2, in one example, includes spaced compression longerons 12a, 12b each foldable at three legs as shown for longeron 12a foldable at legs 14a, 14b, and 14c. The legs may also fold inwardly with respect to their associated longeron. Or, the legs could be rigidly attached to the longeron. Longeron 12b is foldable at legs 16a, 16b, and 16c. Foldable compression bars are pivotably connected across opposing legs. Thus, compression bar 18a is pivotably connected between legs 14a and 16a, foldable compression bar 18b is pivotably connected between legs 14b and 16b, and foldable compression bar 18c is pivotably connected between legs 14c and 16c. Preferably, outer foldable compression bars or struts 20a and 20b are pivotably connected between compression longerons 12a and 12b at each end of bed 22 as shown. Bed 22 may be a mesh style as shown or solid fabric and it is typically affixed to or wrapped around the longerons. Various pivoting and foldable linkages may be used and locking joints may also be used for the longerons, legs, and compression bars which may be made of aluminum tubing, other metal alloys, or composite materials. Handles 25a, 25b, and 27a, and 27b are preferably included and may connect seamlessly to the respective longerons and extend outwardly from the bed for transporting a patient. The handles could also fold and/or telescope with respect to the longerons.

(12) 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.

(13) Shown in FIGS. 1-4 is an exemplary longitudinal truss structure on each side of the litter including a compression longeron 12 and flexible tension members (e.g., Kevlar, straps, belts, or webbing) extending from at or proximate one end of each compression longeron to at or proximate the bottom of each leg and then to an opposing end of the compression longeron. Thus, flexible tension member 30a is fixed to longeron 12a proximate bar 20a and the head of the bed, extends to the bottom of leg 14a (where it is affixed thereto), extends to the bottom of leg 14b (where it is affixed thereto), extends to the bottom of leg 14c (where it is affixed thereto) and then extends to proximate bar 20b and the foot of the bed where it is affixed to longeron 12a. Flexible tension member 30b is similarly constructed for longeron 12b.

(14) Preferably, the nodes L.sub.1-L.sub.8 FIG. 4 of the longitudinal trusses are further connected by diagonal flexible tension members as shown for diagonal flexible tension member 32a extending diagonally from at or proximate the bottom of leg 14b to at or proximate the top of leg 14a and flexible tension member 32b extends diagonally from at or proximate the bottom of leg 14b to at or proximate the top of leg 14c. Flexible diagonal tension members 34a, and 34b, FIG. 3, are similarly connected between leg 16b and legs 16a and 16c on the other side of the litter completing its longitudinal truss structure. These diagonal elements prevent the structure from shearing under load. The flexible tension members cannot support bending or compression loads, and instead only support loads in tension. As such, they enable the litter to be folded and enable a lighter weight litter.

(15) 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.

(16) 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.

(17) 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.

(18) The example of the lateral truss structure shown in FIG. 5 includes opposing legs 14a and 16a, compression bar 18a, and flexible tension member 40 connecting across the litter to nodes at or proximate the bottom of opposing legs 14a and 16a, and diagonal flexible tension members 42a and 42b extending from the bottom nodes to the top nodes of the opposing legs. With three opposing legs, there are thus three lateral truss structures as more clearly shown in FIG. 3. The lateral truss structures may further include the bed and/or laterally extending flexible tension elements 43a, 43b, and 43c, FIGS. 2-3 connected between the top nodes of opposing legs and optionally sewn to the bed.

(19) 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 brace elements which must support bending loads to prevent deformation.

(20) One preferred foldable litter preferably also includes a top or bed truss structure including, as shown in FIG. 6, for each bed truss panel 50a, 50b, 50c, and 50d, a pair of spaced compression bars, a section of each longeron between the spaced compression bars, and flexible diagonal tension members. Accordingly, for bed panel 50a, the top truss structure includes compression bars 20a and 18a, longeron sections 52a and 52b, and flexible diagonal tension members 54a and 54h extending from the top of legs 14a and 16a diagonally across the bed to the intersection between longeron sections 52a, 52b, and bar 20a. Diagonal truss members 54a and 54b may be sewn to the bed. Bed panel 50 has a similar structure. For bed panels 50b and 50c, the diagonal tension members are connected to the longerons and/or the tops of the spaced legs.

(21) 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.

(22) 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.

(23) 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.

(24) Thus, in one particular example, shoulder strap 60, FIG. 7 connects to node L.sub.1 of the top truss structure, lap strap 64 connects to node L.sub.5, and leg strap 68 connects to node L.sub.6. Litter restraint straps 72a, 72b, and 72c, and 72d connect to the same nodes. The same configuration exists on the other side of the litter. The applicable nodes may include buckles, rings, or the like for connection to the patient restraint and litter restraint straps. FIG. 1 shows how diagonal tension members 54 of the top truss structure form loops 69 for connection to the patient restraint and litter restraint straps, lines, or harnesses.

(25) FIG. 8A shows a compact lightweight foldable litter in its packaged configuration. In FIG. 8B, the foldable longerons 12a and 12b are unfolded by pulling the handles away from each other until they reach the limit of travel by tensioning the lower flexible tension members 30a and 30b, FIG. 8C. FIG. 8D the spreader bars 20a and 20b and 18a-18c are unfolded until straight and locked in place tensioning the bed and the bottom tension cross straps 40a and 40b and 40c which may include adjustable buckles as shown. FIG. 8E shows a configuration where sliding tubes such as tubes 70a, 70b, 70c, 70d, and 70e are used to lock the spreader bars to prevent them from folding when the litter is loaded with a patient. Other latch mechanisms, locking mechanisms, and pivoting mechanisms are possible. The Kevlar fabric tension members may be fastened to the aluminum or metal alloy or composite tubular members (the longerons, legs, and spreader bars) using fasteners. The length of several of the various flexible fabric tension members may be adjusted using straps, buckles, and the like.

(26) 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.

(27) 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.

(28) 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.

(29) Other embodiments will occur to those skilled in the art and are within the following claims.