Abstract:
Embodiments of a patient transport platform employing one or more adjustable columns interposed between a base having caster wheels with one or more intermediate large wheels, the adjustable columns accommodating deployment and retraction of the large wheels and elevation and positioning of an articulating patient stretcher chair. In various embodiments, the adjustable columns are in parallel or series connection, or combinations thereof. An articulating base frame assembly with a dampened interconnection between fore and aft sections, having three pairs of wheels for selective implementation in use is also presented.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application hereby claims the benefit of and priority to U.S. Provisional Patent Application 61/632,775, filed Jan. 31, 2012, titled “Patient Transport Platform,” which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The invention herein resides in the art of patient transport and procedure devices. More particularly, the invention relates to such devices that provide for ease of maneuverability and access by the patient, while providing a broad range of procedural utility. Specifically, the invention relates to a patient transport platform that allows for improved mobility by incorporating a set of castered wheels with an interposed pair of deployable large diameter wheels, in conjunction with a seat having a range of adjustable heights and orientations so as to accommodate ease of patient accessibility and care giver utility. Also presented is an articulated base frame assembly with a dampened interconnection between fore and aft sections, having pairs of wheels selectively adapted for implementation in use. 
     BACKGROUND ART 
     There are numerous and various patient transport devices presently known. Most of them employ a platform with a castered wheel at each of four corners thereof, the castered wheels being of small diameter and not given to ease of mobility on anything but the smoothest and flattest of hard surfaces. Typically, patient transport stretcher chairs have also had a lowest seat height in the range of 24 inches, making the same difficult to access by the patient. Moreover, presently existent transport chairs that are adapted for use as treatment or medical procedure stretchers or platforms have been of a complex structure with attendant high costs. 
     SUMMARY OF THE INVENTION 
     In light of the foregoing, it is a first aspect of embodiments of the invention to provide a patient transport platform that is easy to move and steer over a wide range of floor surfaces. 
     Another aspect of the invention is the provision of a patient transport platform in which the seat height may be significantly lowered over presently existing units, providing for ease of entrance and exit by patients. 
     Yet a further aspect of the invention is the provision of a patient transport platform that provides a wide range of positions and orientations to accommodate not only the transport of a patient, but the undertaking of medical procedures, examinations and the like, while still providing for patient comfort. 
     Still a further aspect of the invention is the provision of a patient transport platform having an articulating base for ease of use with a stretcher chair. 
     An additional aspect of the invention is the provision of a patient transport platform having an articulating base of sections interconnected to accommodate free floating and dampened actions therebetween. 
     Another aspect of the invention is the provision of a patient transport platform wherein mobility is achieved by positioning an intermediate pair of large wheels between fore and aft pairs of wheels, either centrally therebetween or toward the aft pair of wheels. 
     The foregoing and other aspects of embodiments of the invention that will become apparent as the detailed description proceeds are achieved by a patient transport device, comprising: a base; castered wheels attached to said base; a support structure mounted to said base for receiving and maintaining a patient; at least two height adjusting mechanisms mounted in series between said base and said support structure; an axle with at least one large wheel supported by springs from the base; a first of the two adjusting mechanisms having an ability to engage the axle of the large wheel for a short distance at the lower end of its stroke; and where said first adjusting mechanism has the ability to vertically float toward the bottom of the stroke when the large diameter wheel is in contact with the floor surface, supporting most of the patient and patient support device weight. 
     Certain other aspects of embodiments of the invention are achieved by a patient transport device, comprising: a bifurcated articulating base having fore and aft portions; a pair of fore caster wheels connected to said fore portion and a pair of aft caster wheels connected to said aft portion; at least one large wheel, larger in diameter than said fore and aft caster wheels, interposed between said pairs of fore and aft caster wheels; and an actuator interposed between said fore and aft portions and effecting articulation therebetween and thereby altering vertical positional relationships among said large wheel and said pairs of fore and aft caster wheels. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       For a complete understanding of the various aspects, structures and techniques of the embodiments of the invention, reference should be made to the following detailed description and accompanying drawings wherein: 
         FIGS. 1A and 1B  are illustrative drawings of a first embodiment of the invention employing series-connected actuators with a double wishbone suspension or four bar parallel linkage for effecting movement of an associated chair and deployment and retraction of a pair of large central wheels; 
         FIGS. 2A and 2B  are illustrative drawings of a second embodiment of the invention employing a pair of series-connected column actuators, but without the double wishbone suspension; 
         FIGS. 3A-3D  are illustrative drawings of a third embodiment of the invention employing a pair of fore and aft column actuators in parallel connection with each other and in series connection with an interposed column actuator, showing various states of actuation thereof; 
         FIG. 4  is a side elevational view of a patient transport platform base according to an embodiment of the invention; 
         FIG. 5  is an elevated perspective view of the patient transport platform base of  FIG. 4 , showing a single column actuator; 
         FIG. 6  is a side perspective view of the patient transport platform base of  FIG. 5 ; 
         FIG. 7  is a side perspective view showing a stretcher chair in chair mode received by the patient transport platform base of  FIG. 5 ; and 
         FIG. 8  is a side perspective view showing a stretcher chair in stretcher mode received by the patient transport platform base of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings and more particularly  FIGS. 1A and 1B , an appreciation can be obtained of the structure and operation of a first embodiment of the invention. This embodiment shows a patient transport platform wherein the height adjustment mechanism is divided into two independently controlled mechanisms operating in series. They include a typical adjustable column actuator plus a modified double wishbone suspension of the column such that it is adjusted by a separate actuator. A protrusion on the outer part of the column can rest on the axle of the large wheel in the lowered position. The double wishbone actuator has a free floating ability at the bottom of its stroke. When this actuator is raised, springs lift the wheel axle above the floor to allow movement and positioning of the patient transport device on its castors. 
     With specific attention to  FIGS. 1A and 1B , it will be appreciated that a patient transport platform according to a first embodiment of the invention is designated generally by the numeral  10 . The device  10  includes a base  12  supporting a stretcher chair  14 . In standard fashion, the stretcher chair  14  includes seat, back and leg rest portions, capable of articulating with respect to each other between a chair orientation and a stretcher orientation. At each of the four corners of the base  12  are caster wheels  16 , typically being of rather small diameter, on the order of 3-5 inches. A pair of large diameter wheels  18  (only one shown in the drawings) is interposed between the pairs of fore and aft caster wheels  16 . The large diameter wheels  18  can have a diameter on the order of 12-20 inches. The large wheels  18  are maintained upon an axle  20 , the axle  20  being biased from the frame by means of a pair of springs  22  interposed between the base  12  and the axle  20 . The springs  22  may be of any suitable type, but are preferably compression springs, urging the wheel  18  away from the floor or support surface. The springs  18  are counteracted by the combined weight of the chair  14  and patient, the added weight of the patient being sufficient to bring the wheels  18  into contact with the floor or supporting surface, against the urging of the springs  22 . 
     A column actuator  24  and suspension actuator  26  are connected in series and interposed between the stretcher chair  14  and base  12 . The actuators  24 ,  26  may be of any suitable type, including hydraulic, pneumatic, electrical or mechanical. Each has an associated piston or column  24   a  and  26   a , as shown in  FIG. 1B . The suspension actuator  26  is interconnected with a double wishbone suspension  28  of the column actuator  24 . A stop  30  is provided on the column actuator  24  and is positioned and adapted for engagement with the axle  20  of the large wheels  18 . 
     In use, the actuator  24  may be used to raise or lower the stretcher chair  14  by means of the associated piston  24   a . The suspension actuator  26  and associated piston  26   a  serve to raise the column actuator  24  and associated double wishbone suspension  28 , as best shown in  FIG. 1B . 
     As presented above, the suspension actuator  26  is preferably characterized by a dead band or free floating range at the bottom of its stroke, accommodating compression of the spring  22  and urging of the wheel  18  into contact with a floor surface by the combined weight of the patient and the stretcher chair  14 . 
     With reference now to  FIGS. 2A and 2B , a second embodiment of a patient transport platform made in accordance with the invention can be seen as designated generally by the numeral  40 . The unit  40  is similar to the unit  10  and, to the degree of such similarity, the same numerals are used to designate similar elements. Again, a base  12  receives a stretcher chair  14  and has at the four corners thereof caster wheels  16  with a pair of larger wheels  18  positioned therebetween. The wheels  18  are rotatable about an axle  20 , which is again biased by a compression spring  22 , or the like. Here, however, there is no wishbone suspension, but rather a pair of adjustable columns  42 ,  44  in series connection. The adjustable column  42  has an associated piston  42   a  that extends therefrom and is operatively connected to the stretcher chair  14 . In like manner, the adjustable column  44  has a piston  44   a  that is affixed to the base  12 . A stop  46  is attached to the adjustable collum  44  and is adapted to rest upon the axle  20 , for operation in a fashion substantially similar to that of the embodiment  10 , but for the replacement of the double wishbone suspension. 
     With reference now to  FIGS. 3A-3B , an appreciation can be attained with regard to a third embodiment of a patient transport platform made in accordance with the invention and designated generally by the numeral  50 . Here, adjustable columns  52 ,  54 ,  56  are operatively interconnected, having respective pistons  52   a ,  54   a , and  56   a . Pistons  52   a  and  56   a  are operatively connected to the stretcher chair  14 , such as the seat portion, while the piston  54   a  is connected to the base  12 . The adjustable columns and associated pistons  52 ,  56  are interconnected in parallel, with that combination being in series interconnection with the adjustable column  54 . The adjustable column  54  has an associated stop  58 , adapted for engagement with the axle  20  of the large wheels  18 , as discussed above. For that purpose, the piston  54   a  of the adjustable column  54  is free floating at the bottom of its stroke, to accommodate movement as against the spring  22  when a patient is received within the chair. 
       FIG. 3A  shows the patient transport platform with the stretcher chair  14  at its maximum height, with the pistons  52   a ,  56   a  at maximum extension from the adjustable column actuators  52 ,  56 . 
       FIG. 3C  shows the piston  52   a  of adjustable column  52  extended slightly, with the pistons  54   a ,  56   a  in their retracted position, allowing the stretcher chair  14  to have a slight backward tilt in the “comfort” position. 
       FIG. 3D  shows a procedural position of the stretcher chair  14 , again with the pistons  54   a ,  56   a  of the adjustable columns  54 ,  56  in their fully retracted position, the piston  52   a  partially extended, and with the back of the stretcher chair  14  being reclined into alignment with the seat portion thereof in a stretcher orientation. 
     With the adjustable column  54   a  being secured to the base  12 , and the columns  52   a ,  56   a  being adjustable as just described, the outer columns  52 ,  56  exert the weight of the patient transport platform  50  directly onto the axle  20  of the large wheels  18 . When the large wheels  18  are in contact with the floor, the spring force of the spring  22  that supported the wheels now exerts a pre-defined force onto the base  12 , maintained by the caster wheels  16 , thus maintaining stability. 
     While the outer portion of the rearward adjustable column  56  is rigidly attached to the outer portion of the center adjustable column  54  to provide stability, the outer portion of the forward adjustable column  52  may be hinged at the lower end of the center column  54  to provide a pivot and thus provide for unequal travel of the two outer adjustable columns  52 ,  56 . This allows for significant seat tilt for the Trendelenburg ( FIG. 3D ) and reverse Trendelenburg positioning. The outer and upper portions of the forward column  52   a  and reverse column  56   a  are attached to the seat bottom to provide for desired vertical positioning even while the large wheel  18  remains in contact with the floor. 
     When the center column is raised, the large wheels  18  lift off of the axle  20 , by separating the stop  58  from the axle, the large wheels  18  lift above the floor in the range of 1″-1.5″ of the free floating travel of the actuator  54 . 
     It is further presented that the friction of the glides within the columns provides a damping action that reduces teetering of the patient transport platform  50  when the center of gravity is over the large wheels  18 . It is contemplated that additional dampening can be added if necessary and the same may be elastomeric, hydraulic, pneumatic, electric or rheomagnetic. 
     For purposes of transporting a patient, whether sitting upright as in a chair or lying horizontal as on a stretcher, the structure and operational features of the platform base are of significance. Accordingly, with reference to  FIGS. 4 and 5 , an appreciation can be obtained with regard to a patient transport platform base made in accordance with the invention and designated generally by the numeral  60 . The platform base  60  includes a base frame  62  having caster wheel assemblies  64  disposed at each of four corners thereof A pair of caster wheels  66   a  is disposed at a fore end of the platform base  60 , while a pair of caster wheels  66   b  is disposed at the aft end of the base. Positioned intermediate the fore and aft pairs of caster wheels  66   a  and  66   b  are a pair of large wheels  68 . In general, the large wheels  68  preferably have a radius that exceeds the diameter of the caster wheels  66 . 
     Extending upwardly from and comprising a portion of the patient transport platform base  60  are one or more column actuators  70 , a pair being shown in  FIG. 4 , with a single column actuator being presented with regard to subsequent embodiments. 
     The base frame  62  is divided into fore and aft portions, such portions being in articulating relationship with each other. As best shown in  FIG. 5 , the fore portion of the platform base  60  comprises a pair of parallel side channels  72  affixedly connected to a cross channel  74  at the fore end of the base  60 , the cross channel  74  having caster wheel assemblies  64  and caster wheels  66   a  maintained on opposite ends thereof 
     Extending downwardly from the side channels  72  and extending therebetween are spaced apart support members  78 , adapted to receive and maintain a base plate  80  thereon. As shown, the base plate  80  receives the column actuators  70  and provides the main support for the structure of a chair assembly to be received thereby. The plate  80  may further receive other mechanisms, either not shown or to be discussed later herein. 
     The aft portion of the base frame  62  comprises a pair of parallel side channel members  82 , running parallel to the pair of side channels  72 . Extending across and connected to the ends of the side channels  82  is a cross channel  84 , running parallel to the cross channel  74 , and maintaining caster wheel assemblies  64  and associated aft caster wheels  66   b  at opposite ends thereof. 
     An axle  86  receives the pair of large wheels  68 , as shown. Preferably, the axle  86  is appropriately mounted to and maintained by the side channels  72  and/or base plate  80 . Further, according to a preferred embodiment of the invention, the pair of side channels  82  is pivotally mounted on the axle  86 . According to one embodiment of the invention, the large wheels  68  are simply freewheeling, with the resultant patient transport mechanism being only manually maneuverable. According to another embodiment of the invention, the wheels  68  may be powered, as by means of a motor-driven transaxle drive mechanism  88 , supported by the base plate  80  and in operative engagement with the wheels  68 . 
     It should now be apparent that the aft portion  82 ,  84  of the base frame  62  is pivotally secured to the fore portion  72 ,  74 ,  76  of the base frame  62 . This pivotal engagement is preferably about the axle  86 , but the desired articulation might be obtained by connecting the side channel  82  to the side channel  72  by pins or the like defining appropriate pivot points. 
     With reference now to  FIGS. 5 and 6 , it can be appreciated that a damper or actuator/damper mechanism is interposed between the fore and aft portions of the articulating base frame  62 . The damper or actuator/damper may be either hydraulic or pneumatic. When articulation of the base frame is desired, and in embodiments where such articulation is achieved manually, the element  90  need merely be a damper. Alternatively, if deployment of the articulating base is to be achieved pneumatically or hydraulically, the element  90  may serve as a combination actuator/damper mechanism. 
     As shown, the mechanism  90  is interposed between a bracket  92  secured to the cross channel  76  of the fore portion of the bifurcated base frame  62  and the cross channel  84  of the aft portion of the bifurcated base frame  62 . Pin connections  96 ,  98  respectively secure opposite ends of the mechanism  70  to the brackets  92 ,  94 . 
     As best shown in  FIG. 6 , the bracket  92  is characterized by a slot  100  that receives the associated pin  96 . This slotting provides a free-floating effect for the aft wheels  66   b , when the large wheels  68  are in contact with the floor. The size of the slot  100  determines the nature and extent of the free float of the aft wheels  66   b . According to an embodiment of the invention, the free float of the wheels from the planar surface defined by those wheels, and further controlled by the length of the slot  100 , is on the order of plus or minus 0.5 inch and preferably plus or minus 0.25 inch. According to yet another embodiment of the invention, the free floating occurs in a range of plus or minus 0.125 inch of vertical wheel travel. Following the free floating region of operation, the damper of the mechanism  90  dampens any further relative movement between the large wheels  68  and the aft wheels  66   b.    
     It is further desired, for purposes of ease of handling and patient comfort, that the axle  86  of the large wheels  68  be positioned at or behind (toward the aft end) the center of the base frame  62 . In other words, with the articulating base locked such that the channels  72 ,  82  are aligned, and with the caster wheels  66   a  and  66   b  on the floor, and the large wheels  68  thereabove, the axle of the large wheels  68  is either at the center of the wheel base, or toward the aft portion thereof. 
     With reference now to  FIG. 7 , the numeral  102  shows a stretcher chair  104  mounted upon a patient transport platform base  60 , made in accordance with the invention. Here, the stretcher chair  104  is shown in the chair orientation. Further, the base frame  62  is shown articulated, with the channels  72 ,  82  angled with respect to each other. It will be appreciated that when a patient is seated within the stretcher chair  104 , the center of gravity of the unit is forward of the axle  106  and floor contact is made between the large wheels  68  and the fore caster wheels  66   a . This contact engagement is further encouraged by any motive force that is applied to the push handles  106 , seeking to move the assembly  102  in the fore direction. 
     With reference to  FIG. 8 , the assembly of  FIG. 7  is shown with the stretcher chair  104  maneuvered to the stretcher position. Here, the center of gravity of the assembly is typically between the axle  86  of the large wheels  68  and the aft caster wheels  66   b . Accordingly, with the aft portion of the frame being articulated with respect to the fore portion, the large wheels  68  and the aft caster wheels  66   b  are in contact with the floor, and this contact is further ensured when a motive force is applied to the end of the stretcher as at  108 . 
     According to preferred embodiments of the invention, when the fore and aft portions of the base frame  62  are aligned with each other, as shown in  FIG. 4 , the large wheels  68  are lifted from the floor a distance of approximately 0.5-1.5 inch. Accordingly, on flat surfaces, the assembly may be easily maneuvered and positioned. Moreover, the assembly may accommodate deviations in the floor surface, such as thresholds, ramp transitions, and the like. For transport purposes, with the base frame  62  being articulated, the benefit of maximizing the weight on the large diameter wheels  68  can be attained, whether those wheels are driven or freewheeling, and transport can be achieved with ease and comfort for the patient. The non-contacting pair of caster wheels ( 66   a  or  66   b ) is only off of the plane of the contacting wheels on the order of approximately 0.75-1.5 inch, and preferably 1.0 inch. Accordingly, when a threshold, floor deviation, ramp, or the like is encountered and an intermittent shifting of contact occurs, the free floating nature of the aft caster wheels  66   b  afforded by the slot  100 , followed by the damping effect of the damper or actuator/damper  90 , ensures patient comfort and unit stability. Only a small free float of the aft caster wheel pair  66   b  is experienced before any necessary further travel of the caster wheel pair  66   b  is experienced in a dampened mode. 
     It should now be appreciated with regard to the embodiments of the invention shown in  FIGS. 4-8  that a bifurcated articulating base allows for accommodation of a convertible patient transport device for transporting a patient when the device is either in the chair or stretcher mode. It is preferred that a pair of large wheels  68  is mounted to the base in a region beginning at a midpoint of the base and extending toward the pair of aft caster wheels  66   b . When the articulating base is maneuvered to a first positional relationship, the large wheels are positioned above a plane established by the lowermost surfaces of the pairs of caster wheels, while in a second positional relationship, the pair of large wheels extends partially below the planes when the stretcher chair  104  maintains a patient in the chair mode, the center of gravity of the patient transport device  102  has a center of gravity between the axle of the large wheels  68  and the pair of fore caster wheels  66   a . In similar manner, when a patient is maintained in the stretcher mode, that center of gravity lies between the axle  86  of the large wheels  68  and the pair of aft caster wheels  66   b . This defines whether the fore or aft caster wheels will be in floor contact in combination with the pair of large wheels  68 . 
     The embodiments of the invention of  FIGS. 4-8  further allow the fore and aft portions of the base to articulate with respect to each other when the pair of large wheels  68  is partially below the plane established by the lower outermost surfaces of the pair of caster wheels  66   a  and  66   b . A damper and/or actuator/damper mechanism  100  operatively interconnects the fore and aft portions of the base and has a free float range defined by a slotted connection as at  100 , allowing for undamped movement between the fore and aft section of a limited nature, on the order of 0.125-0.375 inch. Alternatively or additionally, the damper or actuator/damper may have a characteristic dead band or a progressive damping characteristic. Of course, the extent of such free floating is controlled by the length and/or configuration of the slotted connection  100 . This free float range is followed by a dampened range of operation, minimizing teetering when the patient transport device is in motion. 
     The fore and aft portions of the base articulate about the axle  86  of the pair of large wheels  68 , which wheels may be either freewheeling or driven, as by a transaxle  88  or the like. In other words, the concepts of the invention are adaptable to powered or manually driven patient transport devices. 
     Thus it can be seen that the various aspects of the invention have been achieved by the different embodiments presented and described herein. While in accordance with the patent statutes only the best mode and preferred embodiments of the invention have been presented and described in detail, the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention reference should be made to the following claims.