Abstract:
A linear translation thrust system for moving an object from one location to another that includes at least two platforms and pivotally connected members. The distance between one platform and the second is varied by inflating and deflating an inflatable bladder. The linear translation thrust system may also include a conduit for coupling the exhaust system of a vehicle to the interior of the bladder so that the exhaust pressure of the vehicle inflates the bladder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a device for providing linear translation of one platform relative to a second platform. More particularly, the invention relates to a device for the lifting and lowering of people in wheelchairs to allow entry into and egress from a vehicle. 
     2. Description of Related Art 
     Physically disabled individuals using a wheelchair rely on many different types of mechanical devices to perform routine tasks. For example, a powered lift is often required in order to move such an individual to and from the interior of a vehicle. Conventional wheelchair lifts require extensive modifications to a vehicle in order to attach the lift device to the vehicle. Some of these modifications cause normal vehicle entry and exit to be blocked while the wheelchair lift is in use. 
     There is a public need for a low profile and low pressure actuated wheelchair lift that does not require extensive vehicle modifications or block vehicle doors. Ideally a wheelchair lift should have a footprint just larger than that which is required to encompass the footprint created by the wheelchair. Most power devices for actuating a lift mechanism requires the use of high pressure piston driven devices or heavy electrical motors and gear boxes with commensurate heavy articulating structural members. 
     It is an object of this invention to provide a lightweight lift mechanism requiring very low pressures for the actuation and lifting force. 
     It is a further object of the invention to provide a constant translation or lifting force for a given low pressure input fluid. 
     It is still further object of the invention to provide a lift that travels a straight line path between the lift platform and the bottom platform and has a high aspect ratio (greater than 3 to 1) between the stowed height of the device and the deployed height of the device. 
     U.S. Pat. No. 3,843,092 and U.S. Pat. No. 3,730,366, for example, disclose lifting structures that could be used to lift a wheelchair. However, these and other conventional lifting structures have some disadvantages and limitations, namely their large footprint and cost. Most lift mechanisms require high pressure actuators and/or heavy electric motors and gear boxes in order to affect the operation of the lift. The mechanism members are necessarily high strength and heavy in order to withstand these high pressures and associated forces. Thus, the weight of the finished product is also relatively heavy. 
     In light of the foregoing, there is a need in the art for a lightweight, low profile, low pressure actuated improved lift or translation device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a device that substantially obviates one or more limitations of the related art. To achieve these and other advantages, and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention includes a linear translation device having a base, a platform above the base, an intermediate platform between the base and the platform, an inflatable bladder between the base and the platform for lifting the platform as the bladder is pressurized, at least one first hinge member and at least one second hinge member. Another aspect of the invention includes a hinged bracket assembly formed of two members. 
     In an aspect of the invention, the first hinge member has a first end pivotally connected to the base and a second end pivotally connected to the intermediate platform. In addition, the second hinge member has a first end pivotally connected to the platform and a second end pivotally connected to the intermediate platform. 
     In another aspect of the invention, the hinged bracket assembly comprises a first bracket member pivotally connected to the base at one end and pivotally connected to a second bracket member at the other end. The other end of the second bracket member is pivotally connected to the platform. The pivotal connection between the two bracket members is formed along a hinge axis in a plane substantially perpendicular to hinge axes of the pivotal connections of the first and second hinge members. The bracket hinge axis is in the same plane as the intermediate platform. The intermediate platform has two concave cutouts to provide clearance for the first and second bracket members as they fold inward toward each other during deflation of the inflatable bladder. 
     In yet another aspect, the lift device includes a second platform, and a second inflatable bladder for moving the second platform away from the platform during inflation of the second inflatable bladder. In one preferred configuration having brackets and hinged members, vertical motion is imparted to the second platform without substantial translation of the second platform. In another preferred configuration having hinge members, the second platform simultaneously translates and elevates. 
     In still another aspect, the lift device includes a hose for fluid coupling an exhaust system of a vehicle, or similar source of pressurized air, to an interior of the inflatable bladder so that exhaust of the vehicle inflates the bladder. 
     Additional features, advantages, and objectives of the invention will be set forth in the description that follows, and in part, will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and claims herein as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a side view of a first embodiment of the linear translation device in the fully elevated position wherein broken lines show movement of the linear translation device to a lowered position; 
     FIG. 2 is a plan view of an intermediate platform shown in FIG. 1; 
     FIG. 3 is a side view of a second embodiment of the linear translation device including a second platform for simultaneous lifting and translation; 
     FIG. 4 is a side view of a third embodiment of the linear translation device with a second platform for vertical lifting without substantial translation; 
     FIG. 5 is a partial cross-sectional detail view of an inflation valve assembly shown in FIG. 3; 
     FIG. 6 is a plan view of a base and bladder inflating connector for use with the linear translation device; and 
     FIG. 7 is a top view of an exhaust system coupling for the linear translation device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention as illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts. 
     A preferred embodiment of the linear translation device is shown in FIG. 1, and identified generally by reference numeral  10 . The linear translation device  10  includes a base  12  located below and parallel to a platform  14 . An intermediate platform  16  is located between base  12  and platform  14 . As shown in FIG. 2, the intermediate platform  16  has an opening  32  through which an inflatable bladder  18 , shown in FIG. 1, fits. The size and shape of opening  32  may be of any suitable proportions. By way of example only, an oval shape is shown in FIG.  2 . 
     As shown in FIG. 1, the inflatable bladder  18  is located between the base  12  and the platform  14 . Inflatable bladder  18  has any suitable shape, but the preferred shape shown in FIG. 1 is cylindrical with flat ends. As the inflatable bladder  18  is inflated, it pushes platform  14  away from base  12  and passes through opening  32 , shown in FIG.  2 . When the bladder  18  is deflated, it lowers the platform  14  toward the base  12 . Objects that are to be raised or lower, such as a wheelchair, are placed on platform  14 . 
     Intermediate platform  16  is attached to base  12  through first hinge members  20 . While there may be any number of first hinge members  20 , FIG. 1 shows by way of example two first hinge members  20 . First hinge members  20  are pivotally connected to intermediate platform  16  and base  12 . As inflatable bladder  18  is inflated, the pivotal connections allow intermediate platform  16  to travel both vertically and horizontally relative to base  12 . Intermediate platform  16  may have a pair of cutouts  70 , shown in FIG. 2, to facilitate storage of the vertical linear translation device  10  in its deflated state. 
     As shown in FIG. 1, one or more second hinge members  22  have a first end pivotally connected to platform  14  and a second end pivotally connected to intermediate platform  16 . Preferably, two of the second hinge members  22  are provided. Hinges preferably provide the pivotal connections between the first hinge members  20  and the intermediate platform  16  and base  12  and between the second hinge members  22  and the intermediate platform  16  and platform  14 . The first and second hinge members  20  and  22  allow platform  14  to remain parallel to base  12  and intermediate platform  16  during inflation of inflatable bladder  18 . Preferably, first hinge members  20  and second hinge members  22  are shaped in such a way as to allow inflatable bladder  18  to fully inflate without undesired obstruction. 
     In accordance with another aspect of the present invention, lateral movement of platform  14  relative to base  12  is limited by a first bracket member  24  and a second bracket member  30  shown in FIG.  1 . First bracket member  24  is pivotally connected to base  12  and second bracket member  30  is pivotally connected to platform  14 . Hinges pivotally connect first bracket member  24  and second bracket member  30  together, and provide the pivotal connections between first bracket member  24  and base  12  and between second bracket member  30  and platform  14 . The pivotal connection between the first bracket member  24  and second bracket member  30  has a hinge axis  26  in a plane substantially perpendicular to hinge axes  28  of the pivotal connections of first and second hinge members  20  and  22 . In addition, the pivotal connection between the first and second bracket members  24  and  30  is preferably in the same plane as intermediate platform  16 . 
     Preferably, the sum of the length of one of first hinge members  20  and the length of one of the second hinge members  22  connected thereto is greater than a lift distance between base  12  and platform  14  when inflatable bladder  18  is fully inflated. This insures that first hinge member  20  and second hinge member  22  lack colinearity when platform  14  is moved away from base  12  and facilitate the deflation of inflatable bladder  18  by preventing the first hinge member  20  and second hinge member  22  from becoming locked together when the bladder  18  is in an inflated position. 
     FIG. 3 shows a second embodiment of a lift device  10 ′. Lift device  10 ′ is constructed similar to the lift device  10  shown in FIG.  1  and also includes a second platform  34 . Second platform  34  is moved away from platform  14  by a second inflatable bladder  36  located between platform  14  and second platform  34 . While second platform  34  can be coupled to platform  14  by any known means, in the preferred embodiment at least two third hinge members  38  provide the coupling between the platform  14  and second platform  34 . Third hinge members  38  have a first end pivotally connected to platform  14  and a second end pivotally connected to second platform  34 . Hinges preferably provide the pivotal connection of the third hinge member  38 . 
     Second inflatable bladder  36  is constructed similar to inflatable bladder  18  and is inflated via a valve assembly  40  located in platform  14  and providing selective fluid communication between the interiors of the first inflatable bladder  18  and the second inflatable bladder  36 . Valve assembly  40  has a first end  41  exposed to the interior of first inflatable bladder  18  and a second end  43  exposed to the interior of second inflatable bladder  36 . 
     As shown in FIG. 5, the second end  43  of valve assembly  40  includes a valve member  58  connected on one side to spring  44 . Spring  44  places a pre-load on valve member  58  forcing it to rest on a valve seat  62 . Second end  47  of spring  44  pushes against valve body  64 . First end  45  of spring  44  is connected to a support washer  60  located at the first end  41  of valve assembly  40 . Support washer  60  has an opening that allows fluid from the interior of inflatable bladder  18  to act against valve member  58 . Inflation fluid in the lower bladder exerts pressure upon the spring side of valve  58  and spring  44  exerts pressure upon a support washer  60 . When the force created by the inflation fluid pressure in the first inflatable bladder exceeds the pre-load force of spring  44 , valve  58  lifts from valve seat  62  in valve body  64  and thereby allows fluid to pass from first inflatable bladder  18  to second inflatable bladder  36 . During deflation, an exhaust valve  56 , shown in FIG. 7, attached to first inflatable bladder  18  is opened thereby releasing fluid from the interior of bladder  18 . As the fluid is released the internal pressure of inflatable bladder  18  decreases. When the pressure becomes insufficient to overcome the pre-load force of spring  44 , valve member  58  returns to its resting position against valve seat  62 . As shown in FIG. 5, the second end  43  of valve assembly  40  also has at least one, preferably two, exhaust passages  68 . Exhaust passages  68  have flexible diaphragms  66  covering their openings. The flexible diaphragms  66  are attached at one end to the side of the openings facing the first inflatable bladder  18 . In its rest position, the flexible diaphragms  66  cover the openings of exhaust passages  68 . When the pressure in the first inflatable bladder  18  becomes less than the pressure in the second inflatable bladder  36 , the pressure in the second inflatable bladder forces the non-attached end of flexible diaphragms  68  to move away from the openings of exhaust passages  68 . The pressurized fluid in the second bladder  36  then bleeds back through the multiple exhaust passages  68  thereby allowing it to deflate. 
     In accordance with the present invention, second platform  34 , platform  14 , and third hinge members  38  preferably form a parallelogram structure. As shown in FIG. 3, the parallelogram structure produces relative translation between the platform  14  and the second platform  34  in a direction perpendicular to the lift direction of second platform  34  during inflation of second inflatable bladder  36 . Through this arrangement, second platform  34  is capable of moving laterally towards the interior of a vehicle to facilitate transferring a wheelchair to or from second platform  38  and the vehicle. As shown in FIG. 3, at least one side of the second platform  34  has a wedge shaped ramp  42  to facilitate loading and unloading of objects onto second platform  34 . 
     FIG. 4 shows a third embodiment, lift device  10 ″ for vertical lift without substantial lateral translation. Lift device  10 ″ has two main portions, a lower portion similar to linear translation device  10  shown in FIG. 1, and an upper portion including a second intermediate platform  72 . In this embodiment, second inflatable bladder  36  passes through an opening, not shown, in second intermediate platform  72  and moves the second platform  34  away from the platform  14  during inflation of second inflatable bladder  36 . Second inflatable bladder  36  is connected to inflatable bladder  18  through valve assembly  40 . Valve assembly  40  is incorporated into platform  14  in this embodiment and allows for the inflation of second inflatable bladder  36 . 
     As shown in FIG. 4, second intermediate platform  72  is attached to platform  14  through a hinge assembly similar to that connecting the intermediate platform  16  and the base  12  in linear translation device  10  shown in FIG.  1 . As second inflatable bladder  36  is inflated, the pivotal connections allow second intermediate platform  72  to travel both vertically and horizontally relative to platform  14 . Second platform  34  is attached to second intermediate platform  72  by means of a hinge assembly having fourth hinge members  90  similar to that connecting intermediate platform  16  to platform  14  in linear translation device  10  shown in FIG.  1 . Translational motion between second platform  34  and base  12  is avoided by using a bracket assembly having a third bracket member  92  and a fourth bracket member  94  similar to that used to connect base  12  to platform  14  in linear translation device  10  shown in FIG.  1 . As compared to the linear translation device  10  shown in FIG. 1, the linear translation device  10 ″ gives the user the ability to reach greater distances with substantially no translational motion between base  12  and second platform  34 . 
     As shown in FIG. 6, the base  12  preferably has an inflatable bladder connector  50  for placing the inflatable bladder  18  or the inflatable bladders  18  and  36  in fluid communication with a source of fluid. The connector  50  is preferably embedded in base  12  and has a bladder coupling  48  for flow connection to inflatable bladder  18 . Connector  50  also includes a fluid source coupling  46  for providing flow connection to a source of fluid, such as the exhaust source  58 , shown in FIG. 7, of a vehicle or the blower output of a shop vacuum, for inflating inflatable bladder  18  and optional second inflatable bladder  36 . 
     FIG. 7 shows one possible manner by which a vehicle&#39;s exhaust can be used to inflate bladder  18  and optional second inflatable bladder  36 . Bladder inflating hose  60 , shown in FIG. 7, has a first end connected to exhaust valve  56  and a second end connected either directly to inflatable bladder  18 , or to fluid source connector  46 , shown in FIG.  6 . Exhaust valve  56  is connected to an exhaust source  58  and is operated by a switch, such as a Bowden cable  96  shown in FIG. 7, capable of directing the exhaust fluid into inflatable bladder  18  as desired. 
     Those skilled in the art will appreciate that modifications may be made to the structure of the invention without departing from its scope or spirit. In view of the foregoing, it is intended that the present invention cover modifications and variations of the invention provided they fall within the scope of the following claims and their equivalents.