(1) Field of the Invention
The invention relates to the design and operation of a lightweight portable turntable for rotating a wheelchair in tight quarters.
(2) Description of Related Art
Conventional wheelchairs or powerchairs, in particular rear wheel drive chairs, are not designed to rotate on a central axis and are difficult to maneuver in tight quarters and cannot rotate or turn on a short axis like modern mid wheel drive powerchairs which can rotate on a short axis. However, the rear wheel drive powerchairs are far more suitable for travel over rough terrain such as in fields or in wooded areas. Situations are encountered wherein the ability to rotate a wheelchair in tight quarters is required in sporting events wherein travel over rough terrain is required to reach a position where short axis rotation is desirable. Examples of such occasions include hunting and fishing trips. To overcome this problem it is desirable to provide a separate turntable for the powerchair at the short axis location.
Wheelchair turntables have been described for various applications. However, safety concerns have not been sufficiently addressed. These concerns become particularly important when the wheelchair is in motion, such as in a car or bus. Moreover, applications for modern, motororized and therefore heavy wheelchairs have also not been sufficiently addressed.
Wess, et. al., in U.S. Pat. No. 6,568,646 describes a circular turntable mounted rotatably on a base. In one embodiment, the turntable is supported by central conical roller bearings assisted by anti-friction pads between turntable and the base. In a second embodiment the turntable is supported by ring bearings formed by multiple plastic spheres disposed in two circular grooves in the base, concentric with the turntable. Wess provides a rod which effectively locks the turntable to the base of the unit, thereby preventing the table from rotating during positioning of the wheelchair or when the table is not occupied.
Lamb, U.S. Pat. No. 4,339,224 describes a circular compartment containing multiple turntables to accommodate wheelchairs in a public transportation vehicle such as a bus. A padded center-post and padded walls are provided as cushioning for the chair and its occupant in the event of a sudden jolt of the vehicle. However, no provisions are made to secure the wheelchair itself, much less the occupant.
Whitfield, U.S. Pat. No. 7,040,248 B1 shows a turntable for holding a wheelchair on a boat or truck. The chair is fastened to the turntable with U bolts and the turntable is stabilized against vehicle movements.
Constantin, U.S. Pat. Nos. 4,690,364 and 4,754,946, teaches a wheelchair supporting platform onto which the wheelchair is securely fastened with bolts. The platform is rotatably mounted onto a base by a shaft which extends through an opening in the base. In operation, the shaft is fitted with a retaining washer which permits rotation but does not permit the shaft to be pulled out of the opening. Thereby the wheelchair can be safely secured in a moving vehicle,
Lanzillotta, et. al., U.S. Pat. No. 4,759,684 teaches, a wheelchair supporting platform which raises the wheelchair in the manner of a barber chair and also permits rotation thereof. The wheelchair is rolled onto the platform but is in no way secured to the platform.
Sheets, U.S. Pat. No. 5,220,116, describes a rotatable shooting platform for a quadriplegic which has front and rear stops against the wheels of a wheelchair to prevent its forward or backward movement. This is particularly important to prevent gun recoil from driving the chair backwards and off the platform. However, these stops, which are permanently fastened to the platform, make it difficult to subsequently move the wheelchair off the platform. In a second embodiment, a reversible electric motor, operated by the hand of the occupant, rotates the turntable.
Battery powered wheelchairs are quite abundant today and are particularly well suited to the quadriplegic. The power supply of the wheelchair can be utilized not only to drive the chair, but also in this invention, to operate the turntable when the chair is engaged thereon. Further, the power supply can also be used to enable safety features, in particular, by switching power and control from the chair to the turntable, only after the chair has been secured to the turntable. Not only does this provide stability in a moving vehicle but also prevents the chair from being accidentally driven while it is latched to the turntable.
More specifically, it becomes an object of this invention to power the turntable with either the wheelchair's power supply or a separate battery. The wheelchair can optionally be driven onto the turntable and into a latch which locks the chair to the platform. The occupant's control can be simultaneously shifted from the chair to the turntable, while also engaging any other safety devices. Disengaging from the turntable and transferring control back to the chair is only allowed when the turntable is in the proper discharge position. All of these operations can be entirely and safely under control of the chair's occupant.
It is another object of this invention to provide a design for a lightweight, high capacity, motorized, and portable wheelchair turntable which can be safely, independently and conveniently operated by wheelchair-bound person.
It is another object of this invention to provide a design for a lightweight, high capacity, motorized, and portable wheelchair turntable wherein electric power is provided by an external battery.
It is another object of this invention to provide a design for a lightweight, high capacity, and portable wheelchair turntable wherein electrical power and control can be automatically transferred from a powerchair to the turntable when the powerchair engages the turntable and is returned to the powerchair when the occupant disengages the turntable.
It is yet another object of this invention to provide a design for a lightweight, high capacity wheelchair turntable which can be mounted, engaged, operated, and dismounted, with ease and confidence, entirely under the control of a wheelchair-bound person.
These objects are accomplished by a turntable consisting of a stationary bottom plate and a rotatable top plate supported by a central conical bearing assembly and a large diameter circular bearing. Rotation of the top plate is accomplished by an electric motor/gearbox assembly fastened onto the top plate which drives a small sprocket residing between the two plates. The small sprocket drives a chain which also engages a large sprocket, said large sprocket being fastened securely to the lower plate.
Electric power can be supplied to the motor by a battery which also powers the wheelchair. The powerchair is driven onto the rotatable platform over a short ramp which can be retracted after the chair passes over it. The chair may then mount a fifth-wheel hitch assembly where a hitching pin anchors the chair to the turntable, and can also switch electrical power from the chair's electric motor to the motor on the turntable. This now secures the chair and prevents any accidental motion thereof. This is particularly important if the platform is used in a moving vehicle or a boat. In addition, the occupant's control of the motion of the chair is now switched over to control of the table rotation. Operational control, for example by a chin controller or other joystick type control 55, is also transferred to the turntable. Return of power and control to the wheelchair is optionally accomplished by ejecting the hitching pin with a solenoid attached beneath the hitch assembly.
Alternately, the turntable may be provided with its own battery mounted thereon. In this case, only the wheelchair's control is transferred to the turntable when the turntable is in service. This can be done either by a hard wire connection 53, made at the time that the chair becomes latched to the turntable, or, by utilizing a joystick or chin control 55 which transmits a radio signal (not shown) to a receiver on the turntable which, in turn, operates the table.
In the accompanying drawings forming a material part of this description, there is shown:
A preferred embodiment of this invention is illustrated in
The thrust bearing has a weight capacity of about 850-1000 pounds and is only about ¾ inches in height. The large bearing, almost the size of the platform width, works best in terms of weight support. The total platform height, including the upper and lower plates is then only about 1½ inches.
A bearing assembly 10 forming the hub of the rotatable upper plate 3 comprises a pair of conical roller bearings 11a and 11b. The outer race member 12 is common to both bearings 11a and 11b which is welded to mounting plate 13 which in turn is bolted to upper plate 3 by bolts 14. The conical roller bearings 11a and 11b are adjustably secured within the outer race member 12 by the central bolt 15. A protective cover 17 is provided to protect the bearing assembly from debris. The edges of cover 17 may be curved downward to further shield the bearings. Elevation block 16 aligns the bearings 11a and 11b with the upper plate 3 and provides not only spacing but also additional robustness to the bearing assembly 10.
The upper plate 3 is rotated by a reversible dc electric motor 18 which can be under the control of the wheelchair's occupant. Preferably, this is a 12-volt, 30-amp brush motor with gear drive and a 54:1 ratio. The motor 18 rotates a drive sprocket 22 through a gearbox 19 and shaft 20 through an opening 21 in the upper plate 3 (See also
It has been determined that with a large/small sprocket diameter ratio of 9.33 (using, as an example, a large sprocket size of about 14″ and small sprocket of about 1.5″), driven by a 12 Volt motor provides a comfortable rotation speed of the platform. A 24 Volt battery/power supply was found to rotate the table too quickly. Smoothness of rotation is achieved using, for example, a #35 chain and a large sprocket having 114 teeth or thereabout.
Referring now to
An optional small fifth-wheel coupling receiver 34 is shown just ahead of the right wheelchair tire stop 31. This type of coupling allows a reasonable amount of error in the alignment of a wheelchair mounted hitch pin and the receiver on the turntable.
In a second embodiment of this invention, the turntable is identical to the one described in the first embodiment except that it is powered by its own battery or other power supply. The turntable can then accommodate manual wheelchairs as well as powerchairs. Another advantage is that an ohmic power connector from the chair to the turntable is unnecessary. However, chin or other joystick control can still be transferred from the chair to the turntable at the moment the chair is latched thereto. This effectively disables the chair's battery preventing accidental movement of the chair while it is latched to the turntable.
Positioning the battery or power supply is arbitrary and it may be mounted next to the motor 18.
The present invention provide a design for a lightweight, high capacity, and portable wheelchair turntable wherein electrical power and control can be automatically transferred from a powerchair to the turntable when the powerchair engages the turntable and is returned to the powerchair when the occupant disengages the turntable. The rotatable platform of the invention can be mounted, engaged, operated, and dismounted, with ease and confidence, entirely under the control of a wheelchair-bound person. An important application is for a disabled person to use the turntable at a computer workstation. Another important application is for use in outdoor sporting activities such as hunting and fishing trips. Many other applications will be apparent to those skilled in the art and to users of the rotatable platform.
While the embodiment described supra includes only essential features of the turntable which are directed at functionality, there are additional features which may be incorporated on the platform which would make the turntable safer and more user friendly to the occupant.
While this invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.
This application is a Continuation-in-Part application of U.S. Ser. No. 12/322,152, filed on Jan. 29, 2009 now abandoned, which is herein incorporated by reference in its entirety.
Number | Name | Date | Kind |
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4339224 | Lamb | Jul 1982 | A |
4555990 | Egawa | Dec 1985 | A |
4690364 | Constantin | Sep 1987 | A |
4754946 | Constantin | Jul 1988 | A |
4759684 | Lanzillotta et al. | Jul 1988 | A |
4934843 | Nakanishi | Jun 1990 | A |
4966362 | Ramaekers | Oct 1990 | A |
5220116 | Sheets | Jun 1993 | A |
5261779 | Goodrich | Nov 1993 | A |
5344265 | Ullman et al. | Sep 1994 | A |
5391030 | Lee | Feb 1995 | A |
5794908 | East et al. | Aug 1998 | A |
5884929 | Kincaid | Mar 1999 | A |
6343908 | Oudsten et al. | Feb 2002 | B1 |
6568646 | Wess et al. | May 2003 | B2 |
7040248 | Whitfield | May 2006 | B1 |
20040000440 | Sawyer | Jan 2004 | A1 |
Number | Date | Country | |
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20110127402 A1 | Jun 2011 | US |
Number | Date | Country | |
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Parent | 12322152 | Jan 2009 | US |
Child | 12931525 | US |