The present invention relates to a mechanical bathtub lift seat apparatus for assisting persons of limited mobility, such as the elderly or disabled, transfer into or out of a typical bathtub.
 Persons having permanently limited mobility or strength to due to age or disability may have difficulty performing certain typical daily tasks. Entry to or exit from a bathtub is an example of such a task, as it requires transition between a standing position outside the tub and a seated position upon a very low surface within the tub, including climbing over the side wall.
 As a result, there are a number of existing products aimed at assisting a user enter and exit the tub by easing the aforementioned transition. These products include inflatable chairs positioned within a bathtub for lowering and raising the user to and from the bottom of the tub in a constantly seated position. Other seat assemblies can be positioned within a tub for the same purpose, but are driven by water actuated cylinders or electric motors. Some of these assemblies feature rotating seats so that the user can initially sit with his/her legs outside the tub and then rotate their legs over the tub wall before being lowered, eliminating the step of unassisted entry to the tub altogether. Other devices, typically driven by electric motors, are capable of actually transferring the user from a seated position entirely outside the walls of the tub to a seated position within. One lowering system involves a band spanning from a wall-mounted dispenser on one side of a tub to the wall of the tub opposite the dispenser. An electric motor within the dispenser slowly dispenses more length of the band in order to lower a user seated on the band into the tub. Once bathing is completed, the motor is run in an opposite direction to retract the band into the dispenser, thereby lifting the user back up to the top of the tub.
 The primary problem associated with the existing bathtub lift devices is the high cost involved. The need for components such as air compressors, seals and adaptors for water driven devices, electric motors and control systems, coupled with possible installation costs, keeps many of these products financially out of reach for many of those in need of the assistance that would be provided. Many elderly or disabled persons live on limited income and cannot justify the high cost of the existing bathtub lift systems despite the comfort and safety levels they offer. As a result, there is a need for a bathtub lift apparatus that can be produced and sold at a reasonable cost.
 According to one aspect of the present invention there is provided a bathtub lift apparatus for assisting a person into and out of a bathtub comprising:
 a base frame for being received in the tub, the base frame including a track supported on the frame having a lower end and an upper end;
 a trolley supported for movement along the track;
 a seat for supporting the person thereon, the seat being supported on the trolley device for movement with the trolley between a lower position at the lower end of the track and an upper position at the upper end of the track;
 a rotatable drive member supported for rotation on the frame;
 an elongate driven member engaged about the drive member and connected to the trolley for displacement of said trolley as the drive member is rotated; and
 a driver device for rotating the drive member.
 Preferably the base frame comprises two laterally spaced parallel walls, wherein the drive member and elongate driven member are located between said walls.
 Preferably the track comprises two laterally spaced track members, each having an upper and lower surface defining an elongate channel therebetween for receiving the trolley.
 Each of the upper and lower surfaces of the track members may comprise a rail.
 Alternatively, the upper surface of each track member may comprise a rail while the lower surface of each track member comprises the base frame.
 Preferably there is provided roller members supported on each side of the trolley supported for movement along the track.
 Preferably the roller members are supported in pairs on axles mounted to the trolley.
 Preferably the track is non-linear between the upper and lower ends thereof.
 The seat may be pivotally supported on the trolley for pivotal motion relative thereto.
 In this arrangement, preferably there is provided:
 a pivotal mounting mechanism for pivotally supporting the seat on the trolley for pivotal motion between the lower position where the seat is generally horizontal and the trolley is inclined along the track and a lifting position where the seat and trolley are both inclined along the track and generally parallel to each other; and
 an abutment member mounted on the seat that abuts with the trolley to prevent the seat from pivoting passed the lifting position where the seat and trolley are generally parallel.
 Preferably the elongate driven member is flexible.
 The elongate driven member may be endless.
 Preferably the elongate driven member is guided by idler members supported on the base frame.
 Preferably one of the idler members is floatingly supported on the base frame and biased in order to maintain tension in the elongate driven member.
 Preferably the idler members comprise pulleys.
 Preferably the elongate driven member comprises a chain and the driver member comprises a sprocket for engaging the chain.
 Preferably the driver device comprises a rotational member having a series of handles circumferentially spaced therearound.
 In this arrangement, preferably the handles comprise openings in the rotational member.
 Alternatively, the driver device may comprise a hand crank mechanism for rotating the drive member.
 Preferably the driver device is accessible by the person supported in the seat.
 Preferably there is provided a locking mechanism for selectively preventing motion of the seat relative to the base frame.
 Preferably the locking mechanism is coupled between the driver device and the base frame.
 Preferably the locking mechanism comprises:
 an opening in the driver device;
 a corresponding opening in the base frame;
 a pin for passing through the opening in the driver device into the opening in the frame, thereby blocking motion of said driver device, and hence the driver member, elongate driven member, trolley and seat, relative to said frame.
 Preferably the base frame and the driver device comprise aluminum.
 The present invention can be made and sold at substantially lower costs than existing bathtub lifts as a result of its simple mechanical structure. Assembly is simple and affordable, as the drive system not require any complex, costly or custom components and the base frame is easy to fabricate. The apparatus is hand driven and therefore does not require the use of an external power source, such as an electric motor or air compressor and corresponding control mechanism. Furthermore, the simplicity of the apparatus ensures that any maintenance will be minimal and affordable.
 The driver device is reachable from the seat of the lift and therefore may be used by a bather without outside assistance. The driver device is of substantial size such that the amount of torque needed to lift the bather supported on the seat can be achieved with relatively little force. As a result, the bather does not require a lot of strength to use the apparatus and is therefore less likely to require assistance. Using a material of relatively high strength to weight ratio such as aluminum to construct the frame and driver device, the weight of the apparatus is kept to a minimum so that the lift can be easily lowered into and lifted out of a typical bathtub. This is ideal for the cases where more than one person uses the tub on a regular basis and the lift is not always needed. There is no need for professional installation, which helps keep down the overall cost of the lift apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
 In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:
 FIG. 1 is a side elevational view of the bathtub lift with the seat in the lowered position.
 FIG. 2 is a side elevational view of the bathtub lift with the seat in the raised position.
 FIG. 3 is a rear elevational view of the bathtub lift with the seat in the lowered position.
 FIG. 4 is a rear elevational view of the bathtub lift with the seat in the raised position.
 FIG. 5 is a top plan view of the bathtub lift with the seat in the lowered position.
 FIG. 6 is a top plan view of the bathtub lift with the seat in the raised position.
 FIG. 7 is a cross sectional view of the bathtub lift with the seat in the raised position as taken across line VII-VII of FIG. 6.
 The following description outlines the details of a bathtub lift for assisting persons of limited mobility, such as the elderly or disabled, transfer into or out of a typical bathtub. One embodiment of the present invention is shown from the side in FIGS. 1 and 2. The bathtub lift apparatus 1 features a base frame 10 for supporting the apparatus within the bathtub (not shown), a seat 20 for supporting the bather and a driver device 40 for controlling motion of the seat 20. The lift functions in such a manner as to move the seat 20 between a lower position as seen in FIG. 1 and a raised or upper position as seen in FIG. 2. The seat 20 has a backrest portion 21 and a bottom portion 22 connected by an angled portion 23. The user can sit upon the bottom portion 22 in the raised position from outside the tub, rotate his or her body in order to dispose each leg on an opposite side of the apparatus and then descend gradually to the lowered position within the tub. Once finished bathing, the user can then use the control device 40 to ascend back to the raised position and then rotate his or her legs over the tub wall in order to exit the bathtub.
 The movement of the seat is achieved through rolling motion of a trolley 30 attached to the seat 20. The base frame 10 includes a pair of spaced apart parallel vertical walls 11 each having an upper edge 12 defining generally horizontal lower 17 and upper 18 portions and an inclined portion 16. The walls 11 are connected and spaced apart at the end of the upper portion 16 by a horizontal base member 13 at the bottom of the frame 10 and vertical end wall 15 disposed above the base member as shown in FIGS. 3 and 4. A track assembly 50 is supported on each wall 11. The track includes a rail 51 which is held above the base frame 10 by rail supports 52 that extend generally perpendicular to the upper edge 12 of the walls 11. The rail 51 and supports 52 are connected by bolts 53 in order to form a channel 54 defined by a space between the rail 51 and the upper edge 12 of the wall 11. This channel 54 defines the path along which the trolley 30 can move. The trolley includes wheels 32 disposed on each side of the trolley body 31 for rolling motion within the channel 54. The track extends along the inclined 16 and upper 18 portions of the upper edge 12 so that the seat 12 attached to the rear end of the trolley 30 can move between the lower position above lower portion 17 to the raised position above the inclined portion 16. The inclined portion 16 is curved in order to provide a smooth transition of the trolley 30 to and from the upper 18 and lower 17 portions.
 Components of the drive system for the trolley are disposed between the walls 11 of the base frame 10 and are illustrated in FIG. 7. A chain 82 is positioned around a drive sprocket 45 and guide pulleys 91, 94 and 96 and attached to the trolley 30 at opposite ends. A first end of the chain 82 is attaches to the trolley 31 by means of attachment member 34 bolted to the chain 82 and the trolley body 30 at an end opposite the seat 20. From this first end, the chain extends around the sprocket 45 down to a floating idler pulley 91 which is mounted on a lever 92 for pivotal movement about an axis defined by a shaft 93 supported at each end by a wall 11 of the base frame 10. This arrangement allows movement of the idler pulley 91 in order to retain tension in the chain 82 as the trolley 30 moves along the track 50. The chain extends from the idler 91 over a guide pulley 94 supported between the walls 11 by a shaft 95. The chain further extends from the guide pulley 94 around a third pulley 96 supported on a shaft 97 near the end of the lower portion 17 opposite the inclined portion 16. This pulley 96 reverses the chain direction back toward the drive sprocket 45 for connection to a second trolley attachment member 33 at an end of the trolley 30 nearest the seat 20. Similar to the first attachment member, the second attachment member 33 is bolted to the chain 82 and the trolley body 31. With the seat 20 in the lowered position as shown in FIG. 1, rotation of the sprocket 45 in a clockwise direction drives the chain 82 in a manner that pulls the trolley 30 along the track 50 up the inclined portion 16 to the upper portion 18, moving the seat 20 toward the upper position shown in FIG. 2. The shafts 95 and 97 that support the pulleys 94 and 96 at the lower portion 17 further are connected to a wall 11 of the base frame 10 at either so that they not only support the pulleys, but also keep the walls spaced apart at that end of the apparatus.
 The rotation of the drive sprocket 45 is achieved by means of the control device 40. The control device 40 includes a drive wheel 49 having a series of handles 41 formed by holes circumferentially spaced around the wheel. As seen in FIGS. 3 and 4, the drive wheel is attached to a rotatable member 46 by means of bolts 43. The rotatable member is fixed on the same shaft 45 as the drive sprocket 81. The shaft 45 extends transversely through aligned holes in the vertical walls 11 of the base frame 10 near their upper edges 12 at the upper portion 18. The shaft is free to rotate with respect to the frame 10, but lateral movement along its axis is prevented by the combination of a pin 48 and blocking plate 47 as shown in FIGS. 3-6. The blocking plates 47 are supported on the shaft 45 just outside each vertical wall 11 and the pins 48 pass through openings in the shaft just outside the plates. Lateral movement of the shaft 45 with respect to the frame 10 is prevented by the abutment of either pin 48 with the respective blocking plate 47. Rotation of the drive wheel 40 and attached rotatable member 46 causes the sprocket 81 to turn and drive the chain 82, resulting in motion of the trolley 30 and attached seat 20. The wheel 40 is of sufficient size that the handles 41 are within reaching distance of the user when supported on the seat 20 regardless of the position of the trolley 30 along the track 50. The amount force needed to pull the seated user up the inclined portion 16 is kept reasonably small as the relatively large radius of the driver wheel 49 ensures a proportionally large resultant torque about the axis of the shaft 45.
 The force of gravity on the user when seated in the raised position tends to cause the trolley 30 and attached seat 20 to descend down the inclined portion 16 to the lowered position. As a result, a locking mechanism is provided for selectively securing the trolley 30 in the track 50 at the upper portion 18 of the walls 11 of the base frame 10, thus locking the seat 20 in the raised position above the inclined portion 16. A hole 42 in the driver wheel 49 is positioned in order to align with a corresponding hole 14 in the wall 11 of the base frame 10 on the same side of the lift apparatus 1 as the wheel 49 when the seat 20 is in the raised position. A pin 70 is passed through the aligned holes 42 and 14 in order to prevent motion of the wheel 49 with respect to the base frame 10. Since the wheel 49 is attached to the rotatable member 46 which is mounted on the same shaft 45 as the drive sprocket, rotation of any of these components is prevented by the pin 70. The trolley 30 and seat 20 cannot move with the pin 70 in place as the cogs of the stationary sprocket 81 prevent motion of the chain 82.
 A pivoting mechanism 60 is provided between the trolley 30 and the seat 20 to allow pivotal motion of the seat with respect to the trolley as they move along the track 50. A pair of hinges 63 provides the pivoting action between the seat 20 and trolley 30. Each hinge has flaps 61 and 62 attached to the trolley body 31 and the seat 20 respectively. As shown in FIG. 1, the hinge 63 allows the bottom portion 22 of the seat 20 to take on a nearly horizontal orientation in the lowered position at the lower portion 17 of the wall 11 even though the trolley 30 is at an angled orientation along the inclined portion 16. As the trolley 30 is pulled upward along the inclined portion 16 by the chain 82 the hinge will open further such that the bottom portion 22 of the seat 20 will take on an the same orientation as the trolley 30, in other words parallel to the inclined portion 16. An abutment member 64 is attached to the underside of the bottom portion 22 of the seat 20 in order to prevent the hinge 63 from opening more than 180 degrees. In the raised position shown in FIGS. 2 and 7, the hinge 63 opens under the weight of the seat 20 (and user, if seated thereupon) and moves the abutment member 64 into contact with the trolley body 31. This keeps the bottom portion 22 of the seat in a generally horizontal orientation in which the user can easily get on or off the seat 20 for entering or exiting the tub respectively.
 Due to the handles 41 circumferentially disposed about the drive wheel 49 the lift is operable by either the bather or an assistant. The bather is lowered into the tub from the raised position shown in FIG. 2 by removing the locking pin 70 from the aligned holes 42 and 14 in the drive wheel 49 and wall 11 respectively. The weight of the bather on the seat will tend to move the seat 20 and attached trolley 30 down the inclined portion 16, pulling on the chain 82 and causing counter clockwise rotation of the sprocket 81 and the attached shaft 45. Since the driver wheel 49 is mounted on the same shaft 45 by means of the rotational member 46, the counter clockwise rotation can be resisted by means of the handles 41, thereby controlling the speed of descent of the bather towards the lowered position shown in FIG. 1. In order to exit the tub, the seat 20 is moved upward along the inclined portion 16 from the lowered position by rotating the driver wheel 49 clockwise by means of the handles 41. Once the seat 20 has reached the raised position, the holes 41 and 14 of the locking mechanism will be realigned so that the locking pin 70 can be inserted to lock the seat in the raised position while the bather dismounts the lift apparatus.
 The above description outlines a single embodiment of the present invention from which a number of alternate embodiments can be derived by those who are skilled in the art. Alternate styles of frames, seats, trolleys, tracks, drive members, driven members and guide members can be assembled to achieve similar results. One alternate embodiment may employ a rope and winch for lifting and lowering the seat, in which case the rope would only have to extend between the winch and the end of the trolley nearest the upper portion eliminating the need for the guide and tension pulleys. Another alternate embodiment could use a notched belt and pulley combination instead of the chain and sprocket. Other embodiments could feature a trolley arranged to move along a single track member or elongate handles extending outward from the drive wheel transverse to the apparatus. The trolley and seat could also be combined into a single rigid component, eliminating the need for the pivoting mechanism. In this arrangement, the track would not extend to a horizontal upper portion of the frame. The trolley would only move along an inclined section of track and therefore would always be oriented at the same angle with respect to the frame. Without the pivot mechanism, the seat would not move relative to the trolley but would remain fixed at an orientation similar to that of the lowered position of the seat in the preferred embodiment, as shown in FIG. 1. As a result, the bottom portion of the seat would remain in a generally horizontal orientation when moving between the lowered and raised positions.
 Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.