Abstract:
The present invention provides a device for safely and conveniently conveying an object on a slope. The safety feature includes a fail-safe one-way brake comprising a ratchet wheel, a pawl and a biasing means. In one embodiment, the device is foldable; in another embodiment, the device is integrated with a suitcase; in yet another embodiment, the device is motorized.

Description:
FIELD OF INVENTION 
     The present invention relates to a device for conveying an object on an uneven slope, in particular a staircase. 
     BACKGROUND 
     There are situations where people need to convey heavy or bulky objects, e.g. suitcases, up or down uneven slopes, such as staircases when no elevator is available. Dragging such heavy objects up or down a flight of stairs can be very difficult. 
     Conventional suitcases usually have wheels on the bottom to ease the movement of the suitcase on a flat surface. However, such configured wheels are not suitable for manoeuvring the suitcases over the edges of staircases. 
     U.S. Pat. No. 6,938,740 discloses a suitcase that has a plurality of rollers mounted on the back panel of the suitcase to assist in pulling the suitcase up a staircase and a handbrake to stop the movement of the suitcase on the stairs by frictionally engaging brake pads with the rollers. However, this disclosed suitcase has certain disadvantages. Firstly, the friction brake is not consistently reliable, due to wear and tear of the brake pads. Secondly, the brake is ineffective when the suitcase is out of the reach of a user. Accidental release of such a suitcase at an upper staircase would endanger the lives of people who happen to be in the way of the suitcase rolling down the staircase. 
     Therefore, there is an imperative need for a device for conveying, objects on uneven slopes conveniently and safely. 
     SUMMARY 
     The present invention provides a device for conveying an object on a surface, which comprises a support having a open chamber facing the surface; and a climbing module housed in the chamber, the module comprising a pair of pulleys operable to rotate about parallel axes; a belt circumscribing the pair of pulleys and operable to turn in cooperation with the pair of pulleys in a first direction or in a second direction opposite to the first direction; a one-way brake for engaging with one of the pulleys and preventing the belt from turning in the first direction but not in the second direction; and a wire having a first end and a second end, the first end of the wire being connected to the one-way brake; wherein a pulling force on the wire disengages the one-way brake so that the belt is operable to turn in either direction and the device can be moved by the belt on the surface. 
     In accordance with one embodiment of the present invention, the one-way brake comprises a ratchet wheel secured on the pulley that is engaged by the one-way brake; a pawl for engaging with the ratchet wheel in a resting position so as to prevent the belt from turning in the first direction; and a biasing means for creating a biasing force to lock the pawl in the resting position so that the one-way brake is engaged; wherein the one-way brake is disengaged only when the pulling force on the wire overcomes the biasing force and moves the pawl away from the resting position. 
     In accordance with another embodiment of the present invention, when the device is operated by a user to convey an object on an uneven slope, such as a staircase, the belt turning in cooperation with the pair of pulleys eases the movement of the object on the slope and the one-way brake is configured to be engaged immediately to stop the device from moving down the slope, once the user accidentally loses the control of the device. 
     The objectives and advantages of the present invention will become apparent from the following detailed description of embodiments thereof in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like elements. 
         FIG. 1  shows a perspective view of a stair climbing device in accordance with one embodiment of the present invention. 
         FIG. 2A  shows a perspective view of the climbing module of the stair climbing device shown in  FIG. 1 ; whilst  FIG. 2B  shows an enlarged cross sectional view of part of the climbing module shown in  FIG. 2A . 
         FIG. 3  shows a stair climbing device in accordance with another embodiment of the present invention, in operation to convey an object on an uneven slope. 
         FIG. 4  shows a perspective view of a stair climbing device in accordance with another embodiment of the present invention. 
         FIG. 5  shows a perspective view of a stair climbing device integrated with a suitcase in accordance with another embodiment of the present invention. 
         FIG. 6  shows a perspective view of a stair climbing device integrated with a suitcase in accordance with another embodiment of the present invention. 
         FIG. 7  shows a perspective view of a motor-driven stair climbing device in accordance with yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be understood more readily by reference to the following detailed description of certain embodiments of the invention. However, it will be understood by those skilled in the relevant art that the present invention may be practised without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. 
       FIG. 1  shows a perspective view of a stair climbing device  100  in accordance with one embodiment of the present invention. The stair climbing device  100  comprises a support  102  for loading and supporting an object (not shown in  FIG. 1 ); a climbing module  104  connected to the support for conveying the object; a handle  140  for steering the device  100  to a desired direction; and a wire  150  for connecting the handle  140  to the climbing module  104 . 
     Still referring to  FIG. 1 , the support  102  comprises a supporting beam  110  that serves as a mounting frame for the climbing module  104 ; and a sledge beam  120  that is positioned in parallel at each of the two sides of the supporting beam  110 . Upper surfaces of the supporting beam  110  and the sledge beams  120  form a flat platform for supporting the object. The supporting beam  110  defines a hollow chamber  112  open at a ground surface for housing the climbing module  104 . 
     In one embodiment of the supporting beam, the supporting beam  110  is U shaped. 
     In one embodiment of the sledge beam, the sledge beam  120  is L shaped. The horizontal leg of each L shaped sledge beam  120  forms part of a planar contact surface between the device  100  and stairs (not shown in  FIG. 1 ). In addition, a plurality of slots  122  are carved on the vertical leg of each L shaped sledge beam  120 . These slots  122  are useful as anchor points for luggage straps, strings, ropes or hooks for fastening the object to the support  102 . 
     In one embodiment of the sledge beam, each sledge beam  120  is coated with a layer of low friction material, such as polytretrafluoro-ethylene (PTFE), on the surface  124  in contact with stairs in order to reduce sliding friction. In another embodiment, the low friction material is high-density polyethylene (HDPE). 
     In yet another embodiment, the low-friction contact surface is provided by attaching a strip of low friction material to the surface  124 . 
     Still referring to  FIG. 1 , the support  102  can be assembled in a collapsible way. Each sledge beam  120  is connected to a side of the supporting beam  110  by two bars  130 . One end of each bar  130  is connected to the supporting beam  110  by a bracket  132  and a pin  134 , such that each bar  130  is pivoted and foldable to a side of the supporting beam  110 . The other end of each bar  130  is connected to the sledge beam  120  by a socket  136 ; this end of the bar  130  is kickable in the socket  136  by a spring loaded locking pin  138 . To disassemble the support  102 , the spring loaded locking pins  138  are partially displaced so that the end of the bars  130  can be dislodged from the sockets  136 . In another embodiment of the support, one end of the bar  130  is pivoted at the sledge beam  120  whilst the other end is connected to the supporting beam  110  by a socket joint. 
     In another embodiment of the support, the bars  130  form members of a scissor arm mechanism. The scissor arm mechanism allows the supporting beam  110  and the sledge beams  120  to be connected in a collapsible manner. In yet other embodiment of the support, the sledge beams  120  are connected to the supporting beam  110  by two-position hinges. 
     In one embodiment of the support, pockets are carved in the supporting beam  110  as well as slots in the sledge beams  120  and the bars  130  to reduce the weight of the stair climbing device  100  for convenient carriage. 
     Still referring to  FIG.1 , the handle  140  comprises a housing  142  for holding a part of the wire  150  within and a release  144  for releasing the wire  150  disposed within the housing  142  so that the length of the wire  150  between the handle  140  and the climbing module  104  can be adjusted in order to cater for individual use. The wire  150  is spring-loaded (not shown in  FIG. 1 ) in the housing  142 . When the release  144  is pressed, the wire  150  will be recoiled. When the release  144  is pressed and a pulling force is exerted on the wire  150 , part of the wire  150  disposed within the housing  142  will be released. 
       FIG. 2A  shows a perspective view of the climbing module  104  of the stair climbing device shown in  FIG. 1  according to one embodiment of the present invention. The climbing module  104  comprises a front pulley  160 , a rear pulley  161 , an endless belt  164  and a one-way brake  170  for blocking the movement of the climbing module  104  in a direction opposite to X direction indicated by the arrow as seen in  FIG. 2A , when the brake is engaged. 
     Still referring to&#39; FIG. 2A , the two pulleys  160 ,  161  are mounted in the supporting beam  110  (not shown in  FIG. 2A ) and operable to rotate about two parallel pivots  162 ,  163 . Part of each pulley  160 ,  161  extends below a lower surface of the supporting beam  110 . The interior surface of the belt  164  circumscribes the two pulleys  160 ,  161 , so that the belt  164  is operable to turn in cooperation with the two freewheeling pulleys  160 ,  161 . The exterior surface of the belt  164  that extends below the lower surface of the supporting beam  110 , together with lower parts of the sledge beams  120  (not shown in  FIG. 2A ), forms a planar contact surface with stairs (not shown in  FIG. 2A ), acting as a traction surface on which the device  100  travels. In addition, a support member  166  is mounted above the lower part of the belt  164  for preventing the belt  164  from bending inward and maintaining the planar contact surface with stairs. 
     In one embodiment of the support member, the support member  166  is L shaped. In another embodiment of the support member, the support member  166  is coated with a layer of low friction material, such as PTFE, on the surface  167  (not shown in  FIG. 2A ) in contact with the belt  164 , in order to reduce sliding friction. In yet another embodiment of the support member, the low friction material for coating the surface  167  is HDPE. 
     In one embodiment of the climbing module  104 , the pulleys  160 ,  161  are timing pulleys; accordingly, the endless belt  164  is a timing belt that matches the timing pulleys  160 ,  161 . In one embodiment of the timing belt  164 , the exterior surface of the belt  164  has a rubberized coating to enhance traction between the belt  164  and the surface in contact. 
       FIG. 2B  illustrates a cross sectional view of part of the climbing module  104  shown in  FIG. 2A . The one-way brake  170  (also shown in  FIG. 2A ) comprises a ratchet wheel  171 , a pawl  172  for engaging with the ratchet wheel in a resting position, and a biasing means  180  for biasing the pawl  172  towards the resting position. The ratchet wheel  171  is mounted co-axially on a side of the front pulley  160  with teeth of the ratchet wheel  171  pointing in the anti-clockwise direction as seen in  FIG. 2B . The pawl  172  is located at one end of a lever  173  rotatable about an axis  174  parallel to the axis  162 . The lever  173  has three arms: a pawl arm  173   a , a stopper arm  173   b  and an actuator aim  173   c . The pawl arm  173   a  terminates with the pawl  172 , which is operable to engage with teeth of the ratchet wheel  171  to prevent anti-clockwise rotation of the front pulley  160  as seen in  FIG. 2B , but allowing clockwise rotation. The engagement of the pawl  172  with the ratchet wheel  171  defines the resting positions for the pawl  172  and the lever  173 . 
     Still referring to  FIG. 2B , one end of the biasing means  180  is located in a recess  182  of the stopper arm  173   b . The other end of the biasing means  180  contiguous with the supporting beam  110  is located in an aperture  184  in a locating plate  186 . When assembled, the aperture  184  is in line with the recess  182  on the stopper arm  173   b , such that the recess  182 , the aperture  184  and the supporting beam  110  keep the biasing means  180  in position. The biasing means  180  creates a torque in the anti-clockwise direction as seen in  FIG. 2  on the lever  173  so that the pawl  172  is urged towards the resting position to engage with teeth of the ratchet wheel  171 . In this way, the one-way brake is engaged by default, wherein the belt  164  can only turn in the clockwise direction and the climbing module  104  can only move in X direction. 
     In one embodiment of the biasing means as shown in  FIG. 2B , the biasing means  180  is a compression spring. In another embodiment, the biasing means  180  is a biasing block, such as a rubber rod. In yet another embodiment, the biasing means  180  is a stack of disc springs. In another further embodiment, the biasing means  180  is a fluid shock-absorber. In yet another embodiment, the biasing means  180  is a tension spring; for example, one end of the tension spring is attached to the stopper arm  173   b  whist the other end is attached to the supporter member  166 . 
     Still referring to  FIG. 2B , the stopper arm  173   b  has an additional threaded hole  190  near the recess  182 . A screw  192  is provided in the threaded hole  190 . The length of the screw  192  extending from the stopper arm  173   b  towards the locating plate  186  is adjustable. Once the screw  192  length is set, the screw  192  is lockable by a lock nut  194 . The screw  192  acts as a stopper when the lever  173  rotates in a clockwise direction as seen in  FIG. 2B , and the biasing means  180  is compressed. 
     Still referring to  FIG. 2B , one end of the wire  150  is attached to the actuator arm  173   c  of the lever  173 . The attachment is formed by threading the wire  150  through a bore  153  through the actuator arm  173   c  and crimping a sleeve  152  that is larger than the bore  153  at one end of the wire  150 . An additional wire guide  154  with another bore  155  is provided on the front end of the supporting beam  110 . The other end of the wire  150 , passed through the bore  155 , is disposed in the housing  142  of the handle  140 . 
     In accordance with another embodiment of the present invention, the wire  150  is connected to the actuator arm  173   c  by means of a threaded hole on the bore through the arm  173   c  and a screw in the threaded hole tightened on the wire against the bore. In yet another embodiment, the wire through the arm  173   c  and additional guide  154  is a bar that is rigid but terminates with an attachment for a wire  150 . 
     Now referring again to  FIG. 2A , when a pulling force, in X direction as seen in  FIG. 2 , is exerted on the wire  150 , it generates a torque on the lever  173  in the clockwise direction. When the torque generated by the pulling force on the lever  173  is greater than the opposing torque generated by the biasing means  180 , the lever  173  will rotate in the clockwise direction, thereby moving the pawl  172  away from the resting position and releasing the ratchet wheel  171 . In this way, the one-way brake is disengaged; wherein the belt  164  is operable to turn in either clockwise or anti-clockwise direction, and the climbing module is movable in either X direction or the opposite direction. 
       FIG. 3  shows a side view of a stair climbing device  100  in accordance with one embodiment of the present invention, in operation by a user  302  to convey an object  304  on a staircase  306 . The object  304  is strapped on the top of the supporter  102 . The user  302  pulls on the handle  140 , moving the pawl  172  away from the resting position and disengaging the one-way brake. The movement direction of the device  100  on the staircase  306  will be determined by the combination effect of the pulling force, the gravity force and the rolling friction force between the belt  164  and stairs  306 . When along the X-axis as seen in  FIG. 3  the pulling force is greater than the gravity force plus the rolling friction force, the belt  164  will turn in the clockwise direction, so that the climbing module  100  will move upstairs. When along the X-axis the pulling force is less than the gravity force minus the rolling friction force, the belt  164  will turn in the anticlockwise direction, so that the climbing module  100  will move downstairs. When the pulling force is removed, the pawl  172  will immediately snap back to the resting position under the torque generated by the biasing means  180  and stop the belt  164  from turning in the anti-clockwise direction, thereby preventing the device  100  from moving downstairs. 
     In one embodiment of the device  100 , the front  160  and rear  161  pulleys are spaced apart such that they span a distance between edges of at least two steps of a typical staircase. 
       FIG. 4  shows a perspective view of a stair climbing device  400  in accordance to another embodiment of the present invention. The stair climbing device  400  comprises two climbing modules  404 . Each climbing module  404  is configured in a similar manner as the climbing module  104  of the earlier embodiment. However, the two climbing modules  404  are positioned in parallel and connected by two bars  430 . Each bar  430  is configured similar to the bar  130  in the earlier embodiment. One end of the bar  430  is pivotable with one climbing module  404  and the other end is detachably connected to the other climbing module  404  by a socket  436  lockable by a spring loaded locking pin  438 . The two wires  450  are housed in a same handle  440  and controlled simultaneously. 
       FIG. 5  shows a perspective view of a stair climbing device  500  integrated with a suitcase  560  in accordance with another embodiment of the present invention. The suitcase  560  has a vertical recess  563  on a rear panel  562 . The supporting beam  510  is directly moulded onto the surface of the recess  563  to which the climbing module  504  is mounted. The climbing module  504  is configured in a similar manner as the climbing module  104  of the earlier embodiment. The handle  540  is detachably coupled to the top panel  564  of the suitcase  560 . 
     In one embodiment of the suitcase  560 , the exterior surface of the rear panel  562  is affixed with a layer of low friction material, such as PTFE. In another embodiment, the low friction material is HDPE. In another embodiment, two beams  520 , one at each side of the climbing module  504 , are fixed to the rear panel  562  for supporting the suitcase and preventing the direct contact between the suitcase and stairs (not shown in  FIG. 5 ). In yet another embodiment, the surface of the beams  520  in contact with stairs is coated with a layer of low friction material. 
       FIG. 6  shows a perspective view of a climbing device  600  integrated with a suitcase  660  in accordance with another embodiment of the present invention. The suitcase  660  comprises two climbing modules  604  that are configured in a similar manner as the climbing modules  104  in earlier embodiment. Each climbing modules  604  is mounted to a supporting beam  610  (not shown in  FIG. 6 ) that is directly moulded on the surface of a vertical recess  663  (not shown in  FIG. 6 ) on a rear panel  662 . Two wires  650 , each connecting to one of the climbing modules  604 , have one end disposed in a same handle  640  to be controlled simultaneously. 
       FIG. 7  shows a perspective view of a motorized stair climbing device  700  in accordance with another embodiment of the present invention. Based on the non-motorized stair climbing device  100  shown in  FIG. 1 , the motorized stair climbing device  700  further comprises a power unit  701 , a motor  703  electronically connected to the power unit  701 , a gearbox  704  driven by the motor  703  for rotating the front pulley  160 , and a controller  705  for controlling speed and rotation direction of the motor  703 . The power unit  701  is manually turned on or off by activating a master switch  702 . When the power unit  701  is turned on, the motor  703  is on a standby status, awaiting signals from the controller  705 . The controller  705  is connected to the lever  173 , responding to a pulling force on the wire  150 . 
     The controller  705  is a Proportional Integral Derivative (PID) controller, comprising a control box, a switch connected to the lever  173 , a control timer, a control circuit and an encoder (not shown in  FIG. 7  but understood) attached to the motor  703 .The control timer records the duration between two neighbouring states of the switch. And the control circuit receives signals from the switch, the timer and the encoder for controlling the motor. The controller  705  implements a speed and direction control on the motor  703  based on the history and rate of the change of switch state sensed by the timer and the encoder. When a pulling force is applied to and maintained on the wire  150 , the lever  173  is pivoted away from the resting position, thereby disengaging the pawl  172  from the ratchet wheel  171 ; the lever  173  also activates the switch to an ON state and the control circuit actuates the motor  703  in a first direction; the motor in turn turns the gearbox  704  and propels the first pulley  160  to rotate in the anti-clockwise direction as seen in  FIG. 7 ; the belt  164  subsequently turns in a direction opposite to the X direction. When a pulling force is exerted on the wire  150 , but momentarily released and quickly exerted again, the timer records a short duration between the changes of switch state from ON to OFF and back to ON again. If the recorded duration is within a pre-determined time period, the control circuit sends an output signal to actuate the motor  703  in a second direction reversed from the first direction, and in turn propels the gearbox  704 , pulley  160  and belt  164  (shown in  FIG. 2A ) in a reverse direction. If the duration recorded is longer than the pre-determined time period, there is no change of the output signal and the control circuit actuates the motor  703  in the first direction. 
     In another embodiment of the controller, the controller  705  is a fuzzy control system. In yet another embodiment of the controller, the controller  705  is an analogue control system. In another further embodiment of the controller, the controller  705  is a digital control system. 
     When the device is in operation to convey an object on an uneven slope, such as a staircase, the X direction denotes the direction upward the uneven slope. 
     While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the invention scope is not so limited. Alternative embodiments of the present invention will become apparent to those having ordinary skill in the art to which the present invention pertains. Such alternate embodiments are considered to be encompassed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is described by the appended claims and is supported by the foregoing description.