Variable Speed Patient Transfer Apparatus

1 . A patient transfer apparatus comprising:

a frame;

a seat assembly coupled to the frame;

a track assembly supported for pivoting movement relative to the frame, the track assembly including a moveable track and a motor configured to drive the track for traversing stairs in an ascending direction and in a descending direction opposite the ascending direction;

a sensor configured to detect an operating state of the patient transfer apparatus; and

a control system including a controller configured to control the motor and to adjust a track speed of the patient transfer apparatus based on the operating state of the patient transfer apparatus detected with the sensor.

2 . The patient transfer apparatus of claim 1 , wherein the sensor is configured to determine movement of the track assembly between:

a storage position arranged adjacent to the seat assembly to define the operating state as an occupied state, and

a deployed position arranged pivoted away from the seat assembly to define the operating state as a deployed state.

3 . The patient transfer apparatus of claim 2 , wherein the controller is further configured to determine a track angle of the track assembly relative to a vertical axis to define the deployed state.

4 . The patient transfer apparatus of claim 3 , wherein the controller is further configured to at least partially limit the track speed of the track based on the track angle during operation in the deployed state.

5 . The patient transfer apparatus of claim 1 , wherein the control system further includes an operator interface configured to receive an input from an operator indicative of a desired speed of the patient transfer apparatus; and

wherein the controller is further configured to receive the input from the operator interface and operate the motor at the track speed based on the desired speed.

6 . The patient transfer apparatus of claim 5 , wherein the sensor is configured to determine an actual speed of the track; and

wherein the controller is further configured to:

detect slip occurring between the track and the stairs in response to a difference between the desired speed of the track and the actual speed of the track to define the operating state as a slip state, and

operate the motor to decrease or halt slip during operation in the slip state.

7 . The patient transfer apparatus of claim 5 , wherein the track speed of the patient transfer apparatus is further defined as a maximum allowable speed; and

wherein the controller is further configured to operate the motor such that the patient transfer apparatus moves at the maximum allowable speed when the desired speed is greater than the maximum allowable speed, and at the desired speed when the desired speed is less than or equal to the maximum allowable speed.

8 . The patient transfer apparatus of claim 1 , wherein the sensor is configured to detect occupancy of the seat assembly to define the operating state as an occupied state.

9 . The patient transfer apparatus of claim 8 , wherein the controller is configured to control the motor to at least partially limit the track speed of the track to a patient track speed during operation in the occupied state in response to the sensor detecting that the seat assembly is occupied by a patient.

10 . The patient transfer apparatus of claim 9 , wherein the controller is further configured distinguish between the presence of a patient and the presence of an object during operation in the occupied state.

11 . The patient transfer apparatus of claim 10 , wherein the controller is further configured to control the motor to permit the track speed of the track to exceed the patient track speed during operation in the occupied state in response to the sensor detecting that the seat assembly is occupied by an object.

12 . The patient transfer apparatus of claim 11 , wherein the controller is further configured to:

detect an absence of occupancy of the seat assembly to define the operating state as an unoccupied stat, and

control the motor to permit the track speed of the track to exceed the patient track speed during operation in the unoccupied state in response to the sensor detecting that the seat assembly is unoccupied.

13 . The patient transfer apparatus of claim 8 , wherein the controller is further configured to drive the motor to adjust the track speed of the track assembly during operation in the occupied state.

14 . The patient transfer apparatus of claim 8 , further comprising a brake configured to selectively apply a braking force imparted on the track based on movement of the track in the ascending direction or descending direction; and

wherein the controller is further configured to operate the brake to adjust the track speed of the track assembly during operation in the occupied state.

15 . The patient transfer apparatus of claim 8 , wherein the sensor is configured to determine a current of the motor.

16 . The patient transfer apparatus of claim 8 , wherein the sensor is configured to determine a load acting on the seat assembly.

17 . The patient transfer apparatus of claim 1 , wherein the sensor is configured to detect the stairs to define the operating state as a stair traversal state.

18 . The patient transfer apparatus of claim 17 , wherein the sensor is further configured to detect a condition of the stairs during operation in the stair traversal state.

19 . The patient transfer apparatus of claim 18 , wherein the condition of the stairs includes a transition between the stairs and a landing; and

wherein the sensor is configured to measure a distance between the stairs and the landing.

20 . The patient transfer apparatus of claim 19 , wherein the controller is configured to control the motor to at least partially limit the track speed of the track to a landing track speed during operation in the stair traversal state in response to the sensor detecting that the landing is a bottom landing.