Stretcher having a motorized wheel

P-0001[0001] This application is a continuation of U.S. patent application Ser. No. 10/022,552, filed Dec. 17, 2001, now U.S. Pat. No. ______, which is a continuation of U.S. patent application Ser. No. 09/434,948, filed Nov. 5, 1999, now U.S. Pat. No. 6,330,926, and which claimed the benefit of U.S. Provisional Patent Application Serial No. 60/154,089, filed Sep. 15, 1999, each of the foregoing applications and issued patents being hereby incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates to a stretcher such as a wheeled stretcher for use in a hospital, and particularly to a wheeled stretcher having a wheel that can be deployed to contact a floor along which the stretcher is being pushed. More particularly, the present invention relates to a wheeled stretcher having a motorized wheel.

[0003] It is known to provide hospital stretchers with four casters, one at each corner, that rotate and swivel, as well as a center wheel that can be lowered to engage the floor. See, for example, U.S. patent application Ser. No. 09/150,890, filed on Sep. 10, 1998, entitled “STRETCHER CENTER WHEEL MECHANISM”, for Heimbrock et al., which patent application is assigned to the assignee of the present invention and incorporated herein by reference. Other examples of wheeled stretchers are shown in U.S. Pat. No. 5,806,111 to Heimbrock et al. and U.S. Pat. No. 5,348,326 to Fullenkamp et al., both of which are assigned to the assignee of the present invention, and U.S. Pat. No. 5,083,625 to Bleicher; U.S. Pat. No. 4,164,355 to Eaton et al.; U.S. Pat. No. 3,304,116 to Stryker; and U.S. Pat. No. 2,599,717 to Menzies. The center wheel is typically free to rotate but is constrained from swiveling in order to facilitate turning the stretcher around corners. The center wheel may be yieldably biased downwardly against the floor to permit the center wheel to track differences in the elevation of the floor. The present invention comprises improvements to such wheeled stretchers.

[0004] According to the present invention, a stretcher for transporting a patient along a floor includes a frame, a plurality of casters coupled to the frame, a wheel supported relative to the frame and engaging the floor, and a drive assembly drivingly couplable to the wheel. The drive assembly has a first mode of operation decoupled from the wheel so that the wheel is free to rotate when the stretcher is manually pushed along the floor without hindrance from the drive assembly. The drive assembly has a second mode of operation coupled to the wheel to drive the wheel and propel the stretcher along the floor.

[0005] According to still another aspect of the present invention, a stretcher for transporting a patient along the floor includes a frame, a plurality of casters coupled to the frame, a wheel coupled to the frame and engaging the floor, a push handle coupled to the frame to maneuver the stretcher along the floor, a drive assembly selectively couplable to the wheel and being operable to drive the wheel and propel the stretcher along the floor, and a hand control coupled to a distal end of the push handle to operate the drive assembly.

[0006] In accordance with a further aspect, the drive assembly includes a motor having a rotatable output shaft, a belt coupled to the output shaft and the wheel, and a belt tensioner movable to tension the belt so that the belt transfers rotation from the output shaft to the wheel.

[0007] According to a still further aspect, the belt tensioner includes a bracket, an idler coupled to the bracket, and an actuator coupled to the idler bracket. Illustratively, the actuator has a first orientation in which the idler is spaced apart from or lightly contacting the belt, and a second orientation in which the idler engages the belt to tension the belt to transfer rotation from the drive motor to the wheel.

[0008] In accordance with another embodiment of the drive assembly, the wheel is mounted directly on an output shaft of a drive motor. In accordance with still another embodiment of the drive assembly, the wheel is mounted directly on a rim portion of a rotor of a drive motor.

[0009] In accordance with another aspect, the stretcher further includes a battery supported on the frame and an on/off switch coupled to the drive motor and the actuator. The on/off switch has an “on” position in which the drive motor and the actuator are supplied with electrical power, and an “off” position in which the drive motor and the idler bracket actuator are prevented from receiving electrical power.

[0010] In accordance with still another aspect, the second mode of operation of the drive assembly includes a forward mode in which the drive assembly is configured so that the wheel is driven in a forward direction, and a reverse mode in which the drive assembly is configured so that the wheel is driven in a reverse direction. Illustratively, movement of a control to a forward position configures the drive assembly in the forward mode, and to a reverse position configures the drive assembly in the reverse mode. In one embodiment, the control includes a rotatable switch coupled to a distal end of a push handle, and which is biased to a neutral position between the forward position and the reverse position. In another embodiment, the control includes a push-type switch coupled to a distal end of a push handle to control the speed of the drive motor, and a forward/reverse switch located on the stretcher to control the direction of rotation of the drive motor.

[0011] According to another aspect of the invention, a stretcher for transporting a patient along a floor includes a frame, a plurality of casters coupled to the frame, a first assembly coupled to the frame for rotatably supporting a wheel between a first position spaced apart from the floor and a second position engaging the floor, a selectively engagable clutch configured to selectively couple a drive motor to the wheel when the clutch is engaged. Illustratively, the clutch allows the wheel to rotate freely when the stretcher is manually pushed along the floor without hindrance from the drive motor when the wheel is engaging the floor and the clutch is disengaged. On the other hand, the drive motor drives the wheel to propel the stretcher along the floor when the wheel is engaging the floor and the clutch is engaged.

[0012] Additional features of the present invention will become apparent to those skilled in the art upon a consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

P-0013[0013] The detailed description particularly refers to the accompanying figures in which:

P-0014[0014]FIG. 1 is a perspective view showing a wheeled stretcher incorporating a drive assembly including a floor-engaging wheel for propelling the stretcher along a floor in accordance with the present invention,

P-0015[0015]FIG. 1<i>a </i>is a perspective view of a portion of the stretcher of FIG. 1, showing a rechargeable battery, a recessed battery compartment in a lower frame configured for receiving the battery and a main power switch mounted on the lower frame adjacent to the battery compartment,

P-0016[0016]FIG. 2 is a partial perspective view, with portions broken away, showing a linkage assembly for lifting and lowering the wheel, and a drive assembly drivingly couplable to the wheel for propelling the stretcher along the floor, the linkage assembly having a neutral position (shown in FIGS. 3 and 7) in which the wheel is spaced apart from the floor and a steer position (shown in FIGS. 5 and 8) in which the wheel is engaging the floor, and the drive assembly having a first mode of operation (shown in FIGS. 5 and 8) decoupled from the wheel so that the wheel is free to rotate when the stretcher is manually pushed along the floor without hindrance from the drive assembly and a second mode of operation (shown in FIGS. 9 and 10) coupled to the wheel to drive the wheel to propel the stretcher along the floor,

P-0017[0017]FIG. 3 is a side elevation view showing the linkage and drive assemblies of FIG. 2, the linkage assembly being shown in the neutral position with the wheel spaced apart from the floor, and further showing the drive assembly in the first mode of operation decoupled from the wheel, the drive assembly including a belt coupling a drive motor to the wheel and a belt tensioner to selectively tension the belt, the belt tensioner including a support bracket, an idler pulley (hereinafter idler) coupled to the support bracket, and an actuator having a first orientation (shown in FIGS. 3, 5, <b>7</b> and <b>8</b>) in which the idler is spaced apart from the belt to decouple the drive motor from the wheel, and a second orientation (shown in FIGS. 9 and 10) in which the idler engages the belt to tension the belt to couple the drive motor to the wheel to propel the stretcher along the floor when the wheel is engaging the floor,

P-0018[0018]FIG. 4 is a sectional view taken along line <b>4</b>-<b>4</b> in FIG. 3, and showing the linkage assembly in the neutral position in which the wheel spaced apart from the floor,

P-0019[0019]FIG. 5 is a view similar to FIG. 3, showing the linkage assembly in the steer position with the wheel engaging the floor, and further showing the actuator in the first orientation with the idler spaced apart from the belt to decouple the drive motor from the wheel so that the wheel is free to rotate when the stretcher is manually pushed along the floor without hindrance from the drive assembly,

P-0020[0020]FIG. 6 is a sectional view similar to FIG. 4 taken along line <b>6</b>-<b>6</b> in FIG. 5, and showing the linkage assembly in the steer position in which the wheel engaging the floor,

P-0021[0021]FIG. 7 is a side elevation view corresponding to FIG. 3, showing the linkage assembly in the neutral position with the wheel spaced apart from the floor, and the actuator in the first orientation with the idler spaced apart from the belt to decouple the drive motor from the wheel, and further showing the drive motor mounted on the lower frame, a wheel-mounting bracket supporting the wheel, the belt loosely coupled to the drive motor and the wheel, the idler support bracket carrying the idler pivotally coupled to the wheel-mounting bracket, and the actuator coupled to the idler support bracket,

P-0022[0022]FIG. 8 is a side elevation view corresponding to FIG. 5, showing the linkage assembly in the steer position with the wheel engaging the floor, and the actuator in the first orientation with the idler spaced apart from the belt to decouple the drive motor from the wheel so that the wheel is free to rotate when the stretcher is manually pushed along the floor without hindrance from the drive motor,

P-0023[0023]FIG. 9 is a view similar to FIG. 8, showing the linkage assembly in the steer position with the wheel engaging the floor, and the actuator in the second orientation with the idler engaging the belt to tension the belt to propel the stretcher along the floor,

P-0024[0024]FIG. 10 is a sectional end view taken along line <b>10</b>-<b>10</b> in FIG. 9, showing the linkage assembly in the steer position with the wheel engaging the floor and the actuator in the second orientation to couple the drive motor to the wheel to propel the stretcher along the floor,

P-0025[0025]FIG. 11 is an end elevation view of the stretcher of FIG. 1, showing the head end of a patient support deck mounted on the lower frame, a first push bar locked in an upward push position and having a handle post extending generally horizontally above the patient support deck, a second push bar locked in a down-out-of-the-way position having a handle post below the patient support deck, and a rotary switch coupled to a distal end of the handle post of the first push bar for operating the drive assembly,

P-0026[0026]FIG. 12 is an exploded perspective view of the rotary switch of FIG. 11 coupled to the distal end of the handle post of the first push bar,

P-0027[0027]FIG. 13 is a sectional view of the rotary switch of FIGS. 11 and 12,

P-0028[0028]FIG. 14 is a block diagram, schematically showing the electrical components of the drive assembly,

P-0029[0029]FIG. 15 is an exploded perspective view of an alternative push-type switch assembly configured to be coupled to the distal end of the handle post of the first push bar for operating the drive assembly, the push-type switch assembly including a pressure sensitive switch configured to be positioned inside the handle post and a flexible dome-shaped cap configured to be coupled to an input shaft of the pressure sensitive switch,

P-0030[0030]FIG. 15<i>a </i>is a view showing a forward/reverse switch configured to be coupled to a distal end of the handle post of the second push bar,

P-0031[0031]FIG. 16 is a sectional view of the push-type switch assembly of FIG. 15 coupled to the distal end of the handle post of the first push bar,

P-0032[0032]FIG. 17 is a sectional view similar to FIG. 16, showing the flexible dome-shaped cap of the push-type switch assembly pressed to push the input shaft of the pressure sensitive switch,

P-0033[0033]FIG. 18 is a perspective view of an alternative embodiment of the drive assembly drivingly couplable to a floor-engaging wheel for propelling the stretcher along the floor, and showing the wheel mounted directly on an output shaft of a drive motor coupled to the wheel-mounting bracket,

P-0034[0034]FIG. 19 is a sectional view of the drive motor and the wheel of FIG. 18 through the central axis of the motor output shaft,

P-0035[0035]FIG. 20 is a perspective view of another alternative embodiment of the drive assembly drivingly couplable to a floor-engaging wheel for propelling the stretcher along the floor, showing the wheel mounted directly on a rim portion of a rotor of a drive motor, and further showing a stationary shaft of a stator of the drive motor fixed to the wheel-mounting bracket, and

P-0036[0036]FIG. 21 is a sectional view of the drive motor and the wheel of FIG. 20 through the central axis of the stationary stator shaft.

DETAILED DESCRIPTION OF THE DRAWINGS

P-0037[0037] The present invention will be described in conjunction with a hospital stretcher, but it will be understood that the same may be used in conjunction with any patient support apparatus, such as an ambulatory chair.

P-0038[0038] Referring to FIG. 1, a stretcher <b>20</b> in accordance with the present invention includes a frame <b>22</b>, comprising an upper frame <b>24</b> and a lower frame <b>26</b>, a shroud <b>28</b> covering the lower frame <b>26</b>, a head end <b>30</b>, a foot end <b>32</b>, an elongated first side <b>34</b>, and an elongated second side <b>36</b>. As used in this description, the phrase “head end <b>30</b>” will be used to denote the end of any referred-to object that is positioned to lie nearest the head end <b>30</b> of the stretcher <b>20</b>, and the phrase “foot end <b>32</b>” will be used to denote the end of any referred-to object that is positioned to lie nearest the foot end <b>32</b> of the stretcher <b>20</b>. Likewise, the phrase “first side <b>34</b>” will be used to denote the side of any referred-to object that is positioned to lie nearest the first side <b>34</b> of the stretcher <b>20</b> and the phrase “second side <b>36</b>” will be used to denote the side of any referred-to object that is positioned to lie nearest the second side <b>36</b> of the stretcher <b>20</b>.

P-0039[0039] The upper frame <b>24</b> is movably supported above the lower frame <b>26</b> by a lifting mechanism <b>38</b> for raising, lowering, and tilting the upper frame <b>24</b> relative to the lower frame <b>26</b>. Illustratively, the lifting mechanism <b>38</b> includes head end and foot end hydraulic cylinders <b>40</b> and <b>42</b>, which are covered by flexible rubber boots <b>44</b>. The head end hydraulic cylinder <b>40</b> controls the vertical position of the head end <b>30</b> of the upper frame <b>24</b> relative to the lower frame <b>26</b>, and the foot end hydraulic cylinder <b>42</b> controls the vertical position of the foot end <b>32</b> of the upper frame <b>24</b> relative to the lower frame <b>26</b>.

P-0040[0040] It is well known in the hospital equipment art to use various types of mechanical, electromechanical, hydraulic or pneumatic devices, such as electric drive motors, linear actuators, lead screws, mechanical linkages and cam and follower assemblies, to effect motion. It will be understood that the terms “drive assembly” and “linkage assembly” in the specification and in the claims are used for convenience only, and are intended to cover all types of mechanical, electromechanical, hydraulic and pneumatic mechanisms and combinations thereof, without limiting the scope of the invention.

P-0041[0041] A patient support deck <b>50</b> is carried by the upper frame <b>24</b> and has a head end <b>30</b>, a foot end <b>32</b>, a first elongated side <b>34</b>, and a second elongated side <b>36</b>. A mattress <b>52</b> having an upwardly-facing patient support surface <b>54</b> is supported by the patient support deck <b>50</b>. A pair of collapsible side rails <b>56</b> are mounted to the upper frame <b>24</b> adjacent to the first and second elongated sides <b>34</b>, <b>36</b> of the patient support deck <b>50</b>. An IV pole <b>58</b> for holding solution containers or other objects at a position elevated above the patient support surface <b>54</b> is pivotably attached to the upper frame <b>24</b>, and can be pivoted between a lowered horizontal position alongside the patient support deck <b>50</b> and a generally vertical raised position shown in FIG. 1.

P-0042[0042] Casters <b>60</b> are mounted to the lower frame <b>26</b>, one at each corner, so that the stretcher <b>20</b> can be rolled over a floor <b>62</b> across which a patient is being transported. Several foot pedals <b>70</b> are pivotably coupled to the lower frame <b>26</b> and are coupled to the lifting mechanism <b>38</b> to control the vertical movement of the head end <b>30</b> and the foot end <b>32</b> of the upper frame <b>24</b> relative to the lower frame <b>26</b>. In addition, a brake pedal <b>72</b> is coupled to the lower frame <b>26</b> near the foot end <b>32</b> thereof to control the braking of the casters <b>60</b>. A brake-steer butterfly pedal <b>74</b> is coupled to the lower frame <b>26</b> near the head end <b>30</b> thereof to control both the braking of the casters <b>60</b>, and the release of the braked casters <b>60</b>. Each of the foot pedals <b>70</b>, brake pedal <b>72</b>, and brake-steer pedal <b>74</b> extends outwardly from the lower frame <b>26</b>.

P-0043[0043] As shown in FIG. 11, a first push bar <b>80</b> is pivotally mounted to the head end <b>30</b> of the upper frame <b>24</b> below the patient support deck <b>50</b> adjacent to the first elongated side <b>34</b> of the patient support deck <b>50</b>. Likewise, a second push bar <b>82</b> is pivotally mounted to the head end <b>30</b> of the upper frame <b>24</b> below the patient support deck <b>50</b> adjacent to the second elongated side <b>36</b> of the patient support deck <b>50</b>. Each of the first and second push bars <b>80</b>, <b>82</b> is independently movable between a raised push position shown in FIGS. 1 and 11, and a lowered down-out-of-the-way position shown in FIG. 11. The first and second push bars <b>80</b>, <b>82</b> each include a handle post <b>84</b> that is grasped by the caregiver when the first and second push bars <b>80</b>, <b>82</b> are in the raised push position to manually push the stretcher <b>20</b> over the floor <b>62</b>. When the push bars <b>80</b>, <b>82</b> are in the down-out-of-the-way position, the push bars <b>80</b>, <b>82</b> are below and out of the way of the patient support surface <b>54</b>, thus maximizing the caregiver's access to a patient on the patient support surface <b>54</b>.

P-0044[0044] As previously described, the stretcher <b>20</b> includes the brake pedal <b>72</b> positioned at the foot end <b>32</b> of the stretcher <b>20</b>, and the brake-steer pedal <b>74</b> positioned at the head end <b>30</b> of the stretcher <b>20</b>. A brake-steer shaft <b>88</b> extends longitudinally along the length of the stretcher <b>20</b> on the first side <b>34</b> thereof underneath the shroud <b>28</b>, and is connected to both the brake pedal <b>72</b> at the foot end <b>32</b> and the brake-steer pedal <b>74</b> at the head end <b>30</b>. Movement of either the brake pedal <b>72</b> or the brake-steer pedal <b>74</b> by a caregiver causes the brake-steer shaft <b>88</b> to rotate about a longitudinal pivot axis <b>90</b>. When the brake-steer shaft <b>88</b> is in a neutral position shown in solid lines in FIG. 4, the brake-steer pedal <b>74</b> is generally horizontal as shown in FIG. 1, and the casters <b>60</b> are free to swivel and rotate. From the generally horizontal neutral position, the caregiver can depress the brake pedal <b>72</b> or a braking portion <b>92</b> of the brake-steer pedal <b>74</b> to rotate the brake-steer shaft <b>88</b> in an anticlockwise, braking direction indicated by arrow <b>94</b> in FIG. 4 to a brake position shown in phantom in FIG. 4. In the braking position, the braking portion <b>92</b> of the brake-steer pedal <b>74</b> is angled downwardly toward the first side <b>34</b> of the stretcher <b>20</b>, and a steering portion <b>96</b> of the brake-steer pedal <b>74</b> is angled upwardly. Rotation of the brake-steer shaft <b>88</b> to the brake position moves brake shoes into engagement with the casters <b>60</b> to stop rotation and swiveling movement of the casters <b>60</b>.

P-0045[0045] From the brake position shown in phantom in FIG. 4, the caregiver can depress a steering portion <b>96</b> of the brake-steer pedal <b>74</b> to rotate the brake-steer shaft <b>88</b> in a clockwise direction back to the neutral position shown in solid lines in FIG. 4. When the brake-steer shaft <b>88</b> is in the neutral position, the caregiver can depress the steering portion <b>96</b> of the brake-steer pedal <b>74</b> to rotate the brake-steer shaft <b>88</b> in a clockwise, steering direction indicated by arrow <b>98</b> shown in FIG. 6 to a steer position shown in FIG. 6. In the steer position, the braking portion <b>92</b> of the brake-steer pedal <b>74</b> is angled upwardly, and the steering portion <b>96</b> of the brake-steer pedal <b>74</b> is angled downwardly toward the second side <b>36</b> of the stretcher <b>20</b>.

P-0046[0046] A linkage assembly <b>100</b> is provided for lifting and lowering a wheel <b>110</b>. The linkage assembly <b>100</b> has (i) a neutral position (shown in FIGS. 3 and 7) in which the wheel <b>110</b> is raised above the floor <b>62</b> a first distance, (ii) a brake position (shown in phantom in FIG. 4) in which the wheel <b>110</b> is raised above the floor <b>62</b> a second higher distance, and (iii) steer position (shown in FIGS. 5 and 8-<b>10</b>) in which the wheel <b>110</b> is engaging the floor <b>62</b>. The floor-engaging wheel <b>110</b> serves a dual purpose—(a) it facilitates steering of the stretcher <b>20</b>, and (b) it drives the stretcher <b>20</b> along the floor <b>62</b> in a power drive mode. Referring to FIGS. <b>2</b>-<b>6</b>, the wheel <b>110</b> is mounted on an axle <b>112</b> coupled to the lower frame <b>26</b> by a wheel-mounting bracket <b>114</b>. The wheel-mounting bracket <b>114</b> is, in turn, coupled to the brake-steer shaft <b>88</b>. Rotation of the brake-steer shaft <b>88</b> changes the position of the wheel <b>110</b> relative to the floor <b>62</b>. For example, when the brake-steer pedal <b>74</b> and the brake-steer shaft <b>88</b> are in the neutral position, the wheel-mounting bracket <b>114</b> holds the wheel <b>110</b> above the floor <b>62</b> a first distance (approximately 0.5 inches (1.3 cm)) as shown in FIG. 3.

P-0047[0047] When the brake-steer shaft <b>88</b> rotates in the braking direction <b>94</b> (shown in FIG. 4), the linkage assembly <b>100</b> pivots the wheel-mounting bracket <b>114</b> upwardly to further lift the wheel <b>110</b> above the floor <b>62</b> a second higher distance (approximately 3.5 inches (8.9 cm)) to allow equipment, such as the base of an overbed table (not shown), to be positioned underneath the wheel <b>110</b>. When the brake-steer shaft <b>88</b> rotates in the steering direction <b>98</b> (shown in FIG. 6), the linkage assembly <b>100</b> pivots the wheel-mounting bracket <b>114</b> downwardly to lower the wheel <b>110</b> to engage the floor <b>62</b> as shown in FIGS. 5 and 8-<b>10</b>.

P-0048[0048] The wheel-mounting bracket <b>114</b> includes a first outer fork <b>120</b>, and a second inner fork <b>122</b>. A foot end <b>32</b> of the first fork <b>120</b>, that is the end of the first fork <b>120</b> closer to the foot end <b>32</b> of the stretcher <b>20</b>, is pivotably coupled to the lower frame <b>26</b> for pivoting movement about a first transverse pivot axis <b>124</b>. A head end of the first fork <b>120</b>, that is the end of the first fork <b>120</b> closer to the head end <b>30</b> of the stretcher <b>20</b>, is pivotably coupled to the second fork <b>122</b> for rotation about a second transverse pivot axis <b>126</b>. A head end portion <b>130</b> of the second fork <b>122</b> extends from the second transverse pivot axis <b>126</b> toward the head end <b>30</b> of the stretcher <b>20</b>. The wheel <b>110</b> is coupled to the head end portion <b>130</b> of the second fork <b>122</b> for rotation about an axis of rotation <b>128</b>. A foot end portion <b>132</b> of the second fork <b>122</b> extends from the second transverse pivot axis <b>126</b> toward the foot end <b>32</b> of the stretcher <b>20</b>, and is received by a space formed by two spaced-apart prongs of the first fork <b>120</b>.

P-0049[0049] An end plate <b>134</b> is fixed to the foot end portion <b>132</b> of the second fork <b>122</b>. A vertically oriented spring <b>136</b> connects the end plate <b>134</b> to a frame bracket <b>138</b> mounted to the lower frame <b>26</b>. When the wheel <b>110</b> is in the neutral position (raised approximately 0.5 inches (1.3 cm)), the brake position (raised approximately 3.5 inches (8.9 cm)), and the steer position (engaging the floor <b>62</b>), the spring <b>136</b> yieldably biases the end plate <b>134</b> and the foot end portion <b>132</b> of the second fork <b>122</b> upwardly, so that the head end portion <b>130</b> of the second fork <b>122</b> and the wheel <b>110</b> are yieldably biased downwardly. The end plate <b>134</b> has a pair of transversely extending barbs <b>140</b> shown in FIGS. 3 and 5 that are appended to a lower end of the end plate <b>134</b> and that are positioned to engage the bottom of the first fork <b>120</b> when the first and second forks <b>120</b>, <b>122</b> are in an “in-line” configuration defining a straight bracket as shown in FIG. 3. Thus, the barbs <b>140</b> stop the upward movement of the end plate <b>134</b> at the in-line configuration to limit the downward movement of the head end portion <b>130</b> of the second fork <b>122</b> and the wheel <b>110</b> relative to the first fork <b>120</b> as the spring <b>136</b> biases the end plate <b>134</b> of the second fork <b>122</b> upwardly.

P-0050[0050] When the brake-steer shaft <b>88</b> pivots the wheel-mounting bracket <b>114</b> downwardly to the steer position shown in FIGS. 5 and 8-<b>10</b>, the wheel <b>110</b> is lowered to a position engaging the floor <b>62</b>. Continued downward movement of the wheel-mounting bracket <b>114</b> pivots the second fork <b>122</b> relative to the first fork <b>120</b> about the second transverse pivot axis <b>126</b> in the direction indicated by arrow <b>142</b> shown in FIG. 5, moving the first and second forks <b>120</b>, <b>122</b> into an “angled” configuration as shown in FIG. 5. The end plate <b>134</b> is yieldably biased upwardly by the spring <b>136</b> to yieldably bias the wheel <b>110</b> downwardly against the floor <b>62</b>. Preferably, the downward force urging the wheel <b>110</b> against the floor <b>62</b> should be sufficient to prevent the wheel <b>110</b> from sliding sideways when the stretcher <b>20</b> is turned. A spring force of approximately 40 pounds (about 18 kilograms) has been found to be adequate.

P-0051[0051] As can be seen, the spring <b>136</b> biases the second fork <b>122</b> away from the angled configuration and toward the in-line configuration, so that the wheel <b>110</b> is biased to a position past the plane defined by the bottoms of the casters <b>60</b> when the wheel <b>110</b> is lowered for engaging the floor <b>62</b>. Of course, the floor <b>62</b> limits the downward movement of deployed wheel <b>110</b>. However, if the floor <b>62</b> has a surface that is not planar or that is not coincident with the plane defined by the casters <b>60</b>, the spring <b>136</b> cooperates with the first and second forks <b>120</b>, <b>122</b> to maintain contact between the wheel <b>110</b> and the floor <b>62</b>. Illustratively, the spring <b>136</b> can maintain engagement between the deployed wheel <b>110</b> and the floor <b>62</b> when the floor <b>62</b> beneath the wheel <b>110</b> is spaced approximately 1 inch (2.5 cm) below the plane defined by the casters <b>60</b>. Also, the spring <b>136</b> allows the deployed wheel <b>110</b> to pass over a threshold that is approximately 1 inch (2.5 cm) above the plane defined by the casters <b>60</b> without causing the wheel <b>110</b> to move out of the steer position into the neutral position.

P-0052[0052] The linkage assembly <b>100</b> includes an upper bent-cross bracket <b>144</b> coupled to the frame bracket <b>138</b>, and supporting an upper pivot pin <b>146</b>. Likewise, the linkage assembly <b>100</b> includes a lower bent-cross bracket <b>148</b> coupled to the wheel-mounting bracket <b>114</b>, and supporting a lower pivot pin <b>150</b>. In addition, the linkage assembly <b>100</b> includes (i) a pivot link <b>152</b> fixed to the brake-steer shaft <b>88</b>, (ii) a connecting link <b>154</b> extending from the pivot link <b>152</b> to a common pivot pin <b>156</b>, (iii) a frame link <b>158</b> extending from the common pivot pin <b>156</b> to the upper pivot pin <b>146</b> of the upper bent-cross bracket <b>144</b>, and (iv) a bracket link <b>160</b> extending from the common pivot pin <b>156</b> to the lower pivot pin <b>150</b> of the lower bent-cross bracket <b>148</b>.

P-0053[0053] The frame link <b>158</b> and the bracket link <b>160</b> form a scissors-like arrangement as shown in FIGS. 2, 4 and <b>6</b>. When the caregiver depresses brake pedal <b>72</b> (or the braking portion <b>92</b> of the brake-steer pedal <b>74</b>) and rotates the brake-steer shaft <b>88</b> in the counter-clockwise direction <b>94</b> toward the brake position, the pivot link <b>152</b> pivots away from the wheel-mounting bracket <b>114</b>, pulling the connecting link <b>154</b> and the common pivot pin <b>156</b> toward the brake-steer shaft <b>88</b> in the direction indicated by arrow <b>162</b> shown in FIG. 4. The upper bent-cross bracket <b>144</b> is vertically fixed relative to the lower frame <b>26</b> and the lower bent-cross bracket <b>148</b> is fixed to the wheel-mounting bracket <b>114</b>, which is pivotably mounted to the lower frame <b>26</b> for upward and downward pivoting movement relative to the lower frame <b>26</b>. Movement of the common pivot pin <b>156</b> in the direction <b>162</b> closes the scissors arrangement formed by the frame link <b>158</b> and the bracket link <b>160</b> as shown in phantom in FIG. 4, pulling the bracket link <b>160</b> upwardly. Pulling the bracket link <b>160</b> upwardly pivots the wheel-mounting bracket <b>114</b> in the direction of arrow <b>164</b> shown in FIG. 3, and further lifts the wheel <b>110</b> off of the floor <b>62</b>.

P-0054[0054] When the caregiver depresses the steering portion <b>96</b> of the brake-steer pedal <b>74</b> and rotates the brake-steer shaft <b>88</b> in the clockwise direction <b>98</b> (shown in FIG. 6) toward the steer position, the pivot link <b>152</b> pivots toward the wheel-mounting bracket <b>114</b> pushing the connecting link <b>154</b> and the common pivot pin <b>156</b> away from the brake-steer shaft <b>88</b> in the direction of arrow <b>166</b> shown in FIG. 6. Movement of the common pivot pin <b>156</b> in the direction indicated by arrow <b>166</b> opens the scissors arrangement formed by the frame link <b>158</b> and the bracket link <b>160</b>, and pushes the bracket link <b>160</b> downwardly. Pushing the bracket link <b>160</b> downwardly pivots the wheel-mounting bracket <b>114</b> in the direction of arrow <b>168</b> shown in FIG. 5, thus deploying the wheel <b>110</b> into engagement with the floor <b>62</b>.

P-0055[0055] When the brake-steer shaft <b>88</b> is in the steer position, the pivot link <b>152</b> contacts a frame member <b>170</b> coupled to the lower frame <b>26</b>, stopping the brake-steer shaft <b>88</b> from further rotation in the clockwise direction as shown in FIG. 6. When the pivot link <b>152</b> contacts the frame member <b>170</b>, the common pivot pin <b>156</b> is in an “over-the-center position” away from the brake-steer shaft <b>88</b> and beyond a vertical plane <b>172</b> (shown in FIG. 6) defined by the upper and lower pivot pins <b>146</b> and <b>150</b>, so that the scissors arrangement formed by the frame link <b>158</b> and bracket link <b>160</b> is in a generally fully-opened position. The upward tension of spring <b>136</b> in conjunction with the over-the-center position of the common pivot pin <b>156</b> biases the pivot link <b>152</b> against the frame member <b>170</b> and biases the common pivot pin <b>156</b> away from the brake-steer shaft <b>88</b>, to lock the wheel <b>110</b> and the brake-steer shaft <b>88</b> in the steer position shown in FIGS. 5 and 8-<b>10</b>.

P-0056[0056] Thus, the stretcher <b>20</b> includes the brake pedal <b>72</b> and the brake-steer pedal <b>74</b> connected to the longitudinally extending brake-steer shaft <b>88</b>. Actuation of the brake pedal <b>72</b> or the brake-steer pedal <b>74</b> by the caregiver simultaneously controls the position of wheel <b>110</b> and the braking of casters <b>60</b>. The brake-steer pedal <b>74</b> has a horizontal neutral position where the wheel <b>110</b> is at the first distance above the floor <b>62</b> and the casters <b>60</b> are free to rotate and swivel.

P-0057[0057] From the neutral position, the caregiver can push the brake pedal <b>72</b> or the braking portion <b>92</b> of the brake-steer pedal <b>74</b> down to rotate the brake-steer shaft <b>88</b> by about 30 degrees to the brake position to brake the casters <b>60</b>. In addition, when the brake-steer shaft <b>88</b> rotates to the brake position, the pivot link <b>152</b> pivots away from the wheel-mounting bracket <b>114</b> pulling the connecting link <b>154</b> and the common pivot pin <b>156</b> in the direction <b>162</b> (shown in FIG. 4) and closing the scissors arrangement of the frame link <b>158</b> and the bracket link <b>160</b> to lift the wheel <b>110</b> to the second higher distance above the floor <b>62</b>.

P-0058[0058] The caregiver can also push the steering portion <b>96</b> of the brake-steer pedal <b>74</b> down to rotate the brake-steer shaft <b>88</b> by about 30 degrees past the neutral position to the steer position in which the casters <b>60</b> are free to rotate and swivel. In addition, when the brake-steer shaft <b>88</b> rotates to the steer position, the pivot link <b>152</b> pivots toward the wheel-mounting bracket <b>114</b> pushing the connecting link <b>154</b> and the common pivot pin <b>156</b> in the direction <b>166</b> (shown in FIG. 6) and opening the scissors arrangement formed by the frame link <b>158</b> and the bracket link <b>160</b> to deploy the wheel <b>110</b> to engage floor <b>62</b> with enough pressure to facilitate steering of the stretcher <b>20</b>. In the steer position, the second fork <b>122</b> of the wheel-mounting bracket <b>114</b> pivots relative to the first fork <b>120</b> and relative to the lower frame <b>26</b>. The wheel <b>110</b> is spring-biased into engagement with the floor <b>62</b> with sufficient force to permit the wheel <b>110</b> to track differences in elevation of the floor <b>62</b>. Reference may be made to the above-mentioned U.S. patent application Ser. No. 09/150,890, entitled “STRETCHER CENTER WHEEL MECHANISM”, for further description of the linkage assembly <b>100</b> for lifting and lowering the wheel <b>110</b>.

P-0059[0059] The construction and operation of a first embodiment of a drive assembly <b>200</b> of the present invention will now be described with reference to FIGS. <b>7</b>-<b>10</b>. The drive assembly <b>200</b> includes a variable speed, bidirectional drive motor <b>202</b> having a rotatable output shaft <b>204</b>, and a selectively engagable clutch <b>206</b> to selectively couple the drive motor <b>202</b> to the wheel <b>110</b> when the clutch <b>206</b> is engaged. As previously described, the wheel <b>110</b> has three positions—(i) a neutral position in which the wheel <b>110</b> is raised the first distance above the floor <b>62</b> as shown in FIGS. 3 and 7, (ii) a brake position in which the wheel <b>110</b> is raised the second higher distance above the floor <b>62</b>, and (iii) a steer position in which the wheel <b>110</b> is engaging the floor <b>62</b> as shown in FIGS. 5 and 8-<b>10</b>. When the wheel <b>110</b> is engaging the floor <b>62</b>, the drive assembly <b>200</b> has (a) a first, manual drive mode of operation decoupled from the wheel <b>110</b> (when the clutch is disengaged as shown in FIGS. 5 and 8) so that the wheel <b>110</b> is free to rotate when the stretcher <b>20</b> is manually pushed along the floor <b>62</b> without hindrance from the drive motor <b>202</b>, and (b) a second, power drive mode of operation coupled to the wheel <b>110</b> (when the clutch is engaged as shown in FIGS. 9 and 10) to drive the wheel <b>110</b> to propel the stretcher <b>20</b> along the floor <b>62</b>.

P-0060[0060] The selectively engagable clutch <b>206</b> includes a drive pulley <b>208</b> mounted on the rotatable output shaft <b>204</b> of the drive motor <b>202</b>, a driven pulley <b>210</b> coaxially mounted on the axle <b>112</b> and coupled to the wheel <b>110</b>, a slipbelt <b>212</b> (also referred to herein as belt <b>212</b>) extending loosely between and around the drive pulley <b>208</b> and the driven pulley <b>210</b>, an idler <b>214</b> having a first position (shown in FIGS. 5 and 8) spaced apart from or lightly contacting the belt <b>212</b> and a second position (shown in FIGS. 9 and 10) pressed against the belt <b>212</b> to put tension in the belt <b>212</b>, a support bracket <b>216</b> pivotally mounted to the head end portion <b>130</b> of the wheel-mounting bracket <b>114</b> about a pivot pin <b>218</b>, an actuator <b>220</b> mounted to the lower frame <b>26</b>, and a gas spring <b>222</b> having its ends <b>224</b> and <b>226</b> pivotally coupled to the support bracket <b>216</b> and an output member <b>228</b> threadably engaging a rotatable output shaft <b>230</b> of the actuator <b>220</b>. The support bracket <b>216</b>, the actuator <b>220</b> and the gas spring <b>222</b> are sometimes referred to herein as a second assembly or second linkage assembly.

P-0061[0061] In the specification and claims, the language “idler <b>214</b> is spaced apart from the slipbelt <b>212</b>” or “idler <b>214</b> is lightly contacting the slipbelt <b>212</b>” is used for convenience only to connote that the slipbelt <b>212</b> is not in tension and the drive motor <b>202</b> is decoupled from the wheel <b>110</b> as shown in FIGS. 5 and 8. Thus, the language “idler <b>214</b> is spaced apart from the slipbelt <b>212</b>” or “idler <b>214</b> is lightly contacting the slipbelt <b>212</b>” is to be construed to mean that the drive motor <b>202</b> is decoupled from the wheel <b>110</b>, and not to be construed to limit the scope of the invention.

P-0062[0062] In the manual drive mode, when the wheel <b>110</b> is engaging the floor <b>62</b> and the clutch <b>206</b> is disengaged as shown in FIGS. 5 and 8, the support bracket <b>216</b> has a first orientation in which the idler <b>214</b> is spaced apart from or lightly contacting the belt <b>212</b> so that the wheel <b>110</b> is free to rotate when the stretcher <b>20</b> is manually pushed along the floor <b>62</b> without hindrance from the drive motor <b>202</b>. In the power drive mode, when the wheel <b>110</b> is engaging the floor <b>62</b> and the clutch <b>206</b> is engaged as shown in FIGS. 9 and 10, the support bracket <b>216</b> has a second orientation in which the idler <b>214</b> is pressed against the belt <b>212</b> to transfer rotation from the drive motor <b>202</b> to the wheel <b>110</b> to propel the stretcher <b>20</b> along the floor <b>62</b>.

P-0063[0063] A power source, such as a rechargeable battery <b>242</b>, is inserted into a recessed battery compartment <b>244</b> formed in the lower frame <b>26</b> as shown in FIG. 1 a for supplying power to the drive motor <b>202</b> and the actuator <b>220</b>. The battery compartment <b>244</b> has terminals <b>246</b> for engagement with corresponding terminals <b>248</b> on the rechargeable battery <b>242</b> when the battery <b>242</b> is inserted in the battery compartment <b>244</b>. A main, on/off power switch <b>250</b> is mounted on the lower frame <b>26</b> away from the patient support deck <b>50</b> for connecting and disconnecting the drive motor <b>202</b> and the actuator <b>220</b> to and from the battery <b>242</b>. A limit switch <b>252</b> is mounted on the lower frame <b>26</b> next to the linkage assembly <b>100</b>, as shown in FIGS. 4 and 6, for sensing when the wheel <b>110</b> is lowered for engaging the floor <b>62</b>. A rotary switch assembly <b>254</b> is coupled to a distal end <b>86</b> of the handle post <b>84</b> of the first push bar <b>80</b> as shown in FIGS. 1 and 11 for controlling the speed and direction of the variable speed, bidirectional drive motor <b>202</b>.

P-0064[0064] The stretcher <b>20</b> is in the manual drive mode when the wheel <b>110</b> is engaging the floor <b>62</b>, but the main power switch <b>250</b> on the lower frame <b>26</b> is switched off as shown in FIGS. 5 and 8. In the manual drive mode, the actuator <b>220</b> remains inactivated allowing the belt <b>212</b> to ride loosely over the drive and driven pulleys <b>208</b> and <b>210</b> to permit the wheel <b>110</b> to rotate freely when the stretcher <b>20</b> is manually pushed along the floor <b>62</b> without interference from the drive assembly <b>200</b>.

P-0065[0065] The stretcher <b>20</b> is in the power drive mode when the wheel <b>110</b> is engaging the floor <b>62</b>, and the main power switch <b>250</b> on the lower frame <b>26</b> is turned on as shown in FIGS. 9 and 10. In the power drive mode, the actuator <b>220</b> is activated to press the idler <b>214</b> against the belt <b>212</b> to couple the drive motor <b>202</b> to the wheel <b>110</b> to propel the stretcher <b>20</b> along the floor <b>62</b> in response to the operation of the rotary switch assembly <b>254</b> on the handle post <b>84</b>.

P-0066[0066] A generally vertically oriented spring <b>232</b> (FIGS. 3, 5 and <b>7</b>) coupled between a head end <b>30</b> of the idler support bracket <b>216</b> and the lower frame <b>26</b> helps to fully lift the linkage assembly <b>100</b> off the floor <b>62</b> when in neutral or brake positions. Alternatively, the vertically oriented spring <b>232</b> may be coupled between a head end <b>30</b> of the wheel-mounting bracket <b>114</b> and the lower frame <b>26</b>. Guide rollers (not shown) are provided to prevent the belt <b>212</b> from slipping off the drive and driven pulleys <b>208</b> and <b>210</b>.

P-0067[0067] When the actuator <b>220</b> is activated to press the idler <b>214</b> against the belt <b>212</b>, the gas spring <b>222</b> is compressed as shown in FIGS. 9 and 10 to provide additional downward biasing force between the wheel <b>110</b> and the floor <b>62</b>. Illustratively, the additional downward biasing force exerted by the compressed gas spring <b>222</b> is between seventy five pounds and one hundred pounds.

P-0068[0068]FIG. 14 schematically shows the electrical system <b>240</b> for the drive assembly <b>200</b>. The limit switch <b>252</b> senses when the wheel <b>110</b> is lowered for engaging the floor <b>62</b>, and provides an input signal to a controller <b>256</b>. The controller <b>256</b> activates the actuator <b>220</b> when the main power switch <b>250</b> is turned on and the limit switch <b>252</b> senses that the wheel <b>110</b> is engaging the floor <b>62</b>. When the actuator <b>220</b> is turned on, the output member <b>228</b> of the actuator <b>220</b> is translated in the direction of arrow <b>258</b> (shown in FIG. 8) to cause the support bracket <b>216</b> to pivot clockwise about the pivot pin <b>218</b> to press the idler <b>214</b> against the belt <b>212</b> as shown in FIG. 9 to transfer rotation from the drive motor <b>202</b> to the wheel <b>110</b>. The drive motor <b>202</b> then propels the stretcher <b>20</b> along the floor <b>62</b> in response to the operation of the rotary switch assembly <b>254</b>. The rotary switch assembly <b>254</b> is rotated to a forward position for forward motion of the stretcher <b>20</b> and is rotated to a reverse position for reverse motion of the stretcher <b>20</b>. The speed of the variable speed drive motor <b>202</b> is determined by the extent of rotation of the rotary switch assembly <b>254</b>.

P-0069[0069] The rotary switch assembly <b>254</b> coupled to the distal end <b>86</b> of the handle post <b>84</b> will now be described with reference to FIGS. 12 and 13. FIG. 12 is an exploded perspective view of the rotary switch assembly <b>254</b>, and FIG. 13 is a sectional view of the rotary switch assembly <b>254</b>. The distal end <b>86</b> of the handle post <b>84</b> includes a generally cylindrical hollow tube <b>260</b> defining an axis <b>262</b>. The rotary switch assembly <b>254</b> includes a bidirectional rotary switch <b>264</b> positioned inside the hollow tube <b>260</b> to rotate about the axis <b>262</b>. Control wires <b>266</b> of the rotary switch <b>264</b> are routed through the hollow tube <b>260</b> for connection to the controller <b>256</b>. The rotary switch <b>264</b> includes an input shaft <b>268</b> which is configured to be inserted into a chuck <b>270</b> coupled to an inner end of a control shaft <b>272</b>. A thumb wheel <b>274</b> is coupled to an outer end of the chuck <b>270</b> by a set screw <b>276</b>. The control shaft <b>272</b> is inserted into an outer sleeve <b>278</b> through an outer end thereof. The rotary switch <b>264</b> includes a threaded portion <b>280</b> that is screwed into a flange portion <b>282</b> formed at an inner end of the outer sleeve <b>278</b>. The outer sleeve <b>278</b> is configured to be press fitted into the hollow tube <b>260</b> formed at the distal end <b>86</b> of the handle post <b>84</b> as shown in FIG. 13.

P-0070[0070] The rotary switch assembly <b>254</b> is biased toward a neutral position between the forward and reverse positions thereof. To this end, the control shaft <b>272</b> is formed to include wedge-shaped camming surfaces <b>284</b> which are configured to cooperate with corresponding, notch-shaped camming surfaces <b>286</b> formed in an inner sleeve <b>288</b> slidably received in the outer sleeve <b>278</b>. The inside surface of the outer sleeve <b>278</b> is formed to include raised guide portions <b>290</b> which are configured to be received in corresponding guide grooves <b>292</b> formed on the outer surface of the inner sleeve <b>288</b>. The reception of the guide portions <b>290</b> of the outer sleeve <b>278</b> in the corresponding guide grooves <b>292</b> in the inner sleeve <b>288</b> allows the inner sleeve <b>288</b> to slide inside the outer sleeve <b>278</b>, while preventing rotation of the inner sleeve <b>288</b> relative to the outer sleeve <b>278</b>. A spring <b>294</b> is disposed between the inner sleeve <b>288</b> and the flange portion <b>282</b> of the outer sleeve <b>278</b>. The spring <b>294</b> biases the camming surfaces <b>286</b> of the inner sleeve <b>288</b> into engagement with the camming surfaces <b>284</b> of the control shaft <b>272</b> to, in turn, bias the thumb wheel <b>274</b> to automatically return to a neutral position thereof when released.

P-0071[0071] Thus, the thumb wheel <b>274</b> is movable to a forward position in which the drive assembly <b>200</b> operates to drive the wheel <b>110</b> in a forward direction to propel the stretcher <b>20</b> in the forward direction, and the thumb wheel <b>274</b> is movable to a reverse position in which the drive assembly <b>200</b> operates to drive the wheel <b>110</b> in a reverse direction to propel the stretcher <b>20</b> in the reverse direction. The handle post <b>84</b> may be marked with an indicia to provide a visual indication of the neutral position of the thumb wheel <b>274</b>.

P-0072[0072] Illustratively, the drive motor <b>202</b> is Model No. M6030/G33, manufactured by Rae Corporation, the linear actuator <b>220</b> is Model No. LA22.1-130-24-01, manufactured by Linak Corporation, and the rotary switch <b>264</b> is Model No. RV6N502C-ND, manufactured by Precision Corporation.

P-0073[0073] FIGS. <b>15</b>-<b>17</b> show an alternative push-type switch assembly <b>300</b> for operating the drive motor <b>202</b>. The push-type switch assembly <b>300</b> is coupled to the distal end <b>86</b> of the handle post <b>84</b> of the first push bar <b>80</b>. The push-type switch assembly <b>300</b> includes a pressure sensitive, push-type switch <b>302</b> positioned inside the hollow tube <b>260</b> formed at the distal end <b>86</b> of the handle post <b>84</b>. Control cables <b>304</b> of the push-type switch <b>302</b> are routed through the hollow tube <b>260</b> for connection to the controller <b>256</b>. The push-type switch <b>302</b> includes a threaded portion <b>306</b> that is screwed into a threaded portion <b>308</b> formed on the inside surface of an outer sleeve <b>310</b>. The outer sleeve <b>310</b> is configured to be press fitted into the hollow tube <b>260</b> of the handle post <b>84</b> as shown in FIGS. 16 and 17. The push-type switch <b>302</b> includes an input shaft <b>312</b> which is configured to be in engagement with a flexible dome-shaped cap <b>314</b>. The flexible dome-shaped cap <b>314</b> is snap fitted over a flange portion <b>316</b> of the outer sleeve <b>310</b>. The farther the input shaft <b>312</b> on the push-type switch <b>302</b> is pushed, the faster the drive motor <b>202</b> runs. A forward/reverse toggle switch <b>318</b> is mounted near a distal end <b>86</b> of the second push bar <b>82</b> to change the direction of the drive motor <b>202</b> as shown in FIG. 15<i>a</i>. Alternatively, the forward/reverse toggle switch <b>318</b> may be located at some other location—for example, the lower frame <b>26</b>.

P-0074[0074] Thus, the forward/reverse toggle switch <b>318</b> is moved to a forward position in which the drive motor <b>202</b> operates to drive the wheel <b>110</b> in a forward direction to propel the stretcher <b>20</b> in the forward direction, and the forward/reverse toggle switch <b>318</b> is moved to a reverse position in which the drive motor <b>202</b> operates to drive the wheel <b>110</b> in a reverse direction to propel the stretcher <b>20</b> in the reverse direction. The speed of the drive motor <b>202</b>, on the other hand, is determined by the extent to which the push-type switch <b>302</b> is pushed. Illustratively, the push-type switch <b>302</b> is of the type sold by Duncan Corporation.

P-0075[0075]FIGS. 18 and 19 show an alternative configuration of the drive assembly <b>350</b> drivingly couplable to the wheel <b>110</b> for propelling the stretcher <b>20</b> along the floor <b>62</b>. As shown therein, the wheel <b>110</b> is mounted directly on an output shaft <b>352</b> of a drive motor <b>354</b>. The drive motor <b>354</b> is, in turn, mounted to a bracket <b>356</b> coupled to the wheel-mounting bracket <b>114</b>. Control cables <b>358</b> of the drive motor <b>354</b> are routed to the controller <b>256</b> along the wheel-mounting bracket <b>114</b>. Illustratively, the drive motor <b>354</b> is of the type sold by Rockland Corporation.

P-0076[0076]FIGS. 19 and 20 show another alternative configuration of the drive assembly <b>400</b> drivingly couplable to the wheel <b>110</b> for propelling the stretcher <b>20</b> along the floor <b>62</b>. As shown therein, the wheel <b>110</b> is mounted directly on a rim portion <b>402</b> of a rotor <b>404</b> of a hub-type drive motor <b>406</b>. The stationary stator shaft <b>408</b> of the hub-type drive motor <b>406</b> is coupled to the wheel-mounting bracket <b>114</b>. Control cables <b>410</b> of the drive motor <b>406</b> are routed to the controller <b>256</b> along the wheel-mounting bracket <b>114</b>. Illustratively, the hub-type drive motor <b>406</b> is Model No. 80-200-48-850, manufactured by PML Manufacturing Company.

P-0077[0077] Although the invention has been described in detail with reference to a certain preferred embodiment, variations and modifications exist within the scope and spirit of the invention as described and as defined in the following claims.