WO2012006719A1

WO2012006719A1 - Stretcher lift

Info

Publication number: WO2012006719A1
Application number: PCT/CA2011/000803
Authority: WO
Inventors: Denis Joanisse
Original assignee: Denis Joanisse
Priority date: 2010-07-15
Filing date: 2011-07-15
Publication date: 2012-01-19

Abstract

A stretcher lift for ambulances, the lift helping ambulance attendants load a wheeled stretcher, with the stretcher carrying a patient, into the ambulance. The lift is characterized in having a tray, a base plate, and drive means. The base plate is adapted to be mounted on the floor of an ambulance adjacent the ambulance's loading entrance. The tray is connected to the base plate for movement relative to the base plate. The drive means selectively move the tray. The drive means can move the tray downward from a storage position where the tray is stored in an upright position on the base plate within the ambulance, to a loading position where the tray is deployed rearward at a downward angle from the base plate outside the ambulance. A stretcher can be wheeled to place the front of the stretcher on the tray in the loading position and the tray can be moved up to lift the stretcher and the tray to a transfer position where the front of the stretcher can be transferred into the ambulance. The invention is also directed toward an ambulance incorporating the stretcher lift and use of the lift.

Description

STRETCHER LIFT

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

[1000] This invention relates to a stretcher lift for an ambulance to help ambulance attendants and/or paramedics place stretchers, with patients thereon, into ambulances. The

invention is also directed toward an ambulance with the

stretcher lift, and to using the stretcher lift for helping to load a stretcher, carrying a patient, into an ambulance.

BACKGROUND ART

[1001] Most ambulance stretchers have a pair of fixed front wheels just underneath the front of the main frame of the stretcher. The fixed front wheels are used for loading the stretcher into an ambulance, the wheels guiding the stretcher in a straight line on the floor of the ambulance. These stretchers also normally have an extendable frame, such as a foldable scissors frame, under the main frame, behind the fixed front wheels, the extendable frame carrying movable or swivel front and rear wheels at the bottom. The extendable frame is normally extended or unfolded beneath the main frame so the main frame of the stretcher, with the patient thereon, is supported on the swivel front and rear wheels at about the waist level of a standing person. The stretcher, carrying the patient, can be easily moved and/or attended to in this position. The extendable frame is withdrawn or collapsed upwardly, moving the movable front and rear wheels up adjacent the main frame, when the stretcher is to be loaded into an ambulance.

[1002] The stretchers, carrying patients, are presently loaded manually into the ambulances. This involves wheeling the stretcher to the loading door of the ambulance when the door is open, lifting the stretcher and moving it forward to place the fixed front wheels of the stretcher on the floor of the ambulance. The scissors frame is then collapsed and the

stretcher is lifted up about the fixed front wheels to raise the front swivel wheels to floor level. The stretcher is then pushed to place the front swivel wheels, and then the rear swivel wheels, on the floor of the stretcher. The combined weight of an average person and stretcher is about three hundred pounds. The initial lifting and longitudinal movement of the loaded

stretcher to get the fixed front wheels of the stretcher onto the floor of the ambulance; having to support the rear of the stretcher initially when the fixed front wheels first contact the floor; and especially having to lift the rear of the stretcher to raise the front swivel wheels level with the floor and move it forward in this position; all can cause injuries. The loss of time due to the work related injuries among

ambulances attendants is substantial.

[1003] It is the purpose of the present invention to provide a stretcher lift that can aid attendants in lifting and loading stretchers into ambulances. The stretcher lift of the present invention simplifies the loading process and significantly reduces the weight the attendants have to handle in loading the stretcher thus minimizing the risk of injuries to the

attendants. The lift can reduce the weight the attendants have to handle by over 50% making the job much easier and leading to fewer job related injuries. The result is substantial savings for ambulance companies and substantial improvement in the health and lives of the attendants.

SUMMARY OF THE INVENTION

[1004] The present invention is directed toward a stretcher lift that can be mounted at the rear of an ambulance floor to help the ambulance attendants lift a stretcher, with a patient on the stretcher, and move the loaded stretcher into the ambulance. The lift attachment has a base plate mounted on the ambulance floor at the rear of the floor. A tray is pivotally mounted on the base plate. The tray can be stored in an upright, stored position in the rear of the ambulance, adjacent the rear door of the ambulance when the door is closed. The tray can be pivoted from the stored position down to a loading position where the tray extends rearward and downward from the ambulance floor when the ambulance door is opened. In the loading

position, the tray normally extends below the fixed front wheels of the stretcher when the extendable frame of the stretcher is extended and the stretcher is on the ground. The stretcher can be wheeled on the ground on the swivel wheels to place the fixed front wheels on the tray. The tray can then be pivoted up from the loading position, carrying the front of the stretcher with it, to a transfer position, where the tray is generally level with the floor, while extending rearward from the ambulance. The stretcher can be rolled off the tray on its fixed front wheels part way into the ambulance with the tray in the transfer position. The extendable frame is then collapsed raising the swivel wheels on the stretcher, as is known. The tray is again lowered to the loading position, this time from the transfer position, while the attendants support the rear of the

stretcher. The stretcher is again moved forwardly by the attendants, rolling it on its fixed front wheels riding on the floor of the ambulance, to move the swivel front wheels of the stretcher onto the tray. The tray is then again raised from the loading position to the transfer position, lifting the movable front wheels of the stretcher higher. With the tray now at floor level in the transfer position, the attendants roll the

stretcher forwardly on the swivel front wheels, off the tray and into the ambulance. It will be seen that the use of the lift results in a good portion of the weight of the stretcher and patient being borne by the tray in raising and moving the loaded stretcher into the ambulance. [1005] The invention is particularly directed toward a

stretcher lift for ambulances, the lift helping ambulance attendants load a wheeled stretcher, with the stretcher carrying a patient, into the ambulance. The lift is characterized in having a tray, and a base plate adapted to be mounted on the floor of an ambulance adjacent the ambulance's loading door. The tray is movably connected to the base plate. The tray is movable between a storage position where the tray is stored in an upright position on the base plate and a loading position where the tray extends rearward and downward from the base plate and where, when the lift is mounted on an ambulance, the stretcher can be wheeled to place the front of the stretcher on the angled tray. The tray can be moved from the loading position to a transfer position where transfer of the stretcher into the ambulance can begin, lifting the front of the stretcher with it, the tray extending rearward from, and generally level with, the base plate in the transfer position.

[1006] The invention is also directed toward an ambulance with a stretcher lift for helping attendants move a wheeled

stretcher, with a patient thereon, into an ambulance. The stretcher lift has a base plate with a tray movably attached to the base plate. The base plate is mounted flat on the floor of the ambulance adjacent a loading door of the ambulance. Drive means are provided on one side of the base plate, the drive means connected to the tray to move the tray. The tray is moved by the drive means between a storage position within the ambulance where the tray is stored upright above the base plate, a loading position outside the ambulance where the tray extends rearward and downward from the ambulance. In the loading position, the tray extends just below the front of the stretcher so that the front of the stretcher can be loaded onto the tray to be lifted by the drive means. [1007] The invention is also directed toward the use of a stretcher lift to help ambulance attendants load a stretcher, carrying a patient, on an ambulance. The stretcher is of the type having an extendable frame under the main frame, behind the front of the stretcher and attached to the main frame, the extendable frame having front and rear swivel wheels. The stretcher lift is mounted on the floor of the ambulance adjacent the loading entrance to the ambulance, the stretcher lift having a tray, the tray normally stored in an upright storage position on the floor adjacent the loading entrance. The use of the lift involves moving the tray down from the storage position to a loading position when the entrance is open, the tray extending rearward from the ambulance and downward in the loading

position. A stretcher on the ground is then wheeled to place the front of the stretcher on the tray while the extendable frame is extended. The tray and the front of the stretcher are then moved up to a transfer position while supporting the rear of the tray with an attendant, the tray extending rearward from the

ambulance and substantially level with the floor at the transfer position. The attendant then moves the stretcher forwardly on the front of the stretcher to move the front of the stretcher off the tray into the ambulance. The tray is then lowered from the transfer position to the loading position

while the attendant supports the rear of the stretcher, and the extendable frame is retracted. The stretcher is pushed forward, riding on the ambulance floor on the front of the stretcher to load the front swivel wheels onto the tray and the tray is then moved up, along with the stretcher, to the transfer position. The stretcher is then pushed off the tray on the swivel wheels into the ambulance, the tray is moved up to the storage

position, and the door is closed.

BRIEF DESCRIPTION OF THE DRAWINGS

[1008] Fig. 1 is a perspective view of the lift mounted on the rear of an ambulance;

[1009] Fig. 2 is a perspective view of the base plate forming part of the lift;

[1010] Fig. 3 is an exploded perspective view of the tray and the bridge plate;

[1011] Fig. 4 is a cross-section view along line 4-4 in Fig. 1;

[1012] Fig. 5 is a cross-section view along line 5-5 in Fig. 4;

[1013] Fig. 6 is a detail, cross-section view showing the connection between the tray and bridge plate;

[1014] Fig. 7 is a cross-section along line 7-7 in Fig. 6;

[1015] Fig. 8 is a cross-section of the drive means taken along 8-8 in Fig. 2;

[1016] Fig. 9 is a cross-section taken along line 9-9 in Fig. 8 [1017] Figs. 10A-10I are schematic views showing the lift in various positions during operation;

[1018] Fig. 11 is a schematic view showing a cam arrangement for controlling the movement of the tray;

[1019] Fig. 12, appearing on the same page as Figs. 8-9, is a detail view showing the mounting of a weight sensor on the base plate ;

[1020] Fig. 13, appearing on the same page as Figs. 8-9, is a cross-section view along line 13-13 in Fig. 12;

[1021] Fig. 14, appearing on the same page as Figs. 8-9, is a detail view of an alternative mounting connecting the tray to the base plate;

[1022] Fig. 15, appearing on the same page as Figs. 8-9, is a detail view showing an alternative connection of the drive shaft to the tray; and

[1023] Fig. 16 is a plan view of a modified bridge plate mounted on the tray.

BEST MODE FOR CARRYING OUT THE INVENTION

[1024] The stretcher lift 1, as shown in Figs. 1-5, has a tray 3 with a bridge plate 5 mounted on the tray 3. The tray 3 is used to help the attendant lift the stretcher as will be described. The tray 3 has a floor 7 with side walls 9, 11 and a rear wall 13 extending up from the sides and rear respectively of the floor. The rear wall 13 angles outwardly from the floor and terminates in a rear edge 14. The floor 7 preferably is a relatively thick, built-up, structural member to provide rigidity and ends in a front wall 15. The floor 7 can taper rearward. The tray 3 has support arms 17, 19 that extend forwardly from the side walls 9, 11 of the tray, past the front wall 15 of the floor 7. The support arms 17, 19 are separate members securely joined to the outside of the side walls 9, 11. The support arms 17, 19 could also be extensions of the side walls 9, 11.

[1025] The bridge plate 5 has a floor 21 with side walls 23, 25 extending up from the sides of the floor. The side walls 23, 25 are angled slightly away from each other. The angling of the side walls 23, 25 prevents the stretcher wheels from bearing against the side walls while the stretcher passes over the plate 5. Floor 21 has a rear edge 27 and a front edge 29, the front portion of the floor 21 angled or curved down slightly to the front edge 29 as shown at 31. The rear edge 27 of floor 21 is adjacent the rear wall 13 of the tray 3, the floor extending well forwardly of the front edge 15 of the tray to just short of the front of the support arms 17, 19. The bridge plate 5 is used to guide the stretcher into the ambulance.

[1026] The bridge plate 5 is mounted to the tray 3 by pivot pins as shown in detail in Figs. 6-7. The side walls 23, 25 of the bridge plate 5 each have a vertical slot 33 near the bottom, back end of the side walls. A bolt 34, threaded through a hole 35 in the lower, back end of each of the side walls 9, 11 of the main tray 3 extends through a slot 33 to pivotally join the rear of the bridge plate 5 to the rear of the tray 3. The bolts 34 can be locked to the side walls 9, 11 with a nut 36 on each side of each wall (only one nut shown) . The bolts 34 act as pivot pins and allow the bridge plate 5 to pivot relative to the tray 3. The slots 33 allow the bridge plate 5 slight movement vertically relative to the tray 3. The mounting of the bridge plate 5 to the tray 3 allows the bridge plate 5 to ^Afloat' relative to the tray 3. Both the tray 3 and the bridge plate 5 could be notched inwardly from their rear edges 14, 27, as shown by the dash lines in Fig. 3, to form notches 37, 38. The notches 37, 38 allow the attendant greater access to the interior of the ambulance, adjacent the ambulance loading entrance.

[1027] The lift 1 includes a base plate 39. The base plate 39 is elongate, sized to extend substantially across the floor 41 of an ambulance 43 as shown in Fig. 1. The base plate 39 is adapted to be mounted flat on the floor 41 of the ambulance 43 adjacent, and parallel to, the loading entrance 44 of the ambulance. The base plate 39 can be detachably mounted on the floor 41 with bolts (not shown) extending through the floor 41 and attaching the base plate 39 to a mounting plate (not shown) beneath the floor. The base plate 39 can have a central cutout 45 extending inwardly from the front side 46 of the plate to accommodate the known safety hook 47 in the floor 41 of the ambulance 43.

[1028] Mounting means are provided for connecting the front of the tray 3 to the base plate 39. The mounting means comprise first and second mounting means 49, 51 on the front of the tray, spaced apart sufficiently to allow the stretcher to pass between them. The mounting means 49, 51 are more specifically mounted on the free ends of the support arms 17, 19 which arms form part of the tray 3 as shown in Fig. 2. The first mounting means 49 can comprise a pivot pin 53 extending laterally from the support arm 17 toward the support arm 19 and securely fixed to the support arm 17. The second mounting means 51 can comprise a through hole 55 in the support arm 19, the interior of the hole 55 being splined as shown at 57 in Fig. 4. The pivot pin 53 is aligned with the through hole 55, the longitudinal axis of the pin 49 and hole 51 aligned to form a pivot axis 59 for the tray 3.

[1029] The mounting means further include third and fourth mounting means 60, 61 on the base plate 39 for cooperatively receiving the first and second mounting means 49, 51

respectively on the tray 3. The third mounting means 60 can comprise a bracket 65 mounted upright on the base plate 39 with a hole 67 there through for rotatably receiving the pivot pin 53 on the first support arm 17 of the tray 3 to form a first pivot 68. The fourth mounting means 61 can comprise a drive shaft 69 extending from a drive means 71 mounted one side of the base plate 39. The drive shaft 69 is aligned with the pivot axis 59 and has a first, slightly reduced diameter, extension 73. The extension 73 is splined, as shown at 75 in Fig. 8, and the extension forms a shoulder 77 with the drive shaft 69. The splined extension 73 fits snugly into the splined hole 55 in the support arm 19 to form a second pivot 78. When splined extension 73 is inserted in the splined opening 55, the shoulder 77 abuts against the second arm 19. A second, smaller, threaded extension 79 extends from the first, splined, extension 73 and projects past the arm 19 when the first extension 73 is inserted full into the opening 55. A lock nut 81 is threaded onto the second extension 79 to retain the tray 3 on the drive shaft 69. The two pivots 68, 78 are spaced apart on the pivot axis 59, wide enough apart to move a stretcher between them.

[1030] The splines on the drive shaft 69 and the end of the support arm 19 could be modified to have a section of both the circumference of the first extension 73 and the splined hole 55 without splines so that there is only one way of mounting the splined extension in the splined hole. This will ensure that the tray 3 is always in the proper position to start the stretcher loading procedure when it is remounted on the first and second mounting means 49, 51. Other constructions on the first

extension 73 on the drive shaft 69 and the hole 55 in the second support arm 19 can be employed to ensure correct mounting of the tray 3 on the base plate 39.

[1031] When the tray 3 is mounted on the base plate 39, the bridge plate 5 spans the gap between the floor 7 of the tray 3 and the top of the base plate 39 as seen in Fig. 1. The mounting means described above allows the tray 3, and attached bridge plate 5, to be easily removed from the base plate 39 for cleaning or replacement. The lock nut 81 is removed and the tray 3 is slid to the right, as seen when viewing Fig. 1, to slide the pivot pin 53 on the support arm 17 out of the hole 67 in bracket 65 on the base plate 39, while simultaneously sliding the splined hole 55 on the support arm 19 off the splined, first extension 73 of the drive shaft 69.

[1032] The drive means 71 mounted on the base plate 39, pivotally raises or lowers the tray 3 relative to the base plate 39 about the pivot axis 59 by rotating the drive shaft 69. The drive means 71 includes a housing 83. Mounted within the housing 83, as shown in Figs. 8 and 9, is the drive shaft 69, the shaft projecting out of the side of the housing 83 toward the bracket 65 on the base plate 39. The drive shaft 69 is aligned with the pivot axis 59 and with the hole 67 in the bracket 65. The drive means 71 includes rotation means 87 for rotating the drive shaft 69 in either direction to predetermined positions. The shaft 69 is rotatably mounted within the housing 83 between two bearing supports 89, 91. The rotation means 87 includes a sprocket-type gear 93 fixed to the shaft 69 between the bearing supports 89, 91. Two hydraulic cylinders 95, 97 are mounted in the housing 83 above the shaft 69. A drive chain 98 is mounted over the gear 93 with the ends 99, 101 of the chain attached to the piston rods 103, 105 respectively of the hydraulic cylinders 95, 97. Moving the piston rods 103, 105 in opposite directions simultaneously will move the chain 98 in one direction or the other, depending on the direction the piston rods 103, 105 are moved, to rotate the drive shaft 69. Rotating the drive shaft 69 will pivot the attached tray 3, via the connection between the splined

extension 73 on the drive shaft 69 and the splined hole 55 on the end of the support arm 19, in one direction or the other about pivot axis 59. Suitable known hydraulic means (not shown) are provided to extend or withdraw the piston rods 103, 105 of the cylinders 95, 97. The drive means 71 move the tray 3 between a storage position, where the tray 3 is upright on the base plate 39 within the ambulance; a loading position, where the tray 3 extends rearward and downward from the base plate outside the ambulance; and a transfer position, where the tray 3 extends rearward from the base plate 39 outside the ambulance.

[1033] The lift attachment 1 has a control panel 107 to control the operation of the lift attachment. The control panel 107 is mounted on the housing 83 of the drive means 71 for access from outside the ambulance through the entrance 44 of the ambulance 43 as shown in Fig. 1. The control panel 107 has an up button 109 used to raise the main tray 3. Pushing the up button 109 once and releasing, will cause the tray 3 to rise from the loading position to the transfer position. Push and continue pushing the up button 109, and the tray 3 will rise from the transfer position to the stored position. A down button 111 below the up button 109 lowers the tray 3. Push and release the down button 111 and the main tray 3 will lower to the loading position either from the storage position or the transfer position. A automate button 113, below the down button 111, will place the movement of the tray 3 in an automatic mode as will be described below. The panel 107 also includes an emergency stop button 115 at the top of the control buttons 109, 111, 113 to stop the tray movement at any time. To reset after hitting the emergency button 115, a dial 117 behind the emergency button 115 can be rotated. The controls are set up so that anytime you wish to stop the tray 3 during its movement, in the automatic mode to be described, you can press any of the three control buttons 109, 111, or 113, or the emergency button 115 on top of the control buttons. While the control panel 107 is shown mounted on the drive means 71, the control panel 107 can also be mounted on the interior wall of the ambulance, on the inside of the rear door of the ambulance, or in a hand held remote, if desired.

[1034] To load the stretcher, with the patient thereon, in the ambulance, the rear door is opened and the tray 3 is moved from its upright stored position within the ambulance, as shown in dotted lines in Fig. 10A, to its loading position outside the ambulance. More specifically, the tray 3 is pivoted counter clockwise by its drive means 71, by pushing the down button 111 to lower the tray. The tray 3 pivots about the pivot axis 59, from its upright, stored position to its loading position by having the drive shaft 69 rotate the required amount in the counter clockwise direction. In the loading position, the tray extends rearward from the back of the ambulance and is angled downward as shown in Fig. 10A. The angle at which the tray slopes down from the horizontal can range between 25° and 45°, but is preferably between 30° and 35°. The support arms 17, 19 can be notched, if required, as shown at 118 in Fig. 1, to accommodate the rear, top corner 119 of the ambulance floor 41 as the arms lower. The tray 3 is sized, and positioned in the loading position, to have the rear wall 13 just below the front of the stretcher S when the stretcher is elevated by the scissors frame SF and riding on its front and rear swivel wheels FSW and RSW as skown in Fig. 10A. More specifically, the rear stretcher. The distance between the front, fixed wheels FW and the front, swivel wheels FSW on the stretchers used with ambulances is normally about twenty two inches and the fixed wheels FW are several inches above the front swivel wheels FSW when the scissors frame SF is folded or retracted against the main frame MF. The tray should be between about sixteen and eighteen inches long to operate properly with most of the stretchers used with ambulances. An attendant will roll the stretcher forward on its swivel wheels FSW, RSW to place the front of the stretcher, and more specifically the fixed front wheels FW of the stretcher on the tray 3 as shown in Fig. 10B.

[1035] The tray 3 is then moved upwardly from the loading position, carrying the front of the stretcher with it, to the transfer position. The tray pivots upwardly in a clockwise direction, by pressing and releasing the up button 109 to rotate the drive shaft 69, to the transfer position shown in Fig. IOC. The attendant who rolled the stretcher supports the rear of the stretcher during this movement if needed. The rear wall 13 of the tray 3 will help retain the fixed front wheels FW on the tray 3. The drive shaft 69 is rotated the required amount in the clockwise direction to place the tray in the transfer position. The bridge plate 5 bridges the gap between the floor 7 of the main tray 3 and the rear edge of the base plate 39 when the tray 3 is in the transfer position, the front portion 31 of the bridge plate 5 bearing on the top of the base plate 39. An attendant then pushes the stretcher forwardly to move the front of the stretcher off the tray 3 onto the floor 41 of the ambulance. The stretcher moves on its fixed front wheels FW as shown in Fig. 10D. The stretcher is pushed just far enough forward to have the safety bar on the bottom front of the stretcher move past the fixed hook 47 on the ambulance floor as the stretcher moves into the ambulance. The hook 47 prevents the stretcher from moving back off the floor during loading. The safety bar can be moved manually when removing the stretcher to pass by the hook 47.

[1036] Once the front of the stretcher is on the floor of the ambulance, the tray 3 is lowered again to the loading position as shown in Fig. 10E. The drive shaft 69 is rotated the required amount counter clockwise by pushing the down button 111 while the rear of the stretcher is supported by an attendant. Both the front and rear swivel wheels FSW, RSW on the stretcher are moved up by the attendant retracting the scissors frame SF against the main frame MF. The tray 3 must be short enough to allow the front swivel wheels FSW to clear the tray when the scissors frame SF is retracted. The attendant then moves the stretcher forwardly, it riding now on its fixed wheels FW on the ambulance floor, to move the front swivel wheels FSW onto the tray 3 as shown in Fig. 10F. The tray is then again moved up to the transfer position, by pushing the up button 109, as shown in Fig. 10G. At the transfer position, an attendant pushes the stretcher forward again, this time on its swivel front wheels FSW as shown in Fig. 10H, to move the swivel front wheels FSW off the tray and onto the ambulance floor. The attendent continues pushing to move the entire stretcher into the

ambulance, the stretcher eventually resting on both the front and rear swivel wheels FSW, RSW. Once the stretcher is in the ambulance, the tray 3 is raised to a vertical stored position within the ambulance, as shown in Fig. 101, by pushing the up button 109 and this time, continuing to push it. The ambulance door is closed when the tray is in the stored position. The stretcher can be unloaded by merely reversing the loading procedure .

[1037] The amount of rotation of the drive shaft 69, clockwise and counter clockwise, to place the tray 3 in the various positions at various times during loading of the stretcher can be controlled in various known ways. A simple and inexpensive way is to use a set of cams 121A, 121B, 121C as shown in Fig. 11. The cams 121 can be mounted on a shaft 122 extending axially from the rear of the drive shaft 69 within the drive means 71. Each cam 121 has a high point 123 that can be set where required to stop the tray in a desired position. The high point 123 on each cam 121 lifts a roller 124 running on the periphery of the cam to move an actuator 125 attached to the roller 124. The actuator 125 moved by the cam 121A, 121B or 121C opens a relay 127A, 127B or 127C associated with the cam. The relay 127 is closed by pushing on the control button associated with that particular relay and cam depending on the tray movement

required. When the relay 127 is closed, it actuates the

hydraulic system 128 to provide fluid to the hydraulic cylinders 95, 97 in a manner to rotate the drive shaft 69 in the required direction and the required amount to provide the tray movement desired. When the relay is opened by the cam associated with it, the tray stops in the desired position.

[1038] To set the first cam 121A in the proper operational position, the tray 3 is moved by hand from the stored position to the loading position. At the loading position, the cam 121A is loosely rotated on the shaft 122 so that its high point 123 is located to open the relay 127A operating the hydraulic supply 128 which provides the correct direction of rotational movement and the correct amount of rotation when the down button 111 associated with the relay 127A is pressed. The cam 121A is then locked in the position, where its high point 123 opens the relay 127A, by screws (not shown) on the cam 121A bearing against the shaft 122. Opening the relay 127A ends the movement of the tray at the loading position. Each of the other two cams 121B and 121C are set similiarly to control movement from the loading position to the transfer position, and from the transfer position to the storage position respectively.

[1039] With the cams 121 set, when the loading of the stretcher is initiated by pressing the down control 111 button, the relay 127A operates the hydraulic supply 128 to rotate the drive shaft 69 counter clockwise to move the tray 3 down. As the drive shaft 69 rotates, the cam 121A also rotates until, when the tray is in the proper loading position, the high point 123 on the cam 121A opens the relay 127A, stopping movement of the tray. When loading is completed, the up control button 111 is pushed next, and immediately released to raise the tray 3 along with the front of the stretcher on the tray. The relay 127B associated with the second cam 121B is closed and the hydraulic supply 128 rotates the drive shaft 69 clockwise until the tray 3 reaches the transfer position at which time the high point 123 on the cam 121B opens the relay 127B stopping movement. When transfer is completed, the tray is moved down a second time, this time from the transfer position, to the loading position, to allow the swivel wheels to be loaded on the tray. Moving down is again accomplished by pressing and releasing the down button 111 with the high point 123 on cam 121A associated with this button again stopping the tray at the loading position. After loading a second time, the tray is then lifted to the transfer position a second time by pressing and releasing the up button 109, as before with the high point on the second cam 121B opening the relay 127B to stop movement of the tray when the transfer position is reached. Once the second transfer is completed and the stretcher is all on the ambulance floor, the up button 109 is pressed and pressing continues, to close the third relay 121C which causes the hydraulic supply to move the tray up to the storage position and when the storage position is reached the high point on the third cam 121C stops the movement. The cam arrangement for controlling the movement of the tray is

relatively simple and inexpensive. Other known shaft movement controlling means can be used such as electronic encoders or optical encoders.

[1040] The operation of the lift 1 can be at least partly automated using weight sensors. The use of a floating bridge plate 5 on the lift facilitates the use of the weight sensors. Weight sensors are preferably provided on the tray 3, under the bridge plate 5, and on the base plate 39 for sensing a minimum weight, such as between, and including, five to ten pounds, on the tray. The weight sensor 131 on the base plate 39 is located behind the safety hook 47. A thin flexible plate 133 with a cutout 135 for the safety hook 47, as shown in Figs. 12 and 13, is provided as a protective cover for the sensor 131. The plate 133 has two cuts 137, 139, one on each side of the cutout 135, extending forwardly from the rear edge 141 to just past the end of the cutout 135, to form a flexible flap 143. The weight sensor 131, in the form of a strip, is adhered to the base plate 39 adjacent its rear edge 145 in line with the safety hook 47. The plate 133 is placed over the sensor 131 and fastened with screws to the base plate 39. The sensor 131 is under the flap 143 raising it slightly. The sensor, in this location would be located under the front edge 29 of the floor 21 of the bridge plate 5, the front edge being bent downwardly as shown at 31, to press on the flap 143 over the weight sensor 131. Preferably, two additional strip sensors 133, 135 are mounted on the floor 7 of the main tray 3 under the bridge plate 5 as shown in Fig. 3. When a stretcher's wheels roll onto the tray 3, even though the tray is angled, the sensors 131, 133, 135 will sense at least part of the weight of the stretcher as it is pushed against the tray, and this can be used to automate the stretcher loading process .

[1041] Using the weight sensors, the stretcher loading process can be automated after the tray 3 has been lowered to the loading position by pushing the down button 111 to initiate loading. With the tray in the loading position, pushing the automate button 113 on the control panel will automate loading. Now, when the stretcher is pushed forwardly to have the fixed, front wheels FW contact the tray 3, the tray 3 will

automatically rise to the transfer position on the wheel contact when at least one of the sensors 131, 133, 135 sense pressure of five-ten pounds from the fixed front wheels FW of the stretcher. The wheels press on the floor 21 of the bridge plate 5

transferring weight through the plate to the sensors 133, 135. Once the fixed front wheels FW are rolled off the tray and onto the ambulance floor, the weight sensors sense the removal of the wheels and the tray will be automatically moved down to the loading position to receive the front swivel wheels FSW of the stretcher. The sensors again sense the load imposed by the front swivel wheels FSW as they are moved onto the bridge plate 5 on the tray 3 and again automatically raise the tray to the transfer position and retain it there so that both the front and rear swivel wheels SW can be moved onto the ambulance floor. After both sets of swivel wheels are rolled off the tray onto the ambulance, the unit will automatically move the tray to the stored position. A suitable programmable logic controller (PLC), such as a unit sold by Siemens under their "LOGO!" trademark can be used to automate the above steps.

[1042] While one form of rotating means for rotating the drive shaft in either direction has been described, using hydraulic cylinders and a belt and sprocket type gear arrangement, other rotating means can be employed. A drive gear could, for example, be used in the place of the belt to rotate a regular gear, replacing the sprocket type gear, on the drive shaft. A

hydraulic or electric motor could be used to rotate the drive gear which engages the driven gear on the drive shaft. [1043] While one form of connection between the tray, the base plate, and the drive means has been described, other

arrangements can be employed. For example, as shown in Figs. 13 and 14, the second mounting means 51A can comprise a drive pin 151 securely fixed to the end 153 of the second arm 19A and extending laterally from the second arm toward the drive means 71. The drive pin 151 can be rotatably mounted through a hole 155 in a second bracket 157 on the base plate 39, the second bracket 157 forming the fourth mounting means 73A and located adjacent the second arm 19A on the drive means side of the arm. The bracket 157 and the drive pin 151 form the second pivot means 78A. The drive shaft 69A extends from the drive means 71 as before and is axially connected to the end of the drive pin 151 by suitable detachable connecting means. The drive shaft 69A and drive pin 151, have the same diameter and are axially aligned on the pivot axis 59. The drive shaft 69A and drive pin 151 have semi-cylindrical tabs 159, 161 respectively formed from their free ends 163, 165. The tabs 159, 161 are abutted and joined by a bolt 167 and nut 169, the bolt 167 passing through the tabs 159 and 161 transversely to the pivot axis 59. Other suitable detachable, connecting means can be used to join the tabs. Other types of detachable connecting means can be used to join the drive shaft 69A and drive pin 151.

[1044] The bridge plate 5 can be modified for manual operation of the lift using the up and down buttons 117, 119. The modified bridge plate 5A can comprise a flat plate 171 that is attached at its rear edge 173 by a pivot 175 to the rear of the bottom plate 7 of the tray 3 at the rear wall 13 of the tray. The front edge 177 of the bridge plate 5A extends past the front edge of the tray 3, terminating just short of the ends of the support arms 17, 19. The bridge plate 5A will span the gap between the front 15 of the tray 3 and the base plate 39. The modified bridge plate 5A can have side walls if desired that angle outwardly, similar to side walls 23, 25 on the bridge plate 5.

[1045] The lift can include safety features. A shut-off switch can be operated by the ambulance door when it is closed, to prevent operation of the lift. The lift can be equipped with a sensing device that, when the tray, while moving, encounters a resistance, such as a person's body, it automatically stops movement to avoid injury to the person. Usually, an ambulance has two attendants and one attendant can support the rear of the stretcher when needed when loading the stretcher, while the other attendant operates the control panel and retracts the scissors frame. The unit however permits a single attendant to load the stretcher if needed. He can do so with the control panel on a hand held remote.

Claims

I claim:

1. A stretcher lift for ambulances, the lift helping ambulance attendants load a wheeled stretcher, with the stretcher carrying a patient, into the ambulance, the lift characterized in having: a tray, a base plate adapted to be mounted on the floor of an ambulance adjacent the ambulance's loading entrance, the tray connected to the base plate for movement relative to the base plate, a drive means for selectively moving the tray, the drive means able to move the tray downward from a storage position where the tray is stored in an upright position on the base plate, to a loading position where the tray is deployed rearward at a downward angle from the base plate and where, when the lift is mounted on an ambulance with the tray deployed, the stretcher can be wheeled to place the front of the stretcher on the angled tray.

2. A stretcher lift as claimed in claim 1 wherein the front of the tray is connected to the base plate by first and second spaced apart pivot means, the first and second pivot means defining a pivot axis parallel with the base plate and with the loading entrance of the ambulance when the base plate is mounted in the ambulance, the drive means pivoting the tray about the pivot axis to be able to move the tray from the storage position to the loading position.

3. A stretcher lift as claimed in claim 2 wherein the drive means is on the base plate on one side of the first and second pivot means and has a drive shaft aligned with the pivot axis, the drive shaft forming part of one of the pivot means and having its free end releaseably, fixedly connected to another part of the one pivot means on the tray.

4. A stretcher lift as claimed in claim 2 wherein the drive means is on one side of the first and second pivot means and has a drive shaft aligned with the pivot axis, the drive shaft detachably connected to one of the pivot means on the tray.

5. A stretcher lift as claimed in claim 1 wherein the tray includes a floor and arms on the side of the tray projecting forwardly from the front of the floor to the base plate; a bridge plate on the tray, the bridge plate pivotally attached to the rear of the tray and extending from the rear of the tray, past the front of the floor to the base plate.

6. A stretcher lift as claimed in claim 5 wherein the bridge plate is pivotally attached to the tray through a slot in the plate extending transverse to the floor of the tray allowing the bridge plate to both pivot and to move toward and away from the tray at the slot.

7. A stretcher lift as claimed in claims 5 wherein the lift has a weight sensor mounted on the base plate, the free end of the bridge plate bearable on the weight sensor, the weight sensor used to help automatically move the tray.

8. A stretcher lift as claimed in claims 6 wherein the lift has a pair of weight sensors mounted between the bridge plate and the floor of the tray, the weight sensors used to help

automatically move the tray.

9. A stretcher lift as claimed in claim 2 wherein the drive means is mounted on one side of the base plate and comprises a drive shaft rotatably mounted within a housing and extending from the housing to be aligned with, and connected to the tray, through one of the pivot means; the drive means having operating means actuated by two hydraulic cylinders within the housing to rotate the drive shaft via a belt, and thus the tray, in either direction .

10. A stretcher lift as claimed in claim 2 wherein the pivot means include a fixed pivot pin on one side of the tray and a splined hole on the other side of the tray, the pivot means further including a bracket on the base plate with a hole for rotatably receiving the fixed pivot pin and a drive shaft extending from the drive means and having a splined end, the fixed pivot pin rotatably mounted in the hole in the bracket and extending toward the splined hole to form the first pivot means; the splined hole fixedly mounted on the splined end of the drive shaft to form the second pivot means whereby rotation of the drive shaft will rotate the tray.

11. A stretcher lift as claimed in claim 10 wherein the drive shaft has a short threaded end extending from the splined end, the threaded end extending past the side of the tray toward the other side when the drive shaft is passed through the splined hole in the one side; and a nut threadable on the threaded end to retain the tray on the drive shaft.

12. A stretcher lift as claimed in claim 1 wherein the tray extends downward at an angle of between 25° and 45° and has a length ranging between sixteen and eighteen inches.

13. A stretcher lift for ambulances, the lift helping ambulance attendants load a stretcher, with the stretcher carrying a patient, into the ambulance; the stretcher being of the type having a main frame with fixed wheels at the front of the main frame and front and rear swivel wheels on the main frame behind the fixed wheels, the front and rear swivel wheels capable of being raised or lowered; the lift characterized in having: a tray; a base plate adapted to be mounted on the floor of an ambulance adjacent the ambulance's loading door; the tray connected to the base plate for movement relative to the base plate; the tray movable from a storage position where the tray is stored in an upright position on the base plate to a loading position where the tray extends rearward and downward from the base plate and where the tray, when the unit is mounted in an ambulance, is angled downwardly far enough, and is long enough, to extend just below the fixed wheels on the stretcher when the swivel wheels are lowered, so that the stretcher can be wheeled to place the fixed wheels on the tray

14. A stretcher lift as claimed in claim 13 wherein the front of the tray is connected to the base plate by first and second spaced apart pivot means, the first and second pivot means defining a pivot axis parallel with the base plate and with the loading entrance of the ambulance when the base plate is mounted in the ambulance, and a drive means connected to the tray for pivoting the tray about the pivot axis to be able to move the tray from the storage position to the loading position.

15. An ambulance having a floor and a stretcher entrance closed by a door; the ambulance adapted to receive a stretcher of the type having a main frame with fixed front wheels under the front of the main frame and an extendable frame under the main frame, behind the front wheels, attached to the main frame, the extendable frame having front and rear swivel wheels; the ambulance having a stretcher lift, the lift having a base plate and a tray, the base plate attached to the floor of the

ambulance adjacent the stretcher entrance, the tray movably attached to the base plate, the tray stored in an upright storage position on the base plate in the ambulance adjacent the door when the door is closed, the tray movable from the storage position to a loading position when the door is open, the tray extending rearward out of the ambulance and angled downward in the loading position, the tray located in the loading position so that a stretcher, with the extendable frame extended, that is to be loaded into the ambulance, can be wheeled to place the front fixed wheels on the tray.

16. An ambulance as claimed in claim 15 wherein the front of the tray is attached to the base plate by two spaced apart pivot means; the tray pivotable about a pivot axis passing through the pivot means; the pivot axis parallel to the ambulance entrance and to the base plate; drive means on the base plate outside the pivot means, the drive means connected to one side of the tray to pivot the tray from the storage position to the loading position .

17. An ambulance as claimed in claim 16 wherein the tray has a floor receiving the wheels of the stretcher and arms extending forward from the floor of the tray to the pivot means, the tray including a bridge plate, the bridge plate movably attached at its end to the tray and extending over the floor of the tray and past the floor to lie on the base plate when the tray is in the loading position.

18. An ambulance as claimed in claim 17 wherein the bridge plate is pivotally attached to the tray through a slot in the plate extending transverse to the floor of the tray allowing the bridge plate to both pivot and to move toward and away from the tray at the slot.

19. An ambulance as claimed in claim 18 wherein the lift has a weight sensor mounted on the base plate, the free end of the bridge plate bearable on the weight sensor; and at least one weight sensor between the tray and the plate, the weight sensors used to help automatically move the tray.

20. A stretcher lift as claimed in claims 17 or 18 wherein the lift has a pair of weight sensors mounted between the bridge plate and the floor of the tray, the weight sensors used to help automatically move the tray.

21. The use of a stretcher lift to help ambulance attendants load a stretcher, carrying a patient, on an ambulance; the stretcher of the type having a main frame and an extendable frame under the main frame, attached to the main frame behind the front of the stretcher, the extendable frame having front and rear swivel wheels; the stretcher lift mounted on the floor of the ambulance adjacent the loading entrance to the ambulance, the stretcher lift having a movable tray, the tray normally stored in an upright storage position on the floor adjacent the loading entrance; the use of the lift involving moving the tray down from the storage position to a loading position when the entrance is open, the tray extending rearward from the ambulance and downward in the loading position; wheeling a stretcher, having its extendable frame extended, on the ground to place the front of the main frame on the tray in the loading position; moving the tray and the front of the stretcher up to a transfer position while an attendant supports the rear of the stretcher if needed, the tray extending rearward from the ambulance and substantially level with the floor at the transfer position; the attendant moving the stretcher forwardly at the transfer position to move the front of the stretcher off the tray into the ambulance.

22. The use of the stretcher lift as claimed in claim 21 including retracting the extendable frame on the stretcher and lowering the tray from the transfer position to the loading position while supporting the rear of the stretcher with the front of the stretcher on the ambulance floor; pushing the stretcher forwardly to place the retracted front swivel wheels of the stretcher onto the tray in the loading position; moving the tray with the front swivel wheels up to the transfer position while supporting the rear of the stretcher; pushing the stretcher on the swivel wheels at the transfer position into the ambulance; moving the tray up to the storage position; and closing the door.

23. The use of the stretcher lift as claimed in claim 22 wherein the various up and down movements of the tray, moving it to the various positions, are initiated manually by pushing control buttons which activate hydraulic means to move the tray.

24. The use of the stretcher lift as claimed in claim 22 wherein the various up and down movements of the tray, moving it to various positions, after the first movement, are initiated by moving the stretcher on or off weight sensors carried by the unit .

25. The use of the stretcher lift as claimed in claim 24 wherein at least some of the sensors are carried by the tray.