US3436769A - Hospital bed with friction drive - Google Patents

Description

April 8, 1969 F. J. BURST 3,436,769

HOSPITAL BED WITH FRICTION DRIVE Filed NOV. 24, 1967 Sheet I of 8 *3 a s 1 672 501' Eanozls Jflars i April 8, 1969 F. J. BURST HOSPITAL BED WITH FRICTION DRIVE Sheet 3 018 mNN Filed Nov. 24, 1967 April 8, 1969 F. J. BURST HOSPITAL BED WITH FRICTION DRIVE Sheet Filed Nov. 24, 1967 April 8, 1969 F. J. BURST HOSPITAL BED WITH FRICTION DRIVE 4 Ora Sheet Filed Nov. 24, 1967 Sheet F. J. BURST HOSPITAL BED WITH FRICTION DRIVE E 022045 tffiunsf April 8, 1969 Filed Nov. 24, 1967 April 8, 1969 F. J. BURST HOSPITAL BED WITH FRICTION DRIVE Sheet 5 rs $5 ba J S N A Filed Nov. 24, 1967 April 8, 1969 F. J. BURST 3,436,769

HOSPITAL BED WITH FRICTION DRIVE Filed Nov. 24, 1967 Y Sheet 7 of a IL lit Z1335 I [6 I l arr-r- LL #110 'I' g} ii 11;? 1'12 1% \L :1 I E April 8, 1969 F. J. BURST HOSPITAL BED WITH FRICTION DRIVE Filed Nov. 24, 1967 Jazz 01" finned; I]. 510292 United States Patent 3,436,769 HOSPITAL BED WITH FRICTION DRIVE Francis J. Burst, Batesville, Ind., assignor to Hill-Rom Company, Inc., Batesville, Ind., a corporation of Indiana Filed Nov. 24, 1967, Ser. No. 685,421 Int. Cl. A61g 7/06, 7/00; F16h 15/00 US. Cl. -67 13 Claims ABSTRACT OF THE DISCLOSURE A hospital bed having an electric motor and a friction drive selectively moved to connect the motor to mechanism for elevating the bed or to mechanism for elevating the head section of the spring frame of the bed, the motor being reversible to lower the portion of the bed to which it is connected.

This invention relates to electric hospital beds and has for its principal object the provision of a new and improved bed of this kind.

It is a main object of the invention to provide, without sacrificing quality, an electric hospital bed at a cost comparable to that of manually operated beds, thereby to render electric beds available for installations where the cost of prior art electric hospital beds has been deemed detrimental.

Another object of the invention is to provide in a hospital bed a friction drive mechanism selectively positioned by manual means not available to a patient in the bed, which mechanism is operated by an electric motor that is controlled by means available to a patient in the bed.

Another object of the invention is to provide in a hospital bed a power unit mounted for translatory movement transversely of the bed and containing an electric motor, a drive shaft upon which a pulley and a drive wheel are fixed, a belt connecting the motor to the pulley and spring means for maintaining a predetermined tension on said belt.

Another object of the invention is to provide in a hos pital bed a control rod journaled in the frame of the bed, rotatable around its axis in both directions from a neutral position to establish limit positions for the operating mechanisms of the bed and movable axially to operate a switch to start and stop the electric motor by which the operating mechanisms are activated.

Another object of the invention is to provide in a fricion driven electric hospital bed a screw rotatable to elevate the head section of the spring frame and means enabling said screw to elevate the knee section of the frame as the head section is elevated to prevent a patient in the bed from gravitating towards the foot of the bed.

Another object of the invention is to provide in a hi-low hospital bed that is capable of being placed in T rendelenberg positions, a mechanism for limiting the development of slack in the cables leading to the end of the bed that is retained in elevated position while the other end of the bed is lowered.

Further objects of the invention not specifically mentioned here will be apparent from the detailed description and claims which follow, reference being had to the accompanying drawings in which a preferred embodiment of the invention is shown by way of example and in which:

FIGURE 1 is a plan view of a hospital bed embodying the invention with a part of the protective covers removed;

FIGURE 2 is a side elevational view of the bed in normal position and with the protective covers in place and with a part broken away to show parts hidden thereby;

FIGURE 3 is a foot end elevational view of the bed drawn to an enlarged scale and with the foot board removed;

FIGURE 4 is a plan view of the friction power unit in neutral position, partly in cross section and drawn to an enlarged scale;

FIGURE 5 is a plan view of the power unit in one operated position;

FIGURE 6 is a cross sectional view taken along the line 66 of FIGURE 5 looking in the direction of the arrows;

FIGURE '7 is a side elevational view of the power unit, partly in cross section through the drive shaft mounting;

FIGURE 8 is an elevational view, partly in cross section and showing the selector lever;

FIGURE 9 is a plan view of the structure shown in FIGURE 8;

FIGURE 10 is a the bed;

FIGURE 11 is an end elevational view partly in sections along the line 11-11 of FIGURE 10;

FIGURE 12 is a fragmentary cross sectional view of the hi-low nut in limit position;

FIGURE 13 is a fragmentary view of the head elevating mechanism in normal position taken along the line 1313 of FIGURE 1;

FIGURE 14 is a fragmentary view of the automatic knee elevating mechanism taken along the line 14-14 of FIGURE 1;

FIGURE 15 is a fragmentary view, partly in cross section along the line 1515 of FIGURE 1 showing the manual foot end control mechanism; and

FIGURE 16 is a fragmentary cross sectional view taken along the line 1616 of FIGURE 15.

Present day hospital beds are usually of the so-called hi-low variety in which the frame of the bed is supported by cables attached to the tops of the legs of the bed which are telescoped into posts at the corners of the bed. Mechanism for operating the bed to elevate the same to a height convenient to a nurse or doctor administering to a patient in the bed are in certain instances manually operated and in other instances an electric motor is employed for this purpose. These beds contain the usual articulated spring frame together with a mechanism for elevating the head section of the frame, mechanism for elevating the thigh section thereof, and mechanism for elevating the foot section of the spring frame. In certain beds these mechanisms are all manually operated and in other beds an electric motor is used for this purpose.

Electrically operated hospital beds are necessarily more costly than manually operated beds and there are many places in a hospital where the hospital administrators find it diflicult to justify the added cost of an electric bed and consequently manual beds are commonly used at these locations.

The present invention seeks to render available, without sacrificing quality, an electric bed at a cost more nearly comparable to the cost of a manual bed, thereby to render electric beds available for many uses now dominated by manually operated beds. In the production of the low cost electric bed, most, if not all, of the features of the more expensive electric beds are retained.

The bed of the present invention includes a pair of screw shafts journaled in the main frame of the bed, each shaft having a friction wheel fixed upon it and disposed within a cross channel at the foot end of the bed. One of these screw shafts is equipped to operate the hilow mechanism of the bed and the other equipped to operate the mechanism for raising and lowering the head section of the spring frame and when it is desired to do so to simultaneously raise the thigh section of the spring frame slightly so as to prevent a patient in the bed from gravitating to the bottom thereof.

The power unit of the bed consists of an electric motor mounted for movement transversely of the bed and plan view of the drive mechanism of coupled to a drive shaft by a belt which drive shaft is journaled in a housing member that is attached to the motor mount for movement transversely of the bed. The drive shaft contain a drive wheel, normally located midway between the two friction wheels and moved into engagement with one or the other of these wheels by the transverse movement of the power unit. An apparatus for effecting this selective movement of the drive wheel is located on the foot end of the bed and hence not available to a patient lying in the bed.

Control means for starting and stopping the motor are located in the seat section of the spring frame and hence readily available to a patient in the bed. Since it is rarely desirable to elevate the thigh section more than required to prevent the patient from gravitating to the foot of the bed when the head section of the spring frame is in elevated position the usual manual control of the thigh section is included so that when necessary in the treatment of a patient in the bed the thigh section can be elevated as required by that treatment. The usual manual arrangement for elevating the foot section of the spring frame to put the bed in so-called contour position is likewise retained.

The invention will be best understood by reference to the drawings where in FIGURES 1, 2 and .3, it will be seen that the bed contains a main frame which has at the head end of the bed posts 11 and 12 between which a channel 13 is fixed. As will be seen in FIGURE 2 the channel 13 is disposed with its web located on the side towards the foot of the bed and there is a cover 14 that extends between the flanges of the channel to close off the same. A head board 15 of suitable design is supported upon the channel and posts in known manner.

Located at the foot end of the bed are posts 18 and 19 between which a channel 20 is extended and disposed with its web on the side towards the head end of the bed. A foot board 21 is fixed to the posts 18 and 19 by known means and extends to the bottom of the channel 20 serving as a cover therefor, as will presently appear.

Extending between the posts 11 and 19 is a side rail composed of rectangular tubing and having an end section 22 fixed to the post 11 and extending inwardly therefrom at an angle with respect to the longitudinal median line of the bed. Section 22 merges into a middle section 23 which is disposed parallel to the longitudinal median line of the bed and merges into an end section 24 which extends outwardly to the post 19 to which it is attached.

On the other side of the bed is a similar side rail having an end section 25 fixed to the post 12 and extending inwardly therefrom and merging into a middle section 26 which is parallel to the section 23 which merges into an end section 27 which is fixed to post 18. Cross members 28, 29 and 30 extend between the side rails and are fixed thereto.

Fixed to the middle section 23 of the side rail is a seat support member 31 which as will be seen best in FIGURE 3 extends upwardly and outwardly from the side rail. A similar seat support 32 is fixed to the middle section 26 and extends upwardly and outwardly therefrom. The seat section 34 of the spring frame is attached to these supports.

The head section 33 of the spring frame is pivotally connected to one side of the seat supports 31 and 32 in the usual manner and the thigh section 35 is pivotally connected to the other side of the seat supports. The foot section 36 of the spring frame is pivotally connected to the thigh section 35 in the usual manner.

The spring frame members are preferably angles to which the usual spring fabric is attached, which fabric has been omitted from the drawings to avoid an unnecessary complication thereof.

As will be seen best in FIGURES l0 and 11, fixed to and extending between the cross members 29 and 30 of the main frame is a guide 40 which is rectangular in cross section and has an open top. Journaled in the cross member 29 and located centrally 0f the guide 40 is a hilow screw shaft 41 which as will be seen best in FIG- URE 5 is connected by a coupling 42 to a stub shaft 43 that is journaled in a thrust bearing 44 mounted in the web of channel 20. A friction wheel 45 is fixed upon shaft 43 with its hub 46 engaging the movable portion of the thrust bearing 44. Also fixed to and extending between cross members 29 and 30 is a similar guide 47 and centrally located in this guide 47 is a head operating screw shaft 48 which as will be seen in FIGURE 5 is journaled in a thrust bearing 49 carried upon the web of channel 20, the shaft extending through this bearing and web. Fixed upon the end of the shaft 48 disposed within the channel is a friction wheel 50, the hub 51 of which abuts against the inner member of the thrust bearing. It will be noted that screw shafts 41 and 48 are disposed parallel to each other and that there is an appreciable distance between the adjacent edges of friction wheels 45 and 50.

As will be seen best in FIGURES l, 10, 11 and 12, the hi-low mechanism includes a nut 55 threaded upon shaft 41 and disposed in the guide 40. This nut contains four openings, the axes of which are parallel to the axis of the shaft 41. Fitted against the end of the nut 55 are the webs of a pair of channel shaped catch plates 56 and 57 which webs contain perforations aligned with the holes in the nut 55.

A pair of cables 58 and 59 extend through the nut and the web of catch plates 56 and terminate in a cable fastening device of known design. These cables extend along the shaft to a pair of double groove pulleys 60 journaled in the cross member 28 of the main frame of the bed. Preferably the member 28 is a rectangular tubing and the pulleys 60 are journaled within the tubing, there being openings in the vertical walls of the tubing to permit entrance and exit of the cables.

Cable 59 extends from one of the pulleys through an opening 61 in the vertical wall of the side rail at the junction of sections 22 and 23 thereof. The cable extends through the end section 22 around a sheave 62 journaled in that section adjacent the post 11, thence upwardly to a point of attachment at the top of the leg 11' telescoped in post 11.

Cable 58 extends around the other pulley of the pair 60, thence through an opening 63 in the vertical wall of the side rail at the junction of sections 25 and .26 thereof, thence thru the end section 25 and around a sheave 64 and upwardly to a point of attachment at the top of the leg 12' telescoped in the post 12. A second pair of cables 65 and 66 extend through a perforation in the web of catch plate 57 and the openings in the nut 55 aligned therewith, thence around the other grooves in the pair of pulleys 60, cable 65 then extending through an opening 67 at the junction of sections 26 and 27 of the side rail, thence through the section 27 around a sheave 68 and thence upwardly to a point of attachment at the top of the leg 18 telescoped in the post 18. In a similar manner cable 66 extends through an opening 67' at the junction of sections 23 and 24 of the side rail, around a sheave 68' journaled in the end section 24, thence upwardly to a point of attachment at the top of a leg 19' telescoped into the post 19. Through this arrangement the frame of the bed is hung on the legs telescoped into the post by the cables and the tension on the cables maintains the catch plates 56 and 57 snugly against the end of the nut 55.

As will be seen in FIGURES 1 and 13, the bed is equipped with the usual mechanism for elevating and lowering the head section of the spring frame. This mechanism includes a cross tube 70 fixed to the head section 33 of the bed near its pivotal connection to the seat section 34'. A pair of crank arms 71 are fixed upon the cross tube 70 and equipped with pins 72 which project through slots 73 in the operate bars 74 which bars at their distal ends are pivotally connected to opposite sides of the nut 75 that is threaded upon the shaft 48. Movement of the nut 75 in one direction elevates the head section of the bed in known manner, and when moved in the opposite direction lowers that section.

As will be seen in FIGURES l, 2 and 14, the head section 33 of the spring frame is equipped with a cross tube 76 on the main frame with a levelizer 77. The levelizer is engaged by the cross tube when the section 33 is in horizontal position. Should treatment of a patient in the bed require the head section 33 to be placed below horizontal while the other sections of the spring frame are horizontal the levelizer must be moved. To this end the levelizer is pivotally connected to the sections 23 and 26 of the main frame and can be rotated on its pivots away from the stop block 78 into the postiion shown in dotted lines in FIGURE 14. Head sections may then be lowered until cross tube engages the side rails of the main frame.

Power unit As will be seen in FIGURES 4 through 7 inclusive, the power unit consists of a motor support indicated generally at 80 and containing a horizontal portion 81 that is supported upon the bottom portion of the cross member 30 of the main frame by a low friction mounting bushing 82 which projects through a slot 83 in the member 30 and by buttons 82' which engage member 30. The horizontal member contains a channel shaped depressed portion 81' and terminates in an upstanding flange 84 best seen in FIGURE 6. This flange is attached to the web of the channel 20 by a low friction bushing 85 that extends through a horizontal slot 85' in the web of the channel.

The drive shaft housing indicated generally at 86 consists of a channel shaped front member 87, the web of which is supported upon the web of the channel 20 by four low friction bushings 88 each of which is registered with and supported in a horizontal slot in the web of channel 20. The housing includes a back plate 89 fixed to the flanges of the front channel 87 in convenient manner such as by welding. Thrust bearings 90 are mounted in the web of the member 87 and in the back member 89 and the drive shaft 91 is journaled in these bearings and extends through a suitable opening in the web of channel 20. The drive wheel 92 is fixed upon the drive shaft and disposed between the friction wheels 45 and 50 the shaft being held against axial movement by the hub of the drive wheel 92 and by a collar 93 secured on the shaft. A pulley 94 is fixed upon the drive shaft between the thrust bearings 90. The motor support 80 and the drive shaft housing 86 are connected together by a link 95, preferably a channel, welded to the flange 84 of the motor support and to the web of the front member 87 of the housing. Through this arrangement the motor support and the housing are capable of translatory movement as a unit, which movement is transversely of the bed.

Disposed in the depressed portion 81' of the motor suppotr 81 is a motor slide plate 97 from the ends of which flanges 98 project downwardly. Fixed in the motor support plate 81 and extending through slots in the flanges 98 is a stationary pin 99. Fixed in the flanges 98 and extending through slots in the motor support 81 is a movable pin 100. Springs 101 are connected between the stationary and movable pins. The motor 102, which may be any one of a number of suitable motors readily available upon the open market, is fixed upon the motor slide plate 97 and a belt 104 encircles the motor pulley 103 and the pulley 94 on the drive shaft. The tension of springs 101 tend to move the slide plate 97 and motor mounted thereupon to the left as seen in FIGURE 6. These springs are calibrated to maintain a predetermined tension upon the belt 104.

Selector mechanism As will be seen best in FIGURE 8, the mechanism for moving the power unit transversely of the bed consists of a control arm 105 connected by pivot 106 to the web of channel 20. A pin 107 fixed in the lower end of arm 105 extends through a slot 107' in the Web and through a perforation in the flange 84 of the motor support 81 and is fixed thereto. Arm 105 extends upwardly from pivot 106 through a slot 108 in the flange of channel 20 and contains near its upper end a T-shaped slot 109.

A selector lever 110 is pivoted to cross member 111 of the bed by a pivot 112. A pin 113 fixed in the lower end of the lever 110 is registered in the T-slot 109. Fixed on lever 110 near the upper end thereof is a socket 114 in which the shank 115 of a selector knob 116 is telescoped and secured in convenient manner such as by a set screw.

It will be noted that the distance between the selector knob 116 and the pivot 112 is greater than the distance between that pivot and the pin 113. It will also be noticed that the distance between the T-slot 109 and the pivot 10 6 is greater than the distance between pivot 106 and the pin 107. As a result of this mechanical leverage the force required to produce a given pressure between the drive wheel 92 and the selected one of the friction wheels 45 and 50 is achieved by the application of a smaller force to the selector knob 116. When this knob is moved from the position shown in full lines in FIGURE 8 to the position shown in dotted lines therein the power unit is moved to the left as seen in FIGURE 5 and drive wheel 92 is moved into driving engagement with the friction wheel 50. Pin 113 is moved into the end of the cross portion of T-slot 109 to hold the apparatus in this position after the force is removed from the knob 116. The mechanism for moving the power unit transversely of the bed is located at the foot thereof and consequently is not readily available to a patient in the bed.

Control mechanisms To render movement of the bed, particularly the head section thereof, available to a patient, a control rod 120 best seen in FIGURES 5, 6, 7, 1'0 and 11, is journaled in the cross members 29 and 30 of the main frame of the bed for both rotational and axial movement. Fixed on the end of the rod 120 adjacent the drive shaft housing 86 is a pin 121 which projects into a slot in the bifurcated ear 122 that is bent out of the back wall member 89 of the housing. As will be seen best in FIGURE 5 when the power unit is moved to engage the drive wheel 92 with the friction Wheel 50 movement of the car 122 rotates the rod 120 through a small arc.

Limit positions setting Fixed upon the rod 120 are spaced apart hi-low limit plates 123 and 123' and head limit plates 124 and 124'. Rotation of the rod 120 occasioned by the movement of the power unit to the position shown in FIGURE 5 lowers the limit plates 124 and 124' into the path of a limit bracket 126 fixed upon the nut 75. Thus is responsive to moving the control rod 120 towards the cross member 29 results in operating the switch 127 to move nut 75 towards the cross bar 30 engagement of the bracket 126 with plate 124 will move the rod 120' in the opposite direction and thereby stop the motor.

Movement of the nut 75 in the opposite direction is stopped by the engagement of bracket 126 with stop plate 124 in a similar manner. Nut 55 on the hi-low screw shaft is equipped with a similar limit bracket which engages limit plate 123 or 123' when nut 55 approaches its limit position.

Motor control As will be seen best in FIGURE 10 a switch 127, preferably a single pole double throw snap action switch, is mounted upon the cross member 30 and preferably disposed within a suitable housing. Fixed upon the rod 120 is a collar and the operating lever of switch 127 extends into a groove in the periphery of this collar. A spring 129 encircles the rod 120 and extends between the collar 128 and the cross member 30. A similar spring 129' abuts against the cross member 29 and a pin carried upon the rod 120.

As will be seen best in FIGURES l, 3 and 13, an operate rod 130 disposed within the seat section supports 31 and 32 and terminates in operating knobs 131 located at the sides of the bed within easy reach of a patient therein. Depending from rod 130 are pivot bars 132 which extend down to and are pivotally connected to brackets 133 mounted upon the side rails of the main frame. Also fixed upon operate rod 130 and depending therefrom are a pair of levers 134 to which control rod 120 is pivotally connected. Movement of either one of the control knobs 131 from neutral in one direction moves the control rod 120 axially in a corresponding direction. This movement causes collar 128 to operate the switch 127, thereby to initiate an operation of the motor 102. It is suflicient to note here that the main spring of the switch 127 is connected to one side of a source of power and the two make contacts of the switch are connected to the two operate leads of the motor, the common lead of the motor being connected to the other side of a source of power. When the switch is operated in one direction the motor will be operated in one direction and when the switch is operated in the opposite direction the motor will be operated in the opposite direction. Through this arrangement movement of the head section of the spring frame is under the control of a patient in the bed.

T rendelenberg positions There are times when the treatment of the patient in the bed requires that the spring frame be put in one or the other of the Trendelenberg positions, that is with the spring frame flat and with one end of it lower than the other end. To permit placing the spring frame in these positions as will be best seen in FIGURES 1 and 3, knobbed shafts 135 and 135 are journaled in the web of channel 20 and carry at their inner ends cams 136 and 136'. A tie rod 137 connects together these two cams. When it is desired to maintain the foot end of the bed elevated while the head end thereof is lowered, the hi-low mechanism is operated to raise the bed to its upper limit position. Knobs 135 or 135' are then operated to position the tongue of the cams 136 and 136 into the paths of legs 18' and 19' at the foot end of the bed. The hi-low mechanism is then operated to lower the bed and when the tongues on the cams engage the upper ends of the legs further downward movement of the foot end of the bed is prevented. Further operation of the hi-low mechanism to lower the head end of the bed removes tension from the cables 65 and 66 which are connected to the foot end of the bed.

Cable slack prevention As will be seen best in FIGURES l and 12, unwanted slack in the cables 65 and 66 is prevented. As will be seen best in FIGURE 12, each of the flanges of catch plates 56 and 57 contain a rectangular opening 140 into which project latch springs 141, fixed upon the guide 40. Since the tension on cables 65 and 66 has been removed these springs hold the catch plate 57 against movement in the guide 40. Tension still being on cables 58 and 59, catch plate 56 is held in contact with the nut 55.

When the spring frame of the bed is being restored to horizontal position as the nut 55 reaches its upper limit position, the tongues on cams 136 and 136' are out of engagement with the tops of the legs 18 and 19' and a spring 138 extending between the guide rod 137 and the cam 136 restores the cams to their normal position.

In order to permit holding the head end of the bed elevated while the foot end thereof is lowered, the mechanism just described is duplicated in the channel 13 at the head end of the bed and operated by knobs 139 and 139' in the foregoing manner.

Automatic knee elevating To eliminate the tendency of a patient in the bed to gravitate towards the foot end when the head section of the spring frame is elevated, the bed is equipped with mechanism for automatically elevating the knee ioint of the spring frame as the head section thereof is being elevated.

As will be seen best in FIGURE 14, this mechanism consists of a pair of crank arms fixed upon the cross tube 70 and between which a tie bar 151 is pivotally connected. Fixed to the thigh section of the spring frame is a cross tube 152 to which a crank arm 153 is fixed. A pair of links 154 are pivotally connected to the crank arm 152 and also to the tie bar 151.

A cross tube 155 journaled in the main frame and LX- tending between side rail sections 23 and 26 thereof is equipped with L-shaped bars 156 which journal it in the main frame and form handles for rotating the tube around its axis. Fixed to the cross tube 155 are a pair of support arms 157 between which a roller 159 is journaled. Tie bar 151 extends between the support arms 157 and rests upon the roller 159 when the mechanism is set for automatic knee elevation.

As will be seen in FIGURE 14 when the sections of the spring frame are horizontal the mechanism is in the position shown in dotted lines in this figure. It will be noted that the links 154 are disposed at an acute angle to the tie bar 157, this angle being approximately 30. As the head elevating mechanism is operated, this angle increases and when the spring frame of section 33 is in fully elevated position in which it is shown in full lines in this figure, the angle between the links 154 and the tie rod 151 is slightly greater than a right angle, namely an obtuse angle. The shape of the tie bar 151 and length of the links 154 and length of the support arms 157 are proportioned so that when the head section 33 is in fully elevated position the elevation of the knee joint between the thigh and foot sections is not sufficient to result in an undesired elevation of the knee.

In the event that it is desired that the thigh section remain horizontal while the head section 33 is being elevated, cross tube 155 is rotated clockwise as seen in FIGURE 14 away from stop brackets 158 into the position shown in dotted lines in this figure. The distal end of tie bar 151 is then supported by the links 154 and during movement of the tie bar as the head section 33 is being elevated, links 154 swing on their pivots and the thigh section 35 of the spring frame remains horizontal being supported by the engagement of the feet 152 with the side rails 23 and 26 of the main frame 10.

Manual elevation of knee hinge There may be times when treatment of the patient in the bed requires elevating the thigh and leg sections of the spring frame and the bed is equipped with the usual manual means for accomplishing this purpose. As will be seen in FIGURE 15 the cross tube 160 on the thigh section of the spring frame carries a pair of crank arms 161 between which a tube 163 is positioned and pivotally connected to the crank arms by a pin 162 which projects through an elongated slot 164 in the tube. A nut 165 is fixed in the end of the tube 163 and threaded upon a screw shaft 166 that is journaled in brackets attached to the channel 20 at the foot end of the bed. The usual foot levelizer 167 is pivotally connected to the foot end of the foot section 36 of the spring frame and the cross member 30 is engaged in a notch in this levelizer to hold the foot section in horizontal position. It will be noted that since the pin 162 projects into and through slot 164 and the tube 163 the thigh section of the spring frame can be elevated by the automatic knee elevating mechanism notwithstanding that the manual mechanism is not operated.

Covers To guard against the entrance of lint or other extraneous material into the operating mechanisms of the bed, a power unit cover 170 is employed to protect the power unit, a cover 171 to protect the limit position control mechanisms, a cover 172 best seen in FIGURES 8 and 15 to cover the selector mechanisms and covers 173 over each of the sheaths by which the cables are conducted into the posts of the bed. The foot board 21 aids in covering the selector mechanisms and covers the mechanism disposed within the channel 20.

Lockout There may be times when the attending physician desires to have the head section of the spring frame and the hi-low mechanism disabled so that the bed must remain in a position in which it has been set notwithstanding that the patient may try to alter this position.

As will be seen in FIGURES 8 and 9, fixed in the cover 172 are lock bars 175 and 176, each of which is journaled in the top edge of the cover and equipped with a knob disposed thereabove. When the bed has been set in a desired position and the selector mechanism moved to its neutral or middle position, the lock bars 175 and 176 may be rotated into the path of the socket 114 engaging that socket to prevent movement of the selector mechanism in either direction. Should the patient in the bed move the operate rod 130 out of its neutral position, the motor may be started but the mechanisms of the bed will not be operated since the drive wheel is in neutral position and not engaging either of the friction wheels.

From the foregoing it will be apparent that the bed of the present invention lends itself to use by ambulatory patients requiring a minimum of nursing care. The bed can be used in locations where manually operated beds are now commonly used because of their lower cost. Since positioning of the head section of the spring frame is controlled by the patient, less care by hospital personnel is required by this bed than is required with manual beds. My improved bed is capable of being placed in all positions that may be required in the treatment of patients. The power unit, including the friction drive, is of simple construction and is thoroughly reliable in operation. The placing of the selector at the foot end of the bed renders it inaccessible to a patient in the bed and simplifies the structure of the bed. Automatically established limit positions guard the mechanisms from being damaged during operations. Protective covers prevent the entrance of lint and the like into the operating mechanisms of the bed to insure long trouble free service of the bed.

What is claimed is:

1. In a hi-low hospital bed having a main frame supported by legs telescoped into posts on the frame and having supported thereon the usual spring frame having head, seat, thigh and foot sections pivotally connected together, said bed having manual means for elevating the thigh and foot sections and having journaled in the main frame a pair of screw shafts spaced apart and parallel to each other, one of said shafts for operating the hi-low mechanism and the other operating the mechanism for raising and lowering the head section of the spring frame; the improvement comprising:

(a) a pair of friction wheels, one attached to each of said screw shafts;

(b) a power unit, including an electric motor, a drive shaft upon which a drive wheel is mounted and disposed between said friction wheels, and a belt for establishing a driving connection between said motor and shaft;

(c) means for selectively moving said power unit transversely of the bed from a central position to engage said drive wheel with said friction wheels, one at a time, to establish driving connections therebetween;

(d) control means for starting and stopping said motor;

(e) and means connecting together said head and thigh sections of the spring frame to enable movements of the head section to effect corresponding move ments of the thigh section.

2. A hospital bed as specified in claim 1 in which the main frame includes a channel, fixed to and extending between the posts at the foot end of the bed, disposed with its web innermost and in which the friction wheels and drive wheel are disposed within said channel.

3. A hospital bed as specified in claim 2 on which the power unit comprises a motor support mounted for translatory movement transversely of the bed by means engaging the web of said channel and a cross member of the main frame spaced from said web, a drive shaft housing comprising a front member mounted on said web for translatory movements transversely of the bed, a back member fixed upon and spaced from said front member, a thrust bearing in each of said members in which bearings the drive shaft is journaled, a pulley fixed on said shaft between said bearings, means connecting together said motor support and said drive shaft housing, a motor slide plate mounted upon said motor support for movement transversely of the bed upon which plate the electric motor is fixed, a belt encircling said pulley and a pulley on the shaft of the motor, and spring means for urging said slide. plate away from said shaft housing to maintain a predetermined tension on said belt.

4. A hospital bed as specified in claim 3 in which the means for mounting the motor support and front member of the drive shaft housing consists of low friction bushings fixed upon said members and extending through slots in said web and the cross member of the frame.

5. A hospital bed as specified in claim 4 in which the means for selectively moving the power unit consists of a control arm pivoted to the web of the channel and eX- tending through a slot in the upper flange of the channel, a pin fixed in said arm adjacent its lower end and extending through a slot in said web to the motor support to which the pin is fixed; a selector lever pivotally mounted on a cross member of the frame disposed above said channel and extending above said pivot to a selector knob, a pin fixed in the lower end of said lever and extending through a T-shape slot in the upper end of said control arm, said pin moving into one end of the cross portion of said T-slot to maintain the power unit in the operative position in which it has been set by rotation of said arm and lever about their respective pivots.

6. A hospital bed as specified in claim 5 in which there are a pair of lock bars, each of which is engageable with the selector lever to prevent movement of that lever in one direction from a neutral position of the lever.

7. A hospital bed as specified in claim 6 in which the distance between the selector knob and the pivot of said selector lever is greater than the distance between said pivot and the pin at the lower end of the lever and in which the distance between the. T-slot in and the pivot of the control arm is greater than the distance between that pivot and the motor support pin, so that a given operating p1 essure applied to the selector knob to move the mechanism into operating position produces a greater pressure between the driving and friction wheels.

8. A hospital bed as specified in claim 1 in which the control means includes a control rod journaled in cross members of the frame for rotary and axial movements, a pin fixed on said rod and engaged in a slot in the power unit to rotate the rod as the power unit is moved by the moving means; plates fixed upon said rod and moved by rotation thereof into the path of a nut on the screw shaft selected by said movement of the power unit, to determine limit positions for said nut; an electric switch; a collar on said rod engaging the operating lever of said switch; means for moving said rod axially from neutral in either of two directions and thereby operate said switch to start the motor, engagement of the nut with one of said plates moving the rod axially in the opposite direction to stop the motor.

9. A hospital bed as specified in claim 8 in which the means for moving the control rod axially comprises an operate rod pivotally mounted on said main frame beneath the seat section of the spring frame which rod extends upwardly at the ends of the seat section and terminates in operate knobs readily accessible to a patient in the bed; a pair of levers fixed on said operate rod and pivotally connected to said control rod so that movement of the operate rod around its pivots moves the control rod axially, and spring means surrounding said control rod for returning said rods to a normal position when pressure on the operate knobs is removed.

10. A hospital bed as specified in claim 1 in which the main frame contains side rails composed of rectangular tubing, each of which rails has end sections extending inwardly from each post at an acute angle to the longitudinal median line of the frame and merge into a central section that is parallel to said median line; a sheave journaled in each end section of the rail and extending into the associated post, there being a perforation in the rail at each junction of the ends and middle sections thereof through which perforations the cables of the hi-low mechanisms of the bed enter the end sections of the rail and extend around said sheaves into a space between the posts and legs telescoped therein to a point of attachment at the tops of the legs to support the frame upon the legs.

11. A hospital bed as specified in claim 1 in which the hi-low mechanism includes a nut threaded upon the screw shaft and containing four holes, the axes of which are parallel to the axis of the shaft; a pair of channel shaped catch plates, each having a web abutted against the end of the nut and containing perforations coinciding a pair of holes in the nut; a perforated flange at each end of each catch plate; a pair of cables attached to one of said plates and extending through the holes in the nut to the legs at the head end of the bed to which they are attached; a second pair of cables attached to the other plate and extending through the holes in the nut to the legs at the foot end of the bed to which they are attached; cam means in the end structure at each end of the bed adapted to engage the ends of the legs when the bed is in elevated position to retain the end of the bed in that position; latch springs engaged in the perforations in the flanges of the catch plates to hold the plate associated with the retained end of the bed against movement as the nut is moved to lower the other end of the bed to place the spring frame in position inclined with respect to horizontal.

12. A hospital bed as specified in claim 1 in which the mechanism for raising and lowering the head section of the spring frame includes a cross tube fixed on the head section near the pivotal connection thereof to the seat section; a crank arm fixed upon said cross tube; a tie bar pivotally connected to said crank arm and extending towards the foot of the bed; a roller upon which said tie bar rests; a cross tube fixed upon the thigh section of the spring frame; a crank arm fixed upon said latter cross tube, link means pivotally connected to said latter crank arm and to the distal end of said tie bar and disposed at an acute angle to said tie bar when the head section of the spring frame is in horizontal position, operation of said mechanism to elevate said head section moving said tie bar over said roller and increasing said angle through a right angle into an obtuse angle to elevate the thigh section and thereby prevent a patient in the bed from gravitating towards the foot when the head section is in elevated position.

13. A hospital bed as specified in claim 12 in which the roller is journaled between support arms fixed upon a cross tube that is journaled in the main frame of the bed, which tube can be rotated to disengage the roller from said tie rod when it is desired to have the thigh section of the spring frame remain in horizontal position when the head section is in elevated position.

References Cited UNITED STATES PATENTS 3,211,014 10/1965 Sanderson 74202 3,216,026 11/1965 Mann 566 3,237,212 3/1966 Hillenbrand et al. 5-63 X 3,256,534 6/1966 Benoit et a1 5-66 3,278,952 10/1966 Holm 566 X 3,345,107 10/1967 Homier et al. 297410 3,375,740 4/1968 Bottum 74202 X CASMIR A. NUNBERG, Primary Examiner.

U.S. Cl. X.R.

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