JPS6219866B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to hospital beds. This type of bed usually has devices that allow the patient to sit up or down and to move the patient's upper body to a sitting position or to articulate the patient's thighs upward. It is. To perform this operation, most hospital beds include a base support frame, a main frame, and a mattress frame. Often the main frame supports a motor to move the main frame vertically relative to the base frame and to pivot the head or lower portion of the pinerest frame. The three separate frames are thus in a favorable condition for performing the necessary operations.

Despite having these three horizontal frames, existing hospital beds have some drawbacks. First, these frames have poor maneuverability due to their length and weight, are expensive to attach to additional equipment and assemblies, and have unnecessarily complex operating linkages.

In order to overcome the disadvantages of the conventional technology, the hospital bed of the present invention has a main frame and a mattress. frame and has two frames.
The main frame is supported off the floor by parallelogram links or four-bar links, and supports a power drive motor and linkage to effect the movement of the bed as required. There is. Additionally, the main frame incorporates locking devices to maintain selected four-bar links in the raised position.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hospital bed that has only two frame mechanisms but is capable of the same movements and positioning that can be achieved by a bed with three frame mechanisms. It is.

Another object of the present invention is to provide a hospital bed which is equipped with a four-bar linkage main frame lifting support mechanism mounted on casters, and which allows the bed to be raised and lowered with minimal force. be. A simple direct power drive and linkage mechanism is provided to accomplish this operation.

Yet another object of the present invention is to provide a hospital bed with a shortened wheelbase for improved maneuverability.

Yet another object of the present invention is to provide a durable and inexpensive hospital bed having a simple fixation device.

The invention will be explained in more detail below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the preferred embodiment of the present invention has transverse beams 14, 14 at their ends.
Two elongated frame members 12, 1 connected to
It has a supporting main frame 10 consisting of two parts.
Two vertical members 16 are fixed to the transverse beam, and these vertical members are connected to brackets 22, 22.
The head plate 18 and foot plate 20 are attached through them.

Extending outwardly and upwardly from opposite sides of the main frame 10 are two support arms 24, 24, one of which is attached to each frame member 12. These support arms pivotally connect the pinerest frame 26, which includes a head 28, a thigh 36, and a foot 40. The head 28 consists of a U-shaped frame whose ends are pivotally connected to the support arm 24 at sections 29, 29, the upper end of which is horizontally supported by a vertical support 30 resting on the frame member 12. It is supported vertically so that it can take any position. Also, the U-shaped head 28
A torque tube 32 is mounted near the end of the shaft in a manner to be described later, and the pivot connection points 29,
The head 28 is allowed to pivot clockwise about the center 29.

Also, the support arm 24 on the opposite side of the bed,
24 includes a rectangular thigh portion 36 of the pinerest frame 26 at pivot points 34, 34;
is installed. Supplemented to this pinerest frame is a rectangular foot 40 having a U-shaped structure, and an arm extending from the foot is pivotally connected to the opposite thigh 36 at portions 42, 42. ing. Supporting the thigh 36 and foot 40 in a horizontal position are vertical supports 44 and 50 secured to opposite ends of the foot 40. Support 4
4 includes a U-shaped bar with an arm depending downwardly from the opposite side of the foot 40 for connection to a bar 46 which rests on a cross bar 48 extending between the main frame members 12,12. May contain. Added to the distal end of the foot 40 is a vertical support 50 that is attached directly to the frame member 12.

As is well known in the art, rotating the torque tube 38 counterclockwise causes the thigh 36 to
can be pivoted upward about the pivot point 34, simultaneously raising the anterior end of the foot 40, which
6 and foot 40 articulate at pivot points 42,42. The ends of the foot 40 remain supported on the main frame member 12 via supports 50, but these members can reciprocate along the frame toward the head end of the bed.
Alternatively, a ring mechanism (not shown) may be installed at the foot end of the bed, as is also well known in the art.
may be secured such that the end can be raised relative to the joint or supported in a raised position as shown in FIG.

Before discussing the drive mechanisms for controlling the individual movements of the pinerest sections, we will discuss the leg assemblies 60 that raise and support the main frame. These leg assemblies raise and lower the bed. These assemblies consist of a main frame member 12 and a single spindle shaft 6.
A parallelogram or four-bar link 62 is incorporated between the caster wheel 64 and the caster wheel 64 having a diameter of 5.

Referring to FIG. 3, the four-bar link includes a trunnion block 66 secured to and depending from each main frame member 12. These trunnion blocks have two torque tubes 68 and 70 rotatably journalled extending across the main frame 10, each of which has a rod or shaft rotatably pressed therewith. Links 72 and 7
4 is installed. A vertical link 78 is pivotally connected to the opposite end of each set of rods 72 and 74. A pair of links 78 near the head and foot ends of the bed are secured to the next transverse tube 76. The outer end of each transverse tube is provided with a journal portion for receiving a spindle shaft 65 of a caster 64. The weight of the bed and patient is 4
It is supported by a linkage 62 that communicates with vertical links 78. These links 78 then transfer the weight to the intermediate portion of the laterally extending transverse tube 76. The weight passes through this transverse tube to the caster 6 located at the outer end of the transverse tube.
4. The transverse tube 76 has a length sized such that the caster 64 extends outwardly of the main frame members 12, 12 and beyond the bar linkages 72,74. Since the casters are installed so as to protrude outward from the main frame and the four-bar link, the weight transmitted to the floor through the casters can provide stable support to the entire bed structure. Accordingly, the stability normally achieved by using a base frame supported above the floor by casters and then supporting the main bed frame, as in the past, is not achieved with the present invention. It can be obtained even if the frame is completely removed.

Referring to FIG. 4, a counterclockwise directed force exerted on tube 70 causes link 74 to
(which is constrained to rotate with tube 70) begins rotational movement about its pivot point with vertical link 78. Simultaneously, the tubes 70 rotate counterclockwise at each end of the bed so that the main frame member 12 is raised to the raised position shown in FIG. Furthermore, trunnion 66, rod 7
A four-bar linkage 62 consisting of shafts 2 and 74 and a vertical link 78 maintains vertical alignment of caster wheels 64 and their spindle axes 65. As already explained, by adopting this link mechanism, the third bed
The supporting frame can be removed.

Furthermore, the drive mechanism for raising and lowering the bed can be simplified. The simple drive mechanism of this structure will be explained in detail with reference to FIGS. 2 and 4. As shown therein, vertical movement of the main frame member 12 is accomplished by rotation of the lower torque tube 70. This is made possible by welding two laterally spaced, generally L-shaped lever arms 80 to each lower torque tube 70. The free ends of these lever arms are pivotally connected to the depending flanges of a reciprocating U-shaped drive channel member 82 by cross pins 84, which pins 84 are elongated at opposite ends of the reciprocating channel member 82. Hole 8
It extends into 6. Referring to FIGS. 2 and 4, as the reciprocating groove member 82 moves to the left, the pin 84 also moves to the left, rotating the lever arm 80 and torque tube 70, thereby lifting the bed. The force that causes the driving groove member 82 to reciprocate is
2 by a motor 88 mounted on and moving therewith. The motor 88 may be attached to a flange depending from the channel member 82 or by any suitable means. A threaded output shaft 92 extends from the motor 88 along the groove member 82 and into a threaded nut 94 which acts as a stop member. The nut 94 is restrained from reciprocating movement by a tie rod 96 which is connected between the end beam 14 and a flange extending from the locking nut. The rotational force from motor 88 thus causes drive shaft 92 to threadably engage nut 94.
Further, the motor 88 and the groove member 82 are moved to the left, and the lever arm is moved counterclockwise to raise the bed. By rotating the motor 88 and the output shaft 92 in opposite directions, the output shaft 92 inside the nut 94 is unscrewed, and the lever arm 86 is rotated clockwise to move the bed under gravity. so that it can be lowered. In this way, the groove members 82 and 4, which are simple drive mechanisms,
The bar linkage allows the apparatus of embodiments of the invention to be raised and lowered, and the main frame to move vertically.

Hospital beds are sometimes required to assume either a forward-tilt position or a reverse-tilt position as shown in FIG. To assume these positions, the entire main frame 10 is raised to its maximum height by motor 88. and a locking device 120 mounted on one of the four-bar linkages is engaged;
The motor is reversed. Therefore, if the fixing device attached to the foot of the bed is engaged at the elevated position of the frame, then by reversing the motor, only the head of the bed will be lowered to create a positive tilting condition. . Alternatively, a reverse tilting condition is created when a locking device on the opposite side of the previous locking position is engaged. As shown in FIG. 2, the bed can be released from any of the tilted conditions described above by raising the bed to its maximum height and releasing the locking mechanism.

The fixation device 120 will be described in detail with reference to FIGS. 5-8. This device uses torque tube 68
and 70. The fixation device consists of a vertical support member 122 having a semi-circular recess at each end for insertion between the torque tubes 68 and 70. To facilitate the insertion operation, a removable fixing plate 124 is provided at the upper end, which is bolted at intervals along the outer circumference of the torque tube 68, as shown in FIG.
may be provided. Alternatively, the fixing plate 124 may be provided at the lower end. The support member is preferably comprised of a tubular, rigid rod for strength, and flanges 126 are secured to the bottom of the support member and are disposed laterally to prevent lateral movement of the torque tube. Preferably, it is positioned between levers 80.

The support member 122 has a point 127 near its upper end.
A fixed rod 128 is pivotally connected to. The fixing rod 128 is U-shaped for strength.
Preferably, a semicircular recess is provided at the opposite end. The upper recess 130 is for engaging the upper torque tube 68, while the lower recess 132 is for selectively engaging a pin 134 extending between and coupled to the two lever arms 80. can be matched. 5 and 7, the leg assembly is shown in the raised position with lever arm 80 rotated fully counterclockwise. To lower the main frame member 12, the lever arm 80 must be able to rotate clockwise, allowing the drive rod 82 to reciprocate to the right.
As shown in FIG. 5, there is nothing blocking this clockwise movement, so the bed can be lowered. However, in order to effect forward or reverse tilting (as an example is shown in FIG. 2), one of the leg assemblies must be held in the raised position. This is achieved by preventing the lever arm 80 attached to one of the leg assemblies 60 from descending or rotating clockwise. The left leg assembly is now in an operative state assuming the reverse tilt position shown in FIG.

In a preferred embodiment of the invention, the clockwise downward movement of the lever arm 80
28 into the passageway of the pin 134, which is subjected to compression between itself and the torque tube 68, and a rigid strut to hold one end of the bed in the raised position. act as a

Movement of the fixed rod 128 is effected by an L-shaped actuation plate 136 pivotally connected on the support member 122. Actuation of this member places the locking rod in the "ready" position.

As shown in FIGS. 5 and 6, the fixing rod 12
8 is provided with an elastic tip 138. This chip is constructed from a synthetic resin such as "Delrin" or other suitable synthetic resin. "Delrin" is a registered trademark used for DuPont products.

The actuating plate 136 rotates so that the left end of the actuating plate faces upward (see FIGS. 5 and 6), and the fixing rod 12
8 and the free end of this locking rod is moved upwardly to place tip 138 into the path of pin 134.
This is the "ready" position.

The actuation plate 136 is rotated by a push-pull lever 142 that extends through the foot end 14 (see FIGS. 2 and 4) of the main frame for easy access by hospital attendants. Fixed rod 12
A tension spring 144 is connected between the actuating plate 136 and the fixing rod 12.
8 acts to hold the pin 134 in the locked or fixed position before it engages with the pin 134. Actuation plate 13
The free end of 6 engages the edge 140 of tip 138 in this position. The tension in the spring is of sufficient strength to hold the member in place until the pin 134 modulates, as will be explained later (see FIG. 6).

It should be noted that in the "ready" position, only the resilient tip 138 of the locking rod is in the path of the pin 134. This allows the attendant at the hospital to choose between the normal tilt position and the reverse tilt position, regardless of how high the bed is raised. If the bed is in any position other than the fully raised position, the bed must be adjusted to the fully raised position to begin the movement to take the required forward or reverse tilt position. There must be. Such movement causes pin 134 to move counterclockwise across its path. If one of the tips 138 of the fixing rods were to be moved forward to the ready position as shown in FIG. be. The fixed rod has an operating plate 136 with a tip 138.
is held in the ready position by engaging the edges 140 of. The upward movement of the bed is thus adjusted in such a way that this bed assumes a fully raised position, without interfering with the operation of pre-adjusting one or the other of the fixing members to the ready position. Allows movement into position.

As the bed moves downward, pin 134 moves clockwise and engages the underside of tip 138. Continued movement of the pin causes the locking rod to rise against the action of spring 144 and to release actuating plate 136 from edge 140. The actuation plate 136 is rotated counterclockwise by the force of the spring and moved to the normal neutral position (FIG. 5).

As pin 134 moves counterclockwise, it pivots locking rod 128 counterclockwise until recess 132 engages the pin and recess 130 engages torque tube 68. The locking rod is thus compressed tightly between pin 134 and tube 68, attaching the four-bar linkage to one end of the bed. By continuing to operate the motor 88, the other end of the bed can be continuously moved downward to assume a required tilt position between a normal tilt position and a reverse tilt position.

L-shaped link 80 attached to the end of the bed when securing one or the other four-bar linkage
to secure it in place. The opposite end of the bed is lowered by operating the drive groove member 88.
Movement of the drive groove member 88 is absorbed by the "slip motion" between the L-shaped link 80 and the groove member 82. Pin 84 is positioned within slot 86. As the groove member moves downwardly, lowering one end of the bed, pin 84, which is attached to link 80 at the fixed end of the bed, becomes fixed. Pin 84 slides within slot 86 in channel member 82 and absorbs movement of the channel member.

After being placed in the positive or reverse tilt position, the bed can be returned to its normal horizontal position by activating motor 88 and raising the bed to its maximum height position. spring 144
The pressing action causes the fixing rod 128 to retreat from its locking position.

In addition to tilting the bed by raising and lowering it, the head 28 and thigh 36 can be pivoted about the support arm 24 (see Figures 1 and 2). . Two lever arms 160 are mounted on the torque tube 32 and restrained for rotation therewith in order to pivot the head 28 about the pivot points 29,29. Threaded output shaft 16 of motor 166 suspended by suitable means from transverse support rod 48
A threaded nut 162 telescopically moved by 4 drives these lever members.

Similarly, the thigh 36 is connected to another motor 1.
70 to advance and retract the threaded nut 174 through its threaded drive shaft 172 allows for pivoting about the pivot points 34, 34. This drive shaft is connected to a lever arm restrained by a torque tube 38.

The members controlling the operation of the three motors 88, 166, 170 are either fixedly connected to the foot of the bed or mounted on the support arm 24 so as to be accessible to the patient.

In the embodiment shown in FIGS. 1 to 12,
The footboard and headboard of the bed are removably attached. At the outer end of the bed transverse beams 14,1
4, a vertical tubular member 216 is secured.
Bracket 22 defines an elongated hole in which tubular member 21 is received. The headboard and footboard can be removed by vertically lifting the bracket 22 to slide it off the tubular member 21.

Alternatively, the bed may be operated via a manual drive as shown in FIGS. 9-12. This bed has a substantially similar main frame member 12 and a mattress frame 2 with a four-bar linkage 62 for raising the bed.
6. However, the drive linkage for moving the pinerest and for moving the lift link is different.

In this embodiment, lever arm 80 is connected by a pair of parallel links 214.
Link 214 has a slot 286 at each end thereof to receive a transverse pin 284 attached to a set of links 80.

Link 214 has an extendable drive rod 210 pivotally connected at section 285 near link 80, which is mounted at the head end of the four-bar linkage. At its opposite end, the drive rod is provided with a drive nut 287. A driving screw member 289 is journalled inside a hemispherical thrust bearing 291 on the main frame. The threaded member is in operative engagement with the nut 287, and rotation of the threaded member advances or retracts the drive rod relative to the threaded member depending on the direction of rotation. Although not shown in the figures, the connection to the main frame may include a pivot connection as necessary to allow upward movement of the main frame and thus transform the angle between drive rod 210 and threaded member 289. It has been done well.

The drive screw member is typically rotated by a hand crank or handle 200 that is partially recessed within the foot plate 202, as shown in FIG. The handle is driven by a threaded member 2 by a telescoping linkage 204 that is partially retractable into the headboard when the handle is not in use.
89. The telescoping linkage includes a shaft 292 connected to a threaded member 289 via a universal joint 206. Shaft 292 is square shaped and has a free end telescopically received within a tube 293 attached to crank 200. The tube is also rectangular in shape and has a driving relationship due to the coupling relationship between the square end of the shaft 292 and the tube 293. This is done by a sliding engagement. Tube 293 is
It can be pulled out from the shaft to allow for removal of the footplate, as will be explained later. In this embodiment, the operation of raising the knee portion and the operation of raising the head can also be performed manually. A similar crank with a telescoping coupling 204 is provided.

The head 28 is similarly pivotally connected by a crank 216 and an extendable link 218 which, via a universal joint 219, extends a threaded telescoping rod 220 which drives a lever arm 160. or withdraw.
Similarly, the lever arm 176 of the thigh 36 is
Telescoping rod 2 driven by handle 236 via link 232 and universal joint 234
30. These manually operated linkages can be modified in various forms in the art.

Crank 20 to raise the main frame
0 is rotated, and the driving screw member 289 is rotated. This causes the nut 287 to move and the driving tubular member 210 to extend. The resulting force forces link 214 toward the head end of the bed and moves lever arm 80 counterclockwise. This movement actuates a lever arm attached to the cross bar and caster assembly to raise the platform supporting the patient. Lowering the bed is accomplished by turning the hand crank in the opposite direction.

The embodiment of FIGS. 10-12 incorporates the forward and reverse tilt mechanisms of FIGS. 5-8. These embodiments operate in a similar manner as previously described. Slot 286 connects pin 284 and link 214
Make the necessary movements between the two.

A modified example of the elevating link mechanism composed of four rods is shown in FIGS. 13 and 14. Rather than employing separate link members, torque tubes 68 and 70 extend through trunnion 69 and connect spindle shaft 65 of caster 64.
The torque tubes 68, 70 may be bent 90 degrees to form a parallel link 250 that is directly attached to the housing 252 that receives the torque tubes 68, 70. The attachment between housing 252 and link 250 may be provided by a pivot pin that passes through these members and allows for angular movement of link 250 relative to housing 252.

It should also be noted that the casters supporting the bed on the floor are spaced outwardly from the main frame. This provides maximum stability to the bed even when loads are applied towards the edges of the patient support surface. In this embodiment, the caster can be moved to a specific position relative to the floor by adjusting the extension of the torque tube from the trunnion 66. In this embodiment it is also possible to remove the transverse connections between the casters in order to further improve the cleaning operation.

In this embodiment the head plate and foot plate are secured to the main frame by slightly modified means.
Each of the tubular members 221 includes a flat plate 225 facing outwardly from the bed. The bracket 222 attached to the head plate and the foot plate is the plate 22
5 includes a curved groove 223 that slidably receives the groove. A stopper 229 is provided above each bracket to prevent further downward movement of the bracket and to fix the position of the head plate and foot plate. By adopting such a configuration, spare devices such as IV rods or the like placed inside the vertical tubular member 21 do not need to be removed in order to remove the head plate or foot plate. .

Other modifications are possible within the scope of the invention. For example, the structure of the four-bar linkage mechanism may be changed, and various forms of the fixing device 120 for allowing the bed to assume a forward tilted position or a reverse tilted position may be considered.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a preferred embodiment of the invention. FIG. 2 is a side cross-sectional view taken along line 2--2 of FIG. FIG. 3 is a side view showing the bed of FIG. 1 in a raised position. Figure 4 shows
Figure 4 is a view similar to Figure 3 with the bed in the lowered position and the mattress frame pivoted; 5, 6 and 7 are side views of the fixing member. FIG. 8 is a front view of the member of FIGS. 5-7. FIG. 9 is a plan view of another embodiment of the invention. Figure 10 is line 10 in Figure 9.
FIG. Figure 11 shows
10 is a side view showing the bed of FIG. 9 in a raised position; FIG. FIG. 12 is a front view of the front plate of the bed shown in FIGS. 9-11. 13th
The figure is a perspective view showing a modified example of the leg link of the present invention. FIG. 14 is a plan view of FIG. 13 viewed from above. Explanation of symbols, 10: Main frame, 62: 4-bar link, 24: Support frame, 64: Caster wheel, 28: Head, 70: Torque tube,
36: Thigh, 80: Lever arm, 60: Leg assembly, 82: Groove member.

Claims (1)

[Scope of Claims] 1. A hospital bed comprising a main frame, a pinerest frame supported by the main frame, and wheels connected to each end of the bed by at least one parallelogram linkage. has
a leg assembly supporting each end of the bed, the parallelogram linkage comprising: a mounting body depending downwardly from the main frame; a vertical member extending upwardly from the wheel; two pivotable parallel bars interconnecting the body and the vertical member; and at least one of the parallel bars is adapted to raise the end of the bed relative to the wheel. A hospital bed comprising a lever member connected to the parallel bars for pivoting movement relative to the mount. 2. A hospital bed according to claim 1, wherein the respective leg assemblies at each end of the bed are connected to each other to simultaneously raise the mattress frame in parallel. 3. A hospital bed according to claim 2, wherein said assembly is connected by an elongated reciprocating drive rod attached to said lever member. 4. An electric motor is mounted on the elongated drive rod, and is connected to the main frame for reciprocating the drive rod to pivot the lever member and raise or lower the bed. 4. The hospital bed according to claim 3, further comprising a driving member connected therebetween. 5. A hospital bed according to claim 2, wherein said lever member is rotatable by a manual crank having a telescoping threaded shaft connected to said lever member. 6. a threaded nut secured against reciprocating motion; and a threaded output shaft, the threaded nut being fixed from the motor to the drive rod for reciprocating the output shaft, motor, and drive rod to rotate the parallel bars. Claim 4, wherein said drive member includes: an output shaft extending into said drive member;
Hospital beds as described in Section 1. 7 The leg assembly is provided with a fixing member for independently fixing the parallelogram link mechanism when the end of the bed joined thereto is in the raised position, and a fixing member is provided on the drive rod for independently fixing the parallelogram link mechanism. is for allowing the drive rod to move relative to the fixed parallelogram linkage so that the unfixed end of the bed is lowered as the drive rod reciprocates; 4. A hospital bed according to claim 3, further comprising a member movably coupled to said lever member. 8 The above mounting body includes a trunnion, a block,
2. A hospital bed according to claim 1, further comprising a journalled torque tube to which said two parallel bars are attached. 9. A hospital bed according to claim 8, wherein each of the torque tubes has two sets of parallel bars attached at opposite ends thereof. 10. A hospital bed according to claim 1, wherein said wheel is a caster wheel having a spindle mounted in a cross bar to which said vertical member is mounted. 11 Rectangular main frame; Pine tress frame having a head area and a thigh area; In order to support the main frame above the floor level and to raise and lower the main frame, the main frame a parallelogram linkage provided at each end of the main frame; and a drive member coupled to the main frame and connected to the parallelogram linkage for raising and lowering the main frame; A hospital bed. 12. The hospital bed according to claim 11, wherein the parallelogram link mechanism is attached to wheels with casters. 13. The hospital bed of claim 11, wherein said drive member includes a lever arm attached to said parallelogram linkage for raising and lowering said bed. 14. The lever arm of claim 13, wherein the lever arm attached to the parallelogram linkage at each end of the main frame is connected by a conventional reciprocatable drive rod. Hospital bed. 15. Each parallelogram linkage is provided with a locking member for effectively fixing one of the linkages in the raised position, and the drive rod is
15. A hospital bed as claimed in claim 14, characterized in that the bed is movably coupled to the linkage to permit lowering movement of the unsecured linkage. 16. Claim 14, further comprising a manual crank drive member for reciprocating the drive rod and rotating the lever.
Hospital beds as described in Section 1. 17. A main frame having two spaced frame members, a pine tress frame supported on the main frame, and a leg assembly for raising and lowering the main frame; The leg assembly includes: a trunnion block secured to each of the frame members; two torque tubes extending between and journalled to the trunnion blocks; and a torque tube attached at an approximately 90 degree angle to the torque tube. two parallel bars mounted and pressed to rotate with the torque tube; on the wheel parallel to a plane passing through the central axis of the torque tube pivoted to the two parallel bars; A hospital bed comprising: an attached vertical link; and a drive member for rotating the torque tube to raise and lower the bed. 18. The hospital bed of claim 17, wherein the leg assembly includes a locking device for preventing downward movement of the leg assembly. 19. Claim 1, wherein said fixation device includes a support platform selectively movable within a downwardly directed path of said leg assembly.
The hospital bed described in item 8. 20. The hospital bed of claim 19, wherein said support platform is movable into the path of said drive member to prevent lowering of said leg assembly.