Tilt Bed

Abstract

A bed is provided having a movable frame for supporting a mattress and supported above a relatively fixed base by means of first and second link sets which permit the movable frame to be adjusted relative to the base. The link sets are so arranged that when the movable frame is in its uppermost position, a first locking member coupled to the movable frame can be positioned to immobilize the first link set so that when the bed is lowered the movable frame is tilted into the Trendelenberg position. A second locking member is also coupled to the movable frame for engaging the second link set for tilting the movable frame into the reverse Trendelenberg position.

Description

This invention relates to adjustable beds and in particular to hospital beds of a type having a movable frame on which a mattress is supported and which can be adjustably elevated between predetermined upper and lower positions and tilted into Trendelenberg and reversed Trendelenberg positions.

When attending to a patient in a hospital bed it is desirable to be able to raise or lower the frame and mattress which support the patient to facilitate tending to the patient's various needs. Also, in some medical procedures it is necessary to tilt the bed into the Trendelenberg position (in which the patient's head is below his feet) and into the reverse Trendelenberg position (in which the patient's head is above his feet). Some known types of beds are capable of these adjustments but are provided with complicated and expensive adjustment linkages whereas other types are simple but somewhat unsatisfactory in terms of adjustability or appearance.

According to a particular preferred embodiment of the present invention, a bed is provided having a movable frame for supporting a mattress and supported above a relatively fixed base by means of first and second link sets which permit the movable frame to be adjusted relative to the base. The link sets are so arranged that when the movable frame is in its uppermost position, a first locking member coupled to the movable frame can be positioned to immobilized the first link set so that when the bed is lowered the movable frame is tilted into the Trendelenberg position. A second locking member is also coupled to the movable frame for engaging the second link set for tilting the movable frame into the reverse Trendelenberg position.

The invention will be better understood with reference to the drawings, wherein:

FIG. 1 is a perspective view of the bed according to the invention with the mattress removed from the bed;

FIG. 2 is a sectional side view on lines 2--2 showing a part of a first link set;

FIG. 3 is an exploded perspective view showing part of a second link set;

FIG. 4 is a sectional side view showing the bed in the Trendelenberg position; and

FIG. 5 is a view similar to FIG. 4 showing the bed in the reverse Trendelenberg position.

Reference is first made to FIG. 1 which shows a bed 10 with the mattress removed. The bed consists of a base or lower frame 12 and a movable or upper frame 14 which is supported by respective first and second link sets 16, 18 above the base 12 for movement between uppermost and lowermost positions. The link sets 16, 18 are held in generally parallel relationship by a yoke 20 coupled to the link sets, and up and down movement of the frame 14 is provided by an actuator 22 which is operably connected to the yoke 20. The actuator is pivotally mounted in a trunnion 24 attached to a transverse member 26 of the movable frame 14 to accommodate variations in height of the yoke 20 as the frame 14 is raised or lowered. When the actuator is energized, it moves the yoke 20 longitudinally thereby rotating the link sets 16, 18 about first and second transverse axes of respective pairs of bearing blocks 28, 30 mounted on the underside of longitudinal members 32, 34 of the frame 14. The lower ends of the link sets are coupled at respective pivots 36, 38 on longitudinal members 40, 42 of the base 12.

The movable frame 14 is lowered by operating actuator 22 which permits the combined weight of the patient and parts above the base 12 to rotate the link sets about respective axes through bearing blocks 28, 30 and about pivots 36, 38 thereby lowering the movable frame 14. To raise the frame, the actuator 22 is energized to move the link sets in the opposite direction. The movable frame 14 can be tilted into the Trendelenberg or reverse Trendelenberg positions by operating respective controls 44, 46 which respectively lock the link sets 16, 18 to the movable frame 14 as will be described.

Longitudinal members 40, 42 of the base 12 are connected at their ends to respective upper ends of uprights 48, 50 and 52, 54, and transverse members 56, 58 extend between respective lower ends of pairs of uprights 48, 52 and 50, 54. The transverse members 56, 58 are therefore below the longitudinal members 40, 42 so that when the movable frame 14 is in its lowermost position, it rests on the transverse members 56, 58 with the link sets 16, 18 extending downwardly from their respective pivots 36, 38. This arrangement provides maximum vertical movement of the frame 14 with minimum longitudinal movement because as the frame 14 is lowered it initially moves longitudinally in one direction and then as the link sets 16, 18 rotate downwardly past the horizontal, the frame 14 commences movement in the other longitudinal direction. Four castors 60, complete the base.

The movable frame 14 includes a transverse member 62 at the head end of the bed for supporting a headboard (shown in chain-dotted outline) and transverse member 64 at the foot of the bed for supporting the footboard (also shown partly in chain-dotted outline). A further frame can be attached to the frame 14 in any manner suitable for supporting a mattress above the exposed parts of the link sets and yoke 20.

The link set 18 consists of a transversely extending tubular shaft 66 which rotates in the bearing blocks 30. Primary links 68 are attached one to each of the ends of the shaft 66 and extend in parallel relationship for movement with the shaft. The distal ends of the links 68 are pivotally connected to respective secondary links 70 which are pivotally connected at 36 to the respective longitudinal members 40, 42. Links 70 are in parallel relationship one with the other and the primary and secondary links 68, 70 are pivotally interconnected intermediate the ends of the links 70 for relative rotation. However rotation is limited by respective pins 72 at the distal ends of secondary links 70. These pins engage respective primary links 68 to prevent the primary and secondary links rotating about their pivotal connections under the influence of a patient's weight. Shaft 66 includes a crank 74 having a pair of spaced-apart upright portions supporting a transverse pin 76 which is engaged in a longitudinally extending slot 78 of yoke 20. When the movable frame 14 is in the uppermost position the crank 74 extends upwardly above the shaft 66.

A rigid projection 80 extends perpendicularly from crank 74 towards the foot of the bed for engagement with a movable stop member 82 pivotally attached to the underside of a cross member 84 of frame 14. As will be described, the stop member 82 can be moved by a rod 86 attached to control 46 into engagement with projection 80 to limit movement of the link set 18.

The link set 16 is similar in most respects to the set 18 and parts similar to those already described with reference to link set 18 will be given primed numerals. However, link set 16 differs from link set 18 in that a compound crank 88 is used in place of crank 74. As better seen in FIG. 2, compound crank 88 consists of an arm 90 rigidly attached to tubular shaft 66' and having a rigid projection 92 extending perpendicularly from arm 90 towards the foot of the bed. A lever 94 is pivotally attached to the tubular shaft 66' and located within the arm 90 which has a U-shaped cross-section. The lever 94, which also has a U-shaped cross-section, is pivotally attached at its distal end to the yoke 20 which extends longitudinally beyond the lever 94 terminating at a pivotal connection 96 with actuator 22. An adjustment bolt 98 having a lock nut 100 is threadably engaged in lever 94 for engagement with a pad 102 welded to the arm 90. The lever 94 is free to rotate between an engaged position where the bolt 98 rests against pad 102 (as shown in FIG. 1) and a released position where it has rotated about tubular shaft 66 away from arm 90 as shown in FIG. 2. The bolt 98 permits adjustment to ensure that after assembly the movable frame 14 is horizontal when base 12 stands on a horizontal surface.

Reference is now made to FIGS. 1 and 3 to describe the stop member 82 which is typical of both stop members 82 and 82'. As seen in FIG. 3, stop member 82 is pivotally connected by an axle 104 to a U-shaped bracket 106 adapted to be attached by screws 108 to cross member 84. Control rod 86 has a cranked end 110 for engagement in an opening 112 of stop member 82, and an opening 114 is provided in the end 110 for receiving a split pin 116 after the end has been passed through the opening 112 and through a washer 118. Respective pins 120, 122 are provided on the member 82 and bracket 106 for attachment to the ends of a tension spring 124. The pins 120, 122 and spring 124 are positioned so that the member 82 is biased into either an engagement position wherein a shoulder 126 engages projection 80 on crank 74 as will be described, or a disengagement position in which the stop member is moved by the rod 86 and control 44 away from the crank 74. The stop member 82' is similar to the stop member 82 and is controlled by rod 86' attached to control 44.

In the position shown in FIG. 1 the movable frame 14 is in its uppermost position with the link sets 16, 118 in generally parallel relationship. In order to stabilize the link sets, a pair of limit links 126 are pivotally connected to respective connections between primary links 68' and secondary links 70' and have slots 128 in which respective pins 130 on base members 40, 42 are loosely engaged. As the link set 16 rotates about pivot points 36, the limit link 126 moves guided by pins 130. In the event that an attendant wheels the bed over a threshold or other floor projection, a force will result which tends to cause the secondary links 70' to rotate towards the foot of the bed about pivot points 38 resulting in sudden collapse of the movable frame 14 downwardly onto the base 12. To prevent this happening the limit links are provided to prevent the secondary links 70' (and hence the links 70) from passing beyond an upright position. Preferably, the links 70' are not permitted to reach the upright position.

In FIG. 1 the frame 14 is in its uppermost position and upon energizing actuator 22 the cranks 74 and 88 are made to rotate in an anti-clockwise direction as drawn so that the link sets 16 and 18 begin to rotate downwardly about respective pivot points 36 and 38. If this movement is continued, the movable frame 14 will eventually rest on the transverse members 56, 58 of the base 12 at which time the movable frame 14 is in its lowermost position. Upon reversing the actuator 22 the movable frame 14 is again raised to its uppermost position.

Reference is next made to FIG. 4 which shows the link sets 16, 18 arranged to support the movable frame 14 in the Trendelenberg position. Initially the stop member 82' is moved into engagement with projection 92 so that upon lowering the frame 14, the arm 90 and primary links 68' are locked in relation to the movable frame 14. As a result there is a reactive force on stop member 82' sufficient to prevent movement of this member into the disengagement position. When the actuator 22 is energized to lower the frame 14, the lever 94 in the compound crank 88 rotates to permit the crank 74 to rotate together with the tubular shaft 66 and primary links 68. As a result primary links 68 move away from respective pins 72 on secondary links 70 and the head end of the frame 14 is lowered. A limited movement of link set 16 takes place about pivot 36 but the link set 16 moves as a locked unit with frame 14 so that there is no relative movement between the primary links 68' and secondary links 70'.

The actuator 22 includes an internal stop to prevent excessive tilting of the movable frame 14 in the Trendelenberg position beyond a typical limit of 11 degrees to the horizontal. It should be noted that the yoke 20 is in tension during this movement into the Trendelenberg position and that the crank pin 76 remains at the outer extremity of slot 78 in yoke 20.

The frame 14 is moved back into its uppermost position by energizing the actuator 22 to raise the frame. Once the frame is in the uppermost position the stop member 82' can then be disengaged from the projection 92 by moving the control 44. The biasing spring 124' holds the stop member 82' in the disengaged position.

Reference is next made to FIGS. 1 and 5 to describe moving the frame 14 into the reverse Trendelenberg position. In this case the control 46 is moved to engage stop member 82 with projection 80 to disable the link set 18. By contrast with the movement of frame 14 from the uppermost position to the Trendelenberg position in which the pins 76 and 76' remain at the same distance apart, in the reverse Trendelenberg movement the pin 76 moves towards the pin 76'. This latter movement is permitted by slot 78 in yoke 20 which allows the pin 76 to effectively move nearer to the pin 76'. Also the actuatuator 22 controls the position of link set 16 so that the lever 94 of compound crank 88 remains in the engaged position. Otherwise the movements illustrated in FIGS. 4 and 5 are similar.

Claims

What we claim as our invention is:

1. An adjustable bed comprising:

a base;

an upper frame movable between an uppermost position and a lowermost position and tiltable from the uppermost position into Trendelenberg and reverse Trendelenberg positions;

first and second generally parallel link sets, each link set comprising: a pair of primary links pivotally coupled to the upper frame; a pair of secondary links pivotally coupled to the base; means pivotally connecting each of the primary links to a corresponding one of the secondary links; and means limiting rotation of the secondary links relative to the primary links in one direction of rotation so that there is no relative movement between the primary and secondary links when moving the upper frame between the uppermost and lowermost positions, the pairs of primary links being coupled to the upper frame for rotation about respective transverse first and second axes, the axes being spaced apart longitudinally in substantially parallel relationship, and the pairs of secondary links being coupled to the base for rotation about respective transverse third and fourth axes spaced apart longitudinally in substantially parallel relationship with the first and second axes such that lines drawn between the axes in a plane at right angles to the axes define a first parallelogram with the upper frame in its uppermost position;

first and second cranks respectively coupled to the pairs of primary links for rotation about the respective first and second axes;

a yoke extending longitudinally of the bed and including pivot pins connecting the yoke to distal ends of the first and second cranks on respective transverse fifth and sixth axes which are parallel to the first and second axis and positioned such that lines drawn between the first, second, fifth and sixth axes in a plane at right angles to the axes define a second parallelogram with the upper frame in its uppermost position, the yoke being stressed when the upper frame is in the uppermost position to maintain the link sets in generally parallel relationships;

first and second stop means coupled to the upper frame and movable for selectively limiting rotation of the pairs of primary links with the upper frame in the uppermost position whereby the upper frame can be moved into the Trendelenberg and reverse Trendelenberg positions, the first stop means being operable to limit rotation of the primary links of the first link set so that upon lowering the upper frame the secondary links of the second link set rotate relative to the corresponding primary links and the upper frame tilts into the Trendelenberg position, the second stop means being operable to limit rotation of the primary links of the second link means so that upon lowering the upper frame the secondary links of the first link set rotate relative to the corresponding primary links and the upper frame tilts into the reverse Trendelenberg position;

actuator means coupled to the cranks and operable to move the upper frame between the uppermost and lowermost positions and between the uppermost, the Trendelenberg and the reverse Trendelenberg positions.

2. An adjustable bed as claimed in claim 1, in which the first crank comprises: an arm rigidly attached to the primary links of the first link set for rotational movement therewith about the first axis; and a lever rotatably mounted about said first axis for rotation between an engaged position in which the lever is in contact with the arm for up and down motion of the upper frame and a disengaged position in which the lever is out of contact with the arm for tilting the upper frame into the Trendelenberg position, the distal end of the lever being coupled to the yoke by one of said yoke pivot pins.

3. An adjustable bed as claimed in claim 1 in which the yoke pivot pin coupling the yoke to the second link set slides in a longitudinal slot formed in the yoke to permit relative movement of the pivot pins towards one another in lowering the upper frame into the reverse Trendelenberg position.

4. An adjustable bed as claimed in claim 1 in which each of said first and second stop means comprises a stop member pivotally mounted on said upper frame and movable between an engaged position in which the stop member abuts a corresponding one of the cranks to thereby limit rotation of said crank, and a release position in which the stop member is clear of the crank.

5. An adjustable bed as claimed in claim 1 in which the cranks extend upwardly above a plane containing said first and second axes with the upper frame in said uppermost position.

6. An adjustable bed as claimed in claim 1 and further comprising a trunnion attached to said upper frame and pivotally mounting said actuator.

7. An adjustable bed as claimed in claim 1 and further comprising at least one limit link pivotally connected to one of said secondary links, and slidably and pivotally connected to said base, the limit link being proportioned so that when said one secondary link rotates upwardly towards an upright position the limit link reaches the end of its sliding movement and prevents said one secondary link from passing the upright position thereby preventing accidental movement of the upper frame into the lowermost position.