Tilt bed

Claim 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.