PREFERRED EMBODIMENT

[0015] Referring to FIG. 1, a vertically adjustable bed 1 is shown having a rectangular like bed frame 2 which has cross members 3 and 9 which gives the bed frame its rigidity.

[0016] The leg arrangement associated at each end of the bed consists of a inverted U shaped main leg frame member 7 which is pivotally and movably attached to the bed frame by means of bearing block 4 at pivot point A. This arrangement allows the top of the leg frame member 7 to follow the bearing block as it travels longitudinally along the linear guide 5 in response to the movement of a linear actuator associated with the motor means 10 . The bearing block consists of a square like block having a circular aperture therethrough. The operation of the motor moves the bearing block 4 by means of the linear actuator longitudinally along the linear guide rod 5 . This action causes the main frame leg to collapse and lower or extend and rise under the bed.

[0017] Returning to the leg arrangement, the main leg frame member 7 is pivotally attached at its mid point B to one end of a linkage arm 8 . The other end of the linkage arm 8 is fixedly attached at C to a rotatable sleeve on cross member 9 . It should be noted that the pivot points A, B and C are equidistant from one another which permits the vertical up and down motion of the bed in response to the movement of the bearing block along the linear guide by means of the linear actuator. In operation, the movement of the bearing block along the linear guide rod 5 will either rotationally collapse or raise the main leg.

[0018] One problem with raising a bed from its lowermost position is the greater motor power required to initiate the raising sequence action. This is because there is no effective angle 0 between the main leg frame member 7 and the bed frame 2 as shown in FIG. 1 . When collapsed, the main leg frame member 7 is tucked under the bed frame and is virtually parallel thereto. The angle θ is effectively zero. For this reason, spring members 6 are provided at each end of the linear guide rod mounted circumferentially thereon and optionally fixedly attached to one of the transverse cross-members 3 as shown or to the bottom of the leg. Referring to the earlier description of the operation of the bed, when lowering the bed the front face of the bearing block 4 will eventually come into contact with and engage the spring 6 . Further lowering action will cause the spring 6 to longitudinally compress between the bearing block and the transverse cross-member. Full compression occurs at the lowermost position. When the bed is sought to be raised the energy in the compressed spring 6 acts on the front face of the bearing block 4 to initiate the first or initial movement along the linear guide rod without reliance on the motor at this most critical point. Once movement has been started by the spring and an effective angle 0 established, the motor is able to take over to easily raise the bed.

[0019] The operation of the special foot/caster leg arrangement will now be described with reference to FIGS. 2 and 3 . It can be seen that each open end of the U shaped main leg frame member 7 is connected by a rigidly attached horizontal cross frame member 18 . According to this invention, a foot/caster leg is rotationally or pivotally attached at each end of cross member 18 by means of a shoulder bolt (non shown) passing through hole 16 in the flange 17 to which the foot 14 and caster 13 are attached at either end. As such, and with reference to FIG. 3 , the center line of the caster 13 is distance B from the center line passing through the shoulder bolt. The center line of the foot 14 is distance A from the center line passing through the pin 15 . The caster and foot are thus separated from one another by a ratio of B:A. Further operation of the foot/caster leg arrangement is now described.

[0020] As the bed is lowered or raised, a dog or pin 11 which is fixedly attached and outwardly extends from each end of the cross leg member 18 , will move in an arcuate fashion by reason of its off center location with reference to the longitudinal center line of the cross member 18 . The arcuate movement of the dog or pin 11 is achieved as a function of rotation of the main leg frame member 7 . The dog or pin 11 is aligned and constrained within an arcuate slot 12 in the flange. Thus, and with reference to FIG. 3 , when the bed as in the example shown is in its upper most position, the dog 11 will have moved clockwise in the arcuate slot 12 to the position shown in 3 , thus engaging the flange at the point of contact X as shown. Further movement of the dog as the bed is raised causes the flange to rotate in a clockwise direction onto the caster wheel. Correspondingly, the foot will come off the ground. The reverse action will cause the dog 11 to rotate counter clock wise within the arcuate slot 12 ultimately into disengagement with the end of the slot X and towards the other end of the slot Y wherein the foot will fully engage the floor. It is the constraint of the dog within the arcuate slot which ensures that, excepting only one intermediate position, only the leg or caster are in contact with the floor but not both. It can be seen that the pivot distances B and A (ratio B:A) shown in FIG. 3 can be geometrically matched and sized to the length of the arcuate slot 12 to ensure that the foot 14 comes off the floor at or about the uppermost travel position of the bed. Further movement of the bed to its highest position causes the foot/caster leg to pivot to fully engage the caster wheels with the floor. Thus, the bed remains fixed on the ground through most of the vertical travel sequence.

[0021] The particular arrangement shown for the pin is not essential. What is important is to use the rotational motion at the bottom of the leg or horizontal base frame member by some means such as a pin to engage one end of a slot or channel to obtain the desired action. As such, the pin can be made to extend upwardly at right angles to the longitudinal axis of the horizontal base frame member and the foot/caster can be adapted with an interior channel within which the pin can move to engage one end of the channel.

[0022] A second foot/caster leg on the other end of cross member 18 operates in the same identical fashion but in reverse with respect to the description of the clock wise and the counter clock wise travel directions of the dog 11 within the arcuate slot 12 . Obviously, the other main leg frame is equipped identically and operates in an identical and complementary fashion. All of the actions are synchronized to achieve the objects of this invention. As well, the foot caster may be optionally attached to the bottom of the leg and made to function in like fashion.

[0023] From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to, the structure.

[0024] It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.

[0025] Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.