Some problems in the formal representation of hierarchical knowledge

A rectangular chair frame equipped with casters upon the lower ends of its legs is provided with a platform seat containing an elongated central commode opening normally closed by a closure mounted upon a transverse pivot shaft secured to one of the elongated sides of the closure and equipped with a hand lever for swinging the closure from its closed position (FIGS. 1 and 2) to its open position (FIG. 3). Thereupon the patient, without being removed from the chair, when the need arises, can be moved to a position over a conventional toilet bowl. Thereafter, the closure is closed by swinging the pivot shaft hand lever 180 DEG in the reverse direction to consequently swing the closure into closing relationship with the opening. The closure is releasably locked in its closed position by a swinging latch lever pivoted to the underside of the seat platform on either side or on the back (as shown). The chair has L-shaped side arms pivotally mounted upon the upper extensions of the rear legs and having forward ends provided with locking collars movable downward and upward into and out of locking relationship respectively with keeper blocks on the upper ends of the forward legs, whereupon either side arm can be swung sidewise in order to slide the patient off the seat platform onto his bed or vice versa. The seat platform may optionally be provided with raising and lowering mechanism (not shown) beyond the scope of the present invention to bring it upward to the level of the bed mattress. One such arrangement is shown in my co-pending application Ser. No. 823,534, filed May 5, 1969 for Invalid Lift-Transfer Chair which on Apr. 11, 1972 was issued as U. S. Pat. No. 3,654,643.