Abstract: A novel mechanical power unit for use in stool and the like construction having features allowing its easy application to great variety of additional uses. The power unit has a ram which is displaced within a cylinder under the influence of hydraulic fluid driven by compressed air. The fluid and compressed air are carried in a reservoir generally surrounding the cylinder, formed by the outer wall of the cylinder and the inner wall of a generally concentric shell welded permanently at its ends to the cylinder. A manually operable, normally closed valve is provided in the base of the cylinder to control transfer of fluid between the interior of the cylinder and the reservoir to operate the power unit, causing the ram to extend or retract with respect to the cylinder, and holding the ram in any amount of extension when the valve is closed.

Abstract: A manual suspension support, in which a pair of tubes are telescoped using a vacuum source. A slidable piston in a cylinder is selectively brakable by manipulation of a handle which also carries a valve operable to vary the vacuum in the cylinder.

Abstract: The height of a chair and the inclination of its back support may be varied by changing the respective, effective lengths of two pneumatic springs whose assembly forms the chair leg. The cylinder of one spring is coaxially received in the cylinder or the hollow piston rod of the other spring, and relative axial movement of the received spring and the receiving element of the other spring is limited or entirely prevented. A valve connects the two compartments separated in the cylinder of each spring and may be operated by a mechanism separate from the valve operating mechanism of the other spring.

Abstract: An apparatus for raising and lowering a windable, portable motion picture screen which has a sliding pole inserted into a vertical opening within a hollow support cylinder in such a way that the sliding pole can slide up and down within the cylinder. A lever member is provided on the upper portion of the supporting cylinder to force against the sliding pole within the cylinder and hold it in position. The sliding pole is provided with a rack portion on one side thereof and rack and pinion gear drive means are connected to the side of the supporting cylinder in such a manner that they engage the rack portion of the sliding pole to move it up and down within the supporting cylinder as the gears are rotated.

Abstract: A surgical chair for a doctor embodying an infinitely elevationally adjustable seat connected with a support column, a stand tube arranged within the support column, at which there is attached a base frame equipped with rollers and a lifting device within the stand tube. The lifting device is operatively connected with the support column and can be unblocked by a lever system so that the seat, depending upon the degree of loading thereof, is elevationally adjustable. A foot pedal located between two overhang members of the base frame is arranged with its upper edge at most 4 centimeters above the floor and with adjustable freedom of movement with respect to the floor. The foot pedal is secured by a lever to an angle lever pivotably mounted at the stand tube and acts upon a plunger of the lifting device. At least three guide grooves are provided at the support column and extend uniformly about its inner periphery and parallel to its central axis.

Abstract: An instrument support structure having a post vertically telescoped in a column and an interfitted cylinder and rod within the post defining a hydraulic piston connecting the post and the column. A hydraulic reservoir is mounted on the column, is in fluid communication with the piston, and is pressurized so as to exert a force balancing the weight on the post. Pressurization is by air through a common tire valve so that various weights can be selectively balanced. An adjustable fluid valve controls the rate of fluid movement to and from the piston so as to hydraulically lock the post or adjustably control the rate at which a force can reposition the post. A spring biased shoe holds the post against walls in the column, and a threaded lock element enables the shoe pressure to be increased to mechanically lock the parts.