Abstract: An adjustable-length column for chairs or the like has an upright tube and a pneumatic or hydropneumatic length-adjusting element arranged in the latter, the housing of the element being radially supported in the upright tube and displaceably guided in the direction of a common axis. A profile guarding against twisting is tightly arranged on the housing in particular by shrinking and has at least one radially projecting web which extends parallel to the axis and engages with a groove-like recess of a guide which is non-rotatably connected with the upright tube.

Abstract: In the case of a longitudinally adjustable gas spring with two tubes enclosing each other concentrically and with a valve at one end and with a relief channel at the end where the piston rod exits the inner tube consists of plastics material. It has groove-like channels on its external wall which connect the relief channel with the valve. The webs between adjacent channels bear against the internal wall of the outer tube. The result is a cost-saving structure of the inner tube, which at the same time becomes very stable and is easy to manufacture.

Abstract: An elevating mechanism for chairs, tables or the like has a guide tube for a gas spring. The guide tube has a bottom plate with an opening. In its section penetrating through the bottom plate the piston rod is provided with a necking on which a retaining ring is arranged.

Abstract: In a lockable elevating mechanism for the continuous adjustment of chair seats a guide tube is provided, to the bottom plate of which is secured a piston rod of a longitudinally adjustable gas spring. The guide tube is provided with an additional tube, which can be exited telescopically and and which is guided in a guide bush arrested in the guide tube. The housing of the gas spring is in turn guided in a guide bush arrested in the additional tube. A mechanical spring is provided between the guide tube and the additional tube and acts upon the additional tube in a direction out of the guide tube.

Abstract: A longitudinally adjustable gas spring has a valve having a valve pin arranged to be moved within a valve body. On both sides of the inner chamber of the valve body annular seals are arranged and bear against the cylindrical sections of different diameters. To bridge at least one annular seal grooves are formed in an associated cylindrical section. When the corresponding annular seal is bridged by a displacement of the valve pin, the respective annular seal remains in its position bearing against the cylindrical external surface of the corresponding cylindrical section, so that the wear of the seals implying the gas spring to become unserviceable is eliminated.

Abstract: A longitudinally controllable adjustment device comprises a cylindrical housing, in which a piston rod with a piston is slidable and sealingly extending outwards. Furthermore it comprises a valve for controlling length adjustment of the device. In order to avoid a destruction of seals preventing a flow to the outside of pressure medium at least two seals are provided between the housing and the piston rod whereby a seal between the outer end of the housing and a further seal prevents an inflow of gas and in particular of liquid from the outside into the housing.

Abstract: An adjustable-length gas spring has a compressed gas-filled housing in which a piston with a piston rod is sealingly guided. At one end of the housing is provided a valve with a valve pin for connecting or separating two housing chambers, the valve pin being movable into the housing against the force exerted thereon by the gas pressure with the valve in the open position. The pin is movable against such force when the valve is in the closed position. There is also a permanent release mechanism for securing the valve pin when the valve is in the open position. In order to permit a particularly simple operation of the gas spring, the permanent release mechanism is formed by a bi-stable locking mechanism constructed in the manner of a mechanical flip-flop and which is coupled to the valve pin, being operated by the insertion thereof into the housing.

Abstract: A dental impression tray includes a tray portion anatomically contoured to fit over at least a part of a patient's upper and/or lower dentition of which an impression is to be obtained. The tray portion is loaded with impression material and situated opposite to the desired dentition part whereupon the patient bites into the soft impression material to form an impression of the dentition in the material. The tray portion is defined by at least one wall on which a plurality of vertically extending adjacent ribs are integrally formed defining a plurality of channels therebetween into which the impression material flows. The ribs have a dovetail cross-section so that the channels narrow or converge in the inward direction, i.e. towards the interior of the tray portion, to prevent the impression material from separating from the side wall in the inward direction as well as spreading laterally as and after the impression is taken to thereby provide a precise impression of the dentition.

Abstract: A disposable dental tray for medications such as fluoride gel, includes a unitary member formed of a flexible foam material defining a pair of hinged U-shaped tray portions configured to fit over the upper and lower teeth of the mouth and wherein each tray portion is defined by a base wall, a pair of end walls and inner and outer side walls. Both of the tray portions are provided with respective tray portion positioning tabs extending from their respective outer side walls. The positioning tabs include respective tab sections which are pre-formed so as to be situated such that when the tray portions are folded, the respective tab sections will automatically abut and be squeezable against each other without the consequent application of any forces to the outer side walls of the tray portion thereby preventing any possibility of distorting the tray portions during use.

Abstract: In an exemplary embodiment a multiplexer unit is arranged in the first device unit in the input channels for electric physiological signals and a demultiplexer unit is arranged in the second device unit on the side of the output channels for the time-shared scanning of the signals in the input or, respectively, output channel; and a pulse amplitude modulator and a single galvanically separating coupling location are inserted in series between the multiplexer unit of the first device unit and the demultiplexer unit of the second device unit at the interface between both device units for the de-coupled signal transmission in the time multiplex mode. By this arrangement the minimized number of coupling locations holds coupling capacitance and leakage current to a minimum with only a modest outlay for appertaining control circuitry.