Abstract: A progressive simultaneous vision optical lens for correcting presbyopia corresponding to a low addition is of the kind in which the curve representing the proximity (or power) P lies in an area between a lower envelope curve P.sub.inf and an upper envelope curve P.sub.sup having the following polynomial equations: ##EQU1## where h is the height relative to the axis of the optical lens, i.e. the radial distance from the latter. By appropriate choice of the coefficients A'.sub.i and A".sub.i, the near vision area is made relatively large. Applications include contact lenses, intraocular implants and intracorneal lenses.

Abstract: To define a far vision area and a near vision area in a simultaneous vision ophthalmic lens for correcting presbyopia, the curve representing the proximity as a function of the distance from the axis lies within an area between a lower envelope curve and an upper envelope curve with associated specific polynomial equations in which the coefficients depend on the proximity addition corresponding to the degree of presbyopia of the wearer. Either the far vision area or the near vision area is strengthened relative to the other, the corresponding surface areas S.sub.VL, S.sub.VP being related as follows:for strengthened near vision:1.8.ltoreq.S.sub.VL /S.sub.VP .ltoreq.3.6and for strengthened far vision:4.75.ltoreq.S.sub.VL /S.sub.

Abstract: The proximity P of a simultaneous vision optical lens for correcting presbyopia is defined as the reciprocal of the distance D at which a light ray parallel to and at a distance h from its axis crosses the axis after passing through the lens. The curve representing the proximity P of the lens lies between a lower envelope curve P.sub.inf and an upper envelope curve P.sub.sup satisfying the following equations:P.sub.inf =f(h)=(.SIGMA.A'.sub.i h.sup.i)+P.sub.VLP.sub.sup =f(h)=(.SIGMA.A".sub.i h.sup.i)+P.sub.VLin which P.sub.VL is the proximity for distant vision and A'.sub.i, A".sub.i are numeric coefficients depending on the proximity addition added for near vision to the proximity for far vision. The lens may be implemented as a contact lens, an intra-ocular implant or an intra-corneal lens.

Abstract: A bundle of J-shaped tubes uniformly spaced in radial planes about the axis of a cylindrical shell is provided for the circulation of a primary fluid between on the one hand an inlet header delimited by a central tube plate and by the top dished end of the shell and on the other hand a toric outlet header which is partly delimited by the peripheral tube plate and the shell wall and is located above an annular space between the shell wall and a coaxial inner skirt. At least one nozzle for the supply of secondary fluid in the liquid state opens into the annular space and a lateral chamber is formed within the shell between the primary fluid inlet and outlet headers for collecting the secondary-fluid steam produced in contact with the tubes.

Abstract: A generator for the production of both superheated steam and saturated steam has an outer casing formed by an inner cylindrical shell engaged within an outer cylindrical shell, the shells being closed by dished ends. An annular header for the admission of pressurized primary water is formed between an upper annular tube plate and a partition-wall while an outlet header for the discharge of primary water is formed by a central tube plate mounted within the inner shell. A bundle of parallel tubes for the circulation of primary water extends vertically upward from the central tube plate. The end portion of each tube has the shape of a crook in order to join the tubes to the annular tube plate in uniformly spaced relation. The secondary water is admitted into the casing by means of ducts formed in the inner shell near the central tube plate. The steam generated is discharged through ducts formed in the outer shell.