This invention relates to Ttig pressure double action pumps particularly used for pumping aggressire liquids such, as atomising ones used in agriculture.

!Uhe corrosive ef ect of such liquids on metalic portions which they touch is very well known _*

Ehe most affected part is the one that old^ th press button pump set. This set carries a metalic cylinder in its core -where the end portionOf a forcer works conduction piston giving raise to the alternative motion of the pump.

This press ^" button, conventionally, comprises a gasket made of a synthetic flexible material fixed to the forcsr or piston and working by pressing the walls of said cylinder. -Shis gasket, besides pressing the liquid, works also as a packing for preventing the liquid from pouring between the walls of the cylinder into the functional inner parts of the pumps.

One of the principal problems linked to this kind of pump lies exactly on this fact, because the liquid, due to its aggressivity, injures said walls, giving raise, in a very short time, to erosion that precludes the packing action exerted by said gasket. ϋ3ais fact thus gives urge to frecuent changes of cylinders and consequently to additional costs and de erment in production, due to the forced stoppage of the equipment.

Cylinders made out of porcelain have been regarded as a solution to this erosive process, as they do not suffer under the liquid aggressivity. Considering, however, that procelain is a very expensive imported material, subject to accidental breakage, the inadequacy of its commercial utilization becomes quite obvious.

-Uhis invention, evading the various propositions offered up to now, solves this problem in a practic, cheap, efficient, ^" also feasible under an industrial view point.

32he annexed drawings illustrate this invention which is characterized ^" by the fact of applying to the inner walls of said cylinder 1, covering this wall 2 completely, an impeimeable and cylindrical jacket 3, made of a convenient flexible material substantially in the form of a drinking glass, being said jacket fixed .zj means of its circular flange 4 to the top portion 5 of said cylinder, and fixed by means of its bottom portion 6, preferably having central hole 7, to the end portion 8 of the forcer or piston 9 which operates inside the cylinder 1.

In the drawings, figure 1 is a view in. perspective of the flexible jacket 3 before adjustment to the cylinder, figures 2 A d 3 are sectional side views of said jacket now positioned in the cyl±nder, duly fixed by means of said flange 4 to the top portion of said cylinder and by its bottom portion β to the end portion of piston 9. Hole 7 at bottom β is meant to easily fitting the jacket to the forcer or piston whereto said jacket is fixed by proper means such as fasting screw lock washers (10.11).

-Figure 4 is a partial sectioned side view of a common pump, as above mentioned, duly equipeά with the improvement object of this invention-. It illustrates, in special, a simple manner of fixing flange 4 of said gasket between the top portion of said cylinder and the headstock base 12, meant to the input and output of the liquid under pumping action. Figures 2 and 3 illustrate, in special, the performance of said jacket inside said cyl±nder when said forcer or piston is at work. These figures show that in

whatever position said forcer or piston may be, said cylinde walls 2 remain permanently apart from the li uid action, free from its aggressive results. 2-he outstanding advantage broug by this invention permits the manufac uring of such cylinders with cheap materials, on the contrary of the general use nowadays, such as common metals, even iron, because they do not have to offer any special qualification in order to resis to the corrosive effect of the liquid under pumping.

Said figures 2 and 3 clearly illustrate that sai flexible jacket follows the alternative motion of the forcer piston, inclusively protecting said piston or forcer against contact with said corrosive liquid. It most also be stressed that the pressure effect of said liquid against the neck portion 13 of said jacket becomes substancially weakened in point ? (point of -πa-r-.TTOT- pressure incidence) because point 2? changes of place according to each position of said forcer or piston performance. This fact gives origin to a regular .and ur.1form distribution in the whole extension of said jacket of a resistance strenght that ensures to said jacket, in whic concerns fatigue of materials, practically endless life.