the enclosure fig2 is a sectional view showing a piston pump 10 u2033 according to still another embodiment because the basic construction is the same as the one shown in fig1 the common portions are omitted this piston pump 10 u2033 is directed to suction or pressure reduction but not to exhaust therefore handle portions of the valves 18 and 26 are inserted and fixed from the lower side in the drawing into the insertion holes 24 and 29 in the valve plate 16 and the piston 14 in this construction air moves in the reverse direction to the explanation of fig1 the pressure of the space 31 is reduced and air is sucked from outside through the discharge port 32 a wall 73 at the depth that is omitted from fig1 for simplification is expressed beyond the crank shaft 38 holes 78 and 78 for accommodating projections 76 and 76 disposed on the cover 47 are disposed at both ends of the wall 73 at the depth the cover 47 can be kept under the closed state when these projections 76 and 76 are fitted inserted into the holes 78 and 78 respectively fitting between the projection 76 76 and the holes 78 78 may be loose fit but is preferably close fit to a certain extent fitting may also be sliding fit this is to obtain desired pull out resistance the shape may be a simple rod shape or a rod shape having a projection at an intermediate part when a polymer material such as a plastic material is used the shape is more preferably the simple rod shape at this time the partition plate 72 having the opening on the side of the housing substrate material 44 and the partition plate 74 on the side of the.