PURPOSE: To prevent breakage of cylinders etc. by fixing on a plunger and a cylinder repectively both an inside outside sleeves which doubly enclose the cylinder in the pump consisting of glass cylinder and plunger.

CONSTITUTION: A glass cylinder 2 is fixed on a body 1, and a plunger 3 is inserted slidably into the cylinder 2. The inside sleeve 5 fixed on a plunger head 4 through screwing process extends downward concentrically to the plunger 3 and enclosing the cylinder 2. The outside sleeve 6 fixed on the body 1 extends upward concentrically to the cylinder 2 and enclosing the inside sleeve 5. As the glass cylinder 2 is enclosed doubly by the inside sleeve 5 and the outside sleeve 6, breakage due to hit by foreign material etc. can be avoided.