Apparatus for patient-controlled drug injection having counter

An apparatus for patient-controlled drug injection having a counter, comprising:

• a case;
• a pressing part, provided in the case, for applying pressure to pump a chemical liquid;
• and
• a counter, provided in the case and having a counting button that is pressed by pressure when a user presses the pressing part, for counting the number of times that the pressing part is pressed,
• wherein the counter includes a timer for preventing the pressing part from being pressed again within a certain period of time after the pressing part is pressed, and
• wherein the timer comprises:
• a mainspring which is rotated and wound when the pressing part is pressed;
• a cam rotated by the elastic force of the mainspring, wherein a part of an outer circumferential surface of the cam forms an arc having a longer diameter than the rest;
• and
• a latch for constraining the pressing part while being pressed according to the rotation angle of the cam, or elastically restoring to release the constraining of the pressing part.