Keyboard switch and method of manufacturing the same

A method of manufacturing a keyboard switch comprising a housing having a base portion and a casing portion, a key top which is slidably supported in the casing portion and has a contact point pressing portion formed as part of the keytop and projecting toward the base portion and a retaining pawl for retaining the rear surface of the housing, and a biasing member for biasing the key top toward a home position, the method comprising the steps of:

• forming a membrane contact point sheet, which has an opening for extending the casing portion therethrough and a contact point portion near the opening, the membrane contact point sheet being formed in a three-layered structure, including an upper contact point sheet, a spacer, and a lower contact point sheet, the contact point portion of the membrane contact point sheet having a window hole provided in the spacer, a first contact point being formed on a lower surface of the upper contact point sheet at a place corresponding to the window hole, a second contact point being formed on an upper surface of the lower contact point sheet at a place corresponding to the window hole, wherein the contact point pressing portion is disposed to directly press the contact point portion of the membrane contact point sheet and thereby press the first and second contact points together;
• inserting the casing portion of the housing into the opening;
• putting the biasing member on the casing portion, the biasing member comprising a spring member disposed between the casing portion and the contact point pressing portion formed on the key top and
• inserting the key top into the casing portion to compress the biasing member until the retaining pawl retains the rear surface of the housing.

A method of manufacturing a keyboard switch comprising the following steps of:

• (a) preparing a membrane contact point sheet having an opening and a contact point portion disposed near the opening;
• (b) preparing a housing having a base portion and a casing portion arranged on and extending from a surface of the base portion;
• (c) preparing a key top having a retaining piece with a tip end, a projecting key lever portion, a contact point pressing portion projecting downward from the key top and a retaining pawl provided at the tip end of the retaining piece;
• (d) preparing a coil-shaped biasing member;
• (e) inserting the casing portion of the housing into the opening of the membrane contact point sheet from a rear surface thereof so that the casing portion extends through the opening of the membrane contact point sheet and protrudes from a front surface thereof;
• (f) arranging the biasing member around that part of the casing portion which protrudes from the front surface of the membrane contact point sheet;
• (g) inserting the key top retaining piece and key lever portion into the casing portion of the housing so that the contact point pressing portion is confronted with the contact point portion of the membrane contact point sheet;
• whereupon the biasing member pushes the key top away from the housing base portion and the retaining pawl prevents the key lever portion from coming out of the casing portion.