Fixture cylinder with proximity switches mounted on end caps without spacers

A fixture cylinder that employs substantially identical proximity switches without requiring spacers on the end caps, said cylinder comprising:

• a cylindrical body for housing a piston assembly, said piston assembly including a piston head, a piston rod and a pair of hubs of substantially the same diameter on opposite sides of the piston head, the piston assembly being slideably mounted about a piston axis in a bore in the body;
• a first end cap attached to one end of the body and extending transversely to the piston axis, said first end cap being of a unitary construction and including generally square wall portion adjacent to the body and having four edges, a nose portion of reduced cross section relative to the wall portion and extending away therefrom concentrically with the piston axis through which the piston rod extends, and the end cap further including a integrally formed boss raised up from one edge of the plate portion, the boss providing a generally flat mounting surface for one of the proximity switches, the end cap having an aperture extending from the mounting surface perpendicularly into the bore, the end cap further including a first bore for receiving the piston hub and communicating with ambient air through a port, a cushion seal concentrically mounted about the piston axis inboard of the aperture for engaging said one piston hub, an air passageway between the first bore in the end cap and the bore in the body, a regulating screw in the air passageway, and the first end cap further having a mounting mechanism for attachment to external support structure;
• a second end cap mounted to an opposite end of the body, said end cap being of a unitary construction including a wall portion extending transversely to the piston axis and having four outer edges, the end cap further including an integrally formed boss raised up from one edge of the wall portion for providing a mounting surface for a substantially identical proximity switch, the end cap further including an aperture extending perpendicularly from the mounting surface into the bore in the body, the second end cap further including a second bore for receiving the opposite piston hub and communicating with ambient air through a port, a second cushion seal inboard of the aperture for engaging the opposite hub, an air passageway between the second bore in the second end cap and the bore in the body, a second regulating screw in the passageway, and the second end cap having a mounting mechanism for attachment to external support structure cooperating with the mounting mechanism in the first end cap to hold the cylinder in a desired orientation;
• the mounting surfaces on the bosses in the first and second end caps being substantially coplanar and spaced equidistant from the piston axis;
• a first proximity switch having a flat lower mounting surface and a fixed length probe extending perpendicularly therefrom;
• a second proximity switch substantially identical to the first proximity switch;
• a first pair of screws extending downwardly through the first proximity switch into the first end cap in the area of said boss therein on opposite sides of the aperture serving to bring the lower mounting surface of the proximity switch into precise abutting relation with the mounting surface provided by the boss so that the probe extends freely through the aperture toward the piston bore;
• a second pair of screws extending downwardly through the second proximity switch into the second end cap in the area of the boss therein on opposite sides of the aperture serving to bring the lower mounting surface of the second proximity switch into precise abutting relationship with the mounting surface provided by the boss in the second end cap so that the probe extends freely through the aperture toward the piston bore;
• and
• whereby the same proximity switches can be used to precisely detect the position of the piston rod hubs without requiring the use of spacers between the proximity switch and the end caps.