Punch press assembly including a preloaded encapsulted spring

A punch assembly comprising an elongated punch having an enlarged head at its upper end, a generally cylindrical stripper means supported for reciprocation in a holder wall, said stripper means having a longitudinal passage therethrough for receiving the lower end of said punch, and an encapsulated spring assembly mounted between an upper surface of said stripper and said punch head for resiliently supporting the upper end of said punch above said stripper, said spring assembly having first and second housing halves each having a circumferential peripheral wall and at least partially closed bottom wall and an open end spaced by the peripheral wall from the bottom wall, the first housing half having an outer diameter smaller than the inner diameter of the second housing half, the first housing half having its open end telescopically received interior of the open end of the second housing half, a loaded spring received interior of the housing halves operatively abutting the bottom walls thereof to urge the housing halves away from one another, the housing halves having mating circumferentially engaging faces spaced from their bottom walls engageable by movement of the housing halves axially with respect to one another, the faces limiting axial movement of the housing halves with respect to one another in a direction away from one another but allowing movement of the housing halves in the direction towards one another, said punch extending through a central aperture in one housing half bottom wall into said stripper passage.

A preloaded spring punch and stripper assembly comprising first and second housing members, each housing member including a substantially tubular peripheral wall with an internal partial radial wall portion and an open end at a first axial end of the peripheral wall, the first housing member having a maximum outer diameter less than a maximum inner diameter of the second housing member, the open end of the first housing member inserted into the open end of the second housing member, the first and second housing members being telescopically axially movable, an outer diameter increasing section of the first housing member adjacent the axial end of the first housing member, an inner diameter decreasing section of the second housing member intermediate axial ends thereof and adjacent the first axial end, the sections abutable with one another and the abutment preventing removal of the first housing member from the second housing member, a spring received interior of said housing members, the spring having a free spring height greater than a maximum axial internal height of the housing members when the sections are abutted whereby the spring is preloaded, a punch having a head end received in the second housing member and a lower end extending therethrough, a stripper carried by the first housing member projecting from the partial radial wall thereof in a direction opposite the second housing member and encircling the punch lower end remote from the head end, means supporting the head end of the punch by an abutment member received interiorly of the second housing half, the spring acting against the abutment member urging the abutment member into contact with the partial radial wall of the second housing member and lifting the punch within the stripper, and means for retaining the entire assembly of stripper, encapsulated spring, and housing members together as a single unit.

A preloaded spring, punch and stripper assembly, the preloaded spring assembly including first and second telescoping housing members having cup shaped interiors defined by peripheral walls and partial bottom walls with the bottom walls of the first and second members being opposed to one another with a spring received interior thereof entrapped between the bottom walls, one of said housing members having an inner diameter greater than the outer diameter of the second of said housing members whereby the second of said housing members projects into the interior of the one housing member, the housing members having respectively radially outwardly extending and radially inwardly extending peripheral wall portions adjacent open ends thereof providing interference mating preventing separation of the parts and establishing a maximum stacked height less than the free length of the spring whereby the spring is preloaded interior of the housings characterized in that each housing half is provided with an axial opening for receipt for a punch, the punch extending through the preloaded spring assembly and projecting beyond the axial end of the second housing half, a stripper received around said projecting portion of said punch, the stripper being fixedly attached to the second housing half and aligned with the openings in the housing halves, the stripper having an axial bore therethrough receiving the punch, the movement of the punch in the preloaded spring assembly in a direction towards the stripper being limited by engagement of a head end of the punch with a portion of the assembly contacting an end of the spring, movement of the punch towards the stripper causing compression of the spring and relative movement of the telescoped housing halves towards one another and the housing halves, spring and stripper being retained together as a single unit.