Device for transforming a single pressure force into separate pressure forces

In a punching apparatus:

• a main body having a first chamber and a second chamber connected by an axial bore, said axial bore opening on an end wall of said first chamber;
• a power piston received in said first chamber, and movable toward and away from said end wall;
• a piston rod received within said axial bore, and having a retraction piston thereon slidably received within said second chamber;
• punch means arranged to be operated by said piston rod upon downward movement thereof, to engage a workpiece;
• stripper means carried by said main body on the lower end thereof, and engageable with said workpiece;
• means defining a buffer chamber, said buffer chamber containing a slidably mounted buffer piston, and means urging said buffer piston toward one end wall of said buffer chamber;
• first passage means connected with the region of said second chamber beneath said retraction piston;
• second passage means connecting said first passage means with the region of said buffer chamber beneath said buffer piston;
• third passage means connecting said seond passage means with the region of said first chamber beneath said power piston, and including a one-way valve arrangement to permit flow only from said second passage means to said first chamber;
• and
• fourth passage means connecting said first passage means with said first chamber, and including valve means arranged to open only after said power piston has moved a predetermined distance within said first chamber toward said end wall;
• said first chamber beneath said power piston, said second chamber beneath said retraction piston, said buffer chamber beneath said buffer piston, and said passages being arranged to receive an operating fluid, whereby when pressure is initially placed on said power piston to move said power piston toward said end wall of said first chamber said punch means and said stripper means will be engaged with said workpiece with separate pressure forces that are directly dependent on each other and on the strength of said workpiece, said valve means of said fourth passage means opening in response to further movement of said power piston occurring after said punch means penetrates said workpiece to operate said retraction piston for retracting said punch means while said stripper means remains engaged with said workpiece.