Power press die cushion with air decelerator

Claim 2

A controlled return pneumatic die cushion for a power press, the cushion having an air chamber under substantially constant pressure which respectively contracts and expands in volume as the cushion is decreased in height under the force of a power press ram and as the cushion recovers its original height when the force of the ram is removed, the cushion including a cavity which respectively expands and contracts in volume as the height of the cushion decreases and increases, the cushion including a decelerator valve for bleeding air in a controlled manner from the cavity to control the rate at which the cushion returns to its original height, the valve communicating with the air chamber and the cavity and responsive to the ratio of cavity pressure to air chamber pressure to open when a given ratio has been exceeded.

Claim 3

The die cushion of claim 1 wherein the decelerator valve includes a plug, a conduit communicating one side of the plug with air pressure in the cavity, another conduit communicating the other side of the plug with air pressure in the air chamber, and a valve seat engageable with the one side of the plug to close the valve.

Claim 4

The die cushion of claim 2 in which the one and the other of the plug sides have effective hydraulic areas upon which the cavity pressure and air chamber pressure act, respectively, to move the plug into and out of engagement with the valve seat, and wherein the cavity and air chamber each have effective hydraulic areas Upon which respectively act the cavity and chamber air pressures in opposition to one another, the ratio of the effective hydraulic areas of the one side of the plug to the other side being slightly greater than the ratio of the effective hydraulic area of the cavity to that of the air chamber.

Claim 5

The pneumatic die cushion of claim 1 in which the decelerator valve includes a manually operable flow control valve communicating with the cavity for bleeding air therefrom to the atmosphere, whereby the rate of return of the cushion to its initial height may be closely regulated.

Claim 6

A controlled return pneumatic die cushion for a power press, the cushion including an air chamber under substantially constant pressure which respectively contracts and expands in volume as the cushion is decreased in height under the force of a power press ram and as the cushion recovers its original height when the force of the ram is removed, the air chamber having an effective hydraulic area upon which the pressure therein acts to urge the cushion to its original height, the cushion including a cavity which respectively expands and contracts in volume as the height of the cushion decreases and increases, the cavity having an effective hydraulic area upon which the pressure therein acts to oppose return movement of the cushion, and a decelerator valve for bleeding air in a controlled manner from the cavity to control the rate at which the cushion returns to its original height, the valve including a valve seat, a plug having one side engageable with the valve seat and in communication with pressure in the cavity and an opposed side in communication with pressure in the air chamber, the sides of the plug having effective hydraulic areas upon which act the cavity and air chamber pressures, respectively, to move the plug out of and into engagement with the valve seat, the ratio of the effective hydraulic area of the one plug side to that of the other plug side being slightly greater than the ratio of the effective hydraulic area of the cavity to that of the air chamber, whereby the plug disengages the valve seat to enable air to escape from the cavity when a given ratio of cavity pressure to cushion pressure has been exceeded, thereby decelerating the return movement of the cushion to its original height.

Claim 7

A controlled return pneumatic die cushion for a power press, the cushion including an air chamber under substantially constant pressure which respectively contracts and expands in volume as the cushion is decreased in height under the force of a power press ram and as the cushion recovers its original height when the force of the ram is removed, the air chamber having an effective hydraulic area upon which the pressure therein acts to urge the cushion to its original height, the cushion including a cavity which respectively expands and contracts in volume as the height of the cushion decreases and increases, the cavity having an effective hydraulic area upon which the pressure therein acts to oppose return movement of the cushion, and a decelerator valve for bleeding air in a controlled manner from the cavity to control the rate at which the cushion returns to its original height, the valve including a valve seat, a plug having one side engageable with the valve seat and in communication with pressure in the cavity and an opposed side in communication with pressure in the air chamber, the sides of the plug having effective hydraulic areas upon which act the cavity and air chamber pressures, respectively, to move the plug out of and into engagement with the valve seat, the ratio of the effective hydraulic area of the one plug side to that of the other plug side being slightly greater than the ratio of the effective hydraulic area of the cavity to that of the air chamber, whereby the plug disengages the valve seat to enable air to escape from the cavity when a given ratio of cavity pressure to cushion pressure has been exceeded, thereby decelerating the return movement of the cushion to its original height.

Claim 8

The die cushion of claim 5 wherein the effective hydraulic area of the air chamber is approximately twice that of the cavity.

Claim 9

The die cushion of claim 5 wherein the decelerator valve includes a manually operable flow-control valve communicating with the cavity for continuously bleeding air from the cavity as the cushion returns to its initial height.

Claim 10

A controlled return, pneumatic die cushion for a power press, the cushion comprising an upright cylinder and piston having confronting surfaces defining the top and bottom walls of an air chamber, the cylinder being movable downwardly upon the piston under the force of a power press ram to reduce the volume of the air chamber, the piston and cylinder further having opposed, confronting surfaces defining the upper and lower walls of a cavity which expands in volume as the cylinder moves downwardly upon the piston and which retracts as the cylinder regains its initial heighth when the pressure of the ram of a press is removed, a source of air under substantially constant pressure communicating with the air chamber, and a decelerator valve carried by the cylinder and including a plug having one side in flow communication with the cavity and an opposed side in flow communication with the air chamber, the valve including a valve seat engageable by the one side of the plug, the opposed sides of the plug having effective hydraulic areas upon which act the pressures in the cavity and air chamber, respectively, to urge the plug out of and into engagement with the valve seat, the ratio of the effective hydraulic area of the one side of the plug to the opposed side thereof being slightly greater than the ratio of the effective hydraulic area of the Cavity to that of the air chamber.

Claim 11

A controlled return, pneumatic die cushion for a power press, the cushion comprising an upright cylinder and piston having confronting surfaces defining the top and bottom walls of an air chamber, the cylinder being movable downwardly upon the piston under the force of a power press ram to reduce the volume of the air chamber, the piston and cylinder further having opposed, confronting surfaces defining the upper and lower walls of a cavity which expands in volume as the cylinder moves downwardly upon the piston and which retracts as the cylinder regains its initial heighth when the pressure of the ram of a press is removed, a source of air under substantially constant pressure communicating with the air chamber, and a decelerator valve carried by the cylinder and including a plug having one side in flow communication with the cavity and an opposed side in flow communication with the air chamber, the valve including a valve seat engageable by the one side of the plug, the opposed sides of the plug having effective hydraulic areas upon which act the pressures in the cavity and air chamber, respectively, to urge the plug out of and into engagement with the valve seat, the ratio of the effective hydraulic area of the one side of the plug to the opposed side thereof being slightly greater than the ratio of the effective hydraulic area of the Cavity to that of the air chamber.

Claim 12

The die cushion of claim 8 wherein the decelerator valve includes a spring gently urging the plug into engagement with valve seat, and an externally operable flow control valve communicating with the cavity for bleeding air continuously from the cavity to the atmosphere.

Claim 13

The die cushion of claim 8 wherein the piston includes an upright, stationary piston rod, a piston head at the upper end of the rod, and wherein the cylinder includes an upper strike plate, confronting surfaces of the strike plate and piston head defining the upper and lower walls of the air chamber, the piston rod and head having an air flow passage therein communicating the air chamber with an external source of air under substantially constant pressure, the cylinder including an annular plate spaced below the strike plate and extending inwardly into sliding contact with the piston rod below the piston head, confronting surfaces of the piston head and annular plate defining upper and lower walls of the cavity, the piston rod having at its lower end an outwardly extending baseplate with upright peripheral walls slidingly engaging the walls of the cylinder, confronting surfaces of the baseplate and annular plate respectively defining lower and upper walls of a second air chamber in flow communication with the first air chamber, the lower surfaces of the cylinder strike plate and annular plate each contributing to the effective hydraulic area against which the substantially constant air pressure acts to urge the cylinder upwardly.

Claim 14

A controlled return pneumatic die cushion for a power press, the cushion having an air chamber under substantially constant pressure for returning the die cushion upwardly to its original height following a press operation, the air chamber respectively contracting and expanding in volume as the cushion is decreased in height under the force of a power press ram and as the cushion recovers its original height when the force of the ram is removed, the cushion including a cavity which respectively expands and contracts in volume as the height of the cushion decreases and increases, air pressure within the cushion providing a force in opposition to the force provided by air pressure in the air chamber as the die cushion is returned upwardly to its original height, and a decelerator valve for bleeding air in a controlled manner from the cavity to control the rate at which the cushion returns to its original height, the valve communicating with the air chamber and the cavity and responsive substantially only to the ratio of cavity pressure to air chamber pressure to open when a given ratio of said pressures has been exceeded, said given ratio being such as to cause the valve to bleed air from the cavity so that the force resulting from the cavity pressure does not rise to balance the force resulting from the air chamber pressure, whereby the die cushion is decelerated in its upward movement to its original height.

Claim 15

A controlled return pneumatic die cushion for a power press, the cushion having an air chamber under substantially constant pressure for returning the die cushion upwardly to its original height following a press operation, the air chamber respectively contracting and expanding in volume as the cushion is decreased in height under the force of a power press ram and as the cushion recovers its original height when the force of the ram is removed, the cushion including a cavity which respectively expands and contracts in volume as the height of the cushion decreases and increases, air pressure within the cushion providing a force in opposition to the force provided by air pressure in the air chamber as the die cushion is returned upwardly to its original height, and a decelerator valve for bleeding air in a controlled manner from the cavity to control the rate at which the cushion returns to its original height, the valve communicating with the air chamber and the cavity and responsive substantially only to the ratio of cavity pressure to air chamber pressure to open when a given ratio of said pressures has been exceeded, said given ratio being such as to cause the valve to bleed air from the cavity so that the force resulting from the cavity pressure does not rise to balance the force resulting from the air chamber pressure, whereby the die cushion is decelerated in its upward movement to its original height.