FAIL-SAFE DOUBLE-ACTION SAFETY GUARD

• US 3,554,067 A
• Filed: 02/26/1969
• Issued: 01/12/1971
• Est. Priority Date: 02/26/1969
• Status: Expired due to Term

• Current Assignee: Scutella Joseph
• Original Assignee: Scutella Joseph
• Inventors: SCUTELLA JOSEPH
• Application Number:
  US04/802,346
• Time in Patent Office: 685 Days
• US Class Current: 83/397
• CPC Class Codes: F16P 1/04 Screens or hoods rotating with rotary shafts
• CPC Class Codes: F16P 3/02 Screens or other safety members moving in synchronism with members which move to and fro
• CPC Class Codes: Y10T 83/606 Interrelated tool actuating means and guard means

Abstract

A fail-safe, double-action safety guard having two separate and distinct protective circuits, shown installed on a treadle operated punch press, the primary circuit being both pneumatically and electrically operated, while the secondary or followup circuit is hydraulically operated. Actuation of the foot treadle will open the pneumatic circuit to a preset flow control circuit and also to an air solenoid valve. From the flow control circuit, air pressure passes through and operates a pneumatic drive cylinder which in turn drives a guard-actuating device or butterfly flipper having a guard shield attached thereto. The butterfly flipper is rotated a preset amount to drive the guard shield in front of the work area. Only when the guard shield is completely in front of the work area, an electrical off/on switch is operated which in turn actuates an air solenoid and releases line air pressure to the clutch trip cylinder which trips the press. To operate the followup hydraulic circuit, a preset cam throw is mounted on the crankshaft of the press. When the press is tripped and the ram starts its downward stroke, the cam positively drives a hydraulic cylinder. This cylinder is connected via hydraulic lines to a second hydraulic cylinder which is mounted next to the guard-actuating device or butterfly flipper diagonally opposite the pneumatic drive cylinder, the length of the stroke of the second hydraulic cylinder and the pneumatic drive cylinder being equal. Before the ram has completed a minor fraction of its downward stroke, the second hydraulic cylinder is completely activated against the butterfly flipper. In normal operation, the hydraulic cylinder merely follows the pneumatic cylinder and butterfly flipper action. It is a positive drive but only drives the guard shield in any emergency operation such as a double tripping of the press, or a clutch, air pressure, spring, electrical or air solenoid valve failure. The positive hydraulic drive exerts a large force that may be as great as the punch press, however, and in both normal and unexpected operations, this force cannot easily be overcome by the operator. When the stroke of the second hydraulic cylinder is fully extended to the butterfly flipper, it holds the guard shield in front of the work area until the ram has completed its downward stroke and has started its upward stroke. Meanwhile, the pneumatic drive cylinder retracts and is ready for the next cycle. Desirably the guard shield is opened by means of a return spring and the work area is cleared and made ready for the next cycle of the press.

Claims

1. A fail-safe double-action safety guard mechanism for a punch press having a reciprocable ram and a treadle for effecting the operation of said ram, said mechanism comprising a guard mechanism, a flow control circuit, a first pneumatic actuator for moving said guard to a guarding position and a second hydraulic actuator for positively driving said guard to said guarding position, said treadle means including a control valve interconnecting a source of fluid under pressure to said first actuator and to said flow control circuit, said flow control circuit comprising a control valve having resilient means for actuating said control valve to a first position for directing fluid into said first actuator to effect the movement of said guard to said guarding position, said resilient means being operable to move said control valve to a second position to exhaust fluid and effect the movement of said first actuator to its retracted position.

2. The guard mechanism of claim 1 wherein said flow control circuit includes first and second regulating valves interconnecting said control valve, first actuator and said source of fluid, said first and said second valves being normally open to effect the actuation of said control valve to said first and second positions responsive to said treadle and independently of the movement of said ram.

3. The guard mechanism of claim 2 wherein said first valve comprises a housing having a spring-biased diaphragm member for regulating flowing fluid by reducing the pressure thereof, said first valve being adapted to supply fluid at reduced pressure to said control valve.

4. The guard mechanism of claim 2 wherein said second valve comprises a housing having a flow pressure-regulating needle valve and a flow direction-regulating spring biased ball valve for restricting and delaying the flow of fluid to said control valve, responsive to fluid flow from said first valve.

5. The guard mechanism of claim 1 wherein said control valve comprises a housing having a reduced fluid pressure inlet port, a delayed fluid pressure inlet port, a first actuator fluid pressure outlet port, an exhaust port and an internal chamber for receiving an an internal valve means, said internal chamber including opposed chamfered sealing surfaces within said housing, said internal valve means having opposed chamfered portions thereon for coacting with said chamfered sealing surfaces, and a resilient means biasing said internal valve means, said internal valve means normally permitting reduced fluid pressure to pass therethrough and to said first pneumatic actuator, the flow of delayed fluid pressure to said internal valve means gradually overcoming the resistance of said resilient biasing means to thereby close said internal valve means and permit fluid to exhaust therethrough.

6. The guard mechanism of claim 1 wherein said guard mechanism is rotatably mounted and is provided with upper and lower pressure faces for actuation of said guard member responsive to said first and second actuators, respectively.

7. The guard mechanism of claim 1 including an electrical switch means, and a pneumatic solenoid means, said first actuator being adapted to actuate said electrical switch means, said electrical switch in turn being adapted to actuate said pneumatic solenoid for operating said punch press.

8. The guard mechanism of claim 1 wherein said second hydraulic actuator comprises a first ram driven hydraulic cylinder and a second hydraulic driving cylinder operatively connected to said first hydraulic cylinder responsive to the movement thereof, the movement of said ram driving said first and second hydraulic cylinders to thereby positively drive said guard mechanism.