Gate Safeguarding Device (Movable Barrier)

gate-a1


Introduction

Why use a gate device? According to the OSHA and ANSI standards, “operators must be prevented from inadvertently placing their hands or any other body parts in the point of operation during the die-closing portion of the press stroke.” The movable gate device uses a proven method of placing a physical barrier between the operator and the point-of-operation hazard during the die-closing portion of the press stroke.

Other advantages of gate devices include the following:

  1. Operators are not physically attached with wristlets to the machine as they are when using a pullback or restraint device. This means operator resistance is minimized because of the nonrestrictive design allowing more freedom of movement.
  2. These devices protect other employees in the machine area.
  3. A foot switch can be used to actuate the press. This minimizes stress to the hands and arms which can be caused by palm buttons.

Two types of gates are available. The first is a type A gate. It protects the operator during the entire machine cycle. This means the gate will not open until after the machine’s cycle is complete and stopped (usually in the up position). Type A gates are the only gates that should be used on full-revolution-clutch presses.

The second is a type B gate. It protects the operator during the downstroke only. The gate can open after the hazardous portion of the cycle has passed. Both type A and B gates can be used on part-revolution-clutch machines, hydraulic presses, and other cyclic machines where material is being manually fed.

Type A Gate Sequence of Operation

When the actuating means (palm buttons or foot switch) is operated, air pressure is released from the bottom of the gate-operating cylinder. This allows the gate to descend by gravity. Once the gate is fully down, a gate-down proximity switch senses this and the machine is allowed to make a cycle. If the gate cannot complete its downward travel, this gate-down proximity switch will not sense the gate and will prevent a machine cycle.

If the actuating means is released before the machine starts its cycle, the gate returns to the full open position with a type A gate. When the machine is actually making a cycle, air pressure is applied to the top of the gate-operating cylinder which holds the gate down and prevents it from being raised until the machine has completed its cycle. If the machine malfunctions and does not stop at the end of a normal cycle, the gate remains in the closed position.

According to ANSI, the gate must open after every cycle in order to reset the antirepeat system. If this does not happen, the machine will not make another stroke. To accomplish this, the gate control requires a signal from the machine at the open position. This signal is normally obtained from a photo-sensor or limit switch operated by a cam. Actuation of the limit switch is accomplished by the rotation of the crankshaft or any other member of the machine which makes one cycle or oscillates along one axis every stroke.

When a type A gate package is furnished for a full-revolution-clutch machine, the top-dead-center signal is provided by a limit switch assembly.

Type B Gate Sequence of Operation

The type B gate operates in a similar manner as the type A gate. When the actuating means (palm buttons or foot switch) is operated, air pressure is released from the bottom of the gate-operating cylinder. This allows the gate to descend by gravity. Once the gate is fully down, a gate-down proximity switch senses this and the machine is allowed to begin the cycle. If the gate cannot complete its downward travel, this gate-down proximity switch will not sense the gate and will prevent a machine cycle.

If the actuating means is released before the machine starts its cycle, the gate returns to the full open position. When the machine is actually making a cycle, air pressure is applied to the top of the gate-operating cylinder which holds the gate down and prevents it from being raised until the hazardous portion of the cycle has passed.

The gate must open every cycle in order to reset the antirepeat system. The sequence for this is the same as for the A gate described on the previous page.

OSHA and ANSI Requirements for Power Presses

The OSHA requirements for gate or movable barrier devices are located in 29 CFR 1910.217(c)(3)(i) as follows:
(c)(3)(i) Point-of-operation devices shall protect the operator by:
(f) Enclosing the point of operation before a press stroke can be initiated, and maintaining this closed condition until the motion of the slide has ceased; or
(g) Enclosing the point of operation before a press stroke can be initiated, so as to prevent an operator from reaching into the point of operation prior to die closure or prior to cessation of slide motion during the downward stroke.
(c)(3)(ii) A gate or movable barrier device shall protect the operator as follows:
(a) A Type A gate or movable barrier device shall protect the operator in the manner specified in paragraph (c)(3)(i)(f) (above) of this section, and
(b) A Type B gate or movable barrier device shall protect the operator in the manner specified in paragraph (c)(3)(i)(g) (above) of this section.

Note: OSHA states that the gate must enclose the point of operation. The gates illustrated are furnished as a single panel only, allowing access to the point of operation. Other guarding material is required to safeguard the sides and back of the point of operation. Complete the proper measurement form (page 47, 49, or 50) if these need to be supplied with the gate.

The ANSI requirements for gates or movable barrier devices are located in 8.6.6 of ANSI B11.1.
8.6.6 Movable Barrier Device
1) A movable barrier device, when used, shall enclose the point of operation before a press cycle (stroke) can be initiated.
2) The device shall prevent the individual from reaching the hazards associated with the point of operation by reaching over, under, around, or through the device when in the closed position.
3) In conjunction with the press control, the device shall actuate the clutch and initiate the press cycle (stroke).
4) The barrier shall be capable of being returned to the open position should it encounter an obstruction prior to enclosing the point of operation.
5) The device shall require opening of the barrier to reset the antirepeat system of the press production system every time the press stops before a successive cycle (stroke) can be initiated.
6) The device shall be in compliance with 6.11 and 8.8.
7) The device shall provide visibility to the point of operation when necessary for safe operation of the press production system.
8) The device in and of itself shall not create a hazard to the operator or others.
8.6.6.1 Type A movable barrier device
1) A type A movable barrier device, when used, shall protect the individuals as specified in 8.6.1 (e).
2) The type A movable barrier device shall, in normal single-cycle operation, be designed to hold in the closed position until the slide has completed its cycle (stroke) and has stopped at top of cycle (stroke).
8.6.6.2 Type B movable barrier device
1) A type B movable barrier device shall protect the individuals as specified in 8.6.1 (f).
2) The device shall not be used on full-revolution-clutch presses.
3) The device shall, in normal, single-stroke operation, be designed to hold in a closed position during the closing portion of the cycle (stroke), or until cessation of slide motion during the closing portion of the cycle (stroke).
4) When the protection of the operator is dependent upon the stopping action of the press, a stopping-performance monitor shall be required in conformance with 6.12.

GATE ASSEMBLIES

Basic Gate Assembly (Without Side or Rear Safeguarding)

Basic Gate Assembly
(Without Side or Rear
Safeguarding)

Gate Construction

The panel framework of these gates is constructed of 1″ x 2″ extruded aluminum which slides up and down on roller bearings in a rail extrusion. The panel of the gate is furnished with either clear polycarbonate (3⁄16″-thick) or an adjustable lower section.

The standard gate assembly is furnished with hinges allowing it to swing open. A button-head cap screw on a locking plate holds the gate in place. This feature is useful when changing dies or working on dies in the machine.

The gate assembly can be furnished with side guards. The gate and side panel can be swung open to the left when changing dies. A dead-bolt latch is located on the right extrusion. When side guards are furnished, this latch releases the gate so it can be swung completely open.

These gates are easily mounted on the bolster of the machine or on a special plate or bracket on the front of the machine.

The gate assemblies listed are designed for a variety of machines, including full-revolution-clutch presses. Side guards are also required when using a gate. Gates are made according to the measurements submitted. Please complete the appropriate measurement form for a complete assembly. (links here for forms)

Gate Assembly Components

  • Gate frame assembly
  • Gate panel
  • Proximity switch (24 V DC only) or limit switch
  • Air cylinder(s)
  • Quick dump valves
  • Air flow control valves
  • Solenoid air valve assemblies
  • 1⁄8″ air regulator gauge and mounting bracket
  • Extrusion, hinge assembly, and mounting hardware

Pricing/Ordering Information

The following information is required prior to ordering or pricing a gate assembly:

1. Choose a gate lift height of either 12″ or 18″ (other lift heights are available)
2. Provide gate’s outside dimensions in height and width

OR

Provide gate’s inside opening dimensions in height and width

Gate Device Measurement Fillable Forms

Download and email the completed measurement form based on your application to sales@rockfordsystems.com:

For full-revolution-clutch presses, part-revolution-clutch presses, or hydraulic presses with a gate interface, call our sales department at 1-800-922-7533 or contact us.