Use of OPTO-TOUCH Optical Touch Buttons for Two-hand Machine Trip Controls

Requirements for Anti-tiedown Circuitry

Two-hand trip control has been a popular means for actuation of single-stroke presses

and other single-cycle machinery for many years. Optical touch buttons (OTBs)

provide an ergonomic (stress-free) alternative to conventional mechanical push buttons

used as actuators in two-hand trip controls.

OSHA Requirement for Anti-tiedown Control

Use of OTBs for two-hand trip machine actuation must include "anti-tiedown"

control to prevent any means of defeating one or both actuators to create a one-hand

trip. Federal law mandates the use of anti-tiedown control when two-hand trip actuators

are used for cycle initiation of a single stroke part revolution clutched mechanical power

press. OSHA Code of Federal Regulation, 7-1-92 Edition, CFR Title 29, Part 1910.217

(b) (6) (i) states:

"A two-hand trip shall have the individual operator’s hand controls protected against unintentional

operation and have the individual operator’s hand controls arranged by design and construction

and/or separation to require the use of both hands to trip the press and use a control arrangement

requiring concurrent operation of the individual operator’s hand controls."

Concurrent or "synchronous" actuation of two-hand trips is the most popular approach to anti-tiedown control. European

Standard prEN 574, titled "Safety of Machinery - Two-handed Control Device", defines synchronous actuation as follows:

"6.7 Synchronous actuations

In synchronous actuation an output signal shall be generated only when both control actuating

devices are actuated - in a time which is less than or equal to 0.5 seconds...

... If the control actuating devices are not actuated synchronously the output signal shall be

prevented and it shall be necessary to release both control actuating devices and to reinitiate

both input signals."

Important Application Information

NOTE: In addition to the standards and regulations mentioned above, there are numerous regulations and machine safety

standards that apply to specific industries. For assistance in obtaining copies of any of these standards, contact Banner

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WARNING !

In the United States, the functions that a two-hand control device is intended to perform are regulated by the

Occupational Safety and Health Administration (OSHA). Whether or not any particular two-hand control

system installation meets all applicable OSHA requirements depends upon the details of how the two-hand

control device is applied, installed, operated, and maintained.

When properly installed, a two-hand control device using OPTO-TOUCH OTB Series Optical Touch Buttons can provide

protection only for the hands of the machine operator, and is not a point of operation personnel guarding device, as defined

by OSHA regulations. It is necessary to install point of operation guarding devices, such as safety light curtains and/or hard

guards, to protect personnel from dangerous machine motion.

WARNING!

Never use an OPTO-TOUCH Optical Touch Button as an actuator in an emergency stop (E-Stop)

circuit. E-Stop actuators must be purely mechanical devices that require no power to operate. OPTO-

TOUCH Optical Touch Buttons require power to operate and must not be used as E-Stop actuators under

any circumstances.