Command Devices with Safety in Mind

To protect operators from hazards, machine guarding such as fences, covers and gates are commonly put into place. Safety rated limit switches, interlock switches and non contact sensors are used to detect opening of these guards to initiate a safe shutdown. Safety pressure mats and light curtains can also be used to detect if a perimeter or hazard point has been breached.

In real world applications operator interactions with machinery are often frequent and hands-on. There may be instances an operator may need to perform procedures such as tool adjustments while a machine is running at controlled speeds. Or instances when pinch points cannot be guarded, only avoided by requiring the operator to use two hands to initiate a machine cycle. To accomplish such tasks command devices are used in conjunction with safeguarding as a secondary protection component to create a fluid production and manufacturing process.

Command, or non-separating, devices can be categorized as two types: localized such as two-hand control or emergency stop stations; and movable such as handheld enabling devices. Because command devices are often used at high demand and during live machine operations, not only must they meet safety standards but ergonomic requirements as well. For example, the industrial robotic ANSI/RIA R15.06 standard calls for an enabling switch to operate in an off-on-off sequence as test have proven that human reactions to emergencies are to either release or hold tighter. OSHA 1910.217 requires that two hand control stations be designed in such a way that concurrent use of both hands is required to trip the press.

Installing hard guards or presence sensing devices are only part of the task when it comes to safeguarding. Command devices can allow an operator to safely perform a task or interact with the equipment during setup, maintenance or manual modes. To accompany our vast line of safety devices Schmersal offers a line of command devices designed to meet the industry standards, harsh environments, and the operators comfort.

The TFH Safety Foot Switch from Schmersal utilizes a three stage operation — the switch contacts engage when the foot pedal is depressed to a mid-point, but will disengage when released or when fully depressed. It is typically used in applications where interaction between the operator and machine is required. More»

Designed with a similar 3 stage operation, the hand-held ZSD Enabling Device allows operation of the machine when the trigger is depressed to a mid point. Releasing or squeezing the handle will cause machine stoppage. This enabling device allows operator to observe machine operation from a short distance. More»

The Series BDF control station provides operators and maintenance personnel with the ability to E-Stop, control start up, reset and select the appropriate mode of machine operation in a single housing. Each control station has up to four positions for a wide variety of controls: E-Stop buttons, pushbuttons, mushroom buttons, illuminated pushbuttons, LED indicator lights, selector switches, and key selector switches. More»

Two-hand control consoles are designed to require machine operators to use both hands to initiate a machine control action to insure that the operator's hands are kept away from the hazardous area of a machine during operation. Applications are typically found in the metal working, rubber, plastics and chemical industries as well as in semi-automatic assembly equipment. More»

The TG door handle does more than just open the guard door. It has an integrated enabling pushbutton to initiate a controlled machine shutdown and release a solenoid latched interlock switch. Integrated LEDs indicate the door’s locked status. These door handles can also be outfitted with an E-stop button and/or a start button. More»

E-Stop Station: ADRR

Schmersal offers a cost effective solution to safely emergency stop machinery. The ADRR 40 RT E-Stop pushbutton is designed to meet industry standards such as EN ISO 13850 and NFPA 79. This thermo-plastic E-Stop can actuate Up to 6 contacts at once. Installation can be done through a standard 22mm mounting hole or with a robust enclosure offered in both metal and plastic. More»

ASK THE EXPERT:

Why shouldn’t I use a standard momentary pushbutton as an enabling device?

Extensive accident prevention research has shown that in the event of pain/distress, the natural human reaction is frequently not to let go of an enabling device. Paradoxically, pressure is often applied thus compressing the enabling de-vice. As a result, industry standards such as ANSI/RIA R15.06 call for an enabling device to feature an OFF-ON-OFF configuration so that a machine/robot is only operational while the device is in the middle (“on”) position. Releasing the switch (position 1) or squeezing the switch (position 3) shuts down the equipment.