Keeping it shut
December 1st 2004 Designer safety switch aids machine downsizing, while improving safety with high force interlocking.
All the key designer benefits of small size, high holding force and robust metal construction are provided by Guardmaster’s new 440G-MT, solenoidlocking switch. The 440G-MT is a new generation safety device that enables designers to respond positively to the pressures of downsizing with modern machinery. At the same time it provides improved safety provision with a substantial and highly robust 1600N of holding force to ensure that guard doors stay firmly shut until machine power is isolated - even under physical abuse, and over the lifetime of the switch.
The slim design of the 440G-MT (to DIN 500491), together with its flexibility for eight actuator entry positions, enables the new safety interlock to be mounted on most designs of guards, even in tight spaces. Moreover, the combination of the 440G-MT’s robust metal body and its flexible actuator – which is highly tolerant to the effects of guard wear, mean that it is the ideal device for use in a widest range of operating environments, including arduous ones where lower temperatures (down to –250C) and external atmospheric conditions are encountered. The metal construction ensures high resistance to hot metal chips in such applications as metal cutting, while providing a high degree of dimensional stability, often an issue with plastic-bodied switches.
With its extremely high holding force and repeatable tolerance to abuse, the GM 440G-MT provides a solution across a greater range of applications where higher actuator holding forces are required. For the designer and OEM this means a reduction in inventory as only a single type of switch, rather than a range of switches need be stocked.
Also aiding stock reduction, the in-line symmetrical head design of the 440G-MT means that the safety interlock can be used on both left and right handed guard door applications. In contrast, competitive units without this feature may require several discrete handed versions to be stocked.
The 440G-MT is available in four basic versions providing the OEM with the maximum choice of contact configurations, including optional key release if required.
Standard across all these versions is the facility for operation in high risk applications, the 440G-MT being designed with 4 sets of contacts, which can be configured in a number of ways: 4NC, 3NC 1NO or 2NC 2NO.
These contact options provide great flexibility to the OEM as, once again, they can reduce the number and type of safety switches required on a machine. In addition, they are also part of an electrical installation package that makes the 440G-MT easy to install. The second element in the package is a choice of conduit entry options, which allow cable entry on either side of the safety interlock, or at the end of the unit. These include M20 or ” NPT to cover geographic preferences.
In addition, where fast replacement or ease of installation is an issue, all versions are available with quick disconnect options.
All versions of the 440G-MT conform to standards EN 1088, EN 60947-5-1, and IEC 60204 –1, and hold TUV, UL and CSA approvals. The interlocks are suitable for operation on 24V (AC & DC), 110V AC and 230V AC supplies and are rated for operation in the temperature range –250C to +800C More articles from EJA Ltd (Guardmaster): | 
