Safety is a prime consideration when specifying operators for both commercial and domestic garage doors, as clearly such doors are extremely heavy and have the potential to cause significant injury if components fail to limit the speed and travel of their movement. The UL specification that relates to garage door operators, UL325, now covers operators for both domestic garage doors (Class I regulations) and commercial garage doors (Class II regulations). In both instances, the primary sensing devices used must satisfy regulations for inherent entrapment sensing which includes current sensing, zero speed or equivalent, meaning a maximum door travel speed of one foot per second.
Secondary devices are also required as backup and must have provision for - or be supplied with - a photoelectric sensor, a contact sensor or an actuating device requiring continuous pressure to maintain the opening or closing motion of the door. ZF Electronics designs and manufactures a range of Cherry brand switches and sensors which meet or exceed UL standards, are economical and yet robust enough to suit demanding environments and withstand repeated operation.
In the case of commercial garage door operators, many customers use paired Cherry miniature D4 switches as limit switches in the operator to increase and decrease door travel. These versatile snap switches are highly reliable, operating over an ambient temperature range of -40degC to +150degC. They feature high contact stability and are available with various auxiliary actuators and mounting points. They fulfill the requirements of IEC603351 and are EN61058 and UL1054 approved.
As an alternative, some customers specify Cherry’s new GP series heavy-duty snap action switch, which has ultra-small travel differential and a mechanical life tested to 1 million cycles. Available in a wide variety of actuator styles, GP series switches provide current switching to 20A and are rated to UL1054.
ZF Electronics’ new Cherry GS1001/GS1002 and GS1012 series geartooth speed sensors are also well suited to OEM requirements for garage door operators, as they are immune to rotational alignment and accurately sense the movement of ferrous geartooth targets down to near zero speed. 10-bit dynamic threshold detection means that these sensors automatically adjust their magnetic range and compensate for changes in target geometry, as well as being immune to target run out. GS1001-1002 Hall-effect geartooth speed sensors are circuit-protected and available with an adjustable stainless steel housing.
Cherry GS1012 series flange-mount geartooth speed sensors are resistant to fuels, solvents and lubricants, so are particularly suited to commercial doors for harsh commercial environments, such as automotive engineering workshops. Rated to 150degC, the new Cherry GS1012 flange mount gear sensor’s sealed design exceeds IEC60529 IP67 for fluid immersion.