Abstract: A rigid drive assembly is constructed of two interconnected, flexible chain elements.

Abstract: A telescoping mast assembly includes a plurality of interconnected mast sections nested within each other for movement between a fully retracted height and a fully extended height. A novel, rigid drive assembly, disposed within the interconnected mast sections, telescopes the mast sections to any position between the fully retracted and the fully extended heights. The rigid drive assembly is constructed of two interconnected, flexible chain elements which accurately position the interconnected mast sections.

Abstract: The mast has a housing arranged to be mounted on the roof of a vehicle such as an emergency vehicle at the usual location of a vehicle light bar, whether or not a light bar is associated with the mast housing. A seal unit is located at the lower end of each telescoping mast section engaging the next outer mast section. The seal unit leaves the lower end of all mast sections unobstructed so that a tubular passage is formed from end to end of the mast. A retractable power supply cable is located in the passage of supply power to the electrical appliance mounted on the top of the mast. There are electrical plug connectors at each end of the mast for releasable connection with the electrical fixture at the top and with the vehicle power supply at the bottom of the mast. The mast is mounted on an offset pivot which simplifies the pneumatic-actuating system which tilts and telescopes the mast, and also enables the mast to tilt by gravity from telescoped retracted vertical to stored horizontal position.

Abstract: A safety device for power driven equipment which mechanically locks an access door on the equipment in closed position until the power drive motor has coasted to a stop. A manually operated locking bolt for the access door is pivotally mounted on a housing in which the control components for the safety device are contained. A locking plate is rigidly mounted on the pivot shaft of the locking bolt within the housing for movement with the shaft and bolt. A solenoid operated locking lever is pivotally mounted in the housing and is engageable with the locking plate when the solenoid is energized to prevent movement of the locking bolt from its door locking position. A bolt mounted on the locking plate actuates a switch which is electrically connected in the drive motor control circuit to open the circuit when the lock bolt moves to an unlocked position.