Abstract: A swivel caster includes a swivel assembly having a swivel plate configured to be mounted to a vehicle and defining a swivel axis. A horn depends downwardly from the swivel assembly and a wheel is wheel coupled to the horn with a wheel axle. A slide mechanism couples the horn to the swivel assembly and enables the wheel to slide in a direction generally perpendicular to the swivel axis between first and second trailing positions. The slide mechanism swivels with the horn, the wheel, and the swivel plate about the swivel axis. A swivel limiter is operatively associated with the swivel assembly and limits a swiveling range of the wheel about the swivel axis so as to activate the slide mechanism to reposition the wheel from the first trailing position to the second trailing position when a direction of travel of the vehicle changes.

Abstract: A system is provided for easily replacing a single tube in shell and tube heat exchangers without removing the bundle. The system comprises: (1) a rod which is inserted into the tube to be replaced and left in place when the tube is removed and (2) a special tool which is adapted to fit into the end of a replacement tube and over the rod.

Abstract: In a communication network wherein a master station periodically polls a number of remote stations to determine whether or not each remote station has data to transmit to the master, each of the remote stations is assigned to one two groups. One of the groups is designated as priority stations which commonly have very urgent data for the master station. The group of non-priority stations is sequentially polled for messages to be sent to the master station. The polling of the group of non-priority stations is periodically interrupted so that the master station may poll each of the stations in the priority group to determine if they have messages to send. Upon the completion of the polling of the priority stations, the polling of the non-priority stations is resumed. Periodically a time period occurs for inactive stations to join one of the two groups of stations on the network.

Abstract: A programmable controller is adapted to communicate in a token passing logical ring network in a peer-to-peer fashion. The programmable controller is a station on the network and contains an interface which implements the network protocol. The protocol requires that each station maintain an Active Node Table which stores a complete map of the logical ring and the order in which the token is passed. The Active Node Table is automatically updated by monitoring each token pass on the network, where each token pass identifies the source and destination of the token pass. The Active Node Table is used in performing all routine network maintenance functions, including passing the token, adding stations, and dropping stations. The Active Node Table allows the formation of an Active Node Status Word for use by high level processes within the station. The Active Node Table also facilitates the inclusion of data in the token pass message.