Abstract: A pneumatic rockdrill having a housing; a cylinder connected to a compressed air supply inlet by a set of air passages; an impact piston, at least part of which is reciprocable within the cylinder; and a controller for the supply of compressed air from the air supply inlet to the cylinder. At least one pair of contact surfaces are located at the interface between the piston and the cylinder, where those relatively moving parts contact one another. At least one water supply inlet and water paths connected to the water supply inlet(s) are configured so as in operation to convey water to a drilling tool to flush a hole being drilled, and to supply water to wet the contact surfaces.

Abstract: A software logic controller using flowchart programming includes exception handling elements for handling exception conditions in a manufacturing process. Exception handling is programmed using a Begin Exception element to start monitoring the occurrence of a specific exception condition and an End Exception element to stop the monitoring process. Monitoring is conducted once during every scan cycle of the computer as long as the Begin Exception element is still active.

Abstract: An MWE compressor comprising a housing defining an inlet and an outlet, and an impeller wheel rotatably mounted in the housing such that on rotation of the wheel gas within the inlet is moved to the outlet. The housing has an inner wall defining a surface located in close proximity to radially outer edges of vanes supported by the wheel. The inlet is defined by a first tubular portion an inner surface of which is an extension of the said surface of the inner wall of the housing, a second tubular portion located radially outside the first portion to define an annular passage between the first and second portions, a wall extending across the annular passage between the first and second portions, and a conical wall located upstream of the first portion and extending in the radially outwards and upstream directions from adjacent the upstream end of the first portion to the upstream end of the second portion.

Abstract: A digital communication network carries high and low priority data. The network stations that produce high priority data are assigned to a first group of stations and stations that produce low priority data are assigned to a second group with the two group not being mutually exclusive. Activity on the network is divided into periodic intervals of the same duration. Network control information, that defines how access to the medium, is determined is broadcast to all stations during a first segment of a periodic interval. The network control information defines the length of the periodic interval and of the periodic interval segments, and defines how many stations are in each group. Then during a second segment of the periodic interval, every station in the first group is afforded an opportunity, in a predefined order, to transmit high priority data over the medium.

Abstract: Activity on a digital communication network is divided into periodic intervals and during a segment of each periodic interval a moderator station broadcasts a numerical count of the periodic intervals to all stations on the network. Each station has a memory in which a numerical value is stored, and a comparator that compares the numerical value to the numerical count received from the network. When the numerical count of the periodic intervals equals the numerical value, an apparatus within the station performs a defined operation, such as transmitting a message over the network or synchronizing a clock in the station to a master time standard. The equality of the periodic interval count and the numerical value also can be used to determine when to signal an external device. By using the count of the periodic intervals in this manner, the operation of several stations on the network can be coordinated.

Abstract: A node circuit is operative to couple Manchester encoded data between a transmission medium and an associated electrical device. A first mechanism detects a message frame preamble having a pattern of alternating signal level of substantially identical duration, and a second mechanism that detects a start delimiter in the message frame. The start delimiter has a plurality of binary signal levels in a unique pattern that satisfies a defined set of criteria to optimize the probability that the pattern will be detected while minimizing the likelihood that random valid data will alias into the start delimiter pattern. A data decoder is provided to convert the Manchester encoded data into binary data which then is sent via a signal path to the associated electrical device. Another mechanism is included to detect a unique end delimiter that signals the termination of the message frame.

Abstract: A moderator on a communication network periodically transmits a set of parameters for a protocol that is used to communicate over the network. Each node on the network compares the set of protocol parameters from the moderator to a set of parameters stored in that node. If the sets of parameters at a given node do not match, that given node ceases transmitting messages over the network until either the set of protocol parameters from the moderator match the stored set of parameters, or a matching set of parameters is stored in the node. Typically the active node that is assigned the lowest numerical network address functions as the moderator. However, an automatic process is utilized to prevent a node with a non-matching set of the protocol parameters from becoming the moderator for more than a brief period of time. An override procedure is provided to force all the nodes on the network to adopt a common set of protocol parameters in the event that the automatic process fails.

Abstract: Each message carried by a communication network has a packet that contains data, a tag, and a generation count wherein duplicate packets sent in different messages have identical generation counts. A station includes a modem that connects to the communication network in order to receive messages. A fixed screener circuit has a first memory that stores a set of tag values and a fixed screener determines when a packet tag matches a tag value in the first memory. The station also has an interface through which tag values are received from an external device, such as a host computer. A general purpose screener includes a second memory with a plurality of storage locations in which to store tag values from the interface and a generation count associated with each tag value.

Abstract: An apparatus and method for tool condition and failure monitoring system for predicting imminent tool failure by sensing acoustic emissions from a cutting operation converting the emissions into an electrical signal filtering the electrical signal and using a "count rate" technique on the filtered signal to generate a signal indicative of imminent failure. To improve the prediction, the filtering includes removal of low frequency and d.c. signals and the imminent failure is indicated only after several successive periods of a triggering level of count rate.