Electrical pulse counters – pulse dividers – or shift registers: c – Applications – Counting animate or inanimate entities
Patent
1997-09-03
1999-01-12
Wambach, Margaret Rose
Electrical pulse counters, pulse dividers, or shift registers: c
Applications
Counting animate or inanimate entities
G06M 700
Patent
active
058598898
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of setting-up a sheet counter, intended in particular--but not exclusively--for counting sheets of paper.
A known form of sheet counter, primarily intended for counting sheets of paper such as bank-notes, has an elongate element which is inserted into the corner region of a stack of paper sheets, the element having on one side a port which is connected back to a low (sub-atmospheric) pressure source. An elongate member having its axis substantially parallel to that of the element orbits around the latter and serves to transfer the corner regions of sheets, one at a time, from one side of the element to the other. The corner region of the next-to-be-counted sheet of paper in the stack is lifted from the stack by air drawn through the port until that sheet rests on that element and closes off the port. The element is moved through an acute angle to open a gap for the elongate member, orbiting round the element, to pass between that sheet and the remainder of the stack and then to transfer that sheet to the other side of the element.
A pressure sensor is disposed to sense the pressure in the duct leading to the port, as close as possible to that port in order to allow the generation of a count signal. Each time the port is closed off, the pressure in the duct falls significantly below atmospheric pressure, and that pressure fall is detected and used to produce a count signal. In order to reduce the likelihood of an erroneous count, often the count signal resulting from the sensing of the pressure is combined with a position signal, so that a valid count will be generated only if a pressure change is detected at the time a sheet should close the suction port.
Unfortunately, counting errors sometimes occur in sheet counters as described above, on account of significant pressure fluctuations which may arise in the low pressure source. Also, a significant change in atmospheric pressure can affect count reliability. This leads to a requirement to calibrate the equipment from time to time, and also when it is first installed, especially if the equipment is installed at some geographically elevated site.
In EP-A-0 616 300 there is described a sheet counter of a generally similar kind to that described above and which dynamically can adjust a counting threshold as a counting operation proceeds. Specifically, it suggests that the count threshold should be dynamically set as a proportion of a rolling average of a predetermined number of vacuum levels obtained on previous count cycles. This method has the disadvantage that a counting operation must be commenced before an accurate threshold can be set up, by which time there might already have been one or more miscounts.
It is an aim of the present invention to provide a method of setting-up a sheet counter having an element including a port through which air is drawn during operation of the counter, the port being closed by the sheets being counted, one at a time, which method allows greater counting reliability notwithstanding local variations in the operating conditions.
According to the present invention there is provided a method of setting-up a sheet counter before the commencement of a counting operation, which counter includes an element having a suction port over which the sheets to be counted are caused to lie in sequence one after another, a source of sub-atmospheric pressure connected by a duct to the port, and means to sense the pressure within the duct in the vicinity of the port which sensing means provides an electrical signal indicative of sensed pressure, in which method the port is left open and the pressure in the duct is sensed to obtain a first pressure, either before said source is operated to draw air through the port or after operation of said source has commenced; the source is operated and the port in the element is covered whereafter the pressure in the duct is sensed again to obtain a second pressure; and a count pressure value part-way between the first and second pressures is computed, a valid count signal
REFERENCES:
patent: 5454017 (1995-09-01), Price et al.
patent: 5612984 (1997-03-01), Fuller et al.
Pelcombe Limited
Wambach Margaret Rose
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