Patent GB-904217-A (GB)
Title: Linear dimension gauge
Inventor: PERTHEN JOHANNES
IPC: G01B3/22
Filed: 1958-09-12
Abstract: 904,217. Measuring linear dimensions. PERTHEN, J. Sept. 12, 1958, No. 29278/58. Class 40 (1). [Also in Group XIX] A linear dimension gauge comprising a feeler for sensing individual articles or objects to be measured and for controlling the pointer of a dial indicating the result of the measurement has a releasable locking device for holding the pointer at an article-measuring point on the dial until the feeler is placed against another article, thereby preventing the pointer from returning to starting position between successive gauge readings. Fig. 6 shows a purely electronic embodiment, movement of the feeler 2 being sensed by a capacitance effect which produces an appropriate voltage on the terminals 22a, 22b of an amplifier 21. These terminals are connected through switches S 3 , S 4  to condensers C 1 , C 2 , the charge on which is indicated as a voltage on the tube-voltmeter 23, 24. If the switches S 3 , S 4  are then opened, the pointer of the voltmeter 24 remains stationary until the condensers C 1 , C 2  are discharged by closing switches S 5 , S 6 . The circuit shown operates semi-automatically to hold the reading until the next measurement is taken or until the condenser C 5  is charged up sufficiently through a variable resistance R 6  to trigger off a flow of current through a relay 26 thus opening the switches S 5 , S 6 . This latter period can be set at any time between 1 minute and 5 minutes. The only manual operation involved is the tipping of a switch 29 to the right to discharge the condensers C 3 , C 4 , C 5 , C 6  and stop current flowing in the electromagnet 28, thus allowing the feeler 2 to fall on to the article 1 to be tested, switch 29 returning automatically to the position shown. By this means, the pointer of the instrument does not return to zero between each measurement and this is stated to be less tiring to the operator. Figs. 9 and 10 (not shown), illustrate another embodiment, the principle of operation of which is the same as that described above, but which can be used for fully automatic measurement of a series of workpieces. In this case, the workpieces are rolled under the feeler 2 and movement of the feeler controls the complete operation of the electronic circuits, by variation of an inductance and not a capacitance as in the previous embodiment. Movement of the feeler can also be used to vary a resistance. In this embodiment, the indication of the size of a workpiece is not given until the feeler is moving over the next one. In both these examples, electronic switches with valves or transistors can be used in place of the electromechanical relays. The device can also be used to control sorting apparatus, in which case, a number of condensers C 1  &c. are provided, each operatively connected with one position on the conveyer carrying the articles, and the compartments into which the articles are sorted are each controlled by a tube-voltmeter selected to respond to a specific voltage. Thus, each article is sorted according to the charge carried by the appropriate condenser, which is discharged before being used for a further measuring operation. It is also possible, instead of using symmetricallyarranged condensers, to earth one terminal 22b (say) and connect the other to a single condenser C 1 . The other condenser C 2  can then be used to compensate for internal disturbances in the tube 23. In other embodiments, Figs. 4 and 5 (not shown), movements of the feeler can be converted into a corresponding electrical current or voltage, indicated by an ammeter or voltmeter the feeler of which can be mechanically locked. Alternatively, a crossed coil indicating instrument without a restoring spring may be used, one coil being connected to the varying voltage or current and the other to a constant voltage source, locking being achieved by breaking the circuits to each coil simultaneously.