US2867798A - Generators for producing pulses of alternating current - Google Patents

Description

Jan. 6, 1959 J. H. COQUELET 2,867,798

GENERATORS FOR PRODUCING PULSES OF ALTERNATING CURRENT Filed April 25, 1955 P2 M p cwvreox. flew/r5. .i 532L 25? G-A/A705 GENERATORS FOR PRODUCING PULSES OF ALTERNATING CURRENT Jules Hector Coquelet, Jamioulx, Belgium, assignor to Atelirs de Constructions Electriques de Charleroi, Brussels, Belgium, a Belgian company Application April 25, 1955, Serial No. 503,505 'Claims priority, application France May 18, 1954 3 Claims. (Cl. 340359) This invention relates to generators for producing short pulses of alternating current, and particularly to generators of the type in which the current is generated in a coil associated with a vibrating blade in a magnetic circuit.

The vibrating blade may be fixed at one end to the magnetic circuit with the other end of the blade left free to vibrate in a gap of the magnetic circuit. The blade preferably is held in a deflected position and then suddenly released to vibrate freely and thus produce a pulse of alternating current. If the blade is released by a pawl operated by levers or other means in such a way that the blade begins to move at the same time as the lever or other operating means, then certain drawbacks occur. Particularly, the release of the blade is not sufliciently abrupt and uniform. This results in non-uniform pulses having considerable variations in shape and duration. In order to obviate this drawback it is important to release the blade sharply and precisely every time, and this is one of the objects of the invention.

The foregoing object is attained according to one exemplary embodiment of the invention by maintaining the blade in a deflected condition under the action of a springbiased lever, and then releasing the blade by a sharp impact on the lever by a plunger core of an electromagnet, which core strikes the lever only at the end of its stroke.

Another object of the invention is to make possible a precise control of the amplitude of the pulse. This object is accomplished by providing the electromagnet with an abutment screw against which the lever rests. Adjustment of the screw continuously varies the initial deflection of the blade and hence the amplitude of the generated current.

A further object of the invention is to generate pulses of which the first oscillation is of maximum amplitude so that the rise time or build-up time of the pulse is a minimum. This object is attained by bending the blade in its resting position so that the blade vibrates initially with its maximum amplitude.

A still further object of the invention is to reduce or substantially prevent the production of transients or other irregularities of the current from the current generator. Such irregularities appear to be produced by vibrations resulting from the impact of the plunger on the lever. It has been found that these irregularities can be substantially prevented without appreciably reducing the sharpness of the impact on the lever by providing suitable damping means between the lever and the plunger.

Other features and objects of the invention will become apparent from the following detailed description thereof and the accompanying drawing the single figure of which illustrates a vibrating blade generator according to the invention.

Referring to the drawing, there are shown only the elements essential to an understanding of the invention. A vibrating blade A is fixed at its lower end to an anchoring piece of soft iron A and is free to vibrate at its upper end. The blade is formed of a resilient magnetic material.

States Patent P2 for limiting its axial movements.

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The vibrating portion of blade A is positioned in the gap M1 of a magnetic circuit M2 of a magnet M, which may be a permanent magnet. A current generating coil B is associated with the blade A so that the flux through coil B varies with the position of blade A in the gap M1. At rest, the blade A is held bent by the action of a spring R on a lever L.

The lever L has a fixed fulcrum O and is shaped so that it is necessary only to pivot the lever L against the pull of spring R to release the vibrating blade A. This action is produced by an electromagnet I having a plunger core P. The core P has a cap or flange P1 and an offset A compressible hammer U rests freely on the top of plunger P. When the electromagnet I is energized, the core P is drawn upward into the coil I1 and strikes the lever L near the end of its stroke. At the moment of impact the plunger P has all the kinetic energy it has stored up during its stroke, and in addition the attracting force of the electromagnet is then at a maximum value. The impact of the plunger on the lever L makes it pivot and thereby permits a quick and sharp release of blade A.

When the blade A is thus released it begins to vibrate at its natural frequency. As a result, the intensity of the magnetic field through coil B is varied periodically and an E. M. F. is induced in this coil having a frequency corresponding to the frequency of vibration of blade A. The induced E. M. F. and the generated current have an amplitude determined by the initial deflection of blade A. To vary the deflection of blade A it is only necessary to adjust the initial position of lever L. This is done by means of an abutment screw E threaded on the end of the casing C. Adjustment of screw E moves lever L against spring R to adjust the deflection of blade. A. A central opening E1 in screw E permits the passage of the member U therethrough. The coil I1 is held in place by an additional screw D which also is provided with a central opening for passage of the plunger.

While it is necessary to administer a sharp and sudden impact to lever L in order to obtain uniform pulses, such shocks tend to produce irregularities in the output current. This dilemma is resolved by the hammer or damping member U. This member may be formed of polycaprolactame or any suitable plastic or compressible member may be used which is capable of damping out the parasitic vibrations which give rise to the undesirable irregularities of the output current from coil B.

In teleprinter circuits of the type described in my application Serial No. 485,490 filed February 1, 1955, short current pulses having twelve different frequencies are transmitted to represent a five unit code. These current pulses can be supplied by a like number of generators of the type herein described, arranged so that the vibrating blades vibrate at the different desired frequencies of the currents. Each time a pulse of a particular frequency is required, a control current is impressed by one of the control circuits G1G12 on the coil of the electromagnet for that frequency. This causes the plunger P of that electromagnet, the lever L, and the blade A to operate, and thereby produce a current in coil B of the required frequency.

end in said magnetic circuit and having its other end free to vibrate near a pole of said magnetic circuit and being able to conduct flux, means including a pivoted lever for adjustably and releasably holding said blade in a predetermined bent position which is determinative of the maximum amplitude of the vibrations of said blade when released, means. constantly biasing the lever toward av position for bending the blade, an electromagnet having a movable plunger core which is imparted movement when the electromagnet is energized for delivering an impact to the lever at the end of its movement and for moving said lever away from said blade in a general direction toward which the blade tends to move initially when released from its bent position, and means including a coil surrounding said blade for producing a current corresponding to the vibrations of said blade.

2. A current generator according to claim 1, including resilient means for preventing said impact from producing spurious frequencies in said current.

3. In a teleprinter system for selectively sending short successive pulses of alternating current of different frequencies, in combination, a plurality of current generators, each generator comprising a magnetic circuit, for each generator a blade of resilient magnetic material fixedly connected at one end and having its other end free to vibrate near poles of an associated magnetic circuit, a coil in each generator magnetically coupled to said vibrating blade, means including a single pivoted lever for each generator for adjustably and releasably holding the blades individually in given bent positions which are determinative of the maximum amplitude of the vibrations of each blade when released, for each generator an electromagnet having a movable resilient core slug, means responsive to the energization of the electromagnet for causing said core slug to move between a rest position and a predetermined operative position and near the end of its movement toward its operative position to strike said lever so as to cause said lever to move away from said blade in a general direction toward which the blade tends to move initially when released from its bent position thereby to instantaneously release said blade for vibration, means constantly biasing the levers individually toward a position for engaging their associated blades and bending them and for cooperating with the holding means in restoring the blades individually to their same bent positions subsequent to the de-energization of the individual electromagnets, a teleprinter comprising control circuits for controlling the energization of said electromagnets of said generators individually and for periodically energizing and deenergizing them for short intervals of time, whereby the blades of said generators vibrate at different substantially constant frequencies and generate alternating currents in their associated coils corresponding to the different frequencies of vibration.

References Cited in the file of this patent UNITED STATES PATENTS i,234,650 Ferriter July 24, 1917 1,489,382 Brown Apr. 8, 1924 2,306,068 Lewis Dec. 22, 1942 2,307,521 Lovell Jan. 5, 1943 2,533,136 Muldoon Dec. 5, 1950 2,640,973 Cleaver June 2, 1953

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