US3163273A

US3163273A - Impulse control arrangement for electromagnetic clutches

Info

Publication number: US3163273A
Application number: US214394A
Authority: US
Inventors: Maier Guenther; Leonberg Kreis
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1961-08-03
Filing date: 1962-08-02
Publication date: 1964-12-29
Anticipated expiration: 1981-12-29
Also published as: DE1158377B; GB1008074A

Description

G. MAIER Dec. 29, 1964 IMPULSE CONTROL. ARRANGEMENT FOR ELECTROMAGNETIC CLUTCHES Filed Aug. 2, 1962 MM E..

United States Patent Oiitice figlbgig Patented Dee. 29, 1964 3,l6i,273 IMPULSE CN'HRGL ARRANGEWNT FUR ELECTRMAGNETEC CLUTCHES Guenther Maier, Gerlingen, Kreis Leenberg, Germany, assigner te Robert Bosch G.m.b.H., Stuttgart, Germany Filed Aug. 2, i962, Ser. No. 2in/5,394 Claims priority, application Germany, Aug. 3, 2196i, B 63,5% 8 Claims. (Ci. i92t4) The present invention concerns a control arrangement for electromagnetic clutches, and more particularly for those types of clutches which are used in connection with a vehicle motor for starting the vehicle to move and in connection with gear shift operations. Clutches of this type are equipped with electromagnet means comprising a winding which is energized by energizing pulses at a frequency increasing with the increase of the rotary speed of the motor and supplied by a monostable relaxation circuit which is triggered in synchronism with the motor speed by control pulses so as to change between its stable blocking condition and its unstable second condition which determines the duration of the energizing pulses.

It is required that clutches of this type are changed to torque transmitting condition by the respective control arrangement whenever the motor speed has been increased to about twice its idling speed. It is necessary that the torque transmitted by the clutch can increase from the smallest possible value available at the idling speed of the motor to a maximum value limited only by the structural dimensions of the clutch in which case the energizing pulses follow each other so rapidly that the magnetic iield in the clutch only insigniiicantly decreases during the intervals between two consecutive energizing pulses.

lf a monostable relaxation circuit is used for producing energizing pulses the duration whereof is substantially independent of the rotary speed of the engine, then the time determining element must be selected to be of rather large size in order to obtain a suiiiciently strong clutching effect for transmitting a suiiicient torque even when at the start of the movement of the vehicle the motor speed is only somewhat higher than the idling speed. However, during the operation of the traveling vehicle the operating speed of the motor must be increased considerably beyond the above mentioned speed used during the start of the movement of the vehicle. But under such conditions the danger exists that the intervals between the individual consecutive energizing pulses become so short that the storage means forming part of the above mentioned time determining element, eg. a capacitor, cannot be charged suiiiciently before the start of the next following energizing pulse, or it is even possible that control pulses are produced within the period of a corresponding energizing pulse. Under these circumstances a control pulse could not be responded to by the relaxation circuit, with the result that the energizing pulses ywould occur at a frequency which actually corresponds to only one half of the actually existing rotary speed of the engine. Such a drop of the frequency of the energizing pulses may occur as the actual operating speed of the motor increases and at least when the spacing between the control pulses has the same duration as the energizing pulses themselves.

It is therefore one of the objects of this invention to prevent the above mentioned drop in the frequency of the energizing pulses and the corresponding drop of the transmittable torque to one half of the desired value, by means of a purely electronic arrangement.

Other objects will become apparent from the following description of embodiments of the invention.

With above objects in mind the invention provides in an automotive vehicle having an engine and an elect-romagnetic clutch arrangement including electromagnetic ally activable clutch members, one thereof being connected with one, the other one being connected with another one of two rotatable members and adapted to transmit torque from one to the other member upon application of pulsating energy to said electromagnetic clutch arrangement, in combination, a source of electric energy; electric pulse generator means cooperating with the engine for furnishing electric control pulses at a frequency corresponding to the operational speed of the engine; pulse former means having input means for being supplied with said control pulses and furnishing in response to each control pulse a double pulse composed of a first and a second pulse portion having respectively opposite polarities and being spaced from each other by a predetermined interval; and electric oscillator means energized by said source and controllable by said double pulses furnished by said pulse former means, said oscillator means furnishing energizing pulses to the electromagnetic ciutch arrangement for energizing the latter, each of said energizing pulses being started upon application of one of said second pulse portions and having a predetermined normal duration as long as the sequence of said control pulses has a frequency below a selected frequency corresponding to the upper limit of a predetermined low range of engine speeds, each of said energizing pulses being however terminated with a reduced duration by the application of one of said first pulse portions when at engine speeds above said low range of engine speeds such first pulse portion occurs before the end of said normal duration of an energizing pulse, the interval between consecutive energizing pulses being in this case determined by said predetermined interval between said iirst and second portions of said double pulses.

Preferably the pulse former means or pulse former stage comprises a transistor whose base is connected via a rectifier with the junction point within a voltage divider connected in parallel with the emitter-collector circuit of the transistor and with a load resistor series-connected therein, the base of the transistor being additionally connected via a capacitor with the source of the above mentioned control pulses. ln this case the double pulse can be produced in a very simple manner by arranging a capacitor in the line connecting the input of the oscillator means with the junction point between the collector of the transistor and the above mentioned load resistor.

lf for the purpose of simplifying the structure of the oscillator the latter is provided with an input transistor and with an output transistor conductively coupled with the former, the emittercollector circuit of the output transistor being connected in series With the magnet winding of the clutch arrangement, then a capacitor may be chosen as time determining element which is arranged between that end of the magnet winding which is connected with the output transistor, and the base of the input transistor, a resistor being provided which is counected in series with the time determining capacitor but becomes effective only during the discharge of the capacitor but is shunted by means of a rectifier in order to make it possible that the time determining capacitor is charged rather rapidly. ln this case it is possible to obtain comparatively long energizing pulses while the interval between the above mentioned rst pulse portion and the following second pulse portion which initiates the next following energizing pulse can be kept very short.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specie embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic illustration of a four-cylinder four stroke internal combustion engine connected with an electromagnetic clutch and with an electronic control arrangement;

FIG. 2 is an axial section of an electromagnetic clutch as used in the arrangement accord-ing to FIG. 1;

FIG. 3 is a schematic circuit diagram of an electronic control arrangement for the electromagnetic clutch; and

FIG. 4 is a diagram illustrating the operation and function of this arrangement.

Referring now to FIG. 1, the internal combustion engine operating a vehicle not shown in the drawing cooperates with a three-phase generator 11 the output windings 12, 13 and 14 whereof are connected via three pairs of inter-connected semi-conductor rectiiiers 15, via a positive l-ine 16 and a negative line 17 with a storage battery 18 of 24 volts. The generator 11 is controlled by conventional regulator means not shown in the drawing in such a manner that the output voltage thereof is kept at -a constant amplitude at all those rotary speeds of the engine which may occur during the operation of the motor vehicle. An electromagnetic clutch having a housing 19 is mounted at one end of the engine 10 and is controlled by electric control means 20, illustrated in more detail in FIG. 3, in such a manner that the clutch is automatically changed to torque transmitting condition as soon as the rotary speed of the engine increases to a point which is above the minimum or idling speed of the engine. A conventional gear box 21 is mounted next to the housing 19 of the electromagnetic clutch, the variousgear combinations being controllable by a conventional gear shift lever 21a.

As shown at a larger scale in FIG. 2, the electromagnetic clutch comprises within its housing 19 two

concave plate members

22 and 23 which constitute together a holllow shell rigidly connected with the crank shaft 24 of the engine and constituting at the same time the ily wheel of the engine. Additionally the clutch comprises a rotor 26 mounted on the drive shaft 25 and provided with a plurality of grooves 27 arranged along the circumference of the rotor. In practical embodiments of this type of a clutch an annular gap of l to 2 mm. radial width is provided between the circumference of the rotor 26 and the inner circumferential face 2S of the above mentioned shell. The emp-ty space between the

shell members

22, 23 and the rotor 26 is partly filled with a magnetizable powder 30 which is driven by centrifugal force into the above mentioned annular gap as soon as the engine is in operation. In the two faces of the

members

22 and 23 abutting against each other annular grooves 31 are provided and accommodate a magnet winding 32. The ends of the magnet winding 32 are connected with

slip rings

33 and 34, respectively, which are mounted on the outer face of the member 23 and are insulated against each other. Two

brushes

35 and 36 insulated against each other cooperate with the slip rings, respectively, and are connected with a terminal block 37 mounted on the outside of the housing 19, the terminals of this terminal box, and thereby the magnet winding 32, are connected with the control arrangement 2t). This control arrangement furnishes the electric energy required for the transmission of torque in the form of approximately rectangular pulses one of which is diagrammatically indicated at 3S in FIG. 1. For producing these pulses the input of the control arrangement 20 is connected with the winding 12 of the generator 11 as shown in greater detail in FIG. 3, by means of a cable connection 39 by means of which a control pulse for triggering an energizing pulse is transmitted tothe control arrangement 20 with each revolution of the comprises a monostable relaxation oscillator equipped with three

transistors

41, 42 and 43, and a pulse former `stage which includes a transistor 44.

The transistor 44 has its emitter directly connected with the positive line 16 which is taken from the positive terminal of the storage battery 18. The base of the transistor 44 is connected via a resistor 45 of 10,000 ohms with an auxiliary line 47 that is connected via. a resistor 46 of 700 ohms with the negative line 17 taken from the negative terminal of the battery 18. The resistor 46 together with an electrolytic capacitor 48 of 50 pf. connected with the positive line 16 serves to protect the

transistors

41, 42 and 44 against excessive voltages which may develop when `the battery 1? is disconnected from the rectiiiers 15 or when other energy consumers of low resistance are disconnected from the battery.

The control transistor 44 is held in conductive condition via the base resistor as long as no control pulses 80 are applied thereto. The collector of the control transistor 44 is connected with a resistor 49 of 200 ohms which is, in turn, connected with the auxiliary line 47 via a load resistor 50 of 800 ohms. The junction point 52 between the resistors 49 and S0 is connected via a capacitor 53 of .2 ttf. with the base of the input transistor 41 of the oscillator. For initiating the individual energizing pulses control pulses 80 are used which are derived from a pulsating voitage Ug taken from the output winding 12 and developed by the operation of the generator 11. The voltage Ug has a trapezoidal wave form as illustrated by the diagram 54. This voltage is differentiated by means of a capacitor S5 of l pf. which is connectedwith the junction point of a voltage divider composed of a resistor 58 of 12,000 ohms and a resistor 59 of 10,000 ohms connected between the terminals of the battery 18, and the thus differentiated voltage is then applied via a rectiiier 60 to the base of the control transistor 44.

The oscillator arrangement comprises, in addition to the inputtransistor 41 which has its emitter directly connected with the positive line 16, an amplifying transistor 42 and an output transistor 43 the base of which is connected with the emitter of the transistor 42, and capacitor 62 of .6 af. which serves as a time determining element for determining the normal duration of the energizing pulses 33 as described further below. One electrode of the time determining capacitor 62 is connected with the collectors of the transistors 42 and 43, these collectors being interconnected with each other and with one end of the clutch winding 32. The other electrode of the capacitor 62 is connectedwith the positive line 16 via a resistor 66 of 5,000 ohms, shunted by a rectifier 67, a second rectifier 65, and two series-connected resistors 63 of 700 ohms and 64 of 500 ohms, the junction point therebetween being connected with the base of the input transistor 41. The junction point between the two rectiiiers 65 and 67 is connected via a resistor 69 of 15,000 ohms with the auxiliary line 47 which carries a potential almost equal to that of the negative terminal of the battery 1S.

As long as none of the below described

double pulses

83, 84 are produced a current tlows via the emitter-base circuit of the input transistor 41, ythe resistor 64, the rectifier 65 and the resistor 69 which current renders the input transistor 41 conductive so that it can carry a current across its collector resistor of 800 ohms whereby the base (connected with the collector of the input transistor 41) of the amplifying transistor 42 is caused to carry a high positive potential almost equal to the potential of the positive line 16. Consequently, the transistor 42 which has its emitter connected via a resistor 71 of 30 ohms with the positive line 16 cannot carry any current and holds the output transistor 43 also in non-conductive condition, the emitter of this transistor being connected with .the junction point within a second voltage divider cornposed of a rectifier 72 and Lof a resistor 73 of 1,000 ohms. Under these circumstances the clutch winding 32 is practically without any energization but makes it possible that the time determining capacitor 62 is charged across the rectiiier 67 of corresponding direction of conductivity to a potential which is only slightly below the voltage of the 5 battery 18. This is possible because the capacitor 62 is connected at one end via the clutch winding 32 with the negative line 17 and at the other end with the base of the input transistor 41 which has almost the full positive potential of the positive line 1d.

The above described condition may be called the starting condition in the operation of this arrangement and prevails at low rotary speeds of the engine always at the moment when the control voltage Ug furnished by the generator starts to rise from zero at the moment T1 marked in FIG. 4 and furnishes via the capacitor 5S and the rectifier 6) a blocking control pulse Sil. This pulse 80 suiiices for blocking the pulse forming transistor 44 for a period of time ending at the moment T2.

At the top of FIG. 4 the variations of the pulsating voltage 54 or Ug are plotted against time t. The diagram S2 in FIG. 4 illustrates the potential existing at the junction point 52, and shows that this potential drops during the above mentioned blocking period T1-T2 almost to the potential of the negative line 1'7 as indicated by the line t). During this blocking period a double pulse appears at the base of the input transistor 41, this double pulse being composed of a narrow, strongly negative rst pulse portion 33 and or" a second positive pulse portion 84. The spacing between these two pulse portions is exactly predetermined as will be shown further below.

Of the above mentioned two pulse portions S3 and 84 the first one occurs at the moment T1 and remains ineffective as long as the rotary speed of the engine is within a predetermined low speed range because under this condition the input transistor 41 is in conductive condition at this moment T1. However, since the second pulse portion Sd occurring at the subsequent moment T2 is positive it is capable of raising the base potential of the input transistor 41 above the potential of the positive line 16 in positive direction whereby the transistor 41 is rendered non-conductive. Consequently, at this moment the amplifying transistor 42 and the output transistor 43 are both rendered conductive and the desired energizing pulse 3S is applied to the clutch winding 32. The energizing currentiiowing through the clutch winding 32 and starting at the moment T2 has the effect that the collector potential of the transistors 4t2 and 43 abruptly rises to a value which -is only slightly below the output voltage of the battery 18. The just mentioned collector potential is added to the potential of the capacitor 62 which has been charged during the preceding interval between energizing pulses so that now the resulting base potential of the input transistor 41 holds this transistor in non-conductive condition beyond fthe complete decay of the second pulse portion Sd. Only when the capacitor 62 has almost entirely discharged via the resistors 66 and 69, the input transistor 41 can be rendered again conductive at the moment T3 whereby the transistors 42 and 43 are rendered non-conductive and thus terminate the prevailing energizing pulse. The duration of the energizing pulse 38 is therefore determined by the time between the moment T2 and the moment T3 as long as the rotary speed of the engine is so low that a blocking second pulse portion 84 occurs only after the termination of an energizing pulse.

In the operation of an automotive vehicle it is necessary that even when the transmission is in gear the vehicle is not set into motion while the motor is idling and the brakes are not applied. But, on the other hand, upon increase of the engine speed to about twice the idling speed the torque furnished by the engine must be fully transmitted to the drive wheels of the vehicle. These conditions are satisfactorily met by the arrangement according to the invention because the discharge time constant of the time determining element is predetermined by the capacity of the capacitor 62 and by the resistance of the discharge resistors do and 69 in such a manner that the normal duration of the energizing pulses amounts to l0 msec. Under these circumstances the intervals between consecutive energizing pulses at idling speed of the engine are long enough for permitting the pulse-produced energizatiion of the clutch magnet .to decay completely so that the mean value over time of the clutch energization and consequently the transmittable torque remain very small. As the engine is accelerated the intervals between the consecutive energizing pulses decrease more and more whereby the mean value of energization and consquently the transmittable torque increase rapidly and can then be varied very easily in any desired manner by the operation of the gas pedal.

When the engine speed is higher than within the above mentioned low speed range, then the individual control pulses Si) and the corresponding double pulses occur at such a frequency that the second pulse portions 84 which initiate the energizing pulses 38 may occur during the duration of an energizing pulse 3S which has been initiated by the preceding second pulse portion 84. Since the input transistor 41 is held in non-conductive condition during the normal duration of an energizing pulse the blocking second pulse portion S4 would remain ineilective and only the next following pulse portion h4 could cause the input transistor 41 which has meanwhile become conductive to initiate the next following energizing pulse. Consequently, without the provision of the double pulse according to the invention, the energizing pulses would occur at a frequency which corresponds only to one half of the actually prevailing engine speed. Consequently the clutch would slip and would not be able to transmit the considerably high torque furnished by the engine at these higher speeds.`

This serious diiiiculty is reliably overcome by the invention which provides the above described pulse former stage whereby a negative first pulse portion 83 at the moment T1 is produced before the respective positive second pulse portion S4 occurs, the moment T1 coinciding with the rise of the generator voltage Ug from zero as shown in FIG. 4. The negative first pulse portion 33 has the effect that the input transistor 41 is rendered conductive prematurely in spite of the charge of the capacitor 62. still existing at the high engine speed. As the input transistor 41 is rendered conductive under these conditions the prevailing energizing pulse 38 which otherwise would have a duration ending at the moment T3 is ately following second pulse portion 84 which is intended to initiate the next following energizing pulse 38 is now able to render the input transistor 41 again non-conductive. The comparatively short interval between the negative first pulse portion 83 and the positive second portion 84 initiating the following energizing pulse 3S is suiicient for charging again the capacitor 62 because the charging current for this capacitor encounters practically no resistance in the rectiiier 67 and because also the elements arranged in the charging circuit (emitter-base circuit of the input transistor 41, resistor 64 and rectifier 65) have a low resistance as compared with the high resistance discharge resistors 66 and 69.

Reference is now made specifically to the explanatory diagrams of FlG. 4. As mentioned above the uppermost diagram illustrates the Variations with time of the generator voltage Ug serving as control voltage, the next diagram S2 illustrates the potential variations at the junction point 52 of the pulse former stage, and the next diagram below shows the occurrences of the corresponding double pulses composed of a negative first pulse portion 83 and of a second positive pulse portion 84, these diagrams being based on an engine speed of about 1,000 r.p.m. Below the just discussed diagrams another group of similar diagrams plotted at the same time scale are shown, namely a diagram for the generator voltage Ug based on an engine speed ot about 2,500 rpm., a diagram illustrating the corresponding occurrences of the

double pulses

83, 84 and inally a diagram illustrating the formation of the sansa/s energizing pulses 3S under these conditions. Frein the lowermost diagram it can be seen clearly that each energizing pulse is prematurely terminated at the moment T4 because already at this moment the next following negative first pulse portion S3 is generated whereby the input transistor 4l is again rendered conductive so as to block simultaneously the transistors 42 and 43 whereby the respective energizing pulse 38 is terminated. lf the engine speed is further increased the intervals between the end of one energizing pulse 38 at the moment T4 and the start of the next following energizing pulse 33 at the moment T2 remain constant. Since they are comparatively short in relation to the normal duration or the adjusted duration of the energizing pulses, the energize.- tion of the electromagnetic clutch will drop only insignicantly during these intervals on account of the high inductivity of the electromagnetic arrangement. For the purpose of illustration in FIG. 4 the intervals just discusscd are illustrated as being `rather large only for the salte of the clarity of the illustration. However, it is absolutely possible to choose the resistor 64 located in the charging circuit of the time determining capacitor 62 sufciently small so that the spacing between the moments T4 and T2 can be still more shortened by correspondingly changing the parameters of the voltage divider resistors S8 and 59.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in yother types of impulse control arrangement for electromagentic clutches differing from A the types described above.

While the invention has been illustrated and described as embodied in impulse control arrangement for electromagnetic clutches dilfering from the types described above including double pulse former means, itis not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any Way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of lequivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an electromagnetic clutch arrangement, in combination, a source of electric energy; electric pulse generator means for furnishing electric control pulses at a variable frequency; pulse former means having input means for being supplied with said control pulses and furnishing in response to each control pulse a double pulse composed of a first and a second pulse portion having respectively opposite polarities and being spaced from each other by a predetermined interval; and electric oscillator means energized by said source and controllable by said double pulses furnished by said pulse former means, said oscillator means furnishing energizing pulses to the electromagnetic clutch arrangement for energizing the lauter, each of said energizing pulses being started upon application of one of said second pulse portions and having a predetermined normal duration as long as the sequence of said control pulses has a frequency below a selected frequency corresponding to the upper limit of a predetermined low range of frequencies, each of said energizing pulses being however terminated with a reduced duration by the application of one of said first pulse portions whenY at frequencies above said low range of frequencies such first pulse portion occurs beforeA the end of said normal duration of an energizing pulse, the interval between consecutive energizing pulses being in this case determined by said predetermined interval between said iirst and second portions of said double pulses.

2. In an electromagnetic clutch arrangement, in combination, a source of electric energy; electric pulse generator means for furnishing electric control pulses at a variable frequency; pulse former means having input means for being supplied with said control pulses and furnishing in response to each control pulse a double pulse composed of a first and a second pulse portion having respectively opposite polarities and being spaced from each other by a predetermined interval; and monostable relaxation oscillator means energized by said source and controllable by said double pulses furnished by said puise former means, said oscillator means furnishing energizing pulses to the electromagnetic clutch arrangement for energizing the latter, each of said energizing pulses being started upon application of one of said second pulse portions and having a predetermined normal duration as long as the sequence of said control pulses has a frequency below a selected frequency corresponding to the upper limit of a predetermined low range of frequencies, each of said energizing pulses being however terminated with a reduced duration by the application of one of said first pulse portions when at frequencies above said low range of frequencies such first pulse portion occurs before the end of said normal duration of an energizing pulse, the interval between consecutive energizing pulses being in this case determined by said predetermined interval between said rst and second portions of said double pulses.

3. An arrangement as claimed in claim 2, wherein said pulse former means comprise control transistor means (44) having an emitter-collector circuit including a load transistor (50) connected between the terminals of said source (18), voltage divider means connected in parallel with said emitter-collector circuit and including a first and a second resistor (58, S9), rectifier means (66) being connected between the junction point (56) of said resistors (5S, 59) and the base of said control transistor means (44), and capacitor means (55) being connected between said junction point (56) and said pulse generator means.

4. An arrangement as claimed in claim 3, wherein an intermediate resistor (45) .is connected between the base of said control transistor means (d4) and that end of said load transistor (50) which is connected to a terminal of 4said source (ld), and wherein said rectifier means (60) has a direction of conductivity toward said intermediate resistor (45) and said base of said control transistor means (44).

5. An arrangement as claimed in claim 4, wherein said monostable relaxation oscillator means comprises an input transistor (4l) and a second capacitor (53) connected between the base of said input transistor (41) and that end of said load resistor (Stb) which is connected with the collector of said control transistor means (44).

6. An arrangement as claimed in claim 5, wherein said monostable relaxation oscillator means further comprises an amplifying transistor (4Z) connected at its base with the collector of said input transistor (41) and an output transistor (43) connected at its base with the emitter of said amplifying transistor (42), the collectors of said amplifying transistor (42) and of said output transistor (43) being connected with the electromagnetic clutch arrangement (32), a circuit portion being provided between the collector of said output transistor (43) and the base of said input transistor (41) and containing a time determining capacitor (62) controlling the normal duration of said energizing pulses and a series-resistor (66).

7. An arrangement as claimed in claim 6, wherein a rectifier (67) having a direction of conductivity toward said time determining capacitor (62) is connected in parallel with said series-'resistor (66).

'8. An arrangement as claimed in claim 7, wherein a discharge resistor (69) is connected between said series- 9 resistor (66) and one terminal of said source (1S), and a rectifier (65) is connected between the base of said input transistor (41) and the junction point between said series-resistor (66) and said discharge resistor (69).

References Cited by the Examiner UNITED STATES PATENTS 2,692,510 10/54 Gille 74-125.5 X 2,714,435 8/55 DOzouville 192-35 2,747,710 5/56 Smith 192-84 2,832,235 4/58 Derman 74-125.5 X 2,857,769 10/58 Bale 74125.5 X

Park.

Lemon 318--138 Budlong 74-125.5 X Taylor 318-341 X Vergez S18-341 Denning 318--138 Hansen 318-341 Issler 192-21.5 X Ryan 74--125.5 X Baumann 192--3.5

BROUGHTON G. DURHAM` Primary Examiner.

Claims

1. IN AN ELECTROMAGNETIC CLUTCH ARRANGEMENT, IN COMBINATION, A SOURCE OF ELECTRIC ENERGY; ELECTRIC PULSE GENERATOR MEANS FOR FURNISHING ELECTRIC CONTROL PULSES AT A VARIABLE FREQUENCY; PULSE FORMER MEANS HAVING INPUT MEANS FOR BEING SUPPLIED WITH SAID CONTROL PULSES AND FURNISHING IN RESPONSE TO EACH CONTROL PULSE A DOUBLE PULSE COMPOSED OF A FIRST AND A SECOND PULSE PORTION HAVING RESPECTIVELY OPPOSITE POLARITIES AND BEING SPACED FROM EACH OTHER BY A PREDETERMINED INTERVAL; AND ELECTRIC OSCILLATOR MEANS ENERGIZED BY SAID SOURCE AND CONTROLLABLE BY SAID DOUBLE PULSES FURNISHED BY SAID PULSE FORMER MEANS, SAID OSCILLATOR MEANS FURNISHING ENERGIZING PULSES TO THE ELECTROMAGNETIC CLUTCH ARRANGEMENT FOR ENERGIZING THE LATTER, EACH OF SAID ENERGIZING PULSES BEING STARTED UPON APPLICATION OF ONE OF SAID SECOND PULSE PORTIONS AND HAVING A PREDETERMINED NORMAL DURATION AS LONG AS THE SEQUENCE OF SAID CONTROL PULSES HAS A FREQUENCY BELOW A SELECTED FREQUENCY CORRESPONDING TO THE UPPER LIMIT OF A PREDETERMINED LOW RANGE OF FREQUENCIES, EACH OF SAID ENERGIZING PULSES BEING HOWEVER TERMINATED WITH A REDUCED DURATION BY THE APPLICATION OF ONE OF SAID FIRST PULSE PORTIONS WHEN AT FREQUENCIES ABOVE SAID LOW RANGE OF FREQUENCIES SUCH FIRST PULSE PORTION OCCURS BEFORE THE END OF SAID NORMAL DURATION OF AN ENERGIZING PULSE, THE INTERVAL BETWEEN CONSECUTIVE ENERGIZING PULSES BEING IN THIS CASE DETERMINED BY SAID PREDETERMINED INTERVAL BETWEEN SAID FIRST AND SECOND PORTIONS OF SAID DOUBLE PULSES.