Apparatus For Determining The Position Of Print By Using A Transducer

Abstract

With regard to the electronically driven typewriter which replaces the conventional mechanically driven typewriter, a movable type selection system detects the angular position of print on a paper and controls various attachments. In the movable type selection system of the electronic typewriter, it is required that the determination of the angular position of print is carried out under non contact and low inertia conditions and without receiving any effect of surrounding conditions. And further, it is required that the guidance from a present position to a commanded position is carried out over the shortest route by discriminating whether the present position is situated on the right side or left side of the commanded position. In the present application, this discrimination is achieved by using a transducer which is provided with a magnetic shield plate that rotates between one pair of induction coils and the electromagnetic induction of the secondary induction coil varies in accordance with the angular position of the magnetic shield plate.

Description

The present invention relates to an apparatus for determining the angular position of print by determining the angle of rotation of a revolving axis from a predetermined reference position.

With regard to the electronically driven typewriter which replaces the conventional mechanically driven typewriter, a movable type selection system detects the angular position of print on a paper and controls various attachments. In the movable type selection system of the electronic typewriter, it is required that the determination of the angular position of print be carried out under non-contact and low inertia conditions and without receiving any effect from surrounding conditions. And further, it is required that the guidance from a present position to a commanded position is carried out over the shortest route by discriminating whether the present position is situated on the right side or left side of the commanded position.

The object of the present invention relates to an apparatus for precisely determining the angular position of print under non-contact and low inertia conditions.

Another object of the present invention relates to an apparatus for determining the angular position of print accurately by detecting a voltage with reference to the commanded position as zero voltage.

A further object of the present invention relates to an apparatus for determining the angular position of print by using a transducer which is rotatable in both positive and reverse directions.

A still further object of the present invention relates to an apparatus for determining the angular position of print which is rotatable in steps of a unit angle or an integral number of unit angles.

A still further object of the present invention relates to an electonic typewriter which uses a transducer operated under non-contact and low inertia conditions.

Further features and advantages of the present invention will be apparent from the ensuing description and the accompanying drawings to which, however, the scope of the invention is in no way limited.

FIG. 1 is a block diagram of one embodiment of the present invention,

FIG. 2 shows the principle of one embodiment of the transducer used in the block diagram of FIG. 1,

FIG. 3 is a diagram showing the characteristics of the transducer of the present invention,

FIGS. 4A and 4B show one example of the transducer of the present invention, FIG. 5 shows a modified example of the transducer of FIG. 4B,

FIGS. 6A and 6B show another embodiment of the transducer of the present invention,

FIG. 7 shows the principle of the transducer of FIGS. 6A and 6B,

FIGS. 8A and 8B are diagrams showing the relation between D.C. drift and the position of the transducer,

FIG. 9 shows the gain characteristics of a transducer having a compression characteristic,

FIG. 10 shows an example of the form of the magnetic shield plate of the transducer having a compression characteristic,

FIG. 11 shows a blockdiagram of one embodiment using the transducer shown in FIG. 10,

FIGS. 12A and 12B show a side view of the another embodiment of the transducer and a plan view of the shield plate of the transducer,

FIGS. 13A and 13B are diagrams explaining the principle of the transducer shown in FIGS. 12A and 12B,

FIG. 14 shows a blockdiagram of one embodiment using the transducer shown in FIGS. 12A and 12B,

FIG. 15 is a diagram explaining the operation of the blockdiagram of FIG. 14,

FIGS. 16A and 16B show another embodiment of the transducer shown in FIG. 1,

FIG. 17 is the output waveform of the transducer shown in FIG. 16,

FIGS. 18A and 18B are diagrams explaining the control system of an electronic typewriter using a transducer according to the present invention,

FIG. 19 is a diagram explaining the relation between the hummer carrier and the type carrier in the typing process shown in FIGS. 18A and 18B,

FIG. 20 is a block diagram of the servo-control system for determining the position of print,

FIGS. 21A and 21B are the logic circuit of FIG. 20.

Referring to FIG. 1, transducer 1 is an essential feature of the present invention. The output of the transducer 1 is supplied via an amplifier 2 to a servo-motor 3. The mechanical angular position of the servo-motor 3 is fed back to the transducer 1 by a transmission mechanism 4. When the signal for selecting a balance point is supplied to the transducer 1 via input terminal 5, the transducer 1 generates an electric analog signal corresponding to the difference between the balance point selected by the above-mentioned signal and the position supplied by the transmission mechanism 4. This electric analog signal is supplied to the amplifier 2 which drives the servo-motor 3. Further, the movement of the servo-motor 3 is fed back via the transmission mechanism 4 to the transducer 1. As a result of this, the servo-system runs until the output of the transducer, becomes zero that is, until the difference between the above-mentioned balance point selected by the input signal and the position supplied by the transmission mechanism 4, becomes zero.

FIG. 2 shows the principle of the transducer of the present invention. As shown in FIG. 2, a magnetic shield plate 11 moves up and down between a group of primary windings 7a, 7b, 7c, . . . , 7x and a group of secondary windings 8a, 8b, 8c, . . . , 8x, and thus the degree of magnetic coupling between each pair of windings is varied. The magnetic coupling between the primary winding 9 and the secondary winding 10 is maintained constant. A selection signal e.sub.i is supplied to the induction coil 9 and one of the primary windings 7a - 7x, and the output e.sub.o is taken out from the series circuit of the secondary windings 8a - 8x and 10. When the magnetic shield plate 11 moves up and down, the degree of the magnetic coupling between the primary winding and the secondary winding is varied and the output voltage e.sub.o varies linearly in accordance with the above-mentioned movement of the magnetic shield plate 11. The magnetic coupling between the primary winding and the secondary winding being maintained constant, the output voltage e.sub.o varies as shown in FIG. 3 where the level shift voltage corresponds to e.sub.s. As shown in FIG. 3, the output voltage e.sub.o is proportional to the movement of the magnetic shield plate 11. The point T shows the position where the voltages e.sub.2 and e.sub.s coincide, that is, where the output e.sub.o becomes zero.

FIG. 4A shows a plan view of the transducer of the present invention and FIG. 4B shows the sectional view along A-A' in FIG. 4A. In FIGS. 4A and 4B, the same components as in FIG. 2 are shown by the same reference numbers as in FIG. 2. The magnetic shield plate 11 shown in FIG. 4A has the form of an eccentric Archimedes spiral. Thus, when the magnetic shield plate rotates about the center axis, the degree of the magnetic coupling between the primary winding and the secondary winding has the proportional relation shown in FIG. 3. Referring to FIG. 3, the position can be considered as an angular position of the magnetic shield plate, and the output e.sub.o is proportional to this angular position. The induction coils 9 and 10 which are not shown in FIG. 3, are arranged in a suitable position which is not effected by the magnetic field from the primary winding 7a - 7x and the secondary winding 8a - 8x. In the embodiment shown in FIGS. 4A and 4B, the plate type ferrite cores wound with wire are used as the induction coils.

In the transducer shown in FIGS. 4A and 4B, when the selection signal is applied to the primary winding, for example winding 7g, an output which corresponds to the degree of electro-magnetic coupling in accordance with the position of the magnetic shield plate 11 is obtained in the secondary coil 8g. With respect to the coils 7m and 8m, the periphery of the magnetic shield plate is situated midway between said coils, and the output e.sub.o becomes zero as already described in regard to FIG. 2. In front of and behind the coils 7p and 8p, the direction and quantity of the deviation can be detected as a positive or negative output voltage e.sub.o.

FIG. 5 is an example of one embodiment of the transducer shown in FIGS. 4A and 4B. Referring to FIG. 5, in addition to the construction shown in FIG. 4B, adjusting plates 13s, 13g and adjusting screws 14s, 14g are provided. When many primary and secondary coils are used in the transducer, it is very difficult to make output curves of these coils intersect in the point T shown in FIG. 3. For achieving this object, in the embodiment shown in FIG. 5, the adjusting plates 13s, 13g composed of non-magnetic substance or ferromagnetic substance are arranged near the coils 8s, 8g, and these positions of the adjusting plates are finely adjusted by the adjusting screws 14s, 14g so as to make the output curves of these coils 8s and 8g intersect as above.

As mentioned above, in the transducer shown in FIGS. 4A and 4B, the output level e.sub.o is shifted so that said level e.sub.o becomes zero for x = 0 using the primary and secondary coils 9 and 10. However, in the above-mentioned method, the output voltage e.sub.2 of the coil in the commanded position where .theta..sub.o = 0 is not zero, and the output voltage e.sub.o fluctuates due to variation of the voltage applied to the coil 9 for obtaining the shift voltage in the coil 10 and this phenomenon becomes a source of an error. For eliminating the error due to this phenomenon, means for compensating for the temperature or shielding the magnetic portion completely are conventionally required. This is very difficult and involves high cost.

FIG. 6A shows an improved transducer overcoming the above-mentioned drawback, and FIG. 6B is a sectional view along 0.degree. - 180.degree. in FIG. 6A. A magnetic shield plate 16 composed of conductive substance such as aluminium is fixed to a revolving axis 15. Referring to FIGS. 6A and 6B, a positive voltage detecting coil 17 and a negative voltage detecting coil 18 are wound on ferrite cores 17a and 18a. The primary coil 19 is wound on ferrite core 19a and faces opposite the voltage detecting coils 17 and 18 via the magnetic shield plate 16 as shown in the Figures. The primary coils 19a, 19b, . . . , 19x and the secondary coils 17a, 17b, . . . , 17x and 18a, 18b, . . . , 18x are connected electrically as shown in FIG. 7. In the position shown in FIG. 6A, the output voltage e .sub.o from the coils 17 and 18 is zero, because said coils 17 and 18 are shielded from the primary coil 19. As the coils 17 and 18 are connected differentially to each other as shown in FIG. 7, leakage fluxes interlinking the coils 17 and 18 are cancelled and the output voltage e.sub.o becomes zero without being effected by the surrounding conditions. As a result of this, the desired position can be obtained precisely.

When the axis 15 revolves in the positive direction as shown in FIG. 6A by the arrow A, the coupling between the secondary coil 17 and the primary coil 19 increases from zero, and becomes maximum at .theta. = 180.degree., and the coupling between the secondary coil 18 and the primary coil 19 is maintained at zero until .theta. = 180.degree.. When the rotation of the axis passes .theta. = 180.degree., the coupling between the secondary coil 17 and the primary coil 19 is maintained at zero until .theta. = 0.degree., and the coupling between the secondary coil 18 the primary coil 19 decreases from maximum and becomes zero at .theta. = 0.degree.. It will be understood that when the axis 15 rotates in the negative direction as shown in FIG. 6A by the arrow A, the above-mentioned phenomenon is reversed. Accordingly, the angle of rotation which represents the shortest route from the present position to the commanded position can be detected by discriminating the direction in which the output voltage decreases. Referring to FIG. 6A, it is understood that a broken line shows a complete circle and a hatched position shows the magnetic shield plate.

The above-mentioned transducer has the linear characteristics shown in FIG. 8A. When a D.C. drift (P.sub.+ - P.sub.-) is produced in the output voltage e.sub.o near the balance point P.sub.o, a drift of the position (.DELTA.X.sub.+.about..DELTA.X.sub.-) is produced, and this drift affects the accuracy of the position established by the servo-system. As a characteristic of the transducer for decreasing this drift of the position, the saturated characteristic shown in FIG. 8B may be considered. In FIG. 8B, the drift of the position (.DELTA.X'.sub.+.about..DELTA.X'.sub.-) can be considerably less than in FIG. 8A. FIG. 9 shows one example of the characteristic curve of the transducer characterized in FIG. 8B and FIG. 10 shows one example of the form of the magnetic shielding plate. Referring to FIG. 10, the full curve 20 and the dotted curve 21 show the forms of the transducer designed to decrease the D.C. drift, and the chained line shows the original form. However, when the transducer has the characteristic shown in FIG. 8B, the transient response characteristic deteriorates and overshoot is produced, so that, it is necessary for the rotation of the magnetic shield plate to be suddenly stopped.

For solving this problem, the apparatus for determining the position of the print utilizes the circuit shown in the block diagram of FIG. 11. Referring to FIG. 11, a combination of a non-linear type transducer 22 having a compression characteristic and an expander circuit replaces the linear type transducer 1 in FIG. 1. When a difference signal X between the input selection signal I and the signal from the mechanical position F, fed back from the transmission mechanism 4 is applied to the non-linear type transducer 22, the output of the transducer E.sub.1 and the output of the expander circuit E.sub.2 are:

E.sub.1 = k.sub.1 F(X) (1)

e.sub.2 = k.sub.2 G(E.sub.1) (2)

if we assume that the transducer 22 has a square-root characteristic corresponding to FIG. 8B, and the expander circuit has square characteristics, equations 1 and 2 become:

E.sub.1 = K.sub.1 .sqroot.X (3)

e.sub.2 = k.sub.2 E.sub.1.sup.2 = k.sub.2 k.sub.1.sup.2 X = KX (4)

as shown in Equation (4), the output of the expander circuit 23 becomes proportional to the input of the non-linear type transducer 22 as an overall characteristic.

FIGS. 12A and 12B are an example of another embodiment of the transducer of the present invention. Referring to FIG. 12A, a magnetic shield plate 24 which rotates between the primary winding 20 and the secondary winding 21 has the form shown in FIG. 12B. The magnetic shield plate 24 is composed of plural wings which have the same shape of an Archimedes curve as shown in FIG. 12B and arranged with constant pitch. When, the magnetic shield plate 24 rotates between the primary windings and the secondary windings as mentioned in FIG. 2, the output voltage of the secondary winding 26 varies with the angular position of the magnetic shield plate 24 as shown in FIG. 13. As shown in FIG. 13, the output voltage of the secondary winding is of a saw-tooth waveform, and one cycle of the saw-tooth waveform corresponds to one wing of the magnetic shield plate 24.

FIG. 14 shows a diagram using the transducer shown in FIGS. 12A and 12B. Referring to FIG. 14, the transducer 27 shown in FIGS. 12A and 12B is connected to the input terminal 5 and to the output of the transmission mechanism 4 and the output of the transducer 24 is connected via a changing circuit 28 to the servo-motor 28. A driving voltage generator 29 is connected to the changing circuit 28. The outputs of the transducer 27 and the driving voltage generator 29 are connected to a comparator 30 whose output is connected via a controlling circuit 31 to the other input terminal of the changing circuit 28. The controlling circuit 31 has two terminals to which a unit drive signal S.sub.1 or plural unit drive signal S.sub.2 can be applied.

In the circuit shown in FIG. 14, the displacement of the magnetic shield plate from one stable point to the next stable point as shown in FIG. 13 is carried out by the driving voltage generator 29 whose output is supplied via the changing circuit 28 to the servo-motor 3. The outputs of the driving voltage generator 29 and the transducer 27 are constantly compared in the comparator 30. When the output of the driving voltage generator 29 becomes smaller than the peak value of the output of the transducer 27, the output of the comparator 30 effects the changing circuit 28 via the controlling circuit so as to separate the changing circuit 28 from the driving voltage generator 29 and connect it to the transducer 27. As a result of this, the servo-motor is driven by the transducer 27 included in the servo-system, and reaches the next stable point. As mentioned above, the input supplied to the servo-motor is composed of two portions; that is, the non-servo portion in which a voltage having no relation to the difference between the present value and the target value is supplied to the servo-motor, and the servo-portion in which the voltage corresponding to the difference between the present value and the target value is supplied to the servo-motor.

FIGS. 15a - d show waveforms explaining the function of the circuit shown in FIG. 14. FIG. 15a shows a case of unidirectional control of the transducer 27. FIGS. 15b and 15c show the case of bidirection control of the transducer 27. When the plural unit drive signal is supplied to the terminal S.sub.2 of the controlling circuit 31, the initial displacement of the angle is multiplied by an appropriate number of times according to the plurality of the drive signal. FIG. 15d shows the case of a three times multiplying drive signal.

FIGS. 16A and 16B are an example of a still further embodiment of the transducer of the present invention. Referring to FIGS. 16A and 16B, the group of primary winding coils is composed of coils 33a - 33x and the group of secondary winding coils is composed of coils 34a - 34x which are respectively arranged face to face with coils 33a - 33x sandwiching the magnetic shield plate 32. As shown in FIG. 16, the magnetic shield plate 32 has a triangular form and the coils 33a - 33x and 34a - 34x are arranged in a linear direction so that this transducer has multiple balance points 1 - n in the linear direction as shown in FIG. 17. It will be understood that the primary coils 33a - 33x and the secondary coils 34a - 34x are connected similarly as in FIG. 2.

The apparatus for determining the position of print according to the present invention can be applied to a typewriter using a horizontal multi-type wheel system. The principle of the typewriter using the principle according to the present invention is shown in FIGS. 18A and 18B and FIG. 19. As shown in FIG. 18A, a group of multi-type ring 35 and a hummer 36 are displaced selectively by a carrier 37 and a carrier 38 which can be moved separately from the carrier 37. FIG. 18B shows the relation between the pitch interval of the type wheel (kP.sub.W) and the typing pitch interval (kP.sub.S). FIG. 19 shows the relation between the group of multi-type wheels 35 and the hummer 36 in the typing process. Referring to FIG. 19, I - VIII show positions of each type ring 35-1, 35-2, . . . , 35-8 of the group of the multi-type wheels 35. For the type wheels 35-1, 35-2, . . . , 35-8, the hummer 36 steps one typing pitch in the right hand direction every typing operation. When characters belonging to the same type wheel are printed, the group of multi-type wheels 35 and the hummer 36 step the same pitch. However, generally, the characters which are selected do not always belong to the same type ring, in which case the displacements of the group of the multi-type wheels 35 and the hummer 36 are carried out independently. This feature is shown in FIG. 19.

The amount of the displacement of the group of the type wheels 35 is shown generally by the following equation.

X.sub.ia - X.sub.(i .sub.-1)a = kP.sub.S + kP.sub.W [n(- 1) - n(i)] (5)

wherein:

X.sub.ia : X coordinate of the type ring in "i" typing position,

kP.sub.S : pitch of the type positions,

kP.sub.W : pitch of the type wheels,

n(i): number of type wheel used in "i" typing position.

For determining the X coordinate X.sub.ia taking into consideration the pitch of the typing positions kP.sub.S, the ratio between the pitch kP.sub.S and the pitch of the type wheels kP.sub.W is previously selected as a simple ratio. And an arithmetic circuit 39 shown in FIG. 20 determines the next typing position of the carrier 37 by using the input information concerning the number of the next type wheel and the command of the displacement of the typing pitch interval. The next typing position determined by the arithmetic circuit 39 is supplied to the transducer already mentioned, and shown, for example in FIGS. 4A and 4B. In the transducer 40 shown in FIG. 20, it will be understood that the horizontal displacement of the group of the type wheels 35 given by the servo-motor 3 is supplied to the magnetic shield plate as an angular displacement. In the example of the transducer 40 shown in FIG. 20, the output of the arithmetic circuit 39 and the output of the servo-motor 3 are always compared and the rotation of the servo-motor 3 continues until these two outputs reach balanced condition.

The number of balance points in the transducer 40 is shown by the following equation.

D = m(P.sub.W P.sub.S) .gtoreq. NP.sub.W (6)

wherein:

D: the number of the balance point distributed in the rotational direction of the transducer,

m: minimum value satisfying the relation m(P.sub.W.sup.. P.sub.S) .gtoreq. NP.sub.W (positive integer),

N: number of the type wheel (positive integer),

P.sub.W : ratio of the pitch of the type wheel (positive integer),

P.sub.S : ratio of the pitch of the typing space (positive integer).

Table 1 shows the relation of the above-mentioned Equation 6. --------------------------------------------------------------------------- TABLE 1

TERM D P.sub.W P.sub.S N L (kP.sub.S) NOTE __________________________________________________________________________ 1 8 1 1 8 8 A side print is producible __________________________________________________________________________ D is small, however 2 16 2 1 8 16 L is a little large __________________________________________________________________________ D and L are 3 24 3 2 8 12 small and suitable __________________________________________________________________________ 4 36 4 3 8 102/3 D is too large 5 45 5 3 8 131/3 Do. 6 40 5 4 8 10 Do. 7 24 3 1 8 24 Do. __________________________________________________________________________

In Table 1, L shows the total length of the type ring represented by the typing pitch as a unit. If the value of L is smaller, the loading inertia of the servo system is smaller.

In Table 1, item 3, that is, the case where D = 24 is the most suitable. The arithmetic circuit 39 and the transducer 40 in FIGS. 20, 21A and 21B comply with this condition. Referring to the arithmetic circuit 39 in FIG. 21A, the numbers of the type wheel are shown in I, II, . . . , VIII, and 24 balanced position of the transducer 40 are given by 39-1, 39-2, . . . . , 39-24. These outputs of the arithmetic circuit 39-1, 39-2, . . . , 39-24 are supplied to the 24 primary windings of the transducer 40 via amplifiers 39-1a, 39-2a, . . . , 39-24a, respectively,

Arithmetic circuit 39 is composed as shown in FIG. 21A, each of the output signals 39-1, 39-2, . . . , 39-24 is obtained by means of AND gate circuits and OR gate circuits. FIG. 21B shows one example of production of one of the output signals 39-1. That is, the logic signal 1 is supplied to 1, 2, 3, . . . . , 12 in order every time the hammer 36 displaces to the new typing position. And the logic signal 1 is supplied to I, II, . . . , VIII corresponding to the selected type wheel. Every time, the hammer displaces one pitch, the logic signal 1 is supplied to 5 , and the character to be typed is included in the type wheel III, and the logic signal 1 is applied to III. As shown in FIG. 21A, the output of the AND gate circuits corresponding to III and 5 is 39-3, and this output signal 39-3 is supplied via an amplifier 39-3a to the corresponding primary coil of the transducer 40. Then the analog voltage which corresponds to the difference in the mechanical positions between the type wheel including one pitch prior character kP.sub.W.sub.[n(i .sub.- 1).sub.] and the type wheel including the character to be typed KP.sub.W.sub.[n(i).sub.], is supplied from the secondary coil of the transducer 40 to the servo-motor 3 via the servo-amplifier 2. As a result of this, the type wheel including the character to be typed can be displaced to the next typing position.

Claims

What is claimed is:

1. Apparatus for determining a printing position of a typewriter in accordance with a position selection signal indicating the position of the type to be selected comprising:

1. a transducer which includes:

a. primary coil means composed of a first plurality of first coils which are arranged adjacent each other and each of which has an input terminal for receiving said position selection signal;

b. secondary coil means composed of a second plurality of second coils corresponding to said first plurality which are connected in series facing said first coils with respective predetermined air gaps between said first and second coils, said secondary coil means having output terminal means;

c. a shield plate which is made of a conductive, non-magnetic material and disposed in said air gaps and movable with respect to said primary and secondary coil means thereby to variably and selectively shield said primary coils from said corresponding secondary coils by dissipating eddy currents produced within said plate;

2. a servo-motor which is connected to said output terminal of said secondary coil means and is driven in accordance with the output voltage of said secondary coil means; and

3. a transmission mechanism which is fixed to an output shaft of said servo motor and moves said shield plate in accordance with the rotation of said shaft so as to feedback information of mechanical position of said servo motor to said transducer and drive said servo motor until said output voltage reaches a predetermined voltage.

2. Apparatus for determining a printing position of a typewriter according to claim 1 wherein said shield plate is mounted for rotation about its center and there are a plurality of pairs of said first and second coils arranged circumferentially around said center, wherein said shield plate has the form of an Archimedes spiral, and the magnetic coupling between said first and second coils is varied in accordance with the rotation of said shield plate.

3. Apparatus for determining a printing position of a typewriter according to claim 1 wherein there are a plurality of pairs of said first and second coils arranged linearly, wherein said shield plate has a triangular form, and the magnetic coupling between said first and second coils varies in accordance with the linear displacement of said shield plate.

4. Apparatus for determining a printing position of a typewriter according to claim 2 wherein said transducer includes one each of said first and second coils which are arranged so as to have an electromagnetic coupling coefficient independent of the position of said shield plate, said one first coil being excited with the same polarity as the other coils of said primary coil means, said one second coil being connected with a polarity opposite to the other second coils of said secondary coil means so as to shift said output voltage of said secondary coil means and said servo motor is rotated in the normal or reverse direction depending upon polarity of said output voltage compared with said predetermined voltage.