ELECTRIC CONTROL OF VENETIAN BLIND

Abstract: For the purpose of giving the user of an electric control of a Venetian blind (5) in a window (1) the possibility of adjusting the angular position of the slats independently of a raising or lowering of the Venetian blind by means of an electric motor (14) and spring clutches (11, 12) and corresponding lift cords (10), said control comprises a control circuit (19) with three position switch (21) controlled by the user, said control circuit being so arranged as to drive said motor (14) at low speed during a first predetermined time interval for adjusting slats angle and thereafter to drive said motor (14) at increased speed for the raising or lowering of said Venetian blind.

Description: Electric control of Venetian blind. This invention relates to an electric control of Venetian blind, and of the kind comprising a Venetian blind with head rail, lower list, slats, a drive mecha¬ nism with a number of spring clutches for driving a corresponding number of ladder tapes and lift cords and a reversible electric motor for driving a drive shaft of said spring clutches. A spring clutch of the above-mentioned kind is known from German Patent Specification No. 1,638,007 and is ordinarily used on Venetian blinds that are operated manually by means of a pulling cord. Said spring clutch comprises a drum around which the lift cord of Venetian blind is wound and which serves to raise or lower said lower,list, and a drum around which a specially designed helical spring is wound, the ends of said spring being in engagement with lugs on ladder tape, said spring be¬ ing arranged in such a way that by operating the pulling cord it is possible to adjust the slats in almost verti¬ cal position. By continued pulling action on pulling cord, the lower list may then be raised or lowered. Since there is a direct mechanical link between the two drums of the spring clutch, the two movements, i.e. adjustment of angle and raising (or lowering), begin simultaneously. By proper dimensioning of the diameters of the drums, it is however possible to obtain that the angle adjustment happens quicker than the raising or lowering movement itself. From e.g. Danish Patent Specification No. 144 894 it is known per se to provide a Venetian blind with an electric motor for manoeuvring said Venetian blind. By only associating an electric motor with said spring clutches in a control device as defined above in preamble, one would of course obtain an electrical manoeuvring of said Venetian blind, but the two opera¬ ting steps, i.e. adjustment of slats angle and raising or lowering are still concomitant, which makes it dif- ficult for the user to effect angular adjustment inde¬ pendently of the raising or lowering. From US Patent Specification No. 3,310,099 an electric control of Venetian blind is known, which com¬ prises essentially an electric unit for manual operation and a mechanism, the particular purpose of which is to ensure parallel guiding of lower list during its move¬ ment up and down and to avoid the lift cords being paid out disorderly, when the pulling action due to lower list weight ceases if some part, such as furniture, interfers with the free movement of lower list, said mechanism being furthermore so arranged that when the lower list is in its lowermost position, the user is able to perform adjustment of slats angle without con¬ comitant raising of lower list. Thus, said prior art device does not give the user the possibility of arbitrary slats adjustment by means of said control unit, when the lower list is in some position between uppermost position and lowermost position. This invention intends to obviate such drawbacks and in this respect a control device of the kind set forth in preamble differs from prior art in that accor¬ ding to the invention it comprises a control circuit so arranged as to supply current to motor in a predeter- mined time interval for driving said motor at a first speed in a direction choosen by user for slow change of angle of slats by means of spring clutches and thereafter, when said slats at the elapsing of said time interval has reached one of their extreme positions, to supply motor with a second stronger current for driving said motor at a second higher speed in order to obtain in the direction choosen by user raising or lowering of lower list of Venetian blind by means of said spring clutches and corresponding lift cords. By separating the two functions, i.e. slats adjustment and raising (or lowering) from one another by means of said control circuit, the user is thus given the possibility within said predetermined interval of adjusting the slats angle without or practically without raising or lowering movement. Experiments made on a window of ordinary size and with a Venetian blind of usual type show that a time interval of a few seconds, e.g. 4 s, is quite sufficient for adjustment of slats one way or the other. If within said predetermined time interval and after having ob¬ tained the desired angle position one stops activation of control circuit, the slats and the lower list will remain in their present position. On the contrary, by further keeping control circuit active, one obtains raising or lowering of Venetian blind with said slats situated in the extreme position they attain at the end of said predetermined time interval. In relation to the above comments on Danish Patent No. 144 894, it should be emphasized here that said patent specification exclusively deals with stop¬ ping of Venetian blind in uppermost or lowermost posi¬ tion and gives no indication at all regarding adjustment of slats angle in relation to raising or lowering of said lower list. The invention is further explained hereinafter with reference to the schematic drawings, in which Fig. 1 shows a window with Venetian blind and corresponding control device according to the invention, and Fig. 2 shows an embodiment of an electric control circuit for use in a control device according to the in¬ vention. Fig. 1 shows a window 1 comprising a frame 2, a sash 3 and a pane 4. It can be a fixed window or a side hinged window in a vertical wall or a tiltable window in a pitched roof. The following description is made on the assumption that it is a tiltable window of the kind having hinges (not shown) fitted on the two frame and sash side parts of the window. Reference 5 shows a Venetian blind of usual type having a head rail 6 affixed to the uppermost transver- sal part 3a of the sash 3, a number of slats 7, a lower list 8, and matching ladder tapes 9 and lift cords 10. Inside the head rail 6, the front side of which facing the observer, has been taken away for the sake of clarity, there are built-in two spring clutches of e.g. the art known from above-mentioned German Patent Speci¬ fication No. 1,683,007. A common drive shaft connects said ttfo spring clutches with one another and with an electric motor 14, preferably a D.C. motor. The lower list 8 supports a magnet, preferably permanent magnet 15, the function of which will be further explained later. On the lowermost part of the frame 2 there is located an electric contact device 16 which in relation to a contact piece 17 located on the lowermost part of the sash 3 is so arranged as to ensure, when the window is closed, a supply of current to the motor 14 through wires (not shown on the drawings) which may e.g. be wired inside the corresponding sash side part. Said con¬ tact device comprises also a time relay, the function of which will be further explained later. It should be noted that the above-mentioned combination of contact device 16, contact piece 17, and possibly also said time relay may also be located somewhere else on the frame and the sash, e.g. in the uppermost corner of the window or at some other location on the frame and sash side parts. However, the location near the lowermost corner is most convenient in consideration of the activating of contact in relation to the completed closing movement of the window. Furthermore, said contact device 16 compri- ses a reed-contact (not shown) arranged so as to be activated by the permanent magnet 15 on lower list 8, and the function of which will be further explained below in relation to Fig. 2. In case the window is of a type that can be opened and in case one wishes to give the user the possibility of also adjusting the Venetian blind when the window is open, it is obvious that the current supply to the motor 14 must be designed without said combination of contact piece 17 and contact device 16, e.g. with a flexible wiring (not shown) around or near the axis of window hinges or with gliding contacts (not shown) at the hinges. Wires 18 connect said contact device 16 with a unit 19, which comprises the electronic control circuit described below in relation to Fig. 2 and a correspon¬ ding main transformer receiving main voltage through wires 20. It should be noted that in the installation shown here, the control unit 19 has been located in close proximity of the window 1, but if necessary said control unit may be located somewhere else in the corresponding room, remote from the window, in case one wishes a centralized remote control of the Venetian blind. Furthermore, it should be noted that it is not necessary to use main supply, as said electric control may also be driven by means of a battery inside control unit 19, in which case said wires 20 may be disposed of, or from a central remotely located battery, in which case said wires 20 transfer supply current from said central battery to said control unit 19. On the control unit 19 there is a three position switch 21, the function of which will be further explained in relation to Fig. 2. Fig. 2 shows a circuit diagram of an embodiment of a control circuit for the Venetian blind control described above. Apart from the elements already men¬ tioned with reference to Fig. 1, i.e. the three position switch 21, which in Fig. 2 is shown in neutral middle position, the contact connection 16/17 between frame and sash - contact connection established when the frame is closed - the motor 14, the previously mentioned time realy designated here by reference 22 and the reed- contact, which is here designated by reference 23, the control circuit comprises the following components. A main transformer 30, the primary winding of which is feed with main voltage such as 220 V, 50 Hz, provides on its secundary side an AC voltage of e.g. 12 V. By means of four rectifying diodes D1-D4 of usual type, e.g. BAX18, said AC voltage is rectified into a DC voltage between two conductors 31 and 32. An npn transistor i e.g. of BC547-type has its collector connected with the positive conductor 31 and its base connected with said conductor 31 through a resistor Ri of e.g. 4.7 kϊ2. A power transistor T2 of e.g. BD135-type has its collector connected with the positive conductor 31 and its base connected with the emitter of transistor Ti . The emitter of transistor T2 is connected with a resistor R2 of e.g. 1 kΩ, the oppo¬ site end of which is connected with the positive conduc- tor 31. The three position switch 21 as previously men¬ tioned has a neutral position (position shown in Fig. 2) and two active positions 21a, 21c for one set of con¬ tacts and 21b, 2Id for the other set of contacts, respectively. The connecting point between emitter of tran¬ sistor T2 and resistor R2 is connected with contact 21b in the one set of contacts and with contact 21c of the other set of contacts, corresponding to the opposite position of the switch. Furthermore, contact 21a_ in the one set of contacts is connected with contact 21d of the other set of contacts, corresponding to the other posi¬ tion of the switch. The circuitry combination of transistors i and T2 and resistors R^ and R2 described here is known per se and for persons skilled in the art it will be clearly seen that if control transistor 2 is in conducting state and if the window is closed, that is to say if a connection is established between frame and sash through , contacts 16/17 (cf. Fig. 1), a current will be delivered to motor 14 in one direction or the other, depending on which active position switch 21 is. In neutral position of switch 21 motor 14 is not switched on. Said current to motor 14 circulates further through a diode D5, e.g. a BAX18, in parallel with a resistor R5 of e.g. 47Ω and in series with a resistor Rg of e.g. 0.6Ω to return con¬ ductor 32. Control circuit comprises further three opera¬ tional amplifiers OP1, OP2, and OP3 of a type known per s_e, e.g. LM 324. The connecting point between contacts 21a, 21d, anode of diode D5 and resistor R5 is con¬ nected with the negative input of operational amplifier OP1, the positive input of which is connected with cathode of diode D5 and the corresponding end of resistor R5. Depending on the nominal drive current of motor 14 and other circuit parameters, including the value of resistor R5, operational amplifier 0P1 works as a comparator, the output 33 of which delivers a trigger voltage, the value of which shifts from "high" when motor curren I is lower than e.g. 5 mA to "low" when said motor current is higher than 5 mA. Operational amplifier OP2 has its positive input connected with the positive input of operational amplifier OP1 and with the connecting point between cathode of diode D5, resistor R5 and resistor Rg, and alos with the positive input of operational amplifier OP3. The negative input of operational amplifier OP2 and the negative input of operational amplifier OP3 are con¬ nected with return condutor 32. Output 34 of operational amplifier OP2 is con- nected with the anode of a Zener-diode ZDi having a Zener-voltage of e.g. 4.7 V and with the emitter of an npn-transistor T3 of e.g. BC547-type. The collector of transistor T3 is connected with the cathode of Zener- diode ZDi and with the anode of * a second Zener-diode ZD2 having also a Zener-voltage of e.g. 4.7 V. The cathode of Zener-diode ZD2 is connected with resistor R_ and with base of ' transistor T^• Output 33 of operational amplifier 0P1 is con¬ nected with a timer 36, the output of which is connected with base of transistor T3. A conventional RS-flip-flop 37 has its control input S connected with output 33 of operational amplifier OP1 and thereby also with input of timer 36, and its R-input connected with output 35 of operational amplifier OP3, while Q-output of flip-flop 37 is connected with the base of an npn-transistor T4 of e.g. BC547-type. Emitter of transistor T4 is connected with return conductor 32, while its collector is con¬ nected with connecting point between cathode of Zener- diode ZD2» resistor R]_ and base of transistor T^. With the circuitry as described here, operational amplifier OP2 having a gain factor of e.g. 20 is so arranged as to perform readjustment of motor current. Since an AC motor is used here, and as it is known that rotation speed immediately after start of motor tends to drop more or less depending on the charge and depending of voltage drop over resistor Rg - said voltage drop depending actually on the instantaneous value of motor current - operational amplifier 0P2 serves to control the voltage on base of transistor Tj through the series combination of Zener-diodes ZDi and ZD2• The described control device functions as follows. It is assumed that the Venetian blind is an intermediary position as shown in Fig. 1. When the user shifts switch 21 from neutral position to e.g. contacts 21b and 2 d - said position may e.g. be assumed to cor¬ respond to lowering of the Venetian blind - a current goes through resistor R2# motor 14 and resistors R5 and Rg. As long as said current keeps below 5 mA, output 33 of operational"amplifier OP1 activates flip-flop 37, the Q-output of which inhibates transistor T4. Thus, base of transistor Ti goes high and said transistor as well as power transistor 2 are made conducting, whereby resistance value of resistor R2 «is reduced. When operational amplifier OP1 working as com- parator sees that motor current exceeds the threshold value of 5 mA, it triggers timer 36, whereby transistor T3 is made conducting and short-circuits Zener-diode ZD_. Operational amplifier 0P2 is hereby made to regu¬ late control voltage being equal to be the sum of Zener- voltage (e.g. 4.7 V) over Zener-diode ZD2 plus output voltage of operational amplifier 0P2. The motor 14 rota¬ tes now with slow speed and by means of spring clutches 11 and 12 in top rail 6, it produces a slow changing of slats angle in one direction. If the user had decided to shift switch 21 from middle position to the other posi¬ tion (connection through contacts 21a and 21c_) the motor 14 would rotate in the other direction and the angle position of slats 7 will slowly change the other way. When timer 36 indicates that a predetermined time interval has elapsed, transistor T3 is inhibited. whereby Zener-diode ZD^ in switched on and operational amplifier OP2 drives motor 14 at higher speed. Said time interval, which is here supposed to be of 4 sec, which shows to be quite proper for the desired adjustment of slats by the user, may of course be σhoosen different, depending e.g. on the characteristics of the motor, the size, and weight of Venetian blind (smaller or larger windows) and other related parameters. Now, when the slats after expiration of said time interval (e.g. 4 s) are in one of their extreme posi¬ tions, the prior art spring clutch will, by reason of its particular properties, cf. the above mentioned DE Patent Specification No. 1,683,007, and while motor 14 is driven at increased speed, lower said lower list 8 and thereby also the remaining slats 7. When the lower list 8 reaches its lowermost posi¬ tion, said permanent magnet 15 on said lower list 8 activates the previously mentioned reed-contact 23, which is located in or near the contact device 16. As can be seen from Fig. 2, reed-contact 23 is in parallel with motor 14 and it short-circuits said motor, when said lower list 8 reaches its lowermost position. Thereby the current through resistors R2# R5 and Rg increases. The value of resistor Rg is e.g. one hundreth of the value of resistor R5. In the same way as operational amplifier 0P1 in relation to resistor R5, operational amplifier 0P3 senses the current through resistor Rg. When said current - with the values given above - exceeds o.5 A, the operational amplifier 0P3 is activated and its output 35 delivers a reset signal to reset input R of flip-flop 37. Transistor T4, which until now was inhibited, is thereby short-circuited, whereby base of transistor T^ receives a low voltage and feed current to motor 14 (actually at present time to reed-contact 23) is interrupted. If it is now assumed that the user wishes to raise the Venetian blind all the way up, he must shift switch 21 over to its other position (connection with contacts 21a, 2l£) . The same control process as described above occurs now, apart from the fact that motor 14 rotates the other way (and slats 7 to begin with change their angle in the other direction) until lower list 8 reaches its uppermost position. The mecha¬ nical resistance (charge) against rotation of motor results now in the current exceeding 0.5 A, whereby flip-flop 37 likewise is reset in order to interrupt motor current. When lower list 8 is in its lowermost position and magnet 15 activates reed-contact 23, whereby the current by-passes the motor 14, said motor is unable to rotate any more. Thereby, one would obtain a "locked" position, in which the user is not directly able to raise the Venetian blind. In order to obviate such "locking function" in lowermost position, control cir- cuit comprises a timer 22, which is connected with the motor current circuit and with reed-contact 23 and which is so arranged as to define a convenient time interval of e.g. 5 sec. and to only function, when motor current cirulates in the direction corresponding to the lowering of Venetian blind, whereby reed-contact is switched off and locking function of magnet and reed-contact is ter¬ minated. Therafter, the user may at any time activate the switch optionally, e.g. for adjustment of slats angle and then raising of Venetian blind. It should be noted that the control device described here may also be used or a non-openable win¬ dow, e.g. shop window. In that case, the contact connec¬ tion between sash and frame is superfluous and the con¬ tacts 16, 17 shown in Fig. 2 may be disposed of. It should furthermore be noted that the control device described may also be used for Venetian blinds with vertical slats.

Claims: PATENT CLAIMS 1. An electric control of Venetian blind, and of the kind comprising a Venetian blind (5) with head rail (6), lower list (8), slats (7), a drive mechanism with a number of spring clutches (11, 12) for driving a corre- sponding number of ladder tapes (9) and lift cords (10) and a reversible electric motor (14) for driving a drive shaft (13) of said spring clutches (11, 12), charac¬ terized by a control circuit so arranged as to supply current to motor (16) in a predetermined time interval for driving said motor at a first speed in a direction choosen by user for slow change of angle of slats (7) by means of spring clutches (11, 12) and thereafter, when said slats (7) at the elapsing of said time interval has reached one of their extreme positions, to supply motor (14) with a second stronger current for driving said motor (14) at a second higher spfeed in order to obtain in the direction choosen by user raising or lowering of lower list (8) of Venetian blind by means of said spring clutches (11, 12) and corresponding lift cords (10). 2. An electric control according to claim 1, charac¬ terized in that said control circuit comprises a first operational amplifier (0P1) connected to sense motor current and connected with a timer (36) defining said predetermined time interval, and to increase motor current after said time interval has elapsed. 3. An electric control according to claim 2, charac¬ terized in that said control circuit comprises a second operational amplifier (0P2) arranged so as to regulate motor current with increased current intensity after said predetermined time interval has elapsed. 4. An electric control according to claim 1 or 2, characterized in that said control circuit comprises a third operational amplifier (OP3) arranged so as to sense motor current and when motor current exceeds a current value larger than said increased current density and corresponding to motor overload due to stopping of lower list (8) in uppermost position, to activate a reset circuit (37) for interruption of current supply to said motor (14). 5. An electric control according to any of the pre¬ ceding claims, characterized by means (15), preferably a magnet, and by contact means (23), preferably a reed- contact, said means being so arranged as to interrupt current supply to said motor (14) when said lower list (8) reaches its lowermost position. 6. An electric control according to claim 5, charac¬ terized by a time relay (22) arranged so as to define a second predetermined time interval from the moment said lower list (8) reaches its lowermost position and to cause suppression of current interruption function after said second predetermined time interval has elapsed. 7. An electric control according to any of the pre¬ ceding claims, characterized in that said motor (14) is built-in in said head rail (6) and that at least two contacts (16, 17) on window frame (2) and window sash (3), respectively, are inserted in motor current cir¬ cuit.

Inventors: NOERTOFT SOEREN BERTELSEN, NOERTOFT, SOEREN, BERTELSEN
Applicants: RASMUSSEN KANN IND AS, V. KANN RASMUSSEN INDUSTRI A/S
Application year: 1986
Main classification: E06B9
IPC codes: E06B9