Patent GB-684815-A (GB)
Title: Improvements in or relating to venetian blinds
IPC: E06B9/308
Filed: 1951-03-08
Abstract: 684,815. Venetian blinds. ROLLADENFABRIK A. GRIESSER AKT.-GES. March 8, 1951 [March 9, 1950; March 17, 1950]. No. 5659/51. Class 20 (iii). A venetian blind has lath carrying ladder bands 12, 13, suspended on pivoting frames 7, 8, 9, loosely mounted on a rotatable lath winding shaft 2, flexible pull members 22, 45, 87, depending from winding drums 18 on the shaft 2 through the superposed laths 14, 79 and attached to the lowermost lath for raising and lowering the blind on operation of shaft 2, and a coupling device rendered effective by the unwinding pull member when the blind arrives at its lowermost position to connect the shaft 2 with the pivoting frames 7, 8, 9, whereby further operation of the shaft 2 causes the frames to turn with the shaft to tilt the lowered slats into open, closed, or inclined position. The shaft 2 mounted on bearings 3 in channel-shaped casing 1 may be driven in both directions, e.g. by a crankshaft, through a gear 4 and friction clutch 5, the latter preventing rotation of the shaft under the influence of the weight of the laths. A sleeve 6 rotatably mounted on shaft 2 carries at both ends diametrically opposed arms 7 which are rigidly connected by pins 8 to arms 9, also rotatable on shaft 2. Two chains 10, 11, are suspended on each of pins 8, pass through slots 15 in the casing, and connect at their lower ends to the bands 12, 13. A spiral spring 16 on shaft 2 abuts at one end against the casing 1 and at the other against an arm 9 to urge the two frames 7, 8, 9 against an abutment 17 on the casing. A winding drum 18 with a peripheral groove is secured on shaft 2 between each pair of arms 7 and 9, and a steel tape 22 is attached at one end to the bottom of the groove and wound on the drum before passing from the casing between guide rollers 23 and through a slot 24 in each lath to be attached to the lowermost lath. A spiral spring 26 in a radial opening 25 of the drum 18 bears at one end against the shaft 2 and at the other against a pin 27, which moves in radial slots 28 of the drum. The pin 27 carries two bolts 29, which are located within the circumference of the drum, as in Fig. 4, when the spring 26 is compressed by the tape 22 wound on the drum. When the blind is partially lowered, the slats are held by the spring 16 in the position shown in Fig. 4, but when fully lowered the tape 22 is fully unwound and spring 26 urges bolts 29 outwardly, as in Fig. 7, and when the shaft is further turned the bolts 29 engage the lower pin 8 and rotate frames 7, 8, 9 around shaft 2 against spring 16, the slats becoming fully opened as in Fig. 7, or, on further rotation, fully closed and sloping in the opposite direction to that shown in Fig. 4, the arm 7 then abutting the stop 17 and preventing further rotation. The laths are maintained at any required angle by means of friction clutch 5. To raise the blind the rotation of shaft 2 is reversed, the slats being turned by spring 16. Rotation of the slats at intermediate positions of the blind is performed by means of a cam and pawl. The cam 31 is formed on a sleeve attached to shaft 2 adjacent a frame 7, 8, 9. Two annular discs 34, 35 are rigidly connected to the arm 9 and carry a pin 37 on which the pawl 38 is pivotally mounted so that the heavier end 39 of the pawl coacts with cam 31, the pin 37 being normally located above shaft 2. The cam has a recess 40 and a notch 41 separated by a nose 42, so that when the laths are lowered by rotating shaft 2 the pawl end 39 slides over the cam, over the recess 40, and up nose 42, and jumps over notch 41 if the shaft is turning rapidly, but into notch 41 if the shaft rotates slowly, when rotation of shaft 2 rotates the pawl and hence frame 7, 8 9 and the slats. The slats are held at the required angle by clutch 5. When shaft 2 is further turned the end 44 of the pawl is moved radially inwardly by contact with the inclined surface 43 on the casing, the pawl pivoting and disengaging from the cam, when the spring 16 returns the slats. Fig. 13 shows a modified construction, the slats being raised by a cord 45 which is wound in adjacent spirals on a drum 46 on shaft 2, the shaft and drum moving laterally on rotation as the threaded end 48 of the shaft engages on threaded nut 49, the shaft maintaining contact with the driving gear during the axial movement. The drum has a helical groove 50 to receive the first cable winding which compresses spring bolts, similar to bolts 29. A drum shaped cam 31<SP>1</SP> and a pawl 38 act as the cam and pawl described above to adjust the slats at intermediate positions of the blind, the cam 31<SP>1</SP> moving axially with the shaft. In the modification shown in Figs. 18, 19 the shaft 2 has a square end engaged in a socket of a shaft 63 carrying a winding drum 64 with a draw rope 65, and carries a rotatable sleeve 70 with spring frames 72, 73, 74 urged by spring 81, 82, and winding drums 84 for the lifting tapes 87. The other end of the shaft is threaded at 88 and rotatably mounted in the casing, a nut 90 engaging the thread 88 is prevented from rotating by a guide bar 91 while its axial movement is limited by a stop 92, thus limiting the rotation of shaft 2 and the downward movement of the blind. When the blind is lowered the tape 65 is wound on drum 64, the end of the tape passing over a guide roll 95, and being held by a clamping device at the lower part of the window frame. The blind is lowered by the weight of the laths when the clamping device is released. The angular position of the laths is adjusted as above by means of a pawl 101, a cam disc 102 which has two diametrically opposed recesses 103, two notches 104 and two noses 105, and a release abutment 108. The slats are held in any required position by reason of the clamping device holding tape 65. The blind is arranged between the glass plates a, b of a double window, the casing being carried in the two-part window frame 66, 67, and the completed structure is mounted e.g. pivotally, in the fixed frame c.