Wand operated venetian blind

Abstract

Unless the person closing the blind halts rotation of the wand forthwith upon maximum normal closure of the blind being reached and thereby obviates overpull on the ladders, the tilting action of the tilter of the present invention is automatically suspended to protect the blind against the possibility of deleterious overpull on the ladders by the continued rotation of the wand. At the same time, retrogression of the blind from maximum normal closure is prevented or at least limited.

Description

BACKGROUND OF THE INVENTION

The slats of a wand operated Venetian blind are tilted by manually rotating a wand, also called a baton. The wand rotatively drives the worm of a worm-and-gear tilter. The worm rotates the gear and, by suitable and known means, the movement of the gear is transmitted to the ladders and rendered effective to tilt the slats of the blind by pulling up the rear sidepieces of the ladders while paying out the front sidepieces, or vice versa.

Continued tilting of the slats closes the blind to its maximum normal closure. The point of maximum normal closure, in the usual Venetian blind, is reached before the edge of each slat would move against the face of an adjacent slat; the lift cords interfere with such full closure except in the case of a so-called full closure blind such as, for example, the blind disclosed in U.S. Pat. No. 3,170,505. When the point of maximum normal closure has been reached the person closing the blind ordinarily halts the rotation of the wand. However, a person may fail to timely halt his rotation of the wand; he may be inattentive, or he may suppose that he can close the blind still more by continued rotation of the wand.

When the point of maximum normal closure has been reached, continued rotation of the wand causes overpull on the ladders; and the overpull can become deleterious in one or more ways. The overpull may jamb the top slat against the head of the blind. Also, it may cause the top slat to flip over or try to, particularly in the case of a narrow slat blind. In the case of the blind of U.S. Pat. 3,799,237, in which the top slat coacts with a cord-lock actuator, it is possible for overpull on the ladders to foul the cord lock. In any case, excessive continued rotation of the wand after the blind has reached its maximum normal closure can cause excessive tension to be exerted on sidepieces of the ladders and/or on those rungs of the ladders which are drawing the top slat against the bottom of the head channel.

SUMMARY OF THE INVENTION

The gear of the tilter is a sector of less than 360.degree., whereby the gear can run out of mesh with the worm. Applicant's construction and arrangement are such that, when maximum normal closure of the blind has been reached, the gear is on the verge of running out of mesh with the worm--meaning that small additional movement of the gear would cause the gear to run out of mesh with the worm. At this point the person closing the blind would normally halt his rotation of the wand. Should he fail to do so, the gear will promptly run out of mesh with the worm to suspend tilting action of the tilter before deleterious overpull on the ladders has taken place. Continued rotation of the wand will then be ineffective, and will be harmless accordingly.

Many, perhaps most, Venetian blinds are arranged to be closed by tilting the slats in either direction. If the blind be one which is arranged for closure in either direction the tilter will provide, as regards each direction, for the gear running out of mesh with the worm unless rotation of the wand is halted promptly upon the maximum normal closure of the blind being reached. If the blind be one which is arranged for closure in one direction only, the tilter need provide, as regards that direction only, for the gear running out of mesh with the worm.

The slats of the blind are tilted to closed position by pulling up either the front or the rear sidepieces of the ladders. The pull on the sidepieces means that there is back pull by the sidepieces themselves, and this back pull is fairly strong as the blind approaches maximum normal closure. The back pull is transmitted to the tilter and biases the gear retrogressively. The end tooth of the gear having run out of mesh with the worm, and the thread of the worm having slipped past the end tooth, the retrogressive bias of the gear causes the gear to retrogress a little--the retrogression being arrested by the end tooth of the gear sector engaging the worm convolution somewhat back of the point at which the tooth ran out of mesh with the worm. To prevent, or at least limit, retrogression of the blind from maximum normal closure, the point at which the gear is to run out of mesh with the worm is placed somewhat beyond the point at which maximum normal closure of the blind is reached, whereby all or some of the retrogression of the gear will have taken place before the gear has retrogressed to the point at which maximum normal closure of the blind was reached.

BRIEF DESCRIPTION OF THE DRAWING,

OF WHICH THERE IS ONE SHEET

FIG. 1 is a largely diagrammatic front elevation of a Venetian blind embodying the invention, the "front" of the blind being the face that is toward the room.

FIG. 2 is essentially a front elevation of a fragment of the head of the blind, on a larger scale, a portion of the front wall of the head channel being broken out to reveal the tilter.

FIG. 3 is essentially a section of the head, taken generally on the line 3--3 of FIG. 2. A fragment of the ladder-and-slat assembly is indicated including a fragment of a lift cord. The blind is fully open, the slats being horizontal, i.e., untilted.

FIG. 4 is the same as FIG. 3 but with the blind and tilter at the point of maximum normal closure with the slats tilted forwardly, i.e., tilted with the front edges of the slats depressed.

FIG. 5 is the same as FIG. 3 but with the blind and tilter at the point of maximum normal closure with the slats tilted rearwardly, i.e., tilted with the rear edges of the slats depressed.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT OF THE INVENTION

The drawing shows the presently preferred embodiment of the invention, i.e., the best mode thus far contemplated of carrying out the invention. Except as may be otherwise indicated, the description hereinafter (prior to the claims) refers only to the particular embodiment of the invention that is shown in the drawing. Nevertheless, the disclosure is by way of illustration and example; the claims embrace other embodiments of the invention.

Except for the tilter and the coordination of the tilter with the ladders, both of which will be described and explained later, the blind may be a wand operated Venetian blind of suitable known construction and arrangement, for example, the construction and arrangement disclosed in the U.S. patent of Lorentzen et al. U.S. Pat. No. 3,425,479 issued Feb. 4, 1969. The known construction and arrangement that is disclosed in the present application is the construction and arrangement of the blind of that patent.

A ladder-and-slat assembly that is designated as a whole by 15 is positioned beneath a head which is designated as a whole by 16. The ladder-and-slat assembly includes a series of slats 17 that are supported and articulated together in known manner by two or more ladders 18. Each ladder 18 has a front sidepiece 18a and a rear sidepiece 18b, the two sidepieces being interconnected by vertically-spaced crosspieces or rungs 18c on which the slats 17 rest. The ladder shown is of the "string" type, the sidepieces 18a and 18b being braided cords and each crosspiece 18c being a plurality of filaments which may be braided or twisted into one or more strands.

The had 16 consists primarily of a sheet-steel channel 20 and the mechanism that is contained therein. The channel 20 has a front wall 20a, a rear wall 20b and a bottom wall 20c. Along the upper edges of the front and rear walls 20a and 20b there are longitudinally-extending flanges 20d which are folded inwardly and downwardly. The bottom wall 20c is pierced in known manner (not shown) for passage into the channel 20 of each sidepiece 18a and 18b of the ladders and each lift cord 22 (one shown).

The Venetian blind, designated as a whole by 14 in FIG. 1, is shown diagrammatically as being mounted in conventional manner within a window opening. The head 16 of the blind is mounted on conventional installation brackets 5, one attached to each of the jambs 6 of the window opening. The soffit of the window opening is indicated at 7 and the sill at 8.

The construction, arrangement and operation of the tilter will now be described. The tilter, which is designated as a whole by 40, includes a housing that is mounted in the head channel 20. Journalled within the housing there is a double thread worm 41 and a gear 42. The worm is molded in one piece with a shaft 45 that projects as shown through an opening 20g in the head channel, which opening is spread over an area that includes the juncture of the front wall 20a and the bottom wall 20c. Hanging down in front of the ladder-and-slat assembly 15 (FIG. 1), and suitably connected to the worm shaft 45, there is a wand 38 which is manually rotated to rotatively drive the worm 41.

The wand 38 and its connection to shaft 45 may be as in U.S. Pat. No. 3,425,479. Except for the gear 42, the coordination of the gear 42 with the worm 41 and the coordination of the gear 42 with the ladders 18, the tilter 40 and its mounting in the head channel 20 are the same as in U.S. Pat. No. 3,425,479. FIG. 3 shows the relationship between the worm 41 and the gear 42 when the gear is in mid position, i.e., half-way between its limit of rotation clockwise and its limit of rotation counter-clockwise. As a matter of mechanical convenience in the particular tilter, a radius of the gear 42 does not intersect the worm half-way between the ends of the worm 41 but intersects the worm nearer the top end of the worm.

The gear 42 is a sector of less than 360 degrees, the particular gear shown being a sector which is eight-thirteenths of 360.degree. . The gear is driven by the worm; and rotation of the gear in either direction is limited by the end tooth of the gear section being brought to the worm and then pushed as far as the worm can push it. FIG. 4 shows the relationship between the worm 41 and the gear 42 when the gear is on the verge of running out of mesh with the worm by clockwise rotation. FIG. 5 shows the relationship between the worm 41 and the gear 42 when the gear is on the verge of running out of mesh with the worm by counter-clockwise rotation.

The construction and arrangement of the blind of U.S. Pat. No. 3,425,479 is used in the present instance to transmit the movement of the gear 42 to the ladders 15 and render the movement of the gear effective to tilt the slats 17 by pulling up the front sidepieces 18a while paying out the rear sidepieces 18b or vice versa. As in the blind of U.S. Pat. No. 3,425,479, the gear 42 is coaxial with a steel tilt rod 24 of D-shaped cross section, which rod is also called a D rod. The rod 24 makes a sliding fit with a D-shaped hole 24' in the hub of the gear 42, and the rod extends across the tops of the ladders 15. At the ladders the tilt rod 24 carries drums (not shown) to which the sidepieces 18a and 18b of the ladders are suitably attached, e.g., as disclosed in U.S. Pat. No. 3,425,479.

An increment of angular movement of the gear 42 does not effect a particular increment of tilting movement of the slats 17 regardless of the means by which the movement of the gear is transmitted to the slats or regardless of the width of the slats. What an increment of angular movement of the gear 42 does do is to effect a like increment of angular movement of the tilt rod 24 and the drums that are mounted thereon and to which the ladder sidepieces 18a and 18b are attached. How much the sidepieces of the ladders are raised or lowered by a given increment of angular movement of the drums will be governed by the radius of the drums. And how much the slats are tilted by a particular increment of up and down movement of the sidepieces 18a and 18b will be affected by the distance between the two sidepieces of a ladder which, in turn, is governed by the width of the slats. The net result is that the gear sector 42 should be coordinated with the slats for the particular blind in which the tilter is to be used.

In the blind of U.S. Pat. No. 3,425,479 the drums to which the ladders are attached are in mid position, and the slats are untilted as shown in FIG. 3 of the present application, when the flat of the D-rod 24 is horizontal and is at the top. With the gear sector 42 in the mid rotative position shown in FIG. 3, the necessary rotative indexing of the D-hole 24' in the hub of the gear 42 can be established; the hole 24' will be rotatively indexed to place the flat of the hole 24' horizontal and on top when the drums are in mid position and the slats are untilted. Then the teeth of the gear sector 42 can be layed out. The circular pitch of the teeth and the number on each side of the mid point are selected to have the gear on the verge of running out of mesh with the worm when the slats 17 have been tilted to the point of maximum normal closure of the blind.

In the present case the gear has eight teeth and the eight teeth take up eight-thirteenths of the circumference of the gear 42. The number of teeth being even, the sector has a center pair of teeth rather than a center tooth. In FIG. 3 the center pair of teeth of the gear 42 is in mesh with the worm 41. Proceeding counter-clockwise from the center pair of teeth, the sector is provided with three teeth the end tooth of which is tooth t.sub. 1. Proceeding clockwise from the center pair of teeth the gear sector 42 is provided with three teeth the end tooth of which is t.sub.2 . Rotating the wand in the direction of the arrow in FIG. 4, the end tooth t.sub. 1 is brought to the worm 41 and is on the verge of running out of mesh with the worm when the blind has been brought to its maximum normal closure by tilting the slats forwardly; this is shown in FIG. 4. Rotating the wand in the direction of the arrow in FIG. 5, the end tooth t.sub. 2 is brought to the worm 41 and is on the verge of running out of mesh with the worm when the blind has been brought to its maximum normal closure by tilting the slats rearwardly; this is shown in FIG. 5.

Once maximum normal closure has been reached in either direction, the gear 42 will run out of mesh with the worm 41 unless rotation of the wand 38 is halted promptly. However, a little additional rotation of the gear 42 is required to cause the gear to run out of mesh with the worm. When the gear does run out of mesh with the worm, the gear will retrogress a little as has been explained. But unless the retrogression brings the gear farther back than the point at which maximum normal closure was reached, there will be no retrogression of the blind from maximum normal closure. The retrogression of the blind from maximum normal closure is limited accordingly and may be completely obviated. Preferably each end tooth t.sub. 1 and t.sub. 2 is positioned to keep the gear in mesh with the worm 41 until the angle by which the gear has passed the point at which maximum normal closure was reached is at least as great as the maximum angle of retrogression of the gear when the gear runs out of mesh with the worm. This insures that there will be no retrogression of the blind from maximum normal closure when the gear runs out of mesh with the worm.

It will be seen that the blind is automatically protected against the possibility of deleterious overpull on the ladders by continued rotation of the wand after maximum normal closure has been reached. It will also be seen that retrogession of the blind from maximum normal closure is limited and, preferably, obviated.

In the blind of U.S. Pat. No. 2,174.994 the gear can run out of mesh with the worm at times. The worm is rotated by a cord-driven pulley and the gear is to run out of mesh with the worm only when accumulated slippage of the cord on the pulley is to be corrected.

Claims

What is claimed is:

1. In connection with a Venetian blind that is closed in either direction, i.e., by tilting the slats in either direction from their horizontal position, the slats being tilted by motion transmitted to them from a gear, the gear being rotated by a worm, and the worm being rotated by a manually rotated wand that is connected to the worm,--the method of protecting the blind against deleterious overpull on the ladders and also preventing retrogressive opening movement of the blind from its closed position regardless of the direction of closure, said method comprising:

providing the gear with teeth extending over a portion only of the periphery of the gear and permitting the gear, upon continued rotation of the gear in either direction, to rotate out of mesh with the worm and then retrogress a little,

and selecting the number of teeth on the gear, selecting their position on the periphery of the gear, and selecting their circumferential pitch (a) to cause the gear to be on the verge of rotating out of mesh with the worm upon the blind reaching its closed position in either direction and (b) to permit the gear to rotate out of mesh with the worm at a point that is a little beyond the point at which the blind reaches its closed position and which is at least as far beyond such point as the retrogression of the gear upon the gear rotating out of mesh with the worm.

2. A Venetian blind that is closed in either direction, i.e., by tilting the slats in either direction from their horizontal position, the slats being tilted by motion transmitted to them from a gear, the gear being rotated by a worm, and the worm being rotated by a manually rotated wand that is connected to the worm--wherein the improvement comprises:

the gear is a sector of less than 360.degree. and is on the verge of rotating out of mesh with the worm upon the blind reaching its closed position in either direction, the gear retrogresses a little upon rotating out of mesh with the worm,

and the point at which the gear rotates out of mesh with the worm is a little beyond the point at which the blind reaches its closed position and at least as far beyond such point as the retrogression of the gear upon rotating out of mesh with the worm,

whereby the retrogression of the gear takes place entirely beyond the point at which the blind reaches its closed position and, thereby, the blind is protected against retrogressive opening movement.