VENETIAN BLIND ASSEMBLY METHOD AND APPARATUS

Abstract: A venetian blind assembly method and apparatus in which a flap (36) used to position the rungs (34) of the ladder cords on one side or the other of a plane including the apertures for the lift cords of the blind has its position controlled in a desired manner, e.g. by a solenoid (42).

Description: The present invention relates to an apparatus and method of mechanically assembling the slats of a venetian blind. Venetian blinds consist of at least two ladders, either ladder cords or ladder tapes, each having laterally spaced side members and cross rungs defining openings to receive slats. The assembling can be done manually or by machine and in the latter case, the ladders are intermittently fed lengthwise of the side members and are guided so that two adjacent rungs of each ladder and the portions of the longitudinal side members at the location of the adjacent rungs are held apart, thereby to define a predetermined shape to the associated opening. Slat material is fed along a defined path through the opening. Conventionally the thus assembled slats are individually lifted and stacked and retained by pawls in holder guides and, either during this lifting or after, lift cords are passed down through preformed openings in the slats and attached to a bottom rail. In one embodiment of apparatus for assembling venetian blinds, a guide, in the form of a flap, is provided for each ladder and this flap rocks about a lower generally horizontal pivot from a position on one side of a plane passing vertically through the lift cord apertures in the slats and the other side of this plane, this being caused by the slat material giving to the flap an adequate angular momentum, as the ladders are tautened during raising of a slat, to pass through the vertical position. In this way the ladder cord rungs are alternately positioned first on one side and then on the other side of the lift cord. US-A-4073044 discloses an apparatus for mechanically assembling the slat of venetian blind with at least two ladders said apparatus comprising means for guiding and feeding a length of slat forming material along a defined slat feed path; means for positioning said at least two ladders at different locations longitudinally of said feed path, said ladders each comprising side members and cross rungs, suitably held and spaced to define aligned openings for receiving the slats; means for lifting the individually assembled slats in a direction transverse to said slat feed path to an upper position over a distance effective to position a next cross rung of each ladder directly below said slat feed path; movable ladder guides for accurately positioning each ladder, said ladder guides being movable between a first position and a second position to cause a cross rung to be spaced on one side or the other of the central plane associated with a movable ladder guide. While this may be satisfactory when one is dealing with relatively heavy duty blinds, for example ones having slats with a width of 25mm or so, it is not entirely satisfactory with smaller blinds having a width of, say, 16mm and can give rise to too much friction during the raising and lowering of the blind by lifting and lowering the lift cords. The present invention is characterised by control means to control the movement of said movable ladder guide at any desired time between said first position and said second position and vice versa. The invention also provides a method of mechanically assembling the slats of a venetian blind having a stack of individual slats with vertically aligned openings for the passage of a lifting member with at least two ladders, each comprising two longitudinal side members connected by cross rungs for supporting said slats in the vicinity of said vertically aligned openings, said method comprising the steps of guiding and feeding a length of slat forming strip material along a defined slat feed path; positioning and holding each of said at least two ladders at a different location, longitudinally of said slat feed path, each with its two longitudinal sides of said slat feed path, so as to define at least two aligned slat receiving openings, between a cross rung directly below and a cross rung directly above said feed path; lifting the individually assembled slat in a direction transverse to said slat feed path to an upper stacking position over a distance effective to position a next successive cross rung of each ladder directly below said slat feed path and retaining the assembled slat in an upper stacking position; providing two alternative positions for each cross rung directly below said slat feed path to be on one or other side of the aligned lift cord openings of the assembled slats, longitudinally of said slat feed path; intermittently altering the position of said cross rungs directly below said slat feed path at any desired time after the first three steps have been repeated a number of times. With the method and apparatus of the present invention it is possible readily to control the number of cross rungs which are on one side or the other of the lift cord and preferably the arrangement is such that while, in certain instances, one may have only one cross rung on one side and then one cross rung on the other, as is conventional, one can have the facility for having as many as twenty cross rungs on one side and then an equal or different number on the other side. This greatly reduces the friction problem mentioned above. In the particularly convenient construction, the movable ladder guides are each in the form of a flap pivotal about an axis associated with its lower edge and the control means comprising an electro-mechanical control such as an electromagnet or a fluid pressure operated ram, e.g. a pneumatic ram. Preferably the control means provide a facility for changing the time at which the movable ladder guides are moved between the first position and the second position and vice versa. In a preferred way of carried out the method of the invention, the first and the second of said at least two ladders are held on opposite sides of the aligned lift cord openings associated with a given slat, so that the first and second of said at least two ladders are in mirror-image relation to one another. In order that the present invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:- Figure 1 is a side elevation of one embodiment of assembly apparatus according to the invention; Figure 2 is an enlarged front view of one of the slat assembling stations; and Figure 3 is a side elevation of the station of Figure 1. Referring to the drawings there is illustrated therein a machine frame 10 carrying a reel 12 of slat material 14 which is fed via an accumulator 16 by feed rolls 18 to a cutting and punching station 20. Feed-on rolls 22 feed the cut material to first and second slat assembly stations 24. These are of a conventional design and details of them need not be described. The construction so far described, indeed, is more fully described in United States Patent 4073044. Referring now to Figure 2 one of the stations 24 is indicated in greater detail. Slat material 14 is illustrated being fed past two vertically extending stacking guides 26 each provided with retaining pawls at 28. The slat material 14 is fed through openings 30 (Figure 3) in the ladders which include side members 32 and cross rungs 34. In order to spread the ladders to define a suitable opening for the slat material to be fed therethrough a ladder guide 36 is provided with conventional divergent guide plates 38 mounted on a pivotal flap which is pivotal about a lower edge axis 40. Mounted below the flap is a solenoid 42 the armature 44 of which is connected to a side lever 46 on the flap. Operation of the solenoid 42 will raise the armature 44 and move the flap, which is shown inclined about 30° to the vertical and to the left in Figure 2, to a similar position but to the right. A lift finger 48 is used to raise the slat material which has been laced through the ladder and raise it along the guides 26 to be retained in an upper position by the pawls 28. Each of the slats is provided with an aperture which is aligned with a vertical lift cord needle 50 which is movable along a vertical plane 52 passing through the apertures (not shown) in the slats 14. In a conventional apparatus, which does not employ the solenoid or similar device 42, the cross rungs are alternately positioned one on one side of the vertical plane 52 including the apertures in the slats 14, and then the next on the other side of this plane. With a construction of the present invention, on the other hand, it is possible to leave a number of cross rungs on one side of this plane 52 and a number on the other. In Figure 2 there are illustrated three cross rungs 34 to the left and three cross rungs 34 to the right of this plane. It is contemplated that one can have anything between one and twenty cross rungs to one side of the plane and then to the other side. An electric control circuit (not shown) can be connected to the solenoid 42 to provide any pattern desired of this cross rung arrangement. Instead of having the solenoid 42 one may have pneumatic or other forms of mechanical arrangment to move the flap from one side to the other in a controlled manner.

Claims: Apparatus for mechanically assembling the slats of a venetian blind with at least two ladders said apparatus comprising:- a) means (18,22) for guiding and feeding a length of slat forming material (14) along a defined slat feed path; b) means for positioning said at least two ladders at different locations longitudinally of said feed path, said ladders each comprising side members (32) and cross rungs (34) suitably held and spaced to define aligned openings (30) for receiving the slats; c) means for lifting the individually assembled slats in a direction transverse to said slat feed path to an upper position (28) of a distance effective to position a next cross rung of each ladder directly below said slat feed path; and d) movable ladder guides (36,38) for accurately positioning each ladder, said ladder guides being movable between a first position and a second position to cause a cross rung to be spaced on one side or the other of the central plane associated with a movable ladder guide characterised in that control means (42,44,46) are provided to control the movement of said movable ladder guide at any desired time between said first position and said second position and vice versa. Apparatus according to claim 1, characterised in that said at least two movable ladder guides (36,38) are each in the form of a flap pivotal about an axis associated with its lower edge. Apparatus according to claims 1 or 2, characterised in that said control means comprises an electro-mechanical control means. Apparatus according to claim 3, characterised in that said control means includes an electro-magnet (42). Apparatus according to any one of claims 1, 2 and 3, characterised in that said control means includes a fluid pressure operated ram. Apparatus according to any preceding claim, characterised in that said control means provides a facility for changing the time at which the movable ladder guides are moved between the first position and the second position and vice versa. A method of mechanically assembling the slats of a venetian blind having a stack of individual slats with vertically aligned openings for the passage of a lifting member with at least two ladders, each comprising two longitudinal side members connected by cross rungs for supporting said slats in the vicinity of said vertically aligned openings, said method comprising the steps of a) guiding and feeding a length of slat forming strip material along a defined slat feed path; b) positioning and holding each of said at least two ladders at a different location, longitudinally of said slat feed path, each with its two longitudinal side members laterally spaced and positioned at opposite sides of said slat feed path, so as to define at least two aligned slat receiving openings, between a cross rung directly below and a cross rung directly above said feed path; c) lifting the individually assembled slat in a direction transverse to said slat feed path to an upper stacking position over a distance effective to position a next successive cross rung of each ladder directly below said slat feed path and retaining the assembled slat in an upper stacking position; d) providing two alternative positions for each cross rung directly below said slat feed path to be on one or the other side of the aligned lift cord openings of the assembled slats, longitudinally of said slat feed path; and characterised by intermittently altering the position of said cross rungs directly below said slat feed path at any desired time after steps a) through c) have been repeated a number of times. A method according to claim 7, characterised in that it is possible to change the time at which the position of said cross rungs directly below said slat feed path are intermittently altered between the two alternative positions. A method according to claims 8 or 9, characterised in that a first and a second of said at least two ladders are held on opposite sides of the aligned lift cord openings associated with a given slat, so that said first and second of said at least two ladders are in mirror image relation to one another. A method according to claims 8, 9 or 10, characterised in that the rate of change over is adjustable between being changed once every slat and once every 20 slats.

Inventors: LIM, GUY HUMPHREY
Applicants: HUNTER DOUGLAS INDUSTRIES B.V.
Application year: 1988
Main classification: E06B9
IPC codes: E06B9