VENETIAN BLIND LIFTING AND TILTING MECHANISM

Abstract: An operating mechanism for the slats of a venetian blind in which a rotatable member (18) includes means (20) for raising and lowering a lift element (22), the rotatable member (18) being driven by a drive shaft (16) which also rotates a sleeve (26) provided with an external thread (30) engageable with a traversing nut (36) upon which is mounted a rotatable cam member (74). The sleeve (26) is provided with a key (34) which engages an abutment (84) on the cam member (74) when the latter reaches the end of its movement on the sleeve (26), the cam member disengaging a stop (60) on the resiliently retractable member (64), to disengage a clutch actuating member allowing the latter to rotate to allow a clutch (116) to engage upon the member (18), thereby causing tilt member (92) to rotate to tilt the ladder cords (94) of the venetian blind only at the end of movement of the nut (36).

Description: The present invention relates to an operating mechanism for the slats of a venetian blind. The invention is particularly, although not exclusively, concerned with an operating mechanism for an external venetian blind mounted on the exterior of a building. Various proposals have been made for single operating mechanisms in which a single control is used both to raise and lower the blind and to cause tilting of the slats of the blind when lowered or partly raised. Examples of such blinds are shown, for example, in AT-A-359262 and 354042, in DE-A-3625365 and in EP-A-0097627. In particular DE-A-3625365 discloses an operating mechanism for the slats of a venetian blind, said mechanism comprising a housing adapted to receive a drive shaft rotatable about its axis and adapted to pass through said housing, a rotatable member mounted in said housing adapted to be rotated by said drive shaft in either of two opposite directions, a pivotal tilt element releasably engaged with said rotatable member, said tilt element being adapted to support the slats and to tilt the slats so supported between opposite end positions, a clutch mechanism interposed between said rotatable member and said tilt element, clutch actuating means for releasing said clutch in each of said opposite end positions and rotationally spaced arresting means associated with said clutch actuating means determining the limits of tilt. These constructions are all relatively cumbersome and complex and it is an object of the present invention to provide alternative structures which can be made compact and relatively inexpensively. The present invention is characterised by a retractable stop engageable with at least one said arresting means in an intermediate tilt position between said opposite end positions, whereby, when said stop is engaged with said at least one arresting means, the clutch mechanism is disengaged and rotation of said rotatable member does not cause further rotation of said tilt element beyond said intermediate position, a sleeve adapted to surround said drive shaft and rotatable therewith, said sleeve extending axially outwardly of said clutch actuating means, a radially projecting key associated with said sleeve adjacent to said clutch actuating means, an external thread formed on said sleeve, a translating member driven by said external thread, whereby when the sleeve is rotated, the translating member is caused to move axially of the sleeve, a cam member intermediate said translating member and said housing for rotation relative thereto, a cam surface on said cam member, an abutment formed on an end surface of said cam member facing said radially projecting key, said abutment engaging said key as the translating member moves axially to an end position on said sleeve after a predetermined number of revolutions in that particular direction, whereupon said key rotates said cam member which then acts at least temporarily to retract the stop from said at least one arresting means and thereby allows engagement of the clutch mechanism and thus rotation of the tilt element from said intermediate position to one of said opposite end positions. Such a structure can be made extremely compactly and yet can be designed to operate accurately and effectively even, for example, in what can be a hostile environment on the exterior of a building. Furthermore, the structure can be operated regardless of the mechanism used for raising and lowering the blind. The above structure uses the externally threaded sleeve as a timer to control, as a function of the length of the sleeve, and therefore the number of rotations for the full translation of the translating member, the amount of drop of the venetian blind before the translating member is stopped and before tilting commences. If desired, the threaded sleeve may be designed to be extended by an additional identical part to provide for increased vertical drop of the venetian blind requiring a larger number of revolutions of the rotatable member and thus of the drive shaft. In a preferred construction, the sleeve is mounted externally of the housing and it can then be axially retained by the housing by means of a circumferential groove formed at a location near one end of the sleeve, the groove being engaged by a portion of the housing. Preferably, the translating member is in the form of a nut threaded onto external thread of the sleeve and wherein the nut has an edge surface adapted to slide along an inner surface of a venetian blind headrail in which the mechanism is mounted, to prevent said nut from rotation. While the cam member can be connected to the nut in a number of ways, preferably the nut includes a bearing journal for the cam member, the bearing journal being provided with a chordal flat surface, a flat spring member being mounted in the cam member and engaging said bearing surface, the flat surface providing a preferred initial orientation of the cam member with respect to said nut. The nut and cam member may be rotatably connected by a snap fit connection. Advantageously, the nut has a first stopping element cooperating with a second stopping element on the cam member for limiting rotation of the cam member in both directions. In order to prevent the nut from rotation, the nut preferably has an edge surface (or two edge surfaces) adapted to slide along an inner surface or surfaces of the venetian blind headrail on which the mechanism is mounted. The cam member preferably has a resiliently deflectable detent extending adjacent said abutment, said detent being surmountable upon deflection in one direction and engaging with said radially projecting key on return movement of the key to return the cam member to its initial position. The retractable stop may take many forms and could, for example, be in the form of a pivotal torsion element. In a preferred construction, however, the retractable stop is slidably retained on the housing and is resiliently biassed towards engagement with the arresting means. One advantageous form of the clutch actuating means comprises a clutch actuating member mounted coaxially of the shaft and having associated therewith three rotationally spaced engagement surfaces, while the outer two engagement surfaces determining said opposite end positions upon engagement with the retractable stop. The central engagement surface on the clutch actuating member will then form an abutment for the intermediate tilt position and the clutch actuating member may be provided with portions which may be broken away to provide alternative locations of said surfaces to preselect different amounts of tilt of the slats. The rotatable member may include a tape reel for winding lift tape for raising and lowering the bottom rail of a blind and may also include an axially extending hub on which the tilt element is mounted, and a clutch sleeve surrounding said hub. The clutch mechanism may comprise a helically wound spring carried by the tilt element, the spring surrounding the axially extending clutch sleeve and having radially extending spring ends, the clutch actuating member including an axially extending finger extending between the spring ends, the arrangement being such that engagement of one of said radial spring ends with said axial finger results in the opening up of said spring windings and disengagement from said hub and thus disengagement of the clutch mechanism, when the actuating member is arrested by one of the detents against the retractable stop. The tilt element may comprise a ring element coaxial with the helically wound spring and a circumferential recess accommodating both radially extending spring ends as well as said axially extending finger located therebetween. 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 schematic exploded perspective view of one embodiment of operating mechanism according to the present invention; Figure 2 is an axial cross-section through the nut and cam member of the mechanism of Figure 1; Figure 3 is an end elevation of the cam member as viewed from the left in Figure 1; and Figures 4 and 5 are schematic end views showing movement of the cam follower by the cam member and the resulting tilting of the blind slats. The construction of operating mechanism illustrated in Figure 1 includes a headrail 10 of conventional design in which is mounted (by means not shown) a housing 12 having a dismountable cover 14. Extending axially through the headrail 10 is a rotatable drive shaft 16 on which is engaged a rotatable member 18 having a suitable square cross-section aperture therethrough. The rotatable member 18 includes a reel 20 for a venetian blind lift tape 22 and an axially extending hub 24. Mounted externally of the housing 12 is a sleeve 26 provided with a square cross-section bore 28 engageable by the drive shaft 16, the sleeve having an external thread 30 along its length. At its outer end this sleeve is provided with a step 31 which enables it to be connected to an identical sleeve if one wishes to extend the length of the sleeve. At its inner end the sleeve is provided with a flange 32 carrying a radially projecting key 34. Threaded onto the external thread 30 is a nut 36 including an internally threaded bearing journal 38 which threadably engages the external thread 30. The nut 36 includes a radial wall 40 of generally rectangular shape provided with edge surfaces 42 for engagement with the inner wall of a headrail 10 and on its inner face (on the left of Figure 1) is a first abutment member element 44 in the form of a projection. A housing end wall 46 is shown at the right side of the housing 12, and includes a cut-out 48 of generally rectangular shape having a semi-circular bottom. On the outside of this housing end wall 46 is formed a guide 50 having two facing tracks 52. As can be seen, in the cut-out portion in Figure 1, the very end of the sleeve 26 is formed with a peripheral groove 54 engageable with the tracks 52 to prevent this sleeve from moving axially. Also movable in the guide 50, within the tracks 52, is a retractable stop member 56 having, on its outer surface, a cam follower projection 58 for a reason to be described below. Directly opposite the cam follower projection 58 is an inwardly directed stop 60 which passes through a slot 62 in the end wall 46. A spring 64, which is of generally L-shape and includes a first arm 66 and a second arm 68 is arranged to engage the lower surface of the cam follower projection to urge the stop member upwardly. The upper end of the second arm 68 is provided with an inverted V-shaped end portion 70 which can be pushed into a pocket 72 formed on the exterior of the end wall 46. When the spring has been pushed upwardly into this pocket the resilience of the inverted U-shaped portion will effectively prevent downward movement of the spring 64. Associated with the nut 36 is a cam member 74 having a peripheral cam surface 76. In order to mount the cam member on the nut 36, the cam member includes an outer journal sleeve 78 which engages over the internally threaded bearing journal 38 on the nut 36. Mounted within the outer journal sleeve is a flat spring 80 which extends substantially along a chord of the cam member and engages a chordal flat surface 82 on the outer surface of the bearing journal 38 of the nut. An annular rib 83 engages in a groove in the nut to hold the cam member on the nut as a snap fit. The spring 80 provides a preferred orientation of the cam member with respect to the nut by engagement with the flat surface 82. However, relative rotation is still possible. Formed within the cam member 74 is an abutment 84 which extends generally radially and, in the construction illustrated, is in the form of a recess in the front face (that is to say the left face as seen in Figure 1) of the cam member. The recess is also partly delimited by an arcuate resilient finger 86 which is cantilevered from its right end, as seen in Figure 1, and is provided with a stepped free end 88. The outer surface of the cam member is provided with a second abutment member 90 which can engage with the first abutment member 44 on the nut 36. Returning now to the left hand end of Figure 1, it can be seen that mounted on the rotatable member 18 is a tilt element 92 on which are supported the ladder cords 94 of the venetian blind, these ladder cords may have extended therebetween rungs 96, for carrying slats 98 (see Figures 4 and 5). These Figures also illustrate the bottom rail 100 which is supported by the lift tape 22 wound on the reel 20. The tilt element 92 is formed with a peripheral wall 102 having an arcuate opening 104 formed therein. Radially outwardly of this opening is a holding wall 106 including a central notch 108 into which are engaged means for locking the ladder cords 94. An axially extending bearing in the form of a sleeve 110 is formed on the interior of the annular tilt element and this engages on the axially extending hub 24 of the rotatable member 18 to allow the tilt element to pivot relative thereto. Positioned within the peripheral wall 102 is a coil clutch spring 114 having two free ends 116 projecting generally radially, the free ends being accommodated within the opening 104 with significant clearance on either side. The spring 114 is sprung open somewhat and overlies a clutch sleeve 112 on the rotatable member 18 which is mounted coaxially with the hub 24 thereof. When the spring 114 is engaged on the clutch sleeve 112 it will cause the tilt element 92 to rotate with the rotatable member 18. Mounted within the housing adjacent the tilt element 92 is a clutch actuating member 118 of generally annular shape. The clutch actuating member is provided with three circumferentially spaced arresting surfaces formed by first and second outer detents 120, 122 and an intermediate detent 124, these detents being positioned to be engageable by the stop 60 mounted on the retractable stop member 56. Facing generally to the left, as seen in Figure 1, the clutch actuating member 118 is provided with a finger 128 positioned to engage one or the other of the spring ends 116. Normally, when the rotatable member 18 is caused to rotate by the drive shaft 16, one of the spring ends 116 will abut one side of the finger 128, which will cause the clutch actuating member 118 to rotate with it until, for instance, the intermediate detent 124 engages the stop 60, whereupon the finger 128 causes the spring to open slightly, thereby allowing the clutch to slip, whereby the tilt element 92 will not rotate. When, however, the retractable stop member 56 is caused to move downwardly and the stop 60 moves out of engagement with one of these detents, and this will allow rotation of the actuating member 118 which will release the spring end whereby the spring will clamp onto the clutch sleeve 112, this causing the element 92 to rotate slightly with the rotation of member 18. In order to cause this to happen, operation of the cam member must take place. If one starts, for example, with the blind fully elevated, and operates the drive shaft 16, e.g. by an electric motor or by hand crank, then the reel 20 will rotate allowing the blind to be lowered. As this happens the sleeve 26 will rotate with the drive shaft and, because the nut is prevented from rotating by the edge surfaces 42 engaging the headrail, the nut will move under the action of the internally threaded bearing journal 38 and the screw thread 30, axially along the sleeve carrying the cam member 74 with it. During this process, the clutch spring 114 will be disengaged through the intermediate detent 124 and so the tilt element will not rotate beyond its corresponding intermediate position. The length of the sleeve 30 is chosen so that, as the blind nears its lowermost position, so the nut will reach an axial position so that the front face of the cam member 74 will just be approaching the key 34. The key will engage in the abutment 84 and will cause the cam member to rotate with it. The cam surface 76 is so shaped that the cam follower 58 will be forced downwardly against the action of the spring 64 and the stop 60 will temporarily disengage from the intermediate detent 124. However, the cam member will then have rotated to a position in which the cam no longer presses down on the cam follower 58 so that the stop member 56 will rise and the stop 60 will engage the outer detent 122. The finger 128 will then bear against the right hand spring end 116 thereby opening the spring and causing the clutch to slip. Further rotation of the drive shaft will eventually come to a halt when the second abutment member 90 on the cam member engages the first abutment member 44 on the nut from an opposite side. In this manner it can be prevented that the lift tape 22 will be unreeled to an extent that it starts rewinding in the wrong rotational sense. As explained above, this will allow the actuating member 118 to rotate thereby engaging the clutch and causing the tilt element 92 to rotate with the reel. In the normal course of events the stop member will then be engaged against the intermediate detent 124 so that the blind will be raised or lowered in an intermediate position as, for example, illustrated in Figure 4. As the clutch is released, the clutch actuating member 118 will rotate with the sleeve. If the operating handle or motor is then reversed, the drive shaft 16 will cause rotation in a clockwise direction. The key 34 will engage the stepped end portion 88 of the finger 86 and cause the cam to rotate back thereby depressing the cam follower 58 and allowing the stop to ride over the intermediate detent 124 as the actuating member 118 rotates in a clockwise direction. The resilience of the finger 86 will then allow the finger to lift and there will be a limited amount of rotation allowed for the key 34 before it entirely disengages from the finger and by this time the nut 36 will have moved further to the right and the second abutment member 90 hits the first stopping member 44. The detent 120 will then strike the stop 60 thereby disengaging the clutch and stopping rotation of the tilt element 92. In this way full opening of the slats can be achieved as illustrated in Figure 4. If it is desired to alter the extent of this and indeed to alter the position of the intermediate angling of the slats, then one or more of the breakout portions 126 can be snapped out, thereby to give a longer arcuate path before the stop touches one or more of the detents 120, 122, 124. It will be appreciated that the above described construction is very compact and can be made significantly less expensively than the known constructions. The term "housing" used herein is to be read to cover not only a structure as illustrated, but also any form of frame, wall(s), support(s), locatable in, or forming part of, the blind headrail. Any such "housing" needs to be able to support the various components of the mechanism, such as the stop, clutch actuating member and cam member relative to one another. Similarly, the term "radially projecting key" is to be read to cover any element capable of operating the cam member at the end of travel of the translating member. For example the translating member could include an internal peripheral groove housing a ball which could run in a helical groove on the exterior of the sleeve to cause the member to be translated along the sleeve and when the ball reaches the end of the groove it would be stopped and then caused to rotate the cam member. In such a construction the ball forms the key.

Claims: An operating mechanism for the slats of a venetian blind, said mechanism comprising a housing (12) adapted to receive a drive shaft (16) rotatable about its axis and adapted to pass through said housing, a rotatable member (18) mounted in said housing adapted to be rotated by said drive shaft in either of two opposite directions, a pivotal tilt element (92) releasably engaged with said rotatable member (18), said tilt element being adapted to support the slats and to tilt the slats so supported between opposite end positions, a clutch mechanism (112,114) interposed between said rotatable member and said tilt element, clutch actuating means (118) for releasing said clutch mechanism in each of said opposite end positions and rotationally spaced arresting means (120,122,124) associated with said clutch actuating means determining the limits of tilt, characterised by a retractable stop (56) engageable with at least one said arresting means in an intermediate tilt position between said opposite end positions, whereby, when said stop is engaged with said at least one arresting means, the clutch mechanism is disengaged and rotation of said rotatable member does not cause further rotation of said tilt element beyond said intermediate position, a sleeve (26) adapted to surround said drive shaft and rotatable therewith, said sleeve extending axially outwardly of said clutch actuating means (118), a radially projecting key (34) associated with said sleeve adjacent to said clutch actuating means, an external thread (30) formed on said sleeve, a translating member (36) driven by said external thread, whereby when the sleeve is rotated, the translating member is caused to move axially of the sleeve, a cam member (74) intermediate said translating member and said housing for rotation relative thereto, a cam surface (76) on said cam member, an abutment (84) formed on an end surface of said cam member facing said radially projecting key, said abutment (84) engaging said key (34) as the translating member moves axially to an end position on said sleeve after a predetermined number of revolutions in that particular direction, whereupon said key rotates said cam member (74) which then acts at least temporarily to retract the stop (56) from said at least one arresting means (120,122,124) and thereby allows engagement of the clutch mechanism (112,114) and thus rotation of the tilt element (92) from said intermediate position to one of said opposite end positions. A mechanism according to claim 1, characterised in that said sleeve (26) is mounted externally of said housing and/or said sleeve is axially retained by the housing by means of a circumferential groove (54) formed at a location near one end of the sleeve, said groove being engaged by a portion (52) of the housing. A mechanism according to claim 1 or 2, characterised in that said translating member (36) is in the form of a nut threaded onto said external thread (30) of the sleeve and in that the nut has an edge surface (42) adapted to slide along an inner surface of a venetian blind headrail (10) in which the mechanism is mounted, to prevent said nut from rotation. A mechanism according to claim 3, characterised in that said nut includes a bearing journal (38) for the cam member (74), said bearing journal being provided with a chordal flat surface (82), and in that a flat spring member (80) is mounted in the cam member and engages said flat surface (82), the flat surface providing a preferred initial orientation of the cam member with respect to said nut. A mechanism according to claim 3 or 4, characterised in that said nut has a first stopping element (44) cooperating with a second stopping element (90) on the cam member for limiting rotation of the latter in both directions. A mechanism according to any preceding claim, characterised in that said cam member (74) has a resiliently deflectable detent (86) extending adjacent said abutment, said detent being surmountable by said radially projecting key (34) upon deflection in one direction and engaging with said radially projecting key upon return movement of the key, to return the cam member to its initial position. A mechanism according to any preceding claim, characterised in that said retractable stop (56) is slidably retained on said housing and is resiliently biassed towards engagement with arresting means (120,122,124). A mechanism according to any preceding claim, characterised in that said clutch actuating means (118) comprises a rotatable clutch actuating member mounted coaxially of the shaft and has associated therewith three rotationally spaced engagement surfaces (120,122,124), the outer two engagement surfaces (120,122) determining said opposite end positions upon engagement with said retractable stop and in that the central engagement surface (124) on said clutch actuating member forms an abutment for the intermediate tilt position. A mechanism according to claim 8, characterised in that said clutch actuating member (118) is provided with portions (126) which may be broken away to provide alternative locations of said engagement surfaces to preselect different amount of tilt of the slats. A mechanism according to claim 8 or 9, characterised in that said rotatable member (18) includes an axially extending hub (24) on which said tilt element (92) is mounted, and a clutch sleeve (112) associated with said hub, in that said clutch mechanism comprises a helically wound spring (114) accommodated by said tilt element, said spring surrounding said axially extending clutch sleeve and having radially extending spring ends (116), and in that said clutch actuating member (118) includes an axially extending finger (128) extending between said spring ends, the arrangement being such that engagement of one of said radial spring ends with said axial finger results in the opening up of said spring windings and disengagement from said sleeve and thus disengagement of said clutch mechanism, when the actuating member is arrested by one of its detents against the retractable stop member. A mechanism according to claim 10, characterised in that said tilt element (92) comprises a ring element coaxial with said helically wound spring and comprises a circumferential recess (104) accommodating both radially extending spring ends (116) as well as said axially extending finger (128) located therebetween. A mechanism according to any preceding claim, characterised in that said rotatable member includes a tape spool (20) for winding lift tape for raising and lowering the bottom rail of a blind.

Inventors: OSKAM, HERMAN
Applicants: HUNTER DOUGLAS INDUSTRIES B.V.
Application year: 1988
Main classification: E06B9
IPC codes: E06B9