Abstract:
An automotive HVAC system controls two side by side film belts with a single drive motor. Two co planar wind up rollers, one for each belt, have inboard ends that are indirectly connected by a rotation transmission means that has a defined level of turning “slack”. Rotation is transmitted from one wind up roller to the other only after the slack has been taken up, allowing a certain degree of offset between the two belts. When a first belt is turned past a first position, it eventually moves the other belt to a new position, with the defined belt offset maintained. The first belt can then be turned back, breaking the indirect connection between the two shafts.

Description:
TECHNICAL FIELD 
     This invention relates to air conditioning and ventilation systems in general, and specifically to a system that can drive two separate film belts to substantially differing locations with a single drive motor. 
     BACKGROUND OF THE INVENTION 
     Flexible, rolling film belts are finding increasing acceptance as an alternative to bulkier, and non linear, swinging doors. A typical system uses a belt with one or more apertures that rolls back and forth from a powered wind up roller onto a passive, take up roller. Any fraction of the belt aperture can be aligned with a duct or frame opening to achieve a corresponding degree of air flow. A flat belt is also inherently more compact than a swinging door. 
     Newer automotive HVAC systems often provide for multi zone (individual occupant) air flow rate or temperature control, or both. To achieve independent control with a film belt system, separate film belts capable of at least substantially independent movement are required. Typically, this would also require a separate drive motor to turn the wind up roller of each belt. The motor is one of the more expensive and space consuming elements of the system. 
     SUMMARY OF THE INVENTION 
     The subject invention provides a means for driving two separate film belts with a single motor. In the preferred embodiment disclosed, first and second apertured belts are arranged side by side and substantially co planar, with first and second wind up rollers arranged on a common central axis. The two wind up rollers run on separate shafts, with axially spaced inboard ends. Each wind up roller inboard end has an axially extending, narrow drive lug thereon, which rotates about the central axis, but there is no direct overlap between the drive lugs, and no direct interconnection between the wind up rollers&#39; in board ends. Instead, in the axial space between them, a rotation transmission mechanism comprised of one or more annular members rotates freely on a shaft coaxial to the central axis. Each annular member has a pair of oppositely axially extending contact lugs, the outboard ones of which are engageable with the wind up roller drive lugs, and the inboard ones of which are mutually engageable. A single motor directly drives only the first wind up roller, in response to a conventional controller that can sense either actual belt position or roller position. 
     The presence of the one or more freely rotating members between the two wind up rollers allows for driving engagement between the two when, but only when, the first wind up roller has been turned far enough in either given direction to remove all of the “slack” from the system. That is, when all of the various drive and contact lugs are mutually engaged. Assuming that the separate belts start out with their apertures in an aligned position, but with some slack in the system, the single motor turns only the first windup roller until the point that all of the various lugs make contact with one another. During this initial movement, the first belt moves, but the second belt does not, so the two belt apertures move into an “offset” relative position. Once contact is made, the second wind up roller begins to move as well, and both belts move in the same direction, while maintaining the offset. When the second belt has been moved to a desired position, the motor and first wind up roller can be moved back in the opposite direction, moving the first belt aperture back, but without moving the second belt, until the point where all of the lugs mutually contact again in the opposite direction. At that point, further movement of the first wind up roller would again move both belts, but with a reversed relative offset between the two belts. The amount of total relative belt offset available would be set by varying the total number of annular members, and thereby varying the total number of roller turns possible while the system is “slack”. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will appear from the following written description, and from the drawings, in which: 
     FIG. 1 is a plan view of two separate film belts in a system according to the invention; 
     FIG. 2 is a perspective view of the inboard ends of the two wind up rollers and the rotation transmission means; 
     FIG. 3 is an exploded version of FIG. 2; 
     FIG. 4 is a view similar to FIG. 1, showing a starting point of the two belts prior to attaining a moved position, while there is still slack in the system; 
     FIG. 5 shows the relative belt position at the point where slack has been taken out of the system; 
     FIG. 6 shows the relative belt position just as the desired new position of the second belt has been attained; 
     FIG. 7 shows the first belt being shifted back in the opposite direction to break the indirect connection; 
     FIG. 8 shows the first belt having been moved far enough to again remove the slack from the system and shift the second belt in the opposite direction. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, a preferred embodiment of the invention is indicated generally at  10 . The invention is intended for use in a multi zone automotive HVAC system, most of which is not illustrated, but will be familiar to those skilled in the art. The subject invention could, for example, be used to control air flow through a heater core, and thereby substantially independently vary the temperature between two or more occupant zones (two as disclosed). A controller would be available that could sense and respond to either belt position, or the number and direction of roller turns, or both. The presence and availability of these standard features should be understood, but they do not directly comprise an element of the subject invention. A first flexible film belt  12  with a set of apertures  14  rolls back and forth between a first wind tip roller  16  and a first take up roller  18 . “Wind up” roller, as opposed to “take up” roller, indicates an active, powered condition, although either roller may be winding out, or taking up, the belt material, depending upon the direction of belt movement. Adjacent to, and coplanar with, first belt  12  is a separate flexible film belt  20 , which winds back and forth between a second wind up roller  24  and a second take up roller  27 . The wind up rollers  16  and  24  are co axial, on a central axis A, but there is no direct connection between them. The first wind up roller  16  is directly powered by a single power means, such as by an electric motor  26 , but the second wind up roller  24  is only indirectly powered, as described below. 
     Referring next to FIGS. 2 and 3, additional detail of the indirect connection between the two wind up rollers  16  and  24  is illustrated. Each wind up roller  16  and  24  turns on a separate center shaft  28  and  30  respectively, which lie on central axis A. Each wind up roller also has an inboard end  32  and  34  respectively which rotates one to one there with. Conveniently, each inboard end  32  and  34  may be a separate end piece, as shown, fixed to rotate one to one with the respective wind up roller  16  and  24 . Each inboard end  32  and  34  has an integral drive lug  36  extending parallel to central axis A, in opposite directions, and with the same radial spacing from axis A, but with no overlap or contact with each other. Each drive lug  36  and  38  is circumferentially discrete, that is, it is relatively narrow, and only as wide as necessary for strength considerations. Each inboard roller end  32  and  34  would be radially supported by some means that did not block the axial space therebetween, as by a plane bearing (not illustrated) contacting the annular surface areas indicated generally at  40  and  42 . No particular type of bearing support is required, beyond one that leaves the axial space between the two inboard ends  32  and  34  unobstructed, for reasons described next. 
     Still referring to FIGS. 2 and 3, an indirect connection between the two wind up rollers  16  and  24  is established by a rotation transmission means, indicated generally at  44 . This comprises, in the embodiment disclosed, at least one (two here) annular bodies  46 , which freely rotate around central axis A. Conveniently, these can rotate on the end of one of the wind up roller shafts  28  or  30 , since these lie on axis A. Each annular body  46  has a pair of oppositely axially extending contact lugs  48  that are co radial to the drive lugs  36  and  38 , and substantially as narrow. Axial confinement of the two annular bodies  46  between the two inboard ends  32  and  34  serves to maintain all of the drive lugs  36 ,  38  and the contact lugs  48  in a condition of continual radial overlap, but with enough axial play to prevent rubbing. The outboard contact lugs  48  are capable of engaging the drive lugs  36  and  38 , while the inboard contact lugs  48  would contact only one another. The operation of rotation transmission means  44  is described next. 
     Referring next to FIG. 4, an arbitrary initial position is illustrated. In the FIG. 4 position, the two belts  12  and  20  are located with their apertures  14  and  22  aligned, that is, with no radial offset. In that relative location, the belts  12  and  20  would have the same net effect within any HVAC system, that is, they would pass the same flow of air. To provide multi zone discrimination, they have to be capable of being moved at least substantially independently of one another, to a relatively offset position, which the invention allows. In the FIG. 34 position, there is “slack” in the rotation transmission means  44 , that is, not all of the various lugs  36 ,  38  and  48  are in contact, and therefore not capable of transmitting rotation. A certain degree of relative turns, in either direction, between the inboard ends  32  and  34  (between the rollers  16  and  24 ) will be necessary to bring them all into mutual contact. Remembering that turning first roller  16  in either direction is the equivalent of moving first belt  12  up or down, the system could be set up with the slack “symmetrically split” in the FIG. 4 position, that is, arranged so that moving first belt  12  up or down by an equal offset relative to the second belt  20  would cause all of the lugs  36 ,  38  and  48  to contact in either direction. Or it could be set up so that all of the slack was already out of the system, and moving first belt  12  at all, in one direction of the other, would begin to move the second belt  20 . The slack could also be asymmetrically split, so that more relative motion in one direction or the other would be needed to remove the slack. A potential means for setting that “split” is described further below. 
     Referring next to FIG. 5, the first belt  12  has been moved downward relative to second belt  20 , by directly turning first wind up roller  16  with motor  26 . Just as a relative offset of Δ1 is reached between the two belts  12  and  20 , the rotation transmission means  44  becomes active, that is, all of the radially and axially overlapping lugs  36 ,  38  and  48  make mutual contact. Rotation is now transmitted to second wind up roller  24 . Second belt  20  now begins to move downward at the same rate, maintaining the same relative offset. 
     Referring next to FIG. 6, the first belt  12  has been rolled down farther, taking second belt  20  to a location shifted significantly down from its original location. The same Δ1 relative offset has been maintained, and the rotation transmission means  44  has remained active and maintained the turning connection between the two wind up rollers  16  and  24 . First belt  12  has been shifted down far enough that its apertures  14  might be out of position. However, the absolute and relative position of the two sets of apertures  14  and  22  might be correct under certain circumstances, as well, depending on what relative air flow rates were described. In any event, the relative position of the two belts  12  and  20  would be sensed by a conventional sensing and control system, and further belt motion, if any, would be initiated by the control system&#39;s operation of drive motor  26 . 
     Referring next to FIG. 7, it will be assumed for further illustration that in fact first belt  12  was “over turned” in the previous FIG. 6 position, and that it is desired to shift it back up, to at least some extent. The first belt  12  can be reversed and moved up, by turning first wind up roller  16  in the opposite direction (with the single motor  26 ), which will immediately cause the rotation transmission means  44  to again go “slack,” that is, to break the mutual contact between the lugs  36 ,  38  and  48 . First belt  12  will then roll up freely, without affecting second belt  20 , at least until the driving connection is re formed in the opposite direction. In FIG. 7, there is still slack in the system, and first belt  12  is still moving back up freely. It should be understood that some kind of tensioning and counterbalancing system would be incorporated in and between the second wind up roller  24  and second take up roller  27  to passively maintain second belt  20  in whatever position it is left in. 
     Referring next to FIG. 8, first belt  12  has shifted back up relative to second belt  20  far enough to reactivate the rotation transmission means  44 . First belt  12  has moved back slightly past its FIG. 4 starting position, pulling second belt  20  back up, but not as far as its FIG. 4 starting position. The relative belt offset in the upward direction is Δ2, less than Δ1, so the slack in the system is asymmetrically split, as described above. That split could be divided up in any desired fashion by providing a “setting” mechanism for the wind up roller inboard ends  32  and  34 , so that they and the drive lugs  36  and  38  could be turned and set to any relative starting position when the belts  12  and  20  were aligned. 
     Referring to FIGS. 4,  6  and  8 , it can be seen that there was not enough potential relative belt offset (Δ2) in the reverse direction to allow first belt  12  to be returned from its FIG. 6 “overturned” position to its FIG. 4 starting position, and yet still leave second belt  20  in its FIG. 6 shifted position. More slack in the rotation transmission means  44  in the return direction, more “Δ2”, would be required in order to do that. That could be arranged by dividing up the “slack” in the system to be biased more toward Δ2, as described above, or by providing more total potential relative belt offset (Δ1 plus Δ2) or some combination of the two. More total potential relative belt offset could be provided by increasing the number of annular bodies  46 , thereby creating more contact lugs  48  that would have to make contact, and providing for more “slack turns”. A designer would, in the first instance, decide what the total potential relative belt offset was needed in any given case. Knowing the belt offset length (Δ1 plus Δ2) and the radius of the wind up rollers  16  and  24 , one could calculate the number of relative slack turns necessary to provide that needed offset. This could be any integer number of relative turns, although probably three or fewer would be most practical. 
     Variations in the disclosed embodiment could be made. The single power means could conceivably be a mechanism other than a motor  26 , although that is most common. While it is important that the wind up rollers  16  and  24  be coaxial, the take up rollers  18  and  27  need not, although they typically would be. As already noted, more or fewer annular bodies  46  could be incorporated. The various lugs  36 ,  38  and  48  could have any shape that allowed them to make good contact without occupying excessive circumferential space. A wedge or “pie” shape, for example, could work well. The drive lugs  36  and  38  could be carried by any part of the wind up rollers  16  and  24 , but the separate ends  32  and  34  are convenient and provide the extra potential of being able to easily “set” the relative starting position of the drive lugs  36  and  38 .