Abstract:
In a first embodiment, a selective adjustment cord is provided as a very thin cord is extended through a series of thin engagement apertures which lie adjacent the main lift cord openings in a horizontal blind set. A series of engagement structures themselves cannot fit through the thin engagement apertures, and the selective adjustment cord is capable of movement of a louver having an engagement structure by only about the distance between adjacent louvers. In a second embodiment a slip fitting can be placed on specified louvers such that the first amount of upward travel of the lift cord will immediately lift the slats to which the slip fitting is engaged. Further movement of the lift cord will overcome the resistance of the slip fitting and allow the blinds to be lifted normally.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an improvement in window blinds which enables individuals to have more control over the admission of light and blind orientation with a greatly simplified control. 
   BACKGROUND OF THE INVENTION 
   Horizontal blind systems typically have an upper channel made of metal and configured to support movement and bearing components for horizontal blind operation. The two main operations are the elevation of the bottom horizontal which automatically collects the suspended horizontal step connectors above it and clears the window opening, and the angular movement of the slats utilized to allow light into the room at high or low angle or to close the louvers completely. 
   Where the louvers are left horizontal, very little direct light enters through the window unless the sun or exterior lighting is at low angles. Most louvered blinds are constructed so that the louvered width is sufficient for a small overlap to enable the louvers to be closed in either direction from horizontal to shut out the light. Even assuming no bare overlap, the louvers assume a position at horizontal such that the light source is typically lower than a 45° angle before light is admitted. Given a slight overlap, this angle is typically lower, at about 40° to about 43°. 
   In the summer, it is desired to open the louvers to a horizontal position to admit cooling breezes. However, this action also provides shade from high angle sun light, even if it is desired to admit the sunlight into the room. This action has the advantage in that the blocking of the breezes are minimized, but light can be admitted only by angling the louvers. 
   In angling the louvers to let in the sunlight (while still providing some privacy), the user must make the louvers track the angle of the sun. When the angle of the sun is tracked, the louvers are angled to enable sunlight to come in sufficiently, but only if the louvers are sufficiently tracking. The angling of the louvers significantly impedes the breeze and air flow into and out of the window opening. 
   What is needed is a system which will enable alternate ones of the louvers to move close to each other to provide wider gaps in a horizontal blind set. The movement should ideally be able to occur regardless of whether the slats or louvers are horizontal, or non tilted, as well as when the slats or louvers are tilted. The need to facilitate ease of movement is especially important when tilted as light may be admitted to the room while still providing a partial visual barrier to viewing the inside of the room from outside. 
   In one reference to Lai, U.S. Pat. No. 6,648,048, a complex arrangement is had using a series of adjacent ladders with each ladder having the number of 1/r where r is the number of ladder rungs. Each adjacent ladder can be raised independently with respect to the other ladders. Raising one adjacent ladder moves 1/r slats upward to the adjacent slat. Raising a second ladder moves another 1/r slats up forming an “r” sized bundle. 
   However, the expense of providing more than a single ladder is tremendous, particularly where that ladder has to be raisable, even over a slight vertical distance. The problems with multiple ladders involve the fact that each additional ladder can move only a limited amount. Most horizontal blind sets don&#39;t make accommodation for raising a ladder at all. A cord which is typically attached to the bottom louver collects all of the louvers where the blind set is to be raised. The ladder on a horizontal blind set is typically only for setting the louver angle. 
   In Lai, the raising of the second ladder involved lifting two sets of cords per side, regardless of whether or not the cords were joined along the way along the path to the user. Further, some mechanism had to be provided to prevent the user from continuing to lift the ladders which could cause the web strings joining the vertical ladder extents to tear or bind against the head rail. In addition to the complicated second ladder, Lai also uses bendable clips to engage the second ladder to enable the user to select which louvers to lift, which causes the areas near the ladders to become crowded into a mess. The device of Lai is complicated and causes extra wear and bunching and inhibits the ability for the user to lift the slat bundle to a height which would otherwise be available without the additional space occupied by the clips and additional ladders. 
   What is needed is a system which will enable differential lift of horizontal slats in a horizontal blind system to enable one or more slats to be grouped in order to continue to admit some light over a greater range of sun angles while the slats are horizontal, and to admit some breeze flow through while the slates are tilted. 
   SUMMARY OF THE INVENTION 
   In a first embodiment, an adjustment cord is provided as a very thin cord is extended through a series of thin engagement apertures which lie adjacent the main lift cord openings in a horizontal blind set. A series of engagement structures are provided on the thin cord which acts as an adjustment cord which is capable of movement of only about the distance between adjacent louvers. In the first embodiment, the engagement structures themselves cannot fit through the thin engagement apertures such that upward movement of the adjustment cord will cause every other (for example) louver or slat to be engaged and lifted upward to a position close to the adjacent slat. In a variation on this embodiment, it may be provided that structures can be provided on the adjustment cord which can have a small clip added or removed by the user to provide the interference which provides the lift. 
   In a second embodiment, a special lift cord is eliminated in favor of a slip fitting which can be placed on every other (for example) louver or slat in which the first amount of upward travel of the lift cord will immediately lift the slats to which it is connected. Thus the first short length of lift will cause every other (for example) louver or slat having the fitting to lift its associated louver or slat upward until contact is had with the louver or slat above it. Further movement of the lift cord will overcome the resistance of the slip fitting and allow the blinds to be lifted as per usual. Each slip fitting has only enough friction resistance equivalent to the weight of its portion of the louver or slat to be lifted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a slightly downwardly looking perspective view of a blind set showing a horizontal break line to illustrate that it can be of any overall length and looking down at the head rail and showing two sets of cords, one set operating the louvers for complete lift and the other set of cords extending through a separate hole next to the lift cord and used for manipulating some louvers across a small range of motion from a rest position to a position underneath the next most upper adjacent louver; 
       FIG. 2  is a plan view of a series of about four louvers showing the existence of the lift cord and a series of lead crimps which only underlie every other louver, and where only one side is actuated to emphasize the possibility of one-sided actuation and to show that the sides need not be actuated simultaneously; 
       FIG. 3  is a small figure showing details of an interference members which may be a knot, crimp or other vertical distance supporting structure; 
       FIG. 4  is a view of the bottom of the head rail showing that the main lift cord and alternate lift cord can occupy closely adjacent wear structures; 
       FIG. 5  is a top view of the head rail seen in  FIG. 4  and illustrating the tilt drums and the path of the cord sets seen in  FIGS. 1 and 2 ; 
       FIG. 6  is a perspective view illustrating the use of a slip fitting mounted on a louver which can provide slight friction based force for lifting a louver having the slip fitting when the lift cord is moved over a vertical distance less than the louver spacing; 
       FIG. 7  is an expanded and isolated top view of the slip fitting seen in  FIG. 6 ; 
       FIG. 8  is a still further expanded end side view of the slip fitting seen in  FIGS. 6 and 7 ; and 
       FIG. 9  is a lateral side view of the slip fitting seen in  FIGS. 6-8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The description and operation of the shutter system of the invention will begun to be best described with reference to  FIG. 1  which illustrates a first embodiment of a selective lift blind set  21 . Selective lift blind set  21  includes a head rail  23  supporting a left ladder cord set  25  and a right ladder cord set  27 . As is usual for horizontal blind sets, each ladder cord set  25 ,  27  has a front and a rear vertical cord and a series of horizontal cords joined between the front and rear vertical cord to form a cradle for a series of slats, or louvers  29  seen in  FIG. 1 . The lowermost louver is seen as a base louver  31  which is typically thicker and much heavier than the other louvers. Base louver  31  must have sufficient weight to pull the main lift cord through the components of the head rail  21  so that gravity can operate to enable lowering of the louvers  29  of the selective lift blind set  21 . 
   To the right side of the head rail  21  are a pair of locks including a lock  33  and a lock  35 . From the lock  33  and through its opening extend a first selective lift cord  37  and a second selective lift cord  39 . From lock  35 , a looping cord is seen as a lift cord  41 . The lift cord  41  is typically the lift cord which has one end attached to one end of the base louver  31  and the other end attached to the end of the base louver  31 . The lift cord  41  is typically knotted or attached with a fitting which sets the lift cord  41  together so that one pull on the looping cord  41  will lift the base louver evenly. 
   In accord with the design approach of the invention, first selective lift cord  37  and second selective lift cord  39  extend through the lock fitting  33 , through the head rail  23  and down through a special fitting (not shown in  FIG. 1 ) and emerge as seen on the left side as a continuation of selective lift cord  37  and on the right as selective lift cord  39 . The selective lift cords  37  and  39  can be seen as having a series of interference members  45  which are shown in a position not directly underneath the louvers  29  only for the purposes of illustration. 
   It is understood that the term interference members  45  includes any structures which are capable of physically marking or providing a physical attribute at a place along a cord, in this case first and second selective lift cords  37  and  39 . In the embodiment shown, the interference members  45  may be small pieces of metal pressed around the first and second selective lift cords  37  and  39  at specified distances. The manner in which spacing is obtained may vary widely. A cord may be marked to facilitate manual adding of the interference members  45  along its length. The complete selective lift blind set  21  may be laid out with the existing assembly seen in  FIG. 1  used to apply the interference members  45  at the time that the selective lift blind set  21  is checked for quality control. 
   In the position shown, each of the interference members  45  would be resting directly underneath and adjacent every other louver  29  and would not be able to be seen from the angle of  FIG. 1 . The dropped position of the interference members are for illustration only and merely indicate that the interference members  45  will ideally occur adjacent every other louver  29  in order to lift every other louver  29  upwardly against the louver  29  next most upwardly adjacent. Note also that the selective lift cords  37  and  39  do not extend all the way down to the base louver  31 . 
   The operation of the selective lift blind set  21  will possibly be as follows. Once the lift cord  41  is allowed to travel back through the head rail  23  to enable the louvers to take the position generally shown in  FIG. 1 . Pulling both of the selective lift cords  37  and  39  will raise every other louver  29  to move the louvers  29  to a position where they are grouped in pairs. As a result the spacing between the collected louver pairs will be doubled. 
   Because the selective lift cords  37  and  39  lift from the center of each louver, the louvers can be freely tilted from one side to the other. Although many horizontal blind sets may include both cord and wand tilt controls, the selective lift blind set  21  seen in  FIG. 1  shows a wand type tilt control, including a tilt fitting  51  to which is attached a wand  53  to facilitate axial turning of the tilt fitting  51 . This is typically accomplished by rotating an internal drum to cause the left and right ladder cord sets  25  and  27  to move up and down oppositely. As a front vertical cord of the left and right ladder cord sets  25  and  27  moves up, a rear vertical cord of the left and right ladder cord sets  25  and  27  moves down. 
   This illustrates a significant advantage over the use of a bulky additional ladder cord to provide the selective lift. Since the lift provided by the method and structure of the present invention occurs at the tilt center of the louvers, they are even more freely tiltable by the conventional ladder cords, and makes the ladder cords work more easily. Each formed double set of louvers in full double set orientation is at least partially supported by the interference members  45 . 
   Further, when the first and second selective lift cords  37  and  39  are actuated partially the louvers partially supported by the interference members  45  will be lifted away from dependence on the left and right ladder cord sets  25  and  27  and will not tend to pivot as much or perhaps even at all, as the other louvers  29  which are directly supported by the left and right ladder cord sets  25  and  27 . This would tend to ensure a greater clearance with some visual effects. 
   When the first and second selective lift cords  37  and  39  are actuated fully, the louvers supported by the interference members  45  will assume an orientation in accord with the position of the louvers on the top of each collected pair. At that point the spacing between the louvers  29  will be double the usual spacing, and sunlight occurring at a steeper angle will be admitted. 
   Referring to  FIG. 2 , a plan view of the mechanics of the selective lift blind set  21  illustrates partial actuation of only one side of the selective lift blind set  21  namely first selective lift cord  37  while second selective lift cord  39  remains unactuated. 
   At the left side, the first selective lift cord  37  has been pulled down, causing the left sides of the louvers  29  which lie directly over interference members  45  to be raised up. Of course, the pulling of the first selective lift cord  37  alone typically will not be used to bring pairs of louvers  29  together as a moment is created when the ends of adjacent louvers first meet. This is shown in  FIG. 2 .  FIG. 2  does show the interference members  45  directly under the louver  29  being lifted on the left. 
   On the right, it can be seen that the louvers  29  being lifted may have been lifted partially upwardly and away from the interference members  45 . The first selective lift cord  37  operates in conjunction with the second selective lift cord  39  as they should be lifted simultaneously to effect the even lifting of the louvers  29  overlying the interference members  45  in a manner which will not cause touching of the ends as seen in  FIG. 2 . However, the ability to actuate one of the first selective lift cord  37  or second selective lift cord  39  independently gives some additional visual variation as is seen in  FIG. 2 . Thus a gradient is established with the louvers  29  having a separation on the left side as if they were fully paired, while the louvers are more evenly spaced toward the right side of the selective lift blind set  21 . 
   Other alternatives can include a resting position where each lifted louver is moved half way toward the next upper louver, creating a visual impression of un-evenness. The use of the lock  33  enables almost any combination to be achieved and held. Further, the lifting of the louvers  29  does not interfere with the actuation of the tilt fitting  51  and wand  53 . Any angle can be achieved by the louvers regardless of angle. 
   All of the orientations seen in  FIGS. 1 and 2  were variations on non-tilted louver  29  positions. Where the louvers  29  are tilted, either forward or rearward, the visual combinations are greatly enhanced. The complete pairing of the louvers will be somewhat offset when tilted, perhaps a one quarter inch overlap or the like. In the tilted position, the partial upward movement of the louvers  29  overlying the interference members  45  can create a dramatic effect. Further, where the louvers  29  have different colors or patterns, the manipulation of the first and second selective lift cords  37  and  39 , in combination with the tilt fitting  51  can make dramatic effects. 
   Referring to  FIG. 3 , a closeup view isolated on the left side of one of the louvers  29  seen in  FIG. 1  illustrates the relationship of the left ladder cord set  25 , lift cord  41  and first selective lift cord  37 . The left ladder cord set  25  is seen as having a first vertical cord  61 , second vertical cord  63  and which are connected at various levels by horizontal step connectors  65 . In the view shown, and for illustration purposes only, the louver  29  is lifted slightly from its resting position in which it would lie atop the horizontal step connector  65  beneath it, as well as upon the interference member  45 . If the louver  29  were left in a resting position, it would obscure the view of these two supporting structures. 
   The louver  29  is shown as having a wide oval slot  71  through which the lift cord  41  passes. The length of the oval allows the lift cord  41  to work and freely pass through the louvers  29  regardless of the angular tilt orientation of the louvers  29 .  FIG. 3  also illustrates that in a resting position, the horizontal step connector  65  is on an even level with the interference member  45  just before actuation and while in the rest position. 
   In one embodiment, the interference member  45  is a crimped member. A crimped member may have an expanded portion to form an interference with respect to an aperture  73  which is seen extending vertically through the louver  29  and is just adjacent the wide oval slot  71 . The location of the aperture  73  adjacent the wide oval slot  71  is a matter of design choice. Aperture  73  can exist to the other side of wide oval slot  71 , and the left ladder cord set  25  can extend to either side of the lift cord  41 , and to either side of the first selective lift cord  37 . 
   Referring to  FIG. 4 , a view of the underside of the head rail  23  illustrates some of the organizational structure on the underside. A pair of ladder cord set slots  81  enable the left and right ladder cord sets  25  and  27  to pass through. The reasons for the relatively wide slot is to accommodate left and right ladder cord sets  25  and  27  which may be wider, and which may be tape sets instead of cord sets. 
   A pair of smooth slip fittings  83  has an aperture and accommodates the lift cords  41 . A pair of smooth slip fittings  85  are typically made of a low friction material such as nylon and, along with other low friction fittings within the head rail  23 , acts to make operation of the first selective lift cord  37 , second selective lift cord  39  as frictionless as possible. Again, the orientation of the clip fittings  83  and  85  is a matter of design choice and they could assume any orientation, but the best orientation is preferably directly vertically over the position they will assume in the louvers  29 . 
   Referring to  FIG. 5  an upper view of the head rail  23  is illustrated and shows some further details of the routing of the first selective lift cord  37 , second selective lift cord  39  and lift cord  41 . A set of tilt actuator drums  91  are provided for attachment to the first vertical cord  61  and second vertical cord  63  of the left and right ladder cord sets  25  and  27 . 
   Another way to provide horizontal lift pairing of the louvers  29  can take advantage of the fact that during the raising of the blinds where all louvers  29  are collected that the lift cord passes freely through the wide oval slot  71  in each louver  29 . Only when the louvers are collected by being stacked upon the base louver  31 , will each louver move up. In conventional blind sets, the wide oval slot  71  is so wide that all of the louvers in a conventional blind set will depend solely on either the base louver  31  during raising, or upon the left and right ladder cord sets  25  and  27 . The differential lift given some of the louvers as was seen in  FIGS. 1 and 2  involve movement against only the weight of the louvers, and only over a short distance. 
   If a louver had a limited dependence from the lift cords  41 , it lift within the space of its left and right ladder cord sets  25  and  27  initially to form a pair, and then become later collected as a pair based upon further movement of the lift cords  41 . The further simplification of the raising of some louvers based upon the lift cords  41  alone could be accomplished with a slip fitting which can be added to the wide oval slot  71 . The slip fitting can be of any type. A slip fitting should give only enough resistance to movement of the lift cords  41  which is equivalent to that necessary to overcome the weight of half of the louver  29  to which it is attached, to permit it to be raised from its resting position against its lower horizontal step connector  65  and to raise it up to a position adjacent to the horizontal step connectors  65  of the next higher louver  29 . 
   Referring to  FIG. 6 , a view of an insertable slip fitting  101  is shown in place with respect to a wide oval slot  71  seen in a louver  29 . The details of the insertable slip fitting  101  can be widely varying, but the insertable slip fitting  101  should be able to be inserted on an assembled blind set with an existing lift cord  41  in place without having to dis-assemble the blind set or severing or disconnecting the cord  41 . 
   In terms of geometry, the design should enable being opened and slipped around the lift cord  41  and then brought to a position in place with respect to the wide oval slot  71 . The insertable slip fitting  101  should have an even width for accommodating the lift cord  41 . It is most highly desirable that the insertable slip fitting  101  have a structural orientation that will not bind the wide oval slot  71  or cause a changed force or surface presented to the lift cord  41  when it is in place. Due consideration must be given to the relative friction between the materials employed for the lift cord  41  and insertable slip fitting  101 . Depending upon overall wear, friction and other geometry requirements, the slip fitting  101  can be made of plastic, polyurethane, nylon, fiber glass, metal, glass, carbon composite, polypropylene, Teflon or a Teflon or other material coating of any of the aforementioned materials. 
   It is preferable that the insertable slip fitting  101  be secured to the louver  29  without lateral pressure. One method could involve an independent snap fitting or the like. Referring to  FIG. 7 , details of one embodiment of the slip fitting  101  includes an upper flange  103  which overlies a main vertical extending portion  105  shown in dashed line format. The insertable slip fitting  101  has an slot opening  107  which has a beveled entrance over part of its depth. The slot opening  107  leads into a matching oval (or round) main opening  109 . The main opening  109  accommodates the lift cord  41 . 
   The lift cord is shown as being slightly bigger than the inside surface of the lift cords  41  inside surface of the slip fitting  101  as it is expected that, depending upon the material and density of lift cord  41 , that lift cord  41  will be somewhat compressed to obtain the correct resistance. The setting of the lateral clearance for the lift cord  41  within the insertable slip fitting  101  will depend upon a number of factors, including the materials used and the relative friction between them. 
   However, to begin with, an idealized frictional resistance should be computed. This is the amount of the vertical lifting force from all of the lift cords  41 , against the insertable slip fittings  101  present on the blind set  21 . This amount of force should be only infinitesimally greater than the weight of the louver  29  to be lifted (including the weights if any of the insertable slip fitting  101 , and other components supported by the louver  29  to be lifted). Where a louver  29  is to be lifted from both ends with two insertable slip fitting  101 , the force will be halved. An extra amount should be added to account for wear on the insertable slip fitting  101  from sliding use for a long period of time. 
   Only the act of using the lift cord to repeatedly and completely lift the blind set and louvers will cause any significant wear on the insertable slip fitting  101 . Further, the insertable slip fitting  101  at the top of the louver set will experience the most wear for each lifting and lowering of the louvers  29  of the blind set  21 . 
   On letting the louvers  29  of the blind set  21  down, the maximum pulling resistance experienced by the base louver  31  will occur as the lowermost louver  29  having an insertable slip fitting  101  attached rests into place on its left and right ladder cord sets  25  and  27 . As the base louver then moves its last few inches away from the lowermost louver  29  having an insertable slip fitting  101  attached, the resistance against further movement of each of the lift cords  41  moving through all of its insertable slip fittings  101  will be at its maximum. Thus the weight of the base louver should be sufficient to overcome this resistance, which will be at least as high as the sum of all of the louvers  29  having an insertable slip fitting  101  attached. 
   To account for wear and any diminution in holding force due to repeated lowering and raising of the blind set  21 , the insertable slip fittings  101  will have an initial resistance which is somewhat higher than the minimum necessary to overcome the weight of the louver and raise it. Once both the minimum value of resistance is known, and then once a factor of resistance is added in to combat wear over time, the selection of materials and dimensions is made to achieve the desired values. 
   The density, compressibility and wear characteristics of the lift cords  41  must be taken to account in selecting the materials of the insertable slip fitting  101 , the surface area exposed to the left cords  41  and the width of the main opening  109 , to name only some of the considerations which are materials based. A thicker louver gives the opportunity for a vertically extended length and greater vertical contribution to surface area for the main opening  109 . Greater surface area means less wear and the ability to more widely distribute the wear over a greater surface area. Other factors include the shape of the inside surfaces of the main opening  109  and more. 
   Referring to  FIG. 8 , an end view looking into the end of the slot opening  107  reveals two small hook extensions  111  on the end adjacent the slot opening  107 , and a snap projection  113  on the end opposite the slot opening  107 . The two small hook extensions  111  are shown as having small projections toward the viewer while snap projection  113  has some projection away from the viewer and cannot be seen in  FIG. 8 . 
   Referring to  FIG. 9 , an expanded side view, rotated 90° from the view seen in  FIG. 8  illustrates further details of the two small hook extensions  111  and snap projection  113 . The snap projection  113  can be seen to have a dimple  115  or other projection to enable the slip fitting  101  to be inserted into the wide oval slot  71 , either by a user or at the factory. 
   A typical installation will have the installer or user approach the louver  29  in much the same condition as it might be seen in  FIG. 3  (probably excluding the first selective lift cord  37 ). The user than presses the end of the slip fitting  101  having the slot opening  107  toward the lift cord  41  with the flange  105  in the upward position, oriented away from the top surface of the louver  29  into which it is to be attached. If necessary, depending upon the relative sizes of the slip fitting  101  and lift cord  41  the user can manually assist the widening of the slot opening  107  to admit the lift cord  41 . 
   Once the lift cord is admitted, the sides of the slip fitting  101  should snap shut to yield the configuration seen in  FIG. 7 . The user is then free to reorient the slip fitting  101  to a position where it will align with the wide oval slot  71 . The user then directs the bottom end of the slip fitting  101  having the two small hook extensions  111  into and toward one end of the wide oval slot  71  so that the two small hook extensions  111  extend though the wide oval slot with pressure. Then, the user brings snap projection down and with snap resistance, through the other end of the wide oval slot  71  to cause the slip fitting  101  to securely snap into place with respect to the wide oval slot  71 , to secure it with respect to the louver  29 . 
   In the case of a home installation, the user attaches the slip fitting  101  only to the louvers desired to move to an upper position on the initial pull of the lift cord  41 . Since pulling of the lift cord  41  will tend to raise the base louver  31  by an inch or two, an added length for the base louver  31  can be utilized, or in the alternative some arrangement to pull the lift cords down by 2 or so inches to make sure that the bottom most louvers  29  fitted with the slip fitting  101  (in the case where the louver just above the base louver is fitted) is all seated before lift is applied. Where the bottom louver  29  which is not the base louver is not fitted with the slip fitting  101 , there should be enough downward movement of the lift cord in releasing the last louver  29  into its left and right ladder cord sets  25  and  27  to insure that all louvers fitted with the slip fitting  101  are properly seated. 
   While the present invention has been described in terms of a system and method for enabling creative manipulation of some louvers in a horizontal blind set, one skilled in the art will realize that the structure and techniques of the present invention can be applied to many structures, including any structure or technique where a shortened control movement is desired within a much larger control space. 
   Although the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention. Therefore, included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.