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You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. provisional patent application 60/429,806, filed Nov. 27, 2002. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a slideable panel assembly, and more particularly relates to apparatus for controlling the operation of a slideable panel. 
     BACKGROUND OF THE INVENTION 
     Many vehicles employ a panel assembly having a moveable panel which is utilized to control access to an opening in the vehicle. One example of such an application is on the sliding back-windows currently available on many pick-up trucks. Unfortunately, current designs only allow latching of the moveable panel in its fully closed position. The moving panel is a free-motion state in all other positions. One drawback of this design is that the panel assembly represents a possible point of entry for theft when the moveable panel is not in its fully closed position. Accordingly, there exists a need to provide a panel assembly which provides better control over the movement of the moveable panel and a panel assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a panel assembly for a motor vehicle that provides the ability to securely control the size of an opening defined by the panel assembly. The panel assembly thus provides a theft deterrent by making it more difficult to get through a partially open window. Generally, the panel assembly comprises a fixed panel defining an opening, and a moveable panel for selectively covering the opening. A rail is attached to the fixed panel, and generally comprises a three-sided channel which slideably receives the moveable panel. The three sided channel has an attachment side attached to the fixed panel and an engagement side facing outwardly from the fixed panel. A handle is attached to the moveable panel and is spaced therefrom to define a recess sized to receive the engagement side of the rail. A cam is moveably mounted to the handle and defines an engagement surface which extends through a slot defined in the handle. The cam is biased against the engagement side and is operable between a locked position and an unlocked position. In the locked position, the engagement surface engages the engagement side, and the unlocked position the engagement surface is positioned away from the engagement side. 
     According to more detailed aspects, the handle and cam are capable of being operated with one hand and thus define a single hand actuator. The cam may be pivotally mounted to the handle, or alternatively may be axially slideable relative to the handle. When pivotally mounted, the proximal end of the cam is pivotally mounted while the distal end preferably defines the engagement surface. The distal end may be curved and extend outwardly away from the rail to facilitate operation of the cam. Alternatively, the proximal end of the cam may define the engagement surface, wherein the proximal end is eccentrically shaped to engage and disengage the rail upon rotation of the cam. The opposing sides of the handle preferably include flanges extending away from the rail a distance greater than the distance the handle projects away from the rail in the locked position, thereby preventing inadvertent actuation of the cam. 
     The engagement surface may be a planar surface, or alternately may include a plurality of gripping teeth or other engagement features. The cam may include a pin projecting towards the rail to define the engagement surface. With a pin, the engagement side of the rail defines a plurality of apertures sized to receive the pin for locking the moveable panel at a plurality of discrete positions. Accordingly, the assembly of the present invention allows securing the moveable panel at either an infinite number of latching locations or a discrete number of predetermined locations along the sliding path of the rail. 
     When the cam is axially adjustable in a direction normal to the rail, the cam is preferably biased towards the rail. Alternatively, the cam may be biased away from the rail and a latch is provided which fixes the cam in the locked position. The cam may thus be a push button sized to be operated with a single finger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a plan view of an embodiment of the panel assembly constructed in accordance with the teachings of the present invention; 
         FIG. 2  is an enlarged perspective view, partially cut away, of the panel assembly depicted in  FIG. 1 ; 
         FIG. 3  is plan view of the handle forming a portion of the panel assembly depicted in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the handle taken about line  4 — 4  in  FIG. 2 ; 
         FIG. 5  is a perspective view similar to  FIG. 2  but depicting an alternate embodiment of the handle; and 
         FIG. 6  is a cross-sectional view taken about the line  6 — 6  of  FIG. 5 . 
         FIG. 7  is a plane view of the cam depicted in  FIGS. 1–4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the figures,  FIG. 1  depicts a panel assembly  10  constructed in accordance with the present invention. The panel assembly  10  generally includes a fixed panel  12  which defines an opening  14 . The fixed panel  12  may comprise an relatively rigid material, and preferably comprises a transparent material such as glass. The panel assembly  10  is preferably located in the passenger compartment of a vehicle, such as a passenger truck (not shown). The opening  14  thus provides access to the interior/exterior of the passenger compartment. 
     A pair of rails  16 ,  18  are attached to the fixed panel  12  and serve as a guide for moveable panel  20 . The upper and lower ends  21 ,  23  of the moveable panel  20  are retained within the rails  16 ,  18  and allow the panel  20  to slide axially between a closed position (shown in  FIG. 1 ) substantially covering or aligning with the opening  14 , and an open position wherein at least a portion of the opening  14  is exposed. A handle  22  is connected to the moveable panel  20  which includes a cam  30  for allowing a user to slide the moveable panel  20  to a infinite or discrete number of locations along the slide path and latching the panel  20  in that position. 
     Turning now to  FIG. 2 , an enlarged view of the panel assembly  10 , partially cut away, has been depicted. The handle  22  of the assembly  10  has been shown in greater detail, and generally includes a planar body  24  attached to the moveable panel  20 . The body  24  includes a left side edge  26  and a right side edge  28  which each define a flange  56 ,  58  projecting transversely from the rail  16 . The handle  22  includes a cam  30 , to be discussed in more detail herein, which is utilized to fix the position of the handle  22  relative to the rail  16 , and hence fix the position of panel  20 . Notably, the left and right flanges  56 ,  58  project away from the rail  16  a distance greater than the cam  30  projects away from the rail  16  (in its locked position). In this way, the flanges  26 ,  28  prevent unwanted actuation of the cam  30  by shielding it from the sides. 
     The main body  24  of the handle  22  also includes a boss  25  which supports the cam  30 . The body  24  defines a slot  36  which is sized to receive the cam  30 . The cam  30  extends through the slot  36  and engages the rails  16 , as will be described below. The cam  30  generally includes a first proximal end  32  that is pivotably attached to the handle  22 , and more particularly the boss  25  formed on the body  24 . The opposing distal end  34  of the cam  30  is arcuate in shape and curves to project outwardly from the rail  16  to define a gripping portion  35  that facilitates operation of the cam  30  The handle  22  and cam  30  are sized and positioned to define a single hand actuator that is capable of being operated with one hand. 
     The pivotal connection of the cam  30  to the handle  22  is best seen in the plan view of  FIG. 3 , which shows the cam  30  partially cut away. The boss  25  has a pin  29  set therein. A torsion spring  27  is fitted around at least a portion of the outer periphery of the pin  29  and engages the cam  30 . The cam  30  includes a recess  31  which receives the pin  29 . The torsion spring  27  resists the relative rotation of the cam  30  and handle  22  (and hence also relative to the pin  29  when fixed to the boss  25 ) to bias the cam  30  towards the rail  16  (i.e. in a direction into the page in  FIG. 3 ). 
     It can therefore be seen that the cam  30  is pivotably mounted to the handle  22  and has a distal end  34  which is spring biased into the rail  16 , as can best be seen in the cross-sectional view of  FIG. 4 . The rail  16  generally comprises a three sided channel having an attachment side  40  opposite an engagement side  42  which are connected by a linking side  44 . The attachment side  40  is connected to the fixed panel  12 . The rail  16  defines a recess  17  for receiving the moveable panel  20 . 
     The moveable panel  20  is attached to the handle  22  by way of a spacer  46  to thereby define a recess  48  between the moveable panel  20  and the body  24  of handle  22 . The recess  48  receives the engagement side  42  of the rail  16 . As previously discussed, the handle  22  includes slot  36  which allows the cam  30  to extend therethrough and engage the rail  16 . More specifically, the cam  30  and its distal end  34  define an engagement surface  38  which is biased into and presses against the engagement side  42  of rail  16 . 
     The friction between the cam  30  and the rail  16  is sufficient to prevent movement of the moveable panel  20  by a person either inside or outside the vehicle. Alternatively, engagement surfaces may be employed such as teeth or tongues which cooperate with corresponding grooves, or simply gripping teeth ( 39 ,  FIG. 7 ) formed on the engagement surface  38  of the cam  30  for creating a strong frictional bond with the rail  16 . In this way, the moveable panel  20  and handle  22  may be latched to the fixed panel  12  via rail  16  at an infinite number of locations. 
     Accordingly, the cam  30  is operable between a locked position and an unlocked position. In the locked position, the cam  30 , and more particularly its free end  34  are spring biased such that an engagement surface  38  engages the rail  16  for latching the moveable panel  20  at a desired location. In the unlocked position, the engagement surface  38  is positioned away from the rail  16 , thereby allowing sliding movement of the moveable panel  20 . The cam  30  is spring biased into the rail  16  so that the cam  30  is normally in its locked position. 
     An alternate embodiment of the panel assembly  10 ′ has been depicted in  FIGS. 5 and 6 . The structure and operation of the panel assembly  10 ′ is similar to that of the embodiment shown in  FIGS. 2 and 4 , but utilizes an alternative engagement surface  38 ′ for engaging the rail  16 ′. Accordingly, like reference numerals have been utilized with like components of the embodiments. 
     More specifically, the cam  30 ′ includes a distal end  34 ′ having a projection or pin  50  projecting towards the rail  16 ′. The rail  16 ′ includes an engagement side  42 ′ having a plurality of apertures  52  formed therein. The apertures  52  are sized and positioned to receive the pin  50 , which now defines the engagement surface  38 ′. The apertures  52  are spaced axially along the rail  16 ′ such that the moveable panel  20  may be latched at discrete locations along the rail  16 ′ by way of its handle  22  and cam  30 ′. The pin  50  extends into an aperture  52  and the outer periphery thereof defines the engagement surface  38 ′ which engages the inner periphery of the aperture  52  in the locked position. 
     In another embodiment, and with reference to  FIG. 2 , the cam  30  may include a pivotally proximal end  32  which is eccentrically shaped such that in the locked position, the proximal end  32  engages the rail  16 . As shown in the figure, the cam  30  would define a cam axis extending parallel to the rail  16 . When the cam  30  is rotated such that its axis is non-parallel with the rail  16 , the eccentric proximal end  32  would disengage the rail  16  allowing movement of the moveable panel  20 . The distal end  34  would be used to operate the cam  30  between locked and unlocked positions. 
     In yet another embodiment, the cam  30  may be axially adjustable in a direction normal to the rail  16 . In this embodiment, the cam  30  would be biased towards the rail preferably by a spring. Alternatively, the cam could be biased away from the rail  16 , and a latch would fix the cam  30  in a locked position having the engagement surface  38  pressed against the engagement side  42  of the rail  16 . The latch could thus be sized as a button to be pressed by a user with a single finger. Such push button, spring-loaded latches are well known in the art. 
     The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Summary:
A panel assembly for a motor vehicle provides the ability to securely control the size of an opening defined by the panel assembly. The panel assembly thus provides a theft deterrent by making it more difficult to get through a partially open window. The panel assembly comprises a fixed panel defining an opening, and a moveable panel for selectively covering the opening. A handle is attached to the moveable panel and includes a cam that is moveably mounted to the handle and extends through a slot defined in the handle. The cam is biased against the rail and is operable between a locked position and an unlocked position.