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FIELD OF THE INVENTION 
     The present invention relates to louver assemblies and, more particularly, to a slat tensioning mechanism for releasably holding slats at a desired angulated position in a frame opening and also to frame-structure improvements. 
     BACKGROUND OF THE INVENTION 
     Louver assemblies have been known to be used in conjunction with windows and doors. Louver assemblies generally consist of a plurality of slats pivotally mounted at opposed ends to vertical uprights of a frame. Louver assemblies are advantageous in preventing the light and, in some instances, rain or snow to pass therethrough, while allowing air circulation when the slats are open. The louver assemblies of interest have solid slats as opposed to blinds with cloth slats used mainly in conjunction with windows as an alternative to curtains. Louver assemblies with solid slats are usually mounted in a rigid framing. These louver assemblies have also been known to include mechanisms whereby the slats are interconnected in order for each of them to be pivotally set at a same determined position. In this way, the slats of the louver assembly may rotate from a closed position, wherein the slats are generally vertical, to a maximum opening position, wherein the slats are horizontal. 
     U.S. Pat. No. 4,643,081, issued on Feb. 17, 1987 to Vicinanza et al., discloses a louver system in which the slats are interconnected to pivot together such that they can all be set at a same determined position as described above. The interconnecting mechanism is enclosed within hollow body uprights, whereby it is hidden. 
     Systems have been provided to hold the slats when a desired positioning is achieved. For instance, U.S. Pat. No. 465,098, issued on Dec. 15, 1891 to Maule, discloses a window or door blind wherein slats are interconnected to pivot in concert. A knob is secured to the slat interconnection, whereby it translates up and down an upright of the window or door blind in response to a rotation of the slats. The knob is tapped and is operatingly engaged to a hidden threaded rod, such that the knob can be screwed downward to apply a pressure on the upright. Consequently, the slats can be locked in a desired position. U.S. Pat. No. 3,991,518, issued to Ishihara on Nov. 16, 1976 also discloses a similar locking system, with the difference being that the system is located at a bottom of the louver assembly and is fully visible. 
     Efforts have been made, as seen in the prior art, to enclose the slat interlocking systems in the uprights. This feature enhances the decorative appeal thereof. On the other hand, in the prior art, the slat locking mechanisms are not fully enclosed in the uprights and are not esthetically attractive. It would be desirable to hide the slat locking mechanism. 
     Also, the previously disclosed slat locking mechanisms each require a manual step for the locking of the slats in a desired position. As a result, if the slat opening needs to be changed a few times during the day due to climatic changes, a precious amount of time is lost by this unnecessary manual step. 
     Louvered frames of the prior art, whether they are hinged or releasably mounted to a window sill, are usually maintained in position in their window sill by attaching devices mounted to adjacent frame uprights and accessible interiorly of the frame. These attaching devices often break and are an eye sore. 
     It is also desirable to provide an effective and reliable traction assembly which is easy to install in the mating ends of the frame members and easy to adjust after the frame members are interconnected. 
     SUMMARY OF THE INVENTION 
     It is a feature of the present invention to provide a slat tensioning mechanism for releasably holding slats at a desired angulated position in a frame and which overcomes the above described disadvantages of the prior art. 
     It is a further feature of the present invention to provide an upright cap comprising snap-engagement means for maintaining a louver assembly in position in a window sill. 
     It is still a further feature of the present invention to provide a traction corner for facilitating the assembly of frame members of a louver assembly. 
     According to the above features of the present invention, from a broad aspect, the present invention provides a slat tensioning mechanism for holding interconnected slats of a louver assembly in a desired angulated position. The slat tensioning mechanism comprises a housing having wheel positioning means for rotationally receiving a bearing wheel. the bearing wheel has an outer circumferential flat wall, and hub means adapted for securement to an end connector of a slat, whereby the bearing wheel and the slat rotate together. A tensioning arm assembly is pivotedly engaged to the housing and has an arm disposed at a predetermined location with respect to the outer Circumferential flat wall of the bearing wheel. The arm has a friction surface at a free end thereof for applying a pressure on the outer circumferential flat wall of the bearing wheel for frictionally arresting the bearing wheel at the desired position. The slat tensioning mechanism is adapted to be disposed in an upright of the louver assembly. 
     According to a further broad aspect of the present invention, there is provided a cap adapted for covering an end portion of an upright of a louver assembly. The cap comprises a top surface and a bottom surface, and connection means for releasably securing the cap to the end portion of the upright. A button protrudes from the top surface and is adapted for snap-engagement with a corresponding groove of a window sill, whereby the louver assembly is releasably engagable to the window sill. 
     According to a still further broad aspect of the present invention, there is provided a traction corner for releasably assembling a pair of hollow members having corresponding obliquely cut faces. The traction corner comprises a right-angle body having a pair of arms. One of the arms is adapted to be inserted in one of the hollow members, the other of the arms is adapted to be inserted in the other of the hollow members. A connecting clip is disposed in the right-angle body having a pair of wings. Each of the wings has a hook portion at a free end thereof. The hook portions are adapted for captively engaging the wings in the hollow members, whereby the corresponding obliquely cut faces are face-to-face with a gap therebetween. An expansion mechanism is provided for exerting pressure against the junction of the pair of wings and against the right-angle body such that, with the wings being held captive in the hollow members, the free ends of the wings are displaced toward each other for joining the obliquely cut faces in co-planar engagement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the present invention will now be described with reference to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a louver assembly comprising a slat positioning system in accordance with the present invention; 
     FIG. 2 is a perspective view, partly fragmented, of a slat tensioning device and an upright cap in accordance with the present invention; 
     FIG. 3 is a side elevational view, partly fragmented, of the slat tensioning device and the upright cap; 
     FIG. 4 is a perspective view of the slat tensioning device; 
     FIG. 5 is a perspective view of a wheel of the slat tensioning device; 
     FIG. 6 is a perspective view, partly fragmented, of the upright cap releasably engaged on the framing of a window sill; 
     FIG. 7 is a schematic cross-sectional view of the upright cap releasably engaged in the window sill; 
     FIG. 8 is a perspective view of the upright cap; 
     FIG. 9 is a perspective view, partly fragmented, of a traction corner mounted to a transverse member of the louver assembly in accordance with the present invention; 
     FIG. 10 is a further perspective view, partly fragmented, of FIG. 9; 
     FIG. 11 is a perspective view of a housing element of the traction corner; 
     FIG. 12 is a perspective view of a pulling arm element of the traction corner; 
     FIG. 13 is a perspective view of a pulling mechanism of the traction corner; and 
     FIG. 14 is a perspective view of the traction corner. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings and more particularly to FIG. 1, a louver assembly is generally shown at  1 . The louver assembly  1  comprises a slat tensioning mechanism constructed in accordance with the present invention and located in region A of the lover assembly  1 . The slat tensioning device is not visible, but is adjustable through an upright end cap  12 . 
     As known in the art, the louver assembly  1  is defined by a plurality of slats  2  mounted at opposed ends to a pair of frame uprights  3 . The slats  2  are idle and enabled to pivot between the uprights  3 . The uprights  3  are parallel and are spaced apart by transverse frame members  4 . The uprights  3  consists of hollow channels, wherein a known mechanism is inserted, whereby the slats  2  are operatingly interconnected such that they remain parallel one to another while pivoting between the uprights  3 . The hollow channels of the; uprights  3  are, for instance, of rectangular cross-section with one of the sides thereof being removable, such as to provide access for installation and maintenance of the slat interconnecting mechanism within one of the hollow vertical channels. The louver assembly  1  is adapted to be secured to a window sill, such that the light, rain or snow is prevented from passing through. 
     Referring to FIGS. 2 and 3, the slat tensioning mechanism is generally shown at  10 . The upright  3  has been partly fragmented in order to depict the positioning of the slat tensioning mechanism  10  therein. It is noted that the slat tensioning mechanism  10  bears an end of a slat  2 , whereby the slat  2  is idle and enabled to rotate. 
     Referring now to FIG. 4, the slat tensioning mechanism  10  is shown having a casing  15  defined by a front wall  16 , lateral walls  17  and  18  and a bottom surface  19 . A cavity  20  is defined in the casing  15  and is bounded by the inner surfaces  21  of the front wall  16 , the lateral walls  17  and  18 , and by a substantially semi-circular surface  22  opposite the bottom surface  19  thereof. A circular opening  30  extends through the front wall  16  and is concentric with the semi-circular surface  22 . The semi-circular surface  22  operatingly bears a wheel  23 . A hole  50  extends through the front wall  16  at a top end thereof and adjacent the lateral wall  18 . 
     As best shown in FIG. 5, the wheel  23  is defined by a disk  24  having a front surface  25  and a rear surface  26 . An annular wall  27  laterally extends from the periphery of the disk  24 . The annular wall  27  has an outer surface  28 , whereby the wheel  23  is slidably engaged in the semi-circular surface  22  of the casing  15  as shown in FIGS. 2 to  4 . Accordingly, the wheel  23  is idle and free to rotate in the casing  15 . 
     The front surface  25  of the wheel  23  has an annular flange  29  laterally projecting therefrom. The annular flange  29  is circumferentially disposed on the front surface  25  of the wheel  23 . When the wheel  23  is disposed in the casing  15 , as depicted in FIGS. 2 to  4 , the annular flange  29  corresponds with the circular opening  30  of the casing  15 . Accordingly, when the casing  15  bears the wheel  23 , they are slidably engaged by the corresponding semi-circular surface  22 /annular wall  27  and circular opening  30 /annular flange  29 , whereby the wheel  23  is kept idle in the casing  15 . 
     Returning now to FIG. 5, it can be seen that the front surface  25  of the wheel  23  has a hub  31  laterally projecting therefrom. The hub  31  is concentric with the wheel  23 . The hub  31  defines an inner surface  32 . The inner surface  32  is adapted for matingly receiving an end pivot (not shown) of a slat therein. For instance, the inner surface  32  of the wheel  23  of the preferred embodiment is defined by an hexagonal cross-section (for a corresponding hexagonal cross-section end pivot of the slat  2 ), such that a rotation of the slat is transmitted to the wheel  23 , whereby the wheel  23  rotates about the casing  15 , as explained above. A cylindrical block  33  is concentrically located on the rear surface  26 , thereby structurally strengthening the disk  24 . 
     The wheel  23  further comprises slots  34  and  35  in the outer surface  28  of the annular wall  27 , whereby to limit the rotation of the wheel  23  about the casing  15 , as will be explained hereinafter. The slots  34  and  35  are symmetrically identical. The slots  34  and  35  each comprise a bottom surface  36  bounded by a radially extending straight surface  37  and a sloped surface  38 . Furthermore, a circular edge surface  39  ensures that there is no discontinuity in the sliding engagement surface of the perimeter of the wheel  23 . It is noted that the elements co-operating in sliding engagement consist of materials suitable therefor (e.g. acetal for anti-friction and wear-resistant characteristics). 
     Referring to FIGS. 2 to  4 , a tensioning member is generally shown at  40 . The tensioning member  40  comprises a block portion  41  and a resilient arm  42  connected to an end of the block portion  41 , such that the tensioning member  40  has a generally C-shape. The resilient arm  42  has a bulge  43  at a free end thereof. The bulge  43  has sloped portions  44  and  46 , each connected to a straight portion  45  and  47 , respectively. The block portion defines a planar top surface  48  and a pivot  49  laterally projecting from a side surface thereof. The tensioning member  40  is mounted to the casing  15  by the pivot  49  being interference fitted in the hole  50  of the front wall  16 . The interference fit is such that a non-negligible amount of force needs to be applied to the tensioning member in order for the pivoting thereof about the casing  15 . 
     As best seen in FIG. 4, a rectangular block  51  extends upward from the junction of the lateral wall  17  and the front wall  16  of the casing  15  and is integrally formed therewith. The rectangular block  51  has a tapped hole  52 , operatingly receiving a bolt  53 , whereby the vertical positioning of the bolt  53  may be varied. The rectangular block  51  and the tapped hole  52  are disposed on the casing  15  such that a bottom end of the bolt  53  may come into contact with a free end of the block portion  41  of the tensioning member  40 . Consequently, the bolt  53  may be displaced downward in order to apply a pressure on the free end of the block portion  41 . For instance, as seen in FIG. 2, a tooling end of a screwdriver S is shown on the verge of engaging with the bolt  53 . The screwdriver S will be inserted through the upright cap  1 , as will be explained hereinafter. As a result of the exerted pressure of the bolt  53 , the tensioning member  40  may pivot about the hole  50  in the casing  15 . 
     The tensioning member  40  is disposed in the casing  15  such that the bulge  43  of the resilient arm  42  is in contact with the wheel  23 . Furthermore, the resilient arm  42  is biased such that the bulge  43  exerts a pressure on the wheel  23 . The tensioning member consists of a material having, high memory characteristics (e.g. acetal). Accordingly, the bulge  43  will engage in the slots  34  and  35  when in corresponding positions. When either of the straight portions  45  and  47  of the bulge  43  abut the straight surface  37  of either one of the slots  34  and  35 , the wheel  23  will be prevented from rotating in a direction. Therefore, the slats are limited in going from a vertical position, as shown in FIG. 3, wherein the bulge  43  is engaged in the slot  34 , to a horizontal position, wherein the bulge  43  is engaged in the slot  35 . 
     It is noted that the bulge  43  exerts a pressure on the outer surface  28  of the annular wall  27  when not inserted in either one of the slots  34  and  35 . The exerted pressure may be such that the wheel  23 , and thus the plurality of interconnected slats  2  of the louver assembly  1 , may be arrested in a given position. Consequently, a person may choose a desired opening of the slats, which will be frictionally held by the action of the tensioning member  40  on the wheel  23 , as explained above. If the pressure exerted by the tensioning member  40  is too small to hold the slats in a sloped position, the tensioning member  40  can be pivoted as explained above in order to exert more pressure. Similarly, pressure can be removed from the tensioning member,  40  by loosening the bolt  53 . 
     The casing  15  is sized such that it is frictionally held in vertical position in the channel of the upright, as. seen in FIG.  3 . On the other hand, it can be integrally formed in the upright  3 . Consequently, no fastening elements nor bonding is necessary in order to secure, the slat tensioning device  10  therein. Furthermore, once a slat is inserted in the hub  31  as explained hereinabove, the vertical stability is ensured. 
     In order to have access to the bolt  53  to modify the pressure exerted on the tensioning member  40 , known elements typical to louver assemblies have been modified. For instance, the upright cap  12  and the traction corner  11  have been modified in accordance with the present invention to provide bolt access for the adjustment of the slat tensioning device  10 . 
     Referring to FIG. 2, the upright cap  12  in accordance with the present invention is shown mounted at a top of one of the uprights  3 . It is noted that the upright cap  12  could have been disposed at a bottom end of the upright  3 , wherein the slat tensioning device  10  would have been mounted to the lowest slat, with the bolt  53  thereof downwardly projecting. 
     Referring now to FIG. 8, the upright cap  12  is comprised of a generally rectangular plate  59  having a top surface  60  and a bottom surface  61 . The edge walls  62 ,  63 ,  64  and  65  laterally project from the periphery of the bottom surface  61 , whereby a downwardly facing cavity is formed. A through bore  66 , adjacent the junction of the edge walls  64  and  65 , extends from the top surface  60  to the bottom surface  61 . A resilient finger  67 , adjacent the edge wall  64  and generally in the middle of the cap  12 , extends downwardly from the bottom surface  61 . A hook portion  68  is formed at a free end of the resilient finger  67 . Furthermore, a rectangular hole  69  extends from the top surface  60  to the bottom surface  61  of the cap  12  at the foot of the resilient finger  67 , such that a tool may be inserted therein for deflecting the hook portion  68  of the resilient finger  67 . Similarly, a resilient finger  70 , identical to finger  67 , is located adjacent the edge wall  62  in alignment with the resilient finger  67  and also has a hook portion  71  and a rectangular hole  72 . A rib  73  extends upwardly from the top surface  60  and is located above the edge wall  63 . The rib  73  serves structural purposes, whereby the upright cap  12  is strengthened. 
     The upright cap  12  further comprises a cylindrical receptacle  74  in the surface  61 , adjacent the rib  73 , for receiving a button  75  therein. The button  75  is upwardly biased, in this case by a compression spring  76 , and may comprise a flange or the like at a bottom end thereof (not shown) such that it is kept in the receptacle  74 . Returning now to, FIG. 2, the upright cap  12  is shown mounted on the upright  3  of the louver assembly  1 . The upright cap  12  is dimensioned in order to have its edge walls  62 ,  63 ,  64  and  65  in a planar side-by-side relationship with the lateral walls defining the upright  3 . As known in the art, the finger  67  and  70  engage in a releasable locking with receiving elements within the hollow body of the upright  3 . The cap may be removed by deflecting the hook portions  68  and  71  of the resilient fingers  67  and  70 , respectively, wherefore a lever is inserted in the rectangular holes  69  and  72 . The upright cap  12  is disposed on the upright  3  such that the through bore  66  therein corresponds to the positioning of the bolt  53  of the slat tensioning device  10 , whereby the tooling end of the screwdriver S may access the head of the bolt  53 . 
     The upwardly biased button  75  of the upright cap  12  provides a louver assembly with snap-engagement means for the quick and easy retention and removal thereof upon a window sill. As seen in FIG. 1, the louver assembly  1  is small enough to be handled manually. For instance, the type of louver assembly depicted in FIG. 1 may be removed from a window sill W for maintenance purposes, such as for cleaning. As shown in FIG. 7, the button  75  is shown engaged in a corresponding groove G of the window sill W. FIG. 6 shows a different view of the engagement of the louver assembly  1  to the window sill. The button  75  of the upright cap  12  allows for the automatic snap-engagement thereof in the receiving groove G within the channel of the window sill. Whether the louver assembly is releasably secured to the window sill, whereby it can be completely removed therefrom, or it is hinged at an upright thereof to the window sill to rotate thereabout, no fastening elements are required to proceed with the snap-engagement thereof to the window sill. 
     It is pointed out that the spring biasing mechanism of the button  75  is not necessary for all instances. The upright cap  12  may be provided with a molded button (not shown) when a high stroke of deflection is not necessary. As the upright cap consist in a slightly resilient material (e.g. plastic), it can bend slightly to allow for the snap-engagement of its molded button in the corresponding groove of the window sill. In this case, the upright cap having a molded button does not require a receptacle such as receptacle  74 . 
     As described above, the upright cap of the present invention is advantageous as it provides access to the tensioning bolt of the slat tensioning mechanism. Furthermore, the upright cap  12  does not require fasteners nor bonds, as opposed to the systems known in the art. 
     Also, magnets have been used to secure the louver assembly to the window sill. As magnets have been known to gradually lose their polarity over time, the snap-engagement button  75 , either spring-biased or molded, provides a more durable solution. Finally, when the upright cap  12  is used in combination with the slat tensioning device, the resulting louver assembly comprises discreet features. As described above, once the louver assembly is mounted to the window sill, the through bore  66  in the upright cap is hidden, whereby no trace of the slat tensioning mechanism is apparent. 
     In order to assemble a pair of uprights to a transverse member, while using the slat tensioning device  10  of the present invention with the upright cap  12 , the connecting means between the uprights and the transverse members must take into account that access must be provided between the through bore  66  of the upright cap  12  and the bolt  53  of the slat tensioning device  10 . 
     A traction corner  11  is provided to connect an upright and. a transverse frame member each having corresponding obliquely cut ends. Referring to FIGS. 9 and 10, the traction corner  11  is shown mounted to a transverse member  4  having a 45 degree slant end face. As best shown in FIG. 14, the assembled traction corner  11  comprises a right angle connector body  80  and a traction connecting clip  81 . More particularly, the connector body  80  and the traction connecting clip  81  are each shown individually in FIG.  11  and FIG. 12, respectively. 
     Referring to FIG. 11, the connector body  80  is comprised of a pair of arms  80 ′ and  80 ″, each arm having walls  82  and  83 . The walls  82  and  83  are spaced apart by spacing posts  84  and form a gap  90  therebetween. A pair of transverse walls  85  and  86  are also connected to both the walls  82  and  83 . The transverse walls  85  and  86  are interconnected at a right angle, and are located at the inside corner of the right angle of the connector body  80 . 
     The transverse walls  85  and  86  project above and below the assembly of the walls  82  and  83 , to form flanges  87   a  and  88   a  which laterally project from a top surface of the L-shaped wall  82 , and flanges  87   b  and  88   b  which laterally extend from a bottom surface of the L-shaped wall  83 . 
     A hole  89  extends through the junction of the transverse walls  85  and  86 . Consequently, the hole  89  is centered at the inside corner of the right angle defined by the connector body  80 . 
     A guide  92  protrudes from the surface of the wall  82  within the gap  90  and extends from the junction of the transverse walls  85  and  86  to the apex of the right angle connector body  80 . Similarly, a guide  93  protrudes from the surface of the L-shaped wall  83  within the gap  90 , and extends from the junction of the transverse walls  85  to  86  to the apex of the connector body  80 . The guides  92  and  93  are substantially rectangular shaped. 
     Referring now to FIG. 12, the connecting clip  81  is comprised of a core portion  95  having a pair of opposed pulling arms  96   a  and  96   b . The pulling arms  96   a  and  96   b  are identical. The core portion  95  is comprised of a generally rectangular block having a front surface  97 , a rear surface  98 , lateral side surfaces  99  and  100 , and top and bottom surfaces  101  and  102 , respectively. A hole  103  extends from the front surface  97  to the rear surface  98  and has a circular portion  104  open at the rear surface  98 . The circular portion  104  connects to a hexagonal counterbore  105 , the latter emerging in the front surface  97 . A groove  101   a  is defined in the top surface  101  of the core portion  95 , and extends from the front surface  97  to the rear surface  98 . Similarly, a groove  102   a  is defined in the bottom surface  102 , and extends from the top surface  97  to the rear surface  98 . 
     The pulling arm  96   a  generally extends from the junction of the front surface  97  and the lateral side surface  99 . Similarly, the pulling arm  96   b  generally extends from the junction of the front surface  97  and the lateral side surface  100 . For simplicity, the pulling arm  96   a  will be described and like numerals affixed with a letter “b” on the pulling arm  97   b  in FIGS. 12 and 14 will designate equivalent elements. A head  106   a  is comprised at a free end of the pulling arm  96   a . The head  106   a  has a square front surface  107   a  whereon a tooth  108   a  is located. The tooth  108   a  is generally centered about the square front surface  107   a  and is inwardly facing towards the core section  95 . 
     Referring now to FIG. 13, a pulling mechanism  110  is shown. The pulling mechanism  110  has a bolt  111  having a flat head, a hexagonal nut  112  operatingly engaged thereon, and a backing plate  113 , abutting the flat head portion of the bolt  111 . As depicted in FIG. 13, the backing plate  113  of the preferred embodiment is defined by a panel having a pair of slanted wings for planar engagement with the transverse walls  85  and  86  of the connector body  80 , for purposes which will be explained hereinafter. A hole  114  is generally centered on the backing plate  113  and extends therethrough. The hole  114  is concentric with the flat head of the bolt  111 , such that the tooling end of a screw driver can pass therethrough to operate the bolt  111 . Furthermore, the hole  114  has a diameter smaller than the flat head of the bolt  111 , such that the flat head and the backing plate  113  are always abutted, yet the bolt  111  turns independently of the backing plate  113 . The backing plate  113  has a slot  115   a  in an upper edge thereof, and a slot  115   b  in a bottom edge thereof. 
     The pulling mechanism  110  is inserted in the connecting clip  81 , with the nut  112  matingly engaged in the hexagonal counterbore  105 , whereas the bolt  111  extends through the circular portion  104  thereof. Consequently, the bolt  111  may translate about the connecting clip  81  when rotated, whereas the nut  112  is secured thereto by the mating engagement. 
     Thereafter, the pulling mechanism  110 /connecting clip  81  assembly, as described above, is inserted in the connector body  80 . As shown in FIG. 14, this is achieved by the grooves  101   a  and  102   a  of the core portion  95  being slidably engaged in the guides  92  and  93  of the connector body  80 , respectively. Similarly, the slots  115   a  and  115   b  of the backing plate  113  of the pulling mechanism  110  also slidably engage with the guides  92  and  93  of the connector body  80 , respectively. Consequently, the backing plate  113  is sandwiched between the flat head end of the bolt  111  and the transverse walls  85  and  86  of the connector body  80 . 
     The connecting clip  81  is free to slidably translate upon the guides  92  and  93  of the connector body  80 . Also, the length of the pulling arms  96   a  and  96   b  is such that the square front surfaces  107 A and  107 B thereof extend outward of the gap  90 , at opposed ends of the transverse walls  85  and  86 , respectively. Finally, the core section  95  of the pulling arm element is positioned in the connector body  80  such that the flat head end of the bolt  111 , and thus the hole  114  in the backing plate  113 , are substantially concentric with the hole  89  at the junction of the transverse walls  85  and  86 . The resulting assembly is the traction corner  11  of the present invention, as depicted in FIG.  14 . 
     As shown in FIG. 9, the traction corner  11  is inserted in the obliquely cut end transverse member  4 , which consists of hollow channels. It is noted that the transverse member  4  has a hole  4   a  defined therein. Accordingly, the traction corner  11  is slid in the hollow channel of the transverse member  4  until tooth  108   b  is captively engaged in the hole  4   a  thereof. The flanges  87   b  and  88   b  may be provided to obtain a mating slide in the hollow channels of the transverse member  4  according to the shape thereof. FIG. 10 illustrates a different view of the above described engagement. 
     Thereafter, an upright also having hollow channels (not shown) is joined to the free end of the traction corner  11 , whereby the latter is captively engaged therein by its tooth  108   a . As a result thereof, the obliquely cut ends of the upright and transverse member  4  are face-to-face and separated by a small gap. As partly seen in FIG. 9, corresponding semi-circular holes are provided in the transverse member and in the upright, whereby a tooling end of a screwdriver may operate the bolt  111  of the traction corner  11  when the latter is inserted in the transverse member and in the upright. The hole thereby formed is substantially concentric with the hole  89  of the traction corner  11 . 
     When the bolt  111  is turned in one direction, the nut  112  and the flat head end of the bolt  111  will move in opposite directions, as readily known. Thus, the nut  112  will exert pressure against the core portion  95 , whereas the flat head end will exert pressure on the backing plate  113  and thus the transverse walls  85  and  86  of the body  80 . Consequently, the core section  95  will have a tendency to move. away from the transverse walls  85  and  86  as it translates on the guides  92  and  93 . As the pulling arms  96   a  and  96   b  are connected to the upright and transverse members, respectively, they will move one towards the other, whereby pulling the upright and transverse member one towards the other. The bolt  111  is thus rotated until the obliquely cut ends of the upright end transverse member meet, whereby they are in coplanar engagement. Alternatively, the bolt  111  may be turned in the opposite direction in order to loosen the upright from the transverse member, whereby they can be separated and disassembled. 
     The traction corner  11  of the present invention is simple in construction, and simple in use as only one screw needs to be handled, thereby reducing the time usually necessary to mount such assemblies. The only tool required for the mounting thereof to obliquely cut frame members is a screwdriver. Furthermore, access to the tightening bolt is provided from the inside of the frame members, which means that the frame member can be tightened when they are installed on a window sill. Also, the traction corner  11  does not require much space within the frame members, whereby the remaining space can be used to provide screwdriver access to the slat tensioning device of the present invention. 
     It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims.

Summary:
A slat tensioning mechanism is provided for holding interconnected slats of a louver assembly in a desired angulated position. The slat tensioning mechanism comprises a housing having wheel positioning means for rotationally receiving a bearing wheel. The bearing wheel has an outer circumferential flat wall, and hub means adapted for securement to an end connector of a slat, whereby the bearing wheel and the slat rotate together. A tensioning arm assembly is pivotedly engaged to the housing and has an arm disposed at a predetermined location with respect to the outer circumferential flat wall of the bearing wheel. The arm has a friction surface at a free end thereof for applying a pressure on the outer circumferential flat wall of the bearing wheel for frictionally arresting the bearing wheel at the desired position. The slat tensioning mechanism is adapted to be disposed in an upright of the louver assembly. A cap is secured to an end portion of the upright of the louver assembly and has a button in its top surface adapted for snap-engagement with a corresponding groove of a window sill. A traction corner is provided for releasably assembling a pair of hollow frame members and provides adjustable mating engagement.