Abstract:
A casement window hinge eliminates the use of rivets in the pivot between the sash arm and guide arm such as require a high force deformation of an element to a precise compression that varies according to a “tolerance stack up” between four controlled dimensions of the parts being assembled: the length of the rivet, the deformation of the rivet head, and the thickness of the two arms being assembled. The invention eliminates two of these dimensions through the use of integrally molded pivot pins that fit into a bore in the second arm and which are plastically flanged. Resistance to a pull-out of wood screws that are countersunk into a plastic sash arm is provided by exaggerated counter sinking with undersized countersink bores.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    — 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    — 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to casement window hinges and in particular to a casement window hinge with a sash arm and guide arm providing improved manufacture. 
         [0004]    Casement window hinges allow a window to open by pivoting about a vertical axis that moves inward as the window opens. This combination motion is provided by special casement window hinges supporting the window sash. A separate operator moves the window as mounted on the hinges, typically through the use of a crank mechanism. 
         [0005]    Casement window hinges typically employ a two-bar linkage of a sash arm and guide arm. The sash arm is attached along the window sash, for example, by countersunk wood screws directed up through the sash arm into the wood of the sash. An inward end of the sash arm is pivotally attached to a slide that may move along a track attached to the window opening and that defines the movable pivot point of the window. A center of the sash arm is pivotally attached to one end of a guide arm whose remaining end of the guide arm is pivotally attached to the track displaced from the slide. 
         [0006]    The sash arm and guide arm can be subject to large forces, for example, during shipping, installation, or when the window is subject to wind loads. For this reason, the sash arm and guide arms are typically fabricated out of a sturdy metal such as stainless steel. They are connected together, typically, by a metal rivet that is lightly staked to allow the parts to pivot. Normally the slide is also riveted to the sash arm. 
         [0007]    For smooth and reliable operation, it is important that the rivets between the sash arm, guide arm and slide be tight to prevent excess play between these parts that may cause premature wear or “hammering” in the joints under wind load. On the other hand the rivets must not be so tight as to promote excess friction making the window hard to open or close. While riveting is a simple operation when a joint must be tightly fastened, controlling the large forces required to properly stake the rivets to provide just the right compression for a pivoting joint is extremely difficult. Tolerance “stack up” in the variations of the length of the rivet, the deformation of its head during the staking process, and in the thickness of the two pieces being assembled, makes it difficult to ensure low play in the pivot as well as low friction. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention provides an improved casement window hinge that employs plastic pivot pins connecting between plastic sash and guide arms. The pivot pins may be thermally staked after insertion through a corresponding hole to eliminate play in the pivoting joint. Friction that can prevent the joint from moving, as can occur with the compression incident to metallic rivets, is avoided in the present invention by the natural lubricity of the plastic-to-plastic interface and/or the staking process that does not produce substantial compressive forces. In a preferred embodiment, the pivot pins are integrally molded into one or both of a plastic sash arm or guide arm further eliminating play caused by looseness between the pivot pins and sash or guide arm. 
         [0009]    The inventor has further determined that the problems of countersunk wood screws pulling through a plastic sash arm can be solved by substantially decreasing the size of the countersink thus significantly increasing the contact area between the screw head and the plastic sash arm over the length of the countersink. Mismatch between the shaft size of the wooden screw and the small bore size, such as would be a problem in a metal sash arm, is avoided in a plastic sash arm where the much harder wood screw may slightly enlarge the countersink bore in the plastic sash arm during installation. Finally, the problem of excessive torques being placed on a sash-arm stop (needed to limit opening of the window) are solved by use of a hinging slide stop that permits assembly of the slide into its track but, by moving the stop along the sash arm to the slide, reduces destructive torques on the stop. 
         [0010]    Specifically then, the invention provides a casement window hinge having a longitudinally extending track attachable to a window opening, a slide retainable by the track for movement therealong, a sash arm pivotally attached to the slide at an inner end attachable to a window sash, and a guide arm pivotally attached at one end to the track and at the other end to the sash arm. The sash arm and a guide arm are constructed of a moldable thermoplastic and are joined by a pivot pin passing through a hole formed in one of the sash arm and guide arm, where the pivot pin is constructed of a moldable thermoplastic material having at least one flange to retain the sash arm and guide arm attached together in a pivoting relationship. 
         [0011]    It is thus one feature of one embodiment of the invention to provide an improved pivot for casement hinges that eliminates play that can result in damaging joint forces while naturally limiting joint friction. 
         [0012]    The pivot pin may be integrally molded with the one sash arm and guide arm. 
         [0013]    It is thus another feature of the invention to provide even further reduced joint play by forming the pivot pin integrally with one of the sash and guide arms. 
         [0014]    The flange may be thermally formed to be larger than would reversibly pass through the hole. 
         [0015]    It is thus an aspect of one embodiment of the invention to provide a staking method that provides near zero joint play with limited joint compression. Because the thermal staking essentially melts the end of the pivot pin, the flange may abut the pivoting arm with near zero clearance and yet without the compressive forces normally part of a staking process deforming a metal rivet. 
         [0016]    The casement window hinge may further including a pivot between the slide and the sash arm including a second pivot pin passing through a hole formed in one of the sash arm and slide, the second pivot pin constructed of a moldable thermoplastic material having at least one flange to retain the sash arm and slide attached together in a pivoting relationship. 
         [0017]    It is thus another aspect of one embodiment of the invention to provide similar benefits for the connection of the sash arm and slide. 
         [0018]    The sash arm may include a plurality of holes having frustro-conical counter sinks in which a larger base of the frustum has a radius substantially twice the radius of that of the smaller base. 
         [0019]    It is thus a feature of one embodiment of the invention to permit the use of thermoplastic materials for the construction of the sash arm and guide arm. By decreasing the countersink bore radius, the total conical area contacted by the screw head is increased by a square of the radius decrease, providing a disproportionate increase in pullout strength. Tolerance problems from this reduced countersink bore size can be accommodated by the ability of the thermoplastic material to flow under pressure from a countersink screw. Use of plastic sash and guide arms allows integral formation of the plastic pivot pins and a desirable plastic-on-plastic pivot pin interface. 
         [0020]    The slide may include an extension abutting a stop affixed to the track when the sash arm is perpendicular to the track. 
         [0021]    It is thus an aspect of the invention to displace torsional forces from the pivot between the sash arm and the guide arm allowing both to be practically molded of plastic. 
         [0022]    The extension may include a live hinge allowing it to be displaced from the stop for removal of the slide. 
         [0023]    It is thus an aspect of the invention to allow simplified assembly of the hinge with a stop on the slide that automatically assumes a stop function once assembled. 
         [0024]    A pivot between the guide arm and the track may have a boss constructed of a moldable thermoplastic material and attached to the track and received in a snap fit with a corresponding bore in the guide arm. 
         [0025]    It is thus another feature of one embodiment of the invention to provide for a plastic-to-plastic interface in connecting the guide arm to what is typically a metallic track. 
         [0026]    The boss may be eccentrically mounted for rotation with respect to the track. 
         [0027]    It is thus another feature of one embodiment of the invention to allow for correction of sagging in the hinge by changing the effective length of the guide arm. 
         [0028]    The boss may rest on a tubular extension from the track receiving a screw fitting into the tubular extension. 
         [0029]    It is thus another feature of one embodiment of the invention to provide a well-registered metallic attachment point for the guide arm. 
         [0030]    The snap fit may be provided by an interfitting ridge and groove formed at a circumferential interface between the boss and corresponding bore. 
         [0031]    It is thus a benefit of one embodiment of the invention that it provides simple field attachment of the guide arm to the track without removing the boss. 
         [0032]    An exposed face of the boss may include a slot for receiving a screwdriver for rotation of the boss. 
         [0033]    It is thus a benefit of one embodiment of the invention to allow simple adjustment of sash sag by the consumer. 
         [0034]    These particular features and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]      FIG. 1  is a top plan view of the casement window hinge of the present invention showing the sash arm, guide arm, slide and track structures common to hinges of this type; 
           [0036]      FIG. 2  is a perspective view of the slide of  FIG. 1  showing an extension with a living hinge providing a stop for the window at full opening; 
           [0037]      FIG. 3  is a cross-sectional view through lines  3 - 3  of  FIG. 1  showing a thermally formed flange on a pivot pin attaching the sash arm to the slide, the flange received within a counter bore in a slide to remain recessed within the slide; 
           [0038]      FIG. 4  is a fragmentary perspective view of a pivot mechanism connecting the guide arm to the track showing an eccentric mechanism for adjusting the effective guide arm length; 
           [0039]      FIG. 5  is a cross-section through lines  5 - 5  of  FIG. 4  showing assembly of the eccentric mechanism to a coined post on the track; 
           [0040]      FIG. 6   a  is a phantom view of a prior art countersunk bore in the sash arm; 
           [0041]      FIG. 6   b  is a figure similar to that of  FIG. 6   a  showing a bore with extended surface area providing increased pullout resistance to wood screws; 
           [0042]      FIG. 7  is a front elevational view in partial cross-section of the track and slide of the present invention showing a flared track channel permitting alignment of the slide with the track for shorter windows; 
           [0043]      FIG. 8  is a figure similar to  FIG. 7  in side elevation, showing a chamfer on the slide permitting alignment of the slide and the track for longer windows; and 
           [0044]      FIG. 9  is a fragmentary perspective view of the extension of  FIG. 2  and corresponding stop formed in the slide. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    Referring now to  FIG. 1 , a casement window hinge  10  may include a sash arm  12  that may be attached to a window sash  15  by means of mounting holes  14  receiving countersunk head wood screws (not shown in  FIG. 1 ) upward through the sash arm  12  therethrough. A proximal end of the sash arm  12  is pivotally attached to a slide  16  that may move along a length of a metal track  18  as retained by a rolled flange  20  in the metal track  18 . 
         [0046]    A proximal end of a guide arm  22  is pivotally attached to the track  18  at an end  23  of the track  18  removed from the travel range of the slide  16 , and a distal end of the guide arm  22  is pivotally attached to a midpoint  24  of the sash arm  12 . The sash arm  12  and guide arm  22  form a two-bar linkage providing a simultaneous pivoting and translation of an attached window. The general structure of hinges of this type is described in U.S. Pat. No. 6,088,880 to LaSee, assigned to the assignee of the present invention and hereby incorporated by reference. 
         [0047]    Referring now also to  FIG. 2 , the slide  16  includes a leftward extending stop arm  41  whose end may abut a stop  40  formed in the track  18  to prevent the window from opening too far as will be described below. 
         [0048]    A rear edge of the slide  16  and stop arm  41  supports an upwardly extending ridge  17  that may be captured under the rolled flange  20  of the track  18 . This ridge  17  extends leftward from a slide body  19  to provides a living hinge  27  between the slide body  19  and the stop arm  41  allowing the latter to flex to an assembly position  38  away from the stop  40  so that the slide  16  may be assembled into the track  18  at a portion of the track  18  not having the rolled flange  20 . Upon completion of that assembly, the natural elasticity of the living hinge  27  returns the stop arm  41  to the straightened position so that leftward travel of the slide  16  is ultimately blocked by the stop  40 . 
         [0049]    Referring now to  FIG. 3 , the slide  16  and distal end of the guide arm  22  include counterbored holes  21  having a principal diameter  28 , and a counterbore diameter  30  on their underside larger than principal diameter  28 . Corresponding pivot pins  44  on the sash arm  12  may extend downward from the surface of the sash arm  12  to be received within these bores  26 . The pivot pins  44  have a cylindrical shaft  34  with a diameter conforming to principal diameter  28  of the bore  26 . 
         [0050]    An end of the shafts  34  extending through the principal diameter  28  of the bores  26  may be thermally staked to create a flanged head  36  of diameter less than the counterbore diameter  30  and a thickness less than the depth of the counterbore to fit wholly therein, but of diameter greater than the principal diameter  28  of the counterbored holes  21  so as to retain the pivot pin  44  within the counterbored holes  21 . The staking process may be performed by a number of thermal staking techniques including ultrasonic or heated plate staking and provides a near zero-tolerance fit between a flanged head  36  and a seat of the counterbored holes  21  with very little compressive force as a result of the melting of the material of the pivot pin  44 . 
         [0051]    In a second embodiment, the flanged head  36  may be preformed to a diameter allowing a snap fit with the counterbored holes  21 . The flanged head  36  may be bored and slotted to assist in its compression during this snap fit. 
         [0052]    Ideally the pivot pins  44  are molded to be integral with the thermoplastic sash arm  12 , a material choice for the sash arm  12  that is made possible by fabricating the sash arm  12  of a thermoplastic material strengthened, for example, with glass fiber. By constructing both the sash arm  12  and guide arm  22  out of thermoplastic, a plastic-to-plastic interface is formed resisting binding and destructive wear between the pivot pin  44  and the sash arm  12  or guide arm  22 . 
         [0053]    As will be understood in the art, the slide  16  may also be molded from a thermoplastic material and typically is molded about a steel spine  43  which, in this case, may include a hole amply sized to allow the molding of the counter bored hole  21  into the slide  16 . 
         [0054]    Referring now to  FIGS. 1 ,  4  and  5 , the attachment of the proximal end of the guide arm  22  to the track  18  (constructed of sheet metal in the present invention) is obtained through a molded thermoplastic boss  46  attached to the track  18  (as will be described) and snap-fitting into a corresponding bore  48  in the proximal end of the guide arm  22 . The boss  46  has a generally cylindrical outer surface and thus may rotate within the guide arm  22  when twisted by a screwdriver inserted into a slot  49  cut in the upper face of the boss  46 . The boss  46  provides a rotation axis  50  with respect to its attachment to the track  18  (as will be described) that is eccentric with respect to an outer circumference of the boss  46 . Thus, rotation of the boss  46  with respect to the guide arm  22  causes an effective change of the length of the guide arm  22  as may correct for sash sag as described generally in U.S. Pat. Nos. 4,790,106 and 5,017,075, assigned to the same assignee as the present invention and hereby incorporated by reference. 
         [0055]    Referring to  FIG. 5 , the attachment of the boss  46  to the track  18  is provided by means of a coined protrusion in the track  18  providing an upwardly extending, upwardly open tube  52  integrally formed in the track  18 . The inside of this open tube  52  may be threaded to receive a pan head, hex drive, machine screw  60  whose head may retain the boss  46  against axial movement with respect to the track  18  while allowing rotational movement of the boss  46  about the machine screw  60   
         [0056]    The snap connection between the boss  46  and the guide arm  22  is provided by opposed downwardly cantilevered spring fingers  54  molded into the inner diameter of the bore  48  of the guide arm  22  receiving the boss  46 . Teeth  56  at the lower edge of the spring fingers face inward to receive a corresponding outwardly open rim  57  in the lower edge of the boss  46 . 
         [0057]    Referring now to  FIGS. 6   a  and  6   b , in a prior art, hole  14 ′ receiving countersunk head wood screws to attach the sash arm  12  to a window sash provided an amply-sized countersink bore  63 ′ cut through the sash arm  12  avoiding interference between a shaft of the wood screw and a too-small bore in a metallic sash arm  12 . Limited conical counter sinking  62 ′ is provided so that the head of the wood screw would be flush with a surface of the sash arm  12  to prevent interference in the opening and closing of the window by a protruding screw head. 
         [0058]    In the present invention, the radius of the countersink bore  63  is significantly reduced to equal or be slightly less than the expected diameter of the shaft of a wood screw. This reduction in radius increases the total area of the conical counter sinking  62  as a square of the reduction in radius to provide sufficient pullout resistance in the plastic of the sash arm  12 . The conical counter sinking  62  provides a frustro-conical surface having an upper base of greater diameter and a lower base of lesser diameter. In the preferred embodiment, the radius of the upper base is no less than substantially twice the radius of the smaller base. The increased risk of interference between the smaller hole size of the smaller base and the shaft of the wood screw is remedied by the soft characteristic of the plastic material allowing the wood screw to slightly enlarge this hole as needed. The present inventor has determined that this radius reduction provides a sufficient pullout resistance to allow construction of the sash arm  12  from a reinforced plastic material. 
         [0059]    Referring now to  FIG. 7 , the slide  16  may be pulled upward by an amount  72  when sash arm  12  is attached to a sash (not shown) in a window that is dimensionally shorter than expected. This can make it difficult to insert a guide ridge  17  of the slide  16  under the rolled flange  20 . For this reason, the present invention provides for an upward flaring of the rolled flange  20  to provide a funneling of the guide ridge  17  of the slide  16  into the rolled flange  20  when the slide  16  is first assembled onto that track  18 . Similarly, as shown in  FIG. 8 , a rear edge of the slide  16  includes a chamfer  76  so that, in the opposite situation, where the slide  16  is displaced downward when used with a window that is dimensionally taller than expected, the chamfer  76  guides the slide  16  up onto the surface of the track  18 . 
         [0060]    Referring now to  FIGS. 1 and 9 , opening of the sash  15  such as would move the sash  15  leftward  74  beyond a perpendicular orientation with respect to the track  18  is stopped by abutment of the stop arm  41  of the slide  16  against the stop  40 . This portion of the track  18  near the stop  40  does not have a rolled flange  20  allowing the stop arm  41  to be flexed by means of a living hinge  27  away from the stop  40  for disassembly. 
         [0061]    The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.