Abstract:
A method and apparatus for connecting framing components for windows and doors is disclosed. The method involves the use of a vibrating source, which when applied to the frame components, locally excites the surface, thereby conditioning the members to be welded.

Description:
This application is a Divisional of application Ser. No. 08/742,734, filed Nov. 1, 1996 U.S. Pat. No. 5,902,657 which is a continuation in part of application Ser. No. 08/518,229 filed Aug. 23, 1995, abandoned which is a continuation in part of application Ser. No. 08/379,050 filed Jan. 27, 1995, abandoned. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to vibratory welding of window and door components, and to a method and apparatus for manufacturing the same. 
     BACKGROUND OF THE INVENTION 
     Many technological improvements in window and door design have been made available over the last several years. For instance, the insulating properties of newer window constructions are greatly improved over older window constructions, which can provide a significant energy savings to property owners. Consequently, a significant need has developed to replacing windows and doors during remodeling of older homes and buildings with newer more efficient components. 
     However, most conventional windows, doors, patio doors, etc. are currently built to standardized dimensions. Since different sizes of windows and doors require differently sized components, it is common practice for manufacturers to offer only a limited number of standardized sizes of windows and doors, which reduces the overall manufacturing complexity and costs of these structures based on the efficiencies obtained through economies of scale. 
     Many older windows and doors do not conform to standard sizes, and is often difficult to find replacement windows which exactly fit the roughed-in dimensions of a window or a door to be replaced. Therefore, some standard sizes of windows and doors are often not acceptable substitutes as replacement windows. Often, replacement applications may require custom built windows or doors, which typically require individual components to be separately manufactured to size. Consequently, custom window construction does not obtain the benefits of economy to scale, e.g. high volume production of structures used in standardized parts. Thus, many custom windows and doors are significantly more expensive than their standardized counterparts. 
     Therefore, a need exists for a method of manufacturing windows and doors of custom sizes and shapes which is fast and provides an inexpensive manufacturing process. 
     A need also exists for improving the manufacturing of standard size windows made from new materials. Many new polymeric and composite materials are being used for the manufacture of standard sized and replacement sized windows, and thus the manufacturing needs for all styles of windows and doors needs to be modified to accommodate these new materials. 
     Along this line, a need has developed for improved joint structure for joining framing components made from new materials, such as window sashes, window frames, door frames, etc. For example, windows typically require joint structures for sashes which retain a window glass assembly within a frame. A window glass assembly is typically a single pane of glass, or alternatively, a self-contained, multi-paned insulated glass unit whereby two or more panes are stacked and sealed about the perimeters, with a partial vacuum and/or an insulating gas such as argon contained within the sealed space between the panes. 
     Generally, a sash used to retain a window glass assembly includes framing components which are generally L-shaped in cross-section. A silicone sealant is layered along the inside of the frame, and then the window glass assembly is placed in the frame against the silicone sealant. A glazing bead is then installed around the open side of the sash to retain the window glass assembly therein. 
     It is also known to include spacer blocks sandwiched between the edges of the window glass assembly and the L-shaped channel in the sash, which forms a condensation channel and centers the pane in the sash. Further, by constructing the sash members of a weldable plastic, it is known that custom sashes may be constructed by miter cutting individual members to size, then butt welding the ends of the sash members together. 
     Prior to this invention, this butt welding has occurred through heat welding or ultra-sonic welding. 
     Heat welding involves heating a platen of some type, placing the heated platen in contact with the surface to be welded (oftentimes a thermoplastic material of some type) heating the bonding surface until there is flow, withdrawing the heated platen, and then placing the two bonding surfaces in contact. Thereafter, the heated bonded surface must cool. Heat welding has numerous drawbacks. One drawback is the length of time necessary to heat the welding surfaces to a temperature sufficient for welding. This can take in excess of 30 seconds, which is very slow from a manufacturing point of view when often times millions of units are assembled over the course of a year. Another drawback is if the material which is being welded has good thermal properties, the transfer of heat can be slow so cooling is often slow. The heated surfaces may often experience degradation. Thus a more efficient method of creating a welded joint is needed. Another process for welding window frames is disclosed is U.S. Pat. No. 4,856,230, assigned to Slocomb Industries, which describes a method of securing vinyl window frames together with ultra-sonic welding. U.S. Pat. Nos. 5,105,581, 4,224,091, and 4,090,799 all further discuss the use of ultra-sonic welding techniques in window applications. However, the use of ultra-sonic welding, which requires a horn to be positioned over the weld, whereby the horn admits ultra-sonic frequencies, has numerous drawbacks. In order for an effective weld to take place, often times it is necessary to have multiple horns, with multiple horns for each weld, in that often times with a joint having complex geometry, one horn cannot sufficiently weld the joint portion which is opposite the point farthest from the horn. Further, ultra-sonic welding, although faster than thermal welding involving a heated platen, still suffers from a somewhat slow weld time. A typical ultra-sonic weld may take approximately five or more seconds in order for the weld faces to be melted sufficient such that a weld can occur. A further disadvantage with both thermal heat or ultra-sonic welding is that anytime a thermal plastic material is heated and welded, degradation and excess flash will occur around the weld. As the two faces are bonded together, excess thermoplastic flow occurs which results in the thermoplastic material flowing outside the weld and on the surface of the members which form the weld. This degraded excess flash must be removed in that it diminishes the decorative appearance of the weld. As a general rule, the longer the weld takes to form, the more flash will occur. Thus, it is desirable to produce a weld in a very short period of time, thus minimizing the flash. 
     There is also a need in the art for a window assembly process whereby sash members may be assembled around a glass assembly in a faster and less expensive manner while having an improved decorative appearance. Welding sash around glass is advantageous in that the sash is ready to be incorporated in a window once the weld is completed. The alternative, which is a slower process, involves forming the sash first, inserting the glass, and sealing the glass in the sash. This results in an operation requiring two or more steps, which again increases the time for manufacture of the product. Thus, there is a need for a process which incorporates the glass and welds the sash members in one quick operation. 
     There is also a need to quickly weld all types of corners found in the fenestration industry, including but not limited to, mitered corners, mortis and tenon joints, compound mitered corners and non-flush corners just to name a few. 
     These and other problems associated with the prior art are addressed by the present invention. 
     SUMMARY OF THE INVENTION 
     The invention provides a joint structure whereby the framing components may be securely joined by a vibratory method, which forms a joint structure having a strong weld with minimal flash in a very brief period of time. 
     In accordance with one aspect of the invention, a window is provided which includes a window glass assembly having interior and exterior sides; first, second, third and fourth members coupled to form a frame and a glass receiving channel formed between interior and exterior sides of the members for supporting the interior and exterior sides of the window glass assembly; and a joint structure formed by vibratory welding, thereby interconnecting adjacent ends of the members. The members can be any lineal members, of any length, but are preferably in the window and door industry. 
     The process known as vibratory welding occurs from an energy excitation source that operates to heat the mating surfaces to be joined, and generally only that portion of the surface to be joined. Such a system vibrates two or more surfaces against one another until a melt pool of material is formed, thus producing a weld. At this time, little further heating beyond the weld surfaces takes place. This results in heat without degradation of the adjacent areas around the weld. The weld pool thereafter allows for the two surfaces to be joined to create a strong weld with minimal weld flash and degradation. 
     The weld is preferably a corner or mitered weld. This &#34;off axis&#34; weld, meaning not a butt or 180° weld, is a particularly advantageous weld to achieve with the present invention. This off axis weld includes mitered welds, compound mitered welds, multi-planar welds wherein the welding surface has different planes, mortis and tenon joints as well as other welds or joints used in the window and door industry as well as other industries addressed herein. 
     The present invention minimizes the &#34;zone of disturbance&#34; around the weld. The &#34;zone of disturbance&#34; is the area around the weld where the orientation of the welded material differs from the orientation throughout the remaining portion of the welded part. The present invention has the advantage of having a smaller zone of disturbance, which results in a stronger weld and minimizes any unwanted reorientation of the parts material, which is fibrous. 
     An apparatus is also described and claimed which receives members and welds the corners using the vibratory methods described and claimed herein. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sash assembly. 
     FIG. 2 is a cross-sectional view of the profile of a rail sash member in the sash of FIG. 1, taking along line 2--2. 
     FIG. 3 is a side view of a typical member which is to be welded into a door or window part. 
     FIG. 4 is a perspective view of a vibrating platen consistent with the invention, showing the platen disposed between opposing stile and rail sash members prior to the vibratory welding operation. 
     FIG. 5 illustrates two experimental fixtures which each hold a member to be welded together. 
     FIG. 6 illustrates the fixtures of FIG. 5 with the members in place prior to welding. 
     FIG. 7 illustrates the experimental fixtures in a welding mode. 
     FIG. 8 illustrates the welded members with the bottom member removed from the bottom fixture and the top member still in the fixture. 
     FIG. 9 illustrates a schematic of an apparatus capable of welding a four member frame together. 
     FIG. 10 illustrates a schematic of an apparatus capable of welding a three member frame together. 
     FIG. 11 illustrates a cross-sectional view of a test profile. 
     FIG. 12 illustrates a cross-sectional view of a weld of two composite members, with the weld occurring with the use of hot plates. 
     FIG. 13 is a close-up view of the weld area shown in FIG. 12. 
     FIG. 14 is a cross-sectional view of a weld area using vibratory welding methods disclosed herein. 
     FIG. 15 is a close-up view of the weld area of FIG. 14. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention generally describes a vibratory method and apparatus to weld flowable members. This generally requires at least two members, which are to be joined, whereby at least one member is moved rapidly, at a frequency greater than about 50 Hz, preferably about 100 to 300 Hz, and most preferably about 150 to 250 Hz. This frequency of movement causes localized heating and flow of the member surface sealing faces, which allows the member to be welded to another member or surface sealing face. There is essentially no limit on the upper frequency value except the limitation encountered by the ability of the fixtures to vibrate at high frequencies. Thus, if an apparatus is built to achieve frequencies of about 1000 Hz or higher, this apparatus is also envisioned in the present invention. 
     The members to which the present invention is directed are preferably the components of windows and doors. Other areas of technology including the toy industry, the refrigerator and appliance industry, the building industry, picture industry, automotive industry and other industries assembling lineals may also benefit from the present invention and are envisioned herein. A typical window is shown in FIG. 1 as 10, with stiles 30 and 40, and rails 50 and 60. A mitered corner 15 is also shown. The glass 20 is shown in place. The mitered corner 15 is a type of weld envisioned by the present invention. Any number of sides may be welded from an arched member frame to a multi-sided window such as a pentagon could be welded. 
     The particular members to be welded can be a variety of materials. Although the method is preferably directed at thermoplastic members to be used in the manufacturing of window and door products, any flowable, thermoplastic material which needs to be welded could be used in the present invention. The present invention works well with thermoplastic polymers such as poly(vinyl chloride), low and high density polyethylene, polypropylene, poly(vinyl acetate), ABS polymers and any other polymers which are used in window and door parts. 
     The present invention also works well with thermoplastic composites. Typical composites which could be used include poly(vinyl chloride)/wood fiber composites such as those disclosed in U.S. Pat. No. 5,406,768, which is incorporated herein by reference. Composites which have thermally insulating materials such as wood have inherent problems with heat welding since heat transfer is slow. Thus, vibration welding, with the heat building up at the face of the weld, is particularly suited for composites which have thermal insulating properties. Composites including thermoplastic and non-flowable materials such as a thermoset material are also envisioned in the present invention. The present invention also works with a non-thermoplastic coated with a flowable material. The only requirement is there must exist some flowable material which can create the weld. 
     The usefulness of the present invention in the window industry is that the members used to assemble windows and doors often times have complicated profiles to accommodate the insertion of the glass, weather stripping, and opening within the dwelling in which the window or door is to be inserted. This complex profile is generally not a solid profile, but rather has many different cut surfaces, with oftentimes the majority of the cross-sectional space not having any material at all. The cross section is also complex, unlike a simple tube, and may have internal ribs or channels running through the member. FIGS. 2 and 3 disclose typical profiles. FIG. 2 shows a stile or rail 40, with an insulated glass unit 20 situated therein. The present invention allows welding to occur of these members, around the glass, which will be described below. 
     There are different methods envisioned to achieve a weld using the vibratory methods of the present invention. The first vibratory method involves vibrating at least one of the members. Referring to FIG. 3, member 50 could be vibrated while another member (not shown) could be held stationary, in a jig, with its face against face 54. (FIG. 4, without platen 70, shows two members in position to be welded as well). Preferably, the vibration would occur in a two dimensional direction, which is indicated by the direction of the arrows 55. Member 50 could be vibrated in the direction of arrow 55 at a frequency of about 200 Hz. This vibration would heat the sealing faces of both the members at which the vibration is occurring. Thus in FIG. 3, face 54 would be heated due to the friction created by another member&#39;s face vibrating against face 54. As the face 54 is heated up, a pool of the melted material would be created, which at this point, the vibrating member 50 would cease its vibration, whereupon the pool of material at the interface of each member would solidify, thereby creating a weld at the interface. 
     In another method, both members could be vibrated at a frequency, possibly to shorten the necessary weld time even further. Both members could be moved in the direction of arrows 55. The vibration frequency of both members would preferably be in a range of about 50 to 500 hz. 
     A third method envisioned involves a platen of some type interfacing between the two members. This is shown in FIG. 4, with a platen shown as 70. FIG. 4 shows platen 70 in a withdrawn mode, however, the mode of vibration is shown with platen 70 in phantom, between members 74 and 76. This platen 70 would be driven by an energy source 72 which would vibrate the platen 70 at a particular frequency, approximately 50 to 500 Hz, preferably about 100 to 300 and most preferably about 150 to 250. The preferred direction of vibration is in a back and forth motion, which is shown as arrow 78. This vibrating platen 70 could be in contact with each member&#39;s face 80 and 82, either simultaneously or in an alternative fashion, or some combination thereof, such that the faces 80 and 82 would be excited, thus creating flow of the face material. The platen 70 could just contact one member&#39;s face as well. As a pool of material is generated, faces 80 and 82 become liquid, the vibrating platen 70 would be withdrawn, and the members would be moved into an adjoining relationship. Thereafter, the liquid material at the interface between the faces 80 and 82 of members 74 and 76 would solidify resulting in a weld. The platen could also be heated and could be considered an improvement to hot plate welding whereby frictional heat aids the heating process. 
     The platen 70, preferably, has notch 86 cut into 70. This allows the vibratory weld to occur with the glass 84 in place. The platen 70 can move in and out, in the direction of arrow 78. The presence of the notch 86 prevents platen 70 from contacting and breaking glass 84. After faces 80 and 82 are conditioned to be pushed together to form a weld, members 74 and 76 are pushed together, with glass 84 residing in the groove of members 74 and 76. Thus, in manufacturing, a pane of glass is situated with two stiles and two rails surrounding the glass. The above welding occurs at the four interfaces, and the members are secured, with the glass glazed into place. 
     It has been found that the critical element in welding, the &#34;zone of disturbance&#34;, is much less in vibration welding than in hot plate welding. The &#34;zone of disturbance&#34; is the area around the weld wherein the material&#39;s orientation differs from that which was not exposed to the thermal stresses around the weld. More particularly, in the preferred embodiment of the present invention, a wood fiber/PVC composite is used. This composite material is described in U.S. Pat. Nos. 5,406,768, 5,441,801, and 5,486,553 and is incorporated herein by reference. This composite material has short wood fibers which are blended with a thermoplastic material such as polyvinyl chloride. The composition material is extruded or injection molded into a variety of shapes, preferably into members to be assembled into windows. Orientation of the fibers occurs during the extrusion and injection molding process, and typically such fibers are aligned at a 45° angle with respect to the weld line. This is evident in FIGS. 12-15. However, in the weld area, which is the zone of disturbance, it can be seen in FIGS. 12-15 that the fibers are oriented almost parallel to the weld line. This orientation occurs as the result of thermal disturbance which occurs at the interface of the weld. It has been shown by others that the fiber misalignment in the zone of disturbance decreases the modulus of the material. It has also been found that fiber misalignment results in undesirable thermal expansion or thermal shrinkage. 
     Thus, a narrower zone of disturbance is desirable thereby improving the properties of the welded product. Upon viewing FIGS. 12-15, it is apparent that the zone of disturbance is approximately five times larger with the heat weld as compared to the vibratory weld of the present invention. There is significant fiber realignment in the large zone of disturbance of the heat weld vis-a-vis the vibration welded product. 
     The magnification of FIGS. 12-15 are 14× for FIGS. 12 and 14 and 36× for FIGS. 13 and 15. The material used in the members shown in FIGS. 12-15 is a composite material described in U.S. Pat. Nos. 5,406,768, 5,441,801, and 5,486,553. The hot plate welding occurred according to the description in the &#34;Experimental&#34; portion of this application, under the heading &#34;Hot Plate Weld&#34;. 
     The vibratory welding occurred with identical parts, with the frequency of vibration being about 200 Hz, an amplitude of 0.035 inches and the duration of vibration being 3 seconds. The members were held together in a fixture at an indicated pressure of 6 psi on the machine. 
     Thereafter, the weld was sectioned to expose the welded material and weld area. The fibers visible are wood fibers, with a thermoplastic material encompassing the wood fibers in the matrix. (As is evident in FIGS. 14 and 15, there is an outer white surface which is a thermoplastic vinyl coating on the exterior surface of the right member.) 
     Preferably, the zone of disturbance is less than about 1500 microns wide. Thus, the zone of disturbance is approximately five times larger in the heat weld versus the vibratory weld. More preferably, the zone of disturbance is less than about 1000 microns wide. Most preferably, the zone of disturbance is approximately 500 microns in width, which results in an increased modulus for the welded members in the weld area, as well as minimizing thermoexpansion or contraction. Thus, the method of the present invention results in a weld having a &#34;minimized&#34; zone of disturbance and no thermal degradation which is defined as substantially no fiber misalignment in the area adjacent the weld area. The definition is meant to include any method, or parts which rely on vibration welding as the method to join the parts. 
     The preferred method of vibrating the members is shown in FIGS. 5-10. Generally, FIGS. 5-10 illustrate a preferred apparatus for practicing of the present invention. The figures depict a prototype and a schematic of a production apparatus which vibrates the members together, thus resulting in a weld. 
     FIGS. 5-8 illustrate a prototype design to achieve the benefits of the present invention. FIG. 5 illustrates two fixtures 102 and 104. Fixture 102 retains one member to be welded (not shown). Fixture 104 retains another member (not shown) to be welded. Fixtures 102 and 104 are shown without members, and show a variety of securing bolts with just a small portion of securing bolts generally referred to 102a, 102b, 104a and 104b. These retaining bolts retain the member in place. 
     FIG. 6 discloses the fixtures of FIG. 5 with members 106 and 108 in place. The members 106 and 108 are cut with mitered corners, and the faces are shown at 109 and 110. The members 106 and 108 were inserted into the fixtures 102 and 104 by loosening a variety of retaining bolts, some of which are shown as 102a and 102b and 104a and 104b. As is evident from FIG. 6, a very short portion of the members 106 and 108 extend from the fixtures 102 and 104. The small exposed portions minimize the flash which results from the weld. 
     FIG. 6 illustrates, with arrows 112 and 114, the direction of movement of the bottom fixture 104 in an upward direction, toward fixture 102. A second position is indicated by the dotted line 116 which is meant to indicate fixture 104 in a second position. This position is not the weld position, but is meant to show the travel direction toward a weld position for fixture 104. 110a shows the same face of 110 in a different position, being closer to face 108. 
     The fixtures 102 and 104 have vibratory heads located thereon. The vibratory heads used in the test fixtures shown in FIGS. 5-8 have an electromechanical vibrator assembly of 240 Hz, a dialable amplitude (stroke) with a feedback loop, an adjustable frequency, an Allen-Bradley SLC 500 Programmable Controller, a maximum part size of 24&#34; l×16&#34; w, an opening between platen of 16&#34;, a maximum clamp force of 2,200 lb., an overall machine dimension of 64&#34; w×36&#34; d×73&#34; h, an approximate weight of 4,000 lb., built-in forklift transport tubes, an interior work light, a 5 HP (2.7 kW) solid state power supply, power requirements of 480V AC, 15 amp, 3 phase, 60 Hz, and a minimum air pressure of 60 psi. 
     FIG. 7 illustrates fixtures 102 and 104 in their welding position with members 106 and 108 in contact. In this particular set-up, fixture 104 moves back and forth in the direction of arrows 118 to create a melt pool at faces 108 and 110. This movement in the direction of arrow 118 is the movement described in the experimental section which follows. Fixture 102 stays fixed as fixture 104 moves in the direction of arrow 118. 
     It appears that the ideal direction of movement is in the direction which maximizes continual contact between the faces. Turning back to FIG. 2, arrow 55 shows the preferred direction of movement. This direction results in the most interface contact during the welding process. If the direction were rotated 90°, as shown by arrow 57, the long faces shown generally as 41 and 45 of FIG. 2 would not be in contact for a long period of time. In other words, if one were welding a perfect circle, the direction of movement would be immaterial. However, if one were welding a long, thin, rectangular face, the direction of the vibration should be in the plane of the long sides of the rectangle to maximize contact during the weld process and minimize flash. 
     FIG. 8 discloses the final welded members, with member 108 secured to member 106. The member 108 has been removed from fixture 104. 
     A schematic of a welding apparatus is shown in FIGS. 9 and 10. In FIG. 9, members 120, 122, 124 and 126 are going to be secured together to form a window sash or window or door frame or other four-sided or multi-sided member used in windows and doors. Each member would be fixed in a fixture, and the vibrating heads 128, 132 and 134 are secured to the fixtures and vibrate that portion of the fixture to which the heads are attached. The fixtures are not shown in FIGS. 9 and 10, however, the fixtures utilized in FIGS. 5-8 could be used. Preferably, the fixtures would allow quick mounting and release of the members such that the assembly process is quick. 
     Preferably, the welding of four members occurs around the glass and is a two step process. Welds at faces 136 and 138 occur first. These faces are welded by initially moving members 120 and 124 in the direction of arrows 140 and 142 respectively. Some movement of members 122 and 126 in the direction of arrows 144 and 146 respectively may also occur such that the faces of the members are in contact. During vibration, the interfaces between members 120, 122, 124 and 126 are in contact with one another and shown as interfaces 136-139 respectively. After the members are brought together, initially, vibrating heads 128 and 132 are vibrated in the direction of arrows 128a and 132a. During this vibration, members 120 and 124 are fixed. This vibration of heads 128 and 132 welds the interfaces shown by arrows 136 and 138. After this welding has taken place, head 134 is vibrated in the direction of arrow 134a which welds interfaces shown by arrows 137 and 139. Thereafter, the welded frame is removed from the fixtures and four new members are inserted in the fixtures to be welded. 
     The two step process described above could be modified to be one step or additional step if desired. The preferred is described. 
     An important aspect during welding is that the interface between the members is vibrated away evenly across the full length of the weld. Vibration welding removes only about 0.02 to 0.06 inches from each interface wherein heat welding removes about 0.125 to 0.187 inches. The less interface removed, the better as it results in less flash. In looking at interface 136, there are two portions of the interface of member 120 identified as 148 and 150. Unless the direction from which the pressure is applied pushing members 120 and 122 is adjusted during the vibration welding, the face between portions 148 and 150 would not wear away evenly. To counteract this, the fixtures containing members 122 and 126 should have the pressure directed perpendicular to the face of the weld during the welding process. In this case, such an angle would be a 45° (as measured from the plane of member 122) angle pushing member 122 in the direction of arrow 152. This would ensure that the face of members 120 and 122 would wear away evenly. Such pressure would be simultaneously applied to member 126 during the welding step in the direction of arrow 154. Likewise, during the second step of welding, wherein faces 137 and 139 are welded, members 122 and 120 would be forced against members 124 and 126 in the direction of arrows 156 and 158 respectively. Such pressure would be applied by the fixtures simultaneously during the welding process. 
     FIG. 10 is a three-sided frame with members 160, 162 and 164. Vibrating heads 166 and 168 are moved simultaneously in the direction shown by arrows 166a and 168a. Such vibration occurs after member 160 has moved in the direction of arrow 170 and members 162 and 164 are moved in the direction of arrows 172 and 174 respectively. There is only a one step process of vibration for a three member frame. 
     The above descriptions for FIGS. 9 and 10 are an embodiment and the preferred embodiment at the present time. It is envisioned that other fixtures and vibrating head configurations could be utilized to achieve the welded window and door joints of the present invention. Further, the above can be modified to weld five member frames or other multimember frames. Thus, pentagons, hexagons, etc. may be produced. 
     The preferred angle of the mitered corner is 45 degrees, as shown in the figures. However, other angles are envisioned, from the welded members forming a lineal (180 degrees) or any other angle which results from the welding of two members. 
     The weld is preferably a corner or mitered weld. This &#34;off axis&#34; weld, meaning not a butt or 180° weld, is a particularly advantageous weld to achieve with the present invention. This off axis weld includes mitered welds, compound mitered welds, multi-planar welds wherein the welding surface has different planes, mortis and tenon joints as well as other welds or joints used in the window and door industry as well as other industries addressed herein. 
     An alternative method and apparatus in accordance with the present invention would be rather than vibrating the actual members, a third corner member is vibrated, which is in contact with the faces of the member. This third member would be some type of thermoplastic material which would become part of the finished welded article. In this embodiment, the long members would preferably be stationary, and the third corner member would be held in a fixture with a vibrating head in the third member&#39;s fixture. The vibration of the third member would heat up the face between the first member and the third member and the second member and the third member, thus resulting in a weld. 
     Yet another alternative method would employ the use of a center mullion which would be secured to the top and bottom rail of the window. The center mullion would divide the window configuration into two windows. In this method, the center mullion could vibrate in a horizontal plane, with pressure being applied to the top and bottom lineals, in the direction of the center mullion. This vibration process would secure the top and bottom rail to the center mullion, and the side stiles could be secured either during the attachment of the rail to the mullion or after. Additional mullions could be employed to produce a multi-paned window Thus, the present invention envisions multi-paned and multi-style rails and mullions to produce an infinite number of sizes and shapes of windows. 
     Yet another alternative method could include a multi-member joint or weld. This weld could employ, as a non-limiting example, a three member weld with a 120° angle between each weld. All three members could be moved simultaneously, or in some sequential fashion. 
     FIGS. 5-8 were the test fixtures used to generate the data in the experimental section which follows. 
     EXPERIMENTAL 
     FIGS. 5-8 detail an experimental fixture through which welded members were created. The material used in the experiment was FIBREX™, a composition of PVC and wood, manufactured by Andersen Corporation and, described in U.S. Pat. No. 5,406,768. The test method used to test the weld is described in detail in German Welding Society, Guidelines DVS2207, Part 25, published October 1989. These Guidelines describe welding thermoplastic plastics with heated tool butt welds. In particular, the testing of welded joints is described in paragraph 10 of these guidelines. The parameters and results of the welded components are as follows: 
     Heat Up Time 
     This is the time it takes to heat a test member from room temperature to its lowest welding temperature of above 240° C. 
     Cool Down Cycle 
     This is the time for the joined surfaces to cool below their melt point so that the bonded members have some bond strength. 
     Hot Plate Weld Time 
     This is the period during which the melted faces are brought together under pressure and held firmly. 
     A recommendation of the German Welding Institute suggests that the &#34;Heat Up Time&#34; is actually controlled mechanically by &#34;burning off&#34; 3 mm (0.120) of the profile before the surfaces are brought together. At their recommended minimum temperature of 245° C. this results in an approximate &#34;Heat Up Time&#34; of 15 seconds plus a &#34;Weld Cycle Time&#34; of 7 seconds and a &#34;Cooling Cycle Time&#34; of 25 seconds for a total of 47 seconds per cycle. 
     Rigid PVC fuses fully at approximately 204° C. At this temperature both primary and secondary fusion has taken place with no degradation of the material due to HCl generation. However, at higher temperatures, degradation does take place as evidenced by discoloration of flash at the joint. Higher temperatures can minimize the heat up/cool down period but with the risk of severe degradation and even inferior weld strengths. 
     Vibratory Welding 
     The proposed welded surfaces are vibrated--one against the other at a frequency of approximately 200 Hz. A combination of amplitude of the vibration, the time of the vibration and applied pressure combine to give a melt pool in the interface and results in a welded surface. This process has several advantages: 
     1) weld temperature never exceeds the melt temperature of the material being welded. 
     2) cycle times are fast (typically 2 to 4 seconds). 
     3) heating and cooling areas are very localized resulting in &#34;instant cooling&#34; (when compared to hot plate welding). 
     4) flash is very limited. 
     RESULTS 
     From the following results, it can be clearly seen that vibration welding is a superior process to hot plate welding. Tables 1-5 illustrate vibratory welding utilizing the profile shown in FIG. 11. The amplitude and weld time have been varied to determine the variation which occurs on the load at break. The frequency of the vibration was approximately 200 Hz for all examples in Tables 1-5. A summary follows Table 5. 
     
                       TABLE 1______________________________________Amplitude .030     .030    .030  .030   .030Weld Time 4 Secs   4 Secs  4 Secs                            4 Secs 4 SecsPressure  6 psi    6 psi   6 psi 6 psi  6 psiLoad at Break     585      565     580   570    595(Newtons)______________________________________ 
    
     
                       TABLE 2______________________________________Amplitude .035     .035    .035  .035   .035Weld Time 4 Secs   4 Secs  4 Secs                            4 Secs 4 SecsPressure  6 psi    6 psi   6 psi 6 psi  6 psiLoad at Break     635      580     590   605    635(Newtons)______________________________________ 
    
     
                       TABLE 3______________________________________Amplitude .040     .040    .040  .040   .040Weld Time 4 Secs   4 Secs  4 Secs                            4 Secs 4 SecsPressure  6 psi    6 psi   6 psi 6 psi  6 psiLoad at Break     600      580     550   595    570(Newtons)______________________________________ 
    
     
                       TABLE 4______________________________________Amplitude .040     .040    .040  .040   .040Weld Time 3.5 Secs 3.5 Secs                      3.5 Secs                            3.5 Secs                                   3.5 SecsPressure  6 psi    6 psi   6 psi 6 psi  6 psiLoad at Break     670      640     600   670    600(Newtons)______________________________________ 
    
     
                       TABLE 5______________________________________Amplitude .035     .035    .035  .035   .035Weld Time 4.5 Secs 4.5 Secs                      4.5 Secs                            4.5 Secs                                   4.5 SecsPressure  6 psi    6 psi   6 psi 6 psi  6 psiLoad at Break     615      695     665   640    605(Newtons)______________________________________Summary of Vibration Welding TABLE 5______________________________________       Max 695       Min 605       Ave 644       Std Dev 28.8______________________________________ 
    
     Table 6 details a hot plate weld, illustrating the prior art process, for the same profile as used in Tables 1-5. A summary of hot plate welding follows Table 6. 
     
                       TABLE 6______________________________________Hot Plate Weld______________________________________Hot Plate Weld Temp. 245° C.Weld Time       7 secondsCooling Time    35 secondsBurn Off        3 mm (.120&#34;) - 15 second average time           to achieve______________________________________Results(Newtons)______________________________________   Sample 1      525   Sample 2      555   Sample 3      540   Sample 4      640   Sample 5      590   Sample 6      605   Sample 7      580   Sample 8      585   Sample 9      565   Sample 10     570   Sample 11     575   Sample 12     605   Sample 13     490   Sample 14     595   Sample 15     615   Sample 16     620   Sample 17     565   Sample 18     570   Sample 19     575   Sample 20     605   Sample 21     490   Sample 22     595   Sample 23     615   Sample 24     620   Sample 25     630   Sample 26     535   Sample 27     600   Sample 28     580   Sample 29     545   Sample 30     555   Sample 31     565   Sample 32     495   Sample 33     590   Sample 34     585   Sample 35     525   Sample 36     585   Sample 37     565   Sample 38     535   Sample 39     545   Sample 40     580   Sample 41     565   Sample 42     570   Sample 43     575   Sample 44     630   Sample 45     535   Sample 46     600   Sample 47     590   Sample 48     585   Sample 49     525   Sample 50     605   Sample 51     490   Sample 52     595   Sample 53     615   Sample 54     620   Sample 55     580   Sample 56     545   Sample 57     555   Sample 58     565   Sample 59     495   Sample 60     585   Sample 61     565   Sample 62     535   Sample 63     545   Sample 64     580______________________________________ 
    
     Summary of Hot Plate Welding 
     Profile FIG. 11 
     Max 640 
     Min 490 
     Ave 571 
     Std Dev 28 
     Sash Profile--FIG. 2--Vibratory Weld 
     
                       TABLE 7______________________________________                 Pressure Load at BreakAmplitude    Weld Time    Indicated                          (Newtons)______________________________________.040     2.75 secs.   6 psi.   860.040     2.75 secs.   6 psi.   785.040     2.75 secs.   6 psi.   780.040     2.75 secs.   6 psi.   740.040     2.75 secs.   6 psi.   720.040     2.75 secs.   6 psi.   777.040     2.75 secs.   6 psi.   685.040     2.75 secs.   6 psi.   770.040     2.75 secs.   6 psi.   755.040     2.75 secs.   6 psi.   730______________________________________ 
    
     Sash Profile--FIG. 2 
     Hot Plate Weld 
     
                       TABLE 8______________________________________                               Load at BreakBurn Off   Weld Temp.             Hold Time Cool Time                               (Newtons)______________________________________3 mm.   245° C.             7 secs.   25 secs.                               6803 mm.   245° C.             7 secs.   25 secs.                               7103 mm.   245° C.             7 secs.   25 secs.                               6703 mm.   245° C.             7 secs.   25 secs.                               6203 mm.   245° C.             7 secs.   25 secs.                               6603 mm.   245° C.             7 secs.   25 secs.                               6503 mm.   245° C.             7 secs.   25 secs.                               6203 mm.   245° C.             7 secs.   25 secs.                               6703 mm.   245° C.             7 secs.   25 secs.                               6803 mm.   245° C.             7 secs.   25 secs.                               640______________________________________ 
    
     
                       TABLE 9______________________________________Summary of Load at Break for Vibrating Welding______________________________________       Mean 760       Max 860       Min 685       Std Dev 34______________________________________ 
    
     
                       TABLE 10______________________________________Summary of Load at Break for Hot Plate______________________________________       Mean 660       Max 710       Min 620       Std Dev 22______________________________________ 
    
     In both the first and second set of experiments, the load at break was higher for vibration welding than hot plate welding. Thus, a stronger weld results with a shorter weld time. The above experimental results support the patentability of the present invention. 
     As is evident from the above results, the present invention provides a weld which is stronger than a heat weld. In some situations, the weld can be as much as 20 percent stronger. The weld time for vibration welding is less than half that of a heat weld. Reducing the weld time in half is very significant in the production of fenestration products, which are manufactured in large quantities. As discussed earlier, often times millions of units a year have to be produced, and the shorter the weld time, fewer shifts are necessary to complete the manufacture of a specified number of units. Furthermore, the weld is superior in strength to any weld, thus indicating the numerous advantages of the present invention. 
     Therefore, it may be seen that the invention offers several advantages over conventional welding techniques. As one skilled in the art would appreciate the various modifications could be made to the invention without departing from the spirit and scope of the invention, the invention thus resides in the claims hereafter appended.