GB2376657A

GB2376657A - Window profile notching tool

Info

Publication number: GB2376657A
Application number: GB0204048A
Authority: GB
Inventors: Derek Robert Parsons
Original assignee: GTI KOMBIMATEC MACHINES Ltd
Current assignee: GTI KOMBIMATEC MACHINES Ltd
Priority date: 2001-06-21
Filing date: 2002-02-21
Publication date: 2002-12-24
Also published as: GB0115110D0; GB0204048D0; GB2376656A

Abstract

An apparatus, suitable for preparing two extruded plastics door or window profile comprises a tool, such as a circular saw, suitable for removing or relieving a notch of material from the profile or profiles. The apparatus further comprises a path with a guide, suitable for sliding at least one of the profiles into position to cooperate with the tool, a stop to control the depth of cutting of the notch, by butting against a portion of the profile, the path being at an acute angle to the cutting plane of the tool. The apparatus may further comprise a means for extracting swarf during the relieving process.

Description

Prenarinú' two extruded plastics door or window profiles This invention

relates to apparatus for preparing two extruded plastics door or window profiles for them to be thermally welded together. They may for example 5 form a mitred corner joint, or a joint between an end of one profile and a right-angled notch cut into an intermediate portion of another profile.

During the process of welding frame joints in extruded PVC window and door profiles, a flash or sprue is developed and this requires cleaning off. Neither manual nor machined cleaning has been totally successful, particularly where the profiles 10 have been produced to replicate traditional wooden window frames incorporating the so-called "ogee", "ovollo", and "bevel" moulded shapes, as illustrated in figure 1 of the accompanying drawings. Profiles are generally coloured white, but some imitate wood grain with a laminated skin and these also require cleaning and have proven to be more difficult to clean than unlaminated profiles.

15 During the thermal welding process, a predetermined length of profile is sacrificed by "burning off" or melting. The amount of flash or sprue is generally consistent and is set by the welding machine. Often, but not exclusively, the lengths of profile required to produce a frame are sawn say 6 mm longer than the finished frame needed. A hot-plate type welding machine melts back this excess length 20 which envelopes inside and outside the profile, and it is this sprue around the outside of the profile that actually requires cleaning.

The joints can either be mitred corners or notched transoms or mullions (intermediate frame bars).

It is possible to control the sprue with knife-type limiters manufactured from 25 aluminium and steel and designed to surround the profile. Removal of the sprue by hand or machine is still required, although it is easier once the sprue has been

limited in this way, but the tooling is expensive and cumbersome and the results remain inconsistent.

Accordingly, the purpose of the invention is to overcome or at least mitigate the problem of cleaning sprue in this context.

5 The present invention provides apparatus for preparing two extruded plastics door or window profiles, for them to be thermally welded together, comprising: a tool for removing part of a surface of at least one of the profiles so that a portion is relieved at the said surface to be welded; a path for sliding at least one of the profiles into position for the tool to 10 relieve the said surface; a relief depth stop arranged adjacent the tool at the end of the or each path so as to stop the motion of one or both of the profiles along its path towards the tool, by abutting against a region of its surface to be welded, which region is separate from the said part which is to be relieved, thereby to determine the depth of relief; 15 and a guide along the or each path for guiding the profile along the path; the path being at an acute angle to the plane of operation of the tool so as to allow the tool to relieve the profile surface at an acute angle to the length of the profile. As part of the invention, it was recognised that some particular moulding 20 areas are difficult to clean, and are critical as far as the appearance of the finished product is concerned. Further, it was recognised that sprue could be minimised over these specific difficult areas, whilst the remainder of the joint could be left unchanged so that its strength overall need not be affected adversely. Thus the invention is to allow for the expansion at the joint as a result of the burning off, and 25 compensate for this as precisely as possible by removing material locally prior to the welding process. This achieved by the relieving operation performed by the apparatus of the invention.

In order that the invention may be better understood, examples of conventional welding and of welding using the invention will now be described, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows six cross-sections through typical profile types with 5 decorative moulding, specifically the single bevel outer frame, single bevel "T" transom, single bevel "Z" transom, double bevel outer frame, ogee outer frame and ovollo outer frame; Figure 2 is a perspective view from above of the working area of a typical corner welder; 10 Figure 3 is a perspective view of the welder of figure 2, together with two profiles positioned for a mitre joint, and including the setting plate but omitting the clamps; Figure 4 shows the welder of figures 2 and 3, with the heater plate in position for melting the profiles; 15 Figure 5 corresponds to figure 4 and shows the welded profiles together with formed sprue; Figures 6A and 6B are end elevations of the heater plate of figure 4 together with the profiles, figure 6A showing the profiles in contact with the heater plate just before melt begins, and figure 6B showing them at the end of the melt, showing 20 areas where sprue has formed; Figures 7A and 7B are views corresponding respectively to figures 6A and 6B but with part of the end of each profile having been relieved using apparatus embodying the invention; Figures 8A, 8B,9A and 9B are different views of one end of a profile held 25 adjacent a saw blade for cutting the relief in accordance with the invention; Figures 10A and 10B are views corresponding respectively to figures 8B and 8A illustrating the relieved end edges, or relieved portions, prior to welding;

Figure 11 is a perspective view of apparatus embodying the invention, comprising a saw for cutting relief in profiles using the saw blade of figures 8A, 8B, 9A and 9B; Figure 12 is a plan view of the saw of figure 11, showing the positions of two 5 profiles intended for a mitred joint; Figure 13 is a view of the saw of figure 11 together with a notched profile; Figure 14 is a plan view corresponding to figures 12 and 13, showing two profiles cut with "arrow heads"; Figure 15 is a perspective view of a typical Z transom to reverse butt frame 10 welded joint; Figure 16 is a perspective view of modified apparatus embodying the invention; Figure 17 is an enlarged perspective view of the saw of Figure 16; and Figure 18 is an enlarged perspective view of the guide assembly of Figure 15 16.

Some typical window and door profiles are illustrated in cross-section in figure 1. These are hollow bars of extruded PVC (polyvinyl chloride) which are typically coloured white but may also be laminated with for example a wood grain effect. Typical dimensions are illustrated. The areas of the mould which are difficult 20 to clean of sprue after thermal welding are illustrated by being encircled in figure 1, and it is these portions which are relieved in accordance with the invention, as will be described below.

The working area of a typical corner welder is shown in figure 2; this example is a single head welder, but a multi-head welder would be capable of 25 welding more than one joint at a time. Left and right fences are mounted on left and right tables respectively, and left and right clamps are closed over the fences.

Upper and lower sprue restriction knives are shown on the working edges of the

clamps and tables as shown, in order to reduce the amount of sprue remaining on the joint after it has been welded.

The conventional process for forming a mitred joint comprises sawing the profiles at 45 degrees to produce mitred profiles, with an excess length of typically 6 5 mm to allow for burning off. These profiles are positioned against the left and right fences as shown in figure 3, and their cut ends are made to abut against a setting plate which bisects the right-angle between the profiles. As shown in figure 4, the setting plate is removed and is replaced by a heater plate inserted between the sawn faces of the profiles. The tables close, pressing the profiles against the heater 1 0 plate.

The heater plate is then withdrawn and, as shown in figure 5, the profiles are slid further and are pressed together to form the thermal joint. As shown in figure 5, external sprue is formed around the thermal joint.

Figure 6A is a side elevation showing the end edge of the heater plate and 15 the ends of the profiles, immediately prior to welding. Figure 6B shows how the sprue 61 is formed as the profiles are pushed against the heater plate and part of the length of each profile is sacrificed by burning off. An example of the use of the invention is illustrated in figures 7A and 7B, which show that a portion of the end of each profile, after it has been cut to shape, is further cut (or otherwise formed), to 20 produce a relieved section as shown. The relief is formed normal to the plane of the pre-cut surface to be welded, although it is not essential for the portion removed to be exactly rectangular- so long as the same end result is achieved, namely minimising the material at that region. By reducing the amount of plastics material at this section, less sprue is generated as the profile is sacrificed during welding. As 25 illustrated in figure 7B, the major part of the end section generates the full amount of sprue, whereas the relieved section generates a minimum amount of sprue. The

area of relief is predetermined to give the minimum amount of sprue, for a given predetermined length of sacrificial burning.

This relieving operation is achieved by sawing just the predetermined portion of the previously-cut end of the profile, as shown from different views in figures 8A, 5 8B, 9A and 9B. An alternative tool would be a milling or grinding tool. In this example, the relieving is carried out on a bar cut at 45 degrees, but corresponding relieving is intended to be carried out on selective portions of, for example, a right-

angle notch cut into an intermediate portion of a bar, or over one angled surface of an arrowhead shaped end.

10 The resulting relieved surface is shown in figure 10A, which corresponds to figure 8B, and in figure 10B which corresponds to figure 8A. The relief is cut normally into the cut end surface of the profile, so that it extends in the direction in which the profile is to be melted and sacrificed. Thus the relief may typically be at 45 degrees to the length of the profile. The depth of relief is adjustable to suit 15 various different welder burn off settings, and one example for a mitred corner would be a depth of 1.6 mm for a 6 mm burn off. This means that part of the end face of each profile, which is cut at 45 degrees to its length, is relieved by 1.6mm normal to the plane of the end face. When the faces are welded, each profile burns back a length of 3mm along its length, i.e. 3 x cos 45 = 2.1mm normal to the plane of the 20 end face, making a total burn off of 3 + 3 = 6mm. The depth of relief may typically vary between 0.5 mm and 3 mm, and typically it is about one quarter of the length of intended burn off. A preferred range of depth of relief would be from 0.1 to 0.4 times the length of burn off. The burn off length is easiest to measure linearly along the profile's length, so for example a measurement of 6 mm for a 45 end would instead 25 be 4.2 mm for a 90 end.

A machine embodying the invention for cutting the relief in profiles is shown in Figure 11 in perspective view, and comprises fixed locating fences at right-angles

to each other, adjacent a saw blade. These define paths for sliding the profiles to the saw, and each is at an acute angle to the plane of operation of the saw, i.e. to the saw blade. Adjustable guides are affixed on either side, to support the profiles.

A plate is inserted and clamped adjacent the saw blade and parallel to it, to act as a 5 relief depth stop, to control the amount of relief cut into the exposed end surfaces of the pre-cut profiles. The relief depth stop is disposed symmetrically between the paths and is common to both paths.

This machine of Figure 11 is shown in use, in plan view, in Figure 12, with left and right hand profiles abutting against the relief depth stop, and the saw blade 10 cutting a relief into just a portion of the end surfaces of the profiles, simultaneously.

The part of the surface of each profile which abuts the stop is separate from the relieved part. An alternative use is shown in figure 13, in which a previously notched profile is given a relief cut over a portion of one side of the notch. The other side of the notch would be similarly treated by turning the profile through a right 15 angle and using the other side of the machine.

A further example is shown in figure 14, in which two profiles, pre-cut with arrowheads, are simultaneously given relief cuts over a portion of one side or both sides of the arrowhead. It is also possible to work a notched profile and an arrow headed profile at the same time.

20 A joint comprising of an arrowhead and a notched cut is made to create a dividing bar in a window or door and is generally known as a transom or mullion or midrail. A typical Z transom, welded to a reverse butt frame, is shown in figure 15. In this example, the Z transom was given an arrowhead cut, both surfaces of which 25 were given relief cuts over the portions illustrated by circles in figure 1. The abutting portions of the other frame member were also given relief cuts, prior to welding.

In the process illustrated with reference to figure 11, the profiles need to be pre-cut using a different saw (not shown). They are then given the relief cuts, and then moved to a welding machine such as that shown in figure 2. Alternative processes which are intended to be more efficient are also envisaged.

5 In one example, the relief cuts are made immediately following the sawing of the profiles to length, or the V-notching of the profiles. Using an independently driven milling, sawing or grinding unit, corresponding to the saw blade of figure 11, and fitted to the main sawing machine which is used for shaping the profiles, the relief cuts can be given whilst the profile or profiles remain clamped in position, 10 immediately following their sawing to length or V-notching. Thus one milling, sawing or grinding unit is fitted for each main sawing machine saw blade.

In an alternative arrangement, the relief cuts are made immediately before the profiles are welded together. Using an independently-driven milling, sawing or grinding unit, similar to the saw blade of figure 11, and fitted to a welding head 15 corresponding to that of figure 2, the relief cutting operates immediately after the profiles have been inserted into the welding machine and clamped, but immediately before the welding process begins. It is envisaged that one such relief-cutting unit would be provided per corner joint, and two such units per transom joint. A vacuum extraction unit would be fitted to the same machine, for removal of the swarf after 20 the relief cutting and prior to the welding.

An alternative to the apparatus of Figure 11 is shown in Figures 16 to 18.

The table 10 supports a saw unit 11 which is of conventional construction. A pair of hydraulic clamps 13,14 are mounted on elongate guides 15, 16 for the profiles, in an assembly 12. The saw unit may be drawn vertically in operation such 25 that the saw blade 19 projects through part of a slot 18 in the table to effect the relief cut. In this case, the common relief depth stop 17 is clamped between the inner end

r surfaces of the guides 15, 16, instead of being on the opposite side of the saw as in Figure 1 1.

The position of the guides relative to the saw is adjustable to determine the extent of relief over the surface, i.e. the size of the area of the profile end surface 5 which is relieved. The depth of relief is predetermined by the thickness of the depth stop 17, but the depth of relief can also be adjusted by moving apart the guides 15, 16 and separating the two halves of the depth stop 17.

Claims

1. Apparatus for preparing two extruded plastics door or window profiles, for them to be thermally welded together, comprising: a tool for removing part of a surface of at least one of the profiles so that a 5 portion is relieved at the said surface to be welded; a path for sliding at least one of the profiles into position for the tool to relieve the said surface; a relief depth stop arranged adjacent the tool at the end of the or each path so as to stop the motion of one or both of the profiles along its path towards the tool, 10 by abutting against a region of its surface to be welded, which region is separate from the said part which is to be relieved, thereby to determine the depth of relief; and a guide along the or each path for guiding the profile along the path; the path being at an acute angle to the plane of operation of the tool so as to allow the tool to relieve the profile surface at an acute angle to the length of the 1 5 profile.

2. Apparatus according to Claim 1, in which the position of the guide relative to

the tool is adjustable to determine the extent of relief over the surface.

3. Apparatus according to Claim 1 or 2, in which the tool is a circular saw.

4. Apparatus according to any of Claims 1 to 3, comprising means for 20 extracting swarf produced during the relieving operation.

5. Apparatus according to any preceding claim, in which there are two such paths, on opposite sides of the tool.

6. Apparatus according to any preceding claim, in which the relief depth stop is positioned symmetrically between the paths, to act as a common relief depth stop 25 for both paths.

7. Apparatus for preparing two plastics profiles, substantially as described herein with reference to Figures 11 to 18 of the accompanying drawings.

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