PVC window frame and sash are sealed by lap, and the lap part of the fan and frame is called the overlap amount. The PVC window industry standard does not provide for the amount of overlap. For casement Windows, the amount of lap is generally between 8-10mm. The overlap amount as far as possible to choose some larger if condition permitted. In this way, the sealing between the frame and sash can be ensured even if the overlap position is slightly misaligned during installation and use. Different hardware is also a factor affecting the amount of lap. The lap of the frame and the sash can be chosen to be larger if the ordinary handle is used. A certain gap between the frame sash is required to install the transmission if the transmission handle is used. So amount of overlap must be small. Otherwise, the actuator installed on the sash is easy to collide with the window frame and affect the switch of the window sash. Therefore the amount of lap should be determined separately even if the same profile is used. If the UPVC profile produced by DIMEX is used to produce casement Windows, the lap amount of casement Windows without transmission is set as 8mm, which is ignored by some enterprises.
For sliding Windows, let us take the common European profile as an example
The amount of lap is determined by the dimensions of sash ribs, sash grooves and pulleys. Usually convex ribs, groove size are 20-22mm (there are convex ribs size is greater than the concave tip ruler). The sash groove size minus the pulley height is the lap of the sash to the lower frame. The pulley height is generally 12mm and the lap quantity is 8-10mm. Industry standards require an even amount of overlap between frame and sash. Then the overlap between the sash and the upper frame is also 8-10mm. The amount of sash window lap affects the sealing, safety, installation and daily use of the window. Take the profile with the groove depth of 20mm as an example, when the pulley is 12mm high, the gap between the ribs of the fan and the frame (i.e. the slide) root is 12mm (20mm-8mm = 12mm). This gap is used for sash installation and removal. There is only a 4mm installation gap between the sash and the top of the lower frame rib when installing the window. Due to the size deviation of window frame and sash manufacturing, the straightness deviation of window frame installation, and the height variation of pulley used, the actual lap amount and installation clearance of the frame fan will change. When the overlap between the sash and the upper frame increases, the installation gap decreases, which will make the sash installation difficult. The friction between the window and the upper sealing block increases, resulting in the opening of the window sash; When the upper lap amount is reduced, the sealing performance will decrease. Too little lap will increase the risk of sliding Windows. Therefore, when the amount of overlap is determined, we should pay attention to the size change of the convex rib of the frame of the model steel profile used, the depth of the fan slot and the size of the pulley and the sealing block. The formulation of dimension tolerance window frame and sash and the formulation of production process should effectively control the amount of lap joint.