Spacer

Details Spacer Spacer

2000-08-18

2003-03-25

Loney, Donald J. (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C428S034000, C428S036910, C428S156000, C428S167000, C428S188000

Reexamination Certificate

active

06537629

ABSTRACT:

The present invention concerns a plastic spacer for insulating glass elements, wall panels or similar objects. Such spacers are used, for example, to keep the glass sheets in an insulating glass pane parallel to each other and, combined with sealant, seal the area formed between the glass sheets at its edges and contain desiccant.
FIELD OF THE INVENTION
Spacers are frequently employed in the form of hollow metal profiles (stainless steel or aluminium). The profile has two parallel side walls in contact with the glass sheets and two legs extending between the side walls, which essentially run at right angles to the side walls of the hollow profile and join these to each other.
As far as their bonding properties with conventional sealants and sealing against water vapour penetrating the area between the sheets from outside are concerned, they meet the requirements. Nevertheless, the heat flow at the sheet edges, depending on the metallic materials, is excessive. Even if the area between the sheets is filled with inert gases such as e.g. xenon or krypton, a serious loss in insulation quality is observed, particularly in the boundary area set into the window or facade frames.
BACKGROUND OF THE INVENTION
Proposals to use plastic instead of metallic materials, as specified in DE-A-3302 659. DE-A-127 739, EP-A-0 430 889 and EP-A-0601 488 naturally produced an improvement in relation to heat insulation in the boundary area of the insulating glass element.
By doing this, however, serious problems characteristic of plastic result concerning:
the inadequate longitudinal stiffness and straightness of a plastic spacer compared with one produced from metallic material, which leads to considerably higher production cost and waste during manufacture; this problem can be countered to an extent by increasing the wall thicknesses of the profile. However, the result then is:
excessive heat transfer across the relatively large plastic wall thicknesses; and
increased production costs as a result of the higher material consumption.
OBJECTS OF THE INVENTION
The purpose of the present invention is to supply a common solution to the conflicting problems mentioned above using spacers made with a plastic base.
SUMMARY
The invention purports to solve the problem in the spacers initially described by choosing the ratio of the thickness of the legs to the thickness of the side walls as 0.8 or less and/or the thermal resistance in the legs to be higher than that in the side walls.
Limiting the thickness ratio of the legs and side walls to 0.8 or less gives more freedom to improve longitudinal stiffness by increasing the wall thickness or the side wall thickness while simultaneously limiting the thickness of the legs to the dimensions required for transverse stability of the hollow profile, thus limiting heat transfer at right angles to the length of the profile from one side wall to the other to a minimum.
The choice of a higher thermal resistance in the legs provides reduced heat transfer at right angles to the length of the profile (in the leg level). As the legs form a limiting factor for heat transfer performance, it is now possible to plan and implement reinforcement of the plastic in the side walls with a view to improving longitudinal stiffness, in the main independent of heat transfer considerations. Therefore it is possible to use plastic/reinforcing material combinations, which must provide an optimum in relation to their joining properties, especially bonding between synthetic and reinforcing materials, together with improved mechanical properties, regardless of their influence on heat conducting capability.
The principle of construction of the spacer as specified in the invention makes the longitudinal stiffness required to handle hollow profiles during the production of insulating glass elements feasible due to the freedom to increase the thickness of the side walls, while still providing the advantage of reduced heat transfer associated with plastic and, moreover, the latter can be minimised due to the comparatively thin construction of the legs.
The side wall thickness of a hollow profile in a 20 mm wide spacer is e.g. 3 mm or less for preference.
The choice of wall thickness ratio and/or reinforcement of the plastic increases the longitudinal stiffness, preferably so that the profile in the level of the side walls bends at most by about 100 mm/m of profile length. This saves nugatory expenditure as the conventional devices in metallic spacers can be used.
In addition, the transverse stability required for the hollow profile is the principal determinant for the thickness of the legs, i.e. the capability of the profile to support and retain both glass sheets of the insulating glass element at a defined spacing, even if wind forces acting on the sheets product tensile and/or pressure loading.
Surprisingly, it became apparent at the same time that, as a result of the lower wall thickness of the legs, together with the elasticity properties inherent in plastic, the hollow profile acquires a capacity to adapt in the transverse direction, which allows it to match its cross section at least partially to distortion of the glass sheets (the effect of wind forces). In addition, the legs permit elastic elongation or compression in the transverse direction, so that the position of the side walls of the profile can at least partially follow the distortion or bending of the glass sheets.
This has the effect of lowering the demands on the sealing components placed between the spacer and the glass sheets considerably when the glass sheets are subjected to tension and pressure, which is not only good for the long term stability of the sealing components themselves, but also noticeably counteracts separation tendencies in the glass/sealing component and sealing component/spacer boundary areas.
Limiting the thickness ratio to about 0.6 or less, or even to 0.4 or less, provides a further decrease in heat transfer, thus achieving or simultaneously improving on the abovementioned additional benefits.
It is possible to reduce the thickness of the side walls and, above all, the legs, by arranging one or more links inside the cavity parallel to the side walls, and still maintain comparable longitudinal stiffness. It is possible to form these links extending, in the main, across the entire height of the hollow profile and, in this way, join both legs to each other. Alternatively, the links can also form ribs running along the profile, with an edge standing proud of a leg.
The plastic can be reinforced to minimise wall thickness further, while maintaining or even increasing rigidity, in particular the longitudinal stiffness as well.
In addition, the proportion of reinforcing material in the plastic of the side walls will be higher than that in the legs. This measure is particularly relevant considering that numerous preferred reinforcing materials have a higher specific thermal conductivity than the plastic itself. By reinforcing the plastic in the legs as well, it is possible to reduce their thickness further, though by doing this, in the light of the effect this has on the thermal conductivity of the hollow profile, it is not possible to increase the proportion of reinforcing material arbitrarily. With respect to the thermal conductivity of the plastic, it is beneficial to seek an optimum ratio between reinforcing materials and costs.
With regard to minimising the heat transfer properties of the legs, it is preferable to reinforce these only in part. In this connection, there is the option of reinforcing strip shaped areas running parallel to the profile length, maintaining separation from the side walls and the legs if these are present. This solution strengthens an area of the legs which is mechanically weaker and limits the heat transfer through the legs in another, by means of the non-reinforced areas of the legs adjoining the side walls and, if necessary, the links.
Reinforcing fibres are the first choice for reinforcing materials, preferably chosen from among glass fibres, carbon fibres, aramide fibres and/or n

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