Fire door comprising a steel frame and adhesively attached panels

Abstract

 A steel-structured door, comprising a door frame (10) of steel, a refractory thermal insulation (30), and a door panel (20) on each face of the door, making up an external side of the door, the door panel (20) being attached to the door frame (10) by means of a bonding agent (50).

Description

[0001] The invention relates to a steel-structured door, which comprises a door frame of steel, a refractory heat insulation, and a door panel on each face of the door, making up an external side of the door.

[0002] The invention relates also to a method of manufacturing a steel-structured door, which method comprises attaching to a door frame of steel on each side a door panel as a face for making up an external side of the door.

[0003] Steel-structured doors are typically used in projects, wherein the door is used for establishing a compartment stopping or retarding the spreading of fire in a building. Such typical projects include, among others, doors between stairwells used as emergency exit routes in shopping malls and office buildings and the rest of the business premises or other premises, doors between parking facilities and exit routes, and so on. Especially in public spaces, the rate of using a door can often be remarkably high, the door being thus subjected to numerous loading times throughout the day.

[0004] Known from the prior art is, among others, EP 1 207 239 A2, which deals with fireproof panels. The structure described in the cited publication includes a metal layer, adhesion means, a fire-resistant foam, a mechanical bonding element with adhesion means, and a fire-resistant foam with mechanical bonding elements.

[0005] One traditional way of manufacturing steel-structured doors, which doors match the official regulations regarding fire doors, is to construct the door from steel plate by bending and by welding the components to each other. Such doors require major investments in production, especially in terms of bending machines. Generally, the model of doors apt for such manufacturing process is relatively constant even in various sizes, so the question is about a large-scale bulk product manufacturing process. Another relevant aspect is the development of heat associated with welding. Particularly the door panel or face surface of a stainless-steel constructed door, constituting a façade of the door, makes a comparatively challenging welding project. This is because stainless steel has propensity to reshaping in response to the evolution of heat, perhaps even more propensity than other steel grades. Localized thermal expansion causes convexity, buckling incidents, and the like, which do not necessarily return to the original straight and flat surface. The welding-inflicted discoloration of material is not desirable, either.

[0006] It is true that these discolorations can be dispelled later with appropriate chemical treatments, but that means more working processes and manufacturing costs.

[0007] It is an objective of the invention to provide a steel-structured door capable of withstanding continuous use in public spaces, which door, when tested according to SFS-EN 1634-1 (confirmed on 2000-06-30), fulfils the qualifications required of a fire door for type approval. The type approval refers to: A section in the Finnish building code, entitled Doors, a Ministry of the Environment statute of October 22, 2007 regarding type approval of doors, the EI class fire door of metal. Another objective of the invention is to provide a steel-structured door, which fulfils the quality criteria set therefor, regarding, among other things, straightness, appearance, finish, and durability, the door being still economically viable to manufacture and simple in terms of manufacturing technology, whereby the door structure makes its own contribution towards minimizing possible quality discrepancies in production. A still further objective is to provide a steel-structured door, which is as resistant as possible to vandalism and other possible unconventional use.

[0008] A yet further objective in a method according to the invention is to provide a straightforward, simple, and economically attractive way of manufacturing a steel-structured door. An objective according to one feature of the method is to provide such a door assembly process, by means of which the appearance changes of a door can be maintained at a minimum, i.e. the manufacturing-related stresses applied to the door panel do not result in a change of the door appearance. At the same time, this process step enables providing a fire-resistance upgrading structural detail regarding the construction of a door. This constitutes an objective, especially in cases where the exterior of a steel-structured door consists of stainless steel, which is not actually further coated, painted or similarly surface-treated in the finishing process.

[0009] What is characteristic of a steel-structured door according to the invention is that the door panel has been attached to the door frame by means of a bonding agent.

[0010] What is characteristic of a method according to the invention is that the door panel is attached to the door frame by the application of a bonding agent.

[0011] In the context of this invention, directions used in reference to the structure are as follows. The X-direction corresponds to a lengthwise dimension of the structure, which is hence for example the vertical direction of a door. The Y-direction corresponds to a lateral dimension of the door opening. Consequently, the XY-plane is essentially the same as the direction of the door plane. The Z-direction is a thickness or depth dimension. As this invention is particularly concerned with thermal engineering features of the structural elements, the Z-direction is generally also consistent with the direction of an installed structure's temperature gradient in a fire situation.

[0012] The invention will now be described in more detail with reference to the accompanying figures, in which figures:

fig. 1 shows a general view of a door structure,

fig. 2 shows one cross-section of a door in Z-direction,

fig. 3 shows one arrangement for ensuring the attachment of a door panel,

fig. 4 shows one preferred profile for a door frame.

[0013] Fig. 1 illustrates a door structure in a general view. A steel-structured door 1 of the invention comprises a door frame 10 of steel, a fireproof heat insulation 30, and a door panel 20 on each face of the door 1, making up a façade for the door and said door panel 20 being fixed to the door frame 10 by means of a bonding agent 50.

[0014] Fig. 2 illustrates one cross-section of a steel-structured door in Z-direction.

[0015] In the context of this invention, the bonding agent 50 represents such a material which is capable of forming an adhesion-based joint between the door panel 20 and the door frame 10. The bonding agent 50 includes plastics as its basic ingredient, thus providing a sufficient toughness and elasticity for the joint. Toughness, elasticity, and impact resistance are particularly desirable qualities for normal use of the door. The users often apply substantial forces to the door, especially if an optional door-mounted damper is out of order. The attachment of a door panel to a door frame must not start to crack or delaminate. On the other hand, there are no prior known proposals for providing a fire resistance, which is sufficient for obtaining a type approval for a door and which is implemented by means of a plastic-based adhesive bonding agent. Of course, such an extremely heat-resistant, plastic-based, adhesive bonding agent could be found for example in the attachments of ceramic tiles used in space shuttles or the like, but its price does not make economic sense in terms of manufacturing doors. In the context of this invention, it is an explicit objective to provide a structure which is economically as attractive as possible, yet fulfils the demands. Extensive studies associated with the invention have indicated that several polyurethane-based elastic bonding agents, such as glues or adhesive pastes, fulfill the demands set therefor both in terms of their technical features and price.

[0016] In one preferred embodiment of a method according to the invention, the bonding agent is applied as an undulating, such as a sine-wave shaped, continuous extrudate by means of a die onto the door frame or the door panel. After this, the elements to be connected to each other are placed precisely in a correct position and said elements are pressed together. A suitable amount and application geometry of bonding agent provide a sought-after final result. As a result of the compression, the undulating continuous extrudate or ribbon of a bonding agent turns into a flat film, which retains the door panel securely in place and seals the joint hermetically. By virtue of its undulating shape, the extrudate turns into a relatively consistent film as a result of flattening, whereby the number of air pockets or non-adhered spots can be minimized. About these undulating shapes, it should be noted that the sine-wave form is particularly beneficial as the air is able to discharge thoroughly from the joint and the wave form is mathematically simple to calculate, which in turn facilitates an automated application of the proper amount.

[0017] It has also been discovered that the film thickness bears an effect not only on the strength alone of a steel-structured door in normal use but also in a possible extreme situation, i.e. when fire resistance is called for. With a correct film thickness, the bonding agent admittedly becomes charred and turns brittle, yet is still able to hold the door panel fixed to the door frame. In the event of having too little bonding agent, it will lose its adhesiveness too quickly and, on the other hand, if there is too much bonding agent, it does not work as desired. Based on the studies, when the film thickness in a finished door is preferably within the range of 0,1-1 mm, more preferably 200-500 pm, the optimal end result shall be attained.

[0018] Furthermore, it can be noted from fig. 2 that the door frame 10 can be optionally constructed in a steel profile, wherein the propagation of heat in the Z-direction of a door is retarded by means of heat discontinuities 101. Such a highly appropriate heat discontinuity profile has been described in the same Patent Applicant's earlier utility model, application number FI-U 20060166 (the same patent family includes also DE-UM 202007005298.7). This is a particularly beneficial embodiment in a steel-structured fire door for the reason that the entire amount of heat, the transfer of which is successfully blocked from the on-fire side to the other, not-on-fire side of a door, retards the spreading of fire in a building and provides extra time for the fire brigade to extinguish the fire. In the heat discontinuity profile shown here (depicted in more detail in fig. 4), the transfer route of heat by conduction in the Z-direction has been disrupted, whereby the heat transferring by conduction is forced to travel a considerably longer distance in the X- or Y-direction for making it able to transfer in the Z-direction. Consequently, the heat spreading within the structure is not capable of crossing quickly from one side to the other. A refractory heat insulation inside the door can be preferably provided by using for example a highly appropriate fire protection insulation, such as mineral wool-based PAROC FPS 14, ISOVER PKOL or the like.

[0019] According to one method-related embodiment, the door manufacturing process comprises performing the following steps of:

• preparing the door frame 10 for the application of a bonding agent
• applying the bonding agent on a first side of the door frame 10 for attaching a first door panel 20,
• installing the first door panel 20 correctly against the door frame and pressing it in place for ensuring adherence of the bonding agent,
• installing a thermal insulation 30,
• applying the bonding agent on a second side of the door frame 10 for attaching a second door panel 20,
• installing the second door panel 20 correctly against the door frame and pressing it in place for ensuring adherence of a bonding agent 50. The door frame preparation process may include various process steps, such as, for example, fixing the door frame to a working tool, cleaning the surfaces, applying, heating or other handling a possible primer.

[0020] As an alternative to the presented frame-based assembly mode, it is possible to employ a manufacturing process based on stacking sequence, wherein the door is assembled by stacking directly in the final order. Thus, the first door panel 20 is placed on a working tool, a worktable or the like, the bonding agent 50 is applied to the door panel 20 in spots against which the door frame 10 settles, the door frame 10 is installed, the insulations 30 are installed, the bonding agent is applied on the door frame 10, the second door panel is placed on top of the door frame. This sequence may be slightly quicker than the above-described assembly sequence which requires a turnover of the frame but, on the other hand, it is slightly more difficult in this process to set the elements in precise alignment with each other by first attempt.

[0021] One way of constructing a door frame is, for example, such that elements like frame profiles, which make up the door frame 10, are assembled in a ring configuration and joined together, for example by welding X- and Y-directed frame profiles to each other. The door frame 10 can be constructed in the previously described step of the same process or can be acquired for example from a subcontractor.

[0022] Depicted in fig. 3 are a few preferred features of the invention. In a steel-structured door, the attachment of the door panel 20 to the door frame 10 is backed up mechanically at least along an upper edge of the door panel 20. Further, according to a preferred embodiment, the mechanical backup is provided by way of screws 40. In the context of this invention, the upper edge of a door refers to such a region of the door which, when the door has been assembled and installed in its working position, lies in the X-direction (vertical direction) within a top quarter of the door panel. Preferably, this upper edge is a zone even narrower than the quarter area, but the precise structure is determined according to the construction of a door frame.

[0023] In certain applications, the screws 40 can be left with their heads 42 exposed. However, according to one further developed embodiment, from the standpoint of the appearance and technical functionality of a door, a more preferred embodiment is such that the screws 40 for mechanical backup are made headless. This provides several benefits from the standpoint of a final result. In public spaces, the appearance of doors is almost without exception to provide information about the intended use thereof and to convey a certain image or impression about this particular location. Thus, the neatness and intactness of a door appearance are desirable qualities. In such spaces, the structures assembled by robust riveting, welding or by means of screws do not necessarily provide a desired final result, despite being potentially highly functional in technical sense. Welded structures, especially, are problematic as described earlier. According to one preferred embodiment of the invention, the method further comprises steps, in which the screw 40 is left protrusive in the screwing process, such that between the screw's head 42 and the door panel's 20 surface 21 is visible some of the screw's threaded portion 41 (as shown in fig. 3 to the left of the door frame 10), after which the screw 40 is cut off to the flushness with or along the plane of the door panel's 20 surface 21 (as shown in fig. 3 to the right of the door frame 10). Established this way is a highly inconspicuous mechanical backup for the attachment of a door panel, which nevertheless retains the door panel in position even under a major stress. The traditional "exposed head" screws constitute unfortunately often also a target of vandalism, but "tampering" with this type of virtually invisible screw backup of is difficult or impossible without special tools. Studies have shown that an adequate backup is achieved when the ratio between a selected pitch of the screw and a thickness of the door panel is approximately 1 or less than 1.

[0024] When studying such a door backed up as described above in terms of its behavior further than required by a standard relevant to fire test, it has been discovered that, at the time when the bonding agent finally fails, the door panel remains hanging in place the way of a curtain by its upper edge and protecting the remainder of the door structure. That is, the mechanical backup according to this additional feature provides an effect that the door panel exhibits hardly any warping but instead just hangs as a straight cover for the structure in response to gravity.

[0025] In principle, the presently described invention is applicable to projects other than those intended for fire door service and also to an aluminum-constructed door by substituting aluminum for the material of a door panel and a door frame. However, this option does not pass a fire test, which is specified in standard SFS-EN 1634-1 and which formed the foundation of the invention. One reason for this is that the melting point of aluminum is about 660°C (as compared to 1535° in steel), while temperatures applied in the fire test comply, as specified in standard SFS-EN 1363-1, with a temperature graph T = 345 log10(8t + 1) + 20, wherein T is the average temperature [°C] and t is time [min]. Thus, at 60 minutes, the temperature has already exceeded 950°C, which means that an aluminum-constructed door would already have melted on the fire-facing side

[0026] Reference numerals used in the figures:

1 steel-structured door

10 door frame

101 heat discontinuity

20 door panel

21 door panel's surface

30 thermal insulation

40 screw

41 screw's threaded portion

42 screw's head

50 bonding agent

Claims

1. A steel-structured door (1), which comprises a door frame (10) of steel, a refractory heat insulation (30), and a door panel (20) on each face of the door, making up an external side of the door, characterized in that the door panel (20) is attached to the door frame (10) by means of a bonding agent (50).

2. The door (1) according to claim 1, characterized in that the bonding agent (50) consists of a polyurethane-based elastic bonding agent, such as a glue or an adhesive paste.

3. The door (1) according to claim 1, characterized in that the door frame (10) is constructed from a steel section, wherein the propagation of heat in a Z-direction of the door is retarded by means of thermal discontinuities (101).

4. The door (1) according to claim 1, characterized in that the attachment of the door panel (20) to the door frame (10) has been secured mechanically, at least along a top edge of the door panel (20).

5. The door (1) according to claim 4, characterized in that the mechanical security is provided by means of screws (40).

6. The door (1) according to claim 4, characterized in that the screws (40) for mechanical security are provided as headless screws.

7. The door (1) according to claim 1, characterized in that the refractory thermal insulation (30) inside the door consists of a mineral-wool based fireproofing insulation.

8. A method of manufacturing a steel-structured door (1), which method comprises attaching to a door frame (10) of steel on each side a door panel (20) as a face for making up an external side of the door, characterized in that the door panel (20) is attached to the door frame (10) by the application of a bonding agent (50).

9. The method according to claim 8, characterized in that the bonding agent (50) is applied as an undulating, such as a sine-wave shaped, continuous extrudate by means of a die onto the door frame (10) or the door panel (20).

10. The method according to claim 8, characterized in that the bonding agent film thickness in a finished door is preferably within the range of 0,1-1 mm, more preferably between 200-500 µm.

11. The method according to claim 8, characterized in that the attachment of the door panel (20) to the door frame (10) is backed up mechanically, at least along a top edge of the door.

12. The method according to claim 11, characterized in that the mechanical backup is provided by using a screw (40).

13. The method according to claim 12, characterized in that the screw (40) is left protrusive in the screwing stage, such that between the screw's head (42) and the door panel's (20) surface (21) is visible some of the screw's threaded portion (41), after which the screw (40) is cut off to a flushness with the door panel's (20) surface (21).

14. The method according to claim 8, characterized in that the door manufacturing process comprises performing the following steps of:

- preparing the door frame 10 for the application of a bonding agent

- applying the bonding agent on a first side of the door frame (10) for attaching a first door panel (20),

- installing the first door panel (20) correctly against the door frame and pressing it in place for ensuring adherence of the bonding agent,

- installing a thermal insulation (30),

- applying the bonding agent on a second side of the door frame (10) for attaching a second door panel (20),

- installing the second door panel (20) correctly against the door frame and pressing it in place for ensuring adherence of the bonding agent.

15. The method according to claim 14, characterized in that the method further includes steps of:

- screwing the screw (40) or the screws (40) through a stratum formed by the door panel (20) and the bonding agent (50) into the door frame (10), such that between a head (42) of the screw and a surface (21) of the door panel (20) is visible some of the screw's threaded portion (41),

- cutting off the screw (40) in flushness with the door panel's surface (21).

Drawing