Direct local heating for a movable barrier element to prevent or mitigate ice build-up

Abstract

An entrance system (1) has a movable barrier element (40) positionable to close off and open up, respectively, a passage between different temperature zones. A direct heating arrangement (50) that comprises one or more heating elements (51) is provided in a vicinity of a surface of the movable barrier element (40). The direct heating arrangement (50) is configured for generating heat locally at one or more areas of the movable barrier element (40) susceptible of ice build-up, thereby preventing or mitigating such ice build-up.

Description

[0001] DIRECT LOCAL HEATING FOR A MOVABLE BARRIER ELEMENT TO PREVENT OR MITIGATE ICE BUILD-UP

[0002] TECHNICAL FIELD

[0003] The present invention generally relates to the field of entrance systems. More specifically, the present invention relates to the field of entrance systems comprising a movable barrier element positionable to close off and open up, respectively, a passage between different temperature zones. The present invention further relates to an accessory for retrofitting to an existing installation of such an entrance system, as well as to use of certain heating elements to prevent or mitigate ice build-up at local areas of a surface of a movable barrier element.

[0004] BACKGROUND

[0005] Entrance systems comprising movable barrier elements are frequently used in various different applications. Movable barrier elements are typically door members or window members and are typically motorized. A motorized door member may, for instance, be a sliding door member, swing door member, revolving door member, overhead sectional door member or roll-up door member, actuated by an automated door operator.

[0006] One common use of such a movable barrier element is to close off and open up, respectively, a passage between different temperature zones. A colder temperature zone is at one side of the movable barrier element, whereas a warmer temperature zone is at the other side. For instance, the colder temperature zone may be a freezer area for storing of food or other goods or articles that need to be kept at a sub-zero °C temperature, and the warmer temperature zone may be an adjacent indoor area at room temperature or a conditioned fridge area at around 5 °C. Alternatively, the colder temperature zone may, for instance, be an outdoor environment during winter or in (sub-) arctic environments.

[0007] In some such applications of entrance systems, the movable barrier element is a roll-up door. When using roll-up doors in cold environments, there is a known problem with ice build-up resulting from condensation of humidity in air from the warmer temperature zone. Local areas of the roll-up door, such as the lateral edge areas where elongated transmission elements (a.k.a. “zippers”) are located, are particularly susceptible of such ice build-up. The ice build-up may cause malfunction of the opening and closing or the roll-up door. At least as problematic is the risk of moisture expanding when freezing and causing breakage of seams or seals and material deterioration of the roll-up door.

[0008] The prevailing approach to deal with the ice problem involves manual intervention, by service personnel periodically removing any ice that has been built up. Attempts have been made to prevent ice build-up by using air blowers. While such equipment may do the work, it is bulky, noisy, typically requires integration with the entrance system already at the time of manufacture, and comes with a high energy consumption.

[0009] The present inventor has realized that there is room for improvements in this field, and that the improvements may be applied not just to entrance systems with rollup doors, but also with other types of movable barrier elements.

[0010] SUMMARY

[0011] An object of the present invention is therefore to provide an improved solution to the problem of handling the risk of aggregation of ice in certain areas of a movable barrier element in an entrance system.

[0012] Accordingly, a first aspect of the present invention is an entrance system comprising a movable barrier element positionable to close off and open up, respectively, a passage between different temperature zones. The entrance system has a direct heating arrangement comprising one or more heating elements provided in a vicinity of a surface of the movable barrier element. The direct heating arrangement is configured for generating heat locally at one or more areas of the movable barrier element susceptible of ice build-up, thereby preventing or mitigating such ice build-up.

[0013] The provision of such a direct heating arrangement to an entrance system with a movable barrier element will solve or at least mitigate one or more of the problems or drawbacks identified in the above, as will be even clearer from the following detailed description section and the drawings. It will preempt the need for periodic manual intervention, and it will represent a much more lenient and efficient solution, in terms of space, cost and energy consumption, than the use of air blowers. Generally, the movable barrier element may be any door member or window member in an installation which is at risk of suffering from problems caused by a cold bridge. The door member or window member is typically but not necessarily motorized (automated). A motorized door member may, for instance, be a sliding door member, swing door member, revolving door member, overhead sectional door member or rollup door member, actuated by an automated door operator.

[0014] Advantageously, the heating elements may be provided at or near lateral sides of the movable barrier element. To this end, the heating elements may advantageously be elongated and electrically driven. Such configuration of the heating elements make them well suited to be applied at the areas of the movable barrier element that are particularly susceptible of ice build-up. Accordingly, in some embodiments, the elongated and electrically driven heating elements are mounted to extend vertically along a portion of a frame structure that supports the movable barrier element and defines the passage between the different temperature zones.

[0015] Some embodiments further comprise an overhang flap of a durable flexible material being attached to the frame structure that supports the movable barrier element. The overhang flap is mounted to extend vertically along the aforementioned portion of the frame structure. The elongated and electrically driven heating elements are attached to an inside of the overhang flap, thereby creating a semi-closed space at at least one of the areas of the movable barrier element that are susceptible of ice build-up. Beneficially, the semi-closed space serves to contain heat generated by the elongated and electrically driven heating elements. This will improve the heating efficiency and thus allow use of low-power heating elements (for instance LED strips, as discussed below) to still generate sufficient heat to prevent or at least mitigate ice build-up. Moreover, retrofitting will be will facilitated, since the overhang flap with the heating elements (e g. LED strips) can be provided as accessories that can be easily mounted to an existing entrance system by attaching the overhang flap to the supporting frame structure of the movable barrier element. Alternatively, if the existing entrance system already contains such overhang flaps, the heating elements (e.g. LED strips) may be retrofitted by attaching them to the inside of each overhang flap by, for instance, adhesive or stitching. In further improved embodiments, the inside of the overhang flap is additionally provided with one or more wall elements extending in a direction transversal to the vertical extension of the overhang flap. Compartments are formed at either sides of each of the wall elements, accommodating respective one or more of the elongated and electrically driven heating elements. This arrangement is beneficial, since it will serve to restrict warm air heated by the heating elements from rising upwards towards ceiling level or above the top of the passage, as is otherwise customary physical behavior of warm air. In this context, “restrict” means counteract, reduce or delay such flow of heated warm air upwards.

[0016] As indicated above, the heating elements may be light emitting diode, LED, strips, each LED strip comprising a plurality of LEDs. This is advantageous, since LED strips are cheap and conveniently available. Also, they operate at a low energy consumption, yet enough to prevent or mitigate ice build-up, particularly when emitting infrared light. To this end, at least some of the light emitted by the LEDs of the LED strips is preferably in the infrared wavelength range. In alternative embodiments, at least some of the light emitted by the LEDs of the LED strips is in the visible wavelength range, typically in the red wavelength range. This will introduce the possibility for making additional use of the hearing elements for ambient lighting or visual signaling purposes.

[0017] Other types of heating elements than LED strips are however conceivable for use with the present invention, including but not limited to resistive wires.

[0018] In some embodiments, the movable barrier element is a roll-up door positionable between an extended end position and a wound-up end position to close off and open up, respectively, the passage between the different temperature zones. In a non-limiting sense, the present invention may thus be applied for a roll-up door that comprises a multi-layered curtain having one or more internal layers of insulating material at a central portion of the curtain, encapsulated by laminated external layers of a durable flexible material joined by seams at least at lateral sides of the curtain. The direct heating arrangement will then serve to mitigate or prevent deterioration of the seams as a result of moisture freezing and expanding.

[0019] In some of these embodiments, the vertical edges of roll-up door may be provided with first and second elongated transmission elements. Such embodiments of the entrance system may further comprise a drive mechanism coupled to the first and second elongated transmission elements for causing movement of the roll-up door between the extended end position and the wound-up end position. In such embodiments, the areas of the roll-up door that are susceptible of ice build-up will be at or near the first and second elongated transmission elements, such ice build-up effectively being prevented or mitigated thanks to the provision of the direct heating arrangement.

[0020] A second aspect of the present invention is an accessory for retrofitting to an existing installation of an entrance system that comprises a movable barrier element positionable to close off and open up, respectively, a passage between different temperature zones. The accessory comprises a direct heating arrangement having one or more elongated and electrically driven heating elements to be provided in a vicinity of a surface of the movable barrier element. The direct heating arrangement is configured for generating heat locally at one or more areas of the movable barrier element being susceptible of ice build-up, thereby preventing or mitigating such ice build-up.

[0021] Beneficially, the accessory may further comprise an overhang flap of a durable flexible material being attachable to a frame structure supporting the movable barrier element, such that the overhang flap will extend vertically along a portion of the frame structure. The elongated and electrically driven heating elements are attached to an inside of the overhang flap, thereby creating a semi-closed space at at least one of the areas of the movable barrier element being susceptible of ice build-up. The semi-closed space serves to contain heat generated by the elongated and electrically driven heating elements.

[0022] In some embodiments of the accessory, the elongated and electrically driven heating elements are selected from the group consisting of: LED strips comprising a plurality of LEDs, and resistive wires. The advantages of using LED strips or resistive wires have been explained above for the first aspect of the present invention.

[0023] A third aspect of the present invention is the use of one or more LED strips or resistive wires as a direct heating arrangement to prevent or mitigate ice build-up at local areas of a surface of a movable barrier element operable in a passage between different temperature zones. Again, the advantages of using LED strips or resistive wires have been explained above for the first aspect of the present invention. Embodiments of the second and third aspects of the present invention may have any or all of the features that have been referred to above for the first aspect of the present invention.

[0024] In summary, the provision of a direct heating arrangement as referred to above for the first to third aspects of the present invention will solve or at least mitigate one or more of the problems or drawbacks identified in the above, as will be clear from the following detailed description section and the drawings.

[0025] Embodiments of the invention are defined by the appended dependent claims and are further explained in the detailed description section as well as in the drawings.

[0026] It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. All terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [element, device, component, means, step, etc.]" are to be interpreted openly as referring to at least one instance of the element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Objects, features and advantages of embodiments of the invention will appear from the following detailed description, reference being made to the accompanying drawings.

[0029] Figure 1 is a schematic front and slightly perspective view of an entrance system comprising a roll-up door.

[0030] Figure 2 is a schematic perspective and fractioned partial view of a roll-up door of an entrance system.

[0031] Figure 3 is a schematic perspective and partial view of a roll-up door of an entrance system. Figure 4 is a schematic perspective and partial view of a roll-up door of an entrance system that includes a direct heating arrangement according to an embodiment of the present invention.

[0032] Figure 5 is a schematic sectional view of the roll-up door with the direct heating arrangement according to the embodiment shown in Figure 4.

[0033] Figure 6 is a schematic block diagram of a direct heating arrangement according to an embodiment of the present invention.

[0034] Figure 7 is a schematic block diagram of a direct heating arrangement generally according to the present invention.

[0035] Figure 8 is a schematic front view of an overhang flap, the inside of which carries elongated and electrically driven heating elements of the direct heating arrangement in one embodiment of the present invention.

[0036] Figure 9 is a schematic front view of an overhang flap, the inside of which carries elongated and electrically driven heating elements of the direct heating arrangement as well as transversal wall elements forming compartments to capture generated heat in a refined embodiment of the present invention.

[0037] Figure 10 is a schematic sectional view of the overhang flap shown in Figure 9.

[0038] DETAILED DESCRIPTION OF EMBODIMENTS

[0039] Embodiments of the invention will now be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

[0040] One exemplifying and non-limiting example of an entrance system 1 that comprises a movable barrier element in the form of a roll-up door 40 is shown in Figure 1. Details are shown in Figures 2 and 3. As can be understood from Figure 1, the roll-up door 40 is attached at a proximate end 40Pto a rolling drum 28, supported between a pair of brackets 23. The roll-up door 40 is provided between two side post covers 21 that defines a passage between different temperature zones. The roll-up door 40 is positionable between an extended end position and a wound-up end position to close off and open up, respectively, this passage. In the wound-up end position, the full roll-up door 40 or at least a substantial part thereof is wound up on the rolling drum 28, with a distal end 40a of the rolling door being positioned at or close to the rolling drum 28, thereby opening the passage between the side post covers 21. In the extended end position, the roll-up door 40 is essentially positioned as shown in Figure 1, i.e. fully wound off from the rolling drum 28 such that the distal end 40a of the rolling door makes contact with ground, thereby closing the passage between the side post covers 21.

[0041] As discussed in the background section of this document, the colder temperature zone may, for instance, be a freezer area for storing of food or other goods or articles that need to be kept at a low temperature, while the warmer temperature zone may be an adjacent indoor area at room temperature or a conditioned fridge area. Alternatively, the colder temperature zone may, for instance, be an outdoor environment during winter or in (sub-) arctic environments.

[0042] As explained in the background and summary sections, the present invention prevents or mitigates the problem of aggregation of ice in certain areas of a movable barrier element, in the present case the roll-up door 40, in the entrance system 1. To this end, the entrance system 1 is provided with a direct heating arrangement 50, an embodiment of which is schematically shown in Figure 6 and parts of which can also be seen in Figures 4 and 5. A generalized form of the direct heating arrangement 50 is seen in Figure 7, and beneficial embodiments thereof in Figures 8-10. The direct heating arrangement 50 comprises one or more heating elements 51 provided in a vicinity of a surface of the roll-up door 40. The direct heating arrangement 50 is configured for generating heat locally at one or more areas of the roll-up door 40 that are susceptible of ice build-up. The direct heating arrangement 50 thus prevents or mitigates such ice build-up. Details of the direct heating arrangement 50 will be presented later with reference in particular to Figures 6-10.

[0043] As can be seen in Figure 2, the disclosed embodiment of the roll-up door 40 comprises a multi-layered curtain having one or more internal layers 45 of insulating material at a central portion 41 of the curtain, encapsulated by laminated external layers 46 of a durable flexible material joined by vertical seams 47 at lateral sides 42 of the curtain. As is indicated in the drawing, there may also be horizontal seams 47 between panel sections of the roll-up door 40. The insulating material of the one or more internal layers 45 may, for instance, be polyurethane foam (PUF), polyisocyanurate (PIR) foam, fiberglass or mineral wool. The material of the external layers 46 may, for instance, be polyvinyl chloride (PVC), high-density polyethylene (HDPE) or thermoplastic olefin (TPO). Providing a direct heating arrangement 50 in accordance with the present invention will serve to mitigate or prevent deterioration of any or all of these seams as a result of moisture freezing and expanding.

[0044] As can be seen in Figures 2 and 3, the vertical edges of the roll-up door 40 are provided with first and second elongated transmission elements 43 (only one of which is shown in the drawing). In the disclosed embodiment, the first and second elongated transmission elements 43 are timing belts made of a suitable material, such as rubber, plastics or metal. In typical embodiments, the areas of the roll-up door 40 that are susceptible of ice build-up are at or near these first and second elongated transmission elements 43.

[0045] The entrance system 1 further comprises a drive mechanism coupled to the first and second elongated transmission elements 43 for causing movement 48, 49 of the roll-up door 40 between the extended end position and the wound-up end position. In Figure 3, arrow 48 indicates the direction in which the roll-up door 40 moves when winding up on the rolling drum 28 to ultimately arrive at the wound-up end position. Arrow 49 indicates the direction in which the roll-up door 40 moves when rewinding from the rolling drum 28 to ultimately arrive at the extended end position (as seen in Figure 1).

[0046] As seen in Figure 3, the drive mechanism for the roll-up door 40 comprises a driving drum 24 having a central shaft 25 and first and second gearwheels 26 at respective ends thereof for engagement with the first and second elongated transmission elements 43 at the lateral sides 42 of the roll-up door 40. To avoid any confusion, note that only one gearwheel 26 is shown in Figure 3 and that the driving drum 24 is not shown in Figure 1. As indicated schematically in Figure 6, the drive mechanism for the roll-up door 40 further comprises an electrical motor 64 coupled to the central shaft 25 of the driving drum 24. Reference will now be made to Figures 4-6. In advantageous embodiments, the direct heating arrangement 50 comprises one or more light emitting diode, LED, strips 51, wherein the LEDs of the LED strips 51 will constitute the heating elements 51 of the direct heating arrangement 50. In the advantageous embodiments, at least some of the light emitted by the LEDs of the LED strips 51 is in the infrared wavelength range. It is recalled that in other embodiments, at least some of the light emitted by the LEDs of the LED strips may be in the visible wavelength range, typically in the red wavelength range. This will introduce the possibility for making additional use of the heating elements for ambient lighting or visual signaling purposes In other words, inventive activity can be seen in the use of one or more LED strips as a direct heating arrangement to prevent or mitigate ice build-up at local areas of a surface of a movable barrier element operating in a passage between different temperature zones. It is however also recalled that other types of heating elements than LED strips may be used with the present invention, including but not limited to resistive wires.

[0047] In the embodiment shown in Figures 4 and 5, at each of the areas of the roll-up door 40 being susceptible of ice build-up, there is provided an overhang flap 56 of a durable flexible matenal. The overhang flap 56 is attached to a support structure, such as a wall 30, side post 20, side post cover 21 or insulation panel 10, for the roll-up door 40 and covers the heating elements 51 of the direct heating arrangement 50, i.e. the LEDs 52 of the LED strips 51. A semi-closed space 13 is thereby created that will contain the heat generated at the areas of the roll-up door 40 being susceptible of ice build-up. Preferably, the heating elements 51 of the direct heating arrangement 50 are attached to an inside of each overhang 56. To this end, the LED strips 51 may contain an adhesive layer on the rear side, facilitating attachment to the inside of each overhang 56 by adhesion. As an alternative, the LED strips 51 may be attached to the overhang 56 by stitching or similar ways of attachment. The overhang 56 may advantageously be made of the same or similar material as the outer layers 46 of the roll-up door 40.

[0048] An arrangement like this lends itself very well as an accessory for retrofitting to an existing installation of an entrance system that comprises a roll-up door.

[0049] With reference to Figure 6, the direct heating arrangement 50 according to the disclosed embodiment comprises the aforementioned LED strips 51. At least one LED strip 51 is attached at each lateral side of the roll-up door 40 (i.e., at the left-hand and right-hand vertical sides of the roll-up door 40 when looking at it from the front, like in Figure 1), as discussed above. Depending on the requirements of the particular entrance system 1, the environment in which it operates and the heat generation capabilities of the particular type of LED strip, multiple LED strips 51 may be attached at each lateral side to obtain a sufficiently reliable level of ice build-up prevention or mitigation. One of the advantages of using LEDs strips for the present invention is that LED strips are a simple, inexpensive and widely available type of product. The present invention is not restricted to any particular kind of LED strips. Rather, generally any kind of LED strips will do, as long as they produce sufficient heat for the purpose of the invention. Some exemplary and non-limiting vendors are Philips Hue, LIFX, Sylvania, LEDMO, HitLights, SuperBrightLEDs, Govee, BTF-LIGHTING, Environmental Lights, Adafruit Industries, SuperNight, HitLights, and InStyle LED.

[0050] Each LED strip 51 contains a connector 53. A current or voltage converter, such as a transformer, AC / DC converter or DC / DC converter, connects via a cable, as seen at 54, to the connector 53 and supplies electric power to the LEDs 52 of the LED strip 51. In the disclosed embodiment, the current or voltage converter is a 24 V transformer 55 (it may be, for instance, 48 V in other embodiments), which is connected to AC mains 66 (e.g. 230, 120, 220, 240 or 3x400 VAC, without limitation) via a junction box 60.

[0051] Conveniently, the transformer 55 is connected to the same junction box 60 that also connects, directly or indirectly, to a motor drive 62 for the motor 64 that runs the driving drum 24. Elements 60-64 may be part of a control cabinet of an automated door operator. By connecting the direct heating arrangement 50 to a power source 60, 66 that also drives the electrical motor 64, components are saved and retrofitting of the direct heating arrangement 50 to an existing entrance system installation is facilitated.

[0052] Reference is now made to Figures 7-10. While the detailed description above has been directed at Figures 1-6 with an entrance system having a movable barrier element specifically in the form of a roll-up door 40, it is emphasized that the movable barrier element may generally be any door member or window member in an installation which is at risk of suffering from problems caused by a cold bridge. Generally, the door member or window member is typically but not necessarily motorized (automated). A motorized door member may, for instance, be a sliding door member, swing door member, revolving door member, overhead sectional door member or roll-up door member, actuated by an automated door operator.

[0053] A general direct heating arrangement 50 for an entrance system according to the present invention is schematically illustrated in Figure 7. As will be understood from the discussions in preceding parts of this document, the direct heating arrangement 50 comprises one or more heating elements 51 provided in a vicinity of a surface of the movable barrier element 40. The direct heating arrangement 50 is configured for generating heat locally at one or more areas of the movable barrier element 40 susceptible of ice build-up, thereby preventing or mitigating such ice build-up. The heating elements 51 are preferably provided at or near lateral sides of the movable barrier element 40 and are preferably elongated and electrically driven by a power source 55. Preferably, the elongated and electrically driven heating elements 51 extend vertically along a portion of a frame structure that supports the movable barrier element 40 and defines a passage between different temperature zones.

[0054] Figure 8 is a schematic front view of an overhang flap 56, the inside of which carries the elongated and electrically driven heating elements 51 of the direct heating arrangement 50 according to one embodiment. The overhang flap 56 is preferably made of a durable flexible material being attached to the frame structure that supports the movable barrier element 40. The overhang flap 56 extends vertically along the aforementioned portion of the frame structure, wherein the elongated and electrically driven heating elements 51 are attached to an inside of the overhang flap 56. As previously mentioned already for the specific embodiment of Figures 1-6, the overhang flap 56 thereby creates a semi-closed space at at least one of the areas of the movable barrier element 40 susceptible of ice build-up. The semi-closed space will serve to contain heat generated by the elongated and electrically driven heating elements 51.

[0055] Figures 9 and 10 are schematic front and sectional views, respectively, of an overhang flap 56, the inside of which carries elongated and electrically driven heating elements 51 of the direct heating arrangement 50 according to another, refined embodiment. In this embodiment, the overhang flap 56 moreover comprises transversal wall elements 57 that form compartments 58 to capture generated heat. The wall elements 57 protrude essentially orthogonally from the inside of the overhang flap 56. The wall elements 57 extend in a direction transversal to the vertical extension of the overhang flap 56, with the compartments 58 being formed at either sides of each of the wall elements 57. As can be seen, the compartments 58 accommodate respective one or more of the elongated and electrically driven heating elements 51. Although not seen in the drawings, the wall elements 57 may contain openings (lead-throughs), through which the heating elements 51 may run from one compartment to the next. As previously mentioned, the provision of the wall elements 57 and compartments 58 will serve to restrict warm air heated by the heating elements 51 from rising upwards towards ceiling level or above the top of the passage. The wall elements 57 may be made of any suitable material, such as plastics, or even the same material as the overhang flap 56, and may be attached to the latter in any suitable way, including but not limited to adhesive, stitching or plastic welding. In some embodiments, the overhang flap 56 may be manufactured integrated with the wall elements 57.

[0056] As has been made clear from the foregoing description, there are several advantages with the present invention and its embodiments. For instance, less manual maintenance will be required, since ice buildup no longer needs to be removed manually. Also, a longer lifetime of the movable barrier element can be expected, since prevailing problems with moisture freezing and expanding (for instance, causing breakage of seams and detenoration of the material of the curtain of a movable barrier element in the form of a roll-up door), will be eliminated. Long-term operational stability of the drive mechanism of the movable barrier element can be expected, because build-up of ice on the elongated transmission elements is avoided. In turn, this means that less repairs can be expected. Moreover, the direct heating arrangement, preferably comprising LED strips, will mean less energy consumption than prevailing approaches, for instance those that use air blowers. A reduction in energy usage by as much as 75% can be expected, without limitation.

[0057] The invention has been described above in detail with reference to embodiments thereof. However, as is readily understood by those skilled in the art, other embodiments are equally possible within the scope of the present invention, as defined by the appended claims.

Claims

CLAIMS1. An entrance system (1) comprising a movable barrier element (40) positionable to close off and open up, respectively, a passage between different temperature zones, characterized by a direct heating arrangement (50) comprising one or more heating elements (51) provided in a vicinity of a surface of the movable barrier element (40), the direct heating arrangement (50) being configured for generating heat locally at one or more areas of the movable barrier element (40) susceptible of ice build-up, thereby preventing or mitigating such ice build-up.

2. The entrance system (1) as defined in claim 1, wherein the movable barrier element (40) is selected from the group consisting of a door member and a window member.

3. The entrance system (1) as defined in claim 1 or 2, wherein the door member (40) or window member is motorized.

4. The entrance system (1) as defined in any preceding claim, wherein the heating elements (51) are provided at or near lateral sides of the movable barrier element (40).

5. The entrance system (1) as defined in any preceding claim, wherein the heating elements (51) are elongated and electrically driven.

6. The entrance system (1) as defined in claim 5, wherein the elongated and electrically driven heating elements (51) extend vertically along a portion of a frame structure (10, 20, 21, 30) that supports said movable barrier element (40) and defines said passage between different temperature zones.

7. The entrance system (1) as defined in claim 6, further comprising an overhang flap (56) of a durable flexible material being attached to the frame structure(10, 20, 21, 30) supporting said movable barrier element (40), the overhang flap (56) extending vertically along said portion of said frame structure (10, 20, 21, 30), wherein the elongated and electrically driven heating elements (51) are attached to an inside of the overhang flap (56), thereby creating a semi-closed space (13) at at least one of said areas of the movable barrier element (40) being susceptible of ice build-up, the semiclosed space (13) serving to contain heat generated by the elongated and electrically driven heating elements (51).

8. The entrance system (1) as defined in claim 7, said inside of the overhang flap (56) further being provided with one or more wall elements (57) extending in a direction transversal to the vertical extension of the overhang flap (56), compartments (58) being formed at either sides of each of said wall elements (57), the compartments (58) accommodating respective one or more of the elongated and electrically driven heating elements (51) and serving to restrict rising heated air.

9. The entrance system (1) as defined in any preceding claim, wherein the heating elements (51) are light emitting diode, LED, strips (51) comprising a plurality of LEDs (52).

10. The entrance system (1) as defined in claim 9, wherein at least some of the light emitted by the LEDs (52) of the LED strips (51) is in the infrared wavelength range.

11. The entrance system (1) as defined in claim 9, wherein at least some of the light emitted by the LEDs (52) of the LED strips (51) is in the visible wavelength range.

12. The entrance system (1) as defined in any of claims 1-9, wherein the heating elements (51) are resistive wires.

13. The entrance system (1) as defined in any preceding claim, wherein the movable barrier element (40) is a roll-up door (40) positionable between an extended end position and a wound-up end position to close off and open up, respectively, saidpassage between different temperature zones, the roll-up door (40) comprising a multilayered curtain having one or more internal layers (45) of insulating material at a central portion (41) of the curtain encapsulated by laminated external layers (46) of a durable flexible material j oined by seams (47) at lateral sides (42) of the curtain, wherein the direct heating arrangement (50) serves to mitigate or prevent deterioration of the seams as a result of moisture freezing and expanding.

14. The entrance system (1) as defined in claim 13, wherein vertical edges of the roll-up door (40) are provided with first and second elongated transmission elements (43), the entrance system (1) further comprising a drive mechanism (24, 25, 26, 62, 64) coupled to the first and second elongated transmission elements (43) for causing movement (48, 49) of the roll-up door (40) between the extended end position and the wound-up end position, and wherein the areas of the roll-up door (40) being susceptible of ice build-up are at or near the first and second elongated transmission elements (43).

15. The entrance system (1) as defined in claim 14, the drive mechanism comprising a driving drum (24) having a central shaft (25) and first and second gearwheels (26) at respective ends thereof for engagement with the first and second elongated transmission elements (43) at the lateral sides (42) of the roll-up door (40), and an electrical motor (64) coupled to the central shaft (25) of the driving drum (24), wherein the direct heating arrangement (50) is driven by a power source (60, 66) which also drives the electrical motor (64).

16. An accessory for retrofitting to an existing installation of an entrance system (1) that comprises a movable barrier element (40) positionable to close off and open up, respectively, a passage between different temperature zones, the accessory comprising: a direct heating arrangement (50) comprising one or more elongated and electrically driven heating elements (51) to be provided in a vicinity of a surface of the movable barrier element (40), the direct heating arrangement (50) being configured for generating heat locally at one or more areas of the movable barrier element (40) susceptible of ice build-up, thereby preventing or mitigating such ice build-up.

17. The accessory as defined in claim 16, further comprising an overhang flap (56) of a durable flexible material being attachable to a frame structure (10, 20, 21, 30) supporting said movable barrier element (40), such that the overhang flap (56) will extend vertically along a portion of said frame structure (10, 20, 21, 30), wherein the elongated and electrically driven heating elements (51) are attached to an inside of the overhang flap (56), thereby creating a semi-closed space (13) at at least one of said areas of the movable barrier element (40) being susceptible of ice build-up, the semiclosed space (13) serving to contain heat generated by the elongated and electrically driven heating elements (51).

18. The accessory as defined in claim 16 or 17, wherein the elongated and electrically driven heating elements (51) are selected from the group consisting of: light emitting diode, LED, strips (51) comprising a plurality of LEDs (52); and resistive wires.

19. Use of one or more LED strips (51) or resistive wires as a direct heating arrangement (50) to prevent or mitigate ice build-up at local areas of a surface of a movable barrier element (40) operable in a passage between different temperature zones.

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