TECHNICAL AREA

The present application relates to a temperature guard device for guarding parts of locking systems and in particular locking members used for locking doors and other openable closing members that are used to gain and prevent access to compartments and in particular doors for vehicle containers that may be exposed to varying weather conditions with temperatures below zero degrees but also vehicle containers that may be cooled for transporting frozen goods.

BACKGROUND OF INVENTION

Different locking systems are used in many applications for preventing unauthorized access to compartments. Such compartments may for example be safes, cargo containers, semi-trailer, swap bodies, van compartments, truck compartments, just to mention a few. A conventional locking system for containers comprises vertical rods extending on an outside of a loading door. The vertical rods are arranged with horizontal locking bolts that fit into fixtures on the frame of the loading door. The locking system is operated by handles attached to the vertical rods, enabling a rotation of the vertical rods between a locking position to a resting position. In order to prevent unauthorized access to the container, padlocks are used for locking the handles, preventing rotation of the vertical rods and thereby opening of the doors. Another type of locking device used are universal locks with traditional lock cylinder and keys. Padlocks and the universal locks are easy to manipulate and there is no guarantee or proof that they are used at a dedicated container.

With the ever-increasing cargo shipment around the globe, often containing different types of goods targeted by thieves and thus goods that are tempting to steal, different solutions regarding trailer containers and their doors have been developed. The most basic are solutions where the handling of the trailer door handles are made more difficult, for instance by covering the area of the padlock or to mount a sturdy lockable bar that grips around the vertical rods of a door pair. These might reduce the risk of break-in, but they are bulky, heavy and generally not user-friendly. More recently, intelligent systems have been launched having ID-functions. One such system comprises a locking system that is attached to a door, in particular doors of containers and in particular truck and semi-trailer compartments. The locking system comprises a handle on the outside of the door. The handle controls a locking bolt placed on the inside of the door and extends towards and into a recess or passage in the floor or bottom of the trailer container that receives the locking bolt in a locking position. The handling of the handle is only permitted if a correct code is entered on a keypad. This type of locking system works quite well in most situations.

A truck container may be exposed to varying weather conditions and thus varying temperatures. Some of these containers are insulated and cooled for transporting goods that needs to be kept refrigerated, such as food stuff and pharma products, where the cold chain must be maintained. Many of these cooled containers are regularly cleaned, which is a requirement in particular if frozen food stuff is transported, requiring good hygienic conditions. For instance, after unloading of such goods, the interior of the containers is cleaned and usually pressurized hot water is used in order to remove ice that might have been built up during the transport, apart from the cleaning aspect. No anti-freeze products are used with the hot water during the cleaning. This means that water may enter the recess and surround the locking bolt of the locking system, which water may freeze to ice if the temperature is low enough, for instance when the container is cooled again after cleaning for handling new frozen goods. If this occurs, the locking bolt may be fixated in the recess by the ice that has expanded during freezing, whereby the locking system cannot be operated in order to open the door. It might then be necessary to cut off the locking bolt or use a certain amount of violence and brutal methods to open, whereby the locking system can no longer function as intended before the locking bolt has been replaced as a minor action if possible. Another problem may be that the water in the recess freezes and makes it impossible to enter a locking bolt in the recess for a locking action, thereby preventing a proper closing and locking of the doors of the container. This may be even more problematic if electro-mechanical locking systems are used where the often quite long locking bolt or bolts is/are operated by an electrical motor. The electro-mechanical system cannot know if there is ice in the recess and will try to force the end of the locking bolt into a locking position, with the result that the locking bolt might bend, rendering the locking system inoperable. Some systems have been developed for preventing freezing of locks. Document DE 102015 108039 discloses a motorized lock for a vehicle door wherein the feed lines to the motor are designed as a heating winding around a lock component. Thus, the feed lines have a dual function. The component with the winding is preferably placed inside a housing of a door lock. Another example is found in US 8,253,070 disclosing a padlock provided with heating windings surrounding a lock cylinder and the ends of a curved lock, placed inside a housing of the padlock. The heating windings are driven by a battery and may be activated by a button.

All these solutions are concentrated on heating components inside a lock and not the part of a locking system that creates the locking function, such as the locking bolt and the receiving elements. None of the existing solutions can ensure locking or opening functions at low temperatures below zero degrees caused by ice in the bolt hole. The costs in operations, apart from mentioning the costs for direct material as locks and container body, and the hassle when a trailer cannot be unloaded or loaded a long distance from home, are significant. Another issue that a frozen bolt hole causes is that the route planning for the driver will fail or be seriously delayed and the consequences are obvious.

Thus, there is a need for solutions preventing interacting locking components from being attached to each other by ice.

BRIEF DESCRIPTION OF INVENTION

The aim of the invention is to remedy the drawbacks of the state of the art technology in this technical field. This aim is obtained by a device comprising the features of the independent patent claim. Preferable embodiments form the subject of the dependent patent claims.

In the description of the invention, the wording cavity is used for defining a suitable space that can receive a locking bolt of a locking system. It is to be understood that cavity may comprise any recess, passage or opening that is designed and intended for the use of providing a locking action together with a suitable locking bolt. In this regard, the cavity may be formed by discrete components such as clamping halves that will engage with a locking bolt from two or more sides thereof. It is also feasible that these discrete components may be flexible and that the end of the locking bolt is provided with an enlargement. During movement of the locking bolt, the flexible components will allow passing of the enlargement and engage around the enlargement in a locking position. The end of the locking bolt may further be arranged with an element cooperating with an opening of a cavity such that the cavity is turned between a receiving position to an engaging and locking position around the element of the locking bolt.

Regarding a definition of locking bolt, it may include latches, bars, pins and all types of members that are capable of movably engaging with fixed structures for providing a locking action, and combinations of these as well as locking systems having a plurality of cooperating locking bolts such as espagnolettes and other transmissions such as in safe doors operating several locking bolts at the same time, which locking bolts may engage with fixed structures in different directions and may be moved from a resting position to a locking position. The movement may be performed by different means such as handles, transmissions and combinations thereof as well as by manually moving the locking bolt.

According to a main aspect of the invention, it comprises a temperature guard device for preventing build-up of ice for a locking system, wherein the locking system comprises a movable locking bolt. The device may comprise a cavity designed to receive the locking bolt in a locking position, a heat transmitter arranged in the cavity and a heat source arranged in contact with said heat transmitter. The heat source may be arranged and designed to be connected to a power source such that the heat transmitter is heated and the cavity is heated.

The device provides a solution for preventing any moist, liquid and in particular water that has entered the cavity for the locking bolt to freeze, thereby preventing the ice, which expands when water freezes, to jam or fixate the locking bolt inside the cavity. The risk of having a situation during difficult weather conditions or temperatures below zero degrees centigrade of a refrigerated compartment where a door provided with such a locking system cannot be opened is thus minimized. According to one aspect, the cavity may be formed in the heat transmitter. In that regard, the cavity may be formed by a number of discrete elements forming a heat transmitter. The heat transmitter then acts both as a receiving component for a locking bolt as well as for heating the cavity with the locking bolt in the locking position.

Further, the device may comprise a housing having a compartment with at least one opening, in which compartment said heat transmitter is placed, wherein the compartment and the heat transmitter form the cavity. The housing can then be inserted into a recess of a fixed structure and attached thereto.

According to a preferable design, the housing may be generally tubular, having a centre axis, and with the opening in one end of the housing and wherein the heat transmitter has a shape and dimensions that generally correspond to the cross- sectional shape and the dimensions of the interior of the tubular housing. Since most locking bolts move linearly from a retracted unlocked position to an extended locking position, a tubular design of the housing is preferable. Further, in order to provide the majority of the cavity with heat, the heat transmitter fills the interior of the tubular housing as seen in a cross-sectional view.

According to on feasible solution, the heat transmitter may be arranged with a central passage designed to receive the locking bolt in a locking position. With this design, the locking bolt enters both the housing and the heat transmitter. In this regard, the heat transmitter may further be designed with surface areas adjacent the inner surfaces of the locking bolt when in a locking position, wherein the surface areas are smaller than the total inner surface of the central passage.

As an alternative solution, the heat transmitter is arranged with a surface facing said opening, which surface is designed to be in contact with the locking bolt in a locking position. Flere, the locking bolt will enter the housing but not the heat transmitter. Instead, the locking bolt will be moved until it abuts the heat transmitter.

For any of the solutions, the heat transmitter may be designed with surface areas adjacent the inner surfaces of the tubular housing that are smaller than the total outer surface of the heat transmitter that is generally parallel with the centre axis. With this solution, the contact areas between the heat transmitter and the surrounding housing will be minimized, which is an advantage for example if the housing is made of a material that has inferior heat transferring properties. Moreover, since the housing may be attached to a fixed structure that has been cooled down due to surrounding temperatures, any transfer of cold from the housing to the heat transmitter is minimized.

Regarding the surface areas, they may be designed to extend generally parallel with the centre axis. This is an advantage for instance if the outer surface of the heat transmitter is machined with for example a shank end mill and the heat transmitter is formed from a solid rod. The heat transmitter may then be fixated at one end and the milling by the end shank mill is performed from the other end providing elongated grooves with the surface areas between the grooves. The heat transmitter may then be fixated at the machined end and the first end of the heat transmitter is milled. With such an operation, the grooves and the surface areas of the first and the second milling operation may be positioned offset in the circumferential direction.

As an alternative to placing the heat transmitter in a cavity or the heat transmitter forming the cavity for receiving a locking bolt, a heat transmitter may be arranged in a section of the locking bolt that enters a cavity in the locking position. This solution also provides the heating of the cavity as well as the locking bolt for preventing build up of ice.

According to a further aspect, the device may comprise a controller that in turn may comprise a temperature sensor and switching elements. The controller may then be arranged to activate the switching elements when a temperature detected by the temperature sensor is below a pre-set value and to de-activate the switching elements when a temperature detected by the temperature sensor is above a pre-set value. With this solution, the heating of the device is performed automatically in contrast to a manual operation or a constant heating process. The device is then only activated if for example a surrounding temperature approaches or is below zero degrees centigrade. Above this temperature range, the heat source is not active. In order to log the function and operation of the device, the controller may further comprise memory elements capable of storing detected temperatures. Further, if the device is used in conjunction with a vehicle, such as a freight truck or the like, the device may comprise connections to an electrical system of a vehicle. In any event, when the device is provided with a housing, the housing is preferably provided with a liquid drainage in order to further minimize the risk of any build-up of ice around the locking bolt.

The device may be incorporated in a system that may comprise a battery as power source. The battery may in this regard either work as solitary stand-alone unit or be working together with the electrical system of the vehicle. For instance, when the vehicle is used, power from its electrical system may be used to operate the device.

In addition, the system may comprise a charger that can charge its battery. The system may be extended further to comprise a photovoltaic cell. The photovoltaic cell may then be used to charge the battery, which is an advantage if the device is used for example in a trailer that can be disconnected from a truck. The device can then still operate via the battery, supported by the photovoltaic cell.

BRIEF DESCRIPTION OF DRAWINGS

In the following detailed description of the invention, reference will be made to the accompanying drawings, of which

Figs. 1a, 1b show schematic illustrations of a locking system utilizing the present invention,

Fig. 2 shows a side view of a device according to the application attached to a fixed structure,

Fig. 3 shows a perspective view of the device of Fig. 2 with a housing partly cut away in order to view the interior of the device,

Figs. 4-8 show different designs of a heat transmitter comprised in the device of Fig. 2, Fig. 9 schematically shows a vehicle provided with a system comprising the device of Fig. 2, and

Figs. 10-26 show different variants of the device with different designs and positions of the heat transmitter.

DETAILED DESCRIPTION OF THE INVENTION

The device according to the present invention is intended to be used with locking systems for doors and the like openable structures that allow or deny access to any type of compartments that may contain goods and items that need to be protected. The openable structures may comprise swing doors, sliding doors, folding doors, revolving doors, just to mention a few types. Figs. 1 a and 1 b schematically show such one example of a locking system 2 attached to a swing door 4, in turn pivotally attached to a door frame or post 5 of a compartment (not shown). The locking system 2 comprises a locking member in the form of a locking bolt 6 that is movable in the longitudinal direction between a retracted resting position and an extended locking position. In the locking position, the free end of the locking bolt 6 is inserted into a recess 8 in a fixed structure such as the door frame as seen in the right picture in Fig. 1 b. It is to be understood that the locking system may be placed in other positions on a door. For instance, a locking system may be arranged on one side of a door or the door be provided with two locking systems, one on each side of a door. It is also to be understood that a locking system may act upwards.

Figs. 2 and 3 show a temperature guard device 10. The temperature guard device 10 is intended to be attached to a fixed structure 12 of a compartment provided with at least one opening as well as at least one closing structure. The closing structure may be any type of door or hatch that can be arranged in the opening for closing the opening. The fixed structure may in that regard be a door frame, a floor or a ceiling of the compartment. The temperature guard device 10 is arranged to cooperate with a locking bolt 14 of a locking system such that in a locking position, the locking bolt 14 is moved into an engaging position with the temperature guard device 10.

The temperature guard device 10 as shown comprises a generally tubular housing 16 forming an inner cavity 20 and having an upper opening 18. The tubular housing is in the example shown generally in the form of a cylinder, but it is to be understood that the housing may have other forms in cross-section, such as elliptic or polygonal. The housing 16 is arranged to be inserted into a recess in the fixed structure 12 and be attached thereto. In order to provide the correct attachment position in the longitudinal direction along a centre axis CA, one end, preferably the upper end of the housing 16, is provided with a circumferential flange 21 around its opening 18 that will rest against a surface surrounding the entrance of the recess when installed. The opposite end of the housing 16 is provided with a bottom wall 22. The housing 16 is preferably made of a material that can withstand impact from liquids such as water and water-containing liquids as well as acid solutions, such as corrosion resistant stainless steel. It is however to be understood that other types of suitable materials may be utilized, having the desired properties.

The housing 16 further comprises a support structure, Fig. 3, that in the example shown is a wall section 24 inside the housing at a distance from the opening 18, which wall section 24 is arranged generally transversal to the centre axis CA and attached to the inner wall of the housing 16. The bottom wall 22 is provided with a drainage passage 26. A tubing or the like may be arranged in the drainage passage 26 for guiding the drained liquid away from the device.

A heat transmitter 30 is attached to the wall section 24 and is extending towards the opening. The heat transmitter 30 is preferably made of a solid piece of material, which material has good heat distributing properties. One favourable material is aluminium or alloys thereof that moreover has good properties to withstand impact from e.g. water.

The heat transmitter 30 has a cross-sectional shape and dimensions that generally correspond to the cross-sectional shape and inner dimensions of the housing 16. In the example shown the heat transmitter has an outer diameter that generally corresponds to the inner diameter of the housing 16. However, in order to reduce the risk of heat to be transferred from the heat transmitter to the housing, its outer surface may be machined such that only small surface areas 32 may be adjacent or in contact with the inner surface of the housing. In the example shown in Fig. 4, the outer surface of the heat transmitter 30 is arranged with longitudinally extending semi-cylindrical grooves 34 that are spaced apart around the circumference of the heat transmitter 30. As seen, one longitudinal section of the outer surface of the heat transmitter 30 may have grooves that are offset from another longitudinal section. As an alternative, the heat transmitter 30 may be made with an unbroken cylindrical outer surface as seen in Fig. 5. This may for example be chosen if the material of the housing has good heat conducting properties or if there is a gap between the outer surface of the heat transmitter and the inner wall of the housing. In any event, an end surface 36 facing towards the wall section 24 is arranged with a flange 38 that fits into a passage of the wall section 24.

The heat transmitter 30 is further arranged with an end surface 40 facing towards the opening 18 of the housing 16. The end surface 40 could either be flat and transversal to the longitudinal direction along the centre axis CA, or could have an end surface that is inclined in relation to the longitudinal direction as seen in Figs. 4 and 5. The design of the end surface 40 of the heat transmitter 30 depends on the design of the free end of a locking bolt that is to be inserted into the opening of the housing and where an end surface 42 thereof can be moved in contact with the end surface 40 of the heat transmitter 30. For instance, the locking system may be arranged to be self locking when a door that it is attached to is closed. A locking bolt with an inclined surface will then be biased to a retracted position against a force from e.g. a compression spring, when the inclined surface comes in contact with a fixed structure such as a door frame. The locking bolt will then be moved to the extended position inside the housing of the temperature guard device by the pushing force of the locking system. The end surface 40 of the heat transmitter 30 will then have a complementing inclination.

Figures 6 to 8 show different designs of the heat transmitter 30. In Fig. 6, the heat transmitter is designed with a central cylindrical passage 100 in which a locking bolt with a planar, transversal end surface is to fit into. The heat transmitter in Fig. 6 is provided with the small surface areas 32 separated by the grooves 34. The heat transmitter of Fig. 7 is modified in that the central passage 100 is provided with small surface areas 32’ separated by grooves 34’, Fig. 7a, instead of the outer surface of the heat transmitter. As seen in Fig. 7b, a locking bolt may be placed in the central passage. Further, Fig. 8 shows a further variant where both the outer surface of the heat transmitter 30 as well as the central passage 100 are arranged with the small surface areas 32, 32’ separated by grooves 34, 34’.

The heat transmitter 30 is further arranged with an attachment point or surface 44 for a heat source 46. In the example shown a flat surface 44 is arranged on the side surface of the heat transmitter 30. A generally rectangular heat source 46 is firmly attached to the surface 44 of the heat transmitter 30. The heat source 46 is connected to a suitable power source via wires 48. The wires 48 may extend through the wall section and be connected to a controller 50 placed in the bottom area of the housing 16. The controller 50 in turn may then be connected with wiring 52 to a power source, such as for instance the electrical system 54 of a vehicle 56, comprising e.g. generator and batteries 58, if the locking system is used with a container truck or semi-trailer truck, Fig. 9. It is to be understood that the power source also may be a stand-alone battery unit 60, forming a system with the device. The system with the battery unit 60 may further be provided with photovoltaic cells 62 that via a charging circuit can charge the battery 60. It is also possible to combine this system with a connection to obtain power from an electrical system 54 of a vehicle. For instance, if a compartment with the device according to the invention, such as a semi-trailer, is connected to a truck, then the power from the electrical system 54 of the vehicle can be used. Flowever, when the semi-trailer has been disconnected from the vehicle, then the battery unit 60 with the photovoltaic cells 62 may be used. The device may also be connected to the mains if the locking system is used for a stationary compartment. If the power is taken from the mains, a suitable transformer may be utilized for reducing the voltage.

The controller 50 of the temperature guard device 10 is further preferably arranged with at least one temperature sensor 64, Fig. 3, that is capable of measuring the temperature in the vicinity of the housing 16 and the locking bolt 14. The temperature sensor 64 is then connected to the circuit board of the controller 50 or may be an integral part of the controller circuit board 50. In this regard, the controller 50 is provided with processing elements like micro-processors 66 and switches 68 such that the heat source 46 is supplied with power if the measured temperature is within a range where there is risk for freezing. Above this temperature range, the power to the heat source 46 is cut off. The controller 50 is further arranged with memory elements 70 where detected temperatures and other data and information may be stored. An important aspect of the controller is further that it comprises a real time clock in order to keep track of time and date. In this regard, the controller may be provided with a micro battery that will maintain power to the real time clock under all conditions. The detected temperatures connected to time stamps will provide information regarding how a temperature curve has been during a certain time period and also a certain distance if such information is available, for instance with a positioning module such as GPS, which may be coordinated with the time log. The device 10 may in this regard be arranged with communication and transmitting elements 72 capable of transferring data and information from the memory elements 70 to an external receiver. Many different communication techniques are readily available on the market and will not be described in detail. The communication elements 72 may further be connected to a communication system of the vehicle.

The above obtained information may be used for showing if for instance a door has been opened at an unauthorized position and/or time and date as well as indications for verifying an unbroken cold chain, which for instance may be very important for transporting food stuff or medicaments.

Figs. 10 - 13 show a variant of a temperature guard device 10. It comprises a generally tubular housing 16 with a bottom 22. The bottom 22 is arranged with a passage 80 for electrical cables as well as for drainage of liquids entering the housing. Inside the housing a heat transmitter 30 is placed. The upper part of the housing is arranged with a rim 81 for bolting to a fixed structure 12 of a compartment. The heat transmitter in the figures comprises a first lower solid part 30i, made for example of aluminium. On the sides of the first part 30i, a number of grooves 82 are arranged for electrical cables as well as for drainage. The upper surface of the first part 30i is formed to create space 84 for a heat source 46, a controller 50 and sensors, such as a temperature sensor as mentioned above. These components are arranged on a printed circuit board 85, PCB, that is placed on top of the first part 30i. Further on top of the PCB 85 a second upper solid part 30ii of the heat transmitter is placed. The upper part 30M is also arranged with grooves 82 on the side for drainage and a central circular recess 86 with a central passage 88. In the central recess a sensor 90 is placed, which may be an inductive sensor. The sensor is electrically connected to the PCB via the central passage 88. The two parts of the heat transmitter and the PCB may be attached together with bolts through holes in the components as seen in Figs. 12 and 13 and the space 84 with the PCB and its components may be filled with a material preventing any liquid or moisture from entering. The variant may further be arranged with a load cell 92 for detecting a locking bolt pressing on the heat transmitter, indicating correct locking of the door.

In order to provide further information to for instance a driver or a transport company, the inductive sensor 90 may be utilized. The sensor 80 may then detect if the locking bolt is present, indicating that the door is locked. The sensor may be connected to a communication unit 92, Fig. 9, that may be placed in the container or in the truck.

The communication unit 92 is provided with communication elements such as GPS, LoRa and GSM, GPRS or any other suitable communication protocol. The GPS will provide time and position when there is an occurrence. A LoRa chip may be used for communication between the communication unit 92 and an indicator 94 that the driver has. The indicator 94 may be a dongle provided with a LoRa chip to communicate with the communication unit 92 and has a light indicator 96 that may provide a green light when the locking bolt is in place and the door is locked and a red light, maybe flashing, when the door is unlocked and open. As an alternative, a display 98 of the vehicle may be used for displaying the status of the lock and the door. The GPRS module may be used for transmitting occurrences to a cloud-based server.

Figs. 14 and 15 show a further variant of a temperature guard device. Here the heat transmitter 130 is in the form of a solid block of suitable heat conducting material, such as aluminium or alloys thereof. The heat transmitter 130 is arranged with a cavity 120 adapted to receive a locking bolt. The bottom of the cavity 120 is arranged with a drainage 126. The heat transmitter 130 is further arranged with a compartment 132 in which a controller 50 is placed. A heat source 46 is connected to the controller for heating the heat transmitter 130 and thus the cavity 120. A suitable lid 134 is arranged for covering the controller 50. The device of Figs. 14 and 15 is intended to be placed in a suitable space in a fixed structure such that the upper surface of the device is in level with for example a floor of a compartment. Figs. 16 and 17 show a similar variant. However, here the heat transmitter 230 has a tubular shape with a central cavity 220. The controller 50 is here embedded in a cavity covered by a bottom wall 232, which wall 232 is provided with a central drainage passage 226. A number of heat sources 46, four in the example, are connected to the controller 50 and are attached to contact surfaces on the outer surface of the heat transmitter 230. This variant is also intended to be placed in a suitable space in a fixed structure such that the upper surface is in level with a surrounding floor area.

Figs. 18 and 19 show a further variant. Here the device is made up of a number of discrete generally plate-shaped elements 300 forming a heat transmitter 330, which plate-shaped elements 300 are inter-connected to each other along the sides thereof. The connections comprise cylindrical elongated elements 310 that fit into half-tubular elongated elements 312, providing a certain movement between adjacent plate shaped elements such that a ring-shape may be formed. The outer surface of the plate-shaped elements 300 are provided with recesses 314 in which a controller 50 and a heat source 46 may be positioned. A suitable lid 316 is covering the controller 50 and the heat source 46. Depending on the heating requirements, some or majority of the plate-shaped elements 300 may be provided with a heat source 46. This forms a design with a tubular cavity 320 in which a locking bolt may be entered. The ring- shaped design may be placed in a suitable housing (not shown) which is placed in a recess of a fixed structure or directly in an appropriate recess in the fixed structure.

In contrast with the previous variants, the plate-shaped elements 300 forming a ring- shaped heat transmitter 330 may be attached to a locking bolt, forming an outer surface thereof, wherein the locking bolt with the plate-shaped elements may enter a cavity of a fixed structure when in a locking position, thereby enabling a heating of the cavity and the locking bolt.

Regarding having heat sources on a locking bolt, a variant thereof is shown in Figs. 20 to 22. Here a solid tubular piece of a locking bolt is arranged as a heat transmitter 430. A generally disk-shaped controller 50 is attached to one end of the heat transmitter 430. The controller 50 is arranged with a number of heat sources 46. The heat sources 46 are attached to recesses 444 on the outer surface of the heat transmitter 430, in the variant shown three heat sources 46. The controller 50 is protected by an end piece 460 having a circular groove 462, in which the controller fits. The end piece 460 is attached to the heat transmitter 430, for example with an elongated rod 464 extending through the centre of the heat transmitter 430. The upper end of the rod 464 may be attached to the rest of the locking system.

Figs. 23 - 24 show a further variant where heat sources 46 are arranged on a locking bolt. Here the heat transmitter 530 is a solid block with a section 532 of generally rectangular shape. One end section 534 of the heat transmitter 530 may be designed with a generally cylindrical outer shape to fit into a cavity of a receiving part in a fixed structure when the locking bolt is in a locking position. The outer surfaces of the rectangular section 532 are provided with recesses 536 for a number of heat sources 46 as well as for a number of controllers 50. The upper end of the heat transmitter 530 may be attached to further parts of the locking system. Again, depending on the heating requirements, some or all of the outer surfaces of the heat transmitter may be arranged with heat sources.

Figs. 25 - 26 show a further variant where heat sources may be a part of a locking bolt. Here the heat transmitter 630 is arranged as an elongated block having a semi circular outer surface and a flat inner surface. On the inner surface a controller 50 with a heat source 46 is attached. The heat transmitter 630 is in turn intended to be attached to a section of a locking bolt (not shown) having a complementing shape, together forming a cylindrical unit. The unit is then designed to fit into a cavity of a fixed structure in a locking position. The unit is further arranged to be attached to further components of the locking system.

As an alternative, the variant of Figs. 25 - 26 may be placed in a cavity of a fixed structure, which cavity is arranged to receive a locking bolt in a locking position.

Regarding the controller, it may preferably be encapsulated in order not to be affected and damaged by moist and the like. For instance, the encapsulation may be done by epoxy potting compounds available on the market. It is to be understood that the embodiment described above and shown in the drawings is to be regarded only as a non-limiting example of the invention and that it may be modified in many ways within the scope of the patent claims.