THERMAL APPLIANCE WITH REDUCED ELECTRIC FIELD EMISSION

Abstract

 The present invention relates to a thermal appliance, which comprises a blanket (10) and a heating element (20) distributed inside the blanket (10), and a supply control unit (11) which is electrically connectable on one side to this heating element (20) and on the other side to an electrical power outlet (13) via a power supply plug (12). The thermal appliance is characterized in that the supply control unit (11) further comprises at least a first switching device (21) capable of interrupting the supply of the thermal appliance to one pole and a second switching device (22) capable of interrupting the power supply of the thermal appliance on the opposite pole and which are able to allow the passage of the current or not.
Furthermore, an electronic control device, or an assembly of electronic components working in a co-ordinated manner, contained within the power control unit is able to simultaneously activate/deactivate the first and second switching devices.
In this way, the electric field that can occur in an electric blanket fed by the mains through a non-polarized power plug is reduced, regardless of how the plug is inserted into the power outlet and without any user action.

Description

Field of invention

[0001] The present invention relates to a thermal appliance, such as a thermal blanket, a heating pad, a heating mat and similar heating appliances; in particular, the present invention relates to such a thermal appliance provided with one or more electrical parts which have the purpose of allowing the user a more convenient use of the blanket with a reduction in the emissions of the electric field.

State of art.

[0002] Thermal blankets, heating pads, heating mats and similar products have been known for a long time, and generally include a power control unit and an operating unit electrically connected to it. The control unit generally comprises a blanket, for example consisting of textile material, and a linear heating element distributed inside the blanket and consisting of one or more conductors, mostly with a serpentine pattern, having a path such as to favour, or rather not hinder too much, the blanket bending.

[0003] Normally, the heating element comprises a first and a second coaxial conductor, wherein the first conductor disposed in a spiral around an electrically insulating core, generally textile, and wherein the second conductor is wound in a spiral around the first conductor, with an electro-insulating material interposed thereinbetween; the whole being further enclosed by an external coating made of an additional electro-insulating material. The heat is electrically produced by Joule effect in the conductors, and from here it is distributed in the blanket.

[0004] Typically, a thermal appliance is connected to the electrical outlet for distributing alternate electric current by means of a cable ending in a plug inserted in the outlet. The electric current is typically distributed with two lines, respectively called "phase" and "neutral", wherein the latter shows a potential difference or voltage almost zero compared to the ground, while the "phase" line has an alternating voltage whose value depends on the electricity distribution network, in particular 230V in Europe and in many other countries, 120V in the USA, 100V in Japan, etc.
In some countries, such as in England, Australia or the United States of America, the plug/outlet pair of the power supply network is polarized. Therefore, in such countries, it is possible to adopt production devices designed to ensure that the conductors of the phase and neutral lines, respectively, are connected in such a way that the electric field generated by the thermal appliance is as small as possible, below the perceptible threshold levels perceptible by the user, thus eliminating any kind of inconvenience to the user.

[0005] In other countries, such as in many European countries or in Korea, for example, the plug/outlet pair of the power supply network is not polarized. Thus the conductors of the phase and neutral lines, respectively, will be randomly connected to the plug terminals, and consequently to the control circuit and to the thermal appliance.

[0006] Typically, known blankets operate with a single switching device that is typically electronic as described in the patent application published as EP 3,226,649, or, due to safety issues, with two of these switching devices connected in series, placed on the same polarity. If the plug is incorrectly biased, when these cut-off devices turn off, the problem of the high electric field remaining in the blanket is generated.

[0007] Many solutions are known which solve the problem with a search action of said phase through the actions that the user must do following appropriate instructions for using the control unit; however, these types of solutions, in addition to making said control units more expensive, require a considerable effort for the user to be able to correctly insert the plug.

[0008] For example, the Korean patent application no. KR20100009788 describes a manual detection device of the power ground line, wherein the user himself manually switches the switching terminal of the control switch to a contact in which the user's hand is in contact with the contact terminal of the human body. If a lamp connected to the circuit is kept in the switched state by the non-illuminated contact, the ground side of the power source can be connected to the ground terminal. Conversely, when the lamp is illuminated, the open contact is connected to ground.

[0009] Furthermore, the Korean patent application no. KR20160089653 describes a method for blocking an electromagnetic wave generated by a temperature controller of a thermal blanket, so as to be able to inspect whether an electric field exists in a heating element of a circuit unit and a ground terminal, to bypass the electric field in the ground terminal.

[0010] Finally, the patent application published with n. EP 3,226,649, in the name of the same applicant as the present application, describes a thermal blanket wherein a power control unit comprises a single switching device typically of electronic type control, and therefore it also requires a checking device able to determine the polarization direction with which the power plug has been inserted into the power supply outlet. As a result, the user is alerted, for example by the emission or not of a light signal, if the power plug has been inserted into the power supply outlet in such a direction to reduce the electric field generated, or if it is necessary to reverse such an insertion direction.

[0011] However, in the solution described in EP 3.226.649, the user is requested to personally verify (by detecting the presence or absence of the light signal) the correct insertion of the power plug and possibly to reverse such an insertion direction. Moreover, the light emission, which should warn the user that the power plug has not been inserted in the correct direction to minimize the electric field generated, is often not easily detectable by the user, particularly when in non total darkness conditions.

[0012] Therefore, the Applicant of the present patent application has found the need to simply decrease the effects of the electric field which can occur in an electric blanket supplied by the network through a non-polarized power plug without requiring any attention from the user.

Summary of the invention

[0013] In a first aspect, the present invention relates to a thermal appliance such as that one indicated in claim 1.

[0014] The Applicant of the present application has in fact surprisingly found that the technical problem encountered above can be effectively and reliably solved by means of a thermal appliance comprising a blanket and a heating element distributed inside the blanket, and a power control unit which is electrically connectable on one side to said heating element and on the other side to a power outlet of the AC power supply network via a power plug, characterized in that said thermal appliance further comprises at least a first switching device and a second switching device which are capable of allowing or not the passage of the current and in that said power control unit is able to simultaneously activate/deactivate both said first and second switching device, wherein said first and second switching device are arranged so that said first switching device is able to interrupt the power supply of the thermal appliance on one pole and the second switching device is able to interrupt the power supply of the thermal appliance on the opposite pole.

[0015] In this way, the electric field that can occur in an electric blanket fed by the mains through a non-polarized power plug is reduced, regardless of how the plug is inserted into the power plug.

[0016] In fact, thanks to the fact that the power control unit is able to simultaneously activate/deactivate the two switching devices, the problem of accumulating residual electric field present in the known in the art thermal blankets is solved when the current does not circulates, therefore when that blanket is off.

[0017] Furthermore, no user intervention is required to check whether the power supply plug has been inserted into the power supply outlet in order to reduce the electric field generated, as necessary instead in the thermal appliance described in EP 3.226.649. In fact, the power control unit automatically ensures that the system optimally acts from the electric field accumulation point of view, without any user intervention, which was not possible using the system described in EP 3.226.649.

[0018] The term "thermal appliance" means in the present text and in the appended claims an appliance intended mainly, but not exclusively, for heating a bed or a person in a bed, such as a thermal blanket, a heating pad, a heating mat or a similar thermal appliance having a substantially flat shape and of any size, i.e. completely covering a bed or only a portion thereof or a part of the body or a part of the floor.

[0019] Preferably, said thermal appliance is a heating blanket.

[0020] Preferably, each of said first and second switching device is of the electronic type and indifferently is a semiconductor type switch selected from the group consisting of the TRIACs (from the English "Triode for alternating current"), SCR (from English "Silicon Controlled Rectifiers") or similar elements. More preferably, said first and second switching devices are of the electronic type and are both devices of the TRIAC type.

[0021] According to another embodiment, said first and second switching device are of the electromechanical type, such as for example relays.

[0022] In this way, if the two TRIAC or SCR elements or relays are each connected on their own pole, when they are switched off they substantially isolate the blanket, significantly reducing the value of the residual electric field, regardless on how the power plug has been polarized.

[0023] Preferably, said power control unit comprises at its inside an electronic control device able to simultaneously activate/deactivate said first and second switching devices.

[0024] According to one embodiment, said electronic control device is a single device, such as for example a microcontroller or an integrated circuit.

[0025] According to an alternative embodiment, said electronic control device is an assembly of electronic components working in a co-ordinated manner, such as for example two or more microcontrollers or integrated circuits or similar devices, or combinations thereof.

[0026] Preferably, said blanket is connected by means of a first cable portion to the power control unit, which in turn is connected, through a second cable portion, to said power plug.

[0027] Preferably, said electric current is distributed from said power outlet to said thermal appliance via a first AC power supply line A, also called "phase", which presents an alternating voltage value depending on the electrical distribution network, and via a second AC power supply line B, also called "neutral", which presents a voltage or potential difference almost equal to zero with respect to the ground.

[0028] Preferably, said thermal appliance is supplied with an alternating voltage of less than 250 V and having a frequency of, for example, 50 Hz or 60 Hz.

[0029] In this way, although the voltage frequency is an important parameter to determine the electric field generated by the same voltage, as long as the frequency of the mains voltage is 50Hz or 60Hz, or that available in almost all countries, it does not affect the present invention, which therefore finds its application for all network frequencies of practical use.

[0030] In a second aspect, the present invention relates to a method such as that indicated in claim 7.

[0031] The Applicant of the present application has in fact surprisingly found that the technical problem encountered above can be effectively and reliably solved by a method for reducing the electrical field in a thermal appliance including a blanket and a heating element distributed inside the blanket, and a power control unit which is electrically connectable on one side to said heating element and on the other to a power outlet of the AC power supply network via a power plug, wherein said thermal appliance further comprises at least a first switching device and a second switching device capable of allowing or not the passage of the current, wherein the method is characterized in that said first and second switching device are simultaneously activated/deactivated by an electronic command device, or by an assembly of electronic components which work in a co-ordinated manner, contained within said power control unit, wherein said first interruption device interrupts the supply of the thermal appliance to one pole and said second interruption device interrupts the supply of the thermal appliance to the opposite pole.

[0032] In fact, being able to deactivate the first and the second switching device at the same time, the electric field accumulation inside the thermal appliance is reduced.

[0033] Preferably, each of said first and second switching device is of the electronic type used in the thermal appliance of the first aspect of the present invention cited above and is indifferently a semiconductor type switch selected from the group consisting of the TRIACs (from the English "Triode for alternating current"), SCR (from the English "Silicon Controlled Rectifiers") or similar elements. More preferably, said first and second switching deviced are of the electronic type and are both devices of the TRIAC type.

[0034] According to another embodiment, said first and second switching devices are of the electromechanical type, such as for example relays.

[0035] In this way, if the two TRIAC or SCR elements or relays are each connected on their own pole, when they are switched off they substantially isolate the blanket from the electric field, regardless on how the power plug has been polarized.

[0036] According to an embodiment, said electronic control device used in the method of the present invention is a single device, such as for example a microcontroller or an integrated circuit.

[0037] According to an alternative embodiment, said electronic control device used in the method of the present invention is an assembly of electronic components working in a co-ordinated manner, such as for example two or more microcontrollers or integrated circuits or similar devices, or combinations thereof.

[0038] Further characteristics and advantages of the present invention will be better highlighted by examining the following detailed description of a preferred but not exclusive embodiment, illustrated by way of non-limiting example, with the aid of the attached drawings, in which:

• Figure 1 is a schematic view of an embodiment of a thermal appliance according to the present invention connected to an outlet for distributing electric current;
• Figure 2 shows in detail a first embodiment of the thermal appliance control unit shown in Figure 1;
• Figure 3 shows in detail another embodiment of the thermal appliance control unit shown in Figure 1.

Detailed description

[0039] The following detailed description refers to a particular embodiment of the thermal appliance of the present invention, without limiting its content.

[0040] With reference to Figures 1 and 2, a thermal blanket 10 is described lying on a bed and connected through a first portion of cable 14 to the control unit 11, which comprises an electronic circuit inside it. The control unit 11 is in turn connected, by means of a second portion of cable 15, to the power plug 12 which is inserted into the power outlet 13 for distributing alternating electric current, with double positive and negative polarity. The thermal blanket 10 is supplied with an alternating voltage, for example, of a frequency of 50 or 60 Hz. Inside the heating blanket 10 a heating element 20 is inserted to which a power regulated by the control unit 11 is supplied.

[0041] In the power outlet 13 the electric current is distributed with two supply lines, respectively called "phase" A and "neutral" B (shown in detail in Figure 2), wherein the latter presents a potential difference or voltage almost zero compared with to the ground, while the "phase" line has an alternating voltage of value depending on the electricity distribution network, in particular 230V in Europe and in many other countries, 120V in the USA, 100V n Japan, etc.

[0042] In particular, it has been found, as shown in Figure 2, that the control unit 11 of Figure 1 is provided with a first switching device 21 and a second switching device 22 which are able to allow the passage of the AC or not.

[0043] The two switching devices 21,22 are simultaneously activated or deactivated by a single electronic control device 25, such as for example a microcontroller or an integrated circuit, contained within the control unit 11, thus reducing the formation of an electric field inside the thermal blanket 10.

[0044] Moreover, the two switching devices 21,22 are arranged so that the first switching device is able to interrupt the supply to the thermal blanket 10 on a pole 23 and the second switching device 22 is able to interrupt the supply to thermal blanket 10 on the opposite pole 24.

[0045] Thanks to this arrangement of the two switching devices 21,22 (each connected respectively to its own pole 23,24 and operated by a single electronic control device 25), when the two devices 21,22 turn off, they substantially isolate the blanket 10 from the electric field, regardless of how the power plug 12 has been biased into the power outlet 13.

[0046] This allows to minimize the electric field accumulation inside the thermal blanket 10 during the periods in which it is switched off, regardless of how the power plug is polarized and without any user action, as it was instead necessary using the thermal apparatus described in EP 3.226.649, which comprises a single switching device typically of electronic type control, and also a checking device able to determine the biasing direction with which the power plug has been inserted into the power supply outlet. In the case described in EP 3.226.649, the user was notified of an eventual accumulation of electric field by a current sufficient generation to light on a neon bulb. Then the user, following such a visual indication, proceeded to invert the power plug repositioning in the power outlet.

[0047] On the other hand, in the embodiment of the present invention shown here with reference to Figures 1-2, no checking device and, consequently, no user intervention is required thanks to the fact that the present solution has two switching elements able to interrupt both the supply poles of the blanket.

[0048] With reference to Figure 3, another embodiment of the present invention is shown, in which both the switching devices 21,22 are of the electronic type and in particular are constituted by TRIAC (from the English "Triode for alternating current").

[0049] Of course, many modifications and variations of the described preferred embodiments will be apparent to those skilled in the art, still remaining within the scope of the invention.

[0050] For example, in the embodiment described above with reference to Figure 3, two TRIACs were used as switching devices 21,22 and the used supply to the heating element 20 was of the alternate type. However, in another embodiment of the present invention it is possible to use, instead of the TRIACs, switching devices 21,22 of the SCR type; in this case, the power supply used will no longer be of the alternate type, while remaining within the scope of the present invention.

[0051] Moreover, in the embodiment described above with reference to Figures 2 and 3, the electronic control device 25 is a single device, such as for example a microcontroller or an integrated circuit. However, in another embodiment of the present invention it is possible to use, in place of said single microcontroller or integrated circuit 25, an assembly of electronic components 25 working in a co-ordinated manner, such as for example two or more microcontrollers or circuits integrated or similar devices 25, or combinations thereof, while remaining within the scope of the present invention.

[0052] Therefore, the present invention is not limited to the preferred embodiments described, illustrated only by way of example and not for limiting purposes, but is defined by the following claims.

Claims

1. Thermal appliance comprising a blanket (10) and a heating element (20) distributed inside the blanket (10), and a power control unit (11) which is electrically connectable on one side to said heating element (20) and on the other side to a power outlet (13) of the AC power supply network via a power plug (12), characterized in that said thermal appliance further comprises at least a first switching device (21) and a second switching device (22) which are capable of allowing or not the passage of the current and in that said power control unit (11) is able to simultaneously activate/deactivate both said first (21) and second (22) switching device, wherein said first (21) and second (22) switching devices are arranged so that said first switching device (21) is able to interrupt the power supply of the thermal appliance on one pole (23) and said second switching device (22) is able to interrupt the power supply of the thermal appliance on the opposite pole (24).

2. Thermal appliance according to claim 1, wherein each of said first (21) and second (22) switching devices is of the electronic type and indifferently is a semiconductor selected from the group consisting of TRIAC, SCR or similar elements.

3. Thermal appliance according to claim 1, wherein each of said first (21) and second (22) switching devices is an electro-mechanical relay.

4. Thermal appliance according to any one of the preceding claims, wherein said power control unit (11) comprises at its inside an electronic command device (25) able to simultaneously activate/deactivate said first (21) and second (22) switching device.

5. Thermal appliance according to any one of the preceding claims, wherein the electric current is distributed from said power outlet (13) to said thermal appliance via a first AC power supply line (A), also said "phase", which presents an alternating voltage value depending on the electrical distribution network, and via a second AC power supply line (B), also said "neutral", which presents a voltage or potential difference almost equal to zero with respect to the ground.

6. Thermal appliance according to any one of the preceding claims, wherein said blanket (10) is connected via a first cable portion (14) to the power control unit (11), which in turn is connected, via a second cable portion (15), to said power plug (12).

7. Method for reducing the electrical field in a thermal appliance including a blanket (10) and a heating element (20) distributed inside the blanket (10), and a power control unit (11) which is electrically connectable on one side to said heating element (20) and on the other to a power outlet (13) of the AC power supply network via a power plug (12), wherein said thermal appliance further comprises at least a first switching device (21) and a second switching device (22) which are capable of allowing or not the passage of the current, wherein the method is characterized in that said first (21) and second (22) switching device are simultaneously activated/deactivated by an electronic command device (25), or by an assembly of electronic components (25) which work in a co-ordinated manner, contained within said power control unit (11), wherein said first (21) and second (22) switching devices are arranged so that said first switching device (21) is able to interrupt the power supply of the thermal appliance on one pole (23) and said second switching device (22) is able to interrupt the power supply of the thermal appliance on the opposite pole (24).

8. Method according to claim 7, wherein each of said first (21) and second (22) switching devices is indifferently of the semiconductor electronic type selected from the group consisting of TRIAC, SCR or similar elements, or an electro-mechanical relay.

Drawing