Patent Application
20170367761
The present invention is concerned with a skin treatment device, for example a hand-held hair removal device. The device may comprise a handle with an energy supply, an application head with at least one heat source comprising at least one semiconductor light source, and at least one heat sink comprising cooling fins.
It is known to use skin treatment devices using semiconductor light sources for hair removal. For example, EP 1 771 121 B1 discloses a radiation device for use in an epilator comprising LEDs as a light source.
Every light based device inherently generates heat and the light source heats up. High temperatures of the light source may lead to a performance loss. Thus, an efficient cooling system is necessary to get a high performance light based hair removal device. Heat conductors in cooling systems spread and conduct heat quickly away from a heat source to cooling fins. Known cooling systems use for example a solid copper or aluminum bar for conducting heat from a heat source to cooling fins. However, this increases the weight of a skin treatment device, which is undesired. In addition, efficient use of such cooling systems is limited to transferring heat over short distances only which also limits efficiency of the light output power.
Further, US 2005/0231983 A1 discloses an LED curing device having a rigid body with an end tip comprising the LED and a fan located at an opposite end of the body. A heat pipe extending through the body is bonded or glued with one end to the LED and with an opposite end to a heat sink near the fan. The fan blows air over the heat sink.
It is an object of the present disclosure to provide skin treatment device with an improved heat transfer system.
A skin treatment device is provided comprising a handle with an energy supply, an application head with at least one heat source comprising at least one semiconductor light source, and at least one heat sink comprising cooling fins, wherein the heat sink is located remote from the heat source within the handle, and wherein the heat source is thermally connected to the heat sink by means of a heat pipe heat transfer system. In more detail, the heat transfer system may comprise a hermetically sealed tubular body containing a working medium, wherein the pressure within the tubular body is chosen such that the working medium is a saturated liquid at room temperature and may be vaporized by the heat source. A wick structure may be located in the tubular body exerting a capillary action on the working fluid, i.e. for transporting the liquid from the condensation area (heat sink) to the evaporation area (heat source). Wick structures suitable for heat pipes include sintered metal powder, screen, and grooved wicks, which have a series of grooves parallel to the pipe axis. Depending on the geometry of the tubular body, provision of a wick is not required. For example, a heat pipe may have a configuration and/or coating provided on the inner walls for providing a capillary action. High heat conductance in conjunction with the fact that heat pipes are lightweight enables the possibility to spatially separate heat source and heat sink over higher distances.
In accordance with one aspect the application head may be sealed, e.g. hermetically, without openings to the ambience and may comprise at least one air channel adapted for guiding air to the at least one semiconductor light source. The at least one air channel may have at least one inlet opening which is located in the handle and at least one outlet opening which is located in the handle.
In addition or as an alternative, in accordance with a further aspect the application head may be pivotably connected to the handle.
Heat pipes in different base shapes of the tubular body, for example round or flat, are suitable for use in the skin treatment device. In particular, the heat pipes may have a rectangular shape. The tubular body of the heat transfer system may be made from a thermally conductive material, especially copper, steel or aluminum. The working medium of the heat transfer system may be a fluid, like a refrigerant, for example water, ammonia or 1,1,1,2-Tetrafluoroethane (R-134a).
The energy supply may comprise an energy storage, like a battery, in particular a rechargeable battery, located in the handle. In addition or alternatively, the energy may be provided via a mains cable. Optionally, the heat source is electrically connected to the energy supply by means of the tubular body of the heat pipe heat transfer system.
The heat source of the skin treatment device may comprise light source suitable for hair removal. For example, the heat source may comprise a vertical-cavity surface-emitting laser (VCSEL) array, a vertical external cavity surface-emitting laser (VECSEL) array, a light emitting diode (LED) array and/or an organic light emitting diode (OLED) array.
The heat sink of the skin treatment device may comprise an appliance for increasing heat transfer from the heat source. For example at least one cooling fan may be provided to raise heat dissipation. In addition or alternatively, at least one thermoelectric element may be provided.
The application head may be sealed, in particular the head may be mechanically sealed without any openings. With such an environmental encapsulated head design the head is protected against environmental influences like dust, humidity, water, or lotion. In this case, the heat sink, including an optional fan, the cooling air inlets and outlets may be completely placed in the handle.
For some applications it may be desirable if the application head is rigidly connected to the handle. In addition, the use of, for example, rigid copper material for the tubular body of the heat pipe sets limits movements of the head relative to the handle. However, it is possible to bend heat pipes in required shapes. This characteristic enables more industrial design freedom between head and handle. The angle between the center line of the head and the center line of the handle may be chosen ±60°. This allows an exposed head with a fixed angle between handle and head. Handling of the hand-held device improves, due to design freedom to get an optimal angle between handle and head for best intended device usability.
Alternatively, the application head may be pivotably connected to the handle. For example, heat pipes with an additional flexible segment enable designing a device with exposed swivel head. Heat conductors with an additional flexible segment enable designing a device with exposed swivel head. The head may be mechanically connected to the device body (handle) via a constant torque hinge, for example as typically used for notebook displays. This hinge separates the heat conductive means from the mechanical means. The constant torque hinge allows changing the angle while maintaining sufficient rigidity of the device for use without unintended change of the head-body angle. When providing a swiveling connection the heat conductivity of the connection is very important. A typical mechanical hinge even if made of copper or alumina may not have sufficient heat conductivity to meet the requirements for a device with extensive heat load within the device head.
An important aspect is the solution how to enable sufficient heat transport from the heat source in the application head to the heat sink in the handle or body while having a swiveling connection between both parts. A heat pipe may be made flexible by inserting a flexible segment between the heat source and heat cooling fins section. The flexible segment accommodates any relative motion between heat source and heat sink. An example for such a flexible segment is a flexible bellows section of a heat pipe arranged between the application head and the handle. As a further example, a flexible segment may comprise a highly heat conducting graphite foil, e.g. a pyrolytic graphite sheet (PGS), between the application head and the handle, e.g. connected to the heat source part and the heat sink part of the cooling system. Flexible heat pipes work in principle equivalent to the rigid heat pipes. This additional feature increases the usability of the device, because head orientation to skin adapts better to body shape while usage.
In addition or as an alternative, the application head may be pivotably connected to the handle by means of a heat conducting hinge having a spindle and a jack. The spindle may comprise a portion of the tubular body of a heat transfer system and the jack may comprise a portion of the tubular body of a heat transfer system or a pyrolytic graphite sheet (PGS). In other words, the heat transfer system may comprise a first heat pipe being part of the spindle and a second heat pipe being part of the jack. As an alternative, a heat pipe is part of the spindle and a pyrolytic graphite sheet is part of the jack.
According to one aspect, the application head of the skin treatment device further comprises a transparent or translucent skin contact window. Such a skin contact window prevents direct contact of the user's skin to the light source and further prevents environmental influences like dust, humidity, water, or lotion.
During operation a light source module, for example a LED light source module, may generate up to 75 W heat power and the surface of the light source module could heat up to about 80° C. A part of the heat power is heating up the skin contact window. The higher the skin contact window temperature is the more uncomfortable is the usage for the user. To prevent high temperatures at outside surface of the skin contact window, active cooling of the skin contact window and/or thermally decoupling of the window from the heat source is desirable.
In this respect, a first side of the at least one semiconductor light source may be thermally connected to the heat transfer system and a second side of the at least one semiconductor light source which is opposite the first side may be located within the application head at a position and orientation permitting light to be emitted from the at least one semiconductor light source through the skin contact window. In other words, the heat pipe heat transfer system is arranged such that heat is transferred from the side facing away of the skin contact window from the heat source, i.e. the semiconductor light source.
In addition or as an alternative, the skin contact window may be thermally connected to the heat transfer system or it may be thermally connected to an additional heat transfer system. The additional heat transfer system may be a heat pipe heat transfer system which comprises for example a hermetically sealed tubular body containing a working medium wherein the pressure within the tubular body is chosen such that the working medium is a saturated liquid at room temperature which may be vaporized by the heat source. In other words, the skin contact window cooling design may comprise connection of the glass or ceramic window to a separate second heat pipe with a heat conductive frame, for example pre-stamped and/or with an applicable heat conductive gap filler, e.g. filled silicon rubber or graphite based filler). The window may be made of a good heat conducting material, like ceramic, sapphire or the like. Within the handle of the skin treatment device, the semiconductor light source and the skin contact window may each have a separate heat sink, for example separate cooling fins. As an alternative, the semiconductor light source and the skin contact window may share one common heat sink. Two different fans may be provided for separate heat sinks. However, even with two separate heat sinks, it is preferred to provide only one single fan which serves both cooling systems.
The skin contact window may be directly connected with a heat transfer system. However, for providing a homogeneous and higher performance heat flow the skin contact window may be thermally connected to the heat transfer system or to the additional heat transfer system by means of a thermoelectric cooler. For example, this skin contact window cooling system comprises a Peltier element placed between the heat pipe and the inner side of the skin contact window. A Peltier element is an active heat conduction element which enables homogeneous and high performance heat flow from low to high temperature sections. Provision of a thermoelectric cooler, like a Peltier element, facilitates heat transfer from the light source and from the skin contact window using only one single heat pipe to cool both, the LED module or the like light source and the skin contact window at lower temperature at the same time.
In addition to transferring heat from the skin contact window to the handle or as an alternative, the application head may comprise cooling fins which are thermally connected to the skin contact window. For example, the skin contact window cooling system comprises a head housing made of a heat conductive material, e.g. aluminum or specific filled plastic, which is connected to the skin contact window directly or via a conductive frame. In other words, the application head housing may serve as a heat sink, for example as a heat capacitor and/or with additional cooling fins. Heat sink fins can be integrated in the application head housing, i.e. the application head housing and cooling fins are one component part. Alternatively, cooling fins may be fitted at the rear side of the head that is the side facing away from the skin contact window. This design supports an encapsulated application head design.
Further or as an alternative, the application head may comprise at least one air channel adapted for guiding air through a gap between the at least one semiconductor light source and the skin contact window. The skin contact window cooling system may comprise an air channel between the application head and the handle. A function of the channel is to suck heated air from the gap area between the light source and the skin contact window by means of a fan which may be placed in the handle. The working principle of this fan is to suck air from one side (inlet side) and to create overpressure at the opposite side (outlet side). At the suction or inlet side the fan generates a negative pressure, i.e. a vacuum. With the fan located in the handle and the handle connected to the application head via an air channel, vacuum generated by the fan in the handle sucks in air of ambient pressure from the application head area via the air channel, thereby generating an air exchange from the application head to the handle. This working principle requires a connection of the application head to the ambient pressure to supply the head with fresh cooling air.
In general, the at least one air channel may comprise at least one inlet opening which is located in the applicator head and/or in the handle and at least one outlet opening which is located in the applicator head and/or in the handle. For example, a fresh air inlet for window cooling and/or interruption of heat flow to the window from the light source is located in the handle which is directly connected to the application head. In some embodiments, the application head may include air guiding walls to lead the air between the light source and the skin contact window. A second channel connection to the handle may suck the heated air due to vacuum generated by the fan in the handle. Due to sealed head design, it is possible to use a lotion or the like liquid with the skin treatment device. Alternatively, a fresh air inlet for head cooling is located in the application head itself. For example, the application head includes air support walls to lead the air between the light source and the skin contact window. In some embodiments, only one cooling channel between the application head and the handle may be sufficient. Due to this non-encapsulated head design, the use of a lotion or the like liquid together with the device is limited. The cooling air channels may be integrated in the handle and/or in the head housing or may be provided as an extra part, e.g. extra build-in pipe channels.
Still further, the applicator head may comprise a fan adapted to pass air through the air channel. In more detail, the skin contact window cooling system may comprise a non-encapsulated design of the application head with small openings and a small fan integrated in the head. Continuous exchange of fresh air between the skin contact window and the light source module prevents that the heat emitted by the light source module heats up the skin contact window to a temperature level which is unpleasant for the user. Usability of lotion or the like is limited due to the non-encapsulated head.
The light output area may be designed such that a window is provided which does not directly contact a user's skin. For example, an additional cap, which is placed in front of the light output area, i.e. a window, prevents during usage a contact between the skin and the window. According to one aspect, the cap has no contact to the window, except some possible fixation contact points. This provides a small air gap between the skin contact cap and the window which prevents heat transfer from the window to the skin spacer cap.
Such a skin spacer cap may reduce heat transfer from a heated window to the skin due to a reduced contact surface size to the skin. In addition, the cap may keep the skin on distance from the heated window. It may further serve as a light guide for the emitted light. Provision of such a cap may result in that no additional cooling of the window may be required.
An additional gel-cushion, a gel-cushion attachment, may be placed in front of the light output window. The gel may have a high light-transmissivity for visible and NIR-light and is encased by a flexible and transparent foil. The attachment may have no contact to the window, except of some fixation contacts. A small gap between the gel-cushion attachment and the window prevents or significantly reduces the heat transfer of the warm window to the gel-cushion. A benefit of the gel-cushion is to improve the adaptation of the head to body shapes due flexible properties of the gel-cushion while device usage and the possibility to use lotion or the like liquids together with the skin treatment device.
The skin treatment device as shown in the
The application head 2 comprises a light source in the form often an LED module 3. The light based device is suitable for skin treatment, especially for applications that need a high intensity light source, and if the light delivery system is desired to be small and light. Possible applications include light based hair removal, light based skin rejuvenation via bio-photo modulation and acne treatment.
The application head 2 may be designed to be a separate component part which is split from the handle 1. This results in a better application head adjustment to different body shapes. Further, an environmental encapsulated head design is feasible. The compact size of the application head improves the usage precision for small treatment areas (e.g. face and bikini) by enhancing the visibility of the skin to be treated.
In the skin treatment device of
The LED module 3 is thermally connected to the heat sink 4 by means of a heat pipe 6. The heat pipe 6 comprises a tubular body of a flat and substantially rectangular shape which is hermetically sealed. A working medium is located within the tubular body with the pressure of the working medium within the tubular body being chosen such that the working medium is a saturated liquid at room temperature and may be vaporized by the heat source that is of the light source 3. As can be seen for example from
In the embodiment of
An air channel is provided in the skin treatment device, which air channel comprises an inlet 8 located in the handle 1, a passage 9a from the handle 1 to the head 2, a further passage 9b from the head 2 to the handle 1, and an outlet 10. Thus, ambient air may be sucked in by fan 5 via the inlet 8, floating about the light source 3 and through a channel 9c between the light source and the skin contact window 7, back into the handle 1 and through fan 5 to outlet 10. In other words, fan 5 not only supplies cooling air to fins 4 but also for cooling skin contact window 7.
An alternative design is depicted in
A further alternative is depicted in
Still further embodiment is depicted in
Due to the relatively rigid structure of heat pipe 6, the application head 2 may be fixed with respect to the handle 1. Nevertheless, it is possible to position the application head 2 with respect to the handle 1 in different ways to get an optimal angle between of the application head 2 and the handle 1 for the best intended usability of the handheld skin treatment device.
As an alternative, heat pipe 6 may be provided with an additional flexible segment 13 as depicted in
In more detail, the flexible segment 13 may be a swiveling head design with a flexible heat pipe 6. Heat pipes may be made flexible by inserting a flexible bellows section between the upper and lower part of the heat conductor/heat pipe. Such a flexible heat pipe is available for example from the company Aavid Thermalloy, LLC under the name Thermacore flexible heat pipe. This additional feature of a swiveling application head 2 increases the usability of the device, because adjustment of the head-body angle allows improved handling on difficult to reach body areas.
As an alternative, the flexible segment 13 for the swiveling head design may comprise a PGS (Pyrolytic Graphite Sheet). Such a PGS has a very high heat conductivity within the plane of the material. The heat conductivity can be up to 5 times higher than the heat conductivity of pure copper. In addition, the PGS material allows bending with very narrow bending radius and high number of bending cycles. Such a PGS is available from the company Panasonic under the name PGS graphite sheet.
To improve heat transfer from the skin treatment window 7, the skin treatment window 7 may be thermally connected with a separate heat transfer system in the form of a heat pipe 14 as shown in
As an alternative, the skin contact window 7 may be provided with a cooling system transferring heat from the skin contact window 7 to the cooling fins 4 by means of heat pipe 6. In this embodiment it is preferred to provide a thermoelectric cooler, for example a Peltier element 16 as shown in
For some applications it may be desirable to prevent direct contact between a user's skin and a window 7 of the device. As an alternative to a skin contact window 7 a light output window cap in the form of a skin spacer cap 17 is provided in the embodiment depicted in
In addition or as an alternative, a gel cushion 20 may be provided between the window 7 and the user's skin as depicted in
In the present embodiment, the first (upper) heat conductor 6′ may be just a plate of a good heat conducting material, e.g. copper or alumina, a heat pipe 6 or directly an extended area of the PGS sheet 24. The heat from the heat source 3 in the head 2 is transferred via the upper heat conductor 6′ to the flexible part 13 of the heat conductor which may be a PGS foil. The hinge 21 of
An aspect of the embodiment of
Another option to transfer the heat from the head 2 to the body or handle 1 is using a specially designed hinge 21 which has the capability to transfer sufficient heat.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16176379.2 | Jun 2016 | EP | regional |
| 17169532.3 | May 2017 | EP | regional |
