US20120006517A1

US20120006517A1 - Thermally Conductive Sleeve, Heating System, and Method of Use

Info

Publication number: US20120006517A1
Application number: US13/176,153
Authority: US
Inventors: Keith Baird; Craig Riggs; Jeffrey A. Martin
Original assignee: Heatron Inc
Current assignee: Heatron Inc
Priority date: 2010-07-08
Filing date: 2011-07-05
Publication date: 2012-01-12

Abstract

A thermally conductive sleeve is disclosed which is used to heat a wide range of components. The sleeve can be used in conjunction with one or more heating elements to provide a heating system. Also described are various methods of using the sleeves and heating systems and forming the sleeves and heating systems.

Description

FIELD OF THE INVENTION

The present invention relates to a thermally conductive component for facilitating heat transfer to another component. The invention also relates to heating systems using thermally conductive components and related methods of use.

BACKGROUND OF THE INVENTION

Numerous applications exist in industry and research in which certain components must be maintained at particular temperatures or within certain temperature ranges. For example, in the manufacture of semiconductor materials, temperature is a critical variable and if not controlled, can detrimentally affect the resulting semiconductor material or its properties. Thus, in many manufacturing and processing facilities, significant measures are frequently undertaken to ensure that certain materials, regions of the process or system, or components in thermal association with the sensitive materials or process regions, are maintained at desired temperatures.
A variety of components typically exist within the temperature sensitive regions of a system. Examples of such components include, but are not limited to, process components such as valves and instrumentation, mechanical components such as fasteners, and various other items.
It is well known to use thermal insulation on piping and flow conduits to minimize heat transfer from or to the piping and material flowing therein. Furthermore, it is also known to utilize temperature controlled heaters in such applications and at desired locations in the system.
Although satisfactory in numerous aspects, it is not always possible to apply thermal insulation and/or a controllable heater onto a component of interest in order to limit the extent of heat transfer to or from that component. This difficulty is particularly pronounced if the item of interest is irregularly shaped or has a non-symmetrical shape. Moreover, if the component is relatively small in size, that may further preclude effective use of thermal insulation or of a heater.
Therefore, a need exists for a system and related method for controllably heating an item, and particularly an item that exhibits an irregular or nonsymmetrical shape, or an item that is relatively small.

SUMMARY OF THE INVENTION

The difficulties and drawbacks associated with previously known heating or thermal control systems are addressed in the present invention for a thermal transfer sleeve, heating system using such sleeve, and related method of use.
In one aspect, the invention provides a thermally conductive sleeve adapted for heating an item having an outer contour. The sleeve defines a recessed interior region which is sized, shaped, and configured to fittingly engage the outer contour of the item to be heated. The sleeve comprises a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard.
In another aspect, the invention provides a heating system for heating an item. The heating system comprises a thermally conductive sleeve, the sleeve defining an interior region for receiving and at least partially contacting the item to be heated, and an outer surface. The sleeve is formed from a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard. The heating system also comprises at least one heating element positioned adjacent the sleeve and in thermal communication therewith.
And, in yet another aspect, the invention provides a method of heating an item having an outer surface configuration. The method comprises providing a thermally conductive sleeve defining a recessed interior region. The interior region is sized, shaped, and configured to fittingly engage the outer contour of the item to be heated. The sleeve comprises a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard. The method also comprises positioning the thermally conductive sleeve on the item such that the item is fittingly engaged within the interior region of the sleeve. The method additionally comprises placing at least one heater in thermal communication with the sleeve. And, the method comprises operating the at least one heater to thereby emit heat, whereby said heat is transferred from the at least one heater through the sleeve, to the item.
As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a preferred embodiment thermal transfer member in accordance with the present invention.

FIG. 2 is an exploded assembly view of a preferred embodiment heating system in accordance with the present invention.

FIG. 3 is a schematic cross sectional view of another preferred embodiment heating system positioned about an item to be heated or temperature controlled in accordance with the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention relates to a heat transfer member that defines a recessed interior region sized and shaped to accept a part to be heated. The part typically has an irregular or asymmetrical shape, as explained in greater detail herein. The heat transfer member preferably forms a “sleeve” around the part to be heated. The heat transfer member also preferably includes a smooth uniform outer surface onto which a flexible heater can be attached. A significant aspect of the present invention relates to forming the interior region of the heat transfer member so as to very closely contact the outer surface of the irregular shaped part to be heated. Utilizing such intimate contact between an irregularly shaped part to be heated and a thermally conductive sleeve, facilitates heat transfer between the two. Another aspect of the present invention relates to the selection of material for forming the heat transfer member or sleeve. A preferred material is a curable silicone material as described in greater detail herein. The preferred material provides relatively low flammability properties in conjunction with relatively high thermal transfer properties.
And, the present invention also pertains to a heating system utilizing the various heat transfer members described herein. Additionally, the invention is directed to methods and techniques for heating objects and/or maintaining such objects at desired temperatures.

Thermally Conductive Sleeves

The thermally conductive sleeve preferably defines a recessed interior region that is sized, shaped, and configured to fittingly engage one or more components or parts to be heated. As will be appreciated, typically, the components or parts to be heated and targeted for use with the preferred embodiment sleeves described herein, exhibit non-symmetrical (asymmetrical) shapes and are often irregular or oddly shaped.
The interior region of the various sleeves described herein can exhibit nearly any shape or configuration, and can be of nearly any size permitted by the overall size of the sleeve. It is significant however that the configuration of the interior region closely matches the configuration of the outer surface of the component(s) or part(s) to be heated so that a relatively large proportion of the outer surface of the component or part contacts the inner surface of the interior region of the sleeve. Preferably, upon appropriate placement of a sleeve onto a part to be heated, at least 60%, more preferably at least 75%, more preferably at least 90%, and most preferably at least 95% of the outer surface area of the part enclosed within the sleeve, is in direct contact with the sleeve, and preferably the interior region of the sleeve. This promotes and facilitates conductive heat transfer between the sleeve and the item to be heated.
The preferred embodiment thermally conductive sleeve can be formed in nearly any manner so long as the size, shape, and configuration of the interior region of the sleeve corresponds to, i.e. geometrically conforms to, the outer surface of the item or component to be heated. Preferably, the sleeve is formed by molding an initially flowable liquid material that can subsequently be cured, hardened, and/or otherwise solidified to form the preferred sleeve. As will be understood, it is preferred that in forming a preferred embodiment sleeve, a flowable liquid silicone material is introduced into a mold or other container within which is appropriately positioned, a sample or model of the item to be heated. As the liquid silicone material is introduced into the mold containing the sample, the liquid silicone flows around the sample and thereby upon subsequent curing or solidification, adopts the configuration and contour of the outer surface of the sample. Transfer of liquid silicone preferably continues until the sample is completely covered by the liquid silicone. However, it will be appreciated that the invention includes embodiments in which the sample is not entirely covered by the liquid silicone and instead is only partially covered.
Preferably, the sleeve is formed from a moldable liquid silicone material. Preferably, the material is liquid at ambient temperatures prior to curing. The silicone material is thermally conductive, exhibits a relatively low modulus so that it is somewhat flexible after hardening or solidifying, and is readily repairable after hardening or solidifying. Most preferably, the silicone material exhibits a relatively low flammability upon hardening or solidifying. More specifically, with regard to the thermal conductivity properties of the preferred sleeves, the sleeves typically exhibit a thermal conductivity coefficient of at least about 0.1 W/mK, more preferably at least 0.4 W/mK, more preferably at least 0.6 W/mK, and most preferably at least 0.65 W/mK. The thermal conductivity of the material used for forming the preferred sleeves or heat transfer members can be significantly higher. As will be understood, thermal conductivity is a property of a material that indicates its ability to conduct heat. Multiplied by a temperature difference and an area, and divided by a thickness, thermal conductivity predicts the power loss through the material. Regarding the low flammability properties of the sleeve material, the preferred sleeves, once sufficiently cured, exhibit a minimum flammability rating of V-1 as measured by UL 94 standard. More preferably, the sleeve material exhibits a flammability rating of at least V-0 as measured by the UL-94 standard. Specifically, these ratings are measured as per UL-94 HB test defined in that standard. Preferably, the sleeve material cures upon exposure to temperatures of at least 100° C.
A particularly preferred material used for forming the preferred embodiment sleeves is a two part 100% silicone solids elastomer material, typically used in electronic applications. An example of such a material is QSIL 553 available from Quantum Silicones of Richmond, Va. The QSIL 553 material is typically supplied in two components, an “A” component and a “B” component. The properties of each component are set forth below in Table 1:

TABLE 1

Properties of Preferred Silicone Material, Uncured

	Pre-cured Properties	“A” Component	“B” Component

Viscosity, cps	5,000	3,500
Appearance	Beige	Black
Specific Gravity	1.60	1.60

	Mix Ratio	1:1
	Pot Life	>120 minutes (max 25,000 cps)

The QSIL 553 material is prepared for use by combining the two parts, i.e. components A and B. Preferably, the components are combined in equal amounts by weight, i.e. in a 1:1 ratio, and thoroughly mixed. Mixing by stirring is acceptable. It is preferred to preclude or at least reduce air entrapment in the resulting mixture. Once properly mixed, the liquid material has a pot life of up to approximately 120 minutes. The QSIL 553 material can be cured by exposure to elevated temperatures such as from about 100° C. to about 160° C. for time periods from about 5 minutes to about 15 minutes. It will be understood that in no way is the invention limited to the use of curable materials or to the particular curing profiles noted herein.
After forming a preferred embodiment sleeve from the mixed QSIL 553 material, preferably by molding as described herein, and after the material has cured, the material exhibits the following properties as set forth in Tables 2-4:

TABLE 2

Properties of Preferred Silicone Material, Cured
Cured Properties (cured 7 minutes at 150° C.)

	Durometer, shore A	40
	Tensile, psi	175
	Elongation, %	200
	Tear, die B, ppi	25
	100% modulus, psi	<150

TABLE 3

Flammability of Preferred Silicone Material, Cured
Flammability
UL 94

	3.0 mm	V-0
	1.5 mm	V-1

TABLE 4

Other Properties of Preferred Silicone Material, Cured

	Thermal Conductivity
	W/mK	0.68
	Electrical Properties
	Dielectric Strength, V/mil	490
	Dielectric Constant (1000 Hz)	3.00
	Volume Resistivity, Ohm-cm	1 × 10¹⁴

It is contemplated that one or more agents or additives may be incorporated into the material forming the heat transfer member. For example, a wide array of agents can be used including but not limited to, dispersants, viscosity-adjusting agents, biocides, colorants, dyes, UV stabilizers, density modifying agents, thermal conductivity modifying agents, reinforcing agents, skin-forming agents, and plasticizers.
FIG. 1 illustrates a preferred embodiment thermal transfer member or sleeve 10 in accordance with the present invention. The sleeve 10 defines a front face 20 generally extending between and bounded by an outer wall surface 12. The sleeve 10 also defines a generally recessed interior receiving region preferably accessible from the front face 20. The interior receiving region is defined by an interior wall surface 14 and a bottom or rear wall 16. It will be understood that in no way is the invention limited to the particular sleeve 10 depicted in FIG. 1, nor to the configuration or shape of the interior region of the sleeve 10.
In optional versions of sleeves or thermal transfer members according to the invention, it may be desirable to include one or more apertures in the sleeve providing communication between the interior region of the sleeve and the exterior of the sleeve. The sleeve 10 includes an example of such an aperture 18 extending through the bottom wall 16. Furthermore, it is also contemplated that the various sleeves may further define one or more slots such as a slot 22 extending through a wall of the sleeve.

Heating Systems

The present invention also provides a heating system using one or more of the preferred embodiment thermally conductive sleeves. The heating system generally comprises one or more sleeve(s) and one or more flexible heaters or heating elements. Generally, the flexible heaters or heating elements are positioned relative to the sleeve so as to be in thermal communication therewith. Preferably, the flexible heater or heating element is affixed along and in contact with an outer periphery of the sleeve and most preferably along an outer surface or region of the sleeve.
Heat emitted or produced from the flexible heater is transferred from the surface or region of the sleeve adjacent to or in contact with the flexible heater through the body or a portion of the body of the sleeve to the sleeve interior region. If a part or other item is disposed within the interior region of the sleeve and preferably in a fittingly engaging manner, heat transfer occurs from the sleeve, i.e. the surfaces defining the interior region of the sleeve, to the item fittingly engaged and disposed therein.
Although one or more flexible heaters can be placed in thermal communication with a sleeve in a variety of fashions, a preferred approach is to bond or otherwise adhere the heater to the outer surface of the sleeve. A wide array of commercially available adhesives having sufficient stability at the temperatures at which the sleeve and heater are used, can be employed for bonding the heater to the sleeve.
Preferably, one or more flexible heaters are bonded to the outer surface of a sleeve by placing an uncured face of the flexible heater against an outer sleeve surface and applying heat and pressure to cure and bond the heater material to the sleeve. The flexible heater material is typically a fiberglass reinforced silicone sheet material that can range in thickness from about 0.010 inch to 0.030 inch in thickness. This product is typically cured on one side and the other side remains uncured until processed. Once cured, the material exhibits both excellent tear and dielectric strength while providing a minimum flame retardancy rating of UL 94-HB. The flexible heater preferably includes one or more electrically resistive heating elements that emit heat when passing an electrical current therethrough.
Optionally, the heating system may further comprise an effective amount of a thermal insulating material disposed about the sleeve and/or the flexible heater in thermal communication therewith.
FIG. 2 is a schematic illustration of a preferred embodiment heating system 200 in accordance with the present invention. The system 200 comprises a thermal transfer member or sleeve 110 defining generally hollow or recessed interior region 114. The sleeve 110 also defines an outer surface 120. The heating system 200 further comprises one or more heaters such as flexible, electrical resistance heaters 130 and 140, which are bonded or otherwise contacted along the outer surface 120 of the sleeve 110.
FIG. 3 is a schematic cross sectional view of an item 310 to be heated or otherwise subjected to temperature control. The item 310 is shown extending or projecting from a substrate 300 or other surface. The item 310 is depicted as having an irregular shape. The item 310 is fittingly engaged and received in an interior region defined by a thermal transfer member or sleeve 320 that is generally positioned about the item 310. Preferably, at least a majority and more preferably all or substantially all of an outer surface 312 of the item 310 is in contact with an interior surface 322 of the sleeve 320. One or more heaters such as heaters 330 and 340, are disposed about and in thermal communication with the sleeve 320. FIG. 3 also illustrates an optional thermal insulation layer or member 350 disposed on or about the sleeve 320.

Methods

The present invention also provides methods of using the preferred embodiment heat transfer members and heating systems as described herein. For example, a preferred method of use is as follows. After forming a heat transfer member having an interior region sized, shaped, and configured to fittingly engage the outer surface of an item to be heated, the member is placed over the item such that the item is received within the interior of the heat transfer member. One or more heaters such as electrical resistive heaters are affixed or otherwise positioned in thermal communication with the heat transfer member, prior to, during, or after placement of the heat transfer member over the item. Upon operation of the heater(s), thermal energy, i.e. heat, is emitted from the heater(s) through the heat transfer member, and to the item. Optionally, one or more layers or regions of thermal insulation may be positioned about the system.
Use of the preferred embodiment heat transfer members or sleeves and the heating systems using such members provides numerous benefits such as but not limited to, improving overall heat transfer to an item to be heated, reducing the power to the heater(s) otherwise necessary, improving or prolonging the life of the heater(s) by reducing the temperature otherwise needed to impart sufficient heat transfer to the item, improving ease of installation, and improving the appearance of the heaters and item(s) being heated.
Many other benefits will no doubt become apparent from future application and development of this technology.
All patents, published applications, articles, and standards noted herein are hereby incorporated by reference in their entirety.
It will be understood that any one or more feature or component of one embodiment described herein can be combined with one or more other features or components of another embodiment. Thus, the present invention includes any and all combinations of components or features of the embodiments described herein.
As described hereinabove, the present invention solves many problems associated with previous type devices. However, it will be appreciated that various changes in the details, materials and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art without departing from the principle and scope of the invention, as expressed in the appended claims.

Claims

1. A thermally conductive sleeve adapted for heating an item having an outer contour, the sleeve defining a recessed interior region, the interior region sized, shaped, and configured to fittingly engage the outer contour of the item to be heated, the sleeve comprising a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard.

2. The thermally conductive sleeve of claim 1 wherein the material is a silicone material.

3. The thermally conductive sleeve of claim 2 wherein the silicone material is a curable material and prior to curing, is liquid at ambient temperatures.

4. The thermally conductive sleeve of claim 3 wherein the silicone material cures upon exposure to temperatures of at least 100° C.

5. The thermally conductive sleeve of claim 1 wherein the material exhibits a thermal conductivity of at least 0.65 W/mK.

6. The thermally conductive sleeve of claim 1 wherein the material exhibits a flammability rating of at least V-0 according to UL-94 standard.

7. A heating system for heating an item, the heating system comprising:

a thermally conductive sleeve, the sleeve defining an interior region for receiving and at least partially contacting the item to be heated, and an outer surface, the sleeve formed from a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard;

at least one heating element positioned adjacent the sleeve and in thermal communication therewith.

8. The heating system of claim 7 wherein the heating element is in contact with the outer surface of the sleeve, and the interior region of the sleeve exhibits an asymmetrical configuration that is adapted to receive the item having an asymmetrical outer surface.

9. The heating system of claim 7 wherein the material forming the sleeve is a silicone material.

10. The heating system of claim 9 wherein the silicone material is a curable material and prior to curing, is liquid at ambient temperatures.

11. The heating system of claim 7 further comprising:

a thermally insulating material disposed on at least one of the sleeve and the heating element.

12. The heating system of claim 7 wherein the material exhibits a thermal conductivity of at least 0.65 W/mK.

13. The heating system of claim 7 wherein the material exhibits a flammability rating of at least V-0 according to UL-94 standard.

14. A method of heating an item having an outer surface configuration, the method comprising:

providing a thermally conductive sleeve defining a recessed interior region, the interior region sized, shaped, and configured to fittingly engage the outer contour of the item to be heated, the sleeve comprising a material exhibiting a thermal conductivity of at least 0.4 W/mK and a flammability rating of at least V-1 according to UL-94 standard;

positioning the thermally conductive sleeve on the item such that the item is fittingly engaged within the interior region of the sleeve;

placing at least one heater in thermal communication with the sleeve;

operating the at least one heater to thereby emit heat, whereby said heat is transferred from the at least one heater through the sleeve, to the item.

15. The method of claim 14 further comprising:

positioning thermal insulating material about at least one of the sleeve and the heater(s).

16. The method of claim 14 wherein the outer contour of the item to be heated is asymmetrical in shape and the interior region contacts at least 60% of outer contour of the item to be heated.