Electrically powered stripping tool

Abstract

A finish removal tool for removal of a variety of finishes is provided having a rigid two-handled body, a scraper blade and ducted forced convection heating and cooling elements configured for continuous operation. Embodiments may include adjustable power levels, temperature sensor, indicator lighting, exhaust ducting and heat shields. A variety of scraper blade accommodations are described.

Claims

1. An electrically powered stripping tool for removing finish from a work surface, comprising: a tool body comprising a tool end, an opposing handle end comprising a handle, and a work surface side extending between the tool end and the opposing handle end, an air flow duct comprising an inlet end, an outlet end, and an internal cavity extending between the inlet end and the outlet end, the inlet end located at the tool end of the tool body facing the work surface side of the tool body, the outlet end extending out from the work surface side of the tool body, an electrical heating element located within the air flow duct internal cavity between the inlet end and the outlet end, an electrical fan located within the air flow duct internal cavity between the inlet end and the electrical heating element, the electrical fan configured to draw air into the inlet end of the air flow duct and direct it through the air flow duct internal cavity past the electrical heating element and out of the outlet end of the air flow duct, a heat sink comprising a rigid thermally conductive material attached to the tool end of the tool body such that a portion of the heat sink extends substantially into the internal cavity of the air flow duct at the inlet end of the air flow duct, and another portion extends out from the work surface side of the tool body, a scraper blade attached to and in thermal communication with the heat sink such that the scraper blade extends out from the heat sink to the work surface side of the tool body adjacent to the air flow duct outlet end, and a second handle located near the tool end of the tool body.

2. The electrically powered stripping tool of claim 1 comprising a hot air guide, the hot air guide comprising: a front side, an opposing open side, and two opposing lateral sides, wherein the opposing front and open sides adjoin the two opposing lateral sides in a substantially rectangular shape, and wherein the hot air guide is positioned on the work surface side of the tool body such that the opposing open side is adjacent to the scraper blade, and wherein the outlet end of the air flow duct terminates into the hot air guide.

3. The electrically powered stripping tool of claim 2 wherein the hot air guide comprises an extension or replaceable angled bottom profile to accommodate different handle height positions during scraping.

4. The electrically powered stripping tool of claim 1 wherein the electrical fan is configured to operate at a power selectable speed.

5. The electrically powered stripping tool of claim 1 wherein the electrical heating element is configured to operate at a power selectable heat.

6. The electrically powered stripping tool of claim 1 further comprising a finish material selector switch located on the tool body, the switch configured to control the power supplied to the heating element.

7. The electrically powered stripping tool of claim 6 wherein the finish material selector switch is configured to control the power supplied to the electrical fan.

8. The electrically powered stripping tool of claim 1 wherein the heat sink comprises an aluminum alloy.

9. The electrically powered stripping tool of claim 1 wherein the heat sink comprises a copper alloy.

10. The electrically powered stripping tool of claim 1 wherein the scraper blade extends out from the heat sink at a trailing angle of incidence.

11. The electrically powered stripping tool of claim 10 wherein the heat sink is attached to the tool body via an adjustable hinge, variable thickness shims or other known positioning arrangement so that the scraper blade trailing angle of incidence is adjustable.

12. The electrically powered stripping tool of claim 10 wherein the trailing angle of incidence is between 10 degrees and 25 degrees.

13. The electrically powered stripping tool of claim 1 wherein the scraper blade comprises a thermally conductive factor of greater than 40 W/m-K.

14. The electrically powered stripping tool of claim 1 wherein the air duct comprises an air duct heat shield to contain heat and protect a user from burns.

15. The electrically powered stripping tool of claim 1 comprising a handle heat shield under the second handle to protect a user from burns.

16. The electrically powered stripping tool of claim 1 comprising a temperature sensor, for sensing the temperature of the finish ahead of the scraper blade, and a status light configured to signal when the finish ahead of the blade has attained a pre-set temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 exemplifies an embodiment of the electrically powered stripping tool.

(2) FIG. 2 exemplifies a perspective view of an embodiment of the electrically powered stripping tool with auxiliary features.

(3) FIG. 3 exemplifies an additional perspective view of an embodiment of the electrically powered stripping tool with auxiliary features.

(4) FIG. 4 illustrates an embodiment of the electrically powered stripping tool scraper blade and heat sink.

(5) FIG. 5 illustrates an alternate embodiment of the electrically powered stripping tool scraper blade and heat sink.

(6) FIG. 6 illustrates an alternate embodiment of the electrically powered stripping tool scraper blade and heat sink.

(7) FIG. 7 illustrates an alternate embodiment of the electrically powered stripping tool scraper blade and heat sink.

(8) FIG. 8 exemplifies use of the electrically powered stripping tool on a finish.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 illustrates an example embodiment of the electrically powered stripping tool (100), while FIG. 8 illustrates use of the electrically powered stripping tool (100) on a wood substrate, as will be described. The tool body (110) extends in a longitudinal shape with a tool end (116) and an opposing handle end (115) and a work surface side (112) being the side that faces, typically down or horizontal, the wood surface being worked on. The tool has two handles, one on each end for a controlled force and stoke operation of the device. In one embodiment, the handle (120) on the handle end (115) of the tool body (110) might be an elongated first-type handle and the second handle (190) on the tool end (116) of the tool body (110) might be of a knob design. Other, more specific designs for these handles will accommodate comfort of the operator.

(10) A scraper blade (180), removably attached to, and in thermal communication with, a heat sink (170), extends outwards from the tool body (110) on the tool end (116) of the tool body (110) out from the work surface side (112) at a trailing angle (181) to the work surface, typical of a scraper blade. The heat sink (170) is rigidly attached to the tool body (110) so that the scraper blade (180) has a rigid connection to the tool body (110). The width of the scraper blade (180) is not limited to any dimension, but will vary based upon industry practices in any given application of the tool (100). FIG. 4 exemplifies an embodiment of the scraper blade (180) to heat sink (170) relationship.

(11) As shown in FIG. 8, finish (15) on a wood substrate is removed by stroking the tool (100) in the direction of the handle end (115) as moderate pressure is applied on both the handle (120) and second handle (190) to engage the scraper blade (180) with the finish (15).

(12) Referring to FIG. 1, to enhance removal of the finish (15) from the wood substrate, heat is applied by forced convection via air (10) travelling through an air flow duct (140) and directed onto the finish (15) to be removed. The air flow duct (140) comprises an inlet end (141) and an outlet end (142), with an internal cavity (143) extending between the inlet end (141) and the outlet end (142). The outlet end (142) of the air flow duct (140) is attached nominally vertically through the tool body (110) where it directs the air (10) directly onto the finish (15) to be removed. This allows a portion of the air (10) to pass along the profile of the scraper blade (180) to disperse removed finish (15) that comes off in manageable flakes, rather than fine, air-borne particulate, as in sanding.

(13) Comprised within the internal cavity (143) of the air flow duct (140) is an electrical heating element (150) that heats the air (10) as it travels through the air flow duct (140). Air (10) is moved through the airflow duct (140) from the inlet end (141) to the outlet end (142) by an electrical fan (160) located in the internal cavity (143) of the air flow duct (140) between the inlet end (141) and the electrical heating element (150).

(14) In the preferred embodiment, a hot air guide (130) is attached to the tool body (110) on the work surface side (112) adjacent to the outwardly extending scraper blade (180) where it receives the hot air (10) from the air flow duct (140) and more precisely directs the air (10) onto the finish (15) to be removed and onto the scraper blade (180) profile for effective finish (15) flake dispersal.

(15) The hot air guide (130) comprises a nominally rectangular design. The nominal rectangular design is comprised of two opposing lateral sides (133), a front side (131), and an opposing open side (132) which is adjacent to the scraper blade (180). The two lateral sides (133) define the width of the rectangular design, nominally equal to the width of the scraper blade (180). As the air (10) enters the hot air guide (130), it is directed nominally vertically directly at the work surface where, by forced convection, it effectively confines the air (10) to heat the finish (15) to its release temperature just ahead of the advancing scraper blade (180). It should be understood that the outlet end (142) of the air flow duct (140) may be shaped to accommodate the structure of the hot air guide (130) in lieu of a separate hot air guide (130) element.

(16) While the front side (131) and lateral sides (133) of the hot air guide (130) confine the heated air (10) on three sides to enhance convective heating of the finish (15) ahead of the advancing scraper blade (180), a large portion of the forced air (10) then exits the hot air guide (130) against the scraper blade (180) and out laterally from the tool (100), conveying the released finish (15) flakes with the air (10), thus maintaining a clean scraper blade (180).

(17) During operation, the scraper blade (180) is continuously in contact with both the heated exiting air (10) and the heated finish (15), and in the process, both contribute to some heating of the scraper blade (180). To mitigate this, in the instant invention, the inlet end (141) of the air flow duct (140) is located near the heat sink (170) such that the inlet end (141) of the air flow duct (140) accepts a portion of the heat sink (170) into the internal cavity (143) of the air flow duct (140). As the electrical fan (160) draws air (10) into the air flow duct (140) over the heat sink (170), the drawn in unheated air (10) removes heat from the heat sink (170) by forced convection, allowing the heat sink (170) to conduct the excess heat away from the scraper blade (180), keeping the blade temperature below the melting temperature of the finish (15) so that the scraper blade (180) does not contribute to additional heating of the finish (15) and cause build-up. This cooling aspect of the instant invention facilitates continuous use of the tool (100).

(18) The scraper blade (180) can be made of most alloys of stainless steel, carbide steel or most any metal used for scraper blades. In the best mode, the blade is comprised of a metal with a moderate to good heat transfer performance. Acceptable blades, such as carbon steel, have a thermal conductivity of approximately 45-50 W/m-K. Superior to this are aluminum-bronze alloy scraper blades, which have a thermal conductivity approaching 200 W/m-K. The heat sink (170) should be made of any rigid metal or metal alloy material with good thermal conductivity, including but not limited to materials such as copper, aluminum, copper brass, or alloys, such as aluminum bronze. Thermal conductivity for the heat sink (170) should exceed that of the chosen scraper blade (180).

(19) Thermal grease or intermediate thermal interface materials may be used between the scraper blade (180) and the heat sink (170), if necessary, to enhance heat transfer away from the scraper blade (180) across the scraper blade (180) to heat sink (170) interface.

(20) For a given finish (15) type and thickness, elevating the finish (15) temperature to the desired range is a function of heat applied and length of time applied. In the refinishing industries, removal of finish (15) by scraping is performed in a surprisingly consistent stroke speed when done by hand, thus fixing the length of time. In the case of the instant invention, the applied heat variable can then be further simplified down to two variables: temperature and flow volume of the air (10) directed at the finish (15). A minimum volume of air (10) flow is required in the instant invention in order to clear the removed finish (15) from the scraper blade (180) as well as to convect heat away from the heat sink (170). In the best mode, for a hand-held scale embodiment of the instant invention, air (10) flow of approximately 20 cubie feet per minute (CFM) accomplishes both of these objectives. This is easily achieved with commonly available electrical fan (160) elements powered by a 110-volt 15-amp household circuit. The inventive concept easily applies to larger capacity embodiments as well, and can be implemented using increased amperage or voltage circuits that would be available in a refinishing work setting to deliver increased air (10) flow.

(21) The remaining variable, the required temperature of the air (10) depends upon the release temperature of the finish (15) to be removed. Lower release temperature finishes, such as latex-based finishes, clearly demand lower air (10) temperatures than finishes with higher release temperatures, such as oil-based finishes, in order to bring them up to the release temperature by forced convection. Finishes with still higher release temperatures, such as epoxy-based finishes, require even higher air (10) temperatures in order to bring them up to the release temperature by forced convection. Again, for hand-held scale embodiments of the instant invention, this is easily achieved with commonly available electrical heating elements (150) powered by a 110-volt household circuit. Larger capacity embodiments can be implemented using increased amperage or voltage circuits that would be available in a refinishing work setting to deliver increased temperatures.

(22) In the preferred embodiment, a single tool (100) can be used for removal of any of several types of finishes by use of a selector switch to control the temperature of the air (10). Referencing FIG. 2, the instant invention is configured to simplify adjustment of the temperature of the air (10) with a temperature or finish material selector switch (165). This selector switch (165) would work in combination a variable wattage electrical heating element, electrically pulsed heating elements or multiple heating elements, any of which are represented as the electrical heating element (150) on FIG. 1. Given the relatively standard release temperatures of latex-, oil- and epoxy-based finishes, and the relatively standard scrape, or stroke, speeds used in the refinishing industry, the finish material selector switch (165) setting is pre-calibrated to power the electrical heating element (150) wattage that is optimized for removal of a selected type of finish (15).

(23) Either hard wiring from the finish material selector switch (165) to the electrical heating element or wiring through a simple control module (155), see FIG. 1, can be used. In this context, the control module could be as simple as a terminal strip for power distribution to and from the material selector switch (165), electrical fan (160), electrical heating element (150), and any external power circuitry. It is also contemplated, as will be described, that the control module (155) may incorporate temperature, motion, particulate or other sensory input and additional display elements in order to achieve additional control functionality, an in addition, the control module (155) may be embodied using a programmable device as well.

(24) As illustrated in FIG. 2 and FIG. 3, in another embodiment, the tool (100) incorporates a temperature sensor (200) to sense the surface temperature of the finish (15). In this embodiment, a status light (210), in conjunction with the finish material selector switch (165), is configured to turn on when the temperature of the finish (15) has reached its release temperature, signaling to the operator that it is clear to begin the scrapping stroke. The temperature sensor (200) is preferably mounted away from the heated work area using a port (205) within the tool body (110) for line-of-sight sensing of the work surface finish (15). Use of this embodiment is applicable to the beginning of a stroke where the operator is signaled to momentarily hold the tool (100) in position until the finish (15) is ready to be scraped. Then, as the operator begins the scraping stroke, the design and dimensioning of the hot air guide (130) is such that the finish (15) ahead of the advancing scraper blade (180) reaches its release temperature given the consistent stroke speed of the operator.

(25) It is also contemplated that a variable or multi-speed electrical tan might be employed, controlled by either the finish material selector switch (165) or a separate switch element. Variable or multi-speed electrical tan embodiments are embodied similar to the electrical fan (160) from FIG. 1.

(26) For finishes with excessive thicknesses, one generally performs a second or subsequent pass of the tool (100) to progressively remove the finish (15) down to the wood substrate. This approach ensures preservation of the underlying wood substrate.

(27) In an alternate embodiment, the opposing open side (132) of the hot air guide (130) is not completely open, but rather is shorter than the front side (131) and opposing lateral sides (133). Design specifics of the open side might vary based upon desired air flow patterns, especially where desired finish (15) removal air flow rates differ when used in various applications. Furthermore, the hot air guide (130) may have an extension or an adjustable or replaceable angled bottom profile to accommodate different handle height positions during scraping. Thus, if the operator chooses to drag-scrape the finish (15) at a lower trailing angle (181) and, as a result, holds the handle (120) higher from the work surface, then the hot air guide front side (131) extends down further from the tool body (110), while the hot air guide lateral sides (133) would also co-extend down further at the adjacent hot air guide front side (131), resulting in maintenance of a reasonable gap between the hot air guide (130) and the work surface, which ensures adequate air (10) flow to disperse finish (15) flakes from the scraper blade (180).

(28) Optimum forced convective heat transfer to the finish (15) is achieved when the heated air (10) is directed at, or close to, an angle normally incident on the finish (15). Alternate embodiments with heated air (10) incident onto the finish (15) at a nominal normal angle of incidence to the finish (15) are possible. However, for efficiency purposes, the use of vanes or other directive elements to direct the heated air (10) prior to impacting the work surface are not preferred.

(29) In an alternate embodiment, the heat sink (170) is shielded from the air (10) exiting the hot air guide (130) to more effectively cool the scraper blade (180).

(30) In some cases, the operator of the tool (100) may find that modifying the trailing angle (181) slightly may lead to improved results. The two-handled feature of the instant invention allows the operator to raise or lower the handle (120) as each stroke is made, thereby decreasing or increasing the angle of attack of the scraper blade (180) on the finish (15). Typically, best results with a drag scraper occur when the blade is positioned at a trailing angle (181) of approximately 15 degrees, but in any case, no more than 25 degrees.

(31) Depending upon the scraper blade type (180) and edging, specific trailing angle (181) implementations will vary based upon applications. It should be clear that the instant invention can be configured to accommodate a variety of designs in this aspect, either through a fixed attachment, an adjustably-hinged attachment, use of shims or other known arrangement, in combination with handle positioning and hot air guide (130) dimensioning. It is preferred that the scraper blade (180) trailing angle (181) of incidence be adjusted by varying the angle of the heat sink (170) so that the optimized heat transfer from the scraper blade (180) to the heat sink (170) is not interrupted. If shims or similar arrangement is used to change the trailing angle (181) of the scraper blade (180) with respect to the heat sink (170), close attention should be paid to materials selection and interface to preserve optimized heat transfer from the scraper blade (180) to the heat sink (170).

(32) FIG. 5. FIG. 6 and FIG. 7 exemplify alternate embodiments of the scraper blade and heat sink elements. FIG. 7 illustrates a profiled scraper blade (175) that comprises an integral heat sink. Use of a profiled blade is advantageous for contoured surfaces. A profiled scraper blade (175) may also be a separate blade that attaches to a separate heat sink, such as the heat sink (170) of FIG. 4. Given that a customized profiled scraper blade (175) would see relatively little lifetime usage, it may be made of a softer metal having a higher thermal conductivity, such as brass, which would facilitate easier heat transfer away from the blade. Furthermore, the shape of the hot air guide (130) may be modified to accommodate a profiled scraper blade (175) where the exiting air is directed to best clear the removed finish (15).

(33) In an alternative embodiment shown in FIG. 6, scraper blade (185) comprises a plurality of flexible blades. In this arrangement, FIG. 5 exemplifies an individual flexible blade (184) comprising a scraper blade element (182) which allows for even pressure of the scraping edge against the work surface finish (15) when the work surface is textured, curved or has a discontinuous surface profile. In this embodiment, an attached heat sink element (183) is either separate or segmented so that it does not interfere with the ability of the blade (182) to flex as it follows the contour of the finish (15). This embodiment does not preclude extension of the inlet end (141) of the air flow duct (140) to accept a larger portion of the heat sink (183) into the internal cavity (143) of the air flow duct (140) in order to convect heat away from the heat sink (183).

(34) In an alternate embodiment, exhaust ducting to capture the released finish (15) flakes can be added to at least one side of the tool (100) adjacent to the scraper blade (180) so that the released finish (15) flakes can be directed into a container or a vacuum system or other method of capture.

(35) In alternate embodiments, the tool (100) comprises heat shields below the handle (120) or second handle (190) or around the air flow duct (140) to direct any excess heat away from the operator's hands. Typical heat shield arrangements might be a non-structural planar or shaped skin wrapped around or in front of a heated element between the heated element and the operator's hand positions with a gap between the heated element and the heat shield.

(36) It will readily be apparent to those skilled in the art that other applications are possible for the present invention, and while the embodiments described herein are illustrative of the invention, other modes of implementation are both within the spirit and scope of the invention.