BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to surface treating tools, and more particularly, to a mechanical paint removing tool.
2. Brief Description of the Prior Art
Generally speaking, the three approaches used in removing paint from a surface are chemical, thermal and mechanical. Chemical paint removers operate by softening, dissolving, or otherwise degrading the paint film so that it can be flushed or scraped from the surface. Chemical paint removers have the shortcomings of being slow, messy, expensive and somewhat hazardous. The expense involved in using chemical paint removers makes them impractical for use on large surface areas.
Thermal paint removers are used to soften and degrade the paint film so that it can be scraped from a surface. Thermal paint removers are also slow and expensive and possess possible hazards as well as sometimes sealing underlying surfaces, such as wood. The possible fire hazard of the thermal paint removers is sufficiently great, so that in some localities special permits are required for use of such equipment.
Mechanical paint removers generally fall into three sub-categories, the first of which is the use of abrasive sheets, blocks or forms, wherein friction and abrasion of hard particulate matter against the paint film is used to remove the paint. Generally speaking, such appliances as motorized sanding tools, and the like, fall into this category. A shortcoming of this form of paint removal is that the removal of paint tends to clog the abrasive particulate matter and in addition, sometimes, motorized abrasive tools, such as disc sanders, and the like, are confronted with considerable down time which is spent in either cleaning the disc or changing discs.
Another sub-category of mechanical paint removers is the use of wire brushes that are both used as hand tools and motor driven tools. Wire brushes are effective on chalk paint films, but are not too effective on tougher films unless extremely stiff wire is used. When such stiff wire is used, a wood surface may be easily cut or scratched by use of a wire brush.
The third sub-category of mechanical paint removers is that of scrapers, which fall into a wide variety of shapes and styles. Generally speaking, scrapers remove paint by pushing or pulling against brittle film edges to plane or split the film-to-film or, film-to-underlying surface bond. Hand scrapers are slow and laborious to use and can not be used to produce a desired feathered edge where unsound paint is removed from adjoining sound film.
In addition, there is in the art, examples of mechanical abrading tools wherein an abrasive element is mounted on a base and the base is rotatably driven so that the abrasive element engages a working surface. Examples of such structures are found in the Staehle U.S. Pat. No. 1,652,915, Gray U.S. Pat. No. 1,358,148 and Walters U.S. Pat. No. 3,216,041.
The Staehle patent shows a scraper having a rotary disc with a plurality of stacks of disc cutters arranged so that the axis of the disc cutters is at a 90° angle relative to the axis of rotation of the base. The Walters patent shows a rotary scraping device wherein arcuate saw blade-like members are disposed on the underside of the base. The Gray patent shows a rotary scraping device wherein scraping blades are disposed at different angles to the axis of rotation or radius of the disc. Heretofore, non of the mechanical abrading tools as exemplified in the art set forth has been satisfactory for quickly removing paint from an underlying surface.
It is therefore, the object of this invention to provide an improved mechanical paint removing tool of the type which is to be driven by another power tool, which removal tool is capable of quickly removing paint from a surface and without harmful effects to the surface even where the surface is wood or a similar substance.
SUMMARY OF THE INVENTION
This invention is directed, in brief, to the provision of an improved mechanical paint removing tool.
The best mode currently contemplated for carrying out the invention includes the provision of a base having an upstanding shaft for connection to a power tool, such as a hand drill or the like. The base has depending brackets for rotatably mounting threaded abrading elements for rotation about an axis which is in a plane perpendicular to the axis of rotation of the base. Moreover, the axis of rotation of the abrading elements is at a slight angle relative to the axis of rotation of the base or of a radius emanating therefrom. A handle and shroud structure encloses the base for control and guidance thereof during periods of use.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the mechanical paint remover tool of this invention showing it in use with a power tool, which is illustrated in phantom outline;
FIG. 2 is a fragmentary enlarged section view of the mechanical paint removing tool of this invention;
FIG. 3 is a view similar to FIG. 2 showing the tool in engagement with a surface to be worked;
FIG. 4 is a bottom plan view of the paint remover tool of this invention;
FIG. 5 is a fragmentary side elevational view of the abrading elements supporting base used in the tool of this invention; and
FIG. 6 is a section view through the abrading element supporting base illustrated in FIG. 5.
While the invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a specific embodiment therefor, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT
The mechanical paint scraper 10 of this invention is intended for use with a power tool for driving the same, such as the phantom illustratedhand drill 12, shown in FIG. 1. The mechanical paint scraper includes a handle 14, preferably of a size and shape to be grasped by hand. Handle 14 is connected to a shroud 16 by a suitable means such as the fasteners 16a.
The shroud 16 includes bearings 18, received in an upright opening 20 in the shroud. The bearings 18 provide a shaft receiving opening 22 therethrough. Shroud 16 includes a lower depending annular skirt 24 which has a chute-like opening 26 therein and the adjacent portion of which has an outwardly diverging flange portion 28.
The mechanical paint scraper 10 of this invention further includes an abrading element supporting member, generally indicated 32. The abrading element supporting member 32 includes a substantially disc-like base 34 with a centrally positioned shaft 36 extending uprightly therefrom. Shaft 36 is of a size and shape to be rotatably and slidably received in bore 22 of bearings 18 in the shroud 16. The upper end of the shaft 36 includes an annular groove 38 which receives a snap ring 40 for holding the member 32 in assembly with the shroud 16, while permitting slight relative vertical movement between the two. The shaft 36 terminates in a reduced end 42 which is of a size and shape to be secured in the chuck of a power tool, such as the phantom illustrated hand drill 12.
A central boss 44 depends from the underside of the base 34. A plurality of circumferentially spaced flanges 46 depend from the periphery of base 34 spaced from boss 44. Each of the flanges 46 has an opening 48 for receiving the enlarged head 50 of each pin 52. Each pin 52 has a threaded end 54 opposite the enlarged head 50, which ends are threadably received in threaded bores 56 in boss 44 for rotatably mounting an abrading element or bit 58 about its central bore 60. The several flanges 46 and boss 44 cooperate to provide mounting yokes for rotatably mounting the abrading elements 58.
Each abrading element or bit 58, has a threaded periphery 62. Preferably, if the supporting member 32 is to be rotated in a clockwise direction, it is desired that the threaded periphery 62 of each abrading element 58 be a left-handed thread, whereas, if the member 32 is to be rotated in a counterclockwise direction, then a right-hand thread is desirable on the periphery 60 of the abrading element 58. It is to be noted that the crest 62a of the teeth of the thread is sharp and terminates in a rounded root 62b, and that the leading edge of the next adjacent tooth has a front face 62c which is substantially perpendicular, or transverse to, the axis of rotation of the element 58 being 90° or, within a few degrees thereof. Also, preferably, the end corners of the abrading element 58 are rounded as shown at 64.
Referring to FIG. 4, there is shown therein a dotted line 66 which represents the axis of rotation of the cylindrical abrading element or bit 58 and a line 68 which represents a radius from the axis of rotation of the member 32 and intersects the axis 66 of the abrading element 58. The angle of this intersection is represented by the letter A in FIG. 4. It has been found that for most uses, when the value of the angle A is approximately 15°, optimum paint scraping action is resultant from the operation of the scraper of this invention. As the shaft 36 is rotated, the abrading elements or bits 58, produce a combination action of slicing and scraping paint film. The threaded edges of the abrading elements 58 slice into the paint film, represented by the letter P in FIG. 3 and simultaneously scrape the sliced segments away from an underlying surface, represented by the letter S in FIG. 3. It has been found that operation of the tool in this manner results in uniform wear on the threaded periphery 62 of the abrading elements 58 and clogging is held to a minimum. It is also believed that the rounded root area 62a aids in maintaining the toothed periphery of the abrading element free of clogging. To further assist in preventing cloggin, the threads may be coated with a release material, such as that sold under the trade mark "Teflon." It has been found that when the angle A is increased in value, the abrading elements have more agressive characteristics with respect to a surface, but that this results in an increased tendancy for heat build-up and clogging of the threads. Furthermore, as the angle A increases in value, the abrading bits have less ability to rotate about their mounting on pins 52. It is believed that a more desirable paint removing action results when the angle A is maintained at a range of 5° to 30°; more particularly 10° to 15°, and is believed that 15° is the optimum value for angle A.
It has been further found that an ideal configuration for the abrading elements or bits 58 is to form the abrading elements with an outside diameter of approximately one-half inch and the full depth of the threads without the rounded root being one-sixteenth of an inch; with the length of pitch being five-eighths inch, and with the threads being formed at 10 threads per inch. In the preferred embodiment, the diameter of the base 34 is approximately 2 1/4 inch and the abrading elements are located on axes spaced 120° apart, as shown. As previously mentioned, the preferable value of the angle A is 15° and as further previously mentioned, if the shaft 36 is to be rotated in a clockwise direction then it is more desirable for the abrading elements 58 to have a left-hand thread while, if the shaft 36 is to be rotated in a counterclockwise direction then a right-hand thread is desirable. In some instances it has been found desirable to provide bits with different thread directions so that at least one bit would have a right-hand thread and at least one bit would have a left-hand thread.
In use, it is intended that the reduced end 42 of the shaft 36 would be secured to the chuck of a power tool such as illustrated hand drill 12. The operator then may control the drill with one hand on the grip thereof, while the other hand is gripped about the handle 14. The tool is placed against a film P of paint over a surface S with the annular skirt 24 in engagement with the surface to be worked. This annular skirt 24 provides a stabilizing effect during the use of the tool, in that it engages a working surface completely about the periphery of the rotating abrading elements. As illustrated, preferably, there is a small amount of slack, or play, between the snap ring 40 and the top of the shroud 16 so thatlimited vertical movement of the shroud relative to the supporting member 32 is permitted. As the power tool is then actuated, the user maintains the skirt 24 in engagement with the working surface through the control afforded by the handle 14. Rotation of the shaft 36 causes the abrading elements or bits 58 to travel in a circular path and at the same time to rotate about their axial mounting on the pins 52. As previously mentioned, this causes the threaded periphery 62 to both, slice into the paint film P, and to further scrape the sliced segments away from the surface S. As further mentioned, the round end corners 64 of the bits 58 and their rounded root structure, as represented at 62b, assist in maintaining the structure free of clogging. The exhaust slot formed at 26 and the outwardly diverging flange 28 permits the scraped or chipped material to be thrust outwardly of the shroud to maintain the area therein relatively free of removed paint and underlying surface material. The tool may be moved about on the work surface by guidance of the handle 14, and the skirt 24 will maintain the abrading element 58 generally in planar engagement against the paint P and surface S. In addition, the skirt 24 serves a protective function when a transverse surface is encountered.
The resultant effect of work with this tool is to rapidly remove loose paint from a surface and to give a feathered effect between the firm, well bonded painted area, and that area of the surface from which the paint has been removed. In preparation of surface for painting, the general desire is to provide a sound surface. In some instances, it may be necessary to use bare wood to provide a sound surface and there may be occassions where, with the use of the tool of this invention, the wood may be lightly roughened. This light roughing may be sufficiently smooth for painting following a light sanding. It is contemplated that the yoke-like mounting arrangement for the abrading bits 58 could be on an adjustable mounting so that the value of the angle A could be changed for optimum performance with different paints or different underlying surfaces. It is further contemplated that bits having different pitch angles or thread configurations could be utilized for giving different results for different paints and different underlying surfaces. This could have an effect similar to changing angle A. This could be accomplished by mounting the bits on a movable or replaceable mounting arrangement. The different bits could be of different pitch, different lead, and different number of threads per inch. It is also contemplated that a flexible driving shaft interconnection could be provided between the hand power tool 12 and the shaft 36 rather than a direct connection as shown herein.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as some modifications may be obvious to those skilled in the art.