BACKGROUND AND BRIEF SUMMARY OF INVENTION
The invention relates generally to abrading tools, specifically, tools wherein a sanding pad is mounted on an extension handle and incorporating a means for vacuum assisted removal of abraded particulate. In particular, the present invention includes a sanding pad which provides laminar flow by supporting a sanding screen with a plurality of pegs, and thereby avoids the use of a plenum chamber supporting the sanding screen with flow restrictive members. The present invention provides an actuated or floating hose junction which allows the sanding pad greater freedom to rotate while keeping the sanding screen fully in contact with the surface being sanded.
The design of an efficient, effective vacuum pole sander requires consideration of several factors. The angle, between the sanding surface and the extension handle, is continuously adjustable through a sufficient range to enable the operator to sand a wide area of the work surface without changing locations. A symmetrical continuous air flow over the surface of the sanding pad is required to comprehensively draw the abraded particulate into the air stream. Additionally, an unobstructed, unconstricted passageway is required to transport the particulate toward the vacuum source.
The methods and means the prior art has used to address these factors are varied. Previous designs of vacuum pole sanders have engineered structure in attempts to solve flow dynamic inefficiencies. In many instances, the additional structure has restricted the range of motion of the sanding pad assembly, increased the air flow inefficiencies and reduced the durability of the design. Vacuum pole sanders, such as Reiter U.S. Pat. Nos. 4,964,243 and 4,779,385, which have incorporated plenum chambers, obstructions, or constrictions, that increased turbulence and reduced the efficiency of the air stream, are typical of the prior art.
Examples of vacuum pole sanders with a single vacuum hose attached between the sanding pad assembly and the tubular handle are of two basic types.
The first type is exemplified by Walters U.S. Pat. No. 5,036,627, Mehrer U.S. Pat. No. 4,062,152, and Brown U.S. Pat. No. 5,624,305; each of which encloses the universal swivel in an elastomeric boot and draws the particulate-laden air stream around the swivel. The abrasive nature of the particulate causes premature wear of the universal swivel. The unnecessary obstruction contributes to turbulence, reducing the efficiency of the air stream.
The second type, exemplified by Sanchez et al U.S. Pat. No. 5,193,313, disposes the vacuum hose along the linear axis of the base plate, a predetermined distance from the universal swivel. The vacuum hose enters the tubular handle laterally, bypassing the universal swivel. This type inherently has an asymmetrical air flow pattern across the planar surface of the sanding pad, and an asymmetrical range of motion of the sanding screen in relation to the tubular handle.
Some previous examples of vacuum sanders have dual vacuum hoses to improve the symmetry of the air flow across the sanding pad (see Paterson U.S. Pat. No. 5,007,206 and Thayer U.S. Pat. No. 5,540,616). The vacuum hoses are attached a predetermined distance from the end of the tubular handle, and disposed diametrically. When a short side of the rectangular sanding pad assembly is moved toward the tubular handle, the vacuum hose is compressed between the tubular handle and the sanding pad assembly. This restricts the range of motion of the sanding pad assembly.
Prior examples have not achieved laminar flow of the air stream through the tool. All have incorporated plenum chambers, with a plurality of apertures in fluid communication with the planar surface of the sanding pad, in an effort to improve the flow pattern. For example, the Reiter U.S. Pat. No. 4,964,243 requires the use of peripheral supports 24, which restrict incoming air flow and cause turbulence. According to fundamental fluid dynamic principals involving fluid moving through a pipe; as velocity increases, turbulence increases. A fluid in motion loses more energy to the effects of friction in turbulent flow than in laminar flow. The present invention achieves laminar flow through the sanding head by supporting the sanding screen without the use of flow restricting supports.
Chambers, obstructions, and constrictions disrupt the parallel streamlines of laminar flow and generate turbulence in the air stream. The path of each particle becomes unpredictable, energy is lost to heat as the particles increasingly collide with each other, the walls of the passageway, and any obstructions in the air stream.
When an air stream is moving through a pipe, a localized area of reduced vacuum is created in a chamber, in relation to the air stream, by limiting the area of the inlet apertures to less than that of the area of the outlet portal(s). The effect of the air stream moving through constricting apertures is to locally accelerate the air stream (velocity is inversely proportional to cross-sectional area), creating localized turbulence. Plenum chambers, obstructions, and constrictions reduce the efficiency of the air stream by disrupting the streamlines of laminar flow and generating turbulence. As the velocity increases, turbulence increases, reducing the efficiency of the system. Obstructions reduce efficiency by physically disrupting the streamlines and creating turbulence as the air stream is forced around the obstructions.
Various methods and means used in the prior art to improve the flow dynamics have restricted the articulation of the sanding pad assembly, reduced the efficiency of the air stream, added manufacturing costs, and reduced the structural integrity and durability of the devices. The applicant believes that inefficiencies in design of the prior art have undermined the confidence of manufacturers and consumers, and is a factor why a tool with such significant benefits is not in common use by professional tradespeople.
During the sanding process of finishing drywall, the operator is often required to sand in hallways, closets, and under stairways. The range of motion between the sanding pad and the handle of the sanding pole must be comprehensive enough to allow the operator to maintain planar contact between the sanding screen and the work surface while working in confined areas.
The present invention provides an actuated, bifurcated vacuum hose junction for a vacuum pole sander. The pole sander includes a sanding pad assembly, a bifurcated hose junction assembly, and a tubular handle assembly. The hose junction is actuated by the movement of the sanding pad in relation to the tubular handle. The hose junction is designed to “float” and is displaced when the sanding pad is moved toward the handle, allowing the operator to close the angle between the pad and the handle, and maintain contact between the sanding screen and the work surface when working in confined areas.
The sanding pole of the application achieves laminar flow through the w sanding head by providing an unobstructed passageway for the air stream. The passageways extend between upstanding support pegs that carry the sanding screen. This design reduces turbulence, conserving the energy available to the system, and maintaining the efficiency of the air stream to transport the abraded particulate to the vacuum source. The operator is free to urge the sanding screen along the work surface, at pace appropriate to the time constraints of the job, without loss of effective particulate removal.
Generally, it is applicant's objective to provide drywall professionals a vacuum pole sander designed well enough to come into common use, by intuitively instilling confidence in the tool's functionality and durability. The sander of the present invention is physically robust enough to provide years of regular professional service. It collects more dust, providing a healthier environment and an advantage over competitors' sanding equipment.
Specifically, it is applicant's objective to provide a pole-mounted vacuum sanding device that maintains an air stream in laminar flow and to transport abraded particulate to a waste receptacle. Additionally, it is applicant's objective to maximize the practical range of motion between the sanding screen and the tubular handle to a range nearly as great as in a conventional pole sander that does not incorporate vacuum-assisted particulate removal. Further, it is applicant's objective to provide a simple, robust design, that can be manufactured economically, and intuitively instills manufacturer and consumer confidence in the functionality and durability of the invention.
When a short side of the sanding pad is moved toward the tubular handle, the present invention displaces the bifurcated hose junction laterally in relation to the linear axis of the tubular handle. When a long side of the sanding pad is moved toward the tubular handle, the hose junction is rotated in place on the tubular handle. This range of motion of the hose junction enables the present invention to incorporate a more comprehensive, symmetrical range of motion between the sanding pad assembly and the tubular handle than the prior art.
More energy is lost to the effects of friction in turbulent flow than in laminar flow. Work is defined as energy inversely proportional to area. If energy is increased and the area over which it is applied remains constant, then work is proportionally increased. Therefore, a fluid in laminar flow has more energy available to do work. A passageway is provided for the air stream without unnecessary chambers, obstructions, or constrictions. The resulting laminar flow of the air stream through the present invention conserves the energy available to the system. As more energy is available to the air stream at the sanding screen, the effective removal of abraded material is increased. Alternatively, the speed of the sanding screen across the work surface can be increased without loss of effectiveness, thereby reducing the time spent on the sanding process.
The present invention incorporates fewer, more robust parts than the prior art. This design reduces manufacturing costs and processes, and increases durability and consumer confidence.
The pad assembly 12 (FIG. 5) includes a flexible sanding pad 18 having a plurality of elongated, cylindrical pegs 20 molded perpendicular to a rectangular planar surface of the pad 18, preferably, an abrasion-resistant, elastomeric-polyurethane composite. The pegs 20 support a conventional sanding screen a predetermined distance from the pad 18. The pad 18 is mounted directly to a rigid, preferably cast aluminum, base plate 22 by a suitable adhesive. The pad 18 has first and second vacuum portals 24, 26 that are aligned with first and second vacuum portals 24 a, 26 a, respectively (not shown), in the base plate 22. First and second tubular flanges 28, 30 extend from the base plate at the first and second vacuum portals 24 a, 26 a, respectively (not shown). Conventional sanding screen clamps 32 are mounted proximal to the short sides, and perpendicular to the linear axis of the base plate 22. The sanding screen clamps 32 comprise a “U” shaped metal channel held to the base plate 22 by wing nut 34 on machine screws 36 mounted to the base plate 22. The universal joint 38 is of conventional design and includes a threaded shaft 40 and two orthogonally disposed pivot axes 42, 44, respectively. The axes 42, 44, allow the angle between the sanding screen's planar surface and a tubular handle 46 to be continuously adjustable over a predetermined range. The universal joint 38 is attached to the base plate 22 by a roll pin 46 through the pivot axis 44 disposed orthogonally to the linear axis of the base plate 22. Each end of the roll pin 46 is friction fit into a first and second aperture 48, 50, in a first and second ridge 52, 54, respectively, cast into the base plate 22.
The tubular handle assembly 16 (FIGS. 6 and 7) includes a tubular handle 78, a coupler nut 80, an inner and outer spacer 82, 84, respectively, a pipe connector 86, and a swivel hose connector 88. The tubular handle 78, preferably aluminum, includes a distal closed end that extends to pad assembly 12, a vacuum portal , and a proximal open end. The pipe connector 86 (FIG. 6) is a predetermined distance from the distal closed end of the tubular handle 78. Vacuum portal 90 is aligned with the vacuum portal in the tubular handle 78. The flange 74 is removably inserted into a vacuum portal 90 in pipe connector 86 which is connected to the tubular handle 78 by a suitable adhesive. The vacuum portal 76 of the pipe connector 64 is aligned with the portal in the tubular handle 78 and establishes a fluid communication between the hose assembly 14 and the handle 78. The universal joint 38 (FIG. 5) is removably attached to the tubular handle 78 by means of a conventional coupler nut 80 (FIG. 6). The coupler nut 80 is held centered in one end of the tubular handle 78 by an inner spacer 82 and an outer spacer 84, preferably nylon, The coupler nut 80 is attached to the tubular handle 78, preferably by a suitable epoxy. When the coupler nut 80, the inner and outer spacers 82, 84, respectively, and the threaded shaft 40 of the universal joint 38 are in place, the end of the tubular handle 78 is effectively sealed. The open end of the tubular handle 78 is connected to a conventional swivel hose connector 88 (FIG. 7) by a suitable adhesive. The swivel hose connector 88 includes a pipe coupler 94, modified with interior grooves 96, and a coaxially disposed rigid tube 98, with external ridges 100 aligned to fit into the grooves 96 in the pipe coupler 94. The grooves 96 and ridges 98 retain the tube 98 in the pipe coupler 94 while allowing the tube 98 to rotate around its linear axis. The swivel hose connector 88 allows the vacuum sanding pole to be attached to a vacuum source (not shown). The hose junction 60, pipe coupler 94 and connectors 64, 86, respectively, preferably are a polyvinylchloride composition.