US3049840A

US3049840A - Sanding tool

Info

Publication number: US3049840A
Application number: US52908A
Authority: US
Inventors: George L Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-08-30
Filing date: 1960-08-30
Publication date: 1962-08-21
Anticipated expiration: 1979-08-21

Description

Aug. 21, 1962 G. L. WILLIAMS SANDING TOOL Filed Aug. 30, 1960 INVENTORQ" L.W L ai GEORGE 31 United States 3,049,840 SANDING TOOL George L. Williams, 250 th St., Santa Monica, Calif. Filed Aug. 30, 1960, Ser. No. 52,908 3 Claims. (Cl. 51-147) This invention relates generally to woodworking apparatus and more particularly to an improved power sanding tool preferably designed for home or relatively small work shops for both rough and fine finishing of woodworking surfaces.

Conventional power operated sanding tools suitable for small work shop use are generally of two types. First, the disc sander in which a circular disc having one flat surface covered with sandpaper material is caused to rotate at high speeds. Second, the belt sander in which a continuous belt is wrapped about spaced parallel rollers and caused to move continuously in one direction. Both types of power operated sanders have certain advantages peculiar to their particular construction. On the other hand, the very nature of their design is such that considerable skill is required for finishing relatively large, flat smooth surfaces.

In disc type sanders, for example, the outer peripheral surface portions of the sandpaper disc will move faster than the inner portions and thus tend to effect more ma terial removal than the inner portions unless careful compensating movements are made. In the case of belt sanders, the weight of the motor driving the belt is usually employed for providing pressure between the sandpaper itself and the work. The user must thus carefully guide and control the belt sander as otherwise it will tend to run away. The restraining action required on the part of the operator tends to result in the development of uneven pressures applied by the various areas of the belt surface.

With all of the foregoing in mind, it is a primary object of this invention to provide a greatly improved power operated sanding tool in which many of the above difliculties are overcome.

More particularly, it is an object to provide an improved power operated sanding tool for finishing surfaces in which a high degree of controlled and uniform pressure may be realized without requiring excessive skill on the part of the operator to the end that very uniformly sanded surfaces result.

Another important object is to provide an improved power operated sander which is designed for sanding relatively large surface areas such as table or desk tops, all in an automatically controlled manner so that substantially uniform material removal is achieved over the entire surface to be worked.

Briefly, these and many other objects and advantages of this invention are attained by employing a basic belt type sander unit in combination with a work table structure. In accordance with the invention, the work table is provided with a cutout in its work surface. The belt sander in turn is movably coupled to the under side of the table and arranged to be moved partially through the cutout so that the upper sanding surface of the belt itself is generally parallel to the top surface of the table and extends slightly above the top surface. Suitable spring type biasing means are employed to bias the sanding belt structure to this latter position. A suitable motor secured to the under side of the table is coupled to the sander to drive the belt.

With the above arrangement, a flat surface to be sanded may be inverted and placed on the top flat surface of the table itself over the cutout portion. The work will thus depress the sanding belt surface slightly until it assumes a flush position with the top surface of the table.

3,049,840 Patented Aug. 21, 1962 The actual sanding operation is effected by the operator moving the entire work over the top surface of the table rather than attempting to manipulate the power sander itself. Thus, uniform pressure between the sanding belt and surface to be sanded is always insured. As a consequence, material removal is uniform over the particular area of the surface being sanded.

In accordance with a feature of the invention, there is also provided a foot operated control pedal coupled to the sanding belt structure enabling the operator to depress the sander to move it from the cutout as desired so that careful control of the sanding operation is realizable at all times.

A better understanding of the invention will be had by now referring to the preferred embodiment thereof as illustrated in the accompanying drawings, in which:

FIGURE 1 is an enlarged cutaway perspective view of the improved sanding tool of this invention; and

FIGURE 2 is a front elevational view considerably reduced in scale of the sander shown in FIGURE 1.

Referring to FIGURE 1, the sanding tool comprises a work table 10 having a fiat surface including a generally rectangular cutout 11. Coupled to the under side of the table is a sanding belt structure including a sanding belt 12, the upper surface of which is arranged to extend through the rectangular cutout 11 as shown. Belt 12 is supported by a suitable mounting structure including spaced

parallel rollers

13 and 14 generally co-extensive with the width of the belt 12 and with the transverse opposite edges of the cutout 11. The arrangement is such that rotation of the rollers will cause the belt 12 to move in a direction parallel to the longitudinal edges of the cutout.

The mounting structure further includes frame means supporting the

rollers

13 and 14 and including flat frame plates 15 secured to

suitable support bars

16 and 17 extending horizontally beneath the table towards the rear edge of the table as shown. The ends of the support bars terminate in a shaft 18 having ends respectively journaled within

suitable brackets

19 and 20 secured to the under side of the table. The entire sanding belt mounting means can thus pivot about a horizontal axis A coincident with the axis of the shaft 18 from a position in which the belt is disposed below the table surface free from the cutout 11 to a position in which the top surface of the sanding belt is substantially flush with or even extends above the work surface of the table.

Drive power for the sanding belt 12 may be provided through a shaft extension 13' connected to the roller 13 and terminating in a suitable drive pulley structure 21 supported to the side of the bar 16 as at 22 Preferably, the pulley 21 is disposed relatively close to the horizontal pivot axis AA so that it will exhibit minimum movement during pivoting action of the entire frame structure.

The drive pulley 21 is connected through a drive belt 23 to a power pulley 24 driven by a suitable motor 25 secured to the under side of the table as by a flange 26. The drive belt 23 constitutes, in essence, a flexible coupling between the motor and the pulley 21 and will accommodate a slight twisting resulting from pivoting movement of the belt structure about the shaft 18.

The sanding belt is normally biased to a position extending partially through the cutout 11 by means of a central downwardly extending flange 27 having secured to its lowermost

tip biasing springs

28 and 29 as shown best in FIGURE 2. The other ends of the

biasing springs

28 and 29 are secured to the under side of the table as at 30 and 31 so that they will exert an upward component of force on the pivoted structure. Also connected to the downwardly extending flange 27 is a line or chain 32 connected to a foot-operated pedal 33 so that an operator by depressing the pedal 33 may pull the pivoted structure downwardly against the force exerted by the

biasing springs

28 and 29.

The operation of the improved sanding tool of this invention will be evident from the foregoing description. Initially, an operator may depress the pedal 33 and thus pivot the entire sanding belt structure about the shaft 18 so that the top surface of the sanding belt 12 is below the level fiat working surface of the table 10. A work to be sanded, such as the top surface of a table or desk, is then inverted and placed on top of the work table to cover the cutout 11. The operator may then start the motor 25 and through the medium of the flexible belt 23 drive the sanding belt 12. Gradual release of pressure on the foot-operated pedal 33 will then result in the

biasing springs

28 and 29 urging the sanding belt upwardly through the cutout to engage the work to be sanded. The pivoting of the structure is such that the top surface of the sanding belt will be substantially parallel with the top surface of the work table so that the entire exposed area of the belt will engage uniformly the work to be sanded.

The weight of the work to be sanded will be borne principally by the top surface of the table 10, the only pressure between the sanding surface of the belt 12 and the work being provided by the tension biasing

springs

28 and 29. This work pressure will be substantially uniform, and thus even sanding takes place.

In the actual sanding operation, the entire work is continuously moved over the flat surface table 10 preferably in a circular motion maintaining the grain substantially parallel to the direction of motion of the belt until all of the surfaces have been exposed to the sanding belt 12. Because of the relatively high speed of the belt compared to transverse movements of the work during the circular motion, the sanding direction is still maintained substantially parallel to the grain.

While it will be evident that equivalent results could be achieved by mounting the sanding belt structure for translational movement rather than pivoted movement, the latter arrangement results in a far simpler sructure. It is important, however that in this latter structure the pivoting be relatively remotely located from the sanding belt such as shown in the illustration of FIGURE 1. By providing a relatively large distance between the pivoting axis and the actual sanding belt, the small degree of arcuate movement of the sanding belt to bring the sanding surface flush with the table top results in an operation substantially equivalent to a direct up and down translation of the sanding belt. In an actual embodiment, the mounting of the backing plate for the sanding belt is made sufficiently resilient to accommodate any slight angular misalignment of the top surface of the belt with respect to the flat surface of the work engaged thereby.

Thus, while only one particular embodiment of the invention has been set forth and described, many changes and equivalent means for carrying out similar functions will occur to those skilled in the art, such changes and equivalent structures falling clearly within the scope and spirit of this invention. The improved sanding tool is therefore not to be thought of as limited to the particular example set forth and described in FIGURES l and 2.

What is claimed is:

1. A power sanding tool comprising, in combination: a work table having a substantially rectangular shaped cutout in its upper surface; a continuous sanding belt; mounting structure for said sanding belt including: spaced parallel rollers for supporting and moving said belt, said rollers being positioned adjacent to and substantially coextensive with the opposite transverse edges of said cutout respectively for moving said belt in a direction parallel to the longitudinal edges of said cutout; frame means rotatably mounting said rollers and extending substantially horizontally under said table towards the rear of said table; pivot means connecting said frame means to the under side of said table for swinging movement about a horizontal axis substantially parallel to said longitudinal edges of said cutout; a motor secured to the under side of said table; flexible means coupling said motor to at least one of said rollers for driving said sanding belt; and biasing means connected between said frame means and said table for urging said rollers and sanding belt upwardly into said cutout so that the upper surface of said sanding belt is positioned above the surface of said table whereby a work to be sanded positioned on said table over said cutout will depress said sanding belt to a position in which its upper surface is substantially flush with the surface of said table.

2. A power sanding tool according to claim 1, including a foot operated pedal means connected to said frame means for applying a downward pull on said frame means to lower the surface of said sanding belt to a position below the surface of said table.

3. A power sanding tool comprising, in combination: a work table having a cutout in its upper surface; a continuous sanding belt; spaced parallel rollers for supporting and moving said belt; frame means supporting said rollers; pivot means pivoting said frame means to the under side of said table so that said rollers and sanding belt are swingable as a unit with said frame means from a position below said cutout upward into said cutout to a position in which the upper surface of said sanding belt is above the surface of said table; biasing means connected between said table and said frame means for urging said frame means upwardly; a motor secured to the under side of said table; and a pulley belt for transmitting power from said motor to one of said rollers.

References Cited in the file of this patent UNITED STATES PATENTS