ABSTRACT    A sanding machine for sanding the surfaces of work pieces placed upon a conveyor that transports the work pieces along a first direction towards and beneath a sanding head。 The sanding head comprises a sanding belt entrained around an upper tension roller and a lower contact roller。 The tension roller and contact roller are provided with a single translational orbital movement by a pair of eccentric shafts operatively connected thereto and rotatably driven by an operatively connected motor。 At least one of the upper tension roller and lower contact roller is also driven by an operatively connected motor so as to provide the endless rotation of the sanding belt around the upper tension roller and lower contact roller。 In this fashion, the sanding belt is provided with two contemporaneous superimposed movements consisting of rotational movement about the tension roller and contact roller and a single orbital translational movement imparted by the rotating pair of eccentric shafts。 The resulting sanding pattern is homogeneous and renders scratches normally created by the endlessly rotating sanding belt substantially unnoticeable。 Asecond embodiment incorporates an arcuate plate in lieu of the upper roller of the sanding head。84447

27 Claims, 3 Drawing Sheets

BELT SANDER WITH ORBITALLY  TRANSLATED ABRASIVE BELT

RELATED APPLICATION

This application is a continuation-in-part application of U。S。 Ser。 No。 09/311,096 entitled “Belt Sander with Orbitally Translated Abrasive Belt” filed May 13, 1999, and now U。S。 Pat。 No。 6,089,958。

TECHNICAL FIELD

The present invention relates generally to machines for abrading material and, more particularly, to an improved sanding machine for providing an enhanced finish on work pieces。

RELATED ART

Motorized sanding machines have been used for many years to sand the upper and lower surface of wooden work pieces that are conveyed along a movable conveyor forming the worktable of the sanding machine。 These motorized sanding machines will typically utilize a wide sanding belt that is entrained around vertically spaced rollers。 A limitation to these sanding machines is that they will often leave cross-grain scratch patterns in the sanded surface of the wooden work piece that results in an unattractive and perhaps unacceptable finish in the work piece。 A further problem relates to movement of the work piece induced by the rotational movement of the rotating sanding belt of the sanding head。 Mechanized hand sanders have been used in order to provide an acceptable finish on wooden work pieces, but the sanding operations are highly labor intensive and expensive。

Further, wide belt sanding machines with orbiting abrasive belts are well known to those skilled in the art。 Representative wide belt sanders are shown in U。S。 Pat。 No。 3,832,807 to Kaiser et al。 and U。S。 Pat。 No。 4,719,721 to Stump。 Generally, in this type of sanding apparatus, one or more (and typically two) inpidual sanding heads are utilized wherein each employs an endless wide abrasive belt entrained over inpidual rollers or drums。 At least one of the rollers or drums is power driven to impart a high speed orbital motion to the abrasive belt。 Generally, two inpidual sanding heads arranged in tandem are provided wherein each is disposed vertically above a horizontal conveyor so as to provide operative contact between the upper surface of work pieces being fed through the machine and the surface of the abrasive belt。 Further, the first sanding head is typically in the form of a contract drum for dimensioning at the drum stage and the second sanding head is in the form of a platen wherein the finishing occurs at the platen station。

Another type of sanding machine is disclosed in U。S。 Pat。 No。 4,742,650 to Sauder, Jr。 et al。 which provides a sanding machine for sanding the surfaces or work pieces placed upon a conveyor that transports the work pieces in a first direction wherein each of two sanding heads is oscillated at two different frequencies relative to the work pieces on the conveyor。 The first oscillating frequency orbits the sanding heads in a circular motion over the work pieces on the conveyor, while the second oscillating frequency (which is greater than the first frequency) results in a vibration of the inpidual sanding elements engaging the work pieces。 The double orbital motion sanding machine disclosed in the patent includes a plurality of sander elements transversely spaced above the conveyor, and the sander elements of first sanding head are staggered with respect to the sander elements of the second sanding head。 This type of sanding apparatus, however, while useful for many purposes is not as effective for sanding certain types of work pieces as the rotating endless belt sanding head-type of sanding machine。