US 3029568 A
Description (OCR text may contain errors)
P. LUBAS BELT TENSION AND TRACKING ADJUSTMENT DEVICE FOR PORTABLE BELT SANDERS Filed May 11, 1960 A ril 17, 1962 2 Sheets-Sheet 1 INVENTOR Joseph P Lubas WITNESS April 17, 1962 J. P. LUBAS 3,029,563
BELT TENSION AND TRACKING ADJUSTMENT DEVICE FOR PORTABLE BELT SANDERS 2 Sheets-Sheet 2 Filed May 11, 1960 mm hm P um v51? f :E WU
INVENTOR. Joseph P Lubas ORNEY WITNESS United States Patent Ofiice Patented Apr. 17, 1962 3,029,568 BELT TENSION AND TRAQKHNG ADJUSTMENT DEVICE FOR P DRTAELE BELT SANDERS Joseph P. Lnbas, Linden, NJ, assignor to Diehl Manufacturing Company, onieryiile, Ni, a corporation of New Jersey Filed May 11, 1960, st. No. 23,377 1 Claim. (Cl. 51-470) This invention relates to portable, power-operated, belt sanding machines. It is customarily in machines of this type to have an endless abrasive belt trained over two pulleys. The belt-driving pulley is journalled in the machine frame at the rear end while the idler pulley is journalled at the forward end. A pressure pad is located between the pulleys to provide a fiat platen to maintain the lower run of the belt against the Work being sanded. Due to the requirement of loading and unloading the abrasive belts and also due to the manufacturing variations in the belt structure itself it is necessary to provide mounting structure for the idler pulley whereby it may be shifted into and out of parallelism with respect to the driving pulley and adjusted to provide proper tension and tracking of the belt.
This invention relates more particularly to structure for adjusting the tension and tracking of the abrasive belt of a belt sanding machine and has as an object an arrangement for supporting the idler pulley whereby said adjustments can be made with dispatch and convenience employing simple, readily-assembled structural elements.
With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.
FIG. 1 is a side elevational view of a sanding machine embodying the invention.
FIG. 2 is a longitudinal sectional view, partly in plan, taken on line 2-2 of FIG. 1.
FIG. 3 is a detail perspective view of an essential element of the device of FIG. 1.
Referring to FIG. 1, there is shown a sanding machine comprising an integral frame having a side wall it a top wall 11 and a bottom wall 12. Formed integrally with the top wall 11 is a motor housing 13 having a cover plate 14. A handle 15 is secured to the motor housing 13 and to an end wall portion 16 of the frame.
A driving pulley 17 is journalled in the frame at the rear end'and an idler pulley 18, located at the forward end, is supported by structures about to be described. An endless abrasive belt 19 is trained over the pulleys as shown.
The bottom wall 12 has secured thereto a resilient pad 20, preferably made of cork, and a polished sheet steel ply 21 to form a smooth platen for holding the bottom run of the belt 19 against the work to be sanded.
Referring now to FIG. 2, the pulley 18 is journalled on a pin 22 secured to one end of a gooseneck bracket 23 made preferably of aluminum. A stem portion 24- of the bracket 23, extending essentially at right angles to the axis of the pin 22, carries a transverse pin 25 and is formed at its free end with a step portion 26.
A wear plate 27, made preferably of sheet steel, is bent to conform to the step portion 26 and is secured to the stem portion 24.by means of a drive pin 28. One
end of the wear plate 27 is bent away from the stem portion 24 and is formed with an aperture 29 for receiving one end of a tension spring 30, the other end .2 being anchored by a pin '31 secured in ribs 42 formed on the side wall 10 as shown.
The stem portion 24 of the bracket 23 slides within a channel-shaped sheet metal cam 32 (shown in FIG. 3) which is secured by screws 33 to spaced bosses 34 and 35 formed on the side wall 10. The bracket 23 is guided in its endwise movement by the pin 25 which engages slots 36 formed in the opposed side walls of the cam 32.
An adjusting screw 37, threaded into a boss 38 formed on the side wall 143 has a terminal portion 39 which bears against the wear plate 27 as shown. A bias spring 4i) retains the screw 37 against rotation.
It will be seen that the single spring 36 applies both forwardly-directed endwise and side-wall directed lateral forces to the bracket 23. Looking for removal of the abrasive belt 19 is accomplished'by pushing in on the idler pulley 18 to retractit rearwardly until the for- I ward edge 41 of the wear plate 27 falls over the terminal portion 39 of the adjusting screw 37, as shown in the dotted lines of FIG. 2. This inclined locked posi tion of the pulley 18 facilitates removal of the old belt and installation of a new one.
A cover piece as secured to the top wall 11 and bottorn wall 12, by means of screws id-serves as a stop for engagement with abutment portionjs of the bracket 23 to limit the maximum forward movement of the bracket 23.
To release the idler pulley 2.8 after a new belt has been installed, a side pressure is applied tothe pulley 1% which causes the bracket 23 to pivot about the pin 25 riding in the slots 36. This allows the forward edge 41 of the wear plate 27 to clear the terminal portion 39 of the screw 37, whereupon the spring 30 pulls the bracket forward to establish and maintain tension on the belt 19.
Adjustment of the screw 37 provides the proper positioning of the axis of the pulley 18 to secure proper tracking of the belt 19.
Having thus set forth the nature of my invention, what 1 claim herein is:
In a portable, power-operated sanding machine having an endless abrasive belt, a frame formed with a vertical side wall, a rearwardly positioned pulley for driving said belt, a forwardly positioned idler pulley for guiding said belt, means supporting said idler pulley coma prising vertically spaced-apart bosses formed on said side wall between said pulleys, a channel-shaped cam positioned horizontally between said bosses and secured thereto, parallel slots formed in the horizontal opposing walls of said cam, a gooseneck bracket having a stem portion slidable within said cam, means secured to said bracket journalling the idler pulley thereon, pin means secured to said stem portion in engagement with said slots for guiding said bracket, the free end of the stem portion being formed with a step portion defining a forward edge, a wear plate secured to the stem portion and covering the step portion and the forward edge, single tension spring means secured at one end to said wear plate and at the other end to said side wall for applying forwardly-directed endwise and side-wall directed forces to said bracket, and manually adjustable means secured to said side wall rearwardly of said tension spring to limit the lateral movement of said step portion toward the side wall and to retain the bracket in a rearwardly retracted position for belt removal.
References Cited in the file of this patent UNITED STATES PATENTS