US 2722790 A
Description (OCR text may contain errors)
Nov. 8, 1955 C. M. SMITH PORTABLE SANDING MACHINE Filed April 16, 1954 INVENTOR CARL M. SMITH United States Patent i 2,722,790 PORTABLE SANDING MACHINE Carl M. Smith, Coudersport, Pa. Application April 16, 1954, Serial No. 423,631 1 Claim. (Cl. 51-170) My invention relates to surfacing machines of the portable electric type and more particularly it is intended for the purpose of producing a smooth sanded, rubbed or polished finish on the surface of articles made of wood, metal, plastics and the like.
A general object of the invention is to produce a light weight machine that is easily handled.
Another object of the invention is to provide a new construction for a portable sanding machine where the motion of hand sanding is really imitated. My design permits and is adaptable to a long stroke movement of the sanding pad. Previous machines of this type have used a very short stroke of the sanding pad activated by an eccentric crank arm. My experiments indicate that about four inches is a convenient and eflective length of stroke to imitate hand sanding with a portable machine.
A further object of the invention is to transmit the power of a small electric motor through suitable gearing to a sprocket wheel and chain with a unit attached to it that drives a sanding pad with a reciprocating motion.
Another object of the invention is to provide a means to readily attach or remove interchangeable sanding pads.
A further feature of novelty is the compact construction that brings the center of gravity close to the work surface.
Another desirable feature of the machine is the elimination of any circular or sworl marks remaining on the finished surface of the work. This is due to the straight line back and forth movement of the pad.
A preferred embodiment of the invention is shown in the accompanying drawings.
Figure 1 is a perspective view of my sanding machine. A portion of the front cover is broken away to show the gear transmission.
Figure 2 is a perspective view looking up at the bottom of the machine with the sanding pad removed and part of one guide rod broken away to show the driving chain more clearly.
Figure 3 is an enlarged perspective view of the locking lever that holds the sanding pad.
Figure 4 is a perspective view looking down on the sanding pad when detached from the machine.
As shown in the drawings 1 is an electric motor housing fastened to the base 6 with a handle 2 on the rear of the motor and handle support 3 also fastened to the base. A cover 4 over the gear transmission is fastened to the front of the motor with a hand knob 5 mounted on the cover. The base plate 6 has a flange 7 at the rear end and a flange 8 at the front end. These flanges support the guide rods 9 and 10. A worm 11 on the motor shaft meshes with the worm gear 12 attached to the same axle with the spur gear 13 that meshes with the spur gear 14. The axle of gear 14 extends through the base plate 6 and has the sprocket wheel 15 attached to the lower end. The chain 16 is driven by the sprocket wheel 15 and rotates around the sprocket wheel 17 mounted on the bottom of the base 6. A driving pin 18 (shown by dotted lines) is fastened to the chain 16 and moves the carriage 19 with a reciprocating motion along the guide rods 9 and 10. The driving pin 18 moves transversely in a groove 20 (shown by dotted 2,722,790 Patented Nov. 8, 1955 lines) in the carriage 19 as needed when the chain turns around the sprocket wheels. Figure 3 shows an enlarged view of the locking lever 21 that serves to hold the sanding pad on the carriage 19. The flange 36 on the end of the lever is a finger grip. In Figure 1 the lever is shown in closed position and in Figure 2 the external end of the lever is shown extended while the internal end of the lever is omitted in this view in order to show the recess 22 in the bottom of the carriage 19. The locking lever 21 fits through the two slots 23 and 24 in opposite sides of the carriage 19 and has an opening cut out at 25 to fit over the Tblock 27 and opening 26 that will fit under the top flanges of Tblock 27. Four pins 28 on the bottom surface of carriage 19 fit in the four holes 29 in plate 30 and serve both to locate and drive the sanding pad. The plate 30 has two stud screws 31 and the Tblock 27 fastened to its top surface and a layer of felt 32 fastened to its bottom surface. The height of the Tblock 27 is made so that it will create spring tension in the locking lever 21 when the opening 26 slides under the top flanges of the Tblock in closed position of the lever and thereby hold the sanding pad in place under the reciprocating carriage 19. The sanding pad is readily removed by pulling the lever 21 outward to where the opening 25 slides over the top of the Tblock. A strip of sanding paper 33 wrapped around the pad is held at each end by the two clamp blocks 34 and the two knurled edge thumb and finger nuts 35 that are threaded to fit on the screw studs 31.
This description is given to explain the operation of my sanding machine as shown in the drawings, but is not intended to limit the design of the various parts. Some deviation of details will be apparent without departing from the scope of the invention.
A hand supported and directed sanding machine comprising a housing frame containing a driving motor with a handle at the rear and a gear housing containing gears at the front with a hand knob on the top of said gear housing; said driving motor housing, handle and gear housing mounted on a base with two parallel guides mounted in a longitudinal position under the base; a driving connection from the motor through reduction gears to a sprocket chain, said chain adaptable to various lengths as predetermined by the spacing of two sprocket wheels attached under the base of said machine; a driving unit fastened to the sprocket chain that slidably engages a transverse slot in a reciprocating carriage supported by and free to move longitudinally along said guides; said reciprocating carriage provided with locating pins to position a sanding pad and provided with a slidable latch to hold a sanding pad; a detachably mounted sanding pad comprising a metal backing plate with flexible material secured to the bottom of said plate and two stud screws mounted on the top side near each end of said plate and a projection mounted on the plate to engage with said slidable latch and two clamp blocks to hold the ends of a strip of sand paper wrapped around the sanding pad, said clamp blocks manually actuated by a thumb and finger nut on each screw stud.
References Cited in the file of this patent UNITED STATES PATENTS 1,761,059 Van Norman June 3, 1930 2,156,798 Bangser May 2, 1939 2,395,537 Crosby Feb. 26, 1946 2,417,680 Decker Mar. 18, 1947 2,488,098 Peterson Nov. 15, 1949 2,492,231 Mandl Dec. 27, 1949 2,582,470 Walker Jan. 15, 1952