US 2751725 A
Description (OCR text may contain errors)
June 26, 1956 R. J. CHAMPAYNE 2,751,725
ORBITAL ACTION RUBBING MACHINE 3 Sheets-Sheet 1 Filed Aug. 13, 1954 June 26, 1956 R. J. CHAMPAYNE 2,751,725
ORBITAL ACTION RUBBING MACHINE Filed Aug. 15, 1954 3 Sheets-Sheet 2 TNVC-MTOM @945 w. ckqwu obme e awe, Pa a/9 W @4' J1me 1956 R. J. CHAMPAYNE 2,751,725
ORBITAL ACTION RUBBING MACHINE 3 Sheets-Sheet 3 Filed Aug. 13. 1954 "ilk pckq c 'kQ [a 5 (jaw-roman United States Patent ORBITAL ACTION RUBBING MACHINE Roy J. Champayne, Rockford, Ill.
Application August'13, 1954, Serial No. 449,690
3 Claims. (Cl; 51-170) This invention'relates 'to' rubbing-machines of the type disclosed in my Patent 2,367,663 in which the rubbing shoe is gyrated'by rotation of a .drive shaft and efficient cutting by the abrasive particles is achieved by counterbalancing of the eccentric shoe mass by weights fixed to the drive shaft.
The primary object is to provide an improved counterbalancing system for a rubbing machine of the above character so as to facilitate accurate counterbalancing of the shoe by a single weight advantageously located in an out of the way position which increases the vertical compactnessof the overall machine structure.
A more detailed object .is to provide a generallyflat rubbing shoe whose center of mass is disposed close to the top of the shoe anditofixthe single counterweight to the drive shaft immediately below the gyrating eccentric and in a recess. disposed within the shoe structure and in the plane in which saidtrnass center 'gyrates.
Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a fragmentary elevational view of a rubbing machine embodying the novel features'of the present invention and partially broken away along the line 11 of .Fig. 4.
Fig. 2 is a fragmentary perspective view looking toward the. bottom of the rubbing shoe with part of the latter broken away.
Fig. 3 is a fragmentary section taken along the line 33 of Fig. 1.
Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3.
Fig. 5 is a fragmentary perspective view of the counterweight and shoe gyrating crank.
Fig. 6 is a view similar to Fig 1 showinga modified form of the invention.
Fig. 7 is a section taken along the line 77 of Fig. 6.
Fig. 8 is a fragmentary view similar to Fig. 1 showing a further modification.
Referring first to the form shown in Figs. 1 to 5, the invention is there shown incorporated in a portable rubbing machine driven by a rotary motor 10 housed within a hollow frame or casing 11 on which a rubbing shoe 12 is supported for bodily. gyration. The'frame casing is generally dome shaped and formed on opposite sides with a handle 13 and a knob 14 which may be gripped to carry the tool, to guide it alonga work surface, or to apply the necessary downwardpressure on the shoe.
The stator of the motor lll which may as shown he of the electric type, is secured within the casing il'with its shaft 15 projecting through the center of a bottom plate 16 and journaled in a bearing 17 supported by the latter. The plate, which is secured to the open bottom of thecasing, cooperates with a second plate 18 secured thereto by screws 19 to formialubricant tight recess 20- for a speed reduction'connection between-the motor shaft ice and a parallel shoe gyrating shaft 21 which projectsdownwardly through the plate Band is journale'd 'at its upper end in a bearing 22 mounted in the plate 16. Intermediate its ends, the shaft21 is journale'd in a rugged antifriction thrust bearin'g'23 whose. inner race ring is pressed into the shaftvand whose outer ring is clamped between spaced shouldersv 24 on the plate In this instance, the speed reducing-connectionds comprised of a pinion 25 on the motor shaft and a spur gear '26 on the shaft 21.
The rubbing shoe 12 comprises a-pad 26'of yieldab'lematerial such as rubber adhesively secured to "a very thin metal sheet 27 which in turn is detachably securedas'by screws 27 to the bottom of a plate like casting 28. of-
light weight metal. One or more abrasive-sheets 29 are stretched around the bottom of the pad andfastenedat opposite ends by suitable clamps 30'mounted on top of the plate 28 at opposite ends thereof.
Upstanding from the central part of the plate 28 and formed integral therewith is a boss 31 terminating in an annular flange 32 in which is-disposed an antifriction thrust bearing 33 whose outer race ring is supported on a shoulder 35' within the flange and fastened to the latter by a clamping ring 34. An eccentric 36is pressed through the inner race ring 33 with a shoulder 37 thereon abutting against the lower end of the ring and its upper end abutting against the inner race of the bearing 23. The eccentric is keyed onto the downwardly projecting end of the shaft" 21 and its axis is oflset from the shaft su'fiicientlyto provide. the desired radius of gyration' oftherubbing shoe 12, usually about 5 of an inch.
The shoe is held against turningduring its gyration by any suitable means which-may comprise a flexible shirt 39 encircling the shouldered-periphery 49 of the boss 31 which is preferably ofelliptical shape with the major axis extending longitudinally of the shoe 12. Atits upper end, the skirt fits over a shoulder 41 on thecasing plate 18 and is fastened by ansencircling band 42.
With the construction above described, it will be apparent that the inner bearing race 38 'rotateswith the.
driven shaft 21 and, because of itseccentric mounting, gyrates in a circle.
of the inability to locate the counterweight" close to therubbing shoe proper or because of the-necessity of employing a second weight to overcome the force couple resulting from improper location zof vthe primary counter Weight.
The present invention overcomes these objections by employinga singlerotating counterweight: 44 astdistin guished from a gyrating weight-and by rearranging' the parts of the rubbing shoe and distributing theirmasses:
so that the weight may be located close to but above the'top of the 'pad 26 and turn innaniorbitof large radius lying in a plane which includes the center of gravity of. the rubbing shoe. Thus, the'weight'44-is fast'oruthe' lower end of the shaft 21and rotates .in a circularrecess.
46. cored out of the shoe casting ZS'andeXtendingsub stantially to .the bottom of the latter:
To locate the center of. gravity of I the shoet close to Since this ring is connected to the rubbing shoe 12 through the bearing 23 and sinceth-e 7 shoe .is held against turning, it and all of the parts sup-- ported thereby will gyrate bodily in the same circle but above the pad 26, advantage is taken of the substantial mass of 'the clamps 30 and the bearing 33 which are spaced above the plate 28 so as to partially offset the mass of thepad 26. The center of gravity is thus raised into a plane 45 which coincides with the plane of the plate 28 whose weight is thus equally divided above and below the center of gravity of the shoe. Ample space 46 for the counterweight may thus be provided within the plate 28 and its boss 31. The weight may be made relatively thin because of the comparatively large horizontal area which is available owing to the substantial width of the abrasive sheet backing 26. That is to say, since the counterweight is fixed to the shaft 21 and thus disconnected from all other parts and at the same time is located remotely from the operating parts and their supporting bearings, the recess 46 in which the weight turns may be nearly as wide as the supporting plate 28. With the center of the mass of the weight at such a large radius, the moment of inertia required in order to balance that of the gyrating shoe mass may be obtained with a comparatively thin and flat weight made of generally semicircular shape as shown in Fig. 2.
With the weight thus located, it is only necessary to counterbalance the shoe statically which is accomplished simply by choosing a counterweight whose moment of inertia is equal to that of the rubbing shoe and by locating the centers of gravities of the two masses in a common plane. Moreover, since the counterweight is very thin and disposed within the rubbing shoe itself, the overall vertical dimensions of the rubbing machine are minimized, and the construction as well as its assembly are greatly simplified as compared with prior constructions.
The counterbalancing system above described may be used in other rubbing machine structures of the above general character in order to achieve overall vertical compactness and eflicient cutting action by insuring gyration of the abrasive particles in true circular orbits. In the modification shown in Figs. 6 and 7, the parts of the shoe gyrating and counterbalancing mechanism are indicated by corresponding reference numerals. The crank shaft 21 projects rigidly from the rotor 50 of the motor which may be of the pneumatic type and actuated by pressure fluid delivered through a manually operable control valve 51. The rubbing shoe is held against turning during its gyration by a plurality of posts 52 composed of yieldable material such as rubber and fastened at their lower ends to bosses 53 on the top of the plate 28 and at their upper ends to similar bosses 54 depending from extensions 55 of the upper end plate of the pneumatic motor 10. The posts are spaced angularly around the motor axis and may be used to perform the additional function of transmitting to the motor frame 11 the thrust applied to the shoe.
Various other means may be provided for restraining the rubbing shoe from turning during its gyration and for sustaining the thrust resulting from pressing the shoe against the work. In the form shown in Fig. 8, the latter function is performed by a series of balls 56 held within a cage 57 which encircles the boss 32 by which the cage is held in. centered position. On their upper and lower sides the balls bear against opposed surfaces on extensions of the plates 18 and 34 above described.
1 The :use of a single counterweightand its mounting close toLthetop of theplate 28 where the massof the gyrating parts is centered is made possible not only by the use of a rotary weight 44 to effect the counterbalance I but also by location of the weight within the shallow recess 46 disposed below the eccentric 36 and its bearing and in a plane' close to the top of the platewhich forms the frame of the rubbing shoe.
required in order to achieve precise counterbalancing of.v
the shoe and therefore gyration'of the abrasive particles one end projecting from the bottom of said frame, a
rubbing shoe including a top plate and a pad of yieldable material secured to the bottom of said plate for attachment of a rubbing sheet thereto, said shoe and the parts thereon having a center of mass disposed closely adjacent the plane of said plate, means joining said frame and plate and acting to hold said shoe against rotation but permitting bodily gyration thereof around the shaft axis, a flange rigid with and upstanding a short distance from the top of said plate, a bearing supported in the upper part of said flange, an eccentric on said shaft disposed immediately below said frame bottom and journaled in said bearing whereby to gyrate said shoe and its center of mass in said plane, said flange and plate defining around the lower end of said shaft below said bearing a generally flat annular enclosure disposed substantially in said plane and having a diameter substantially larger than said bearing, and a weight of a radius substantially equal to said enclosure fixed to said shaft immediately below said eccentric so as to rotate within the enclosure with its center of gravity disposed substantially in said plane but on the opposite'side of the shaft axis from the center of mass of said shoes.
2. A rubbing machine having, in combination, a rigid generally flat plate, a hollow flange rigid with and upstanding from the plate and defining a recess extending downwardly into the plate substantially to the bottom thereof, a pad of yieldable material secured to the bottom of said plate and forming a backing for an abrasive sheet, a bearing mounted in said flange closely adjacent said plate, a shaft projecting through said bearing into said recess, an eccentric on said shaft within said bearing, said sheet, said pad, said plate and the parts' gyrating therewith constituting a rubbing shoe having its center of gravity located within said recess close to said pad, a counter-weight fast on the lower end of said shaft below said eccentric and rotatable within said recess in a plane closely adjacent said center of gravity, the moment of inertia of said weight substantially balancing that of said shoe, a frame disposed above said shoe and rotatably supporting said shaft, and means mounted on said frame and acting to hold the shoe against turning while permitting free gyration thereof.
3. A rubbing machine having, in combination, a rigid frame, a rotary drive shaft journaled in said frame with one end projecting from the bottom of said frame, a rubbing shoe including a rigid top plate, and a pad of yieldable material secured to the bottom of said plate and forming a backing for an abrasive sheet, said shoe and the parts rigid therewith having a center of mass disposed closely adjacent the plane of said plate, means joining said frame and plate and acting to hold said shoe against rotation but permitting bodily gyration thereof aroundthe shaft axis, said plate having formed therein an upwardly opening generally flat recess receiving the lower end of said shaft and disposed substantially in .said plane, a bearing supported by said plate in the upper part of said recess, an eccentric on said shaft disposed immediately. below said frame bottom and journaled in said bearing whereby to gyrate said shoe and its center of mass in said plane, and a counterweight fixed to said lower shaft end immediately below said eccentric so as to rotate Within said recess with its center of gravity disposed in said plane 5 6 substantially coincident with the center of mass of said 2,367,668 Champayne Jan. 23, 1945 rubbing shoe but on the opposite side of the shaft axis. 2,418,246 Burleigh Apr. 1, 1947 2,441,506 Osman May 11, 1948 References Cited in the file of this patent 2,614,369 Robins Oct. 21, 1952 UNITED STATES PATENTS 5 2,639,564 Atkin May 26, 1953 2,248,182 Mateer July 8, 1941