US2669812A - Rubbing machine - Google Patents

Description

Feb. 23, 1954 R. J. CHAMPAYNE RUBBING MACHINE Filed April 20, 1949 2 Sheets-Sheet 1 Feb. 23, 1954 R J, CHAMPAYNE 2,669,812

RUBBING MACHINE Filed April 20, 1949 2 Sheets-Sheet 2 og CLS- CVLQLm-cubrxe Patented Feb. Z3, 1954 UNITED STATES? PATENT OFFICE RUBBING MACHINEv Roy .l`.` Champayne, Rockford, Ill.

Application `April 20, 1949, Serial 1N o. 88,511l

1 claim; l

This'. invention relates to arubbing. machine driven `by arotary motor and has more particular.

reference to machines of the typ-e employing a pluralityA of cranks for converting the rotary motion of the actuator into bodily gyration of a rubbing shoe while at the same time holding theshoeagainst turning.

To counterbalance the eccentric weight of the. rubbing sh-oe in machines of the above character, it hasbeen the practice heretofore to provide a vsingle auxiliary Weight ofthe same mass as the rubbing shoe and employ an additional pair of power` driven cranks to gyrate the weight in out of phase synchronism with the rubbing shoe and in an orbit of similar size as to that of the gyrating shoe. As shown by Fisker Patent No. 2,247,993, the auxiliary counterbalancing Weight may be a second rubbing shoe disposed alongside the first shoe. By locating the counterpoise` between the rubbing shoe and its support as shown by Crosby Patent No. 2,395,537, lateral compactness may be acheved but at the sacrilice` of over-all weight and increased complexity' ofthe actuating and supporting parts.

I have discovered that in order to counterbalance a rubbing shoe which is gyrated by two cranks as described above, it is not necessary to. employ a gyrating weight or a weight having the same mass as the rubbing shoe proper; Based on thisdiscovery, the present invention is to substantially eliminate vibration of therubbing machine by dividingr the counterbalancingmass into a plurality of parts each having a simple" rotary motion and disposed at a substantially larger radius than the radius of. gyration of'lthe rubbing shoe.

Another object is to locate the'counterbalancingmasses in a novel manner which materially reduces the over-al1 dimensions of the rubbing machine as compared to prior constructions.

A more detailed object is to divide the counterbalancing mass into av plurality of parts which revolve with the respective crank shafts and.

Figure 1 is a side elevational View of a rubbing` machine embodying the novel features of` the present invention.

Fig. 2 is a longitudinal central sectional view'.

Figs, 3 and 4 are fragmentary sectional viewsl taken respectively along the lines 3--3 and` 4-4 of Fig. 2.

Fig. 5 is an exploded perspective view of one of the drive shafts and the counterweights thereon.

Fig. 6 is a detail sectional View.

For purposes of illustration, the inventionis" shown in the drawings incorporated in a port-r4 able self-contained rubbing machine driven by a rotary motor IIJ housed within a casing II which supports a rubbing shoe I2 for bodily gy-l ration. The shape of the casing is determined by Whether the shaft I3 of the motor is to bei disposed parallel to the rubbing shoe or per-- pendicular to the latter as in the present in-V stance. Herein, the casing is generally domeshaped and formed on opposite sides with a han dle I4 and a knob I5 either or both of which may be gripped bythe operator to carry the tool, guide it along a Work surface to be sanded, or' press the shoe downwardly against the work.-

In the present instance, the stator I6 of the motor, which may be of the electric type, is secured in the casing by screws I'I and the shaft I3 of the rotor I3 is journaled to its upper end in a bearing I9 in the top of the casing. The

shaft is centered relative to the shoe I2 and near its lower end is journaled in a bearing 20 mounted in a plate 2| which forms the bottom of thef casing II and is detachably secured to the latter by a plurality of screws 22 (Fig. 6). Within the casing, the shaft I3 carries fan blades 23 fordrawing cooling air through the motor and discharging the same outwardly through ports 24 (Fig. 1).

The rubbing shoe comprises a generally rectangular rigid backing plate 24 of light weight metal such as magnesium carrying a pad 25 of yieldable` material. An` abrasive sheet or other" rubbingor brushing element maybe attached to# In the case of an abrasive sheet,- the ends are` bent upwardlfy andf around the shoe ends and secured in clamps?? the bottom. of the latter shoe.

The shoe and the mechanism for converting` the rotary motion of the motor into gyratory motion of the shoe is supported as aself-contain'ed` unit on the plate 2I and they gyrating mechanism'` isdisposedbetween the shoe and thefplatef. This'V mechanism includesftwo parallel shaftsfZ-l spaced-i..

equidistantly from opposite sides of the motor shaft I3 and pressed through the inner race rings of ball thrust bearings 28 whose outer rings are pressed into holes 29 in the plate 2| and seated against inturned flanges 30.

Cranks 3| formed on the lower ends of the shafts 21 are journalled in ball thrust bearings 32 seated in annular flanges 33 upstanding from the top of the shoe plate 2i! and disposed equidistantly from opposite ends of the shoe |2 along the longitudinal center line thereof. rlhe shoe is thusI disposed symmetrically with respect to the motor shaft. The outer race rings of the bearings 32 are heldin the seats by screws 34 and the inner races bear against shoulders 35 on the shafts 21. The cranks are offset in corresponding directions so that the shoe is gyrated bodily in a circular orbit which, in this instance, is il@ of an inch in diameter.

The shafts 2'! are driven in unison and at a speed reduced from the motor shaft |3. Vnile this may be accomplished in Various ways, it is preferred to employ gears 35 fast on the shafts 21 meshing with teeth on the motor shaft. If the motor shaft were disposed horizontally or parallel to the shoe i2, the gears would be of the bevel type, but with the shaft disposed vertically, as shown, spur gears are employed and disposed immediately below bearings 28 so as t0 mesh on adjacent sides with opposite sides of a pinion 31 fast on the lower end of the motor shaft. To reduce noise, the gears :it are preferably composed of non-metallic material such as fiber. A 3 to l speed reduction is employed in the present instance. The operating mechanism is enclosed by a removable skirt 38 preferably composed of exible material such as rubber and clamped by bands 39 around the periphery of the support 2| and an upstanding iiange 40 on the shoe plate 2d.

With the parts arranged as above described, rotation of the motor shaft i3 will result in turning both of the cranks 3| in the same direction and in phase with each other. Power is thus applied to both end portions of the shoe I2 which is gyrated bodily in a inch orbit. Pressure applied to the casing i i to hold the rubbing sheet against the work is transmitted to the casing through the shafts 2l and the four thrust bearings 28 and 32 between which the total thrust is divided.

'To insure gyration of the shoe in a truly circular orbit and to prevent any substantial vibration of the handle ill and other parts of the cas-'- ing, the invention contemplates counterbalancing the unbalanced weight of the shoe |2 and the cranks 3| in a novel manner which minimizes the total weight or the tool, which provides optimum compactness, and which requires no changes or rearrange-ment of the simple power operator described above. In achieving these ends, I have found that it is unnecessary to form the counterweight in a single mass or to center the weight with respect to the shoe |2, or to gyrate the weight as has been the practice heretofore. Instead, I divide the counterweighting mass into a plurality of parts 4| of equal Weight respectively carried by the two shafts 21 with the centers of gravity of the two masses disposed close to the plane of gyration of the center of gravity of the shoe i2 and spaced from the shaft axes distances which are several times the radius ofgyration of the shoe.

In the present instance, the counterweights 4| are xed to the shafts 21 immediately below 4 the gears 36 but the main mass of the weight is centered outwardly beyond the bearing flanges 33 and below the upper ends thereof so that the weights rotate in the annular space surrounding these flanges and Within the shoe ilange 40.

Preferably, each weight comprises a curved or arcuate flange depending from a flat arm or sector 42 secured as by a screw 43 against the underside of the gear and itself forming part of the effective mass of the counterweight. Herein, the inner end of the arm is forked and straddles a squared portion M formed on the shaft between the gear and the crank 3|, the weight being thereby accurately positioned angularly directly opposite from the crank. The two parts of the counterweighting mass thus mounted occupy space already available within the operator, and the size of the individual weights is reduced because of the location at a relatively large radius which may, as shown, be even greater than that of the gears by locating the pinion 31 with its lower end ush with or above the bottoms of the gears.

With the weights arranged as described above, the centers of their masses rotate in a plane which is oiTset only slightly above the plane of gyration of the center or" gravity of the shoe |2 and therefore the eccentric weight of the shoe and the cranks may be substantially balanced by properly correlating the sizes and positions of the two weights 4| in relation to the unbalanced weight of the shoe I2 and the over-all weight of the tool. More accurate balancing and substantial elimination of vibration of the casing may be achieved through the use of an additional counterweight rotatable in unison with the gyration of the shoe and acting in opposition to and balancing the force couple resulting from the inability to locate the weights 4| in the plane of the center of gravity of the shoe |2. Herein, two additional weights 43 are employed and spaced as far as possible above the weightsl 4| without interference with the rotating parts. To this end, the weights 46 are made in the form of relatively flat arms pressed onto the flattened upper ends d5 of the shafts 21 just above the supporting plate 2| and below the fan blades 23. Each arm projects from its shaft on the side thereof directly opposite the center of the lower weights 4| and thus during its rotation derives a centrifugal force which eiectually overcomes the bending moment exerted on the shaft due to the axial oisetting of the mass centers of the weights 4| and the shoe l2.

It has been found in practice that the tool above described may be counterbalanced effectually by sizing the parts as shown in Fig. 2 and by employing main counterweights (parts 4| and 42) of only 2 ounces each, and secondary counterweights do each weighing only 1/2 of an ounce. The use of such small weights is made possible by virtue of the location of their effective masses at substantial distances from the axes of rotation. The total weight of the tool is 'l1/2 pounds, and the gyrating shoe assembly Weighs 11/ pounds.

I claim as my invention:

A. rubbing machine having, in combination, a 3' support, thrust bearings mounted in said support and having laterally spaced parallel axes, two parallel shafts journaled at one of their ends in said bearings with the other end portion of the shafts projecting from one side thereof, a

rubbing shoe disposed beyond the outer ends of said shafts, cranks on the outer ends of said F5 first shafts journaled in said rubbing shoe near opposite ends thereof and operable to gyrate the shoe in orbits of equal diameters, a rotary motor mounted on said support between said shafts and havinga drive shaft, means disposed between said bearings and said shoe and providing speed reduction drive connections between said motor shaft and each of said first shafts to turn the latter in the same direction, and two counter- Weights each fixed to one of said rst shafts between the drive connection thereof and said shoe and eccentrically disposed on the sides of the shafts opposite said cranks, the masses of said weights and their effective radii being correlated 'with the eccentric Weight of said shoe and cranks to counterbalance such Weight eiectually during operation of said motor.

ROY J. CHAMPA'YNE,

References Cited in the le of this patent UNITED STATES PATENTS 10 Number Name Date 2,247,993 Fisker July 1, 1941 2,367,668 Champayne Jan. 23, 1945 2,395,537 Crosby Feb. 26, 1946 2,437,152 Burleigh Mar. 2, 1948

Images