US2280446A - Vibrator sanding and polishing machine - Google Patents

Description

April 21, 1942.

A. NYMAN 2,280,446

VIBRATOR SANDING AND POLISHING MACHINE Filed July 16, 1937 2 Sheets-Sheet 1 l W 1 Q) 2411. 0 6 II 21 8;- l 24 l 3f 21w 4a 1 INVENTOR.

- ALEXANDER N YMAN BY I gh hofl ATTORNEY.

April 21, 1942. A. NYMAN VIBRATOR SANDING AND POLISHING MACHINE Filed July 16, 1937 2 Sheets-Sheet 2 o lob INVENTOR.

ALEXANDER N YMAN BY XM VQQ',

ATTORNEY.

Patented Apr. 21, 19 42 Alexander Nyman, Dayton, Ohio Application July 16, 1937, Serial N0. 153,930

\ 12 Claims.

This invention relates to vibratory devices for polishing, sanding and cleaning, and similar ap-' plications. A particular object of this invention is an efficient vibratory device which is simply and inexpensively constructed.

A further object of this invention is a device of this type which cannot damage the surface worked on.

A further object of this invention is to utilize the principle of mechanical resonance to produce the movement and force necessary for its operation.

An additional object is to provide a device quiet in operation.

A further object is to provide means for suitable adjustment of this device.

Further advantages and objects will appear in the following description referring to the attached drawings.

Fig. 1 is a diagrammatic representation of forces existing in the elements of a device forsilent operation;

Fig. 2 is an elementary view of a modification providing the forces represented in Fig. 1;

Fig. 3 is the external appearance of a preferred embodiment of the device in accordance with my invention;

Fig. 4 is a cross sectional view of the device of Fig. 3;

Fig.5 is a plan view of the device of Fig. 3;

Fig. 6 is another cross sectional view of the device of Fig. 3;

Figs. 7, 8 and 9 are views showing the detail of the operating pad.

The devices known at the present time for the purpose of cleaning, sanding or polishing surfaces have usually used a brush or pad operated by an electric or other type of rotary motor. The devices of this type besides requiring a relatively complicated construction and consequently high cost involve a large rotating inertia for the motor and the parts operated. Thus, if a device of this type is unintentionally pressed too firmly against the surface operated, the forces of inertia plus the active power supplied may be; sufficient to damage the surface. Thus, it is necessary to handle such devices with great care and, in practice, this togcther with the relatively substantial weight and ccst has been one of the great drawbacks and has limited their field of usefulness.

In my invention I have used one or more vibratory elements operated by alternating current magnet. In this case, the total inertia of the moving parts is only slightly in excess of the applied power. Therefore, a relatively slight pressure in excess of that required for normal operation will diminish and eventually stop the vibrations. thus avoidingentirely any injury to the surface. I have found that by bringing the mechanical system close to the resonance with the number of pulsations of alternating current, I can produce vibrations of amplitude and force sufficient to accomplish the work desired. I have found several alternate ways in which such tuning close to resonance can be achieved.

It is known that the number of vibrations of a mechanical system can be expressed by the formula in which N stands for the number of vibrations per second; F stands for the increment of the spring force per unit movement of the vibratory parts; and M is the mass of the vibrating part. Thus, the vibrating system must include in addi tion to the vibrating element a spring of such construction that the force per unit movement is sufficiently high to give the necessary number of vibrations per second. With the generally adopted current of 60 cycles per second, there are actually 120 impulses per second given to a magnet. Then when the magnet is used to activate the vibratory system, the latter should be adjusted to have its resonance frequency close to 120 vibrations per second. I have found by actual experiment that by varying the controlling factors as described below, the amplitude of the vibrator can be brought to a maximum and then reduced, thus showing the passing through the resonance point. I have found that for most cases the best operation is for resonance to be just below 120 vibrations per second, so that the additional resistance of the work accomplished by the vibrator will, if anything, bring it closer to the resonance condition.

I have found that if the spring is arranged in such a manner that its force is increased more rapidly, for instance, as the second and third power of the movement, then the tendency to strike the magnet is'reduced or eliminated. I have shown in Fig. 1 the diagram of such a spring as is illustrated in Fig. 2. Here the magnet I with the coil 2 cooperates with the yoke 8 which is held on a filament spring lb carried by the supports 38 and 39. Mathematicalanalysis of such a spring will show that its force can be represented by the curve such as S4 of Fig. 1. Moreover, by separating the supports 38 and 39, the tension on the filament 1b can be increased sulting in a tuning arrangement similar to the of the filament is increased to increase the number of pulsations per second, that is, the pitch of the tone. I have found this'arrangement particularly desirable.

Since at the point of intersection B and C with the magnetcurve M, the spring force becomes greater than the magnet force, the tendency to strike the magnet is thus eliminated.

I have developed a vibrator on this principle as illustrated in Figs. 3 to 9. Such a vibrator can be built with the exact and most desirable air gap, and the tuning accomplished by a suitable lever system described below. In practice, its operation is very eflicient, as the maximum of amplitude and force can be secured and at the same time there is no tendency to become noisy since the spring force increases enormously before the core can touch the magnet.

The pad itself for the purpose of rubbing or polishing should be as light as possible in order to permit the approach to the resonance condition without making the spring structure too stiff. I have found certain aluminum alloys, which are not as brittle as duralumin, can be used to make shallow pads'as illustrated in pad I which is held on pad support 9 by means of screws or rivets II. The outside surface of the pad 10 may be covered by some material, such as rubber or leather l2, which has high friction with the cloth or other material that may be used for actual polishing. I have found that coating the outside surface with a thin layer of rubber produces such a surface which has increover the advantage of not being able to absorb any of the liquids that may be used for polishing or rubbing as shown in Fig. 4. Element I2 may consist of a rubber tube slipped around the pad communicated as a reaction to the frame.

Therefore, the person operating the device feels only the minimum of vibration effect; in practice, it is quite negligible.

I have found that in order to reduce the noise during polishing, it is desirable to make the envelope of the movement of pad l0 continuous; i. e., at no point should any part of the pad project further down than any other part. This can be secured by making the pad cylindrical with the axis near the average bending point of the spring. The middle of the curved part of the spring (point D) is sufficiently close for practical purposes. The pad may be also made of a block of light wood, such as balsa,- shaped cylindrically on the outside and fastened to support 9 in anysuitable way, for example, by gluing. The covering of rubber or sand paper can be clamped on the block.

A flat handle I3 of wood or composition material gives a satisfactory supporting arrange- -ment. This handle is held in the projections 3b of the shell by means of two pins or screws tuning of a musical instrument where the tension "a. These projections are preferably s close '7 as possible to the mounting screws l8 of the shell and are provided with ribs 9d'to give greater rigidity. I

In order to avoid the unnecessary hitting of the yoke against the magnet, .I have covered the pole surface of the magnet with a thin fish paper strip 2a which is wedged inside the coil and as sists in assembling these coils-in the magnet.

I have further provided a switch I! which is mounted on the inside of the shell 3 and is held in position by two screws l5a which pass through suitable slots in shell 3. snugly into the plug receptacle 30 may be held in position by a metal ring 20a, the switch being suitably connected in the circuit with the coils to control the energization thereof.

Each pair of coils are connected in series by leads such as 28 and 29a, so that the current in the two coils of the same magnet is the same. The pairs of coils are connected in parallel. Thus, the current from the plug passes through lead 29 to the switch l5, hence entering lead 21 for one pair of coils comes out at 28 to the plug 20, and a parallel current from the switch passes through 21a to the second pair of coils and comes out through 29a to the plug 29. The direction of the windings is such that two opposite coils are magnetized in the same direction; therefore, the bridge of the H-magnet carries only the difference between the magnetic fields of the two magnets which is relatively small, and the cross section of this bridge can be made small without undue magnetic saturation.

I have found that for rubbing or polishing ordinary finished surfaces, such as polished wood, painted metal .or smooth metal, a cloth with an application of suitable rubbing material or polishing material of exactly the same nature as is used for hand rubbing or polishing gives excellent results. The apparatus may be placed directly on two or three layers of such cloth and will, then perform the rubbing or polishing work by merely sliding it over the surface to be treated. The moment the vibrator is in action, such sliding will require no physical effort at all by .the operator, as all the surface friction is taken up by the vibratory action of the pads. As the cloth is likely to slip off, I have devised an arrangement consisting of two helical springs 2|, each surrounding one end of shell 3 and supported by two clips 22, each fitting into the holes 22a of shell 3. Such a spring can be extended sufiiciently to hold the cloth between it and the shell permanently in position.

Fig. 6 shows clearly four spring filaments lb which I found could be preferably made of stranded silk cord, since the silk for the same cross section as steel has slightly more tensile strength and has considerably greater elongation, thus permitting a relatively large vibration without unduly high strain. These filaments are supported on two levers 38 and 39 which are pivoted on pivots 38a and 39a as is seen also in Fig. 4. The two levers are controlled by a common screw 40 which brings the upper points of these levers together, thus stretching the fila-.

ments. As seen in Fig. 5, the filaments are anchored to the levers by means, of small. pieces I! with rounded edges held by screws l9a to the levers 38 and 39. A protecting cover I9b of iibrous material, such as fullerboard underlaid by sheet aluminum, protects the silk cord from possible sharp edges of screws l9a. The filaments lb are moreover held on the rocker lever 9a by means of a small plate Ilia as seen in Figs. 4

The plug 20 which fits and 6 and two small screws lllb. A strip of fibrous material lllc protects the silk fibre from contact with metal. The rocker arm la as seen in Fig. 4 is pivoted on pin 9b and may have a bushing lc. The purpose of the bushing lies in the fact that the rocker arm a is preferably made of some aluminum alloy so as' to reduce its weight. A brass bushing gives better bearing surface on the pivot pin 91).

As seen in Fig. 6, the pivot pin 9b is held on a part of the casting I formed as a channel and constituting an integral part with the brackets 3c and I! (see Fig. 4) which support the lever. such as 38. The magnet core I and its coils 2 are mounted as above described, except that the screw it may bolt directly to projections 39 of the casting 3. The yokes Q are mounted on the rocker arm So by rivets 80 as seen in Fig. 4. The construction and electrical connections are in other respects as above described, and provision is made for continuous adjustment of screw 40 during operation of the device to adjust the tension in the filaments, the parts being held in rigid position in any predetermined setting or adjustment. As a result of such construction, and under the action of the electromagnet in effecting displacement of the armature from its neutral position, the tension in the filament is caused to increase more rapidly than in direct proportion to the displacing movements of the armature. This provides for effective and efficient vibrating action of the system with a substantial degree of movement and with proper assurance that the armature will not strike the pole pieces in normal operation. As above described a built-in plug may be used, or the leads may be brought out without a bullt-in-plug connection as is often usual in domestic appliances. I have arranged the casting to take a molded streamlined handle I 3 with possibly the strengthening rib II which is held by pins Ila on the casting 3. All of the parts are mounted on the casting I which is for the purpose left open at least in the central section as indicated by lines 45 and 46 of Fig. 3. This open section is later covered by a thin metal cover ll fastened by screws or rivets "a to the casting 3. An insulating sheet 48 covers the coils to protect them from injury or contact and is clamped between the frame 3 and the cover 41.

In Fig. 4 I have shown the operating pad I0 forming an integral part of the rocker arm 9a; e. g., as a die casting. It is provided with a padding cover 12.

Illustrated in Figs. 8 and 9 is an alternative preferred arrangement. The lever arm 9a with flanges 9d is attached by means .of rivets H to a pad plate III. This pad plate is provided with flanges like Illa which serve to clamp the pad proper. This pad consists of a block lib, preferably made of balsa wood, and is surrounded by a thin rubber sheath l2. In assembling this pad, the pad plate I0 is first riveted to aim 9a and the sheath l2 is slipped over the pad 10b. Next this pad with its sheath is inserted between the flanges of plate Ill and these flanges are then pressed and irnbedded into the relatively soft pad. I have found that this arrangement gives a light rigid pad of sufllciently soft surface to serve well both for sanding and cleaning. when used for sanding, a piece of sand paper is clamped over the surface of the pad by means of a wire loop 2!. Wire loop 23 is pivoted at 23a 'to the pad plate Ill and held in its closed position by the kink 23b engaging the same plate at the other end. The loop He serves to open this wire by finger pressure. The object of-this wire is to material isheld firmly in position and can be easily replaced'when worn out.

I have also illustrated in Figs. 3, 4 and 5 an alternative way of clamping the polishing cloth to the whole device. This consists of two small levers Ila and lib pivoted at 24 and 2!, respectively, and held in the closed position by small bent springs 2lc provided with caps 2ld. These springs are anchored to the casting 3 by rivet 24a and screw Zimrespectively. I have found that this arrangement holds the lever 2 la or 2Ib firmly against front and rear part of the device. By pressing the caps 2Id, the lever is released and can be opened up so that a suitable polishing cloth may be slipped under these levers. On pressing the levers at the depressions 2|] and 2|e, respectively, they are closed and hold the cloth firmly in position. A polishing device of this nature can be easily supported on a stick for polishing fioors or walls. Its weight being only a few pounds, it can be quite easily handled. This stick can be fastened in a number of different ways; for example, a stickprovided at its lower end with clamping jaws which are pivoted on a pivot rod 50 inserted in projections 49 of the casting I at about point E (Fig. 4) where the device balances.

I have found, in practice, advisable to provide holes 4| in the cover 41 opposite the adjusting screw All so that, if the weight of the operating pads is increased by putting relatively heavy abrasive cloth, or if the silk after usage loses some of its tension, then by turning the screw 40, the tension of the silk cords is increased and restored to a value giving satisfactory operation just below the resonance condition.

The principles of invention disclosed herein will suggest many modifications thereof to those skilled in the art, and it is accordingly desired that the appended claims be given a broad construction commensurate with the scope of the invention.

I claim:

1. A device of the character described comprising an electromagnet for producing periodic vibrating forces, an armature subject to the periodic vibrational forces of the electromagnet, a pivotaliy mounted arm for supporting said armature for vibrational movements from'a neutral position toward and away from said electromagnet in response to said periodic vibrational forces, resilient means fastened to said arm forming a vibrating system therewith, means for rigidly holding the ends of the resilient means to provide for development of a tensional force therein upon displacement of said armature from said neutral position under the action of said electromagnet which said tensional force increases more rapidly than the displacing movements of said armature, and a work-engaging member carried by said arm on the opposite sideof the armature from the pivot to provide for securing amplified movement of the work-engaging member.

2. A device of the character described comprising an electromagnet for producing periodic vibrating forces, an armature subject to the periodic vibrational forces of the electromagnet,

means for supporting said armature for vibrational movements from a neutral position toward and away from said electromagnet in response to said periodic vibrational forces, resilient means in which the force of the resilient means increases more rapidly than the displacing movements thereof .for opposing movement of said armatureawayfrom said neutral position and forming a vibrating system therewith, and means for adjusting the tension of said resilient means to tune the natural mechanical frequency of the vibrating system including said armature and said armature supporting means to a condition of substantial resonance with said periodic forces.

3. A device of the character described comprising means for producing periodic vibrating forces, an armature adapted to be acted upon by said periodic forces, means for supporting said armature for vibrating movement within the range of action of said periodic forces, a filament attached to said armature extending substantially transverse of the direction of movement of said armature and fixedly supported to maintain an initial predetermined longitudinal said arm intermediate its ends and adapted to be vibrated from a neutral position toward and away from said electromagnet in response to said periodic vibrating forces of the adjacent elec tromagnet, resilient means associated with each said arm in which the force of the resilient means increases more rapidly than the displacing movements thereof and forming vibrating systems therewith and a work engaging member carried by each of said arms having a curved work surface the center of curvature of which is substantially at the pivot axis of its arm, said arms being adapted to vibrate in unison and in opposite directions in response to said electromagnets to substantially neutralize inertia effects.

5. A device of the character described comprising electromagnetic means adapted to produce periodic vibrating forces, an arm supported adjacent said electromagnetic means, an armature carried by said arm adapted to be acted upon by said periodic vibrating forces, means for tensioning said arm to form a vibrating system, said tensioning means including resilient means fastened to said arm and extending at right angles to the direction of vibration of said arm and means for varying the longitudinal stress in said resilient means to tune said vibrating system to a condition of substantial mechanical resonance with said periodic vibrating forces.

6. A device of the character described comprising electromagnetic means for producing simultaneous periodic oppositely acting forces, a plurality of arms mounted adjacent said electromagnetic means, an armature carried by each said arm and adapted to be acted upon respectively by said periodic forces, means for tensioning said arms to form vibrating systems each including one of said arms, said tensioning means including resilient means fastened to said arms and extending at right angles to the direction of vibration thereof, and means for varying the longitudinal stress in said resilient means to tune said vibrating systems to a condition of substantial mechanical resonance with said vibrating forces, said systems vibrating in opposite directions to substantially balance inertia effects thereof.

'7. A device of the character described comprising electromagnetic means for producing simultaneous periodic oppositely acting forces, an arm mounted adjacent said electromagnetic means, an armature carried by said arm and adapted to be acted upon by said periodic forces, means for tensioning said arm to form a vibrating system, said tensioning means including resilient means having the characteristics of high tensile strength and low modulus of elasticity fastened to said arm and extending at right angles to the direction of vibration thereof, and means for varying the longitudinal stress in said resilient means to tune said vibrating system to a condition of substantial mechanical resonance with said vibrating forces.

8. A device of the character described comprising electromagnetic means for producing simultaneous periodic oppositely acting forces, an arm mounted adjacent said electromagnetic means, an armature carried by said arm and adapted to be acted upon by said periodic forces, means for tensioning said arm to form a vibrating system, said tensioning means including resilient means having the characteristics of high tensile strength and low modulus of elasticity fastened to said arm and extending at right angles to the direction of vibration thereof, means for varying the longitudinal stress in said resilient means to tune said vibrating system to a condition of substantial mechanical resonance with said vibrating forces, and means for protecting said resilient means from the destructive effects of vibratory movement.

9. A device of the character described comprising electromagnetic means for producing simultaneous periodic oppositely acting forces, an arm mounted adjacent said electromagnetic means, an armature carried by said arm and adapted to be acted upon by said periodic forces, means for tensioningsaid arm to form a vibrating system, said tensioning means comprising a silk filament fastened to said arm and extending at right angles to the direction of vibration thereof, and means for varying the longitudinal stress in said resilient means to tune said vibrating system to a condition of substantial mechanical resonance with said vibrating forces.

10. A device of the character described comprising a frame, an electromagnet mounted on said frame, an arm mounted on said frame for movement toward and away from said electromagnet, an armature carried by said arm for movement therewith under the action of said electromagnet, means on said arm for receiving a work device, a member rigidly supported on said frame and extending across said arm substantially at right angles thereto, means for fastening said member to said arm to form a vibrating system therewith, and means for predetermining the longitudinal stress in said member to tune the vibrating system to a predetermined mechanical frequency.

11. A device of the character described comprising a frame, a pair of electromagnets mounted adjacent each otherat one end of said frame,

a second pair of electromagnets mounted adjacent each other at the opposite end of said frame, each electromagnet of one pair being so wound as to effect magnetization in the same direction as one electromagnet of the other pair, arms, mounted outwardly of the ends of said electromagnets for movement toward and away therefrom, armatures carried by each of said arms and adapted to be attracted respectively by said electromagnets, a filament carried in nonyielding manner by said frame and extending transversely across said arms, and means for fastening each said arm to said filament to form therewith a plurality of vibrating systems.

12. A device of the character described comprising a frame, a pair of electromagnets mounted adjacent each other at one end of said frame, a second pair of electromagnets mounted adjacent each other at the opposite end of said frame,

each electromagnet of one pair being so wound as to effect magnetization in the same direction as one eleotromagnet of the other pair, arms mounted outwardly of the ends of said electromagnets for movement toward and away therefrom, armatures carried by each of said arms and adapted to be attracted respectively by said electromagnets, supporting members adjustably mounted on said frame, resilient means carried by said supporting members and extending transversely across said arms, means for fastening each said arm to said resilient means respectively to form a plurality of vibrating systems therewith, and means for adjustably positioning said supporting members to provide a predetermined longitudinal stress in said resilient means to tune said vibrating systems to a predetermined mechanical frequency.

ALEXANDER NYMAN.

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