US2852636A - Air jet commutator - Google Patents

Description

Sept 16, 1958 A. v. BLOCK ErAL AIR JET coMMUTAToR Filed Aug. 12, 1955 INVENTOR. @ZW M56/ 7' 4,4/ W

llii.

United.

AIR JET COMMUTATOR Application August 12, 1955, Serial No. 528,139

Claims. (Cl. 20G-81.9)

This invention relates to mechanical commutation devices and the like.

In the ield of mechanical commutation, the desirable characteristics of an ideal commutator are long life, reliability of operation, high scan speeds with direct current operation, and large segment selection. No commutator exists, however, which is ideal with respect to each of these features. For example, if the speed of commutation is high, the life of the equipment is correspondingly low. Ordinarily the life of a commutator has been limited by contact and rotor wear to only a few million operations.

The subject of this invention provides a lluid jet cornmutator which solves the above problems by having no rubbing contact between the rotor and contact arm and by having only impact contact between the contact arms.

The object of this invention, therefore, is to provide a commutator of a simple design but which will give long life, reliability of operation, and can be used at high scan speeds.

A further object of this invention is the elimination of rubbing contact in commutator devices and substituting therefor only impact contact.

The accompanying drawings disclose illustratory concrete embodiments capable of carrying out the underlying principles of my invention.

Figure 1 shows the uid jet commutator in its application environment;

Figure 2 shows the fluid jet and ribbon type commutator in a blown-up view;

Figure 3 shows a detail view similar to Figure 2 but depicting a cantilever type commutator.

Figure 4 is a view along section lines 2-2 in Figure l.

In prior art devices of commutators, the maximum scan rate was approximately 30 c. p. s. These commutators are rotating wafer switches, motor type commutators with either rotating brushes or rotating segments, or distributor type commutators operating on the cam principle. The above commutators are limited by a short life at high speeds due to excessive wear of either the rotor elements or the contact arms. Their designs also inherently introduce poor frequency response.

With the air jet commutator, it is expected that the life of such commutator should be in excess of 1,000 hours with scan rates of 200 c. p. s. and switching rates in excess of 50,000 operations/ second. In addition, the air jet commutator has a hat frequency spectrum from direct current into the megacycle/second region.

Referringto Figures 1 and 2, circular end plates 1 are mounted on each side of a tubular sleeve 2. Plates 1 are fixed or mounted to any convenient support. Mounted in tube 2 is a flywheel 3 which is secured to the central shaft 4. The shaft is rotatably supported in the end plates by means of ball bearings 5. Any convenient means may be used to drive shaft 4 at the desired rate of speed to obtain the proper scan speed of the air jet.

rates Patent l after closure.

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Bore 7 is drilled longitudinally of the shaft to slightly past its mid-point position. Bore 8 is drilled radially of the ywheel and central shaft to intersect the longitudinal bore 7. Screwed into flywheel 3 is the nipple 10 having a central bore 9 therethrough. The nipple is mounted within the ywheel 3 so that the two bores 8 and 9 are in alignment.

Ribbon 1S is mounted opposite the outlet 16 in nipple 10 between xed rings 11. The ring or posts 11 are secured to the tube 2 by means of fasteners 12.

While Figure 1 shows only several of the ribbon like elements for simplicitys sake, actually a plurality of such ribbon elements are arranged in an annular array as shown in Figure 4.

A dampening device 13 is placed adjacent the ribbon to prevent the ribbon from bouncing and giving false operation. The dampener 13 may take on several forms. For example, in Figure l, the dampener consists of curved heavy spring element with leather, felt or some other absorbent material adhered to the side facing the contact ribbon. The adjustment of the dampener may be made by screw means 14. In this type of dampener, the absorbent pad dampens the contact arm as it swings back The heavy Spring does not deflect appreciably but only serves to bear against the adjustment screw.

A second type of dampener which may be used is shown in Figures 2 and 3. The construction is similar to that of Figure l but the spring material and spacing of the absorbent material from the ribbon is such as to obtain an action wherein the fundamental oscillation of the contact ribbon is only broken and the ribbon is allowed to operate only at harmonics which are small and of such a nature as to prohibit contact recurrence.

Either type dampener, of course, may be used with either type of ribbon (Fig. 1 or Fig. 3).

Figure 3 shows a modification of the air jet commutator; instead of the ribbon type contact mechanism, a cantilever system is substituted therefor. Thus, a cantilever element 15 is mounted from a post 11 having contacts 17,- 18 at one end of the cantilever. The air jet nipple 10 is placed adjacent a portion of the cantilever as in the modication of Figures 1 and 2. Dampening mechanism 13 is also used as in the prior structure of Figures 1 and 2.

Obviously, each of the fixed contacts (17 and 17') has a means by which electrical contact may be made with it, such as separate lead 20 which may be separately brought through the tubular sleeve 2, as shown in Figure 4. The lead 20 is, of course, insulated from sleeve 2, as shown at 21, when necessary. Likewise, each of the movable contacts (18 and 18') are similarly accommodated, as with leads 22.

The operation of the two modifications is identical. Referring to Figures 1 and 2, compressed air is pumped through bore 7 from any convenient source. The air passes through bores 7, 8, 9, out exhaust jet 16 and impinges against the ribbon 15 or cantilever 15 (Figure 3). The force of impingement causes a momentary closure of contacts 17, 18 (or 17', 18 in Figure 3).

Shaft 4, meanwhile, is being rotated at the desired rate of speed. Nipple 10 is likewise rotated at the same rate of speed, causing successive impingement of the air jet on the successive ribbons or cantilevers mounted in tube 2. A port 6 is provided in one of the end plates 1 to prevent a build-up of air pressure within the enclosure.

Damping mechanism 13 is regulated to obtain optimum results with respect to bouncing of the cantilever or ribbon elements. This may have to be readjusted at different scan speeds.

.In `.the actual `construction of the unit, the end plates weremade of aluminum, theflywheel of brass, the damper of leather and the tube of phenolic. It is understood however that numerous substitutions of materials may be made without .dep'artingfrom the scope .of my invention.

Thelnipple,.inflturn,.had anoutletzport of 0:055 diam- -eter with the outlet spaced 0.008" :from fthe ribbon 'or Acantilever elements. .Numerous lother port sizes .and :spaced outlets may be used by a judicial selection `of combinations.

It is thus evident that only insignificant wear occurs `with Lmy improved commutation device, and such Awear Aoccurs only at .the Apoint of contact .since I the :air jet has a negligible :effect .on the .ribbon `or cantilever elements. Furthermore, :it .is relatively `simple to compensate ffor `any wear at .the .point of .contact with `the air I-jet commutation system. With a .conservative design .of .ribbon or cantilever elements, the stress inthe felement'sfmay `be :held .atsuch a low valuethat 4many 'hundredrmil-lions of operations .can be obtained.

Obviously many modifications and variations of the present invention lare possible in the light of the iab'ove teachings. It is therefore fto be understood that Within .the scope fof Athe appended claims .the vinvention :may 'be practiced otherwise ithan-as specically described.

What is claimedis:

1. In a commutation device, -astatio'na'ryhollow member having a Icylindrical .innerfsurface; .a plurality .of fixed, 'spaced electrical 'contacts mounted .annular'ly :on the fcylindrical surface of said member; a plurality of movable :annular-ly spaced, electrical .contacts .resilient-ly :mounted 'in vsaid xedmember and disposed .radially *inward and opposite said fixed contacts for yielding engagement therewith, .a fluid Apressure nozzle having its opening directed at said movable contact mounted in said fixed member for rotation in a peripheral plane that includes said contacts to sequentially close a movable contact on a fixed Contact under fluid pressure from said nozzle during rotation of said nozzle.

2. The device of claim 1 in which said iluid pressure is compressed air and said rhollow stationary member is .provided with an .aperture for exhausting the air Vfrom within it to prevent a pressure Abuild-up in the device.

3. The device of .claim 2 wherein each said movable contact includes a ribbon-like element mounted vbetween two ltXed supports, and the air pressure impinges against said ribbon-like elements.

4. The device ofclaim 2 Yin Whichsaid movable contacts include cantilever elements and the air impinges on the cantilever element to actuate the contacts.

.5. The Adevice of claim 2 .'furtherrincluding damping means mounted in said stationary member adjacent .the :movable contacts to prevent bouncing vof said contacts.

References Cited in `thefiile of this patent UNITED STATES PATENTS I1,322,506 Austin Nov. 25, `19'19 v2,290,725 Bartels et al. July 21, 1942 2,298,210 Gulliksen Oct. 6, 41942 2,455,494 Jaynes Dec. 7, -1'948 2,609,461 Holcomb et al Sept. 2, :19.52 2,773,665 Berger 'et al. Dec. 11, 1956

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