US3548119A - Microphone and magnetic switch assembly - Google Patents

Description

United States Patent Inventors Robert C. Ramsey Niles; Gerrald K. Farrington, St. Joseph, Mich. Appl. No. 655,538 Filed July 24, 1967 Patented Dec. 15, 1970 Assignee Electro-Voice, Incorporated Buchanan, Mich. a corporation of Indiana MICROPHONE AND MAGNETIC SWITCH ASSEMBLY 8 Claims, 1 Drawing Fig.

Int. Cl. H04r l/00 Field of Search 179/167,

158,159,1SW,163,165,114R,l15R;240/10.63, 10.66, 10.6, 25

[56] References Cited UNITED STATES PATENTS 3,162,376 12/1964 Syiochi Furuya 240/1066 3,283,274 11/1966 A. De Falco 335/206 Primary Examinerl(athleen H. Claffy Assistant Examiner-Randall P. Myers Attorney-Burmeister and Kulie ABSTRACT: A magnetic switch assembly for a microphone having a magnetic actuator slidable on a continuous wall of the microphone casing; said actuator being directly removable; and said casing being substantially unmodified while the actuator is still releasable and retainable with respect to the casing; and said magnetic actuator cooperating with a reed switch positioned within the casing on a support provided on a foldable frame member adapted to hold other microphone circuit components.

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PATENTED am 51970 SHEET 3 OF 3 MICROPHONE AND MAGNETIC SWITCH ASSEMBLY This invention relates to a microphone and magnetic switch assembly; and the invention makes particular reference to an assembly in which an exterior actuator element may be simply removed, the microphone then being actuated. The present invention also relates tomagnetically actuated switches.

Microphones generally include a casing or housing with a microphone transducer disposed within the, casing and exposed to the surrounding sound field and a connector accessi- I ble from the exterior of the casing. Theconnector is adapted to be engaged to either a male or femaleplug to provide electrical connections to the transducer. Various switch units and assemblies have been provided at some location on the casing of conventional microphones to actuate and deactuate the microphone. Such switches are generally permanently mounted and fixed in position on the microphone casing. It is evident that such permanentlymounted switches require interlinking structures between the switch actuation member and the circuit breaking elements of the switch. It is an object of the present invention to provide a switch which utilizes a movable magnetic field between the switch actuation member and the switch circuit breaking elements, and thus eliminates the mechanical linkage of conventional switches.

Further, present switch assemblies are often objectionable insome applications such as microphones because the actuation member is visible and exposed; It is an object of the present invention to provide a switch assembly and a microphone utilizing such'a switch assembly, in which the ac tuating member may be removed.

A microphone constructed according to the present invention permits the use of a substantially unmodified microphone casing, thus providing the microphone with an attractive appearance and advantages in handling. A performer handles a microphone in various ways during a performance, and it is an advantage to the performer to eliminate a large switch structure on the microphone casing. In addition to the advantageous handling qualities, a microphone without a switch actuating member on the exterior thereof has a pleasing appearance in that thecasing presents a clean, substantially unmodified line.

Another object of the invention is to provide a switch assembly for a microphone in which an exterior magnetic actuator element may be removed from the casing and mounted on the casing without the use of auxiliary fasteners, such as screws, clips or the like. This object is served by providing a magnetic actuator which may be essentially snapfitted onto the casing and released from the casing by moving apart resilient members of the actuator element.v

Still another object of the invention is to provide a microphone and magnetic switch assembly in which the microphone has a casing in which one part of the switch assembly is displaced. and the switch circuit breaking elements and other microphone circuit components are conveniently and compactly mounted on a frame disposed within the easing; and in which a magnetic actuator is disposed exterior of the casing for actuating and deactuating the microphone circuit without requiring any interlinking structures between the actuating member and circuit breaking elements of the magnetic switch.

Objects such as the foregoing are attained together with still other objects which will become apparent from considering the ensuring specification, including drawings'wherein:

FIG. I is an exploded side view partly in section and with portions separated;

FIG. 2 is a longitudinal sectional view of the microphone of FIG. I;

FIG. 3A is an enlarged top plan view of a reed switch unit, which is a cooperative part of the switch assembly of the microphone of FIGS. 1 and 2;

FIG. 3B is an enlarged side elevational view of the reed switch insert of FIG. 3A; 1

FIG. 4 is a sectional view of the actuator member taken along line 4-4 of FIG. I;

FIG. 5 is a bottom plan view of the actuator member of FIG.

FIG. 6 is a sectional view of the actuator member taken along line 6-6 of FIG. 4;

FIG. 7 is a top plan view of a frame insert in unfolded condition before insertion into the casing of the microphone;

FIG. 8 is a side elevational view of the frame insert of FIG.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8; FIG. 10 is a sectional view taken along section 10-10 of FIG. 3;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 8;

and

FIG. 12 is a sectional view taken along line 12-12 of FIG. 8. FIG. 1 shows an exploded view of the microphone and magnetic switch assembly constructed according to the present invention, and it includes an elongated casing 14 having a continuous cylindrical wall 15. As will be apparent hereinafter, the casing must be constructed of magnetic. flux permeable material, i.e. not a ferromagnetic material. The microphone is shown with an enlarged or hell portion 16 at-one end to hold the electroacoustical transducer in the form of a dynamic microphone head 17. The enlarged end.l6 of the casing 14 receives the microphone head 17 and is threaded at l8'as will be described hereinafter. The opposite-end of the casing 14 is shown as open with a continuous groove 20 in the continuous wall 15 of the elongated casing. The open end of the casing is also threaded, as indicated at 22, so that the threads 22 and groove 20 may receive a threaded cord plug (not shown) which can engage the threads and be seated in the continuous groove. An aperture 23 is disposed adjacent to the open end of the casing 14 to receive a set screw 23a to secure a connector insert within the casing 14.

The exterior surface of wall 15 of the casing 14 is provided with a pair of opposed narrow grooves or troughs 24 on opposite sides thereof. The grooves 24 are parallel to the axis of the wall 15 and are of relatively short length, and are adapted to releasably engage a magnetic actuator shown generally as 26, which will be described in greater detail.

The microphone includes a protective screen 28 which is disposed in the opening of the bell shaped end of the casing to expose the transducer 17 to the surrounding sound field. The screen 28 encompasses wind screen 30 of open cellular foam plastic or the like. The microphone alsohas a grill 32 and a magnetic shield 34 which are mounted on a retainer head 36 by a screw 39. The retainer head 36 is disposed within the bell end 16 of the casing and engages the threads 18. The retainer head 36 also secures the dynamic microphone-head 17 within the casing 14. The microphone head or transducer 17 may be a dynamic type with a diaphragm movable within a permanent magnetic field or another type of transducer such as a balanced armature magnetic transducer or a piezoelectric transducer or the like.

The microphone circuit components are shown to include conductors 40, 42 connected to terminals 44, 46 of the head 17 and to a reed switch shown generally at 48. Leads 50 and 52 extend from the reed switch to a terminal board 54, and leads 56 and 58 extend from the terminal board to the primary winding of a transformer 60. Lead 62 is connected between the transformer 60 and one terminal of the connector insert 64 for connection to an appropriate plug cord. The magnetic reed switch 48 in shown in FIGS. 3A and 3B as including an envelope 66 which is evacuated and encloses reeds 68 and 70 which are normally mechanically biased apart. The envelope 66 is substantially rigid and may be a plastic, glass or an equivalent material readily penetratable by a magnetic flux. The reed 70 is substantially shorter than the reed 68, and the reed 68 is constructed of resilient ferromagnetic material. The reed 68 may thus be attracted by a magnetic force toward the reed 70, thus causing the confronting ends of the reeds 68 and 70 to abut each other and form electrical contact. Electrical contact between the reeds 68 and 70 effectively shorts the primary winding of the transformer 60, and thus deactuates the microphone. The reed switch 48 is thus one cooperative component of the inagnetic switch assembly, and the normally spaced apart reeds are brought into contact under responsive influence of a magnetic flux.

The reed switch 48, transformer 60 and insert 64 are of electrically insulating material disposed within a foldable frame 71 having one part 72 folded on another part 74. The frame 71 also carries a grounding strap 75 which abuts the inside of the casing and is electrically connected to one end of the secondary winding of the transformer 60 by a lead 57; a screw 77 securing the strap 75 to part 72 of the frame 71 and thereby holding the strap 75 in grounding engagement with the casing 14, as illustrated in FIG. 2. It is to'be noted that the casing 14 forms one of the output terminals, and the shield of the connector cable should thus be connected to a female connector which threadedly engages the threads 22 on the end of the casing 14, as is conventional.

The foldable frame 71 is best illustrated in the FIGS. 7, 8, 9, 11 and 12 before folding or assembly andin FIGS. 2 and when folded and holding the various microphone circuit components. Part 72 is formed by a relatively thin part cylindrical throughout its entire length with a radius of curvature slightly less than the radius of curvature of the inner surface of the cylindrical wall of the casing 14. One end 76 of part 72 is open and the other end is closed by an end wall 78. The end wall 78 is a flat part circular disc and extends across the entire end of the part 72 and is integral therewith. Part 72 has a plurality of cutouts 79a, 79b and 790 forming a relatively flat floor portion 80. The floor portion 80 terminates a short distance from the open end 76 to form a generally semicylindrical inner surface 84. The confronting end of the floor por 'tion 80 forms a flat shoulder disposed normal to the axis of the part 72 and adjacent to the part cylindrical surface 84. Projecting portions 90 and 90a extend from opposite sides of the part 72 in the region of the surface 88 and terminate at a distance from the open end 76 of the part' 72, thus forming spaced right angle cutouts 92 and 92a at the open end 76 of the part 72.

A counter-sunk aperture 96 is disposed centrally of the semicylindrical surface 84 for accommodating a set screw 97, as is shown in FIG. 2.

The floor portion 80 in the illustrated embodiment is shown with an area 98 adjacent to the cutout 79a which has no part cylindrical sidewalls. An elongated rectangular opening 100 in this area accommodates one the rectangular sides of the trans formers 60, the protruding windings of the transformer abutting the surface of the floor portion. The semicylindrical surface 84 at the open end 76 of the part 72, of the frame 71 forms a socket which accommodates the connector insert 64 between the shoulder 88 and the open end 76,

A portion 102 of the surface of the floor portion 80 on the side of the transformer 60 opposite the open end 76 accommodates the terminal board 54. This region has an aperture 104 extending through the floor portion 80 through which lead 57 from the transformer 60 extends to make a connection with the grounding strap 57, which is in contact with the casing 14. Sockets or blind bores 106, 108 extend into the surface of the floor portion 80 flanking aperture 104 along the axial length of the floor portion 80, and button projections 110 and 1100 protrude from the floor portion 80 and flank blind bore 106 transversely of the elongation axis of the floor portion 80. The terminal board 54 has protruding buttons 111 disposed within the blind bores 106 and 108 and recesses receiving button projections 110 and 110a to retain the terminal board in position. Similar blind bores 112, 114, button projections 116, 116a, and aperture 118 may be seen on the opposite side of the transformer for engaging a second terminal board when required.

Formed integrally with floor portion 80 is'a raised support 120, and this support secures reed switch 48 on part 72. The support 120 is a resilient body having a leg 122 with a transverse axis parallel to the longitudinal axis of the part and of substantially greater length than the thickness of the leg 122.

The support also has a pair of generally spaced legs 124 and 126 having transverse axes disposed on a common axis parallel to the transverse axis of the leg 122. Leg 122 has a continuous ledge 128, as best illustrated in FIG. 7 and 9, with a curved upper surface 129 contoured to the exterior surface of the reed switch 48. Also legs 124 and 126 are provided with ends protruding toward the leg l22 and the ends have an undercut 130 formed thereon to conform to the contour of the reed switch 48. The cylindrical envelope 66 of the reed switch 48 is wedged between the legs 124 and 126 and the leg 122 securely held on the frame 71 in this manner.

The cutouts 79a, 79b and 79c form a plurality of ribs, such as rib 132 which extends below the floor portion 80 of the first part 72. The legs 132 are continuations of the part cylindrical external surface of the frame 71 and contact the interior wall of the microphone casing 14, as illustrated in FIG. 2.

Frame member part 74 is integral with part 72 has a planar portion 134 which is connected mechanically to end wall 78 of part 72 through a hinge 135. The hinge 135 is formed by a flat strip 135a which extends between parts 72 and 74, and is provided with a transverse groove so that 74 may be foldable on top of part 72, as shown in FIG. 2. Since the hinge 135 must be of resilient material, the frame 71 is preferably of plastic material, such as polyproplene, which also satisfies the requirement of low electrical conductivity.

Planar portion 134 has a cutout 136 which is adapted to allow the spaced resilient legs 122, .124 and 126 to pass therethrough when the part 74 is folded down on part 72. The cutout 136 has edges 136a and 13612 disposed parallel to the longitudinal axis of the part 74 which engagethe outer surfaces of the legs 122, 124 and 126. As best shown in FIGS. 7 and 9, the legs 122, 124 and 126 present outer surfaces which taper outwardly from the ends of the legs to the floor portion 70, so that the edges 136a and l36b wedge against the outwardly facing surfaces of the legs 124, 126 and 122, respec-.

tively, thereby assuring a secure mounting for the reed switch 48 Adjoining the planar portion 134 of part 74 is a part cylindrical portion 138 with the same radius of curvature as that of part 72. The part cylindrical portion 138 also has a part cylindrical inner surface 139 which extends between two end walls 140 and 142 disposed normal to the longitudinal axis of part 74 and extending thereacross. The planar portion 134 of part 74 is disposed in the plane of part- 74 nearest the axis of revolution of the surface 138, so that when part 74 is folded on top of part 72 as indicated in FIG. 2, a maximum volume is disposed between the surface 139 and part 72. The contour of the frame 71 formed by part 72 and 74 conforms to the cylindrical inner surface of the casing 14 of the microphone when the frame member is folded, thus permitting the folded frame to be inserted within the casing 14.

Part 74 has an open end 144 defined by a part cylindrical surface 146. curved protruding stubs 148, 148a extend from the open end of part 72 and mate with cutouts 92 and 92a of part 72 when the parts are folded together. A semicircular groove 150 in the exterior surface 138 in a plane normal to the longitudinal axis of part 74 is aligned with a groove 139 in part 72 to form a seat for circular spring 152 (FIG. 1) to hold the folded parts 72 and 74 together prior to insertion into the casing 14, thereby facilitating this operation.

The actuator element 26 is releasably mounted on the cylindrical wall 15.of the microphone casing 14. As shown in FIGS. 4, 5 and 6, actuator element 26 is in the form of a yoke and includes a body 154 with a pair of spaced legs 156 and 158 extending therefrom and integral therewith. The inside surface of the legs 156 and 158 and the body 154 is a continuous generally semicylindrical surface 160 with a diameter approximately that of the cylindrical wall 15 of the casing 14, so that the inner surface 160 of the actuator element conforms to the exterior surface of the cylindrical wall 15 of the microphone casing 14. The legs156 and 158 have lugs 162 and 164, respectively, which protrude toward one another from the surface 160 to slidably engage the grooves or channels on opposite sides of the microphone casing, one of which is shown at 24 in FIG. 1. These lugs serve to slidably mount the actuator element 26 on the casing 14 and to limit the travel of the actuator element between the actuate and deactuate positions, as will be more fully described hereinafter.

The top of the actuating element 26 has a flat, roughened surface 166 to provide traction for the finger or thumb of the operator which will slide the actuator element along the microphone casing 14. The roughened surface is shown as comprising a plurality of alternating ridges and valleys. The sidewalls 168 and 170 of the actuator are tapered from top to bottom to provide thicker regions adjacent to the surface 166 and thus limit bending of the legs 156 and 158 in the region adjacent to the surface 166. Hence, the body 154 and legs 156 and 158 of the actuating element 26 may be constructed of resilient plastic, such as polysulfane and the outward bending of the legs 156 and 158 will be sufficiently restricted that the actuator element 26 will form a good snap fit on the casing 14. The front and back sides of the resilient body have surfaces 172 and 174 which taper outwardly from the top roughened surface 166 to provide a longer surface for engagement by the operator. Approximately at the junction of the body 154 and the legs 156, 158, the front and back sides of the actuating element 26 are undercut as at 176 and 178; and the front and back sides then continue as straight edge surfaces as shown at 180 and 182.

The surface of the body 154 confronting the wall of the casing 14 is provided with a generally cruciform socket 183 which has tapered sides 184, 186, a tapered end wall 188, and a straight end wall 190 so that a permanent magnet 192 of matching configuration is securely wedged into the socket 183 and secured therein as by cement.

The socket has extensions 196, 196a, 1961; and 1960 which impart a cruciform configuration to the socket. This permits a tool to be used for seating the permanent magnet 192 in the socket or for removing the permanent magnet therefrom. The magnet 192 is magnetically polarized along an axis parallel to the longitudinal axis of the casing 14 in order impress a maximum of flux on the reed 68 of the reed switch 48.

in use, the resilient legs 156, 158 of the yokelike actuator element 26 are urged apart so the actuator element may be mounted on the microphone casing 14 in such a way that interlocking lugs or guides 1.62, 164 are seated in the grooves 24, one in the casing 14. When the actuator element 26 is translated towards the connector end of the casing 14 the magnetic flux from the magnet 192 is aligned with the reed 68 of the reed switch 48 thus increasing the magnetic attraction between the magnet 192 and the reed 68, and causing the reed 68 to abut the reed 70 to deactuate the microphone. The reeds 68 and 70 will remain in abutment and the microphone deactuated as long as the magnet remains in this position. This position of the actuator element 26 is determined by sliding the actuator element backwardly until the lugs 162 and 164 are stopped against the ends of the grooves 24. The microphone may be actuated in either of two ways. First, the resilient legs 156. 158 can be urged apart and the actuator element 26 removed from the casing 14, whereupon the microphone may be operated without the actuator element. Second, the actuator element 26 may be translated toward the bell 16 of the casing 14. Either of these ways displaces the magnet from the reed 68 and permits the resiliency of the reed 68 to pivot the reed 68 from the reed 70 and open the reed switch 48. The microphone is rendered operative by sliding the actuator element 26 forwardly until the lugs 162 and 164 abut the ends of the grooves 24 towards the enlarged portion 14 of the casing.

The use of the frame insert member 71 to hold the reed switch 48 of the transfonner 60, terminal board 54 and connector insert 64 permits these elements to be assembled and electrically interconnected exterior of the microphone casing 14, and inserted into the casing 14 as a unit.

When the frame member 71 is folded upon itself, these components are securely held in position without requiring each element to be separately mounted. The folded frame member 71 with the assembled components is secured within the casing of the microphone by a single screw 198 extending through an aperture 200 in the casing 14 adjacent to the insert 64, as illustrated in FIG. 2.

Such a frame 71 is preferably integrally molded from a slightly resilient plastic. A suitable plastic for the frame 71 is polypropylene. The same or equivalent plastic material may also be used to mold the actuator element 26.

The foregoing specification describes a microphone switch of the shorting or normally open type, i.e., a switch which is open during normal operation. Those skilled in the art will also recognize that the invention may be practiced with a series connected switch which is closed during normal operation.

The invention may now be practiced in the various ways which will occur to practitioners, and all such practice is intended to be a part of the present invention provided it comes within the terms of the following claims as given further meaning by the language of the preceding specification We claim:

1. A microphone comprising, in combination: a casing constructed of nonmagnetic material having an opening to the surrounding sound field, an acoustoelectrical transducer mounted within the casing in communication with the sound field for generating electrical signals responsive to said sound field, and an electrical switch electrically connected to the electroacoustical transducer for actuating and deactuating the microphone, wherein the switch comprises a magnetic reed switch having a first and a second operable condition mounted in a fixed position within the casing, said switch having one reed pivotally mounted with respect to the other reed and being in one of said operable conditions when said reeds are in abutment and the other of said operable conditions when the reeds are spaced, said pivotally mounted reed being constructed of ferromagnetic material and having a permanent set relative to the other reed to establish one of said first and second operable conditions as a normal condition, an actuator mounted on the outside of the casing, said actuator being movable on said casing and having a permanent magnet therein adjacent to the casing, and a foldable frame member within the casing, said frame member having a first part, a second part, and hinge means connecting said parts, said parts being foldable from a linear extension to a matching position of said parts, and said parts in the folded position adapted to receive and hold various elements of the microphone circuit, including means to hold the reed switch in a fixed position within the casing, magnetic flux from said permanent magnet penetrating the pivotal reed when said actuator is disposed adjacent to said reed switch to induce said reed to move from its permanent set to establish the other operable condition of the switch, and the magnetic flux not affecting the pivotal reed when said actuator is remote from the switch.

2. A microphone comprising the combination of claim 1 wherein the reed switch includes a pair of reeds biased out of contact and disposed within a substantially rigid, elongated envelope, and wherein said first part includes a support member for said envelope, said support member including spaced resilient members to receive and release the envelope by a snap fit.

3. A microphone comprising the combination of claim 2 wherein the second part of the foldable frame member has a cutout adapted to be positioned above the support member when the frame member is folded, said cutout permitting the spaced resilient legs of the support member, and the envelope positioned therebetween, to pass through the cutout in said second part.

4. A microphone comprising the combination of claim 3 wherein the first and second parts have curved sidewalls when in the unfolded linear extension, a planar end wall radially in tersects the curved walls at adjoining ends of said parts, and hinge means joining said second part to the said first part at the top of an end wall, said second. art having a substantially .1 V planar portion connected to said hinge means, said cutout being disposed in said second part planar portion.

5. A microphone comprising the combination of claim 3 wherein:

said first part has an open end with a part cylindrical contour, a connector insert disposed in said open end;

a planar area on said first part adapted to receive a transformer; I

a curved wall area in said first part having a floor portion and spaced curved walls, said support member rising from said floor portion above said curved wall area;

a verticalend wall intersecting an end of said curved wall area, said hinge means joining said second part to said first part at a junction at the top of said end wall;

a planar area in said second part connected to said hinge means, a-cutout in said second part planar area through which the resilient legs of the support member may pass when the second part is folded onto first part;

an open end of said second part, region having a part cylindrical configuration at said second part open end, said part cylindrical region at said open ends of said first and second parts forming a cylindrical region of said connector insert when the parts are folded; and

a curved wall area on said second part which cooperates with said first part curved wall area to form substantially circular portions when said parts are folded together.

6. A microphone comprising the combination of claim 5 wherein a substantial portion of the axial length of said first part is spaced from the wall of the casing when positioned within said casing, and said first part further including a plurality of legs spaced along the axial length to support the folded frame insert within said casing.

7. A microphone comprising the combination of claim 5 wherein which further includes means to fasten the part cylindrically adjoining folded ends of said first and second parts.

8. A microphone comprising, in combination, an elongated casing constructed of nonmagnetic material having an opening to the surrounding sound field, an acoustoelectrical transducer mounted within the casing in communication with the sound field for generating electrical signals responsive to said sound field, and an electrical switch electrically connected to the electroacoustical transducer for actuating and deactuating the microphone, wherein the switch comprises a magnetic reed switch having a first and a second operable condition mounted in a fixed position within the casing, said switch having one reed pivotally mounted with respect to the other reed and being in one of said operable conditions when said reeds are in abutment and the other of said operable conditions when the reeds are spaced, said pivotally mounted reed being constructed of ferromagnetic material "and having a permanent set relative to the other reed to establish one of said first and second operable conditions as a normal condition, an actuator mounted on the outside of the casing, said actuator being movable on said casing and having a permanent magnet therein adjacent to the casing, and a pair of spaced resilient legs which ride against the exterior surface of the casing, the actuator being removable from the outside of the casing by pulling the legs of the actuator element away from the outside of the casing, the actuator further including interlocking guide projections on the inside surfaces of the spaced resilient legs, said guide projections being opposed to one another, opposite sides of the casing wall having elongated slide grooves, said projections being adapted to ride the slide grooves when the actuator is mounted on the casing, whereby. the opposed terminating portions of the slide grooves define the extent of the movement of the actuator to its respective positions for moving the reeds in and out of contact with each other, magnetic flux from said permanent magnet penetrating the pivotal reed when said actuator is disposed adjacent to said reed switch to induce said reed to move from its permanent set to establish the other operable condition of the switch, and the magnetic flux not affecting the pivotal reed when said actuator is remote from the switch.

zygg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,548,119 Dated December 15, 1970 I mmfl Robert C. Ramsey & Gerrald K. Farrington It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 54 after "is", change "disp1aced" to --di'sposed.

Column 1, line 64 after "the", change "ensuring" to -ensuing-.

Column 3, line 74 after "part", insert -72--.

Column 6, line "75 after"second", change "art" to -part--.

Column 7, line 21 after "ends", change "of" to --for--.

Signed and sealed this 8th day of June 1971.

(SEAL) Attest:

EDWARD M.FIETCHER, JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents

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