US1950857A - Mechanical movement transmitting apparatus - Google Patents

Description

13, 1934. P. K. MCGALL 1,950,857

MECHANICAL MOVEMENT TRANSMITTING APPARATUS Filed March 23, 1931 2 Sheets-Sheet l ATTORNEY March 13, 1934. P. K. M GALL MECHANICAL MOVEMENT TRANSMITTING APPARATUS Filed March 23, 1931 2 Sheets-Sheet 2 INQENTOR ATTORN EY Patented Mar. 13, 1934 UNITED STATES PATENT orrice MECHANICAL MOVEMENT TRANSMITTING APPARATUS Philip K. McGall, Orange, N. J., assignor Best Manufacturing Company, Irvington, N. .L, a

copartnership The present invention relates to apparatus for the transmission of motion by mechanical means and particularly with the transmission of vibrational movement as, for instance, vibrational movement derived from the armature of a loud speaker motor, and has to do specifically with the transmission of such vibrational movement so that its angle or direction of application may be changed or redirected as desired, so

that its line of application may be translated or displaced bodily as desired, and so that the amplitude of the vibrations may be amplified or reduced.

The invention is particularly adaptable to it loud speaker construction, and it has as a broad object and advantage the possibility of mounting the sound radiating diaphragm and the loud speaker motor in such relative positions as desired, thus avoiding certain important structural limitations which are encountered in the usual loud speaker construction. As a specific illustration, the present invention makes it possible to design loud speakers of particularly compact assembly and of particularly small over-all dimensions without sacrifice of quality of sound reproduction.

In loud speaker operation, an armature or movable vibratory element is vibrated under the influence of the energizing electrical forces 80 which are applied to the loud speaker motor from a radio set, amplifier, or the like, and the resulting vibrational movement of the armature is transmitted to a sound radiating diaphragm through the medium of a driving rod or other appropriate mechanical connection to thereby vibrate the diaphragm and eflfect generation of sound in volume sufficient to be heard throughout a room. The modern tendency in loud speaker construction is toward a reduction in size of the loud speaker. This is particularly true with loud speakers designed for installation in small cabinets, automobiles, hotel rooms where the loud speaker is placed in the wall, and the like.

It is an object of this invention to provide mechanical movement transmitting apparatus, adapted particularly for loud speakers and similar uses, wherein the vibrational movement generated by the armature of the loud speaker motor is transmitted positively and without distortion to a driving element located entirely independently of the location or direction of movement of the vibrating element.

The construction and combination of parts by means of which the above stated and other objects and advantages are obtained are described below and are illustrated in the accompanying drawings wherein a preferred embodiment of the invention as applied to a loud speaker is shown. In the drawings, Figure 1 is a face view showing a cone type loud speaker which embodies the present invention; Figure 2 is a transverse sectional view taken on the plane indicated at 2-2 on Figure 1; Figure 3 is a partial sectional view taken as indicated at 88 3-3 on Figure 2; and Figure 4 is a perspective view illustrating certain details of the movement transmitting apparatus of the invention.

Referring to the drawings, 1 indicates the sound radiating diaphragm of the loud speaker, to here shown as a cone type diaphragm which may be made of paper, fabric, or other suitable material. The diaphragm l is supported at its periphery and is substantially enclosed by a housing 2, as shown. The loud speaker motor m for purposes of illustration, is shown as a socalled magnetic type of motor which comprises a permanent magnet 5 having pole pieces 6 between which an armature 7 operates, the

armature being in the field of the permanent magnet 5 and being also in the field produced by coil 8 which surrounds the armature '7, as shown, and which is supplied through its terminals 9 with energizing current from the radio set, amplifier, or the like. The loud speaker at motor is mounted on supporting bars 10 which extend across the open face of the cone as shown, the arrangement being such that the loud speaker motor lies entirely within the cone 1 so that the entire speaker occupies only as much as does 00 the diaphragm 1 alone. Armature 7 operates in the air gap between pole pieces 6 and, in regular operation of the apparatus, undergoes a vibrational movement about its longitudinal axis represented by armature mounting springs 11.

In the embodiment of the invention here shown, as illustrated particularly in Figure 4, a driving rod 12 is connected at one end to armature '7, as shown, so that vibration of the armature efiects longitudinal vibratory movement of the rod 12. At its other end driving rod 12 is connected to a crank arm 14 here shown as a die-stamped member of sheet metal soldered or otherwise suitably secured to a shaft 15, as indicated at 16, with its free end furnishing the connection with thelink 12, as shown.

Shaft 15 consists of a hollow light-walled metal tube. Shaft 15, being hollow, is possessed of maximum stifiness for a given weight, thus avoiding objectionable transverse vibration. Be-

ing of thin, light metal, shaft 15 is of low mass and thus avoids distortion of reproduced sound due to excessive inertia. A flat spring 17 is secured to one end of the hollow shaft 15, the spring 17 being set into the end of shaft 15 preferably across a diameter of the shaft as shown. The spring 17 is short and is secured to the supporting frame bars 10 by means of any appropriate connection such as the screw connection indicated at 18. At the other end of shaft 15 a. second flat spring 19 is secured, this spring also preferably being set into the end of shaft 15 across a diameter thereof, the spring 19 being preferably arranged, as shown, across a diameter of the shaft 15 which is at right angles to the other spring 17 thereby to aid in avoiding objectionable resonance points. The outer end of spring 19 is attached by a screw connection 20 to a cylindrical adjusting member 21. Adjusting member 21 lies in a bore provided in a block 22, the block 22 being split as indicated at'23 and provided with a tightening screw 24 by means of which block 23 may be clamped down upon adjusting member 21 to lock it in any desired position of adjustment, all of which will be evident from the drawings.

Adjusting member 21 is slotted at its outer end as indicated at 25 so that, by means of a screw driver or other adjusting tool, it can be turned within block 22 to place springs 17 and 19 under such tension as may be desired for proper operation of the apparatus. A particular advantage of adjusting block, 21 and its slot 25 which is accessible with an ordinary screw driver after the apparatus is completely assembled, is in the centering of armature 7. After assembly of the apparatus, armature 7 must be adjusted in the air gap between pole pieces 6 so that it lies centrally in the gap out of contact with each pole piece. The magnetic attraction of the pole pieces tends to pull the armature over against one or the other of the pole pieces, and.

hence springs 17 and 19 must be tensioned in order to hold the armature 7 in proper neutral position in the air gap. Proper tensioning of the, springs and proper centering of the armature is effected by means of adjusting block 21 after assembly of the apparatus is completed. Pads 17a and 19a of heavy rubber are preferably forced over springs 17 and 19, as shown, to aid in preventing excessive vibration.

Hollow shaft 15 is provided with a second crank arm 26 which, in the embodiment here shown, extends off the shaft 15 at right angles to crank arm 14. .Crank arm 26 is secured to a driving rod or link 27, as indicated at 28, and the opposite end of link 27 is secured to the sound radiating cone 21 as indicated at 29. It will be understood that the length of shaft 15 may be limited, if desired, to the desired distance between crank arms 14 and 26, to minimize the total mass of moving parts. This could be effected in the structure here shown by moving supporting bar 10 over adjacent crank arm 26 or by providing another supporting bar for the purpose.

The operation of the device is as follows: Armature 7 vibrates under the influence of the energizing electric current which is supplied to the loud speaker motor. The vibrations of the armature are transmitted through connecting link 12 to crank arm 14, with the result that the shaft 15 is given a vibrating movement about its longitudinal axis against-the action of springs 17 and 19. This rotational vibration movement of shaft 15 actuates crank arm 26 which in turn vibrates driving rod 27 and thereby actuates the sound radiating cone 1. In the particular embodiment here shown the direction of vibration of armature 7 has been turned through a right angle, has been translated into a new plane removed from the initial driving rod 12 a distance equal to the distance between crank arms 14 and 26, and has been increased in amplitude by an amount equal to the ratio of the effective moment arm of crank arm 26 to that of. crank arm 14. I

This arrangement shown and described herein permits the magnet 5 of the loud speaker motor to lie within the cone diaphragm, thus affording a particularly compact assembly and giving a complete speaker which is no larger than the diaphragm itself. If the driving rod 12, or a rod parallel to it, were secured directly to the cone 1, the loud speaker motor could not be contained within the confines of the cone diaphgram. Likewise, if the driving rod 27 were not displaced as shown from driving rod 12, the loud speaker motor would have to be shifted .relative to the axis of the cone so that armature 7 lay on the axis of the cone, in which case the motor could not be contained within the confines of the cone. The present invention is, therefore, important in the manufacture of small speakers of all kinds, such as wall type speakers, cabinet speakers, and the like.

It will be understood that crank arms 14 and 26 can be secured to shaft 15 at any desired relative angular relation, thereby effecting translation of the direction of application of the vibrational movement through any desired angle. It will also be. understood that the spacing of crank arms 16 and 26 along the length of the shaft may be regulated as desired depending on how far from the original plane of motion it is desired to translate the applied motion which is carried by driving rod 27. If only a short distance of translation along the length of the axis of the shaft is desired, the shaft may well be short and might even assume the form of a drum or disk or wheel as distinguished from an elongated shaft. It will be further noted that the relation between the moment arms represented by crank arm 14 and crank arm 26 may be varied as desired to determine the amplitude of the vibration applied to sound radiating cone '1 relative to the amplitude of vibration represented by the actual movement or" the armature 7. v

While the invention has been described herein as applied to a particular form of loud speaker it will be understood that it is applicable to other types of loud speakers, including the socalled dynamic type of loud speaker, and is also applicable to various other uses where a change in the direction of application, a shifting of the line of application, or a change in amplitude of a vibrational movement is desired.

The invention is defined in the appended claims largely in terms-of the features of structure, design, combination and arrangement which are responsible for the above described advantages, and variations from the specific disclosure of the specification and drawings may be made within the scope of the claims without departing from the invention.

I claim:

1. Motion transmitting apparatus of the class described which comprises a shaft, supports arranged adjacent the respective ends of said shaft, a spring interposed between each of said supports and the adjacent end of said shaft, whereby partial rotation of said shaft against the tension of said springs is permitted resilient members lying closely adjacent said respec-- tive springs for preventing objectionable vibration thereof, a vibrating actuating element, connections between said actuating element and said shaft for effecting vibrational rotative movement thereof against the tension of said springs, and connections between said rotative member and an actuated member for imparting vibrational movement thereto.

2. A loud speaker construction which comprises a cone type sound radiating diaphragm, a loud speaker motor mounted within the con- "fines'of said diaphragm, and means for translating vibratory motion from the armature of the loud speaker motor into a direction parallel with the axis of the cone and coincident therewith which comprises a connecting link secured to the motor armature, a rotatable shaft extending substantially at right angles to the axis of said cone, a crank arm provided on said shaft, connections between said driving link and said crank arm for imparting rotary vibrational movement to said shaft, a driving rod for said cone substantially coincident with the axis thereof, and a second crank arm connected to said shaft and to said driving rod, whereby a loud speaker motor of substantial size can be contained within the confines of the sound radiating cone.

' PHILIP K. McGALL.

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