US2485137A

US2485137A - Connection means for phonograph pickups

Info

Publication number: US2485137A
Application number: US561137A
Authority: US
Inventors: Walter J Brown; Alfred L W Williams
Original assignee: Brush Development Co
Current assignee: Brush Development Co
Priority date: 1944-10-30
Filing date: 1944-10-30
Publication date: 1949-10-18
Anticipated expiration: 1966-10-18

Description

Oct. 18, 1949. w. J. BROWN ET AL CONNECTION MEANS FOR PHCNOGRAPH PICKUPS Filed Oct. 30, 1944 4 v INVENTORS. WALTER J; BRowu Ammo LM VILunns Z2 9 Patented Oct. 18,1949

UNITED STATES PATENT OFFICEt- CONNECTION MEANS FOR PHONOGRAPH PICKUPS Walter J. Brown and Alfred L. W. Williams, Cleveland Heights, Ohio, assignors to The Brush Development Company, Cleveland, Ohio, a corporation of Ohio Application October 30, 1944, Serial No. 561,137 7 Claims. (Cl. 179100.41)

Our invention relates to the art of translating the electro-mechanical transducer through the mechanical vibrations into electrical impulses. pickup arm. More particularly our invention relates to means In this invention we hingedly mount a phonofor supporting a pickup cartridge for an elecgraph pickup cartridge from a pivotably mounted trical phonograph, and is a continuation-in-part 5 pickup or tone arm in a manner to achieve all of application Serial Number 378,463, now U. S. of the mentioned benefits and to reduce the un- Patent No. 2,368,198 dated May 4, 1944. balanced weight of the pickup arm which is sup- Pickup arms for electrical phonographs are deported on the phonograph record by means of signed with two pivots or bearings to allow for the phonograph stylus. movement in two directions. The first or vertical 10 It is an object of our invention to provide a pivot or bearing allows the pickuparm to move mounting between a pickup arm and an electrohorizontally with respect to the record being mechanical transducer which reduces the amount played and, as the pickup arm stylus follows the of vibration transmitted from the arm to the grooves of a 'disk record in toward the center of transducer and which resists torsional vibration the record, it allows the entire pickup arm to of the arm. move about the first pivot. The second or hori- Another object is to provide a resilient conneczontal pivot or bearing is one on which the pickup tion between an electro-mechanical transducer arm turns or moves in an up and down direction and an arm. such as when the stylus is taken ofi of the record A further object of our invention is to provide or when irregularities in the record or turntable a co nection between an electro-mechanical cause the pickup arm to move up and down with transducer and a Supporting arm which resists respect to the phonograph. 1n t design and torsional vibration of the transducer with respect manufacture of these pivotg or bearings constid; 2 2 gi l fi gl-er object of on mv nt n is t able care must be exercised o kee he amoun o B 0 0 bearing play at a minimum is particularly provide a resilient connection between an e1ectrotrue for arms designed for use with laterally cut mechanical transducer and a Supporting arm records which depend f iiheir operation on base which provides a damping action to prevent parting a torsional vibration to a needle which in ggg g figg gg transfer of extraneous Vlbr 34910115 turn imparts a vibration to an electro-mechanical 1 Another object of our invention is to resilient! hairsaiss sss.ss zstatistic: mm mm needle vibration to be absorbed by the pickup ig g gz fii zifie forces due to warped arm in the form of a torsional vibration about p othgr sweets aim f u d t dm f a longitudinal axis parallel to the length of the J a er un am an g o our invention may be had by referring to the g zpg x g ggfifig z gg g 2: following detailed description and claims, taken reduce the amount of stylus vibration which is conjunction with the following drawings in which transmitted from the undulations in the record Figure 1 1s a sectional view of a portion of a the electro-mechamcal transducer and may phonograph pickup arm and showing a pickup introduce serious distortion in the wave form at 40 cartridge mounted on the arm. low frequencies As the frequency of h Wbra" Figure 2 is a cross-sectional view taken along tion in the stylus becomes higher and higher the line of Figure 1 and distortion in the wave form introduced by the.

Figure 3 is'a side elevation of a honogra h torsional vibration of the pickup arm becomes less pickup arm partly in section to g z and less due to the inertia of the pickup arm remethod of mounting the pickup cartridge.

.sisting the torsional vibration. The resistance to Figure 4 is a View, partly in Section, of a t the torsional vibration in the pickup arm causes f m of our invention a higher percentage of the stylus vibration to pass Figure 5 is a Sectional View of a modified form to the electro-mechanical transducer and results of our invention in more eilicient conversion of mechanical movew t reference t9 Figures 1 and 2 th r i ment to electrical impulse. It is also desirable h n a form of our i ti i hi h a t ha the P p arm be cushioned to Prevent ducer unit is suspended from a pickup arm l0 vibration produced by either the record, turnby means of a resilient hinge 56 placed between table motor, or any other source external of the the transducer 55 and the pickup arm l0. As the stylus on the record from being transmitted to 55 stylus 6| follows vertical movements of an uneven turntable or warped record the transducer unit 55 pivots about the hinge 56 and very little if any acceleration in a vertical direction is imparted to the pickup arm II). By thus reducing inertia forces the stylus pressure on the record may be reduced and maintained more evenly thereby increasing the life of the records and of the stylus. As in the embodiments illustrated in the parent application, Serial Number 378,463, now U. S Patent No. 2,368,198 dated May 4,v 1.94:4 the resilient hinge 56 may be a metal spring, but we prefer a block of rubber such as sponge rubber or the like as, in addition to the resilient property, it also has the property of effecting a dam-p ing action for reducing the transmission of vibration between the pickup arm l and the transducer unit 55. Fairly stiff sponge rubber blocks may be used to achieve these damping and flexing actions.

The transducer unit 55 is connected to the resilient hinge 56 by means of rivets or screws 51 and the resilient hinge 56 is connected by means of the rivets or screws 58 to a web 59 depending from the head 60 of the pickup arm I 6, thereby suspending the transducer unit 55 from the pickup arm head The resilient hinge '55 may have a relatively high section modulus oriented in a direction to prevent torsional vibration of the transducer with respect to'the pickup arm lo and the pickup arm head 50;and may have a relatively low section modulus in'a direction to permit the transducer unit 55 to move vertically with respect to the pickup arm head to accommodate yertical irregularities in the turntable or record. The point of connection between the transducer unit 55 and the pickup arm head 30 is substantially at the midpoint of the transducer unit 55, but is sufficiently off-center that when the head is lifted from a record the stylus 6i drops slightly with respect to the head 60. The stiffness and location of the hinge 56 may be varied to obtain the least pressure on the point of the stylus 6| which is commensurate with good reproduction. The stylus 6| is connected to a piezoelectric crystal unit 62 bymeans of a drive Wire 63, and the crystal unit 52 includes leads which are connected to the shielded wire 31. The transducerunit 55 and its connection to the amplifiers (not shown) are more fully described in Patent Number 2,081,862,

to A. L. W. Williams. It is to be understood, however, that any other kind of transducer mechanism such as a magnetic transducer may be used with our invention.

Figure 3 illustrates another embodiment of our invention in which the transducer unit 55 (crystal, magnetic, or the like) is connected to the pickup arm head 60 by means of a resilient hinge $4. One end oithe hinge 64 is connected to the transducer unit by means of rivets or screws 51, and the other end of the hinge is connected to the pickup arm ID by means of rivets or screws 5, thus supporting the cartridge 55 from the pickup arm "I. The hinge is positioned at the end of the transducer unit away from the stylus Shand it may be found convenient to use a finger 65 connected to the end or the pickup arm head 50 to engage the stylus end of the transducer unit 55 to prevent the hinge 64 from bending too far when the pickup arm is lifted from the record which is being played.

.Figure 3 also illustrates a hinge and stop construction adapted for use with either of the embodiments of our invention shown in Figures 1 and 3. weprovidc a vertical stop 88 to limit the amount of downward arm motion, in addition to the horizontal stop 4| to limit the amount of lateral arm motion. The vertical stop 56 is connected to the bearing shaft 22 by means of a screw or rivet til and is rotatable in a horizontal plan-e as the pickup arm rotates. The. vertical amp to is not iptatable'in a vertical plane and is adapted to limit the downward distance to which the pickup arm head 60 will move by engaging the underneath side of the pickup arm H). The downward limit of the movement of the pickup arm head 60 is such that the head 60 is held by the stop 55 slightly above the record being played and to cause the stylus SI of the transducer unit '55 to ride in the record groove with suilicient pressure for good reproduction. This manure is represented by the force resulting from the effective weight of the transducer unit 55 and the elastic force exerted by the resilient hinge 64.

Figure 4 illustrates a further modification of our invention which is particularly useful if the pickup is to be used in an upside-down position, such, for example, as a pickup used to reproduce from the underneath side or a record. It is also useful 11" the record is to rotate about a horizontal axis and be reproduced by a pickup which is mounted sideways.

The cartridge 55 maybe connected to the head 60 of the ickup arm to at a point which is substantially the balance point, and the spring III is positioned between the inside surface of the head portion 60 and the top-surface of the pickup cartridge. A molded ring TI is provided on the head portion 66 and a similar ring T2 on the pickup cartridge to prevent sli'p'page'of the spring id. The spring 10 exerts a biasing force which tends to push the stylus end of the cartridge 55 away from the head 60 to cause the stylus SE to extend below the lower surface of the head 60. Thus, whether the pickup is in the position illustrated by Figure 1 or in the position shown by Figure 4, or in any intermediate position it will be operable.

It may be desirable to adjust the bias exerted by the spring 15. An example of where adjustment may be of value is when the cartridge 55 is connected to the head so at a location on the cartridge away from the balance point to cause the stylus end thereof to be slightly heavier than the other end. With this condition it would make a difi'erence in the force exerted by the stylus against the record whether the pickup was operated in a normal orin an upside-down position. By utilizing a spring whose biasing force is adjustable the stylus force can be made uniform for normal or upside-down operation.

The biasing force of spring 15 is adjusted in the following manner. A pressure plate M is positioned between the spring 15 and the underneath side of the head so, and a screw I5 extends through the top wall of the head 50. Turning the screw 15 in one direction causes the pressure plate to move toward thecartridge 55, thereby compressing the s ring 10 and increasing the bias; and turning the screw 15 in the opposite direction relieves the bias.

This bias adjusting screw may extend through the top wall of the head 50 as shown, or it may extend through the cartridge 55. 'An advantage of having it extend through the cartridge 551s that the bias of the spring 16 may be set when the pickup is put on the phonograph and the screw would then be out of sight and less apt to be tampered with.

By utilizing an adjustable bias device such as the illustrated spring and pressure plate arrangement it permits manufacturing one pickup for operation in normal, upside-down, or angular operation.

With the pickup constructions shown the stylus 6| will be biased into engagement with the phonograph record by the unbalanced weight of the transducer, or, in the device of Figure 4, by the unbalanced weight (if any) plus the spring bias.

When playing a record the unbalanced weight of the pickup arm is substantially entirely supported by the vertical stop 68 which permits the pickup arm 50 to be lowered until the stylus 6| engages the'record and until the transducer unit pivots slightly about the hinge by which it is connected to the pickup arm. The hinge, being resilient, exerts a force through the transducer cartridge to couple the stylus to the phonograph record, and this force reacts on to a small extent there is a slight amount of the weight of the pickup arm supported on the stylus. However, if the phonograph record is warped the vertical movement of the transducer cartridge caused by the unevenness results in a hinge action between the transducer and the pickup arm. The arm, therefore, is not moved to any great extent by the warped record and acceleration forces on the stylus are kept to a low amount.

Although we have described our invention with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

We claim as our invention:

1. A pickup device comprising a supporting arm, a complete transducer unit, and a single supporting means joining said transducer unit to the arm, said supporting means comprised of flexible rubber or the like and having a relatively high section modulus in a first direction and a relatively low section modulus in a second direction, means connecting one end of the flexible supporting means to said support, means connecting the other end of the flexible supporting means to said transducer unit in such a manner that the direction of said high section modulus is substantially perpendicular to and the direction of said low section modulus is substantially parallel to the longitudinal axis of said transducer unit whereby said supporting means resists torsional vibrations applied to the transducer unit and permits rotation of one end of the transducer unit with respect to said supporting arm.

2. A pickup device as set forth in claim 1, further characterized by said supporting means being substantially a solid block of flexible rubber or the like.

3. A pickup device as set forth in claim 1, further characterized by said supporting means the pickup arm. Thus being connected to said transducer unit substantially at the center of longitudinal balance of said transducer unit.

4. A pickup device as set forth in claim 1 wherein said transducer unit has a stylus at one end thereof, further characterized by said supporting means being connected to the end of said transducer unit opposite said stylus end.

5. A pickup device comprising a supporting arm including at one end thereof an inverted hollow elongated cup-shaped head, a complete transducer unit, and supporting means joining said transducer unit to said head, said supporting means comprising a plate-like body of flexible rubber or the like, means connecting one end of the flexible supporting means to an inside wall portion of said head with the smallest dimension of said plate-like body in a direction substantially parallel to the longtiudinal axis of said transducer unit, means connecting the other end of said flexible supporting means to said transducer unit whereby said supporting means resists torsional vibrations applied to said transducer unit and permits rotation of one end of the transducer unit with respect to said supporting arm.

6. A pickup device as set forth in claim 5, further characterized by said plate-like body being connected to a side Wall portion of said inverted cup-shaped head and depending downwardly therefrom.

7. A pickup device as set forth in claim 5, further characterized by said plate-like body being connected to the bottom wall portion of said in- :verted cup-shaped head and depending downwardly therefrom free from engagement with the side walls of said head.

WALTER J. BROWN ALFRED L. W. WILLIAMS.

' REFERENCES CITED UNITED STATES I PATENTS Number Name Date 1,792,554 Thomas Feb. 17, 1931 1,905,669 Yenzer Apr. 25, 1933 2,174,692 Dunning Oct. 3, 1939 2,177,692 DiToro Oct. 31, 1939 2,181,437 Norton Nov. 28, 1939 2,257,804 Lord Oct. 7, 1941 2,269,403 Williams Jan. 6, 1942 2,294,674 Lord sept. 1, 1942' 2,368,198 Jones May 4, 1944 2,379,282 Dally et a1 June 26, 1945 2,379,782 Bobb July 3, 1945 2,386,089 Bobb Oct. 2, 1945 2,444,218 Carnahan June 29, 1948 FOREIGN PATENTS Number Country Date 849,531 France Nov. 25, 1939 f