US3327069A

US3327069A - Phonograph pickup cartridge

Info

Publication number: US3327069A
Application number: US390789A
Authority: US
Inventors: White Jack Mort
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1964-08-20
Filing date: 1964-08-20
Publication date: 1967-06-20
Anticipated expiration: 1984-06-20

Description

June 20, 1967 J. M. WHITE PHONOGRAPH PICKUP CARTRIDGE Filed Aug 20, 1964 I NV NTOR. JMK/K 1%,?

firm/wry United States Patent 3,327,069 PHONOGRAPH PICKUP CARTRIDGE Jack Mort White, Indianapolis, Ind, assignor to Radio Corporation of America, a corporation of Delaware Fired Aug. 20, 1964, Ser. No. 390,789 8 Claims. (Cl. 179100.41)

This invention relates to electromechanical transducers and more particularly to pickups for use with phonograph record players.

Electromechanical transducers and associated mechanical parts have inherent resonant characteristics that respond to a given frequency of vibration more intensely than other frequencies. For example, in photograph pickup cartridges these mechanical resonances produce undesired peaked outputs at certain frequencies. The effect of these resonant peaks, may be reduced by providing some sort of damping from the transducer structure.

A phonograph pickup cartridge embodying the invention includes an electromechanical transducing element which is coupled to a mechanical system for imparting mechanical vibrations to the transducing element. A damping member which engages the transducing element has a portion which extends into engagement with a portion of the mechanical system and thus not only serves to damp the resonances of the transducing element but also to damp the resonances of the mechanical system.

In accordance with a further embodiment of the invention, the damping member also serves to retain the transducing element and at least a portion of the mechanical system in predetermined desired positions.

FIGURE 1 is an enlarged perspective bottom View of the pickup cartridge assembly embodying the invention;

FIGURE 2 is a perspective top view of the pickup cartridge assembly of FIGURE 1;

FIGURE 3 is a sectional side View taken along the I longitudinal axis of the pickup cartridge assembly of FIGURE 1;

FIGURE 4 is a sectional front view of the pickup cartridge assembly taken along the section line 44 of FIGURE 3; and

FIGURE 5 is a sectional front View of the pickup cartridge assembly taken along the section lines 55 of FIGURE 3.

In referring to the drawings, like reference numerals designate the same components throughout the figures. The pickup cartridge (FIGURES 1 and 2) includes a substantially rectangularly shaped casing 12 of molded plastic with a rectangularly shaped exposed cavity 14 as viewed in FIGURE 2. Extending in opposite directions from the ends of the casing 12 are two mounting lips 16 and 18, each having a U-shaped slot 20 cut or molded therein. The pickup cartridge 1! is adapted to be fastened to the free end of a tone arm not shown, by a pair of mounting screws that extend through the slots 20 and firmly capture the lips 16 and 18.

In the present example, housed within the cavity 14 are a pair of elongated piezoelectric transducing elements 24 and 26 of rectangular cross-section. These transducing elements are supported by a pair of rectangularly'shaped spaced, rear and middle, rubber damping 'blocks 28 and 30 (FIGURES 2 to 5) which have openings 32 cut or molded therein for receiving and accurately positioning the transducing elements 24 and 26 with respect to each other. In order that the transducing elements 24 and 26 Y are accurataely positioned with respect to the cartridge casing, the damping blocks 28 and 30 are respectively received in two pairs of guideways or grooves 34 which are formed on opposite sides of the cavity 14 in planes perpendicular to the sides of the cavity (FIGURE 2).

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The dimensions of the damping blocks 28 and 30 are made slightly greater than the internal dimensions between the casing grooves 34 so that as these damping blocks are inserted between the grooves, sulficient pressure is provided to anchor the transducing elements securely in position. The transducer element mounting means as described is also adaptable in a similar fashion to a single transducer element monaural pickup assembly.

The rear damping block 28 is thicker than the middle damping block 30 so that the transducer elements are anchored more rigidly by the rear damping block 28 than by the middle damping block 30. The middle damping block 30 has a rectangularly shaped extended bottom portion 38 that fits through a rectangular slot 36 in the bottom of the casing 12 (FIGURES 1 and 5). The extended portion 38 is formed with a U-shaped groove or slot 40 to capture and resiliently grip a portion of a pickup cartridge stylus arm 42.

The openings in the damping blocks 28 and 30 are cut so that the major surfaces of the transducing elements 24 and 26 lie in perpendicular planes, with each plane disposed at an angle at 45 to a plane extending vertically through the longitudinal axis of the pickup casing. The free ends of the transducing elements 24 and 26, which are arranged and polarized to produce a voltage in response to a twisting stress, are driven by a yoke member 44 (FIGURES 2 and 4). Yoke member 44 is formed of an elastomer type material and has a pair of apertures 46 for receiving the transducing elements 24 and 26. The yoke member 44 has a pair of divergent legs 48 and 50 which are perpendicular to the plane of the transducing elements 24 and 26. The divergent legs 48 and 50 are stationary axially but flexible in directions normal to said axis. Any axial force or vibration on a yoke member divergent legs 48 or 50 is transmitted to a divergent edge 53 of the connected transducer element (FIGURE 4) causing a twisting torque on the transducer element. The bottom of the yoke member 44 in the present example includes a V-shaped resilient socket 52 with a pair of slots disposed at right angles and running parallel to the axes of the yoke legs 48 and 50 adapted to clamp around a similarly shaped portion of stylus arm.

The stylus arm 42 includes an elongated thin beam section 58 having a stylus mounted at one end and with a mounting hook or catch 62 formed at the other end. In the present example, the stylus 60 is mounted with its vertical axis (FIGURE 3) disposed generally perpendicular to the elongated axis of the beam section 58, although the disposition of the stylus axis may vary With the type of stylus and stylus mounting used. The mounting hook or catch 62 comprises two sections or surfaces disposed at approximate right angles connected by a curved portion. The upper surface of catch 62 (as viewed in FIGURE 3) lies displaced vertically from the elongated axis of beam section 58 in a plane and approximately parallel (at a slight tilt) to the elongated axis. The plane of the upper surface also lies generally normal to the vertical axis of the stylus 60. Depending upon the size of the yoke member 44 and its extension from the casing 12 and the type of stylus 60 and stylus mounting used, the angular relationship between the above-mentioned components can be modified to fit the particular situation.

The stylus arm 42 is pivotally mounted on the pickup cartridge by placing the upper surface of the catch 62 into a rectangularly shaped mounting hole 64 and then swinging the arm up towards the cartridge so that both surfaces of catch 62 swing into the mounting hole 64 and the lower side of the upper surface engages the cavity 14 interior wall while the V-shaped legs 56 snap into resilient socket 52 on the yoke member 44. In the process the extended damping block portion 38 of the middle damping block 30 resiliently grips and positions the stylus arm 42 at a point between the catch 62 and the V-shaped legs 56, thereby providing damping of the stylus arm as well as for the transducing elements 24 and 26. The above described stylus arm mounting assembly permits a limited freedom of movement in the vertical and lateral directions so that the stylus 60 can follow the recorded information in a record groove and also prevents the stylus arm 42 from rotating about its longitudinal axis. The stylus arm 42 is protected against excessive pressure or accidental dropping by the slotted V shaped extension 76. As pressure on the stylus 60 increases, the stylus arm 42. pivots upward (as viewed in FIGURES l and 3) until the stylus "60- swings into the slot 78 whereby the V shaped extension 76 bears any excessive pressure.

Electrical connections are provided for the transducer elements by flexible conductors 66 which are connected between the various electrodes of these elements and are laid in a rectangularly shaped cavity 68 in which are formed terminals 70', 72 and 74 and into which a plug can be inserted. One of these terminals, such as terminal 72, may serve as a common terminal for piezoelectric elements. If desired, four terminals may be provided, two for each transducing element. Connections from the terminals to the phonograph amplifier may be made in the usual manner. by conductors extending along the tone arm. Thus electrical signals corresponding to one of the separable recordings may be derived from one of the terminals and electrical signals corresponding to the other recording may be derived from the other terminal.

The above described damping blocks 28 and 30 provide damping of mechanical resonances thereby creating a relatively desirable smooth amplitude-vs-frequency response of a high quality phonograph pickup cartridge. In addition to damping the mechanical resonant peaks of the transducer elements 24 and 26, the block 30 provides a cantilever joint about which the transducer elements are twisted. The cantilever effect results in increased stress on the transducer element for a given amount of stylus movement thereby increasing the electrical output of the transducer element. Furthermore, the extended portion 38 resiliently grips the stylus arm 42 to dampen any natural resonant frequencies in the stylus arm and also any noise generated by a loose pivot mounting joint.

The above described phonograph pickup cartridge assembly can be modified to include a single transducer element where it is desired to produce a cheaper type pickup cartridge for presently existing single recording records. In such a case, the damping blocks 28 and 30 require only a single aperture and the yoke member 44 may be modified for single transducer element operation.

What is claimed is:

1. In combination with a phonograph pickup with at least one mechanical-to-electrical transducing element and a stylus arm with an attached stylus coupled to the transducing element by means of a yoke member:

a damping block of resilient material having openings therein receiving and positioning said transducer elements and receiving, supporting said stylus arm.

2. In a phonograph pickup with at least one mechanicalto-electrical transducing element and a stylus arm including a stylus, coupled to the transducing element by means of a yoke member:

a damping block of resilient material having openings therein receiving and positioning said transducer element and receiving said stylus arm;

a casing, and

- means for mounting said damping block in said casing to anchor said transducing element in a predetermined position in respect to said stylus arm.

3. In combination with a phonograph pickup with a pair of mechanical-to-electrical transducing elements and a stylus arm including a stylus, coupled to said transducing element by means of a yoke member:

a damping block of resilient material having a pair of openings therein receiving and positioning said transducing elements relative to each other and an opening therein receiving and resiliently gripping said stylus arm.

4. In a phonograph pickup assembly including at least one elongated end mounted mechanical-to-electrical transducer element, a stylus arm including a pickup stylus at the free end, a yoke member for transmission of vibrations from an intermediate point on the stylus arm to the free end of the transducer elements comprising:

a damping block of resilient material having openings therein receiving said transducer elements, said damping block resiliently anchoring said transducer element at an intermediate point between said transducer mounted end and said transducer free end, said damping block having an extended portion formed with an opening therein receiving and resiliently gripping said stylus arm.

5. A phonograph pickup assembly comprising:

a pair of mechanical-to-electrical transducing elements responsive to flexing of a major surface thereof to produce corresponding electrical signals;

a single piece yoke member having a pair of divergent legs and a slotted central portion, said legs each engaging a different one of said mechanical-to-electrical transducing elements;

a stylus arm pivotly mounted at one end thereof and having a record engaging stylus at the opposite end thereof, a portion of said stylus arm between the ends thereof adapted to ride in said slotted central portion of said yoke to transmit vibrations imparted to said record engaging stylus through said yoke member to said transducing elements, and V a damping block of resilient material formed with a pair of openings therein receiving and positioning said transducing elements relative to each other and formed with an opening therein receiving and resiliently gripping a portion of said stylus arm between said pivotly mounted end and the portion adapted to ride in said yoke central slotted portion.

6. A phonograph pickup assembly comprising:

a pair of mechanical-to-electrical transducing elements each having a rectangular cross-section;

a single piece yoke member having a pair of divergent legs and a reentrant central portion, said legs each engaging a different one of said mechanical-to-electrical transducing elements;

a stylus arm pivotly mounted at one end thereof and having a record engaging stylus at the opposite end thereof, a portion of said stylus arm between the ends thereof adapted to be captured in the reentrant central of said yoke to transmit vibrations imparted to said record engaging stylus through said yoke member to said transducing elements;

first and second resilient damping blocks, each having a pair of openings therein for receiving and positioning said transducer elements relative to each other, said first damping block resiliently gripping said pair of mechanical-to-electrical transducing elements at an intermediate point between the ends thereof, said first resilient damping block having an extended portion formed with a slot therein resiliently gripping a portion of said stylus arm between the pivotly mounted end and the yoke engaging portion, said second resilient block gripping said mechanicalto-electrical transducing elements at the end opposite the end engaging the yoke member, said second damping block having a thicker cross-section than said first damping block;

a casing, and

means for mounting said damping block in said casing to anchor said transducing elements in a predetermined position in respect to said stylus arm.

6 7. In a phonograph pickup of the type having a casing mechanical transducer and for receiving said stylus supporting an electromechanical transducer and having a arm, and coupling member extending from said transducer in the means for mounting said damping block in said casing direction of one side of said casing comprising: to anchor said electromechanical transducer in a prea stylus arm having an elongated beam supporting a 5 determined position in respect to said stylus arm.

record engaging stylus at one end thereof, said stylus 8. A phonograph pickup as defined in claim 7 wherein axis being disposed approximately normal to the axis said coupling member is formed with a reentrant portion of elongation of said beam, said stylus arm also prothat captures a portion of said stylus arm when said stylus viding a mounting portion at the opposite end of said arm is assembled on said casing. elongated beam, said mounting portion including a 10 first section connected to said beam and being dis- References Cited posed generally perpendicular to the axis of elon- UNITED STATES PATENTS gation of said beam and a second section lying in a plane generally perpendicular to said first section and 9/1951 Drelsbach' said stylus axis but spaced away from said axis of 2868892 V1959 'Keohane 179'10O'41 elongation, 3,183,311 5/1965 McAlvay 179100.41 said casing including an aperture in said side thereof FOREIGN PATENTS spaced from said coupling member, said stylus arm being assembled to said casing with said second section proectjed into said casing through said casing 8101971 aperture and engaging said casing to lock said mount- 814,015 ing portion in position and with said stylus arm extending into engagement with said coupling member; NORTON ANSHER Pnmary Examiner a damping block of resilient material having openings J. F. PETERS, Assistan Examiner.

therein for receiving and positioning said electro- 7 228,741 10/ 1959 Australia.

3/1959 Great Britain. 5/ -9 Great Britain.

Claims

1. IN COMBINATION WITH A PHONOGRAPH PICKUP WITH AT LEAST ONE MECHANICAL-TO-ELECTRICAL TRANSDUCING ELEMENT AND A STYLUS ARM WITH AN ATTACHED STYLUS COUPLED TO THE TRANSDUCING ELEMENT BY MEANS OF A YOKE MEMBER;