DE1150215B - Pickup for sampling stereophonically and monaurally recorded signals - Google Patents

Description

GERMAN

PATENT OFFICE

E 17417 IXa / 42 g

REGISTRATION DATE: 2. A P R I L 1959

NOTICE THE REGISTRATION ANDOUTPUTE EDITORIAL: JUNE 12, 1963

The invention relates to a pickup for scanning stereophonic and monaural recorded Signals with a piezoelectric bending element, which at one end by means of a elastic holder is mounted in the housing of the pickup and its free end with which the stylus bearing needle holder is connected.

The object on which the invention is based is to provide a pickup of the above type to create at which resonance vibrations the one consisting of the bending element and the needle holder Arrangement in all bending directions of the bending element are evenly damped to thereby To prevent resonance peaks in the frequency curve of the pickup.

In the case of a known pick-up, this is pizeoelectric Element sandwiched between guirnrnielernente.

In this known arrangement, the damping is not the same in all bending directions. aside from that the damping effect depends on the clamping pressure. With the pickup according to the invention sol in contrast, the damping effect can be obtained without a special one Clamping pressure is required so that it can be mass-produced without adhering to critical manufacturing tolerances can be produced with essentially always the same frequency characteristic.

This is achieved according to the invention in that the housing of the pickup has a bore is provided, in which the piezoelectric bending element is mounted, and that with the piezoelectric Needle holder aligned with bending element in a rubber-elastic bushing that fits into the bore Material is stored.

The pickup according to the invention has an extremely uniform frequency characteristic and is ideal for mass production. With him the piezoelectric Bending element damped to the same extent in all bending directions transversely to its longitudinal axis. Through this the pickup can be achieved by using a correspondingly designed piezoelectric bending element used in particular as a pickup for scanning stereophonic records will.

Another advantage of the pickup according to the invention is that it is sensitive Piezoelectric bending element by being accommodated in a bore in the pickup housing is largely protected against external damage.

Pickup for scanning

of stereophonic and monaural

recorded signals

Applicant:

Erie Resistor Corporation, Erie, Pa. (V. St. A.)

Representative: Dipl.-Ing. E. Prince

and Dr. rer. nat. G. Hauser, patent attorneys,

Munich-Pasing, Bodenseestr. 3 a

Claimed priority:

V. St. v. America April 3, 1958

Auguste L. M. A. Rouy, Scarsdale, N.Y. (V. St. A.),

has been named as the inventor

In order to achieve the damping of resonance peaks, there is no need for the pickup according to the invention special clamping pressure is required under which the piezoelectric bending element is held.

According to a preferred development of the invention, the socket is cup-shaped and carries at its open end a flange that fits into the bore of the housing, with the needle holder through through an opening in the bottom of the cup-shaped socket is while the side wall of the socket is from both the needle holder and the piezoelectric Bending element as well as from the walls of the hole has a distance.

For the assembly of the pickup equipped with a cup-shaped socket, it is advisable to to provide a shoulder in the bore against which the flange of the socket rests.

The elastic holder for the end of the piezoelectric bending element opposite the stylus is preferably carried out through an inserted into the bore of the housing, this end of the Bending element surrounding bush, which on the side facing the needle holder over has a piece of the piezoelectric element extending tapered extension.

The free space surrounding the piezoelectric bending element in the bore is expedient with a filled with damping medium.

309 600/178

The piezoelectric bending element and the damping arrangement formed by the cup-shaped socket are preferably designed so that they are in a bend transverse to the longitudinal axis of the B & geelements oppose essentially the same resistance in all directions.

The piezoelectric element and the needle holder connected to it have a PREFERENCE ₁ way in all directions transverse to the longitudinal axis of the element

effective electrical output voltage is produced, whereby the crosstalk increases will. Much of the torsional stress is wasted energy that does not produce usable power and therefore reduces the efficiency.

In the case of pickups for scanning stereophonic records, the reduction of the Crosstalk is of great importance. Because of its high modulus of elasticity compared to his

same bending resistance and are so dimensioned and io specific weight and because of its high internal

Made of such a material that the damping factor in them is preferable to magnesium. Of the

mechanical waves with the same speed- high modulus of elasticity of magnesium increases the

propagate ability. This has a further reduction in mechanical resonance frequency. The low specific

The weight of the magnesium in the cartridge according to the invention reduces the weight

there is already very little crosstalk between i ₅ attenuation requirement, which corresponds to the square of the spe-

d bid RikMl Fl hh

the two RauintonikaiiMlen result.

Finally, the needle holder can have a socket at one end, with which it is attached to the outer The end of the piezoelectric bending element is attached.

The invention is illustrated by means of two exemplary embodiments shown in the drawing ovulate closer. In the drawing is

Fig. 1 is a longitudinal section through a pickup, Fig. 2 is a section along the line 2-2 in Fig. 1,
Fig. 3 is a section along the line 3-3 in Fig. 1,
Fig. 4 is a section along the line 4-4 in Fig. 1,
5 shows a frequency curve of the pickup,
Fig. 6 the course of the crosstalk attenuation between the channels,

7 shows a plan view of a pickup with two scanning needles for two different plate speeds,

Fig. 8 is a side view of the same pickup,

FIG. 9 is a section along line 15-15 in FIG. 8, FIG. 10 is a section along line 16-16 in FIG Fig. 8,

11 shows a section along the line 17-17 in FIG. 10, and

Fig. 12 is a longitudinal section through the needle holder.
The pickup according to Fig. 1 has a housing 1, which can preferably be molded from plastic and has an outer shape that is in the tonearm, in the

specific weight changes. The high internal damping of the magnesium reduces the need for additional damping. The only other Metal, whose properties are comparable to those of magnesium, is beryllium, that of magnesium probably a bit superior, but is more expensive. The same properties can be found with glass-reinforced Plastics, but not with plastics alone, as these have a low level of rigidity.

The needle holder is symmetrical about its longitudinal axis, so that its mechanical properties in are the same in all directions around the longitudinal axis. In other words, the moment of inertia of a cross-section with respect to an axis at any right to the longitudinal axis Angle standing direction is constant. This is particularly important for pickups for sound reproduction important, because the response characteristics for both channels must be the same for these, so that distortion occurs be prevented.

The upper end of the needle holder 7 is equipped with a socket 8 (Fig. 3) which telescopes over the front free end of a piezoelectric bending element 9 is pushed. The flexure can be glued directly to the inner surface of the mount 8, but an intermediate layer 10 can also be made Paper or other insulating material, e.g. B. enamel, between the inner surface of the socket 8 and the loaded

tion with a section 3 of reduced durometer <on the front part and a section 2 of larger diameter. Between the two sections lies the shoulder 4.

The stylus 5 is attached to a needle holder 7, which is preferably made of a cylindrical or tubular magnesium rod. The stylus is as close as possible to the longitudinal axis of the

Adjacent surfaces of the bending element provided they are to be installed, fits. Be 45 in the longitudinal direction. The bending element 9 preferably has the shape of the housing, extends a cylindrical boring of a rod of cruciform cross-section and consists of a polarized, piezoelectric, ceramic material such as barium titanate. The cruciform bending element has four radially projecting, axially running, mutually perpendicular ribs 11, between which electrodes 12 and 13 are located, which are diametrically opposed in pairs and centered on two mutually perpendicular axes. The ceramic material of the bending element is fastened in the needle holder, thus torsional forces which are polarized to 55 in the direction of the arrows 14, 15, 16 and 17. Crosstalk phenomena from channel to channel Corresponding to this polarization, between the leads will be minimized. Electrodes 12 generate a voltage when the one twist of the piezoelectric bending element is bent about the axis 18, selectable element by deflection of the scanning needle, which generates a voltage between the electrodes 13 through one or the other channel on the sound 60 When the bending element is caused to plate around the axis 19, a torsional chip is bent. The magnitude of the stresses generated in the bending element. That caused by the torsional is proportional to the amount of bending. The electrical voltages generated by the measurement voltage would cancel out the mechanical properties of the cruciform bending in an element of perfect symmetrical elements are trie in all directions around the longitudinal axis and of an absolutely linear formation, i.e. the deflection properties are negated, but there is such a perfection in relation to axes 18 and 19 the same.
Not achievable in practice, and this has the consequence that, in addition, the needle holder 7 and the piezo

due to the torsional stress in both channels an electrical bending element 9 constructed so that in

they propagate elastic deformation waves at the same speed. This becomes a partial Prevents reflection at the junction between the needle holder and the bending element, which could lead to cross-talk between the channels. This condition of equality the speed of propagation is satisfied by the following equation:

E _{7 =} E I _{1 9/9}
S ₁ F ₇ S ₉ F ₉

Are in it

E ₁ , Eg is the modulus of elasticity of the materials of the needle holder 7 and the bending element 9,

S ₇ , S ₉ the specific weight of the materials of these parts,

I ₁ , I _{0 are} the moments of inertia of the cross-sections of these parts with respect to any axis at right angles to the longitudinal axis, and

F ₁ , F ₉ areas of their cross-sectional areas.

The bending element 9 is bent by the stylus 5 only about the axes 18 and 19, these Displacements are independent of one another. The cross-talk between the channels is in a decomposition the signals in the piezoelectric bending element are more favorable than with a mechanical dismantling of the Needle movement in components that act on separate piezoelectric flexures.

The end of the ceramic bending element 9 facing away from the needle holder 7 is inserted into a rubber bushing 20 inserted, the outer diameter of which is essentially the same as the diameter of the section 2 of the hole in the housing 1. This rubber bushing 20 has a tapered extension 21 of smaller diameter than that of section 2. This prevents a sudden concentration of stress in the ceramic element and also reduces the reflection of elastic deformation times. the Rubber bushing 20 has in the middle an opening 20 a for receiving the bending element, which corresponds to the outer contour the same is adapted and pairs of opposing conductors 22, 23 and 24, 25 against the associated Electrode pairs 12 and 13 presses. The conductors 22, 23 are the output lines for the one channel, while the conductors 24, 25 represent the output lines for the other channel. the Rubber bush 20 has the same rigidity in all radial directions.

When the frequency of vibration of the stylus 5 is a natural vibration number of the flexure mechanical resonance occurs, which is an undesirable peak in the frequency curve generated. To reduce this resonance peak, damping is required. With this one Pickups have two resonance frequencies within the audio frequency range. The lower one this resonance frequency corresponds to a 2/4 oscillation in which the bending element 9 and the needle holder 7 swing as a cantilevered beam. This occurs at a frequency between 6000 and 8000 Hz. The next higher frequency corresponds to a 2/2 oscillation in which the bending element 9 and the Nadelhaliteir 7 as clamped on both sides Bearers swing. The frequency of the 2/2 oscillation is between the present pickup 15,000 and 16,000 Hz. The higher resonance vibrations lie above the audio frequency range.

The resonance vibrations are made up of the internal friction of an elastic member, e.g. natural or synthetic rubber, and dampened by viscous friction of a dampening fluid. The rubber damping element is designed as a pot-shaped socket27 with a

to the outwardly projecting flange 26 which is glued to the shoulder 4 between the sections 2 and 3. The side wall of this socket surrounds the needle holder Ί, being at a distance from this needle holder as well as from the wall of the section 3 with a narrower diameter. A hole 29 is provided in the lower wall 28 of the socket, through which the needle holder 7 protrudes and in which it is glued to the socket. The vibration of the flexure is transmitted through the lower wall 28 of the socket and is dampened by the deformation of the side wall. The lower wall 28 lies between the scanning needle 5 (which would have the greatest deflection in the case of the 2/4 resonance oscillation) and the node for the 2/2 resonance oscillation. This arrangement results in adequate damping for both types of vibration. The side wall of the bushing is made thin so that there is little resistance to vibration and the damping is primarily caused by the internal friction in the rubber. Since there is no sliding friction whatsoever, the damping characteristics are very constant.

The pot-like socket 27 also büdet one flexible seal for the bore of the housing and thus prevents leakage of the damping medium, which is filled through a hole 30 in the housing which is then closed by means of adhesive 31. The damping medium fills the whole Cavity around the bending element 9 and causes a viscous damping. The damping medium preferably has one above normal Temperature range essentially constant viscosity, so that its own damping properties by the Temperature are not affected. As the thermal expansion properties of dampening liquids are different than for plastics, precautions must be taken for thermal expansion will. In the present case, these consist in the fact that the side wall of the pot-like socket is flexible is. Due to its ring-shaped cross-section, it is largely isotropic over its entire length.

Fig. 5 shows a diagram in which the sensitivity of the pickup as a logarithmic function the frequency is shown. From this diagram it can be seen that the sensitivity curve is about runs smoothly over the entire range from 30 to 20,000 Hz (far right end of the curve). It is neither with the mechanical 2/4 there is still a peak at the 2/2 resonance frequency of the pickup.

In this diagram, that of a stereophonic test record with cut into a common groove Test frequency was recorded, the sensitivity of the pickup is in dB above and plotted below the theoretical input power. The fall to very low frequencies towards the impedance of the measuring circuit fed by the bending element is attributable. The effect of this impedance is at low fre-

Claims (8)

sequences are greater, and form the slope of the curve when the assembly kit is low. As shown in Fig. 8, therefore, frequencies are to be expected. are the plastic parts 97, 98 at right angles to to determine the crosstalk were the Abtastmadeln 85, bevelled 86, wherein the measurements made in one of the channels protrude currency needle tips from the housing. Each end of the stylus followed a sound groove, the plastic part is equipped with a groove 99, which finally allows an oscillating movement of the needle holder to excite the other channel. Curve 33 shows the voltage im when the stylus follows the sound groove. Each of the artificial right channels is provided on a left channel when scanning an oscillation of the intermediate section of the housing, while curve 34 shows the tension material parts 97, 98 with a semicylindrical Ausini right channel when scanning an oscillation of the io sparse 100. Both recesses form the left channel. In the area of low frequency, the cylindrical chamber, which the piezoelectric sequence, in which the crosstalk between the bending element 88 surrounds. In each recess a channel is strongest, it is, as can be seen, formed on annular groove 101 , which kept the edge 96 of a low value. Although the clay pot receives socket 94 , which is designed in such a way that it is glued into it in a liquid-tight manner. The response properties are the same in all directions - rubber bushing 89 is in semi-cylindrical grooves 102 , crosstalk phenomena can occur as a result of glued in, of which each with a keyway 103 manufacturing tolerances occur. It can be equipped with a wedge-shaped web 104 with the bushing from a softening in the cross section of the needle holder or the piece, piezoelectric bending element occur, and it is 20 These keyways 103 set the angular position of the possible that the bending element and the Sensing needle piezoelectric bending element with respect to each other or with respect to the sound groove not rieh- housing. At the rear end of the housing tig are aligned or the electrodes are incorrectly an annular groove 105 in which a clamps are arranged or in their size from the target value disc 106 is inserted, the four deviate symmetrically. 25 arranged contact pins 107, 108, 109, 110 (FIG. 11) In FIGS. 7 to 12, a pickup can be selected which, before gluing the plastic parts together, is used for stereophonic and material parts 97, 98 with the lines 90 to 93 shown elecaural rendering, the two scanning needles are trisch connected. After the assembly for playing records with different, the from the faalb-cylindrical recesses has nominal speeds. 30 100 formed by a chamber not shown.This pickup is accordingly filled with damping fluid for all openings and on records of the types produced so far and the opening is closed, also suitable for the newer single-groove stereophonic records located at the outer end of the tonearm. The pickup holder consists of a one-piece The stylus holder 80 is a magnesium rod of 35 supporting structure with fastening brackets HOa. circular cross-section and has at its äuße- ^{At the} rear end of the support structure is ren end diametrically opposite, flat Fla- ^a connection plate 111, the four symmetrically with chen Si and 82, each arranged at an angle from each other, by rivets 113 approximately 30 ° to the longitudinal axis of the needle holder fixed contacts 112 carries, of which electrical are inclined. In each of these flat surfaces there is a 40 lines going off. Each of the contacts 112 has a needle holder 83, 84 for receiving a resilient, tangential extension 114 for a scanning needle. These 85 and 86, respectively, are provided. Extensions 114 provide, as Fig. 11 shows that at the inner end, the needle holder 80 to connect with the associated pins 107 to 110 replaced by 87, in which the outer end of piezoelec- ^ner · ^{The pins 107 to 110 könnei1} to the Irish flexure 88 are rotated with cross-shaped cross-45 contacts 114 and connect with this cut is glued. The biage element 88 can be ^{polarized as if it is in} contact when the relative position is shown in FIG. 3. Approach the piezoelectric ^Fi S · ⁿ . At the front of Tonabneh-Biageelement is oriented such that the ^sample-mers there is an annular portion 115 of the needles, the 85, 86 with both the axis 18 and leads to the front end of the pickup. Include an angle of 45 ° at the rear of the axle 19. The other end of the piezoelectric flexible-cylindrical section 116, which guides the rear end of the element 88 in a cylindrical rubber bushing of the pickup, is located on the side of the pickup carrier. Received between the ring section 89, which presses the lines 90, 91, 92 and HS and the cylindrical section 116 , a 93 is pressed against the electrodes of the bending element. U-shaped clamp 117 with arms 118 and 119 be-About the needle holder 80 , the bottom wall 95 of a 55 is fixed, which is pushed on the flat surfaces 120 of a pot-like socket 94 and glued to the narrowed portion 121 of the pickup. This Burihse has an outward attack under spring pressure on both sides. A rotation of the protruding edge 96 and side walls 96 a, that of the pickup by 180 ° from the one needle position along the piezoelectric bending element 88 to the other can be carried out with the help of an arm 122 and at a distance from this from the needle holder 60, which with the plastic parts 97, 98 extend off away. The parts described can consist of one piece. assembled outside the pickup The mode of operation of the device described in FIGS. 7 to 12 will. cartridge is the same as the one in The housing of the pickup consists of two symmetrically shaped plastic parts 97, 98 shown in FIG. 1, the 65 are glued together and a sealed connection. PATENT CLAIMS: scMuss- and support housing for the signals recorded phonically and monaurally from the piezo 1. pickup for scanning stereo-electric bending element and the needle holder with a piezoelectric bending element which is mounted at one end by means of an elastic holder in the housing of the pickup and whose free end is connected to the needle holder carrying the stylus, characterized in that the housing of the pickup is provided with a bore in which the piezoelectric bending element (9, 88) is mounted, and that the needle holder (7, 80) aligned with the piezoelectric bending element is mounted in a bushing (27, 94) made of rubber-elastic material that fits into the bore. 2. Pickup according to claim 1, characterized in that the socket (28, 94) is cup-shaped is trained and on. its open end has a flange (26, 96) which extends into the bore of the housing fits, and that the needle holder (7, 80) through an opening in the bottom of the cup-shaped Bushing is passed through, while the side wall of the bushing is both from the needle holder and one of the piezoelectric flexure and the walls of the bore Distance. 3. Pickup according to claim 2, characterized in that the flange (26) of the socket (27) rests against a shoulder (4) provided in the bore. 4. Pickup according to one of the preceding claims, characterized in that the elastic holder for the end of the piezoelectric which is opposite the stylus Bending element through an inserted into the bore of the housing, this end of the bending element surrounding bushing (20) is formed, which on the needle holder (7) facing Side a conical one extending over a piece of the piezoelectric element Extension (21) has. 5. Pickup according to claim 4, characterized in that the piezoelectric bending element surrounding free space in the bore is filled with a damping medium. 6. Pickup according to one of the preceding claims, characterized in that the piezoelectric bending element and the damping arrangement formed by the cup-shaped socket are designed so that they have a bend transverse to the longitudinal axis of the bending element in alen Opposite directions essentially the same resistance. 7. pickup make one of the preceding claims, characterized in that the piezoelectric bending element and the needle holder (7, 80) connected to it in alen Directions transverse to the longitudinal axis of the bending element have the same bending resistance and so sized and made of such material that they have the same ratio as Product of the modulus of elasticity and the moment of inertia of the cross-section with respect to a Longitudinal axis perpendicular to the product of the specific weight and the area have the cross-sectional area. 8. Pickup according to one of the preceding claims, characterized in that the The needle holder (7, 80) has a socket (87) at one end with which it is attached to the outer end of the piezoelectric bending element is attached. Considered publications:
U.S. Patent No. 2,313,129;
French patent specification No. 1 085 764. 1 sheet of drawings © 309 600/178 6.63