FR2517098A1 - READING ARM FOR ELECTROPHONE - Google Patents

Abstract

THE READING ARM INCLUDES A LEVER1 CARRYING A READING HEAD11 AND ASSOCIATED WITH A SET FOR CREATING THE PRESSURE FORCE, TWO SUPPORTS OPPOSITE ONE OF THE OTHER2 AND 3, ONE OF THE SUPPORTS BEING MOBILE AND LINKED TO THE LEVER1 WHILE THE OTHER IS FIXED, A VERTICAL PIVOT4 AND A BALL6. THE PIVOT4 IS FIXED TO ONE OF THE SUPPORTS2 OR 3 AND COOPERATES WITH A SPHERICAL STOP MOUNTED IN THE OPPOSITE SUPPORT3 OR 2, THE BALL6 IS ARRANGED BETWEEN THE SUPPORTS2 AND 3 IN SUCH A WAY THAT IT TOUCHES ONE OF THESE SUPPORTS AND COOPERATES WITH A PRACTICAL GUIDING ELEMENT (SLOT8) IN THE OTHER SUPPORT.

Description

Tonearm for electrophone.

  The present invention relates to a tonearm

for electrophone.

  The proposed tonearm can be advantageous-

  ment applied in electrophonic devices of

  high fidelity sound reproduction (Hi-Fi).

  We know tonearms with support pivot

  having a weak moment of the reaction forces to the rota-

  tion of the tonearm in a vertical plane and / or in a horizontal plane (see for example the patent of R F A. no 1171170, the French patent no 1448146, the patent of

Great Britain no.1019603).

  In such tonearms, the suspension comprises

  carries a support pivoting around the geometric axis ver-

  tical and carrying pivots to which is mounted a tonearm support, rotating relative to an axis

  of horizontal geometric rotation passing through said pi-

  votes, this suspension thus presenting a construction

  double joint Two pairs of special bearings

  liers allow, in these devices, the rotation of the arm

  of reading, respectively around the geometric axis ho-

  rice and around the vertical geometric axis, which increases the inertia of the tonearm given the need to overcome static friction during its movement.

  up-down and its lateral movement during playback.

  The tonearms of this design are laborious and complicated technology and their adjustment is difficult. There is a tonearm, like the one described

  in US Patent No. 2,998,698, simpler to manufacture

  quer and adjust, which includes a suspension made according to the principle of support at a single point This tonearm has a lever carrying, at its end, a readhead, and associated with a set of creation of the

  pressing force The lever acts as a mo-

  bile of the tonearm suspension, it has an opening above which a pivot support is fixed, in the form of a spherical stop A needle with a sharp top (pivot) is mounted vertically on a fixed suspension support (support permanently mounted on a panel of the electrophone), passes through the holes in the lever, and cooperates with said spherical stop The geometric axis

  vertical rotation of the lever passes through the point of in-

  teraction of the sharp top of the needle and the spherical stop. However, this known tonearm is characterized by high friction during the movement of the tonearm in the two planes, vertical and horizontal; therefore, it has poor characteristics for following the movement because of an inevitable play between the needle and the walls of the orifice of the tonearm; the arm of

  reading cannot therefore be stabilized longitudinally.

  In addition, in this tonearm, as indeed in all the other tonearms mentioned, the set of creation of the pressure force only makes it possible to create an invariable pressure force when reading <c ' that is, the pressing force cannot vary as the tonearm moves toward the center

  of the disc read, nor according to the unevenness of the over-

face of the disc).

  However, it is known that the phonogram becomes more and more tight when passing from the periphery towards the

  center of the disc when recording the same signal.

  So the sides of the groove of the disc become more and more steep in the direction towards the center, and the force

  tonearm pressure must vary accordingly

  dance (in this case, increase) as the tonearm moves toward the center of the disc when playing

reading.

  For example, to read the initial furrow turns, for stable tracking of the furrow, a pressure force of 0.5 g / min may be necessary (this

  which is good enough for modern readers

  weight of the mobile crew of 10,103 m / Nl, and for the

  reading of the final groove turns this force must increase

  lie up to 0.8 g / min due to the tightening of the phono-

  gram So the pressing force must grow gradually

  when reading a value of 0.3 g or even being equal to a constant value of 0.8 g during all

  the reading process Now, in the latter case, a usu-

  excessive re will take place in the starting area of the disc and a method of reading with progressive growth of the pressing force will undoubtedly be preferable. However, a modification of the known tonearms with mentioned construction suspensions carried out

  by providing them with a means of varying the press effort

  may cause degradation of the characteristics

  techniques of the suspensions themselves, in particular an increase

  considerable mention of friction to the axes.

  We therefore proposed to perfect the suspen-

  sion of the tonearm so that during the movement of the tonearm, the undesirable friction is significantly weakened and that the tonearm can be equipped with a means of varying the pressing force

  during reading, which will have the advantage

  improved reading fidelity and increased

  longevity of discs and styli.

  According to the invention, the reading arm comprises a lever carrying a reading head at its end and an assembly for creating the pressing force; of them

  supports arranged one opposite the other, one of which mo-

  bile, is made in one piece with the lever and the

  tre, fixes, is intended to be fixed to an electrical panel

  trophone: a vertical pivot immobilized in one of the supports and cooperating with a spherical stop in the opposite support, the geometric axis of rotation of the lever passing through the point

  interaction of the pivot and said stop; and it is charac-

  terized in that there is provided, between said supports, a ball to which one of the supports is tangent and which cooperates with a guide element produced on the other support, the horizontal geometric axis of rotation of the lever being formed by a straight line passing through the point of interaction of the pivot and the spherical stop and the point of contact

of the ball and the tangent support.

  It is advantageous to produce the guide element

  in the form of an arcuate slot made along a circumference

  ference whose center is on the geometric axis ver-

  tical. The guide element can be in the form of a spherical cell, the radius of the sphere somewhat exceeds the radius of the ball, or else in the form of two equidistant curved projections; in this

  last case, an additional guide element must be executed

  on the opposite support just opposite the pre-

mier guide element.

  To ensure a variation in the pressing force

  When reading, it is preferable to carry out the assembly for creating the pressure force in the form of a magnetic couple comprising a magnet and a ferromagnetic element separated from the magnet by a gap, one

  elements of the magnetic couple must then be rigi-

  dement linked to the mobile support and the other, to the fixed support.

  In case the two supports each have a guide element, it will be advantageous for the magnetic torque element rigidly connected to the fixed support to be arranged in such a way that the magnetic flux of the magnetic couple passes through the normal, cutting the axis. vertical geometric, at the bisector of the angle formed Dar the extreme positions of the horizontal geometric axis that it occupies during the pivoting of the tonearm lever on its full rotation angle around the necessary vertical geometric rotation axis to make

reading the entire phonogram.

  The tonearm produced according to the invention is characterized by: high reading fidelity; appreciably reduced friction in the suspension; a possibility of varying the pressure force during reading; the ability to compensate for the force

  according to the law of its variation, this possibility

  due to the provision of electro-

  magnet of the press force creation set

  sion with respect to the geometrical fxes of the read arm

ture.

  It should be noted that the device according to the invention

  - tion, thanks to a simple and original construction of the

  tonearm suspension, provides minimal friction

  poor vertical and horizontal tonearm rotation axes, less than 7 mg; this index is better than in most of the best known tonearm models. A wide variety of constructive embodiments of the device makes it possible to obtain several different modes of

variation of the pressure force.

  The tonearm is easy and simple to manufacture,

  since it contains a quantity of parts

  about twice as low compared to mo-

  known models, the main parts being produced by molding and punching The tonearm according to the invention makes it possible to reduce the dimensions

of the whole reader.

  The combination of minimal friction on the geometrical axes

  tonearm rotation triques and the possibility of adjusting the pressing force as well as all

  other advantages which ensue, provide per-

  formances of the construction in question which allow

  use it in higher class electrophones.

  In what follows the invention is made clearer

  in the description of the modes of its concrete realization

  made with reference to the accompanying drawings in which, Figure 1 shows a tonearm, seen from above; Figure 2 is a section along II-II of Figure 1, the guide member being formed on the fixed support;

  Figure 3 shows part A of Figure 2, the element

  guide ment being on the fixed support; Figure 4 is an embodiment of the tonearm providing compensation for the recoil force, plan view;

  FIG. 5 is a diagram of distribution of the

  these acting on the tonearm, for the embodiment shown in FIG. 4; Figure 6 shows an embodiment of the arm 6 - reading o the guide element is in the form of a spherical cell formed in the fixed support, seen in plan; Figure '7 is a section along the line VII-VII in Figure 6; Figure 8 shows the same embodiment as in Figure 6, but said cell is formed in the movable support; Figure 9 is a section along the line IX-IX in Figure 8; FIG. 10 is a diagram of variation of the pressure force acting on the tonearm shown in FIGS. 8 and 9; FIG. 11 is a diagram of variation of the recoil force in the tonearm; Figure 12 shows an embodiment of the bres

  where both supports have a guide element

  each one, plan view; Figure 13 is a section along the line XIII-XIII in Figure 12; figure 14 shows the force creation set

  pressure, view according to arrow X in FIG. 12.

  The tonearm shown in Figures 1 and 2 includes

  carries a lever 1, a fixed lower support 2, immobilized on a panel of the electronic phone (not shown), a mobile upper support 3 produced in one piece with the lever 1, a vertical pivot 4 fixed, in the mode

  of realization considered, to the immobile support 3 and co-

  operating with a spherical stop 5 of the support 2 A ball 6 is arranged between the supports 2 and 3 so that it touches a support plate 7 of the support 2 and cooperates with

  a guide element, in the embodiment considered

  déré, with an arcuate slot B The vertical geometric axis' aa of rotation of the tonearm of the lever 1 passes through the point of interaction 9 of the pointed end of the pivot 4 with the stop 5 and the horizontal geometric axis bb of rotation of the lever is formed by the straight line passing through the same point 9 and the contact point 10 of the ball 6 7 - and of the support plate 7 of the support 2 The generatrices of the arcuate slot 8 are circumferences whose

  common center is located on the vertical axis a-a and the long

  slot 8 is chosen sufficient to move

  easy to lever 1 through the entire phonogram from the starting turns of the groove to the final turns At one end of the lever 1 is mounted a read head 11 and at the other end of this lever is installed a set 12 for creating a force

  pressure of the read head 11, in the case

  déré this set is a counterweight The point "O" in figure 1 shows one of the possible positions of the center

of the tonearm gravity.

  When the reader's needle passes through the elevations

  elements of the disc, in other words, during the movement of the head 11 of the reader in a vertical plane, there is a rolling of the active surfaces of the pivot and of the ball

  6 (point 9 and point 10, respectively) on the sur-

  bearing faces of the plate 7 of the support 20 Thanks to the proposed construction of the tonearm, a considerable reduction in the friction on the horizontal and vertical axes of the tonearm is obtained thanks to

  the absence of any source of sliding friction.

  On the vertical and horizontal axes of the tonearm acts the

  rolling friction of the mentioned bearing surfaces.

  The moment of frictional forces on the support of the tonearm is considerably reduced, which ensures a displacement without braking of the reader on the disc. The friction obtained translates into effort to be applied to the tip.

  of the read head is approximately 5 mg.

  Figure 3 also shows an alternative mounting of the ball 6 The slot 8 in this embodiment is made in a fixed lower support 13, the plate 7 of the movable upper support 14 in this case rests on the ball 6 in the point The guide element can be produced in several variants, for example, in the form of a loop fixed to one of the supports, etc. The construction in question eliminates the play taking place in the construction constituting art 8 -

  earlier, this removal of the game improving the character-

  of the reader thanks to the increase in the rigidity of the construction, the decrease in the imbalance of

  reading head tracks, as well as contributes to the am-

  improvement of the near-crosstalk weakening between the channels, lowering the rate of fluctuation and also makes it possible to achieve longitudinal stabilization of the arm

of reading.

  In the embodiment of the tonearm shown in FIGS. 4, 5 there is a useful distribution of the frictional forces appearing during the rotation of the tonearm around the vertical axis aa, thanks to which we have obtained the recoil force compensation effect.

  In this embodiment of the device, unlike

  ference mode, its embodiment shown in Figures 1, 2, the length of the slot 8 is somewhat less than

  sufficient length to move lever 1 through

  towards all the phonogram recorded on the disc, and one of the supports, in this case, the mobile support 3 is mounted with an inclination to the support 2 in the opposite direction-to the direction of movement of the lever 1 during reading. If the phonographic discs and the disc playback devices do not create a radial beat of the recorded phonogram (eccentricity of the central hole by raynort to the thonogram), one could compensate the recoil force by a simulated increase Tentation of the friction at the vertical axis of the arm

of reading.

  However, practically every disc has an eccentric

  tee of the central hole with respect to the phonogram field and

  the tonearm during the reading movement

  back and forth And moreover, when moving the tonearm from the center of the disc to the edge at the

  recoil force - adds friction to the vertical axis.

  To overcome these drawbacks we try to reduce

  in electrophones of all types at least the friction

  tement to the vertical axis, which is obtained U by means of J

25170-98

  9 - expensive processes (for example, using sapphire balls in ru cages in ru Dis) and the compensation of the recoil force is carried out by applying a compensation force of opposite direction and of value equal to the using springs, magnetic forces

or gravity.

  In the tonearm embodiment shown in Figures 4, 5 the force compensation

  reversing is carried out as follows.

  Either support 3 with a read head 11 y

  fixed and a counterweight 12 pivots around the vertical axis

  cal a-a of the tonearm when moving the lever 1 towards the center of the disc in the direction shown by the arrow B Then, the ball 6, abutting against the edge 15 of the slot 8, moves with sliding friction

on the plate 7 of the support 2.

  The value of the sliding friction force, determined by the position of the counterweight 12, that is to say, by the position of the center of gravity "to" t, is chosen equal to the value of the force of retreat and is directed in opposition to the latter, thanks to which

the recoil force is compensated.

  When the lever 1 moves away from the center of the disc in the direction of the arrow C (due to an eccentricity) the support 3 recedes. The ball 6 moves (rolls) on the plate 7 of the support 2 without sliding friction, with minimal rolling friction. In this case, the anti-kickback torque appears due to the fact that at least one of the bearing surfaces of the upper or lower support, in the given case, of the support 3

  (see figure 5) is executed oblique.

  In this way, when moving the lever 1 forward, towards the center of the disc, the recoil force is compensated for by the sliding friction between the ball 6 and the plate 7 of the support 2 At the time of stopping and during the movement lever 1, back, away from the center of the disc, said recoil force is compensated by the force F which is one of the components of - gravity P. In Figures 6 and 7 we can see shown an embodiment of the tonearm in which, unlike the embodiment of the invention shown in FIGS. 1 and 2, the guide element has

  in the form of a spherical cell 16 with a radius exceeding

  sant a little the radius of the ball 6 and made in the sup-

  fixed port 3 In addition, in this embodiment of the device, the assembly for creating the pressure force of the read head 11 is produced in the form of a

  magnetic couple: of an electromagnet 17 and,: of an arma-

  ture 18 separated from the electromagnet 17 by an air gap.

  The electromagnet 17 is fixed to the fixed support 3 and the arma-

  ture 18, to the movable support 2 (the arrangement of the elements of the magnetic couple can be reversed: the electromagnet

  17, on the support 2 and the frame 18, on the support 3).

  The frame 18 is fixed with a screw 19 The electro-

  magnet 17 can be fixed at different points on the support

  3, for example, in positions I, II and III.

  When the tonearm 5 is operating (swivels

  in the direction indicated by arrow D) the support

  3 slides on the ball 6 and the ball 6 remains

  movable with lower support 2.

  The dotted line shows in the drawing the arrangement

  tion of lever I when moving towards the center

of the disc.

  The variation of the pressure force during the

reading is ensured as follows.

  When the tip "K" of the read head is on the initial groove turns, the pressure force I is determined by the relation: F 2 12 o: F 1 is the pressure force, 11 is the arm

  of action of the wave F 1, that is to say, the distance between

  rant the tip of the horizontal axis b-b of the tonearm, F 2 is the force developed by the electro-magnet 17 (F = const); 12 is the arm of action of the force F 2, that is to say, the distance separating the electromagnet 17 from the horizontal geometric axis (bb) of the arm of it - reading The electromagnet 17 is fixed in position I. EE is the position of lever 1 at the initial turns of the groove of the phonogram; H-H is the position of lever 1 at

  final turns of the phonobram groove.

  When the point "K" is moved from position E to position H, the value l%, or the action arm of force F 1, is increased by a value N 11, the arm 12 does not vary and, consequently, the pressure force F decreases The analogous relationship to the forces and arms of their action takes place in case the electromagnet is placed at other points of the support (for example, at the position

II or III).

  Figures 8, 9 illustrate another possible mode

  of the tonearm In this case, unlike

  ference of the previously described case, the guide element, the spherical cell 20, is produced in the upper movable support 3 and during the movement of the lever 1, the ball 6

  moves with the support 3 relative to the fixed support 2.

  During the operation of the tonearm with an electromagnet 17 occupying position I, the action arm of the force F 1 does not vary while the arm 12-I increases;

  therefore, for an F = const the value of F 1 also increases.

  At position II of the electromagnet 17 (the electro-

  magnet 17 is rotated by a certain angle), during operation

  operation of the tonearm, the action arm 11 of the force F 1 does not vary and the arm 12-II increases first, then, after having reached a certain maximum value, 12-I Imax 'decreases and becomes equal at the initial value 121 II; directly proportional pressure force F 1

  to the value of the variant analogously.

  This is apparent from the variation diagram of the pressure force FP shown in FIG. 10 where the pressure force F 1 is plotted on the ordinate, and the radius of the reading groove in millimeters is plotted and abscissa, R being the radius of the turn initial groove and R 2,

  the radius of the final groove.

12 -

  The embodiment of the invention considered as-

  on compensation of the recoil effort in accordance

to the law of its variation.

  From the literature, it is known that the recoil force F 3 in electrophones varies according to a very complex law illustrated in FIG. 11 and depends on the value of the pressure force F.

  The main difficulty in developing

  thinkers of the recoil force F 3 is to create a

  compensation effort varying according to the variation of F 5.

  Table 1 gives the recoil force ratio

  F 3 / reading radius R for the case where the press force

  sion F 1 is constant, table II gives the force relationship

  reversing F 3 / reading radius R in case the pressing force

sion F 1 is variable.

Taule I Table II

-3 -1 3

R 1.0 0.12 R 1 1.0 0.12

R 2 1.0 0.1 RR 2 1.2 0.12

R 5 1.0 0.12 R 5 1.0 O, 12

  We see in table I that the minimum value

  F = 0.1 exists at the mean radius R 2 of the groove.

  On table II we see that if the construction of the tonearm ensures an automatic variation of the pressure force F 1, the recoil force F 3 will have a value

  constant over the entire area occupied by the phono-

  gram of the disc, independently of the radius R of the furrow read and the compensation of this recoil force by an equal force in value and of opposite direction will make a problem easy to solve, the solution being realized in the majority

existing electrophones.

  At position III of the electromagnet 17, during the operation of the read arm, the force action arm 11 F 1 does not vary, the force action arm 12

  F 2 decreases, and the pressure force F 1 decreases in cor-

  correspondence. In the embodiment of the reading arm shown 13 - in FIG. 12, 13, the guide element is made in the form of equidistant arched heavens 21 arranged on the support 3 and passing through the circumferences whose center is located on the vertical geometric axis, aa, and on the support 2 is provided an auxiliary guide element in the form of two equidistant arc projections 22 identical to the main guide element and arranged opposite the latter In this embodiment of the device during the rotation of the lever 1 (1 the ball 6 is moved relative to the two supports 2 and 3 This movement gives rise to the following variants of relationships of the arms 11 and l, depending on the position of the electromagnet 17 (In the drawing the references 25

  and 24 denote fixing screws).

  At position I of the electromagnet 17, as the lever 1 moves towards the final turns of the groove of the disc, the action arm 12 of the force F 2 decreases faster than the action arm 11 de-la force FD Since the pressure force F 2 12 eni cas F 1 1 o 12 a 1 IF 2 will grow gradually but not as fast as in the variant shown in the figures

7 and 8.

  At position II of the electromagnet 17 the variation of the arm 12 will be less significant than that of the arm 11 and,

  therefore, the pressing force F 1 will decrease.

  At position III of the electromagnet 17, the arm 12 IIII, unlike the two previous cases (positions I and II of the electromagnet 17), gradually decreases, which results in a gross decrease in the strength of

pressure F 1.

  The most advantageous position for fixing the electromagnet 17 is that which conditions the passage of the maximum magnetic flux of the magnetic couple through the normal, intersecting the vertical geometric axis a-a, at the bisector.

  of the angle formed by the extreme positions of the geometrical axis

  horizontal stick b-b that the latter occupies during the rotation-

  full tone arm around the geometric axis 14 -

  vertical a-a necessary for reading the whole phono-

  gram of the disc, In all the constructive embodiments of the invention described above, the force developed by the magnetic couple contributes to the proper distribution of the vertical pressure forces on the bearing elements of the suspension: the pivot 4 , the stop 5, the guide elements, the ball 6 It should be noted that the absence of any harmful lateral pressure on said elements of the suspension allows the tonearm to keep its

  high technical and service performance.

  The constructive embodiments of the invention

  represented allow to ensure various laws of va-

  pressure force, the advantage which can be useful to achieve various goals that arise during the

  development of new readers, for example, to compensate for the recoil force in accordance with its law of variation or (and) for the automatic variation of

the value of the pressing force.

  FIG. 14 represents an embodiment of an electromagnetic device for the creation of the force

  pressure (view along arrow L in Figure 12).

  The electromagnet 17 is fixed to the fixed support 2 by the screws 23, 214-, the armature 18 is mounted on the lever 1 One can conceive of other versions of reciprocal arrangement of the electromagnet 17 and the frame 18, for example, frame 18 can be installed on support 2 and

  the electromagnet 17, on the lever 1.

Claims (5)

  1 tonearm of the type comprising: a lever (1) carrying a readhead (11) at its end and associated with an assembly for creating the pressure force; two supports (2, 3) arranged one opposite the other, one of which is fixed and made in one piece with the lever (1), and the other is movable and is intended to be attached to a panel of the recorder; a vertical pivot (4) fixed to one of the supports (2 or 3) and cooperating with a spherical stop (5) formed in the opposite support (3 or 2), the geometric axis of vertical rotation (aa) of the lever (1) passing through the point of their interaction (9); characterized in that it is provided between said   supports (2 and 3), a ball (6) touching one of the supports   ports (2 or 3) and cooperating with a guide element arranged on the opposite support (3 or 2), the horizontal geometric axis (bb) of rotation of the lever (1) being formed by the straight line passing through the point (9 ) interaction of the pivot (4) with the spherical stop (5) and by the point (10)   of contact of the ball (6) and the support (2 or 3).   2 tonearm according to claim 1, characterized in that said guide element is produced in the form of an arcuate slot (8) whose generator is   a circumference whose center is on the geo-axis vertical metric (a-a).   3 tonearm according to claim 1, ca-   characterized in that the guide element is produced in the form of a spherical cell (16, 20), the radius of which   the sphere slightly exceeds the radius of the ball (6).   4 tonearm according to claim 1, ca-   characterized in that said guide element is produced in the form of two equidistant curved projections (21),   and in that, on the opposite support, there is provided an element   additional guide ment (projection 22) identical to   first and arranged in opposition to it.   Tonearm according to any one of claims 1 to 4, in which the assembly for creating the pressure force is in the form of a couple 17098   magnetic comprising a magnet and a ferromagnetic element   tick separated from the magnet by an air gap, characterized by   that one of said elements constituting the magnetic couple   tick is rigidly linked to the movable support (3) of the   seems and the other, to the fixed support (2).   6 tonearm according to claims 4 and   , characterized in that the element of the magnetic couple rigidly connected to the fixed support (2) is arranged in such a way that the maximum magnetic flux of the magnetic couple passes through the normal, intersecting the vertical geometric axis,   at the bisector of the angle formed by the positions ex-   tremes of the horizontal geometric axis (b-b) during pi-   complete voting of the tonearm lever (1) around the vertical geometric axis (a-a) necessary for the   reading of the whole phonogram of the disc.