Tangential tracking tonearm

A tonearm system is provided in accordance with the invention in which the tonearm is mechanically maintained in tangential tracking relationship in the groove in a record during the playing thereof, the record being mounted on a rotating turntable. The principle of the mechanical system according to the invention is to provide the tonearm in fixed relationship with a bracket combination capable of pivoting the tonearm horizontally on a vertical axis which bracket in turn is adapted to rotate about a secondary vertical pivotal axis, this axis being in fixed relationship to the axis of the turntable and the record being played.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to a record player and, in particular to a tonearm 
system for use with a record player providing tangential tracking of the 
stylus in the groove of the record being played. 
(2) Description of the Prior Art 
In record players which contain a rotatable turntable for supporting 
grooved disc records for playing, either of the mono or stereo variety, 
there is typically provided a tonearm mounted for horizontal swinging 
movement about a fixed vertical pivot axis, which vertical pivot axis is 
offset from and is located outside and adjacent to the peripheral rim of 
the turntable. The stylus of such a tonearm system typically describes an 
arc as it tracks the record groove, swinging in a generally clockwise 
direction as the record is played (assuming an outside-in recording). 
It is most desirable that tangency be maintained between the tonearm/stylus 
and the record groove during play, as a lack of tangency gives rise to 
tracking distortions, and undesirable stylus/groove side pressures 
generated on the inner side of the stylus because of the frictional force 
(called "skating force") between the stylus and the walls of the groove of 
the record. 
Any lack of tangency of the stylus with the record groove is undesirable in 
playing monaural records, but is especially undesirable when playing 
stereo records containing separate audio channels on opposite sides of the 
record groove. The reason for this is that not only are distortions 
introduced, but audio balance is disturbed due to the unbalanced side 
pressures. 
Over the years various means have been provided to achieve tangency between 
the grooves of a record being played and the central line or axis of the 
tonearm or pickup and stylus. One means to accomplish this tangential 
relationship has been to offset the tonearm in which the pickup is 
supported by a bent arm and to so mount the pickup that it describes an 
arc across the record. While this maintains relatively good tangency to 
the groove area over the range of radii covered in modern recordings, it 
suffers from the disadvantage, (1) that tangency is really only an 
approximation, and (2) that undesirable side pressures are produced on the 
stylus so that while the pickup body may be tangential, the stylus itself 
is pushed out of tangency and the unbalanced forces on the stylus and its 
supporting mechanism create displacement and distortions which are quite 
serious. 
Another means to accomplish this desired tangential relationship between 
the stylus and the record groove has been to provide the cartridge itself 
at an angle to the tonearm. Tonearm systems incorporating such a system 
are sometimes provided not only with means to adjust the tracking angle, 
but also means to counter the "skating force", i.e. the inward force 
during record play which applies lateral forces against the inner groove 
wall of a record, otherwise desirable minimum record wear and optimum 
tracking is not achieved. 
Straight line motion of the tonearm, or pickup, other than a swinging arc, 
which tends to assure tangency has been an alternative approach by some in 
the prior art and various tonearm systems of this type have been provided. 
An example of such a system is shown in U.S. Pat. No. 2,915,315 wherein 
there is disclosed a support for a conventional phonographic pickup which 
is mounted on a moveable carriage and which is driven by an external motor 
which causes the carriage to maintain the pickup in essentially straight 
line motion at the stylus tip. 
A desire in more recent times is also to make the stylus mass even smaller. 
Thus, in U.S. Pat. No. 3,356,372 there is disclosed not only a means for 
moving a stylus in a radial line as a grooved, disc record is being 
played, but one which is a very small lightweight phonograph pickup having 
a low friction. 
Although some of the prior art systems provide for tangential tracking of a 
tonearm system in record players and have had some success, these tonearm 
systems more often have been not only unduly mechanically/electrically 
complex, but quite expensive. Moreover, they often do not satisfy wholly 
the requirements of a tangential tracking system, particularly where use 
of a very low mass tonearm is also desired. 
SUMMARY OF THE INVENTION 
There is provided by my invention a record player comprising a simple, 
relatively inexpensive, tonearm system for use in combination with a 
turntable adapted to play a grooved disc record wherein the tonearm system 
provides tangential tracking of the stylus of the tonearm thereby reducing 
distortion and skating forces experienced by the stylus, and, moreover, 
comprises the employment of a low mass tone arm. 
In conventional tonearm systems for record players, there typically is 
employed a tonearm supported by a horizontal pivot bracket and a vertical 
pivot bracket. The horizontal pivot bracket is supported by a bearing 
which lies in a horizontal plane, but which axis allows the tonearm to 
move vertically in respect to the turntable. Thus, the tonearm is provided 
to always rest horizontally on the uppermost record. The vertical pivot 
bracket is supported by a bearing lying in the vertical plane, and the 
vertical pivot bracket allows the tonearm to pivot horizontally in respect 
to the turntable. Typically, the horizontal and vertical pivot brackets 
coincide and the vertical axis of the vertical pivot bracket is kept fixed 
relative to the turntable axis. 
I have now discovered that the employment of a moveable vertical axis for 
the tonearm, in combination with a guide means associated with the 
turntable and tonearm provides for a simple, inexpensive, tangentially 
tracking tonearm system. The employment of two vertical pivot axes for the 
horizontal pivotal movement of the tonearm is preferred, one vertical axis 
being fixed, and the other being moveable. The moveable vertical axis is 
disposed with respect to and intersects the horizontal axis of the tonearm 
system. 
In the tonearm system of my invention, the tonearm pivoted for horizontal 
movement of the tonearm on two vertical axes and for vertical movement on 
a horizontal axis, is combined with a guide means which is located 
adjacent to the edge of the circular shaped turntable. Desirably, the 
guide means is circular shaped and is located concentric to the turntable. 
The guide means of the invention has an outside edge located at a radial 
distance from the axis of the turntable such that the distance equals the 
tonearm effective length. The tonearm effective length is defined as the 
distance between the moveable vertical axis of the tonearm and the stylus 
tip of the stylus at the end of the tone arm, as measured on a horizontal 
plane parallel to the surface of the rotatable turntable. A guide-lever 
means, having a straight edge that passes through the moveable vertical 
axis of the tonearm, is mounted at 90 degrees to the axis of the tonearm. 
In accordance with the invention, the tonearm with the stylus tip is 
allowed to move in a vertical plane employing the horizontal pivot axis 
associated with the moveable vertical pivot axis, the horizontal pivot 
axis being located at a right angle to the tonearm. In the tonearm system 
of the invention, unlike conventional tonearm systems where the vertical 
pivot axis of the tonearm is kept fixed relative to the turntable axis, 
the moveable vertical pivot axis is mounted for horizontal pivotal 
movement around a rotatable member, which rotates about a fixed vertical 
pivot axis. 
In the operation of my tangential tracking tonearm system, the tangential 
force on the stylus tip of the tonearm by the record groove, during 
rotation of the record on the surface of the turntable while the record is 
playing, causes both the tonearm to pivot about its moveable vertical axis 
and the rotatable member to pivot on its fixed vertical axis until the 
guide-lever means is in contact with the guide means. The guide-lever 
means remains, during playing of the record, in constant contact with the 
outside edge of the guide means. As the guide means, in the case of a 
circular shaped guide, is concentric with the axis of the turntable and 
the record being played, the guide-lever means is always tangential when 
it contacts the guide means. As the angle the guide-lever means makes with 
the tonearm is also 90 degrees, this provides that the tonearm and stylus 
axis is always tangential to the record groove, irrespective of its 
position on the record. Thus, in my system, tangential tracking of the 
tonearm and stylus is accomplished by a simple and economical means. 
A further advantage with my invention, since any tangential force applied 
with a record to the stylus tip is balanced out as the guide-lever means 
contacts the guide means, and tangential tracking is provided, is that no 
skating force is experienced by the stylus tip. Furthermore, since there 
is no tracking error, because of the tangential tracking provided by my 
invention, the tonearm length can be made quite short, limited, of course, 
only by the particular turntable radius plus any clearance required 
between the turntable and guide means. This is particularly advantageous 
as it permits the design and operation of an extremely low-mass tonearm. 
Thus, in summary, the tone arm system of the invention provides not only 
tangential tracking but substantially 0-skating force, and the use of a 
relatively short, low-mass tone arm in a phonograph and record player. 
My invention thus comprises a record player comprising a turntable and a 
tangential tracking tonearm system which comprises in combination: a 
turntable mounted for rotation about a central axis and adapted to receive 
a groove type disc record, either mono or stereo, on the surface of the 
turntable to be played, the turntable having a peripheral outer edge 
thereof; a tone arm defining an axis and containing a stylus at one end 
thereof comprising a stylus tip for tracking the groove of the record on 
the turntable for playing the record; a guide means disposed adjacent to 
and spaced just apart from the outer peripheral edge of the turntable, the 
outer edge of the guide means being at a radial distance equal to the 
effective length of the tonearm employed; a moveable pivot bracket 
defining a vertical axis for the tonearm adjacent to the other end thereof 
to permit the tonearm to have pivotal horizontal movement about said 
vertical pivot axis; a horizontal pivot bearing and support for the 
tonearm intersecting with the moveable vertical pivot axis; a horizontal 
pivot bearing and support to permit the tonearm to have vertical pivotal 
movement about the horizontal axis; for example, a horizontal pivot 
bracket and a vertical pivot bracket cooperatively joined at the one end 
of the tonearm; a secondary vertical pivot bearing and support defining a 
fixed vertical pivot axis and means connecting the fixed vertical pivot 
axis with the moveable pivot axis; and a guide-lever means secured to the 
vertical bearing and support means and extending through the moveable 
vertical pivot axis and at an angle of 90 degrees to the tonearm axis and 
extending toward the guide means and overlapping the outer edge thereof 
whereby, on operation of the record player and the rotation of the 
turntable and the playing of the record, the tone arm and stylus is 
maintained in tangential relation to the record groove at all times 
through the continuous contact of the guide-lever means against the 
outside edge of the guide means, while the vertical bearing and support 
means pivots the tonearm to maintain the stylus tip of the tonearm at a 
tangent to the record groove.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS THEREOF 
Referring to the drawing there is shown in FIG. 1 thereof a record player 
10 comprising a rotatable turntable 12 mounted for rotation about a 
central axis 14 comprising a manual spindle for single play operation. 
However, it will be appreciated that an automatic spindle for support of 
several records for play automatically can be provided instead, or in 
addition to, if desired. Turntable 12 is supported on base plate 16, which 
in turn can be mounted by conventional elastomeric suspension means to a 
fixed base (not shown). 
On the turntable platter, which can be a solid, one piece precision coating 
having a computer optimized mass, is shown a grooved disc record 18 for 
play. The circular shaped turntable 12 is of a predetermined radius and 
has an outer peripheral edge 20. The turntable is adapted to be rotated 
about central axis 14 by a driving means, such as through a direct-drive 
or belt-driven motor (not shown). 
Tonearm system 22, in accordance with invention, is positioned adjacent the 
peripheral edge 20 of the turntable 12, and comprises the tonearm 24 
having a tonearm axis and which consists essentially of a balanced tubular 
rod. At the one end of tonearm 24 is provided stylus 26, with a stylus tip 
28, the stylus tip adapted to be placed in the groove of the record 18 for 
playing the record 18, as is conventional. At the other end of the tonearm 
24, there is provided a moveable counterweight 30, which provides dynamic 
zero balance of the tonearm 24. It will be appreciated by reference to 
FIG. 2 of the drawing that the axis of stylus 26 and stylus tip 28 is in 
the same vertical plane as the axis of tonearm 24. 
Tonearm 24 is fixedly secured to a horizontal pivot bracket 32 at the end 
adjacent counterweight 30 with the horizontal pivot bracket bearing 34 
being in a horizontal plane. This permits tonearm 24 to move in a vertical 
plane in respect to the turntable 12. Disposed within the horizontal pivot 
bracket 32, which bracket has the configuration of an inverted U, is a 
tonearm vertical pivot bracket 36, the bearing for which lies in a 
vertical plane. This allows tonearm 24 to pivot horizontally in a 
horizontal plane in respect to the turntable 12. The tonearm vertical 
pivot bracket 36 defines a moveable, primary, vertical pivot axis 38. 
As shown in the drawing, horizontal pivot bracket 32 and vertical pivot 
bracket 36 are in combination with one another, and in such combination 
provide for vertical and horizontal pivotal movement, respectively of 
tonearm 24. Although the combination which provides these functions can be 
of various structural configurations, the important consideration is that 
the vertical and horizontal pivot axes intersect. The horizontal pivot 
bracket 32 and the vertical pivot bracket 36 are disposed for movement on 
pivot pins which define the respective axes for pivotal movement of the 
brackets, and hence the tonearm 24. These pivot pins can be spring loaded 
pivot pins, if desired, which permit adjustment and control of the 
frictional forces about the respective vertical and horizontal axes. 
A guide 40 is located adjacent to the peripheral edge 20 of the turntable 
12 and is associated therewith and with tonearm 24, near the tonearm 
vertical pivot axis. The preferred guide is an arc of a circular shaped 
rim having predetermined inner and outer radii greater than the radius of 
the turntable 12, and is positioned so as to be concentric to the 
turntable 12, adjacent to, but beyond the peripheral edge 20. The guide 
means 40 is secured to the base plate 16 (not shown). The outside surface 
42 of guide 40 has a radius such that R=L (as shown in FIG. 2), where L is 
the effective length of the tonearm 24. The effective length of tonearm 24 
is defined as the distance between the tonearm vertical pivot axis 38, as 
defined by the vertical pivot bracket 36, and the stylus tip 28, as 
measured on a horizontal plane parallel to the record playing support 
surface of turntable 12. 
An extended guide-lever means 44 is fixedly connected to the vertical pivot 
bracket 36 so as to move therewith. The inner straight edge 46 of 
guide-lever means 44 passes through the tonearm 24 vertical pivot axis. 
The guide-lever means 44 is mounted on vertical pivot bracket 36 so as to 
be at an angle of 90 degrees to the tonearm 24 axis, which is the same 
axis as the stylus-tip 28 axis, as illustrated. The straight edge 46 of 
guide-lever 44 extends over and just outside of the outer peripheral edge 
of the guide means 40, and is adapted to be placed in continuous contact 
with the outer edge of the guide means 40 during the operation of the 
turntable and the playing of the record, as hereinafter more fully 
described. 
The horizontal pivot bracket 32 and the vertical pivot bracket 36 are 
supported for horizontal pivotal movement about a secondary, fixed, 
vertical pivot axis by means of a rotatable member 48 secured for rotation 
about a pivot pin 50 secured to the base plate 16. Rotatable member 48 has 
opposed extending arm members 52, 54. The end of arm 52 is positioned 
within and supports the horizontal and vertical brackets 32 and 36. The 
other arm 54 is provided with moveable counterweight 56 by means of which 
dynamic zero balance can be provided of the rotatable member 48. Pivot pin 
50 can be spring loaded or adjustable so as to permit adjustment and 
control of the frictional forces about this secondary vertical axis. 
Control of the frictional forces about the vertical axis is desirable to 
insure a more positive contact of guide-lever means 44 with guide means 
40. The friction of the primary vertical pivot axis must always be greater 
than that of the secondary vertical pivot axis to guarantee that the 
straight edge 46 of the guide-lever means will always contact the outer 
surface 42 of the guide means. 
While the bearings for the pivotal movements can be of various types 
commercially available, it is much preferred that they be precision gimbal 
ball bearings. This will provide for minimal horizontal and vertical 
pivotal friction. 
The operation of the tangential tonearm tracking system 22 in accordance 
with the invention is shown more particularly in the plan view of FIG. 2, 
which illustrates the movement of the tonearm system in respect to the 
movement of the tonearm 24 as it moves from the outer periphery of the 
record 18 inwardly toward the central axis 14, with the tonearm 24 being 
maintained by my tangential tonearm system 22 in a tangential relationship 
to a record groove through a horizontal pivotal movement about fixed 
vertical pivot axis 50. Thus, in operation, when the stylus tip 28 
contacts the rotating record 18 in the record groove on the turntable 12, 
the record groove applies a tangential force on the stylus tip 28, which 
tends to rotate the tonearm 24, and the tonearm system 22 about the 
secondary vertical pivot axis by means of the rotatable member 48 rotating 
about pin 50. This pivotal movement continues until the guide-lever 44 is 
placed in tangential contact with the outside edge of guide 40. 
As the edge of guide-lever means 44 and the axis of tonearm 24 are at 90 
degrees with respect to one another, with contact of the outside edge of 
the guide-lever 44 passing through the tonearm vertical pivot axis, the 
stylus tip 28 will be maintained tangentially to the record groove during 
the playing operation, with the guide-lever 44 being in continuous 
moveable contact with the outside surface 42 of the circular shaped guide 
means 40 during the playing cycle. The guide-lever means 44 contacts 
against the outside of the guide means 40, moving from one to the other 
end thereof as the stylus tip 28 moves toward the central axis 14 during 
the playing operation, from the outside edge of the record 18 toward the 
central axis 14 of the turntable 12. Since the guide means 40 is circular 
with the center thereof concentric with the turntable 12, the guide-lever 
means 44 is always tangential when it contacts the edge of the guide 40, 
thus maintaining an angle of 90 degrees. 
In operation, as the stylus tip 28 moves from the outside edge of record 18 
during playing toward the central axis, as illustrated more particularly 
in FIG. 2, the horizontal pivot bracket 32 and the vertical bracket 36, 
and their respective axes, are moveable as the tonearm is maintained at 90 
degrees to the record groove through the action of the guide-lever 44 
against the guide 40. At the start of the playing cycle, the guide-lever 
44 contacts the guide 40 at the one end, and as the tonearm moves 
inwardly, the contact of the guide-lever 44 with the guide 40 is moved 
toward the other end, with respective movement of the moveable pivot 
bracket 36 and the respective tonearm vertical pivot axis as illustrated 
in the two positions shown in FIG. 2 of the drawing. 
In operation, the friction of the tonearm vertical pivot axis should be 
greater than the friction associated with the secondary vertical pivot 
axis and rotatable member 48, in order to maintain the guide-lever means 
44 in continuous tangential contact with the guide 40. Adjustment of any 
pivots with spring tension or the like means for the horizontal and 
vertical axes may be made to insure this continuous contact. 
As many different embodiments of this invention will now have occurred to 
those skilled in the art, it is to be understood that the specific 
embodiments of the invention as presented herein are intended by way of 
illustration only and are not limiting on the invention, but that the 
limitations thereon can be determined only from the appended claims.