GB2229848A - Tone arm - Google Patents

Abstract

A tone arm system has means to prevent possible vibration by adjustment of balancing members by the user to shift the centre-of-mass of the arm tube (12) to its rotational centre (1 9). The tone arm system is also provided with a tracking-force-generating system which uses force other than gravity, in particular a magnetic force. A ring-shaped means is provided in the tone arm system to work in conjunction with the balancing device to make sure that the line connecting the stylus tip and the point at which the vertical rotational axis and the horizontal axis of the tone arm meet is perpendicular to these two axes. In addition to the main body of the tone arm system, a balancing device is provided to help the user balance the headshell and the cartridge. <IMAGE>

Description

SPECIFICATION TONEARM The invention relates to a tonearm and particular to the tonearm of which the center of mass coincides its center of rotation, and of which the line connecting the stylus mounted to it and the center-of-mass may be easily adjusted to become perpendicular to its vertical and horizontal rotation axes.

Conventionally, tonearms are provided with a counterbalance weight. The tonearm, consisting of a tube and such a balance weight, acts in some way exactly 15 lie a weighing machine. The cartridge mounted on the fore end of the tonearm has a stylus which, by picking up the signals in the record grooves, generates musical currents. To ensure steady contact of the stylus with the grooves, a certain tracking force is needed.Therefore, the counter-20 weight mounted at the tail of a tonearm is used to change the balance status of a tone and provide a proper taci force to the stylus. Modifying the position of the esunter- weight on a balanced arm use is hence a widely-used way to reach the goal.

Since tonearms are always designed to rotate freely in both the vertical and the horizontal directions about the rotational center, their tuba: part. when viewed Pro the angle of rotation, is actually very similar to a to flywheel whose rotation is limited by its spingle bearing.

Whenever the stylus traveling in the grooves picks up signals, the tonearm, to which the stylus is mechanically connected, will inavoidably vibrate. While this movement is considered by almost all the tonearm designers a kind of vibration, it is actually small movements containing rotation in both the vertical and the horizontal directions. To be more specific, a tonearm could be considered as a tube receiving continuous forces applied to it from the groove the stylus is traveling in.Were the tonearm not limited by its bearings, whenever a force is applied to it at a point other than its center-of-mass, said tonearm would definitly swing (According to the physical law, this swinging is actually a part of rotation) about its center-of-mass- more specifically, about the ax s passing its center-of-mass and perpenticular to the line connecting its center-of-mass and the point the force, applies to.

During play of a record, the performance of the tonearm may be likened to that of a flywheel ratating about its spindle. The maJor difference between the tonearm 5 rotation and that of a flywheel is that the latter being 360 degrees around and the former being considerably smaller. However defferent their rotational ranges may be vibrations happening to them can be explained by the same mechanical principals and eliminated in the same way. The reason why an unbalanced flywheel causes vibration on its bearing while rotating will explain why a tonearm using gravity to generate the tracking force for its cartridge will cause vibration against its supporting bearings while In operation. Anyhlng that rotates freely will rotate about its center-of-mass.

When the center-of-mass of a flywheel stays out of its center of rotation, which is the center axis of its spindle, said flywheel will have a tendency to draw its center-of-rotation as near to its center-of-mass as possible. Thus, an unbalanced flywheel causes hits against its bearing while rotating, and brings about vibration. However small the rotation may be, such vibration can never disappear.As perfect balanced condition and perfect perpendicularity between the spindle and the flat surface of the "flywheel" are the only factors that make'a flywheel rotate in the smooth way without causing the unwanted vibration, these two conditions will be the only keys to having a tonearm, if likened to a flywheel, reproduce the information in the groove in the natural and clean way as all the vibrations caused by unbalancedness are all eliminated.

According to the present invention, the tonearm designed to swing in the natural and clean way comprises a tube, a counter-weight, a vertical balance-adjusting threaded member and a lateral balance-adiusting assembly, a threaded member and an elastic means designed for changing the position of the arm-tube in regard with the pIvot, a support system, a magnetic tracking-force-generating device. a means which helps ensure the perpendicularity between the axis of the horizontal rotation and the line connecting the stylus and the point the vertical rotation axis and the horizontal rotation axis meet.

There are three factors that make the tonearm do horizontal ratary motions: a, The spiral record grooves on the record will make the tonearm move rotaryily from the outside of the record to its inside; b. when the spindle hole of a record is off-centered, all the grooves on such a record will be eccentric in regard with said spindle hole, thus making the tonearm whose stylus traveling in said grooves move rotarily left-and-right; c. the information in the grooves make the stylus and the tonearm move rotarily in a very small degree.

There are also 2 factors making the tonearm do vertical ratary motions: a. Unflat record surface will cause said tonearm to have such a motion; b. the information in the record groove will make the vertical rotary motion in a very small degree.

Accordingly an object of the invention is to make a tonearm system to which said means are provided to adjust the balance of said tonearm so that the center-of-mass of the 20 tube of the tonearm system and all the components fixedly connected to said tube may coincide with the point at which the axis of the vertical rotation and that of the horizontal rotation of said tonearm tube intersect. Another object of this invention is to provide a 25 tracking-force mechanism which, instead of using gravity to generate the trackingforce needed by the stylus to travel stably in the grooves and to pick up signals from them as all the conventional tonearms do, uses other means (widely known as dynamic tracking-force) such as the magnetic force to generate said tracking-force.

Another object of this invention is to provide a detachable cartridge shell having a lateral balance-adjusting means and to provide a balancing device hereinafter called the headshell assembly balancing device on which the said shell-and-caridge (hereinafter called headshell assembly) fixed to it could be balanced.

Another object of this invention is to provide a means by means of which the perpendicularity between the axis of the vertical arm-tube support and the line connecting the stylus tip and the point where the horizontal and the vertical rotational axes intersect may be perfectly achieved by the users.

The tonearm of the present invention comprises an armtube and a shell attached to said tube at its front end.

The center-line of the tube is at an angle with that of the headshell. Said tube is connected to 2 bearings, each lying in a horizontal plane, by means of a pivot. Said pivot is connected to the said tube by means of an curved elastic piece and a threaded member that by turning the said threaded member, the position of the said pivot, which is sandwiched by the elastic piece and the threaded member, may be changed in regard with the tube. Said bearings allow the tube to do vertical rotary motion. The tube support is connected to the base of the tonearm by means of two bearings which allow the tube support and the tube to do horizontal rotary motions.

At the tail of the armtube is provided a counterweight and a vertical threaded member. Longitudinal shIfting of said counterweight along the said tube and vertical shifting of the means attached to the said threaded member when the balanced headshell assembly is attached to the tube may adjust the center-of-mass of the said arm-tube to its rotational center.

A magnet is mounted on a rack connected to an erect port and 2 magnets are connected to the arm-tube. The orientation and the adjustable relative position of the said magnets make it easy for the user to creat the tracking force needed and to adjust it to a proper degree.

A balancing device that is very similar to a balance in terms of structure and function may be used to balance the headshell assembly so as to make the center-of-mass of said assembly fall in line with the longitudinal center line of the arm tube.

A checking device is provided to the tonearm system for its user to adjust the position of the said tube support so that perfect perpendicularity between the rotational axis of the tube support and the line connecting the stylus and the rotational center of the tonearm assembly may be reached.

Further objects and advantages of the invention will be apparent from a reading of the following detailed description, taken in conjunction with the figures of the accompanying drawings, in which: FI#. 1 is a side view of a tonearm of the invention; FIG. 1A is an enlarged view of the hight-adjusting assembly on the pivot which helps ensure the perpendicularity between the tonearm of the invention; FIG. -9 is a enlarged cross-sectional view on the line 2-2 of Fig. 1; FIG. 3 is a top view of the tone arm of the present invention with part of it cross-sectional; FIG. 4 is a top view of the headshell assembly balancing device of the present invention; FIG. 5 is an end view of said headshell assembly balancing device;; FIG. 6 are top view of the balancing device with a headshell assembly mounted on; FIG. 7 is an enlarged cross-sectional view of said head-shell assembly balancing device viewed from the line 7-7 of FIG. 6; Fig. 8 is a view similar to Fig. 7, showing the headshell assembly mounted on it being reversed; and Figs. 9 and 10 are the views showing the said headshell-balancing device of FIG. 7 and 8 in a unbalanced status.

The preferred example of the present invention shown in the accompanying drawings is a tonearm obtaining the tracking-force by means of a force other than gravity. The said tonearm 10 comprises a tube 12 and a detachable headshell 14; one pivot 16 goes horizontally through the tube 12 and is engaged to the support 20 through 2 ball bearings 18. Said arm-tube 12 fixedly connected to said pivot 16 by means of a screw 9 and an elastic piece 92 may rotate upand-down about the center-line 17 of the pivot 16. The tube support 20 is also connected to the base 24 by means of 2 Dall-bearings 22 which allow the said tube 12 to rotate right-and-left about the center line 21 of the tube support 20.The 5 ball bearings 18 must be positioned in such a way that the center line 17 of the pivot 16, namely the central axis of the arm-tube's vertical rotation, intersects that 21 of the tube support 20, which is also the center line of the arm tube's horizontal rotation, at one point 19.

A plurality of balance-adjusting devices are employed in the present invention for the user to adjust the centerof-mass of the arm-tube 12 to the said point 19. One dynamic tracking-force-generating device (particularly the magnetic one) is employed to, without changing the position of the said 15 center-of-mass, create a proper pressure for the stylus, said pressure generally ranging from 1 to 1.5 gums.

Said tube 12 may be of any type, such as straight-type, J-type or s-type so long as 2 conditions are satisfied: 1st, the line connecting the stylus tip 31 and point 19 be perpendicular to the pivot 16; 2nd, a plurality of balanceadjusting device be provided to the tonearm to ensure that the center-of-mass of it's tube be adjusted to the point IS.

As for the preferred embodiment, a straight-line shape is employed and a headshell assembly is mounted to the said tube 12. The cartridge 28 has a stylus 30 that picks up signals in the grooves.

The pivot bearings 18, the tube support 20 and the base 24 all together form a supporting system that supports the tube 12 and allows it to rotate in both horizontal and vertical directions. The said tube support 90 is connected to the said base 24 by means of a screw 23. After loosening said screw 23, one could easily change the position of the tube support 20 in respect of the base by raising or lowering it manually.

The dynamic tracking-force-generating device, in particular that using magnetic force to generate the tracking-force; may provide the stylus 30 with an appropriate tracking force. Such magnetic tracking-force mechanism includes a cone-shaped magnet 32 which is mechanically fixed to the base via a rectangular rack 42 and a supporting port 44, and one or two magnets 34 and 36, each fixedly connected to the tube 12 by means of a supporting means 38 and 40 and moving along with the tube 12. The poles of said magnets are arranged in a way that the magnets 32 and 34 repel each other, and the magnets 32 and 36 attract each other.

The magnets 34 and 36 are mechanically and rigidly fixed to the tube 12 via the supporting means 38 and 40, and will rotate about the axis 17 along with the tube. However, the cone-shaped magnet 32 is, as shown in Fig. ~. fixed to a rectangular rack 42 by means of a fixing means 35 such as threaded member , and may be removed if necessary Said magnet 32 is positioned in a way that its center line 33 falls in line with the center line 21 of the tube support 20.

By loosening the screws 46, the vertical height of the supporting rack 42 may be adjusted manually by the user.

Said screws 46 fix the magnet rack 42 to a supporting port 44, which is locked to the base. Thus, as the center-line 33 of the fixed cone-shaped magnet 32 always stays in line with that 21 of the tube support, the relative distance between the magnets 32 and 34 and that between the magnets 32 and 36 will always be maintained the same during the play as long as the record is flat.

And, the magnets 34 and 36 of a tone-arm system so designed will always be concentric with the circumference of the said magnet 32 as the tonearm/stylus goes from the outer rim to the inside of the record during play.

However, in case of an unflat record and the stylus must go up-and-down, the magnet 34 will move toward the magnet 32 when the magnet 36 turns away from same, and vice versa. Thus, while the repellence existing between the magnets32 and 34 increases, the attraction between the magnets 32 and 36 will decrease. Being made up by the sum of these two forces, the tracking-force will remain the same as one force increases when the other decreases.

By slightly loosening the screws 46 and sliding the magnet rack 42 up and down along the slots 48 on the supporting port 44, the vertical position of the cone-shaped magnet 32 may be raised or lowered so that the distances between the magnets 32 and 34 and that between the magnets 32 and 36 may be simultaneously adjusted until an appropriate tracking-force is obtained.

To prevent loss of the magnetic density of the said 3 magnets, it is preferable that the magnet rack 42, the supporting port 44, and the supporting means 38 and 40 be made of materials other than those that are magnetically conductive.

All other dynamic tracking-force-generating mechanism such as the spiral spring, may be employed in the present invention in conjunction with or in place of the said magnetic tracking-force mechanism.

A number of balancing devices are provided to the tube and the headshell assembly (hereinafter called the arm-tube assembly) to help the user shift its "center-of-mass in the X (lateral), Y(longitudinal), and Z(vertical) directions.

The "center-of-mass" mentioned above is that of the tube 12 and all the components fixedly connected to it. such components including the shell 14, the cartridge 28, stylus 50. the horizontal pivot 16, the supporting means 38 and 40, the magnets 34 and 36, and all the balancing means. All the other components. such as the tube support 20, bearings 13 and tz, cone-shaped magnet 32, magnet rack 42, supporting port 44, adjusting screws 46 and base 24 are all supported by the chassis of the turntable, therefore being irrelevant to the center-of-mass of the arm-tube assembly.

In addition to the said balancing devices, a screw 90 and an elastic piece 92 are provided at the top of the pivot 16, that by turning the screw upward or downward, the position of the tube 12 in respect of the pivot 16 may be changed, thus getting the center-of-mass of the tube closer to the center line 17 of the pivot 16.

A shell 14 mounted on the said straight tube that is used in the preferred embodiment must be at a complementary angle with the center line 13 of the tube 12 to ensure that the stylus 30 stays tangent with the record grooves. As this lea of arrangement makes the center-of-mass of the head shell assembly off from the longitudinal central axis of the tube, it is required that the center-of-mass of the said headshell assembly be adjusted to stay right at the said axis. For this a lateral balancing means 50 is provided to the shell 14. Said device 50 including a threaded member 52 fixed to the shell 14 and parallel to the pivot 16, and 2 nuts 54 and 56 which may be tightened each other on the said threaded member 52.Shifting the 2 nuts 54 and 56 along the said threaded member 52 may change the position of the center-of-mass of the shell assembly to a position vertically under or above or at the longitudinal central axis 13 of the arm-tub 12. By operating the balancing device 60 shown in Figs. 4 and 5 designed for the balancing operation of the headshell assembly, one could easily adjust the headshell assembly s center-of-mass to the demanded position. The said balancing device 60 is structually and functionally very similar to a balance. Supported by two tip-toes 62 at the two ends, this balancing device 60 will not stay level unless its center-of-mass falls vertically under the line 73 connencting the two points 63 contacting the two tip-toes 62.

If not perfectly balanced, the balancing device 60 will unavoidable incline to either side. Above the center line 73 of the adjusting device 60 a socket 64 is attached. This socket 64, similar to the head-shell socket 26 mounted on the arm-tube 12, is provided to the said balancing device 60 for the shell and the chosen cartridge to be engaged to. The balancing device 60 has at its bottom a lateral slot 66.

Within said slot 66 a movable screw 68 is provided. By sliding the screw 68 within the slot 66 one could adjust the said balancing device 60 to a level condition. The spirit level 70 mounted at the other side of this balancing device is provided to detect the levelness of said balancing device 60.

The socket 64 on the balancing device 60 is designed in a way that the headshell-assembly can be mounted to it with the stylus 30 facing either downward or upward as shown in FIGs. 7 and 8. In either way, the surface of the shell 14 will be level with the bottom 76 of the balancing device 60.

Theoretically, when the heådshell-assembly is mounted to the balancing device 60 in the way as shown in Fig. 6, and said device 60 is fully balanced before the said headshell-assembly is mounted, unless the center-of-mass of said headshell assembly falls vertically under the center line 73, turning the headshell assembly upside down from the status shown in Fig 7 to that shown in Fig. 8 will change the status of balance of the total assembly including the balancing device 60 and the headshell assembly mounted on it.

Provided that the right side of the headshell assembly and the balancing device 60 falls down as shown in Fig. 9 when the headshell assembly is reversed, one could be certain that the center-of-mass of the headshell assembly is off the plane vertically intersects the centerline 73. What the user should do is 1st turn the nuts 54 and 56 away from the shell to as far as they can go on the threaded member 52, then shift the nuts a little bit closer to the center line 73 at one time so that the total assembly becomes less inclined, then reverse the headshell assembly from the status shown in Fig. 9 back to that of FIG. 10, then slightly shift the nuts 54 and 56 inward and repeat the above processes until the said balancing device 60 remains level with the stylus 30 of the headshell assembly mounted on it facing either upward or downward.When this status is reached, it is apparent that the center-of-mass of the headshell assembly falls at (to be accurate, under or above) the center-line 73, and will fall either above or under the longitudinal center-line of the arm-tube when mounted to the said arm-tube 12.

The said balancing device 60 also has a slot 74 at its bottom side 76. This slot 74 is designed to be at an angle with the center line 73 of the balancing device 60, so that looking from under the bottom of the said device 60 into the said slot, the user could clearly see the stylus 30 of the chosen cartridge 28 and check if the said stylus is aligned with the said slot 74, and if the tip 31 of the stylus 30 exactly falls under the point 77 the center line 73 and the slot 74 meet. Meeting these two conditions means that the stylus 30 stays tangent with the record goove and the line connecting said stylus tip 31 and the point 19 becomes perpendicular to the axis 17 of the pivot 16.

Sliding the counter weight 80 (shown in Fig. 1 along the tube 12, one could easily adjust the center-of-mass or the tube 12 in the longitudinal direction; and in like manner, adjust the center-of-mass of the arm-tube assembly in the vertical direction by raising or lowering the position of the nuts 86 and 88 along the threaded member 84. To do the longitudinal balancing, one, after the magnets 32, 34, and 36 are well-deposed and the magnet 32 is temporarily taken off, slowly slides the counterweight 80 to an appropriate position until the arm-tube 12 with the cartridge fitted assumes a level position. The center-of-mass of the arm tube assembly will now rest below the center-of-rotation 19 of the armtube.When the longitudinal balance is reached, one slowly turns the screw 90 to change the position of the tube 12 in regard with the pivot 16 or moves the nuts 86 and 88 upward from the very bottom of the threaded member 84 bit by bit until the headshell assembly either goes up or falls down.

At this moment, one can be sure that the center-of-mass of the whole arm-tube assembly is coincendent with the center of rotation, namely the point 19. Mount the magnet 32 back to the rack 42 and adjust its height in the way mentioned above until an appropriate tracking-force is obtained.

As shown in Figs. 2 and 3, a U-shaped means 100 is locked to the outer cercumference of the tube-support 20 with its upper edge contacting the protruding lower edge 103 of the 2 bearings 18. The said means 100 has at its upper surface two lugs 104. Each of the said lugs has a top surface 106 which is at the same level with the center line 17 of the pivot 16. Geometrically, the two top surfaces 106 of the said lugs 104 and the said center line 17 of the pivot 16 constitute a plane that is perpendicular to the central axis 21 of the tube support 20, namely the axis of the horizontal rotation of the said tonearm. By looking from the rear of the tube 12 and adjusting the height of the tube support 20, one could easily make the stylus tip 31 and the top surfaces 106 of the two lugs 104 fall in said plane, thus obtaining the perpendicularity between the line 108 connecting the stylus tip 31 and the point 19 and the said axis 21 of the tube support 20.

Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is desclosed and is intended to be limited only by the scope of the appended claims.

Claims (11)

CLAIMS:

1. A tonearm system for picking up signals and for preventing vibrations caused by its unbalancedness comprising: (a) a tube (12) supported by a plurality of supporting means which allow the said tube to rotate horizontally and vertically about a rotational center (19); (b) a plurality of balancing means, by adjusting which the users could easily shift the center-of-mass of said tone-arm tube (12) to its rotational center (19); (c) a tracking-force-generating system that uses forces other than those generated by gravity, in particular that generated bay magnetic force, to create an appropriate tracking-force required during the play of the record without affecting the status of balance of said tone-arm system; and (d) a plurality of adjusting means by means of which one could easily adjust the said tonearm to a state that the line connecting the tip (31) of the stylus (30, mounted to said tonearm and the rotational center (19: becomes perpenticular to the axis (21) of the horizontal rotation and that < 17j of the vertical rotation of the said tone-arm system.

2. A tonearm system according to Claim 1 wherein said supporting means comprises a base (24); a rotatable tube support (20) assembly connected to the said base (24, by means of a plurality of bearings (; and a horizontal pivot fl connected to the said tube support (20) by means or a -plurality of bearings (18), said horizontal pivot (16) going through the said tube (12) and allowing same to rotate vertically.

3. A tonearm according to Claim 1 wherein the said balancing means includes one that shifts the center-of-mass of said tube longitudinally and one that shifts said center of-mass vertically and one that shifts the said center-ofmass laterally in a horizontal plane and one that changes the position of the said arm-tube (12) in regard with the said pivot (16).

4 A tonearm according to Claim I wherein the said tracking-force-generating system comprises a magnet of which the center line C33) falls vertically in line with the said 5 rotational center (19), and two magnets (34, 36) machanically affixed to the said tube (12), one of same creating a repellance against the magnet (32), and the other creating an attraction toward the magnet (32).

5. A tonearm according to Claim 4 wherein the said magnet 10 is fixed to a rack (42) whose vertical position may be easily and manually adjusted.

6. A tonearm system according to Claim 2 wherein said tube support (20,# comprises a hight-ad.ustin device by means of which the dIstance between the said pivot and the base (24) may be easily adjusted.

7. A tonearm system according to Claim 2, wherein said tube support (20) is provided with a U-shaped means (100) having two protrusive lugs (104). the line connecting their upper ends (106) falling in line with the stylus tip (31) when the line (108) connecting said stylus tip (31) and the rotational center (19) of the said tube becomes perpendicular to the said rotational axis (21) of the said tube support (20).

8. A tonearm system according to Claim 1 further comprises one detachable headshell (14) to which a cartridge (28) may be mounted to pick up signals from the record grooves during play.

9. A tonearm system according to Claim 8 wherein said headshell has a balancing means (50) protruding laterally and being parellel to the pivot (16), said balancing means comprising a threaded member (52) and a number of nut such that by shifting the position of the said nut(s) the centerof-mass of the said headshell-assembly could be shifted.

10. A tonearm system according to Claim 1 further comprises a balancing means, said means comprising: one U-shaped base having one concaved point (63) at the center of the bottom surface of each of its shoulders; two tip-toes (62) for suspending the said base of which the said concaved points l6::3) lie at the top of said tip-toes (62), one center line (73) drawn around the surface of the said U-shaped base, connecting the said two conclaved points ~63); a socket (64) similar to that (26) on the arm-tube '12), capable of receiving the headshell assembly uith the stylus (30) either facing upward or downward; a level (70) by which one can check If the U shaped base is in the level status; a slot (66) going laterally at the bottom (76) of the U-shaped base; a threaded member and a nut (68) which may be moved within the slot ~66) and fixed thereto to adjust the center-of-mass of the said U-shaped base; and a miter slot (74) at the bottom (76) of the Ushaped base intersecting the said center line of the U-shaped base at one point (77) which, together with the said slot (74) itself, helps the user to define the correct position of the stylus (30).

11. A tonearm system substantially as hereinbefore described with reference to and as snown in the accompanying drawings.