GB2103861A

GB2103861A - Tone arm assembly

Info

Publication number: GB2103861A
Application number: GB08200852A
Authority: GB
Inventors: Robert Graham
Original assignee: MCINTOSH LAB
Current assignee: MCINTOSH LAB
Priority date: 1981-07-29
Filing date: 1982-01-12
Publication date: 1983-02-23
Also published as: JPS5819704A; KR830002136U; KR880000806Y1; GB2103861B

Abstract

A tone arm assembly (10) of the type employed in phonograph assemblies and the like, wherein the tone arm assembly (10) is supported on a unipivot bearing assembly (40 to 62) having a pivot point (62) coinciding with an imaginary horizontal line extending through a center of gravity of the tone arm assembly (10), with the horizontal line extending perpendicular to a longitudinal axis extending through the tone arm assembly (10) from a pick-up cartridge (not shown) positioned at one end to a counter- weight (136) positioned at an opposite end thereof. <IMAGE>

Description

SPECIFICATION Tone arm assembly The present invention generally relates to a tone arm assembly of the type employed with sound reproduction equipment, such as phonograph assemblies and the like. In particular, the present invention is directed to a uniquely balanced tone arm assembly capable of distortion free tracking across even highly warped record surfaces.

Conventional pivoting-type tone arm assemblies usually include an elongated arm member having an intermediate portion pivotally attached to a support housing mounted on a frame portion of the phonograph assembly. A pick-up cartridge and stylus assembly is attached to one end portion of the elongated arm, with a counterweight adjustably mounted on the opposite end portion. By pivotally attaching the arm to the housing assembly, it is possible for the stylus to move in both the vertical and horizontal directions as required when tracking over an undulating record surface. In order to achieve high fidelity sound reproduction, it is essential that the stylus be allowed to precisely follow each of the peaks and troughs formed in the record surface.If the stylus is deflected from its normal tracking path across the record surface, a degree of distortion is introduced, with the amount of distortion being directly dependent on the amount of deflection incurred by the stylus. The problem facing the prior art is to pivotally balance the tone arm above the record surface in such a manner that the stylus is allowed to move as freely as possible over the peaks and troughs of the record surface.

Early pivoting-type tone arm support assemblies usually employed independent bearing systems for controlling the vertical and lateral movements of the tone arm relative to the record surface. For example, ball races, knife edges and even simple sleeved members often made up one or both of the independent bearing systems. Such multiple bearing systems have proven less than completely satisfactory, in that it is practically impossible to isolate the bearing systems from affecting one another. As a result, the bearing assembly controlling lateral movement tended to inhibit free vertical movement of the tone arm, while the vertical bearing assembly tended to somewhat inhibit the lateral movement of the tone arm, resulting in an overall reduction in the fidelity of the sound reproduced from the record.Furthermore, because such independent bearing assemblies were generally complex in structure, it was difficult, if not impossible, to maintain the tone arm in a balanced condition over an extended period of time.

In an effort to overcome the type of problems associated with multiple support bearingassemblies, it has been suggested that the entire tone arm assembly be balanced on a single, unipivot bearing assembly capable of pivoting the tone arm in both the vertical and the lateral direction relative to the record surface. In order to balance the tone arm above the support housing, the prior art considered it essential that the pivot point of the unipivot bearing assembly be positioned vertically above the center of gravity of the tone arm to create a so-called beam-balance mounting assembly. Such an arrangement was considered to be stable in both the vertical and horizontal planes, in that any pivoting movement of the tone arm would generate a restoring force which tended to restore the tone arm to its initially balanced position.In effect, pivoting movement of the tone arm tended to displace the center of gravity of the tone arm assembly toward the raised end portion, thereby creating a restoring force which attempted to return the center of gravity to its initial position. The main drawback of such beam-balance mounting systems is that the restoring forces generated during the vertical pivoting movement of the tone arm opposed the vertical tracking movement of the stylus, thereby deflecting the stylus from its normal path. As a result of such deflections, the sound reproduced from the record was distorted with a corresponding reduction in the fidelity of the tone arm assembly.

The beam-balance achieved by positioning the pivot point vertically above the center of gravity of the tone arm did provide some sideways or lateral stability to the tone arm. In particular, lateral rolling movement of the tone arm generated restoring forces which tended to return the tone arm toward its proper position.

Typical of such a beam-balanced unipivot tone arm in the assembly suggested in U.S. Patent 3,23,283 issued January 25, 2966 to Stanton.

Stanton clearly suggested that the pivot point be positioned vertically above a plane passing through the center of gravity of the tone arm, the plane being defined as extending through the center of gravity of the counterweight and the head shell, respectively. Because a beam-balance effect is created in Stanton, longitudinal pivoting movement and/or lateral rolling movement of the tone arm must create restoring forces proportional to the degree of movement. These restoring forces attempt to return the tone arm to its initial position and thus adversely affect the desired tracking force acting on the stylus. As the tone arm in Stanton tracks over a warped record surface, the relatively large vertical pivoting movement of the tone arm creates a significant restoring force which opposes any movement of the tone arm away from its initial position.While Stanton provides desirable lateral balancing of its tone arm, the adverse restoring forces generated during vertical tracking movements of the tone arm render the Stanton assembly totally unsatisfactory.

Applicant has determined that if the pivot point of a unipivot bearing assembly can be carefully positioned to coincide with an imaginary horizontal line intersecting the center of gravity of the tone arm sub-assembly and extending perpendicular to an axis joining the head shell with a rear counterweight, vertical tracking movements of such a tone arm will not generate unwanted restoring forces. As the tone arm vertically pivots while tracking over a record surface, the only vertical force acting on the tone arm is the tracking force selectively chosen through placement of the rear counterweight.

In a further approach to the problem of providing proper balance, U.S. Patent 4,113,265 issued September 12, 1978 to lyeta suggests employing a pair of lateral counterweights for controlling sideways or lateral roll of the tone arm.

The counterweights are located forward of the pivot point in lyeta and tend to significantly increase the mass of the tone arm assembly.

Furthermore, because the inertia of the tone arm is equal to the mass times the square of the distance from the pivot point, the forward mounted counterweights suggested in lyeta tend to generate an excessive inertia level. Another drawback is the lateral counterweight induced rotation of the tone arm about its longitudinal axis as the lyeta tone arm tracks in a vertical direction on a warped record. This phenomenon produces uneven record and stylus wear as well as reduced channel separation between the left and right signals with a resulting decrease of stereo effect from the loud speakers.

In order to provide a tone arm with sufficient lateral stability and yet eliminate the types of problems confronting lyeta, applicant has determined that a pair of laterally arranged counterweights should have a center of gravity disposed vertically below the pivot point of the tone arm. Furthermore, to prevent the tone arm from rolling when tracking warped records, the axis joining the counterweights should extend perpendicular to the stylus cantilever. Because the center of gravity of the counterweights is slightly below the pivot point, very slight restoring forces are generated during vertical movement of the tone arm. For example, in one embodiment restoring forces in the range of 1-5 milligrams (mg) were generated for a 1/4 inch vertical movement of the tone arm.Such restoring forces can be considered inconsequential when compared to conventional tracking forces measured in grams. In effect, because applicant's specially constructed lateral counterweights provide the tone arm with lateral stability with a minimum increase of inertia, the pivot point essentially coincides with the center of gravity to effectively eliminate vertical restoring forces which plague conventional tone arm assemblies of the Stanton type.

As will become evident from a reading of the following specification and claims, the tone arm assembly of the present invention also includes additional structural features which further reduce the amount of distortion introduced into the sound reproduction process. For example, the tone arm itself is formed from a pair of concentrically extending tubular members having a plurality of spaced, acoustic dampening bands positioned therebetween to reduce resonances from being transmitted through the tone arm.

An object of the present invention is to provide a tone arm mounting assembly, wherein a unique unipivot bearing assembly pivotally supports a tone arm sub-assembly with the bearing assembly having a pivot point located in a horizontal line intersecting the center of gravity of the sub-assembly and extending perpendicular to a longitudinal axis of the tone arm sub-assembly.

A further object of the present invention is to provide a tone arm assembly wherein a pair of lateral counterweights extend from either side of the tone arm sub-assembly, the counterweights having a center of gravity aligned with and positioned vertically beneath the pivot point of the unipivot bearing assembly.

Another object of the present invention is to provide a tone arm assembly including a pair of lateral counterweights positioned within a vertical plane extending substantially parallel to the major axis of the tone arm stylus and pernendicujar to the stylus cantilever.

Another object of the present invention is to provide a tone arm assembly, wherein the tone arm itself includes a pair of concentrically arranged tubular shaft members having a plurality of irregularly spaced, acoustic dampening bands extending therebetween to dampen resonances within the tone arm.

A further object of the present invention is to provide a tone arm assembly, wherein a forward portion of the tone arm is releasably attached to a central housing assembly through a quick-release coupling mounted near the pivot assembly to keep the additional weight of the connector from appreciably adding effective mass to the tone arm, as it would if mounted at the front end of the arm, as well as to allow for easy disassembly of the tone arm assembly for shipment and simple replacement of pickup cartridges already mounted on the forward headshell assembly.

A further object of the present invention is to provide a tone arm mounting assembly which can be easily adjusted in both the vertical and horizontal directions relative to a frame portion of the phonograph assembly.

Another object of the present invention is to provide a tone arm assembly, wherein a first type of relatively thick signal wire is positioned within the forward portion of the tone arm for durability in handling by the user, and relatively fine Litztype signal wire is positioned within the remaining portion of the tone arm as well as within the mounting assembly to reduce the drag of the signal wire on the pivoting movement of the tone arm.

Another object of the present invention is to provide a removably attached rear counterweight assembly which employs a rack and pinion drive for adjusting the position of the rear counterweight relative to the stylus without rotating the counterweight.

A yet further object of the present invention is to provide a tone arm assembly, wherein a rear counterweight mounted on the tone arm is effectively decoupled from the tone arm by supporting the counterweight entirely on a resilient material positioned between the counterweight and support collar extending therethrough.

Each of these objects is achieved in a preferred embodiment of the present invention, wherein a tone arm assembly includes a sub-assembly having a pivot pin extending therefrom. The pin pivotally engages a cup-shaped recess formed on a support member, with the pivot point falling within a horizontal line intersecting the center of gravity of the tone arm sub-assembly and extending perpendicular to an axis extending through the sub-assembly from a pick-up cartridge positioned at one end to a rear counterweight positioned at an opposite end. The tone arm assembly further includes a pair of aligned, lateral counterweights attached to opposite side portions of the tone arm subassembly, with the center of gravity of the lateral counterweights positioned vertically beneath the pivot point of the tone arm sub-assembly.The lateral counterweights are preferably arranged such that a vertical plane intersecting the counterweights extends substantially parallel to the longitudinal or major axis of the stylus and perpendicular to the stylus cantilever. The tone arm sub-assembly also includes a pair of concentrically positioned tubular tone arms having a plurality of spaced, acoustic dampeners extending therebetween. Preferably, the acoustic dampeners are irregularly spaced from one another to absorb vibrations over a wide spectrum of frequences. A silicone fluid may be positioned between adjacent dampeners to further reduce resonances from developing within the tone arm.The unipivot bearing assembly is immersed in a container of heavy silicone-like fluid which lubricates the pivot contact surfaces to reduce the force necessary for pivoting the tone arm assembly relative to the support member, and provides effective damping of any remaining resonances which may be present. In particular, the fluid helps damp the low-frequency resonance peak which is present in all tone arms as a result of the interaction between the tone arm effective mass and the compliance of the stylus assembly, referred to as the CM resonance (CompliancexMass). The fluid also provides for improved arm tracking on warped records by applying controlled resistance to rapid vertical arm motion due to warps.This prevents the stylus from alternatively digging into the record surface on the bottom of a warp, or from leaving the surface of the record on the top of the warp, as in the tendency with any undamped tone arm pivot.

During normal arm motion, this damping resistance is effectively nil and does not impede the performance of the arm.

The present invention also includes a uniquely constructed rear counterweight assembly adaptable for removable attachment to a tone arm housing assembly. A cylindrical counterweight is supported on a band or ring of dampening material such as material sold under the tradename Sorbothane. The band is mounted on a carrier assembly adjustably mounted on a shaft forming a portion of the tone arm. A rack and pinion drive assembly is conveniently employed for adjusting the distance between the rear counterweight and the stylus. Because the counterweight assembly is easily removed from the tone arm, counterweights of varying weight can be employed dependent on the weight of the phonograph cartridge.

In a further embodiment, a uniquely constructed counterweight support assembly which includes a relatively thin ring of elastically deformable material positioned within a groove formed in an aperture extending transversely through a center portion of the counterweight is employed with the tone arm assembly. The deformable ring contacts a support collar extending through the counterweight, with the deformable ring providing the entire support for the counterweight. As a result, the counterweight tends to resonate at substantially the same frequency as the CM resonance of the pick-up cartridge discussed hereabove. This in turn, significantly improves the tracking performance of the tone arm assembly, reduces the chance of low-frequency overload and generally improves the lower frequency reproduction of the tone arm.

In yet a further embodiment, the single ring of elastically deformable material is replaced by a plurality of deformable plugs which are fixedly attached to the support collar and which extend into radial apertures formed in the counterweight.

By adjusting the degree of compression of the deformable plugs, it becomes possible to alter or tune the resonance of the counterweight to compensate for the different resonant frequencies generated by various pick-up cartridges. The greater the amount of compression of each deformable plug in the direction of the collar, the higher the resonant frequency of the counterweight. As the plugs are allowed to extend radially outward through the counterweight, the resonant frequency of the counterweight will decrease.

A further, distinctive feature of the present invention is a method of and apparatus for properly installing the tone arm assembly on a turntable, as well as properly installing the stylus on the tone arm. In particular, a base plate assembly supporting the tone arm assembly is fixedly mounted on the turntable. By selectively rotating a leadscrew extending from the base plate assembly, it becomes possible to alter the position of the tone arm assembly until an opening in the empty headshell is vertically aligned with a fixture removably mounted on the turntable spindle. When the tone arm assembly is properly aligned, lowering the tone arm will result in a portion of the mounting fixture entering the opening formed in the headshell.

Once the tone arm assembly is properly positioned relative to the turntable, the tone arm can be disconnected to allow for installation of the pick-up cartridge on the headshell. An alignment fixture is brought into abutment with the headshell and adjusted until the stylus tip aligns with a predetermined mark on the alignment fixture. By carefully adjusting the position of the cartridge, it also becomes possible to align the stylus cantilever with a predetermined mark on the alignment fixture. After the pick-up cartridge is properly aligned, it is fixedly attached to the headshell by tightening conventional fastening screws or the like.

The present invention will become apparent from a reading of the following specification and claims, together with the accompanying drawings, wherein similar elements are referred to and are indicated by similar reference numerals.

In order to obtain a better understanding of the present invention, reference is made to the accompanying drawings, wherein:~ Figure 1 shows a side view of a tone arm assembly formed in accordance with an embodiment of the present invention; Figure 2 shows a top view of a tone arm assembly of Figure 1; Figure 3A shows a partial cross-sectional view of the tone arm support assembly of Figure 1; Figure 3B shows a partial cross-sectional view of a modified support assembly; Figure 4 shows a cross-sectional view of a forward portion of the tone arm of Figure 1 taken between the section ends A-A'; Figure 5A shows a top view of the tone arm support assembly taken along section B-B of Figure 3A;; Figure 5B shows a bottom view of the tone arm support assembly taken along section C-C of Figure 3A; Figure 6 shows a further side view of the tone arm assembly and associated anti-skate mechanism attached thereto; Figure 7 shows an exploded view of the bearing mount assembly employed in the antiskate mechanism shown in Figure 6; Figure 8 shows a partial side view of a quick release coupling assembly employed in the embodiment of Figure 1, with the coupling assembly being in the disconnected mode; Figure 9 shows a partial side view of a tone arm assembly formed in accordance with an alternative embodiment of the present invention; Figure 10 shows a side view of a portion of the support shaft employed in the embodiment of Figure 3A;; Figure 1 A shows a perspective view of an alternative embodiment of a counterweight assembly formed in accordance with the present invention; Figure 11 B shows a cross-sectional view of the counterweight assembly taken along the plane D-D in Figure 1 1 A; Figure 12 shows a partial top view of a tone arm assembly formed in accordance with a preferred embodiment of the present invention; Figure 13 shows a side view of a further counterweight assembly adaptable for use with the present invention; Figure 14 shows a top view of the counterweight assembly of Figure 13; Figure 15 shows a cross-sectional side view of the counterweight assembly taken along the plane E-E in Figure 14;; Figure 16 shows a cross-sectional end view of the counterweight assembly taken along the plane F-F in Figure 15; Figure 1 7 shows a top view of the tone arm assembly during installation; Figure 18 shows an exploded view of the tone arm installation assembly; Figure 19 shows a perspective view of the stylus alignment assembly adaptable for aligning the pick-up cartridge in a tone arm headshell; Figure 20 shows an exploded view of an antiskate employed in the preferred embodiment of Figure 12; Figure 21 shows a blown-up perspective view of a portion of the tone arm assembly and attached anti-skate mechanism employed in the embodiment of Figure 12; Figure 22 shows an exploded view of a preferred tone arm support assembly employed with the embodiment of Figure 12; and, Figure 23 shows a cross-sectional view taken along the section G-G in Figure 22.

Referring to the drawings, and to Figure 1 in particular, a tone arm assembly formed in accordance with the present invention is generally designated at 10. Tone arm assembly 10 includes a housing assembly 12 having an arm 14 extending generally perpendicularly therefrom, Housing assembly 12 is adjustably supported above a frame portion 16 of a phonograph assembly and the like in a manner to be explained in detail hereafter.

Referring to Figure 4, arm 14 includes an outer, tubularly shaped member 18, and an inner, tubularly shaped member 20 extending concentrically therethrough. Tubular member 20 is formed with an outer diameter which is less than the inner diameter of tubular member 18, allowing a plurality of band-shaped acoustical dampening members 22 to be positioned between inner and outer tubular members 18 and 20, respectively. Dampening members 22 serve the dual purpose of maintaining the tubular members 18 and 20 in their proper concentric alignment as well as suppressing resonances from being transmitted through arm 14. In a preferred embodiment, bands 22 may be formed of an energy absorbing material such as sold under the tradename "Sorbothane". Alternatively, the bands could each be formed from a single piece of any conventional rubber-like material positioned between tubular members 18 and 20.

Furthermore at least some of the bands are preferably spaced from one another at irregular distances of between one-to-two inch intervals to minimize the build-up of resonance nodes. A layer of silicone-like rubber material can be injected into the gaps formed between adjacent bands 22 to further supress resonances, as well as to allow for easy assembly of arm 14.

Referring to Figures 1 and 2, an end portion of pick-up arm 14 fixedly engages a cartridge support member or head shell 24. For reasons which will become clear, head shell 24 must be both strong as well as lightweight. As a result, headshell 24 may be made of a material such as machined aluminium, or a moulded resin compound such as Dupont "Rynite". Headshell 24 includes a sleeve-shaped end portion 26 which surrounds and engages pick-up arm 14. At least one web-shaped gusset 28 extends between a first leg portion 30A and a second leg portion 30B attached thereto. Leg portion 30A joins end portion 26 and extends vertically above pick-up arm 14, with leg portion 30B extending substantially parallel to arm 14. As best shown in Figure 2, leg portion 30B includes a first section 32 which joins leg portion 30A, and a second section 34 which forms an oblique angle with section 32.Finally, headshell 24 includes a raised end portion 36 integrally attached to section 34 and having a curved lower surface to allow an operator to easily grasp and lift end portion 36 and attached arm 14 from a record surface, not shown. A plurality of apertures 38 extend through leg portion 30B of headshell 24 in order to minimize the overall weight of headshell 24. The L-shaped configuration of headshell 24 is specifically chosen such that the center of gravity of the pick-up cartridge is horizontally aligned with the center of gravity of arm 14 and a counterweight 136 for reasons which will become clear hereafter. The procedure of aligning the stylus tip during initial installation of the cartridge will be discussed in detail in a further portion of the specification.

Turning now to Figure 3A, a cross-sectional view of housing assembly 12 is shown. Housing assembly 12 encloses and supports a unipivot bearing assembly capable of supporting tone arm assembly 10 when pivoted through a vertical plane as may occur during the tracking movement of arm 14 across a warped record surface without generating adversely directed restoring forces. In particular, housing assembly 12 includes a substantially cup-shaped cap member 40 and a separate, sleeve-shaped body; member 42 positioned adjacent thereto. Each of the members 40 and 42 includes a plurality of complementary threads 44 formed along confronting end portions in order to threadedly attach members 40 and 42 to each other. Inner wall surfaces of members 40 and 42 enclose and form a hollow chamber 46 which extends longitudinally through a substantial portion of housing assembly 12.In addition, cap member 40 further includes a threaded aperture 48 extending therethrough, with aperture 48 being aligned with a longitudinal axis through a center portion of cap member 40.

Finally, a pin member 50 includes a threaded end portion extending within aperture 48 and a further, cylindrically-shaped hollow end portion 52 extending through a portion of chamber 46.

A support shaft 54 extends vertically above frame portion 16 of the phonograph assembly and includes an elongated, cup-shaped end portion 56 positioned within chamber 46 such that end portion 56 surrounds the hollow end portion 52 of pin member 50. The cup-shaped end portion 56 includes a conical end surface 58 having a cup-shaped recess 62 formed in a radially central portion thereof. Furthermore, a pivot pin member 60 includes a cylindricallyshaped end portion extending within the hollow end portion 52 of pin 50 and further includes a tapered end portion pivotally engaging recess 62 as best shown in Figure 3A.In a preferred embodiment of the present invention, both pivot pin 60 and conical end surface 58 are formed of an extremely hard material, such as tungsten carbide, thereby allowing the pivot assembly to be polished to a smoothness comparable to sapphire but with increased load and shock capability. A heavy-weight silicone type fluid is introduced into cup-shaped end portion 56 to a level sufficient to immerse the tapered end portion of pivot 60 therein. The silicone fluid functions to reduce the friction between the engaging surfaces of pin 60 and recess 62 by forming a thin film of lubricant therebetween. More importantly, the fluid also dampens any resonances introduced into the pivot assembly to improve tracking of warped records as discussed previously.

Support shaft 54 further includes a slot-shaped opening 64 extending through an outer surface portion positioned adjacent to the cup-shaped end portion 56. Shaft 54 is also formed with a threaded end portion 68 positioned opposite from end portion 56, with a hollow passageway 70 extending through end portion 68 as far as slot 64. End portion 68 of shaft 54 extends through an opening 72 formed through frame portion 16 of the phonograph. In order to support shaft 54 in its proper position relative to frame 16, a base plate assembly surrounds shaft 54 and is fixedly attached to frame 16 in a manner to be described.

The base plate assembly includes a substantially rectangularly-shaped base plate member 74 formed with an elongated slot 76 extending through a central portion thereof. Base plate 74 is fixedly attached to frame portion 16 via a plurality of conventional connecting fasteners 78. The base plate assembly further includes a bushing member 80 having a hollow sleeve portion 82 of sufficient inner diameter to allow support shaft 54 to extend therethrough. Bushing 80 also includes a flange-shaped end portion 84 integrally attached to and extending radially outwardly from sleeve portion 82. The base plate assembly also includes a slide member 86 formed with a transverse aperture having a diameter sufficient to allow slide member 86 to surround sleeve portion 82 of bushing 80.Bushing 80 also includes a rib-shaped portion 81 which extends radially inwardly into a slot-shaped opening 83 formed in an outer surface of end portion 68, and best shown in Figure 10. As a result, rib portion 81 prevents shaft 54 from rotating during vertical and horizontal adjustment thereof.

A vertical adjustment member 88 comprises a thumb screw formed with a threaded central opening which surrounds and mates with the threaded end portion 68 of support shaft 54. By rotating screw 88 in either the clockwise or counterclockwise direction, shaft 54 is caused to move in a longitudinal direction therethrough. As a result, housing assembly 12 is either raised or lowered relative to frame 16.

In an alternative embodiment shown in Figure 3B, a locking mechanism is shown for preventing accidental movement of shaft 54 relative to bushing 80. in particular, a threaded aperture 85 extends substantially radially through end portion 84 of bushing 80. A plug 87 formed of a nylonlike material is positionable within aperture 85 and can be forced against end portion 68 of shaft 54 by introduction of a set screw 89 into aperture 85. Set screw 89 may be selectively advanced through aperture 85 until plug 87 is pressed against end portion 68 with a force sufficient to prevent accidental movement of the shaft. It is to be noted in the embodiment of Figure 3B that rib portion 81 and slot 83 have been eliminated, with set screw 89 and plug 87 functioning to prevent misalignment of the tone arm assembly.

Returning now to a discussion of the embodiment shown in Figures 3A, 5A and 5B, slide member 86 and flanged end portion 84 of bushing 80 overlap opposite sides of slot 76, with a pair of connecting pins 94 extending between and fixedly engaging slide 86 and flange 84 to one another. In particular, slide member 86 includes a pair of lower lip portions 90A and 90B which engage recessed wall surfaces 92A and 92B formed in a lower side portion of plate 74 on either side of slot 76, while flanged end portion 84 includes a pair of overlapping lip portions 93A and 93B which engage an upper side portion of plate 74 on either side of slot 76.This unique overlapping construction of flanged end portion 84 and attached slide 86 functions to prevent slide 86 from vertically separating from base plate 74, while at the same time allowing slide 86 and flanged end portion 84 to move in a transverse direction along slot 76. A first support sleeve assembly 100 is fixedly mounted on the base plate 74 and a second, threaded support sleeve assembly 102 is fixedly mounted on slide member 86. A connecting pin 104 includes a non-threaded portion extending through the first sleeve assembly 100, with a circumferentially extending groove formed in pin 104 receiving an end portion of a key member extending from sleeve 100. Pin member 104 also includes a threaded end portion extending through the threaded support sleeve assembly 102.

In order to adjust the horizontal position of support shaft 54 relative to base plate 74, it is merely necessary to rotate pin member 104 in either a clockwise or counterclockwise direction.

Because of the engagement between the key extending from sleeve 100 and the groove formed in pin 104, pin 104 may rotate relative to sleeve 100 but is constrained from moving in the longitudinal direction relative thereto. In effect, the key and groove connection fixes the position of pin 104 relative to base plate 74. However, because sleeve 102 and pin 104 are threadedly interconnected, rotation of pin 104 results in the horizontal movement of sleeve 102 and attached slide member 86, with the movement of slide member 86 causing a similar movement in bushing 80 and shaft member 54 extending therethrough.

In a further, preferred embodiment of the present invention, bushing 80 and thumb screw 88 are replaced by an alignment assembly generally indicated by numeral 69' in Figure 22.

The alignment assembly includes a generally rectangular mounting block 70' which is slidably mounted on base plate 74 in Figure 3A. Mounting block 70' includes a pair of openings 71' and 72' sufficient in size to allow a pair of shoulder bolts to pass completely through mounting block 70' and enter a slide member disposed on an opposite of the base plate, such as slide member 86. Such an arrangement allows mounting block 70' to reciprocate in opposite directions coinciding with a longitudinal axis Q-Q extending through mounting block 70'.In order to initiate movement of mounting block 70', a threaded adjustment pin, not shown, is inserted into a threaded bore 75' extending through a portion of mounting block 70' in a direction parallel to longitudinal axis Q-Q. By selective rotation of such a threaded pin, it becomes possible to alter the position of mounting block 70' relative to its fixedly positioned base plate.

Mounting block 70' functions to support a tone arm support shaft in a manner to be explained. In particular, mounting block 70' includes a cavity 80' having a generally rectangular configuration.

Cavity 80' includes an end surface 81' extending parallel to longitudinal axis qq and located along a plane substantially bisecting mounting block 70' into two equal portions. End surface 81' includes a semi-cylindrical portion 82' extending outwardly from cavity 80', with surface portion 82' having a radius of curvature substantially equal to a radius of curvature of a tone arm support shaft, not shown. Slidably disposed within cavity 80' is a clamping block 83' having a semi-cylindrical surface portion 84' aligned with and extending away from surface portion 82' of cavity 80'. By carefully sizing confronting surface portions 82' and 84' to form a cylindrical opening, it becomes possible to insert a tone arm support shaft completely through mounting block 70'. Clamping block 83' is pressed into frictional engagement with such a tone arm support shaft by appropriate rotation of a set screw 85' extending through mounting block 70' and into contact with clamping block 83'.

When it becomes necessary to alter the vertical position of a tone arm support shaft clamped within mounting block 70', it is only necessary to rotate set screw 85', allowing a pair of biasing springs 86' and 87' to press clamping block 83' away from end surface 81' of cavity 80'. Each biasing spring extends between a separate bore formed in clamping block 83' and a portion of end surface 81'. However, it is understood that each bore could be formed in end surface 81' rather than in clamping block 83'. The clamping block 83' is preferably formed of nylon or the like, which will not scratch or mar the tone arm support shaft.

Referring to Fig. 3a, a hollow attachment assembly 110 is connected to a side portion of body member 42 via a plurality of bolt-like connecting members 112. Attachment assembly 110 includes a hollow, hub-shaped end portion 114 extending perpendicularly away from housing assembly 12 and having a plurality of threads 11 6 formed along an outer surface portion thereof as best shown in Figures 8. Pick-up arm 14 includes a conically-shaped end portion 118 which is formed with an outer diameter slightly less than the outer diameter of hubshaped end portion 114. End portion 118 includes an end surface having a radially directed flange 120 extending circumferentially thereabout, with a rotatable locking ring 122 also surrounding end portion 118.Locking ring 122 includes an inner diameter having a plurality of threads which complement the threads 11 6 formed on hub-shaped end portion 114. Finally, end portion 11 8 of pick-up arm 14 encloses and supports a plurality of male electrical connectors 124 which are complementary in shape to a plurality of female electrical connectors supported within hub-shaped end portion 114.

To join pick-up arm 14 to housing assembly 12, the end portion 11 8 is brought into abutting relationship with hub end portion 114. This, in turn, brings the male electrical connectors 124 into engagement with the corresponding female electrical connectors. The threaded inner diameter of locking ring 122 is then brought into engagement with the threads 11 6 formed on hub portion 114. Locking ring 122 is then rotated onto hub portion 114 until an inner flange formed on locking ring 122 contacts stop flange 120 formed on end portion 118 of pick-up arm 14, thereby preventing further movement of locking ring 122.

Referring again to Figure 3A, a balancing arm 130 extends perpendicularly from body member 42, with arm 130 being displaced 1800 from attachment assembly 110 as measured about the circumference of sleeve member 42. A support collar 132 surrounds a portion of arm 130, with collar 132 including a hub-shaped portion and an integrally attached sleeve-shaped portion. A set screw 134 extends within a radial aperture formed through the hub-shaped portion of collar 132, with set screw 134 being selectively advanced through collar 132 until contact is made with arm 130, thereby fixedly attaching collar 132 to arm 130. A counterweight 136 includes a transverse opening extending through a longitudinal axis thereof, with the transverse opening having a diameter considerably larger than an outer diameter of the sleeve-shaped portion of collar 132.A groove 137A is formed in the inner wall surface of the transverse opening extending through counterweight 136, wherein a preferred embodiment of the present invention groove 137A has a depth of substantially onesixteenth (1/16) of an inch and a width of substantially one-eighth (1/8) of an inch, respectively. A ring of elastically deformable material 138 is positioned within groove 137A, with ring 138 having a radial inner surface in frictional contact with a similarly shaped groove 137B formed in the sleeve portion of collar 132.

Resilient ring 138 provides the sole support for counterweight 136 and is therefore capable of suppressing vibrations from being transmitted between counterweight 136 and arm 130. In one embodiment of the present invention, each of the arms 14 and 130 will share a single longitudinally directed axis extending therethrough.

Furthermore, arms 14, 130 and housing 12 form a tone arm sub-assembly having a center of gravity located in a horizontal plane extending through the center of gravity of tone arm 14 as well as counter balance arm 130. By carefully adjusting the position of pin 50 and cup-shaped member 56, the pivot point of the unipivot bearing can be made to coincide with a horizontal line intersecting the center of gravity of the tone arm sub-assembly and extending perpendicular to a longitudinal axis of the tone arm sub-assembly.

When such a condition exists, the tone arm subassembly has achieved a balanced condition wherein arm 14 can be pivoted in the vertical direction without generating appreciable restoring forces capable of affecting the position of the tone arm sub-assembly. Even though counterweight 136 can be moved to apply a tracking force to the pick-up cartridge attached to pick-up arm 14, such a tracking force does not constitute a restoring force as discussed hereabove, in that the tracking force is always directed toward the record surface while the restoring forces act in a direction opposite to the direction in which pick up arm 14 is pivoted.

An alternative embodiment of the present invention is shown in Figure 9, wherein a pick-up arm 14' permanently engages an attachment assembly 110' which, in turn, is attached to a housing assembly 12 via fasteners 112. In the alternative embodiment shown in Figure 9, the counter-balance weight 136 and resilient ring are similar to the weight and ring shown in Figure 3A.

However, the set screw 134 has been eliminated and a collar 132' is formed with a threaded inner surface which corresponds to a threaded outer surface formed on a counter-balance arm 130'.

By rotating collar 132' in either the clockwise or counterclockwise directions, both collar 132' and counterweight 136 are moved in a longitudinal direction relative to arm 130'.

In a yet further embodiment shown in Figures 11 A and 11 B, the grooves 137 A and B and the elastically deformable ring 138 have been eliminated. Rather, a plurality of preferably four cylindrical-shaped deformable plugs 1 39A-D are each fixedly attached to a sleeve-shaped portion of collar 1 32. Each of the plugs 1 39A-D may be circumferentially spaced at an interval of substantially 90C from adjacent plugs, and each of the plugs 139A-D extends into a separate radial aperture 141 A-D formed through counterweight 136.In addition, a plurality of cylindrical-shaped nylon plugs 1 43A-D are each introduced into radial outer end portions of apertures 141A-D. Finally, a plurality of set screw fastener assemblies 1 45A-D are also introduced into each radially disposed aperture 141A-D, respectively. By rotating the set screws 1 45A-D in a clockwise direction, end portions of the set screws are advanced into contact with nylon plugs 1 43A-D. Further clockwise rotation of set screws 1 45A-D forces the plugs 1 43An D to abut and compress deformable plugs 1 39A-D, respectively.By altering the size of each plug 1 39A-D, the vibrational dampening characteristics of the plug are also altered, thereby allowing one to alter or tune the resonant frequency of the counterweight in order to compensate for various pick-up cartridges employed with the tone arm assembly. In particular, as the initial size of the plugs 1 39A-D is reduced by compression of the plugs, the higher the resonant frequency obtainable by the counterweight. Likewise, as the set screws 1 45A-D are withdrawn, the deformable plugs 1 39A-D expand and yield the lowest frequency.

The counterweight assembly discussed hereabove in conjunction with Figure 3A can only work properly if the center of gravity of counterweight 136 coincides with a longitudinal axis of balancing arm 130. If either counterweight 136 or ring 138 were not "true", rotation of counterweight 136 would serve to displace the center of gravity of counterweight 1 36 from its proper position.

In order to overcome this potentially serious problem, a preferred counterweight assembly 200' shown in Figures 12~16 has been carefully constructed to eliminate rotation of the counterweight. As shown in Figure 15, a balancing arm 202' is attached to a mounting shoe 204', itself attached to sleeve-shaped body member 42. In particular, mounting shoe 204' is formed with a vertically extending, substantially T-shaped retaining pocket 206'. Retaining pocket 206' extends downwardly from an upper surface of shoe 204' to a position approximately threequarters the distance to a bottom surface of shoe 204'. A further opening 208' extends through the vertically lower portion of shoe 204' in a direction substantially perpendicular to the longitudinal axis of pocket 206'.During assembly, a conventional fastening screw 210' is inserted through opening 208' and into an aligned opening formed in member 42, thus fixedly attaching shoe 204' to member 42.

Balancing arm 202' is preferably formed with a substantially rectangular cross-sectional configuration and includes a T-shaped end portion 212' compatible in size and shape to the Tshaped pocket 206' formed in mounting shoe 204'. However, it is considered within the scope of the present invention to form balancing arm 202' with any conventional cross-sectional shape. Likewise, end portion 212' can be formed of any conventional shape, provided that pocket 206' is formed with a compatible shape to allow insertion of end portion 212' therein.

An indexing cursor 214' is slidable mounted on balancing arm 202' at a location remotely positioned from end portion 212'. Cursor 214' includes a hollow body portion 216' surrounding balancing arm 202' and an elongated rod portion 218' extending parallel to balancing arm 202'. A pointer 220' extends from an end of rod 218' and is conveniently aligned with a graduated scale 222' covering a vertically upper surface portion of balancing arm 202'. Finally, an adjustment screw 224' extends through body portion 216' into frictional engagement with balancing arm 202' to releasably fix the position of cursor 214 relative to scale 222' in a manner which will become clear.

A carrier assembly 230' includes a U-shaped sleeve 231', partially encloses balancing arm 202' as best shown in Figure 16. Carrier sleeve 231' includes a pair of parallel extending leg portions 232A' and 232B' interconnected by an intermediate portion 232C'. Portions 232A-C' are sized to slidably engage confronting surface portions of balancing arm 202' when the arm is fully inserted into the carrier assembly. A pinion gear 234' is mounted for joint rotation with a drive shaft 236' extending between leg portions 232A' and 232B', respectively. Drive shaft 236' engages an adjusting handle 238' partially shown in Figure 16 and better shown in Figure 14. By rotating handle 238' in either a clockwise or counterclockwise direction, it becomes possible to rotate pinion gear 234' in a corresponding direction.A wave-spring washer 239' is inserted between the adjusting handle 238' and carrier leg 232A' to provide locking friction for preventing undesired rotation of pinion gear 234'. Washer 239' may be formed of metal, Teflon or any conventional material. Furthermore, washer 239' can be located on any convenient portion of drive shaft 236', providing that washer 239' contacts a relatively fixed surface to provide a frictional braking force.

A hollow, cylindrically-shaped counterweight 240' surrounds an end portion of carrier assembly 230' confronting mounting shoe 240'.

Counterweight 240' may be formed as a single member, or counterweight 240' may comprise a pair of ring-shaped members 242' and 244' disposed side-by-side as shown in Figure 15. If two members are employed, a clamping ring 245' is preferably inserted in facing grooves extending about the circumference of each member.

Regardless of whether one, two or a plurality of members are employed to form counterweight 240', the entire counterweight is supported on a ring of energy absorbing material 246' mounted in a groove 247' formed in an outer surface carrier assembly 230'. Preferably, ring 245' is formed of an energy absorbing material of the type sold under the tradename "Sorbothane", however, it is within the scope of the present invention to employ any conventional energy absorbing material.

In order to alter the position of counterweight 240', a lower surface of balancing arm 202' includes a rack gear 248' adaptable for intermeshing with pinion gear 234'. By appropriate rotation of handle 238', drive shaft 236' and pinion gear 234' relative to rack gear 248', it is possible to adjust the position of the carrier assembly and counterweight mounted therein along the relatively fixed balancing arm 202'.

To properly calibrate counterweight assembly 200', it is necessary to first adjust the position of counterweight 240 until the tone arm achieves a zero balanced position. Such a zero balanced position is characterized by the tone arm maintaining a rest position when left on its own.

Once zero balance is achieved, the indexing cursor 214' slid along balancing arm 202' until pointer 220' is vertically aligned with a graduated scale marking of zero (0). In order to apply a positive tracking force to the tone arm stylus, it is merely necessary to rotate handle 238' and thereby adjust the position of carrier assembly 230' and counterweight 240' along balancing arm 202' in a direction toward member 42 and away from indexing cursor 214'. After carrier assembly 230' has moved a predetermined distance, the pointer will become aligned with a numeral, typically one (1) to three (3) on graduated scale 220'. The position may conveniently correspond to the required tracking force in grams depending on the measuring scale employed.

One of the distinctive advantages of counterweight assembly 200' is the ability to quickly alter the particular counterweight employed as may be required by the weight of the pick-up cartridge. Depending on the weight of the pick-up cartridge (often between 2.5 and 20 grams) it is now possible to employ one of several counterweights by merely removing a first counterweight assembly and substituting a second, entirely separate counterweight assembly. in conventional assemblies employing a single counterweight, the weight may have to be positioned a considerable distance from the pivot point to properly balance the phono cartridge. Such an arrangement significantly increases the overall inertia of the tonearm assembly.In comparison, the ability to change counterweights as with the present invention allows for positioning of the properly chosen weight much closer to the pivot point, thereby minimizing the inertia of the system.

In order to provide sideways or lateral stability for the tone arm sub-assembly shown in Figures 1,2 and 6, respectively, a pair of lateral counterweights 144 and 146 are mounted on a pair of threaded shafts 148 and 150, with the shafts extending in perpendicular directions from opposite side portions of body member 42. In particular, each shaft 148 and 150 extends within a plane which is bisected by a longitudinal axis extending between pick-up arm 14 and counterbalance arm 130. Furthermore, shafts 148 and 150 are aligned with one another and are attached to a portion. of body member 42 such that the center of gravity of the counterweights 144 and 146 is located on a line extending vertically beneath the pivot point formed by pivot pin 60 and recess 62.As a result, a beam-balance mounting system is achieved with respect to sideways or lateral pivoting movement of housing assembly 12 and attached pick-up arm 14. This means that any sideways pivoting movement of pick-up arm 14 toward either of the counterweights 144 and 146 generates a restoring force which attempts to return pivot pin 60 to its initially vertical position. Furthermore, the restoring forces generated by counterweights 144 and 146 does not appreciably affect the vertical pivoting movement of the tone arm subassembly as occurs during vertical tracking over a record surface. In an embodiment of the present invention, both of the counterweights 144 and 146 are concentrically mounted on their respective shafts 148 and 150.However, it is considered within the scope of the present invention to eccentrically mount each of the counterweights 144 and 146, provided the center of gravity of the resulting assembly is located on a line extending vertically beneath the pivot point of the unipivotly supported tone arm sub-assembly.

In a preferred embodiment of the tone arm sub-assembly shown in Figure 12, a pair of counterweights 144' and 146' are disposed along an axis R-R extending intersecting a line vertically beneath the center of gravity of a tone arm sub-assembly 10'. In order to prevent the stylus, not shown, from rolling when vertically tracking over a warped record surface, it is necessary to displace axis R-R from a transverse axis T-T by an angle a. Angle a is identical to the offset angle a the stylus cantilever, aligned with axis S-S in Figure 2, is displaced from the longitudinal axis Y-Y of the tone arm assembly also shown in Figure 2.In effect, lateral counterweight 146' and counterweight 144' are each displaced by an angle as measured in a clockwise direction from traverse axis T-T. The precise angle a is inversely related to the actual distance measured between a vertical plane extending through the stylus tip and a further vertical plane extending through the pivot assembly in the center of the housing assembly.

For example, if the actual distance is measured to be 240 mm, angle a should be 22.9 . In comparison, for a distance of 235 mm, angle a becomes 23.4 . Thus, a is determined by the location of the stylus tip relative to the pivot point. The axis R-R is then arranged to be perpendicular to the axis S-S defined by the angle zg. By pivoting the counterweights 144' and 146' by an angle a as shown in Figure 12, the vertical pivoting plane for counterweights 144' and 146' extends parallel to a major axis through the pick-up cartridge and perpendicular to the stylus cantilever. As a result, the stylus is maintained in its correct, upright position at all times when vertically tracking over even a warped record surface.In comparison, lateral counterweights extending transversely to the longitudinal axis of a tone arm sub-assembly cannot prevent the tone arm from rolling in a transverse direction as the stylus moves in a vertical direction along warped record surface.

The distinctive advantage of displacing the axis of the lateral counterweights as set forth hereabove thus becomes immediately apparent in maintaining an upright position of the stylus regardless of the vertical tracking movement.

As shown in Fig. 3a, a holder assembly 160 preferably formed of aluminum material surrounds and is fixedly attached to support shaft 54 at a position adjacent to slot 64. Holder assembly 160 provides a support for an anti-skate mechanism, a manual arm-lift assembly, and an arm rest assembly all attached thereto. In particular, holder assembly 160 includes a forward portion 161 extending substantially parallel to and spaced beneath pick-up arm 14 when pick-up arm 14 is in a rest position. Forward end portion 161 includes a horizontal leg portion 162 extending substantially perpendicular thereto, such that leg portion 162 and support shaft 148 extend substantially parallel to one another when shaft 148 is in the rest position.

Leg portion 162 includes a vertically extending flange 164 attached to an end portion thereof, with flange 164 extending substantially parallel to shaft 54. It is noted from Figure 2, that flange 164 is inclined at an angle to a longitudinal axis ZZ extending through leg portion 162. Flange 164 further includes an aperture 166 extending transversely through an upper end portion thereof, with a threaded screw 168 rotatably supported within aperture 166. As shown in Fig.

7, a miniature precision bearing assembly 170 is mounted on threaded screw 168, with a ringshaped sleeve 172 rotatably mounted on bearing assembly 170. A washer member 174 is also mounted on screw 168, such that washer 174 is located between bearing assembly 1 70 and flange 164. Ring-shaped sleeve 172 includes a pair of apertures 176 and 178 each extending radially therethrough, with the apertures being circumferentially spaced 900 from one another. A first pin member 180 is supported within aperture 176, while a second pin member 182 is supported within aperture 178. Each of the pin members 180 and 182 extend outwardly from ring-shaped member 172 in a substantially radial direction.A notch 184 is cut in a radially outer end portion of pin 180 and a counterweight 186 mounted on pin 182 is adjusted via a set screw 188 extending through aperture 190 in the counterweight and into frictional contact with pin 182. Finally, a thread 192 of polyester-like material includes a first end portion fixed within notch 184 of pin 180 and a second end portion fixed about counter-balance arm 130.

The operation of the anti-skate mechanism is best shown in Figure 6, wherein the anti-skate mechanism has been illustrated at three positions which occur during operation of the tone arm assembly 10. In particular, when pick-up arm 14 is in the rest position, the pin and counterweight assume a position substantially as designated at 180" and 186", respectively. As pick-up arm 14 is pivoted to bring the stylus into contact with the beginning of the record, the anti-skate mechanism moves to the positions designated at 180' and 186' due to the pull of thread 192 on pin 180. Finally, as the stylus approaches the end of the record, the anti-skate mechanism assumes the position designated at 180 and 186, respectively.By carefully adjusting the position of counterweight 186 on pin 182, an anti-skate force is generated which tends to maintain the tone arm assembly 10 in its proper lateral position relative to the record surface, not shown.

Because of the rolling action of the thread 192 against the outer surface of housing assembly 12, the friction developed between the thread and the housing is effectively non-existant. It is to be noted that thread 192 should extend in substantially the same horizontal plane which includes the pivot point of the unipivot bearing assembly when the anti-skate mechanism assumes the position 180 and 186 to prevent tone arm assembly 10 from twisting about shaft 54.

A further, preferred embodiment of an antiskate mechanism employed with present invention is shown in Figures 12 and 20. In the embodiment of Figure 12, leg portions 162 and 1 64 have been eliminated. Rather, a biasing bearing holder 180' is threaded directly into a holder assembly 160'. As shown in detail in Fig.

20, bearing holder 180' includes a threaded end portion 1 81'; and a cup-shaped end portion 182' oppositely disposed therefrom. A ball bearing assembly 183' is pressed into a cavity 148' defined by cup-shaped end portion 182'. An attachment screw 184' extends through a central opening 185' in bearing assembly 183' and is threaded into engagement with a bias bearing collar 186', thereby aligning collar 186' with holder 180'. Collar 186' has a substantially cylindrical configuration and includes a pair of circumferentially spaced apertures 187' and 188' formed in outer surface portions thereof.

Preferably, apertures 187' and 188' are circumferentially spaced substantially 900 from one another in a manner similar to apertures 176 and 178 formed in sleeve 172 in the embodiment of Figure 7. A first lever 1 89' extends outwardly from opening 187', while as second lever 190' extends outwardly from opening 188'. Each lever includes a threaded end portion adaptable for engaging threads formed in a respective opening.

Furthermore, opening 188' preferably forms an angled trajectory, such that an acute angle of less than 900 is formed between second lever 1 900 and a longitudinal axis of holder 180'. A substantially cylindrical counterweight 191 is mounted such that second lever 190' extends completely through an axial passageway 192' formed through counterweight 1 91'. A springloaded ball plunger 193' extends through a radial opening in counterweight 191' and frictional contacts lever 190' to prevent undesirable slippage of counterweight 191 A A pair of notches or grooves 194A' and 1 94B' formed in spaced portions of lever 190' provide end adjustment positions for counterweight 1 '. As counterweight 191' is moved along lever 190', the spring-pressed plunger provides rolling resistance. When either of the grooves 1 94A' or 194B' are encountered, the plunger is spring pressed into the groove to prevent further movement of the counterweight.

The first lever 189' includes a notch or groove 195' formed at a location remotely disposed from collar 186', with notch 195' receiving a thread of polyester-like material 196' extending from shòe 204'. An opposite end of thread 196' is retained in a boss 197' attached to mounting shoe 204'.

Boss 197' includes a slotted opening 198' sufficient in size to allow insertion of thread 196' and yet of insufficient size to allow passage of an aluminum crimp 199' attached to thread 196'.

A manual arm lift assembly is generally designated at 194, and includes a vertical lift member 196 and a horizontally extending support surface 198 attached thereto. A control arm 200 is attached to the vertical lift member 196 through a conventional cam arrangement such that selective pivotal movement of control arm 200 results in the vertical movement of lift member 196 and attached surface 198, thereby raising pick-up arm 14. A substantially L-shaped rest member 202 extends parallel to pickup arm 14 and includes an end portion attached to the forward portion 161 of holder assembly 160. Rest member 202 includes a cradle-shaped end portion having a flap 204 hinged thereto. Flap 204 and cradle end portion surround and enclose pick-up arm 14, with flap 204 being pivoted to an upright position to allow for removal of pick-up arm 14 from rest member 202.

Turning again to Figure 3A a hollow conduit 210 is shown to extend axially through a portion of sleeve member 42 and slot 64. Conduit 210 surrounds and supports a portion of signal wire generally designated at 212 which extends from the stylus, through inner tubular member 18, attachment assembly 110 and conduit 210. The wire then travels through the hollow passageway 70 formed in shaft 54. In a preferred embodiment of the present invention, a heavy duty signal wire, for example 30 gauge wire, may be employed within tubular member 18, while a much lighter weight Litz-type wire, for example 44 gauge, may be employed within attachment assembly 110 and conduit 210 to significantly reduce the overall drag effect of the wire on the pivotal movement of pick-up arm 14.While 30 gauge and 44 gauge have been cited as examples of the type of wire employed, it is within the scope of the present invention to employ any conventional gauge signal wire for transmitting through the tone arm assembly. For example, the Litz-type wire may be replaced with 5 twisted strains of 44 gauge wire.

Shaft member 54 may be formed of a material such as brass, while the upper section 40 of housing 12 may conveniently be formed of either plexiglass, aluminum, or a resin-based plastic compound such as sold under the trade name "Rynite", with the lower section 42 of housing 12 being formed of aluminum. However, a variety of other, similar type materials may be employed for housing 12 as well as shaft 54.

The present invention also provides a unique apparatus and method for properly installing the tone arm assembly as well as the pick-up cartridge. It is assumed that the effective length of the tone arm, i.e. the distance along an imaginary line drawn between the horizontal pivot and the stylus tip is known. It is further assumed that the offset angle, i.e. the angle between the longitudinal axis of the stylus cantilever and imaginary line defining the effective length is known. Finally, it is assumed that the overhang, i.e. the distance the stylus tip should extend beyond the turntable spindle is known. Even though these geometrical relationships are easily determinable for a specific tone arm assembly, many conventional tone arm makers fail to provide sufficient information on how to precisely install the tone arm and its pick-up cartridge.In comparison, the present invention provides a quick and highly accurate procedure for installing the tone arm with minimum error.

For purposes of explanation only, it may be assumed that the tone arm assembly 10 shown in Figures 17-19 has the following dimensions: effective length 235 mm, offset angle of 23.5 , and overhang of 17.638 mm. For purposes of explanation, the effective length is designated EL, the offset angle is designated angle a and the overhang is designated OH.

An alignment nipple 30' includes a body 31' having cylindrically-shaped opening 32' sufficient in size to allow nipple 30' to be inserted on a spindle S extending from a turn table, not shown.

A pin-shaped projection 13' extends from body 31' in a direction coinciding with the longitudinal axis of spindle S. Projection 33' has an outer diameter slightly less than a diameter of an aperture 34' formed through a portion 39B' of a headshell 24'.

Alignment nipple 30' is removably mounted on spindle S and a tone arm assembly 10 including headshell 24' is pivoted until aperture 34' is vertically aligned with pin-shaped projection 33'.

When headshell 24' is properly positioned over spindle S projection 33' is capable of insertion through aperture 34'. In order to establish the correct mounting position of the tone arm base plate on the turntable prior to alignment of headshell 24' with spindle S, a template may be employed.

Once the tone arm assembly has been properly positioned on the turntable, the arm tube can be disconnected to provide for installation of the pick-up cartridge on the headshell 24'.

An alignment fixture 40' is preferably employed to ensure precise positioning of the pick-up cartridge. The alignment fixture 40' preferably includes an L-shaped member formed by a pair of leg portions 42' and 44' extending perpendicular to one another. Leg portion 42' includes three spaced flange portions 45A', 45B' and 45C' extending outwardly therefrom. Each of the flanges 45A' and 45C' have generally similar shapes and are spaced sufficient distances from flange 45B' to allow insertion of an adjustment tool such as a screw driver therebetween. Flange 45B' has a substantially rectangular configuration and includes a cylindrically-shaped boss 46' extending parallel to leg portion 44'. Boss 46' has a diameter slightly less than a diameter of an aperture 48' extending through headshell 24'.

Alignment fixture 40' further includes a substantially rectangularly shaped clear plate 50' pivotally attached to an end of leg portion 44' remotely positioned from leg portion 42'.

Preferably, plate 50' is formed of plexiglass or the like and can be pivoted to either side of leg portion 44'. A cross-hair index 52' is formed on plate 50' with a point of intersection 53' corresponding to proper overhang of the stylus tip, in this example 1 7.638 mm ahead of spindle S.

Headshell 24' is inverted and positioned such that boss 46' projects through aperture 48'. A pick-up cartridge, not shown, is then arranged on headshell 24' until the stylus tip contacts crosshair intersection 53'. The pick-up cartridge is further adjusted such that the stylus cantilever aligns with the longitudinal axis of plate 50' as manifested by cross-hair 54'. Once the pick-up cartridge is properly mounted on headshell 24', an appropriate fastening tool is inserted between flanges 45A' and 45B' and between flanges 45B' and 45C' to tighten conventional fastening screws extending from the pick-up cartridge into clamping engagement with the headshell.

The present invention is not to be limited to the above-discussed embodiments, but is to be limited only by the scope of the following claims.

Claims

Claims

1. A phonograph assembly of the type including a pivotable tone arm sub-assembly having a longitudinal axis extending from a pickup cartridge mounted at one end of the tone arm sub-assembly to a counterweight mounted at an opposite of the tone arm sub-assembly; unipivot bearing means supported on said phonograph assembly for supporting said tone arm sub-assembly for pivotal movement about said unipivot means, said unipivot bearing means including a unipivot bearing located on an imaginary horizontal line passing through a center of gravity of said tone arm sub-assembly and extending perpendicular to said longitudinal axis of said tone arm sub-assembly.

2. A phonograph assembly according to claim 1, wherein said unipivot bearing means comprises a pivot pin assembly attached to said tone arm subassembly and formed with a tapered end portion; said bearing means further comprises a cupshaped support member mounted on said phonograph assembly and partially filled with a silicone-like fluid, wherein said tapered end portion extends through said fluid and pivotally engages said cupshaped support member.

3. A phonograph assembly of the type including a substantially rigid tone arm subassembly having one end attached to a housing and a pick-up cartridge attached to a further end portion thereof, said tone arm sub-assembly including a first tubular member and a second tubular member surrounding and spaced from said first tubular member, with each tubular member extending between said housing and said pick-up cartridge, and a plurality of separate dampening means each positioned between the first and second tubular members for suppressing resonances from being transmitted through said tone arm sub-assembly.

4. A phonograph assembly according to claim 3, wherein said plurality of dampening means comprises a plurality of separate bands of plasticlike material extending between said first and second tubular members and irregularly spaced from one another.

5. A phonograph assembly of the type including a support assembly pivotally supporting a tone arm assembly mounted thereon, said tone arm assembly including a support collar and balancing arm extending through said support collar and a counterweight surrounding a portion of said support collar, with a pair of radially aligned grooves formed in confronting surface portions of said support collar and said counterweight, and dampening means engaging and extending between said pairs of radially aligned grooves for supporting said counterweight while suppressing vibrations from being transmitted between said counterweight and said balancing arm, said dampening means comprising a ring of resiliently deformable material.

6. A phonograph assembly of the type including a support assembly pivotally supporting a tone arm assembly mounted thereon, said tone arm assembly including a support collar and a balancing arm extending through said support collar and a counterweight surrounding a portion of said support collar, with said counterweight including a plurality of radially extending apertures circumferentially spaced from one another, dampening means extending between said counterweight and said support collar for supporting said counterweight while suppressing vibrations from being transmitted between said counterweight and said balancing arm, said dampening means comprising a plurality of cylindrically-shaped plugs of resiliently deformable material, with each plug aligned with and extending into one of said radially extending apertures.

7. A phonograph assembly according to claim 6, wherein said dampening means further comprises a screw and plug assembly mounted in each of said radially extending apertures, with each of said plugs contacting and selectively compressing one of said deformable plugs against said support collar.

8. An assembly for balancing a tone arm subassembly during vertical tracking across even highly warped record surfaces without generating oppositely directed restoring forces, and comprising:~ a phonograph assembly including a frame with a support assembly extending therefrom; a tone arm sub-assembly having a longitudinal axis extending therethrough and including a housing portion positioned adjacent to said support assembly and further including a tone arm portion extending outwardly from a side of said housing and a balancing arm portion extending outwardly from an opposite side of said housing, wherein said tone arm portion supports a pick-up cartridge and attached stylus and said balancing arm portion supports a counterweight with said longitudinal axis extending therebetween; and unipivot bearing means extending between said tone arm sub-assembly and said support shaft and having a pivot point coinciding with an imaginary horizontal line passing through a center of gravity of said tone arm sub-assembly and extending perpendicular to said longitudinal axis of said tone arm assembly, allowing said tone arm sub-assembly to pivot in a vertical direction without generating oppositely directed restoring forces.

9. A tone arm balancing assembly according to claim 8, wherein said tone arm portion includes a first tubular member and a second tubular member surrounding and radially spaced from said first tubular member, said tone arm portion further includes a plurality of separate dampening members positioned between said first and second tubular members, with said dampening members spaced from one another.

10. A tone arm balancing assembly according to claim 9, wherein each of said dampening members includes a bank of material for the type sold under the tradename Sorbothane surrounding said first tubular member and contacting and supporting said second tubular member, with said plurality of bands of Sorbothane irregularly spaced from one another.

11. A tone arm balancing assembly according to claim 9, wherein said first tubular member is concentrically positioned within said second tubular member and a signal wire assembly extends through said first tubular member between opposite end portions thereof.

12. A tone arm balancing assembly according to claim 10, wherein a layer of silicone-like rubber fills a plurality of gaps formed between adjacent bands of dampening material.

13. A tone arm balancing assembly according to claim 8, wherein cartridge support means engage an end portion of said tone arm portion for supporting said cartridge and attached stylus in a position having the center of gravity of said cartridge horizontally aligned with the center of gravity of said tone arm portion.

14. A tone arm balancing assembly according to claim 13, wherein said cartridge support means comprises a substantially L-shaped bracket member including a sleeve-shaped end portion fixedly attached to the confronting end portion of said tone arm portion, said L-shaped bracket including a first leg portion attached to said sleeve-shaped end portion and extending in a substantially vertical direction above said tone arm portion, said L-shaped bracket further including a second leg portion attached to said first leg portion and extending substantially parallel to said tone arm portion.

15. A tone arm balancing assembly according to claim 14, wherein said second leg portion includes a first section joining said first leg portion and a second section joining and extending at an oblique angle to said first section, said cartridge and attached stylus fixedly engaging said first and second sections of said second leg portion and extending at an angle with respect to a longitudinal axis extending through said tone arm portion.

16. A tone arm balancing assembly according to claim 8, wherein coupling means are mounted on said tone arm assembly for releasably engaging said tone arm portion with said housing portion.

17. A tone arm balancing assembly according to claim 16, wherein said coupling means comprises a locking ring rotatably mounted on an enlarged end of said tone arm portion, said ring having threads formed along an internal surface portion thereof, said coupling means further comprises a hollow attachment member fixedly attached to said housing portion and including threads formed on an outer surface of an end portion confronting said tone arm portion, with said locking ring member engaging said threaded portion of said hollow attachment assembly to engage said tone arm portion to said housing portion.

18. A tone arm balancing assembly according to claim 17, wherein said enlarged end of said tone arm portion includes a radially outwardly directed flange, and said locking ring member includes a radially inwardly directed flange, said radially outwardly directed flange portion of said enlarged end engaging said radially inwardly directed flange of said locking ring, thereby retaining said locking ring on said tone arm portion.

19. A tone arm balancing assembly according to claim 8, wherein said housing portion includes a hollow, cup-shaped end member and an attached sleeve-shaped body member, forming a chamber extending longitudinally through said housing portion.

20. A tone arm balancing assembly according to claim 19, wherein said support assembly includes a vertically directed, cup-shaped end portion extending into said chamber formed within said housing portion with a silicone-like fluid filling a portion of said cup-shaped end portion of said support assembly.

21. A tone arm balancing assembly according to claim 20, wherein said unipivot bearing means comprises a vertically extending pivot pin assembly attached to said cup-shaped end portion of said housing portion and extending into said cup-shaped end portion of said support assembly, said pivot pin assembly having a tapered end portion pivotally engaging a recess formed in an end surface of said cup-shaped end portion.

22. A tone arm balancing assembly according to claim 21, wherein said pivot pin assembly includes a support pin member fixedly attached to said cup-shaped end portion of said housing portion and a tapered pivot pin having a cylindrical end portion extending into a cylindrically-shaped end portion of said support pin.

23. A tone arm balancing assembly according to claim 20, wherein the point of content between said pivot pin assembly and said recess coincides with the center of gravity of said tone arm subassembly.

24. A tone arm balancing assembly according to claim 8, wherein said housing portion includes a cylindrically-shaped outer surface, with said tone arm portion and said balancing arm portion extending substantially perpendicularly from said outer surface and spaced 1800 from one another as measured about the circumference of said outer surface of said housing portion.

35. A tone arm balancing assembly according to claim 8, wherein lateral balancing means extend outwardly from opposite sides of said tone arm sub-assembly for generating restoring forces which tend to resist lateral pivoting movement of said tone arm sub-assembly.

25. A tone arm balancing assembly according to claim 25, wherein said lateral balancing means comprises a pair of threaded shaft members extending from said housing portion on opposite sides of the longitudinal axis of said tone arm subassembly, with each shaft supporting a counterweight mounted thereon, each of said threaded shaft members forming an angle with both said tone arm portion and said balancing arm portion, with a common center of gravity for said pair of threaded shafts and respective counterweight assemblies located in a horizontal plane positioned vertically beneath a horizontal plane extending through the longitudinal axis of said tone arm sub-assembly when in a rest position.

27. A tone arm balancing assembly according to claim 8, wherein a first portion of signal wire having a first gage extends from said cartridge through said tone arm portion of said tone arm sub-assembly, and a second portion of signal wire having a second, higher gage extends from said tone arm portion, through said housing portion and into contact with said support assembly.

28. A tone arm balancing assembly according to claim 27, wherein said first portion of said signal wire is formed by wire having a gage value of substantially 30, said second portion of said signal wire is formed by Litz-type wire having a gage value of substantially 44.

29. A tone arm balancing assembly according to claim 26, wherein each of said threaded shafts forms a substantially perpendicular angle with said tone arm portion and said balancing arm portion.

30. A tone arm balancing assembly according to claim 25, wherein each threaded shaft and respective counterweight assembly mounted thereon has a center of gravity intersecting an imaginary vertical plane extending through said tone arm sub-assembly, said imaginary vertical plane extending substantially parallel to a longitudinal axis of said stylus and perpendicular to the stylus cantilever.

31. A tone arm balancing assembly according to claim 26, wherein each threaded shaft and counterweight assembly mounted thereon has a center of gravity intersecting an imaginary vertical plane extending through said tone arm subassembly, said imaginary vertical plane being displaced in a clockwise direction by an angle of substantially 230 as compared to a further imaginary vertical plane extending perpendicular to a longitudinal axis through said tone arm subassembly.

32. A balancing assembly according to claim 8, wherein said support assembly includes a substantially straight support shaft extending in a vertically downward direction from said housing portion, said support assembly further includes a base plate fixedly mounted on said phonograph assembly frame and formed with an elongated slot sufficient in size to allow said support shaft to extend therethrough.

33. A tone arm balancing assembly according to claim 32, wherein said support assembly further includes a slide member surrounding said shaft and arranged on a side of said base plate remotely positioned from said housing portion, said support assembly further includes a mounting block assembly slidably mounted on said base plate and fixedly attached to said slide member, wherein said mounting block and slide members overlap opposite sides of said elongated slot.

34. A tone arm balancing assembly according to claim 33, wherein said mounting block assembly includes a cavity having a clamping block slidably disposed therein, said cavity and said clamping block having confronting semicylindrical surface portions forming an aperture of a size sufficient to allow said support shaft to extend through said mounting block, said mounting block further includes engagement means for biasing said confronting semi-cylindrical surface portions into frictional contact with said support shaft.

35. A tone arm balancing assembly according to claim 34, wherein said engagement means comprises a set screw extending through an opening in said mounting block into contact with said slidable clamping block whereby rotation of said set screw exerts a force for pressing said clamping block into frictional with said support shaft.

36. A tone arm balancing assembly according to claim 35, wherein said clamping block is formed of a nylon-like material.

37. A tone arm balancing assembly according to claim 35, wherein disengagement means are arranged between a side wall of said cavity and said clamping block for pressing said clamping block out of contact with said support shaft upon withdrawal of said set screw.

38. A tone arm balancing assembly according to claim 37, wherein said disengagement means comprises at least one spring compressed between said cavity side wall and said clamping block.

39. A tone arm balancing assembly according to claim 33, wherein said mounting block includes a threaded bore of a size sufficient to receive a threaded pin member mounted in a support flange extending from said base plate, whereby selective rotation of said pin member serves to alter the position of said mounting block and slide member relative to said base plate.

40. A tone arm balancing assembly according to claim 8, wherein a carrier assembly at least partially encloses said balancing arm portion, said carrier assembly supporting a hollow counterweight assembly for joint movement therewith, said carrier assembly including drive means engaging said balancing arm portion for selectively altering the position of said carrier assembly and counterweight without altering the position of the center of gravity of said counterweight relative to a longitudinal axis through said balancing arm portion.

41. A tone arm balancing assembly according to claim 40, wherein an indexing cursor is slidably mounted on a portion of said balancing arm remotely positioned from said housing assembly.

42. A tone arm balancing assembly according to claim 40, wherein said balancing arm portion is removably attached to a mounting shoe fixedly attached to said housing portion, said balancing arm portion having a substantially rectangular cross-sectional configuration.

43. A tone arm balancing assembly according to claim 42, wherein said carrier assembly includes a hub portion completely surrounding a first portion of said balancing arm and a U-shaped sleeve portion partially surrounding a second portion of said balancing arm, said hub portion including a groove of sufficient size to receive a ring of energy absorbing material extending in a radially outwardly direction between said hub portion and said counterweight assembly.

44. A tone arm balancing assembly according to claim 43, wherein said radially extending ring is formed of a material sold under the tradename of Sorbothane.

45. A tone arm balancing assembly according to claim 43, wherein said drive means comprises a pinion gear rotatably supported between opposite legs of said U-shaped sleeve portion, said pinion gear contacting a relatively fixed rack gear formed in a vertically lower surface of said balancing arm portion, said drive means further comprises a handle attached to said pinion gear for joint rotation, whereby rotation of said handle and pinion gear causes said carrier assembly to move in a longitudinal direction along said relatively fixed rack gear.

46. A tone arm balancing assembly according to claim 8, wherein a holder assembly is fixedly attached to said support assembly and extends substantially parallel to said tone arm sub assembly when in a rest position.

47. A tone arm balancing assembly according to claim 46, wherein anti-skate means are attached to said holder assembly and said tone arm sub-assembly for maintaining a predetermined lateral force on the tone arm supported stylus.

48. A tone arm balancing assembly according to claim 47, wherein said anti-skate means comprises a bearing holder extending outwardly from said holder assembly, said bearing holder having a cup-shaped end portion of sufficient size to receive a ball bearing assembly pressed therein, said anti-skate means further comprises an alignment collar assembly attached to said ball bearing assembly via an attachment screw extending therebetween, said alignment collar assembly including a first pin extending in a substantially vertical direction from said collar and a second pin extending in a substantially horizontal direction from said collar, with a thread-like material extending between a portion of said first pin and a portion of said tone arm sub-assembly located adjacent said balancing arm portion, said anti-skate means further comprises a counterweight mounted on said second pin.

49. A tone arm balancing assembly according to claim 48, wherein said thread-like material extends substantially within a horizontal plane intersecting the pivot point of said bearing means when said tone arm sub-assembly is pivoted a maximum distance from an initial rest position, thereby preventing the tone arm sub-assembly from twisting about said support assembly.

50. A removable counterweight assembly for applying a predetermined tracking force to a pivotally mounted tone arm, and comprising:~ a balancing arm removably attached to a housing supporting said pivotally mounted tone arm, said balancing arm supporting an adjustable carrier assembly having a counterweight mounted thereon, said carrier assembly including drive means engaging said balancing arm for selectively altering the position of said carrier assembly and counterweight along said balancing arm without rotating said counterweight and thereby possibly altering the position of the counterweight center of gravity relative to a longitudinal axis through said balancing arm.

51. A removable counterweight assembly according to claim 50, wherein an indexing cursor is slidably mounted on a portion of said balancing arm remotely spaced from said housing.

52. A removable counterweight assembly according to claim 50, wherein a mounting shoe fixedly attached to said housing includes a substantially T-shaped pocket corresponding in size and shape to a substantially T-shaped flange extending from said balancing arm, whereby insertion of said flange into said pocket serves to removably attach said balancing arm to said housing.

53. A removable counterweight assembly according to claim 50, wherein said carrier assembly includes a hub portion completely enclosing a portion of said balancing arm and a substantially U-shaped sleeve portion partially enclosing a further portion of said balancing arm, said hub portion including a groove of sufficient size to receive a ring of energy absorbing material which contacts and provides the sole support for said counterweight.

54. A removeable counterweight assembly according to claim 53, wherein said energy absorbing ring is formed of Sorbothane.

55. A removeable counterweight assembly according to claim 53, wherein said drive means comprises a pinion gear rotatably supported between said U-shaped sleeve portion, said pinion gear meshing with a rack gear formed in a vertically bottom surface of said balancing arm, said drive means further comprises a control handle attached to said pinion gear for joint rotation, wherein rotation of said pinion gear causes said carrier assembly and attached counterweight to move relative to said fixed rack gear, to alter the tracking force acting on the pivotable tone arm.

56. A method of installing a pivoting tone arm and associated support assembly on a turntable support assembly such that a stylus mounted on said tone arm is properly aligned relative to revolving turntable, comprising the following steps: fixedly attaching a tone arm support assembly base plate to a surface of said turntable support assembly, pivoting said tone arm into vertical alignment with an alignment nipple removably mounted on a spindle extending from the turntable; and adjusting the position of said tone arm support assembly relative to said base plate until a designated opening in a tone arm headshell is vertically aligned with said nipple.

57. A method according to claim 56, including the step of lowering said tone arm until said nipple protrudes through said designated opening to ensure proper alignment of said tone arm with said spindle.

58. A method according to claim 56, including the step of removing said pivoting tone arm from said support assembly and positioning an alignment fixture such that a boss extending from the alignment fixture protrudes through a further designated opening in the headshell.

59. A method according to claim 58, including the step of aligning a pick-up cartridge on said headshell in a position such that a cross hairs formed on transparent plate pivotally attached to said alignment fixture is aligned with a stylus tip protruding from said pick-up cartridge, and further aligning said pick-up cartridge such that a stylus cantilever coincides with a vertical plane extending through an elongated mark formed on said transparent plate.