GB2049259A

GB2049259A - Gramophone pick up arm assembly

Info

Publication number: GB2049259A
Application number: GB8013532A
Authority: GB
Original assignee: MICHELL ENG Ltd J
Current assignee: MICHELL ENG Ltd J
Priority date: 1979-04-27
Filing date: 1980-04-24
Publication date: 1980-12-17

Abstract

The assembly comprises a pickup arm 3 mounted on a carrier 4 which has a needle pivot 7 coacting with a bearing block 8. The assembly is counterbalanced by two masses 10 and 11 secured to a carrier 12 which may be moved along an arm 13 to adjust the tracking mass. Each mass 10 and 11 is further movable in a direction transverse to arm 13 to provide adjustment of head "leaning". The arrangement provides low inertia by siting the main counterbalance masses close to, and below, the plane of the pivot. <IMAGE>

Description

SPECIFICATION Improvements in pick-up arm assemblies for gramophones This invention relates to pick-up arm assemblies of precision construction for use with high quality gramophone turntable units and seeks to provide a pick-arm assembly of the single pivot point type so-called 'unipivot' arm, in which the counterbalance weights are better distributed about the pivot to provide a stabilising effect and to lower the frequency of oscillation According to this invention there is provided a pick-up assembly comprising a pickup arm carrier or 'helmet' pivotally mounted on a base support through a vertically disposed needle pivot bearing, the arm carrier having a longitudinally extending arm adapted to support a pick-up head and, disposed oppositely the arm on the helmet, a counterbalance weight assembly with the centre of mass located below the needle pivot bearing point and with counterbalance masses disposed to each side of a vertical plane through the pivot and arm.

In such an arrangement by splitting the total required counterbalance mass and positioning parts thereof equally to either side of the vertical plane through the pivot and on the arm longitudinal axis, better stability and lower oscillation frequency of the arm is obtained and in addition it is also possible to provide a simple vertical height adjustment of the alignment of the arm by raising or lowering the pivot on the base support. The arrangement enables large counterbalancing masses to be positioned close to the pivot with attendant advantages.

A further advantage resides in the fact that the pivot point for the arm may be arranged to lie on the same horizontal plane as the stylus, thereby providing less movement of mass and thus lower inertia of the parts forming the pick-up. The two main counterbalancing masses are preferably secured in a movable manner on an arm which extends from the arm carrier in a direction opposite to the pick-up arm and from a point which lies below the pivot.

By making the two main counterbalance masses movable in a direction parallel to the arm axis adjustment for various tracking masses is effected, and by making each mass further movable laterally adjustment of the "leaning" of the head is easily made without affecting tracking weight calibration.

An embodiment according to the invention is shown by way of an example in conjunction with the accompanying drawing showing a perspective view of the arm carrier and base support assembly.

Referring to the drawings, these show a base mount 1 which is adapted to be secured to the base board of a turntable unit and carrying a base support 2 on which the pickup arm and pivot assembly are mounted. The pick-up arm 3 includes at one end (not shown) the pick-up cartridge and head shell with the other end secured to an arm carrier or helmet 4. The helmet includes a cap 5 which screw connects therewith and which includes a depending spigot 6 having a needle pivot 7 coacting with a bearing block 8 carried by the base support 2.

The arm carrier also includes a counterbalance weight assembly 9 which is effectively disposed below the pivot point and oppositely to the arm 3 and which comprises two main counterbalance masses 10 and 11 fastened on opposed sides of a carrier 12 which is itself slidably mounted on a shaft 13 secured to the helmet 4. An adjustment knob 14 effects movement of the counterbalance weight assembly 9 on the shaft 13 by screw action towards or away from the helmet thereby providing adjustment of the effective mass acting about the pivot. The bearing block 8 is carried in a screw threading and by rotation of knurled ring 15 this block can be moved upwardly or downwardly thereby providing height adjustment of the pick-up arm assembly as a whole. A securing means 16 provides for locking of the knurled ring 15.

Anti-skating control may be provided by the usual form of small counterbalance weight 19 which engages the stud 17 through a thin filament 20.

The wires from the cartridge are brought out from the pick-up arm inside the helmet 4 and are taken through a small tube to exit at a point below the pivot 7 and thus the centre of gravity is lower.

Each mass 10 is movable transversely to the shaft 13 individually by virtue of their screw connection with stub shafts on the carrier 12. This means provides for lateral balancing of the head, i.e. leaning may be corrected.

An arm rest and pick-up lift assembly 18 may be provided.

1. A gramophone pick-up assembly comprising a pick-up arm carrier pivotally mounted on a base support through a vertically disposed needle pivot bearing, the arm carrier having a longitudinally extending pickup arm adapted to support a pick-up head and, disposed oppositely the arm on the helmet, a counterbalance weight assembly with the centre of mass located below the needle pivot bearing point and with counterbalance masses disposed to each side of a vertical plane through the pivot arm.

2. A pick-up assembly according to Claim 1, wherein the pivot is vertically adjustable with respect to the base support.

3. A pick-up assembly according to Claim

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in pick-up arm assemblies for gramophones This invention relates to pick-up arm assemblies of precision construction for use with high quality gramophone turntable units and seeks to provide a pick-arm assembly of the single pivot point type so-called 'unipivot' arm, in which the counterbalance weights are better distributed about the pivot to provide a stabilising effect and to lower the frequency of oscillation According to this invention there is provided a pick-up assembly comprising a pickup arm carrier or 'helmet' pivotally mounted on a base support through a vertically disposed needle pivot bearing, the arm carrier having a longitudinally extending arm adapted to support a pick-up head and, disposed oppositely the arm on the helmet, a counterbalance weight assembly with the centre of mass located below the needle pivot bearing point and with counterbalance masses disposed to each side of a vertical plane through the pivot and arm. In such an arrangement by splitting the total required counterbalance mass and positioning parts thereof equally to either side of the vertical plane through the pivot and on the arm longitudinal axis, better stability and lower oscillation frequency of the arm is obtained and in addition it is also possible to provide a simple vertical height adjustment of the alignment of the arm by raising or lowering the pivot on the base support. The arrangement enables large counterbalancing masses to be positioned close to the pivot with attendant advantages. A further advantage resides in the fact that the pivot point for the arm may be arranged to lie on the same horizontal plane as the stylus, thereby providing less movement of mass and thus lower inertia of the parts forming the pick-up. The two main counterbalancing masses are preferably secured in a movable manner on an arm which extends from the arm carrier in a direction opposite to the pick-up arm and from a point which lies below the pivot. By making the two main counterbalance masses movable in a direction parallel to the arm axis adjustment for various tracking masses is effected, and by making each mass further movable laterally adjustment of the "leaning" of the head is easily made without affecting tracking weight calibration. An embodiment according to the invention is shown by way of an example in conjunction with the accompanying drawing showing a perspective view of the arm carrier and base support assembly. Referring to the drawings, these show a base mount 1 which is adapted to be secured to the base board of a turntable unit and carrying a base support 2 on which the pickup arm and pivot assembly are mounted. The pick-up arm 3 includes at one end (not shown) the pick-up cartridge and head shell with the other end secured to an arm carrier or helmet 4. The helmet includes a cap 5 which screw connects therewith and which includes a depending spigot 6 having a needle pivot 7 coacting with a bearing block 8 carried by the base support 2. The arm carrier also includes a counterbalance weight assembly 9 which is effectively disposed below the pivot point and oppositely to the arm 3 and which comprises two main counterbalance masses 10 and 11 fastened on opposed sides of a carrier 12 which is itself slidably mounted on a shaft 13 secured to the helmet 4. An adjustment knob 14 effects movement of the counterbalance weight assembly 9 on the shaft 13 by screw action towards or away from the helmet thereby providing adjustment of the effective mass acting about the pivot. The bearing block 8 is carried in a screw threading and by rotation of knurled ring 15 this block can be moved upwardly or downwardly thereby providing height adjustment of the pick-up arm assembly as a whole. A securing means 16 provides for locking of the knurled ring 15. Anti-skating control may be provided by the usual form of small counterbalance weight 19 which engages the stud 17 through a thin filament 20. The wires from the cartridge are brought out from the pick-up arm inside the helmet 4 and are taken through a small tube to exit at a point below the pivot 7 and thus the centre of gravity is lower. Each mass 10 is movable transversely to the shaft 13 individually by virtue of their screw connection with stub shafts on the carrier 12. This means provides for lateral balancing of the head, i.e. leaning may be corrected. An arm rest and pick-up lift assembly 18 may be provided. CLAIMS

3. A pick-up assembly according to Claim 1 or 2, wherein the pivot point lies in the same horizontal plane as the tip of the stylus.

4. A pick-up assembly according to any preceding Claim, wherein the counterbalance masses are mounted to be movable longitudinal of the pick-up arm on an arm extending from the arm carrier and opposite to the pick up arm, the arm being secured to the carrier at a point below the pivot.

5. A pick-up assembly according to any preceding Claim, wherein one, or both, masses are movable in a lateral direction relative to the pick-up arm.

6. A gramophone pick-up arm assembly constructed and arranged to function substantially as herein described with reference to the accompanying drawings.