US2418617A

US2418617A - Pickup device of sound-reproducing machines

Info

Publication number: US2418617A
Application number: US635204A
Authority: US
Inventors: Bessire Jean-Jacques
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-12-15
Filing date: 1945-12-15
Publication date: 1947-04-08
Anticipated expiration: 1964-04-08

Description

April 8, 1947.

JEAN-JACQQES BESSIRE PICK-UP DEVICE OF SOUND REBRODUCING MACHINES Filed Deb. 15, 1945 i/J ATTORNEY Patented Apr. 8, 1947 PICKUP DEVICE OF SOUND-REPRODUCING MACHINES Jean-Jacques Bessire, Bic], Switzerland Application December 15, 1945, Serial No. 635,204

This invention relates to improvements in pickup devices of sound reproducing machines, particularly of the piezo-electric type and the main object thereof is to provide a pick-up having a permanent stylus and allowing to play phonograph records with high fidelity of reproduction and substantially without extraneous surface Claims. (Cl. 179-100. 11)

R The stylus may have a stem which is flattened noise and other sound disturbing influencics experienced with hitherto known pick-up devices.

Another object of the invention is to provide between the stylus and the piezileelefifiric Crystal a resilient intermediate means by which the vibrations of the stylus are thus transmitted upon the piezo-electric crystal that the latter is less moved out of its steady position than in hitherto i known pick-up devices, provided an equal torsion of the vibratory systems. By the interposition of the resilient means in the vibratory systom the inertness of the latter will be reduced and, therefore, the weight of the pick-up may be diminished What contributes to eliminate the surface noise and to diminish the wear and tear on the record.

A further object of the invention is to provide in combination with said pick-up a permanent stylus which carries a member for damping the resonance peaks of the stylus vibrations. For this purpose it has already been proposed to connect the stylus or stylus holder by means of an elastic member with the frame of the pick-up. However, this damping device includes the disadvantage that middle and low frequencies are damped as well and, therefore, the reproduction of deep tones is unfavorably afiected. The damping member according to the invention is resiliently mounted on the stylus and has a freely extending circumferencaso that the natural oscillations of the vibratory system are reduced without increasing the rigidity of the latter. lAt least the portionof the member which is adjoining to the stylus must be resilient, so that the other portion of the member is thereby resiliently connected with the stylus. However, the damping member may be completely made of an elastic material and, for instance, may be constituted by a small rubber disc.

Still another object of the invention is to pro- 'vide in combination with the above-cited pick-up I on two opposite sides over a predetermined length so as to be formed there to a. thin band which besides may be bent through a predetermined angle on the broad side of the band.

Still a further object of the invention is to provide in combination with the above-cited pickup having a delicate permanent stylus referably with a record engaging tip portion of precious stone, a movable supporting and protective member which is adapted to occupy automatically in the pick-up, when the same is lifted off the record, a closed position wherein it covers the jewel point of the stylus against the record. When the pick-up is lowered again upon the record, the protective member will be placed in closed position upon the record, thus supporting the pick-up, and will then be moved relative to the pick-up by the rotation of the record, to the effect that the jewel point will become uncovered and will be lowered together with the pick-up into engaging position on the record without any shock. Preferably the supporting and protective member is rotatably mounted on the pick-up and its cylindrical supporting surface is provided with an elastic protective layer,

These and other objects and features of the invention will appear from the following detailed description of one specific embodiment thereof illustrated in the accompanying drawing, in which Fig. 1 is a sectional elevation of the pick-up with the supporting and protective member in closed position.

Fig. 2 shows a vertical section through the pick-up with the supporting andprotectivememher in opened position.

Fig. 3 shows a horizontal section through the pick-up, along line 3-3 in Fig. 2, and

Fig. 4. is a cross section through the stylus, along line 44 in Fig. 2.

The drawing shows the end portion l of a'hollow, downwardly open pick-up arm of a not illustrated sound reproducing machine. In the casing formed by this end portion l is a pick-up head 2 mounted by means of screws '3. The pickup head 2 contains a piezo-electric crystal 4, a stylus holder 5 and a permanent stylus E which protrudes downwardly from the head 2. The

stylus holder 5 consists of a shaft which is horizontally journalled in the head 2 and has formed a middle portion with a downwardly directed threaded hole wherein the upper threaded end of the stylus 6 is screwed. The shaft 5 is connected with the frame I of the piezo-electric crystal A by an intermediate tapered shaft por tion 8 having a substantially smaller diameter than the shaft so as to be subjected to a very slight resilient torsion when transmitting the vibrations of the stylus 6 upon the piezo-electric crystal 4. The arrangement of this intermediate resilient shaft portion 8 prevents the very brittle crystal 4 from being submitted to dangerous stresses which could damage the same, caused by intense vibrations of the stylus 6. Thereby, the crystal is less moved out of its steady position than in hithertoknown pick-up devices, provided an equal torsion of the vibratory systems, without impairing the reproduction of the sound. The lnertness of the Vibrating system is reduced and, therefore, the weight of the pick-up may be diminished. The stylus 6 extends through a downwardly directed hole 9 of the pick-up head 2 and carries on its cylindrical stem within the hole 9 an annular disc It! made of soft rubber, which is a little smaller in diameter than the hole 9, so that its circumference is freelyextending. If the frequencies of the vibratory system are low, the rubber disc as a whole participates in the vibrations without being perceptibly stressed and deformed in the portions adjoining to the stem by the vibrations. With increasing frequency of the vibrations the disc portions remote from the stylus stem remain more and more stationary, while the disc portions adjoining to the stem elastically participate in the vibrations of the stylus, whereby a damping of the vibrations is effected. It follows from experiments that up to the frequency of 10,000 Hz. a practically straight characteristic line is obtained. Instead of being completely made of soft elastic material the damping disc could comprise a rigid ring which has a free circumference and is resiliently connected with the stylus stem by a soft elastic annular member. In any case the natural oscillations of the vibratory system will be reduced without increasing the rigidity of the latter. I

The stylus has a lower stem portion II which is flattened on two opposite sides over a predetermined length so as to be formed there to a thin band I i which is seen in Fig. 2 from the narrow side and in Fig. 4 from the broad side. The thin band H ends in a socket 52 wherein is fixed a point i3 of precious stone, for instance sapphire. The thin band i l is bent in its upper portion across the broad side thereof through an angle of about 30 to the vertical axis of the stylus stem so that the groove engaging jewel point l3 can resiliently yield in the vertical tangential plane of the groove engaged for eliminating the pinch effect as far as possible. In order to avoid torsion stresses in the. thin band it the bent portion thereof and the jewelpoint l3 are coaxial. The stylus 6 is adapted to damp the vertical motion of the pickup caused by the variations in the depth of the groove bed. Experiments made with the described permanent stylus have shown that by this stylus in combination with the pick-up described, there are obtained: The elimination of the surface noise in playing records, and thus a purer reproduction, an improvement of the stylus point lead on the groove bed, and a diminution of the wear and tear on the record. 7

On two screws I screwed into the lateral sides of the pick-up head 2 is rotatably mounted a drum sector-like cover member l5 having a U-shaped cross section with an inner radius which is. slightly longer than the distanceof the stylus point [3 from the center of rotation of the cover member l5. The cover member i5 is thus adapted to occupy a position wherein it covers and protects the jewel point I3 from below (Fig. 1). As soon as the pick-up is lifted off the record IS the member l5is automatically brought into' this protecting position by the action of a coil spring I! which is located on one of the screws 14 and engages the member IS in closing direction. When the pick-up is lowered again upon the record l6 at first the cover member l5 will contact with the record in order to support the pick-up and to protect the delicate jewel point [3 7 from damage which could be caused by shocks.

turns the same upward into the open position wherein the cover member only slightly contacts the record along the rear edge of the drum, while the stylus point [3 gets thereby uncovered and cautiously lowered upon the record 16 (Fig. 2). The described cover member I5 protects the stylus 6 also when the pick-up 2 is not in use, for

- instance on transports.

It is obviou that various changesand modifications may be made in the details of construction of the above specifically described embodiment of this invention without departing from the general spirit thereof as set forth in the following claims.

What I claim is:

1. A pick-up for sound reproducing machines comprising in a casing in combination a piezoelectric crystal, a rotatable stylus holder in axial connexion with said crystal, a permanent stylus fixed to said holder and having a record engaging point of delicate material, an intermediate resilient means interposed in the vibratory system defined by said crystal, holder and stylus, a damping member mounted on said stylus and having a freely extending circumference, said damping member consisting of resilient material at least in the zone adjoining to said stylus and being adapted to damp the resonance peaks of the stylus vibrations, and a protective member movably mounted insaid casing and adapted to" from the record.

2. A pick-up for sound reproducing machines comprising in a casing in combination a piezoelectric crystal, a rotatable stylus holder in axial connexion with said crystal, a permanent stylus fixed to said holder and having a record engaging point of delicate material, an intermediate resilient means interposed in the vibratory system defined by said crystal, holder and stylus, a'damping member mountedon said stylus and having a freely extending circumference, said clamping member consisting of resilient material at least in the zone adjoining to 'saidstylus and being adapted to damp the resonance peaks of the stylus vibrations, and a protective member movably mounted in said casing and adapted to occupy a closed position'wherein said protective I comprising in a casing in combination a piezoelectric crystal, a rotatable stylus holder in axial connexion with said crystal, a permanent stylus fixed to said holder and having a record engaging point of precious stone, the stem of said stylus being resilient in the vertical-tangential plane of the record groove engaged, for reducing the pinch effect, an intermediate resilient means interposed in the vibratory system defined by said crystal, holder and stylus, a damping member mounted on said stylus and having a freely extending circumference, said damping member consisting of resilient material at least in the zone adjoining to said stylus and being adapted to damp the resonance peaks of the stylus vibrations, and a spring actuated protective member movably mounted in said casing and adapted, upon disengagement of said stylus point from the record, to occupy automatically a closed position, for covering said delicate stylus and damping member against the record, and adapted to be moved by the moving record into an open position, for enabling said stylus point to engage the record without shock.

l. A pick-up for sound reproducing machines comprising in a casing in combination a piezoelectric crystal, a rotatable stylus holder in axial connexion with said crystal, a permanent stylus fixed to said holder and having a record engaging point of precious stone, the stem of said stylus being resilient in the vertical-tangential plane of the record groove engaged, for reducing the pinch effect, an intermediate resilient means interposed in the vibratory system defined by said crystal, holder and stylus, a damping member mounted on said stylus and having a freely extending circumference, said damping member consisting of resilient material at least in the zone adjoining to said stylus and being adapted to damp the resonance peaks of the stylus vibrations, a protective member rotatably mounted in said casing and adapted to cover in closed po sition said delicate stylus point and damping member against the record, a spring acting upon said protective member in closing direction, and a record contacting surface provided on said protective member, for allowing the moving record to rotate said protective member by friction against the action of said spring into open position, whereby said stylus point is enabled to engage the record without shock.

5. A pick-up for sound reproducing machines, comprising in a casing in combination a piezoelectric crystal, a rotatable stylus holder in axial connexion with said crystal, a radially reduced axial portion provided on said stylus holder and resiliently connecting the same with said crystal, a, permanent stylus fixed to said holder and having a record engaging point of precious stone, the stem of said stylus being partly formed to a bent band so as to be resilient in the verticaltangential plane of the record groove engaged, for reducing the pinch effect, a resilient damping member mounted on said stylus and having a freely extending circumference, said damping member being constituted by a rubber disc and adapted to damp the resonance peaks of the stylus vibrations, a drum sector-like protective member rotatably mounted in said casing and adapted to occupy automatically a closing posi tion wherein said protective member covers said delicate stylus and clamping member against the record, upon disengagement of said stylus point from the record, a spring acting upon said protective member in closing direction, and a record contacting elastic layer forming the cylindrical surface of said drum sector-like member, for allowing the moving record to rotate said protective member by friction against the action of said spring into open position, whereby said stylus point is enabled to engage the record without shock.

JEAN-JACQUES BESSIRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number