US2625400A

US2625400A - Phonograph tone arm

Info

Publication number: US2625400A
Application number: US45062A
Authority: US
Inventors: Hermann E F C Lingenbrink
Original assignee: Philco Ford Corp
Current assignee: Space Systems Loral LLC
Priority date: 1948-08-19
Filing date: 1948-08-19
Publication date: 1953-01-13
Anticipated expiration: 1970-01-13

Description

H. E. F. c. LINGENBRINK 2,625,400

PHONOGRAPH TONE ARM Filed Aug. 19, 1948 ACf/Vff Jan. 13, 1953 Patented Jan. 13, 1953 PHON GRAPH TONE ARM Hermann E. F. C. Lingenbrink, Hilltown, Pa., as-

signor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application August 19, 194s, seia1N0.45,062

7 Claims.

The present invention relates to phonograph apparatus and, particularly, to phonograph tonearms. More specifically, the invention has to do with a novel and improved 'arrangement for mounting the tone-arm of a phonograph.

It is generally known in the art that best sound reproducing results are obtained when the needle engages the record with substantially constant pressure throughout the entire playing time. In many cases, known arrangements employed for that purpose are objectionable, chiefly, because of the complicated structure land intricate assembly which they necessitate. According to common practice, the tone-arm usually comprises an elongated channeled member. One end of this tone-arm member (generally called the head portion) is designed to enclose the transducer or pickup unit, whereas the other end portion of said member (generally c-alled the heel portion) is designed to enclose the mounting farrangement. This mounting arrangement must provide for swinging movement of the tone-arm in planes both parallel and perpendicular to the playing surface of the record and, furthermore, must be such that it will not react on the tone- -arm to cause substantial variation in the pressure with which the needle engages the record. Because of the necessarily limited space available for association of the mounting arrangement with the tone-arm heel portion, the provision of a reasonably simple assemblage which is capable of producing the above-mentioned desirable results, meets with troublesome problems. These problems are enhanced by the fact that, in most instances, it is necessary to provide the tone-arm heel portion with accurately balanced means for counterbal-ancing the tone-arm in order to obtain the desired needle-pressure. Furthermore, the use of recently developed lightweight pickups which are adapted to operate at exceedingly low needle-pressure, that is, at a pressure of the order of 5 grams, h-as accentuated the problems of devising simplified adequate means for mounting the tone-arm provided with a pickup of that kind.

It is therefore the primary object of this invention to provide a tone-arm mounting which permits operation at substantially uniform low needle-pressure and, yet, makes it possible to overcome the objections and diiiculties above l:and by the ease with which lit .is asmbled and attached to the tone-arm. The parts are so constructed that they ca -n be conveniently assembled in a unit and, as such, can be readily `and quickly mounted in the tone--arm heel portion with the aid of simple fastening elements.

It is also `an object of the invention to eliminate the necessity of providing the tone-arm walls With bearings for supporting the tone-arm pivots, and to do aWay with the use of special means for mounting the counterweight. For these purposes, the tone-arm mounting unit, in itself, incorporates the necessary pivotal elements and serves to -aix the counterweight within the tone-arm heel portion. An important advantage gained by the used of an arrangement of this kind, is that the only means required to mount the various parts in the tone-arm heel portion, are theffew securing elements employed to attach the arrangement to said portion.

Another object of the invention is to improve the manner in which the desired and substantially constanty needle-pressure is realized. In accordance with this feature of the invention, a counterweight is employed primarily to counteract the natural tendency of the tone-arm to gravit-ate into engagement with the playing sur-V face of the record, and a simple adjustable tensioning means is associated with and included in the mounting unit arrangement to subject the tone-arm to a, regulated yieldable tension which acts on the tone-arm with the required force to obtain the desired needle-pressure. In this manner, it is possible to compensate for variations from the desired manufacturing tolerances and, also, to obtain precisely the needle-pressure with which it is desired to operate.

Still another and more specic objec-t of the invention resides in the provision of an arrangement capable of adequately protecting the needle against injury, and of positively preventing undesirable movements ofv the tone-arm. It frequently happens that the tone-arm is accidentally or otherwisedropped on a surface of the phonograph structure. When this occurs, injury to the needle is likely to follow. Likewise, it frequently happens that the tone-arm, when lifted off :a record and carried toward inoperative p0- sition, is moved beyond its intended position of rest, with the result that injury to the tripping or other mechanism of the phonograph is apt to occur.v The arrangement provided by this invention'issuchdthat it eiectively prevents either of the aboveweventualities. fromkk taking place. Y Thesefand other[objectsl and the manner in which theyae obtained,`will be fully understood from the following description based on the accompanying drawing which illustrates a preferred embodiment of the invention. In the drawing,

Figure 1 is a bottom plan view of a tone-arm heel portion to which the improved mounting arrangement is attached;

Figure 2 is a sectional-elevational view looking in the general direction of arrows 2 2 in Figure 1; and

Figure 3 is a sectional-elevational view looking in the general direction of arrows 3-3 in Figure 2.

Referring more particularly to the drawing, the tone-arm Iil is provided with a recessed heel portion II which receives and houses the tonearm mounting arrangement of the present invention. This arrangement, as shown, basically comprises a mounting bracket I2 and a supporting bracket I 3, which brackets are disposed in substantially parallel relationship and interconnected for relative pivotal movement. This relative pivotal movement is obtained by providing the mounting bracket and the supporting bracket with spaced sets of companion ears I4 and I5 (Figures 2 and 3). 'Ihese ears extend from the side edges of the brackets adjacent one of their end portions, and are so disposed that the ears of one bracket overlap the ears of the other bracket, in the manner clearly illustrated L in Figure 3. The ears are apertured to receive a cross pin i6 which provides the pivotal inter connection between the brackets.

The mounting bracket I2 is rigidly attached to the tone-arm so that the latter pivots with said mounting bracket about the axis of cross pin I6. For that purpose, internally screw-threaded bosses I'I are conveniently provided, at appropriate points, to extend from the inner top sui'- face of the tone-arm heel portion II, and suita able fastening elements I8 pass through apertures in the mounting brackets and are driven in screw-threaded engagement with said bosses. In order to facilitate assembly and, also, to provide for unobstructed relative movement between the brackets, the cross pin IB is freely received in apertured ears I4 and I5. However, excessive displacement of the pin with respect to the ears is prevented by means of protuberances I9 (Figure 1) which are disposed on opposite walls of the recessed heel portion to lie in line with and d adjacent to the ends of the pin, thereby limiting its longitudinal movement in said ears.

The free end portion of the supporting bracket I3 is provided with a right angular-ly disposed shaft 20, a portion of which is shown in the drawing. In practice, this shaft is extended for engagement with bearing means (not shown) which is conveniently provided on the motor board of the phonograph so as to support the tone-arm in operative relationship with respect to a record on the turntable. Thus, the shaft 20 provides for the swinging movement of the tonearm and its mounting arrangement in planes generally parallel to the playing surface of the record supported on the turntable, and the cross pin I6 provides for pivotal movement of said tone-arm and its mounting bracket I2 relatively to the supporting bracket I3, and in planes generally normal to said record surface.

It will be understood that the mentioned swinging and pivotal movements of the tonearm are for the usual purpose of allowing the tone-arm to be brought from an inoperative position of rest to an operative position where the pickup needle engages the record and, also, for the usual purpose of allowing the tone-arm to be brought back to its inoperative position oi rest from an operative position where lthe pickup needle engages the record. When the pickup needle engages the record for its reproduction, it is desirable that the pressure with which the needle bears against the record be predetermined and maintained substantially constant. In accordance with the present invention, means for that purpose is cooperatively associated with the tone-arm and its mounting arrangement.

As more clearly seen in Figure 2 of the drawing, a counterbalancing weight 2l is ixedly retained within the recessed tone-arm heel portion II. The weight 2l has two opposite faces 2Ia and 2lb and, in accordance with the invention, one face 2Ia confronts a surface portion 2Ic of the tone-arm, and the other face 2Ib is formed with a groove 23. Also in accordance with the invention, the mounting bracket I2 which is attached to the tone-arm, has an extension 22 which projects rearwardly from the mounting bracket I2 and enters into the groove 23 provided in the weight. Thus, the bracket extension 22 confronts the face 2lb of the weight so that, in effect, the mentioned surface portion of the tonearm and said extension of the mounting bracket cooperate to clamp the weight in fixed position. A ange 24 which is advantageously provided on the rearward edge of the mounting plate adjacent the mentioned extension, bears on the adjoining surface of the weight and acts to stabilize .said weight. It is important to note that, because the weight is retained in position by the cooperative relationship between parts of the tone-ann heel portion I I and parts of the mounting bracket, the fastening elements I8 for said bracket are all that are needed to mount the weight and bracket assembly within the heel portion.

The weight 2l, in accordance with the invention, serves to counteract the combined weight of the tone-arm and its pickup and, accordingly, prevents the needle from engaging the record with the excessive pressure which said combined weight would impose. In order to obtain the desired needle-pressure, adjustable tensioning means is incorporated in the mounting arrangement to urge the tone-arm in a direction and with the required force to provide the needlepressure with which it is desired to operate. l As shown, this tensioning means takes the form of a coil spring 25 which has one end 26 connected with the supporting bracket I3, and which has the other end 21 connected with a projection 28 extending, at substantially right angle, from the pivoted end portion of the mounting bracketV i2. Thus, the spring acts normally to cause movement of the tone-arm toward and perpendicularly to the playing surface of a record on the turntable, so that the needle engages the record with a pressure commensurate with the force resulting from the tension of the spring. This needle-pressure, in accordance with the invention, is readily adjusted to a predetermined value .by varying the tension of the spring and, for that purpose, one edge of the supporting bracket is provided with a series of notches 29 (see Figure 1 with any one of which the end 26 of the spring may be engaged. Accordingly, the spring may be stretched more or less, depending on its point of connection with the supporting plate, thereby increasing or decreasing the spring tension with a consequent increase or decrease in needlepressure.

Further, in accordance with this invention, means is also incorporated in the mounting arrangement to limit the pivotal movement of the tone-arm perpendicularly to the surface of a record on the turntable. This limited pivotal movement is obtained by providing the brackets I2 and I3 with interengageable stop means which, as more clearly appears in Figure 3, take the form of relatively spaced abutments 30 and 3I arranged on one bracket, and a finger 32 disposed on the other bracket for engagement with said abutments. In the embodiment shown, abutments 30 and 3| are conveniently provided on projection 28 of mounting bracket I2, so that the space between said abutments lies in a plane generally aligned with the plane of the supporting bracket; and finger 32 is located to project from the pivotal end portion of supporting bracket I3 in a plane generally coextensive with the plane of said supporting bracket, so as to extend into the space between the aforementioned abutments. Because of this construction, the tone-arm and its mounting bracket are free to pivot in either direction and relatively to the supporting bracket about the axis of cross pin I6, but the angular displacement of the tonearm and its mounting bracket with respect to the supporting bracket and the turntable, is restricted to the extent allowed by the spacing between abutments 30 and 3l.

By reason of this construction, the needle is effectively prevented from coming in contact with a surface of the phonograph structure, in the event the tone-arm is accidentally or otherwise dropped on such a surface. Also, the tonearm is effectively prevented from being lifted off a record to a level above its resting post (not shown) which is customarily provided on a base plate to maintain the tone-arm in its inoperative position. It Will be understood that by limiting the downward movement of the tone-arm, the needle is protected against the injury which would result should the needle come in abrupt contact with a surface of the phonograph structure. It will also be understood that by limiting the upward movement of the tone-arm, the tonearm is kept from being moved past the level of the resting post, so that the post itself, stops the tone-arm from being swung beyond its intended position of rest. It is pointed out that, in practice, the spacing between abutments 30 and 3| is such that during the playing of a record, when the needle engages the record, the finger 32 is out of contact with said abutments and oats therebetween. In this manner, the abutments do not interfere with the normal operation of the pickup and tone-arm.

From the foregoing description, it will be appreciated that the invention provides an advantageous arrangement by means of Which a phonograph tone-arm may be mounted and supported for proper operation at the desired needlepressure and without the danger of being improperly displaced so as to cause injury to the needle or other parts of the phonograph. Particularly, it will be recognized that the invention makes it possible to assemble, as a unit, the mounting arrangement including the mounting and supporting brackets and their associated elements, which unit may be conveniently aflixed to the tone-arm and utilized to maintain the counterbalancing Weight in position.

I claim:

1- In a DhOnGgl'aph tone-arm mounting ai'- l'angement, a pair of brackets disposed in substantially parallel relationship and intel-conu nected for relative pivotal movement, one bracket having a projection provided with spaced abutments, the space between said abutments lying in a plane generally aligned with the plane of the other bracket, a finger projecting from said other bracket in a plane generally coextensive therewith to extend into the space between the abutments for engagement with the latter so as to restrict the relative pivotal movement of said brackets to the extent afforded by the spacing of said abutments, a rigid supporting shaft connected with one bracket, and tension means'cooperatively disposed between the brackets, and normally urging the other bracket to pivot in one direction with respect to said one bracket, said tension means consisting of a coil spring connected with both brackets, the connection between one bracket and the spring being adjustable to vary the tension of said spring, said adjustable connection between the mentioned one bracket and the spring being provided by means of a series of notches on said one bracket, and the spring being engageable with any one of the notches so as to stretch the spring a greater or lesser extent thereby selectively mcreasing or reducing the tension of the spring.

2. 1n a phonograph apparatus. a tone-arm, a weight in free engagement with a surface portion of the tone-arm and effective to counterbalance the weight of the latter, and a tone-arm mounting arrangement connected with the tonearm and having means engaging said weight and cooperating with said surface portion of the tone-arm to clamp the weight in fixed pos1 t1on, said mounting arrangement including a pair of interconnected brackets to provide two perpendicularly related axes about which the tone-arm may pivot, and tension means cooperatively disy posed between said brackets and urging one bracket to pivot about one of said axes, against the action of the weight, in a direction and with a predetermined force to supply the desired needle pressure.

3. The arrangement set forth in claim 2, in which the brackets are provided with interengageable means to limit the pivotal movement of .the tone-arm about the mentioned one axis.

4. The arrangement set forth in claim 3, in which the interengageable means comprises a pair of relatively spaced abutments provided on one bracket, and a finger disposed on the other bracket to extend between said abutments for engagement therewith.

5. In a phonograph tone-arm mounting arrangement, a pair of brackets disposed in substantially parallel relationship and interconnected for relative pivotal movement, one bracket having a projection provided with spaced abutments, the space between said abutments lying `in a plane generally aligned with the plane of the other bracket, a nger projecting from said other bracket in a plane generally coextensive therewith to extend into the space between the abutments for engagment with the latter so as to restrict the relative pivotal movement of said brackets to the extent afforded by the spacing of said abutments, a rigid supporting shaft connected with one bracket, andwtension means cooperatively disposed between the brackets and normally urging the other bracket to pivot in one direction with respect to said one bracket, said tension means consisting of a stretchable tensioning element connected with both brackets, the connection between one bracket and the tensioning element being adjustable to vary the tension of said elements, said adjustable connection being provided by means of a series of anchoring elements arranged in iixed spaced relationship on said one bracket, the tensioning element being engageable with any one of said anchoring elements, so as to stretch said tensioning element to a greater or lesser extent thereby selectively increasing or reducing the tension of said tensioning element.

6. In a phonograph apparatus, a tone-arm, a counterbalancing weight for the tone-arm, said weight having two opposite faces one of said faces confronting a surface portion ci the tonearm, and a tone-arm mounting arrangement including a pair of pivotally interconnected brackets cooperating with each other to provide two perpendicularly related axes about which the tone-arm may pivot, one of said brackets being attached to the tone-arm and having an extension confronting the other of said opposite faces of the weight, said extension cooperating with said surface portion of the tone-arm to clamp the Weight in fixed position.

7. In a phonograph apparatus, a tone-arm, a counterbalancing weight for the tone-arm, said weight having two opposite faces, one of said faces confronting a surface portion of the tonearm and the other of said faces being formed with a groove, and a tone-arm mounting arrangement includng a pair of pivotally interconnected brackets cooperating With each other to provide two perpendicularly related axes about which the tone-arm may pivot, one of said brackets being attached to the tone-arm and having an extension entering said groove and cooperating with said surface portion of the tonearm to clamp the weight in xed position.

HERMANN E. F. C. LINGENBRINK.

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

UNITED STATES PATENTS Number Name Date 1,881,942 Raber Oct. 11, 1932 2,060,117 Proctor Nov. 10, 1936 2,174,156 Guedon Sept. 26, 1939 2,246,130 Forstrom June 17, 1941 2,331,122 Jones Oct. 5, 1943 2,357,034 Thompson et al. Aug. 29, 1944 2,368,198 Brown et al. Jan. 30, 1945 2,434,033 Cain Jan. 6, 1949 2,475,785 Jensen July 12, 1949 2,545,652 Dann et al Mar. 20, 1951