US2650953A - Method of assembling phonograph translating devices - Google Patents

Description

Sept? 1, 1953 GUNTER, JR 2,650,953

METHOD OF' ASSEMBLING PHONOGRAPH TRANSLATING DEVICES Filed May 3, 1951 J9 4; 25 44 46. .45 0% ENTOR.

1W-xl? ee/ N @QZKM da Patented Sept. 1, 1 953 METHOD OF ASSEMBLIN G PHONOGRAPH TRANSLATING DEVICES Lee Gunter, Jr., Mount Prospect, Ill., assignor to Shure Brothers, Incorporated, Chicago, Ill., a corporation of Illinois Application May 3, 1951, Serial No. 224,410 6 Claims. (Cl. 179-100.41)

This invention relates to a method of assembling phonograph pickup cartridges, more particularly to such a method wherein it is desired to assemble a casing formed in halves, a transducing element, and a phonograph needle chuck into a unitary structure, and itis an object of the invention to provide an improved method of this character.

The phonograph pickup of the subject application is disclosed and claimed in an application of Benjamin B. Bauer, Serial No. 224,339, entitled Phonograph Translating Device, led May 3, 1951, and assigned to the sam-e assignee as the instant invention.

Phonograph pickups of the character indicated comprise a number of relatively small parts, each of which is manufactured to certain specific dimensions, but with a range of permissible tolerance, as is well known. In the assembling process, during which the parts to be assembled are chosen at random, it frequently occurs that the parts selected have dimensions which do not lit together in the best possible manner even though each of these parts has dimensions within the range of tolerance. This occurs because the parts selected have their tolerances all adding in the same sense, for example all positive and by perhaps the maximum amount. In phonograph pickups of the character indicated, it is not only necessary for the parts to t together as the tolerances will permit to form the nal product, but certain parts must also haveprescribed clearances in order that the necessary vibrational movements can occur. It has been found in some instances that parts selected at random and assembled together will produce a pickupin which the necessary clearances are lacking thereby resulting in rejection. Accordingly, it is a further object of the invention to provide an improved method for assembling the parts or a phonograph pickup with parts selected at random and without regard to the sense of the dimensional tolerances wherein the relatively movable parts of the final product have the prescribed clearances.

In carrying out the invention in one form, there is provided in a phonograph translating device including a pair of casing halves held together to form a casing: a pair of resilient members inside of the casing halves and each having an opening therein; a pickup unit including a transducing element held at one end in the opening in the resilient members and a phonograph needle chuck cemented to the transducing element at its other end and in line therewith; and .stop means On the casing halves ,for limiting lateral movements of the needle chuck and transducing element; the method of assembling the device comprising the steps of assembling one end of the transducing element into the opening in the resilient members and the resilient members into the casing halves to form a nal subassembly, disposing the needle chuck at one end in functional relationship to be with the other end of the transducing element and while so disposed holding the needle chuck substantially midway between the stop means and in stressfree relationship with the transducing element, and oementing the needle chuck and the transducing element together while the needle chuck is so disposed.

For a more complete understanding of the invention, reference should be ha-d to the accompanying drawings in which:

Figure 1 is a perspective view of a phonograph pickup cartridge assembled according to the in- Vention;

Fig. 2 is an elevational view of the cartridge shown in Fig. 1 with one casing half removed;

Fig. 3 is a sectional view taken substantially along lines 3-3 of Fig. 2;

Fig. 4 is a perspective view of a subassembly in the method according to the invention;

Fig. 5 is a sectional view taken substantially in the direction of arrows 5-5 of Fig. 4

Fig. 6 is a view taken in substantially the same direction as that of Fig. 5 after a further step in the method according to the invention, and

Figs. '7, 8 and 9 are fragmentary views illustrating various conditions which may arise and their solutions according to the invention.

Referring to the drawings, a pickup 20 assembled according to the invention is shown comprising a cartridge including a pair of casing halves 2| and 22 within which is mounted a pickup element 23 including a transducing element 24, for example, a piezoelectric element, a chuck or transmitting unit 25, and a phonograph needle or stylus 26.

The pickup element is supported within the casing at one end of the piezoelectric elementl 24 by means of rubber or similar material blocks 21 and 23, and the phonograph needle 26 extends outwardly of the casing at the forward end, the piezoelectric element 24, thechuck 25, and the needle 25 comprising a single element or unit mounted in cantilever fashion. Held within the rear of the cartridge are a pair of terminals 29 and 3l which are adapted to be received in suitable sockets on electrical leads in the phonograph pickup arm, and the other ends of the terminals are adapted to be electrically connected to appropriate sides of the piezoelectric element by suitable conductors or straps 32 and 33. The weight of the tone arm and pickup cartridge which is permitted to rest upon the needle 26 when it engages the groove of a phonograph record is supported virtually entirely upon the piezoelectric or transducing element 24 during normal operation. A block of damping material 3D is disposed between the chuck 25 and an abutment on the casing but it is of such size and stiffness that it provides very little if any support for the pickup arm during normal operation. The presence of the block of damping material assists in preventing excessive deflections of the chuck when undue forces are exerted on the pickup arm. Since the piezoelectric element 24 may be quite fragile, it is desirable that the force on the needle26 due to the weight of the tone arm be reduced to as small a value as possible as is consistent with maintaining suncient force at the stylus to assure that the stylus will properly follow the record grooves. The stylus moves laterally to and fro in the record groove thereby deilecting the piezoelectric element 24 and causing an electrical output to be obtained at terminals 29 and 3l.

The casing halves 2l and 22 may be formed of any material having good dimensional stability, such for example as Bakelite and plastic materials or metal, and are held together with the various parts assembled therein by means of rivets or the like 34 and 35. On the outside of each of the casing halves there may be a series of projections 36 and 31, respectively, which are utilized for holding the cartridge to the phonograph tone arm.

Each of the casing halves 2l and 22 is hollowed out to form a space for the active elements of the pickup. A series of serrations or grooves 33 and 39 are provided on the inside of the casing halves for gripping the rubber blocks 21 and 28. The piezoelectric element 24 must be iirmly held between the blocks 21 and 28, but it is undesirable to compress the blocks 21 and 28 beyond a certain amount because the piezoelectric element may be held too tightly. This situation may exist when the dimensions of the various parts are such as to produce a very tight t which condition may arise when the manufacturing tolerances of the parts chosen at random are all in the same sense. Thus, for example, the rubber blocks 21 and 28 may, for a particular pickup, be thicker by the maximum amount of the permissible tolerance, and the walls of the casing halves for this particular pickup may also be thicker by the amount of the permissible tolerance. Under these conditions, if the walls of the casing halves are smooth, that is, the serrations 38 and 39 are eliminated, the rubber blocks 2T and 28 are placed under a much greater compression than they are when the manufacturing tolerances tend in the other or minimum direction, and consequently the piezoelectric element may be hel-d too tightly. it has been found that by utilizing the serrations 38 and 36, the material of the blocks 21 and 26 flows to a certain extent into the serrations, thereby causing much less change in clamping force on the piezoelectric element due to changes in the clamping dimensions.

Each of the rubber blocks 21 and 28 includes an open rectangular groove therein, which grooves lie opposite each other when the rubber blocks are placed together and thereby form a closed rectangular groove within which the rearward end of the piezoelectric element 24 is received. The

piezoelectric element extends downwardly at an angle so that with the chuck 25 and the needle 26 substantially in line therewith, the end of the needle projects outwardly of the pickup and below thereof at the desired point.

The piezoelectric element 24 may be formed of any material having piezoelectric properties and the necessary strength, such as quartz, Rochelle salts or certain ceramic materials, for example. Any shape of piezoelectric element ma be used, the elongated and rectangular crosssectional element shown having been found satisfactory. Other forms of transducers may also be used such, for example, as capacitive, resistive, or magnetic elements which change their propu orties with deformation.

The chuck 25 includes a pair of prongs 4l and 42 which are arranged to lie on the two sides, respectively, of the forward end of the piezoelectric element, the chuck and the piezoelectric element being firmly held together by means of cement i9 or the like. A layer of insulating and/or vibrational isolating material, such as a thin sheet of rubber 43, may be cemented iirmly to the forward end of the piezoelectric element and thus lie between the piezoelectric element and the prongs 4l and 42.

The chuck 25, as is described more completely in the Bauer application referred to hereinbefore, may be formed by taking a tube of the desired material, for example steel or aluminum, of the desired length and flattening one end of it until the two portions of the tube lie against each other, and flattening the other end so as to be within the same plane generally as the first part by leaving a space or slot within which the end of the needle 26 may be received. A hole 44 is provided through the forward part of the chuck for receiving a detent provided on the needle 26. The prongs 4| and 42 preferably are larger at their bases than at their ends to increase their strength and result in a generally trapezoidal groove within which the end of the piezoelectric element is received.

When chuck 25 is cemented to piezoelectric element 24 as described, a relatively rigid structure is formed so that when the needle 26 is engaged within the chuck and the end of the needle is moved back and forth laterally by the record groove, the piezoelectricl element 24 is placed under bending stresses. The casing halves are provided with stops 45 and 46, respectively, against which the edges of the chuck 25 bear so as to limit deflections of the piezoelectric element. lThis is desirable since the piezoelectric element is fragile and cannot be stressed beyond a certain limit without being subject to breakage. The stops 45 and 46 extend inwardly a sufcient distance so that contact therewith is made before the piezoelectric element is subjected to the suiicient stress to cause breakage, allowing, however, sucient clearance between stops and the edges of the chuck necessary for proper operation.

It is essential that the chuck 25 be accurately disposed substantially equidistant from the stops 45 and 46 and remain so after the apparatus is assembled in order that the chuck can move laterally in each direction by the same amount. In this fashion sound is most faithfully reproduced. It has been found that during the manuacturing process the dimensions of the parts due to the permissible tolerances are such that the piezoelectric element may lie at a slight angle relative to the casing instead of being centrally disposed therein or the piezoelectric element may lie slightly offset from the axis of the pickup but parallel thereto.

Ihree possible conditions which may arise are illustrated in Figs. '7, S and 9. In these figures the dot-dash line il represents the center line of the pickup as lwell as the aXis of the pickup unit comprising the piezoelectric element 24, the chuck 25, and the needle 26. The casing halves 2| and 22 are represented by the stops 45 and 4 6. The direction of View of Figs. 7, 8 and 9 may be the same as that in Figs, 3, 5 and 6, which may be the direction a workman would look when assembling the device. In Fig. 7 the piezoelectric ele ment 24 is laterally offset from the center line but parallel to it. In Fig. 8 the piezoelectric element 2li has its forward end lying on and being bisected by the center line 4T, but has its rearward end laterally displaced from the center` line. In Fig. 9 the piezoelectric element 24 has its rearward end on and bisected by the center line 47 and has its forward end laterally displaced therefrom. The chuck 25 is shown in each of the Figs. 7, 8 and 9 in a dotted position also, which is the position the chuck would occupy if the center line thereof `were coincident with the center line of the piezoelectric element 2d in each of the positions shown. It will be observed in Fig. '7 that the chuck 25 (dotted position) is virtually touching the stop 45 while it is spaced farther away from stop 46 than is normal, and in Figs. 8 and 9 that the chuck 25 (dotted position) is virtually touching the stop 46 while it is spaced farther away from stop 45 than is normal, as may be seen in Figs. 3 and 6 wherein the chuck lib occupies the proper position between the stops l5 and iiii. In each of the instances of Figs, '7, 8 and 9 wherein the chuck 25 is shown dotted, it will be clear that the chuck may vibrate farther in one direction than in the other and may hit one of the stops during normal operation with consequent poor sound reproduction.

These and other instances may be obviated according to the method of the invention by first assembling the transducing or piezoelectric element 24, the rubber blocks 2l' and 28, and the casing halves 2l and 22 together as a single unit, followed by assembling the Vchuck to the piezoelectric elernent and cementing the two, as will now be described.

According to the steps of the invention, the rubber blocks 2l and 23, the piezoelectric element 2d, and the casing halves may be assembled toe gether as a unit or a subassembly with the rivets ifi and 35 holding the unit together in any desired way. For example, the rubber block 23 may be disposed within the hollow of casing half 2i with the back of the rubber block in contact with the serrations 39. In this position a rectangular groove in the lower portion of rubber block 28 is exposed and the piezoelectric element 24 may be disposed therein substantially as shown in solid lines in Fig. 4. The rubber block 2l may then be similarly assembled against the serrations 38 of casing half 22 and the two casing halves placed in proper position opposite each other and thev rivets 34 and 35 applied, the resulting construction being that of Fig. 4 as shown by the solid and the phantom lines together and that of Fig. 5. The insulating and/or vibrational damping material 41% may be applied to the end of the piezoelectric element before it is assembled into the casing halves or afterwards, as may be desired.

After this subassembly has been made, the

piezoelectric element 24 may occupy the correct or center line position, as may be seen in Fig. 5, or any one of the positions shown in Figs. 7, 8 and 9, or perhaps others, these positions arising, as has already been indicated, by slight differences in dimensions of the parts, which differences however are within the manufacturing tolerances. The displacement of the piezoelectric element 24, as shown in Figs. 7, 8 and 9, is ex aggerated in order to bring out the conditions had in mind with clarity.

After the subassernbly of Figs. 4 and 5 has been made, the chuck 25 is disposed between the stops 45 and 46 substantially equidistantly by means of shims 4% or other spacers. The prongs di and 42 are disposed so as to lie one on each side of the right end of piezoelectric element 2s. In order to assist the handling of the chuck 25 in this position, it being borne in mind that the chuck 25 as well as the other parts are small parts and are handled by small implements such as forceps, a small dab of fluid cement may be placed at the end of the piezoelectric element 2d and the prongs 4i and 42. The cement becomes tacky and holds the chuck and the piezoelectric element slightly while the shims may be disposed to accurately place the chuck between the stops 45 and 46. The chuck is, so to speak, held in a functional relationship to be with respect to the piezoelectric element. In placing the chuck with the prongs di and l2 into cooperative relationship with the end of piezoelectric element 2d, there is no stress placed upon the piezoelectric element and consequently it is not deflected from the position which it has by virtue of its assembly in the casing halves, as already described. After the correct placement has been reached, a proper amount of cement 49 is placed over the prongs 4i and 42 and the coacting end of the piezoelectric element.

In the structure of Fig. 6, it is only necessary for the chuck 25 to be equidistantly disposed between stops 45 and i6 and the chuck pushed rearwardly until the end of the piezoelectric element is received within the base of the trapezoidal groove. Thereafter the cement i9 may be applied and allowed to harden after which the shirns 48 are removed and the pickup is ready to have the needle inserted into the chuck.

In Fig. 7, and considering the instance where the chuck is shown dotted, it will be understood that if shiins or other spacers were utilized to force the chuck to occupy a central position between stops i5 and @t and one in which the center line of the chuck 1lies on the center line fi'i, the piezoelectric element 2d would be bent and consequently would have stress therein. Then, when the shims were removed after cement is applied to the conforming parts and allowed to harden, it is clear that the chuck would not occupy a central position between stops i5 and dii. The shims 48 are so placed that the chuck 25 is substantially equidistant between the stops dii and 46 and the prongs 4l and l2 are allowed to take their places on the respective sides of the piezoelectric element `as they will, the base of the trapezoidal groove, however, being disposed against the adjacent end of the piezoelectric element. In this position of the piezoelectric element and the chunk, there is no stress between these two parts. Consequently, cement may be: applied, allowed to harden, and the shims it removed, and the chuck 25 remains relative to the piezoelectric element in the position shown by solid lines.

In Fig. 8 the same procedure is followed, that is, the chuck 25 is placed with the prongs il and 152 on opposite sides, respectively, of piezoelectric element 24, and shims 8 are so arranged as to space the chuck 25 equidistantly between. the stops L15 and t5. It will be observed in this gure that with the forward end of the piezoelectric element lying on the center line 4l, the chuck 25 lies on the center line 47 also. There is no stress between the chuck and the piezoelectric element in the position shown by the solid lines, and after cement is applied to the prongsY and the cooperating end of the piezoelectric element, allowed to harden and the shims removed, the parts will remain as shown by the.l solid lines.

In Fig. 9 the same procedure also is followed, that is, the chuck 25 is placed with the prongs ii and i2 on opposite sides, respectively, of the forward end oi piezoelectric element and shims. d8 are disposed so as to place the chuck midway between the stops d and 6, there being no stress between the chuck and the piezoelectric element. Cement applied to the prongs 4i and 42 and the cooperating end of the piezoelectric element and allowed to harden will hold the parts in the relative position shown. Thereafter the shinis may be removed.

When assembled as described, the chuck 25 will lie substantially midway between stops i5 and it and consequently vibrations may occur equally in both directions with resulting good reproduction of sound.

While particular embodiments of the invention have been shown, it will be understood, of course.. that the invention is not limited thereto since many modiiications may be made, and it is, therefore, contemplated by the appended claims to cover any such modications as fall within the.- true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

l. In a phonograph translating device including a pair of casing halves held together to form a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including, la transducing element held at one end in said opening and a phonograph needle chuck cemented to such transducing element in line therewith at its other end; and stop means on said casing halves for limiting lateral movements of such needle chuck and transducing element; the method of assembling said device comprising the steps of assembling one end of said transducing element into the opening in said resilient members and said resilient members into said casing halves to form a inal subassembly, disposing said needle chuck with one end in functional relationship to be with the other end of said transducing element and while so disposed holding said needle chuck substantially midway between said stops and in stress-free relationship with said transducing element, and cementing said needle chuck and said transducing element together While said needle chuck is so disposed.

2. In a phonograph translating device including a pair of casing halves held together to form a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including, a piezoelectric element held at one end in said opening and a phonograph needle chuck cemented to such piezoelectric element in line therewith at its other end;

and stop means on said casing halves for limiting lateral movements oi such needle chuck and piezoelectric element; the method of assembling said device comprising the steps of assembling one end of said piezoelectric element into the opening in said resilient members and said resilient members into said casing halves to form a nal sub-assembly, disposing said needle chuck with one end in functional relationship to be with the other end of said piezoelectric element and while so disposed holding said needle chuck substantially midway between said stops and in stress-free relationship with said piezoelectric element, and cementing said needle chuck and said piezoelectric element together while said needle chuck is so disposed.

3. In a phonograph translating device including a pair of casing halves held together to form a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including, a piezoelectric element held at one end in said opening Iand a phonograph needle chuck cemented to such piezoelectric element in line therewith at its other end; and stop means on said casing halves for limiting lateral movements of such needle chuck and piezoelectric element; the method of assembling said device comprising the steps of assembling one end of said piezoelectric element into the opening in said resilient members and said resilient members into said casing halves to form a final subassembly, disposing said needle chuck with one end in functional relationship to be with the other end of said piezoelectric element and while so disposed shimming said needle chuck to lie substantially midway between said stops and in stress-free relationship with said piezoelectric element, cementing said chuck and said piezoelectric element together while said needle chuck is so disposed and held, and removing said shims.

4. In a phonograph translating device including a pair of casing halves held together to formV a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including, a piezoelectric element held at one end in said opening and a phonograph needle chuck cemented to such piezoelectric element in line therewith at its other end; and stop means on said casing halves for limiting lateral movements of such needle chuck and piezoelectric element; the method of assembling said device comprising the steps of assembling one end of said piezoelectric element into the opening in said resilient members and said resilient members into said casing halves to form a final subassembly, disposing said needle chuck substantially midway between said stops with the appropriate end of said needle chuck'in functional relationship to be with said other end of said piezoelectric element and in stress-free relationship therewith, and cementing said needle chuck and said piezoelectric element together while said needle chuck is so disposed.

5. In a phonograph translating device including a pair of casing halves held together to form a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including a piezoelectric element held at one end in said opening; and a phonograph needle chuck having a pair of prongs each of which lies on one side respectively of the other end of such piezoelectric element, said prongs being cemented to such piezoelectric elemnt with the chuck in line therewith; and stop means on said casing halves for limiting lateral movements of such needle chuck and attached piezoelectric element; the method of assembling said device comprising the steps of assembling one end of said piezoelectric element into the opening in said resilient members and said resilient members into said casing halves to form a final subassembly, disposing said needle chuck substantially midway between said stops with each of said prongs lying on respective sides of said piezoelectric element and in stress-free relationship therewith, and cementing said prongs and said piezoelectric element together while said needle chuck is so disposed.

6. In a phonograph translating device including a pair of casing halves held together to form a casing; a pair of resilient members inside of said casing halves and having an opening therein; a pickup unit including a piezoelectric element held at one end in said opening; and a phonograph needle chuck having a pair of prongs each of which lies on one side respectively of the other of such piezoelectric element, said prongs being cemented to such piezoelectric element with the chuck in line therewith; and stop means on said casing halves for limiting lateral movements of such needle chuck and attached piezoelectric element; the method of assembling said device comprising the steps of assembling one end of said piezoelectric element into the opening in said resilient members and said resilient members into said casing halves to form a final subassembly, disposing said needle chuck with each of said prongs lying on respective sides of said piezoelectric element and while so disposed holding said needle chuck substantially midway between said stops and in stress-free relationship with said piezoelectric element, and cementing said needle chuck and said piezoelectric element together while said needle chuck is so disposed.

LEE GNTER, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,352,311 Di Toro June 27, 1944 2,363,497 Begun Nov. 28, 1944 2,518,861 Burtch Aug. 15, 1950

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