US2326280A - Translating device - Google Patents

Description

Aug. w, 1943. B. B. BAUER 2,32%,0

TRANSLATING DEVICE Filed May 21, 1941 Z2 37 @3 f7 0 52 fl! j? 1% 5f, cyeafifi jag Q02 )2 ja f @mmw manual adjustments areto Patented Aug. 10, 1943 TRANSLATING DEVICE Benjamin B. Bauer, Chicago, 111., 'assignor to S. N.

Shure and Frances Shure,

ness as Shure Brothers,

Application May 21, 1941, Serial No. 394,564 Claims. (Cl. 179-10041) This invention relates to phonograph translating devices having a torsional drive rod. The invention is applicable to either a recorder or reproducer and certain features of the invention are of general application to a torsion rod drive. An important feature however concerns itself with the use of a relatively stiff translating means per se in connection with a torsion drive rOd.

A torsion drive rod for lateral record grooves utilizes a needle or stylus extending generally" transversely to the rod axis. In such a construction, it is desirable from a theoretical angle to endow the drive rod with only one degree of movement; i. e. torsional about its longitudinal axis. Longitudinal and lateral rod movement are ordinarily to be avoided.

As is well known, the width of a laterally cut groove is constantly varying. Where the groove width decreases, a vertical component of force is created tending to raise the needle, assuming the needle is above a horizontal record. This is known as the pinch effect and should be considered as a substantial factor. In practice therefore, it is highly desirable to provide for some transverse rod travel in a direction perpendicular to the record under normal operating conditions.

It follows that there should be a controlled elasticity for needle movements tending to vibrate the drive rod perpendicularly to the record. Since the rotational elasticity of the drive rod is highly important in regard to characteristic control, it is clear that these two elasticities should preferably be independent. This has not heretofore been true of prior devices. In general the mechanical construction interlinked these two elasticities so that independent control of each was impossible. As a rule, the final characteristics were a compromise between conflicting tendencies.

In a torsion drive device, there must be some physical means for connecting the drive rod with the translator per se; i. e. with the element where energy conversion takes place. If a translator has a greater stifiness than is desirable to project to the needle point, a coupling must be used so that the needle may be deflected more easily.

As is well known, the moment of inertia of a rotary part is a function of the square of the radius. By keeping down the radius to a minimum value the moment of inertia is reduced. However, mechanical coupling details require relatively larger and smaller parts, particularly if e provided. In such case, I dispose the smaller its in the drive rod seen in Figs. 3 and 4, the-vertical dimension is trustee, doing busia partnership part of the system and have the larger parts in two, a. flexible coupling maybe provided which functions to change large vibrations of a flexible .element to smaller vibrations of a stiller element.

Referring now to the drawing:

Figure 1 is a top plan view of a translating device, with the top casing member removed;

Fig. 2 is a section on 22 of Fig. 1 but with the top casing member in place;

Fig. 3 is a front elevation of a translating device;

Fig. 4-is' an enlarged view of'the torsion rod bearing shown in Fig. 3; 1

Fig. 5 is an enlarged view of a modified torsion rod bearing;

Fig. 6 is a sectional elevation of a modified translator and clamp combined; and

Fig. 7 is a section on 1-4 of Fig. 6.

The translating device as a whole includes a pair of complementary case members In and H. Both members are generally similar and may be of stamped aluminum, sheet iron, die cast or may even be of a suitable plastic material. Both base members are generally dished to provide a comparatively large compartment I2 formed by wall portions l3 and 14. Rear edges l5 and I6 of the case may be inturned and fitted against an insulating terminal block [1.

The front portion of the case is shaped to provi-de a pair of journals l8 and IS, the metal being pushed inwardly to form the journals. The free I, edges 20 and 2| of the two casing shells meet along the case sides and front. The two shells may be maintained tightly in position by bolts passing through apertures 22, 23 and 24.

Journal l8 and preferably also journal I9 are not circular, as might be expected but have an elongated shape with the long dimension being perpendicular to the general casing plane. As

somewhat longer than the horizontal one. The diiference need not be great and in practice need only amount to about a hundredth of an inch or so. The drawing obviously shows the elongation exaggerated.

Disposed within the forepart of the casing is a torsion drive rod 2G.having a generally circular section and a male coupling element as a flat tail piece 21. Drive rod 26 may have an axial threaded channel 28 into which a thumb screw 29 may be disposed. A generally transverse needle receiving slot 30 is provided at an intermedate part of the rod and into this may be disposed a needle 3|. This needle may be either a conventional reproducing needle or a jewel or may be a cutting stylus for recording. The needle is clamped by screw 29 and preferably extends forward of the device, as shown in Fig. 2. A suitable aperture 32 in casing member II is provided for clearing the needle. A tubular guard 33 is carried by easing member and extends around needle 3| for a distance so that only the tip of the needle clears. Thus guard 33 will take up any shock above that necessary to push the needle tip Rod 26 has reduced circular bearing portions 34 and 35 on opposite sides of the needle clamping region and these reduced portions register with journals l8 and I9 respectively. Around reduced portions 34 and 35 are flexible sleeves 36 and 31 of rubber, felt or the like. It will be noted that the casing flares outwardly on both sides of journal l9. Preferably, reduced portion 35 has about the same length as bearing journal l9 while sleeve 31- is longer than reduced portion 35. Thus the sleeve material stretches out on both ends of the bearing portion and efiectively forms a thrust bearing for axially directed forces. The ends of the sleeves are thus firmly retained against longitudinal force. A somewhat similar thrust bearing action may be obtained by sleeve 36 on reduced portion 34.

Both sleeves 36 and 31 are just thick enough so that a resilient bearing is provided. Each sleeve is originally uniform in thickness so that an increase in resiliency along a vertical axis, as seen in Figs. 3 and 4, results. The elongation of one or both bearing journals may be sufficient to provide open regions 36 and 39 above and below the sleeves. It is understood that substantially the same result may be obtained by varyin the sleeve thickness and having round bearing. or by having uniform sleeves in round journals and flattening the drive rod at the top and bottom as shown in Fig. for example. The thickest part of the variable sleeve would be at the horizontal axis and this would be most compressed.

Since the compression of the sleeves 36 and 31 controls the torsional flexibility of the drive rod, it is clear that this characteristic is independent of the vertical elasticity of the drive rod mounting. The angular extent and depth of free bearing regions 38 and 39 will determine the elasticity of the rod mounting to vertically transverse forces. Hence the elastic properties of the drive rod mounting to torsional movement and vertical translation may be independently controlled.

' Tail piece 21 may have disposed on opposite sides thereof fiat rubber or other flexible pads 40 and 4|. If desired one pad may be omitted. It is preferred however to have one pad of different compressibility and resistance than the other. Flexible materials like rubber, leather, cork or the like have a non-linear characteristic of stress and strain, the compressibility and resistance depending upon the initial compression. It is clear that by having pads 40 and 4| difierent, it is possible to control the vibratory characteristics of the entire coupling. Thus particularly desirable results have been secured by having one pad of a material whose predominant characteristic is elasticity, such as live rubber, and by having the other pad of viscous material whose predominant characteristic is resistance, such as viscoloid.

A pair of clamping members 42 and 43 engage the padded tail piece and the pressure of engagement may be controlled by bolt 44 loosely passing through one piece, here 42, and threadedly engaging the other piece. In effect, the couplin consists generaly of a male member on the drive rod and a female member cooperating therewith.

As shown in Fig. l, clamping members 42 and 43 are generally T-shaped with the bottom of the T preferably engaging the tail piece 21. Other shapes of clamping members are possible. Members 42 and 43 may be springy if desired.

Pads 40 and 4| and clamping members 42 and 43 with bolt 44 really form a transmission coupling with adjustable characteristics. Suitable apertures 45 in the casing give access to bolt 44 and permit adjustment after assembly. Flexible pads 46 and 41 at the center of the T may be provided to engage the casing wall. Flexible pads 48 and 49 on opposite sides of the tail piece 21 may be also provided.

Clamping members 42 and 43 are adapted to clamp any vibratable element of an energy translator between the head ends 50 and 5|. The means clamped may be an armature of an electro-magnetic device, a piezo crystal, a condenser assembly or any other suitable means. Thus as shown in Figs. 1 and 2, a flat torsionally responsive crystal 52, suitably wrapped, may be gripped between clamping ends 50 and 5|. The crystal may be braced at the faces and sides thereof by flexible pads 53' and 54. Wires 55 may be brought out to soldering terminals 56 carried by terminal block H.

The female clamp parts are more or less tightly coupled to the translator and both vibrate at an amplitude small in comparison to that of the drive rod. Thus the effective inertia at the drive rod of the relatively massive female part of the coupling and the manual adjustment is small.

In Figs. 6 and 7, a modification is shown where a condenser having movable plates is used as a translating device. In this form, an insulating frame consisting of flat plates 60 and 6| with spacers 62 and 63 is provided. Carried by plates 60 is a pair of metal electrodes 65 and 66, these being long and narrow and preferably 'symmetrical with respect to the longitudinal axis of plate 60. Plate. 6| also carries similar plates 6'! and 68. Spaced between these opposing electrodes is a vibratable electrode plate 10 rigidly clamped at H and having formed integral therewith clamps 'l2 and 13. Suitable insulating means such as hard rubber pads 15 may be provided at 12. Obviously plates 65 and-68 as one pair and 66 and 61 as the other pair cooperate with movable plate 10 for translating action. A cross connected pair of three plate condensers is thus provided. Thus wire I! connects plates 65 and 68 and is brought out to a terminal 18. Similarly wire I9 connects plates 66 and 67 and is brought out to a terminal 80. Wire 8| is connected to movable plate 70. Thus push-pull circuit action is obtained. It is understood that wire 8| and one of the remaining two terminals inay be utilized in a conventional two wire sys- By virtue of the construction disclosed herein highly desirable characteristics are obtained. Thus the non-circular journals at l8 and I9 provide increased elasticity to shock in the drive mounting perpendicular to the record. This would occur in case the entire device'were set down too hard on the needle. Guard 32 of course protects the entire device against excessive shock. Also, the resilient mounting permits the needle to adjust itself in the record groove. By having substantial resiliency, groove wear in reproduction may be greatly reduced.

The drive rod bearings also provide an end thrust protection and tend to hold the rod with some elasticity against longitudinal movement. This end thrust provision does not impair the rotational flexibility of the mounting as is the case when the rubber supports are cemented to prevent longitudinal movement. The actual elastic structure is simplicity itselfmere1y some rubber tubing.

The provision of a simple fiat tail piece 21 and the clamp construction also has highly desirable features. Thus the drive rod is made simple and light and has low rotational inertia. The clamp with its adjusting screw is separated from the drive rod by flexible means here shown as pads 40 and M. Thus transmission characteristics between the drive rod and clamp may be controlled by pressure on the pads. The clamp and translating device are relatively tightly coupled. Because the clamp and bolt increase the rotational inertia of the vibratory system, it is desirable to couple it closely to the translator. By controlling the clamp tension, the vibratory characteristics of the entire device may be controlled within wide limits.

One highly desirable advantage of the construction is the ready removability of a translating unit and replacement thereof. Thus any translating unit, crystal, electro-magnet or condenser, may be replaced with another for any reason at all with a minimum of trouble.

It is clear that the assembly of the entire device may be accomplished with a minimum of equipment and skill. It is difficult to put anything together incorrectly and after assembly, the adjustment on the clamp is simple.

What is claimed is:

1. In a phonograph translating device, the combination of a resiliently mounted torsion rod having a male coupling element at one end thereof and an energy translator having a vibratable element with a female coupling element, said rod normally vibrating over a greater amplitude range than said vibratable element, and resilient means between said coupling members, said coupling members being adapted to cooperate to transfer vibratory energy whereby efficient energy transfer is eifected and th effective inertia of the system is kept low.

2. The system of claim 1 wherein said female coupling element has manual means for adjusting the degree of coupling between the coupling elements.

3. In a phonograph translating device, the combination of a resiliently mounted torsion rod having a flattened strip at one end thereof and an energy translator having a vibratable element including spaced gripping members, said rod normally vibrating over a greater amplitude range than said vibratable element, said strip being adapted to extend between the spaced gripping members, and resilient means for controlling the degree of coupling between said rod and gripping members whereby eflicient energy transfer is effected and the effective inertia of the system is kept low.

4. The structure of claim 3 wherein a predominantly elastic means on one side and a predominantly resistive means on the other side of said strip comprise the resilient means.

5. The system of claim 3 wherein manual means are provided on the coupling member for controlling the pressure of coupling exerted on said tail piece.

6. In a phonograph translating device, a torsion rod having a flattened tail piece, said rod being generally parallel to a record in the nor-.

mal position thereof, journals for supporting said rod, resilient sleeves between said rod and journals for biasing said rod to a predetermined torsional position, said resilient sleeves being compressed between said rod and Journal faces,.

means for varying the compression of said resilient means around said rod to provide substantially more elasticity in a plane generally perpendicular to a record and passing through the rod axis to permit the rod to move in response to a lateral force, an energy translator having a vibratable element, a pair of members embracing said tail piece and can'ied by said vibratable element, resilient means between said pair of elements and said tail piece for controlling the degree of coupling, said rod normally vibrating over a greater amplitude range than said vibratable element.

7. The system of claim 6, wherein means are provided for ripping the ends of at least one resilient sleeve around the rod at the journals for controlling end thrust.

8. In a. phonograph translating device, the combination of a resiliently mounted torsion rod having a flat tail piece at one end thereof, a

piezo-electric crystal of the torsional type, a

pair of coupling members extending between the crystal and tail piece and embracing both on opposite sides thereof for transmitting torsional vibration, and resilient means between said tail piece and coupling members for controlling the degree of coupling, said rod normally vibrating over a greater amplitude range than said crystal.

9. The structure of claim 8 wherein manual means are provided for controlling the compression of said two members embracing the crystal and tail piece.

10. In a phonograph translating device, the combination of a resiliently mounted torsion rod having a flat tail piece at one end, a condenser assembly having one torsionally movable plate and stationary plates on opposite sides of said movable plate, said movable plate carrying a pair of coupling members embracing both sides of said flat tail piece, and resilient means between said tail piece and coupling members for controlling the degree of coupling, said rod normally vibrating over a greater amplitude range than said movable plate.

BENJAMIN B. BAUER.

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