US2376741A

US2376741A - Pickup arm control

Info

Publication number: US2376741A
Application number: US462340A
Authority: US
Inventors: Jerald D Weaver
Original assignee: Farnsworth Television and Radio Corp
Current assignee: Farnsworth Television and Radio Corp
Priority date: 1942-10-17
Filing date: 1942-10-17
Publication date: 1945-05-22
Anticipated expiration: 1962-05-22

Description

y 2, 1945. J. D. WEAVER PICK-UP ARM CONTROL Filed Oct. 17, 1942 FIG.5

INVENTOR useful improvements PatentedMay 22, 1945 r PICKUP ARM CONTROL Jerald D. Weaver, Fort Wayne, Ind., assignor to Farnsworth Television and Radio Corporation,

a corporation of Delaware Application October 1, 1942, SerialNo. 462,340

4 Claims.

This invention relates generally to new and in automatic selective phonographs and more particularly to a novel mechanism for pickup arm control.

In conventional pickup arm control mechanisms, the pickup arm is pivotally mounted for vertical and horizontal movement on a rotatable tubular shaft supported in a pedestal at one side of the turntable. It has been the usual practice to provide a vertically movable pin in the tubular shaft for elevating the pickup arm. Therefore, at least two separate levers and two associated cam surfaces must be provided for pivoting one of the levers to elevate the pickup arm out of eneasement with a record on the turntable, and for actuating the second lever to swing the pickup arm horizontally to a non-playing position. Near the end of the cycle of operation, a cam wheel cooperates with the levers to swing the Pickup arm inwardly over the initial groove of a record and properly position the pickup arm for engagement with the record on the turntable.

Pickuparm control mechanisms such as that described above, require expensive manufacturing tools and operations as the manufacturing dies are expensive and the operations must be performed to close tolerances, Furthermore, the various levers may be easily sprung out of shape and otherwise injured while in service to render the mechanism inoperative. It is, therefore, desirable that the cams be simplified and th levers be eliminated to as great an extent as possible. This type of mechanism also requires delicate adjustment and, therefore, requires frequent read- .iustment to obtain satisfactory operation. Thus, the elimination of adjustable parts is also very desirable.

The principal object of the invention is to provide, in a phonograph mechanism, an improved pickup arm control mechanism for positively effecting an-automatic adjustment of the pickup am to a predetermined vertical and horizontal position with respect to the initial playing grooveof a record on the turntable during a recordchanging interval.

Another object of the invention is to provide, in a phonograph'mechanism, a simple, inexpensive pickup arm control mechanism which has few parts and requires minimum service to assure satisfactory operation.

In accordance with the present invention, there is provided, in a. phonograph mechanism, a pickup arm mounted at one side of the turntable on a pedestal which is rotatably supported by a hear. ing member interposed between the base of the pedestal and the base plate of the phonograph. A lever is pivotally mounted on the pedestal and is adapted to be moved into and out of engagement with the pickup arm for lifting it out of engagement with a record on the turntable. A pin which is operatively associatedv with the pivoted lever extends below the rotatable pedestal and has a cam member affixed to its lower end. A rotatable member which is operated by a cam wheel driven by the turntable, is operatively associated with the rotatable pedestal and the cam member. The rotatable member is so designed,

that during a cycle of operation of the cam wheel,

it first functions to move the cam member vertically downward against the biasing action of a first spring member thereby actuating the pivotal. lever to lift the pickup arm out of engagement with the record on the turntable. As the cam wheel continues to operate the rotatable member,

it functions-to swing the rotatable pedestal andthe pickup arm horizontally to a non-playing position against the biasing action of a second spring member. Near'the end of the operating cycle of the cam wheel, it permits the second spring member to swing thepedestal and pickup arm inwardly while the cam member maintains the pickup arm in its elevated position. When the pickup arm is swung inwardly to a predetermined position, the cam member engages a stop and further inward movement of the pickup arm is arrested. However, the second spring member continues to move the rotatable member inwardly to a position wherein the first spring member is permitted to move the cam member vertically upward to properly position the pickup arm in engagement with the initial groove of the record on the turntable. Thereafter, the cam wheel ceases to move the rotatable member during the playing of the record on the turntable.

- support and control mechanism;

Fig. 2 is a perspective view of showing the contour of the cam surfaces for elevating the pickup arm;

Fig. 3 is a plan view partly in section of the cam wheel and cam surface for swinging the pickup arm horizontally taken on line 3-3 of Fig. 1;

Fig. 4 is a fragmentary view partly in section taken from the left side of Fig. 1, showing the driving mechanism associated with the turntable and the cam wheel;

Fig. 5 is a fragmentary plan view of the driving mechanism taken on line 5-5 of Fig. 1.

Fig. 6 is a fragmentary view in elevation of Fig. 1.

Referring particularly to Figs. 1 and 2 of the drawing, the invention here illustrated shows a pickup arm control mechanism which includes a base plate I and a rotatable turntable ll, upon which is shown records i2.. The turntable I i mall be driven in amanner such as disclosed in U. S. Patent No. 2,286,490 of Arthur L. Knox, patented June 16, 1942. A pickup arm i3 is mounted at one side of the turntable ii on a pedestal I 5 havtions l1 and i8 as shown in Fig. 1. There is provided a ball-bearing assembly between the flanged portion [6 and the upper side of the base plate ill for rotatably supporting the pedestal IS. The reduced portion ll extends downwardly to a point flush with the underside of the base plate II). An annular member 22 is fixed to the reduced portion l8 in engagement with the lower shoulder of the reduced portion I1 and is adapted to move freely in contact with the underside of the base plate ill to maintain the pedestal IS in proper position to rotate on the bearing member 20. A suitable friction element is provided on the underside of the annular member 22 (Fig. 1). The pickup arm I: is pivotally mounted on pin 26 in the pedestal i5 to swing horizontally and vertically thereon into and out of engagement 'with a record on the turntable ll. end of the pickup arm I3, there is provided a reproducer 23 with a stylus 24 which is adapted to cooperate with a record on the turntable ll.

As shown in Fig. 1, the pickup arm elevating linkage consists of an L-shaped member 21 pivotally mounted on the pin 26 together with aspringbiased pin 30. The member 21 is provided with an adjustable screw 28 adapted to be moved into engagement with the underside of the pickup arm l3 to lift the same. The right-hand end of the member 2'! is provided with an elongated aperture 29. The spring-biased pin 30 supported by the pedestal l4 has a bent end 3| which engages member 21 in the aperture 29, as shown in Fig. 1, and its lower end extends downwardly below the base plate Ill. The pin 30 is provided with a fixed flange 32, and is maintained in the elevated position shown in Fig. 1 by a spring 33, the upper end of which engages the flange 32 and the lower end of which rests on a shoulder 34 of a bore 35. A cam member 36 is aiiixed to the lower end of the pin 30 (Figs. 1 and 2), to rotate therewith and includes a pair of cam portions 39 and 40 (Fig. 2), a first stop lug 4|, and a second stop lug 42. The

annular end 44 of a rotatable member 45 is slid-'- ably mounted on the reduced portion i8 of the pedestal l5, between the annular member 22 and the cam member 38, as shown in Fig. 1. The member 45 is provided with an arm 46 which supports at its free end a smaller roller 41 (Figs. 1 and 3). The annular end 44 of the member 45 is provided with two recessed portions 49 (Figs. 1 and 6), the contours of which correspond to the contours of the

cam portions

39 and 40 of the cam member 33 '(Fig. 2). Normally, while the stylus 24 of the pickup arm I3 is tracking the playing grooves of a record, the

cam portions

39 and 40 are in engagement with the recessed portions 49 of the member 45 and as the pickup arm moves inwardly, the member 45 is moved in a clockwise At the free i ing a flanged portion l6 and two reduced pordirection. The annular end 44 of the member 45 (Figs. 1 and 3) is provided with a notched portion 50 which is adapted to engage a pin 5| atfixed in the reduced portion I8 of the pedestal l5 to rotate the pedestal i5 and swing the pickup arm l3 horizontally outward to a non-playing position. When the member 45 has rotated in a counterclockwise direction to a predetermined position, a pin 82 on the annular end 44 of themember 45 (Figs. 1 and 3) engages the turned up end 83 of a spring member 84, the opposite end of which is connected to the stud 54. The spring member 84 retards the outward movement of the pickup arm and tends to swing the pickup arm inwardly to a predetermined position.

As shown in Figs. 1' and 3, a spring-biased ratchet member 53 is pivotally mounted on a stud 54 which depends below the base plate ill, as shown in Fig. 1. The ratchet member 53 i biased as shown in Fig. 3, into engagement with a stop pin 55 by a spring 56 which has one end anchored I to the ratchet member 53 and the other end anchored to the pin 55. The right-hand end of the ratchet member 53 (Fig. 3) is provided with rachet teeth 56 adapted to engage the flrst stop lug 4| of the cam member 38 as the pickup arm i3 moves inwardly over the record on the turntable II.

As shown in Fig. 3, a spring-biased pivoted element 60 is pivotally mounted on a stud II which is mounted on the underside of the base plate II). The pivoted element 60 is biased, as shown in Fig. 3, into engagement with a stop pin 62 by a spring 63 which has one end anchored to the pivoted element' 60 and the other end anchored to the pin 62. The right-hand end of the pivoted element 60 (Fig. 3) is positioned to be engaged by the second stop lug 42 of the cam member 36 when the pick-up arm 13 and the member 45 are moved inwardly from the outwardmost position.

The mechanism for moving the member 45 in a counterclockwise direction and therewiththe pickup arm horizontally outward, includes a cam gear 65. The cam gear 65, as shown in Fig. 1, is fixed to a shaft 66 which extends downwardly below the base plate I0 (Fig. 1). Referring to Fig. 3, it will be noted that several teeth have been removed at 61 to provide a mutilated portion, the purpose of which is to break the driving connection between the cam gear and a small pinion gear 68 fixedly secured to a shaft 69 which is supported by a bracket 10 (Fig. 1). The cam gear 65 may be moved into driving engagement with the pinion 68 by a tripping mechanism such as disclosed in U. S. Patent No. 2,286,490 of Arthur L. Knox, patented June 16, 1942. As shown in Figs. 1 and 5, a small pinion gear II is aflixed to the upper end of the shaft 69 in continual driving engagement with a similar pinion gear 12 fixedly secured to a shaft 14 which supports and moves with the turntable II. The shaft 14 is also rotatably supported by the bracket 10, as shown in Fig. 5. One complete revolution of the gear 65 defines a complete change cycle of the pickup arm movement as will be evident hereinafter.

The gear 65 is provided with a cam surface 16 (Fig. 3) comprising an angular portion "A; a concentric portion 163 and an eccentric portion 160. As shown in Fig. 3, the roller 41 on the member 45 is adapted to move over the cam surface 16.

In operation, a record is placed on the turntable Ii, the stylus 24 of the pickup arm I3 is manually brought into engagement with the initial playing groove of the record on the turntable,

and the rotation of the turntable is initiated. While the stylus 24 tracks the playing groove of a record on the turntable, the pickup arm I3 is moved inwardly to the center of the turntable I plane relative to the pinion 68 sufilciently'far to bring the cam wheel 55 into drivingengagement with the pinion 68. Thereafter the cam wheel 55 is driven through one revolution until the mutilated portion 61 is again adjacent the pinion 68.

When the cam wheel 65 begins to rotate, the roller 41 on the arm 46 engages the cam surface 16A and the arm 46 is cammed to move in a counterclockwise direction (Fig. 3). Normally when the arm 46 is moved in a counterclockwise direction (Fig. 3) the cam member 38 would rotate in a corresponding direction. However, the rotary movement of the cam member 38 in-this direction is arrested by the locking-engagement be tween the lug 4| of the cam member 38 and the ratchet 48 on the spring-biased member 53 (Fig. 3). Thus, as the cam wheel 65 moves the member 45 in a-counterclockwise direction, the recessed portions 49 engage the cam'portions 39 and to depress the cam member 38 and therewith the pin 30 vertically downward against the biasing-action of the spring 33. As the pin 30 and the bent portion 3| are moved downwardly, the member 21 is tipped in a clockwise direction (Fig. 1) moving the screw 28 into engagement with the underside of the pickup arm l3 to thereby elevate the stylus 24 out of engagement with the record on the turntable. when the cam member 38 moves downwardly, the first stop lug 4| is moved downwardly out of engagement with the spring-biased member 53 and the annular portion 44 of the member is moved into frictional engagement with a friction element 25 on the underside of the member 22 (Fig. 1). This frictional engagement prevents the member 45 I from moving horizontally unless a positive force is applied thereto. As the cam wheel 65 continues to move the member 45 in a counterclockwise direction (Fig. 3) the left-hand side of 'the notch (Fig. 3) engages the pin 5| in pedestal l5 and moves it, together with the pickup arm l3, in a counterclockwise direction. As the member 45 further rotates, the pin 82 aflixed to the annular end 44 of the member 45, engages the turned up end 83 of the spring 84 (Figs. 1 and 3). Further movement of the member 45 builds up tension in the spring member 84. By the time the concentric cam portion 183 engages the roller 41, the

pickup arm [3 is moved to its outermost position.

When the cam. wheel 65 is rotated to the position where the cam portion 160 engages the roller 41, themember 45 is moved in a clockwise direction (Fig. 3) under the biasing action of the spring 84. The pickup arm I3 is also moved inwardly by the frictional engagement between the members 45 and 22. As the pickup arm I3 is swung from non-playing to playing position, it is held elevated by the engagement of the

cam portions

39 and 40 with the underside of the member 45 until such time as the stylus 24 of the pickup arm I3 is immediately over the initial playing groove of the record on the turntable H. Forther inward movement of the pickup arm l3 by the spring 84 is arrested by the engagement of the second stop lug 42 on cam member 38 with the spring-biased member 80 (Fig. 3).

- When the inward movement of the pickup arm I3 is arrested in this manner, the tension spring 83 is still imparting a force upon the member 45 and thus continues to move the member 45in a I clockwise direction. When the member 45 is moved inwardly to the full line position in Fig. 3, the portions 48 move into engagement with the

cam portions

39 and 40 thereby to permit the' spring 33 to elevate the cam member 38 and the pin 3ll and lower the pickup arm l3 and the stylus 24 into engagement with the initial playing groove of the record on the turntable. When the cam member 38 is elevated as described above, the second stop lug 42 is moved out of engagement. with the'spring-biased stop 60 (Fig. 3) to allow the pickup arm |3 to move easily over the surface of the record as the stylus 24 strikes the playing grooves. Thereafter the driving engagement between the cam wheel 55 and the pinion gear 68 is broken by the mutilated portion 31 and reproduction of the record takes place.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An automatic phonograph comprising a record-supporting turntable, a pickup arm mounted adjacent said turntable for vertical and horizontal movement, linkage means associated with said pickup arm for imparting vertical movement thereto, movable cam means fixed to said linkage means, a movable cam operating means in engagement with said cam means and operatively associated with said pickup arm for imparting movement to said cam means and said linkage to elevate and rotate said pickup arm, and means for moving said cam operating means.

2. An automatic phonograph comprising a record-supporting turntable, a pickup arm pivoted adjacent said turntable for vertical and horizontal movement, linkage means associated with said pickup arm for imparting vertical movement thereto, movable cam means fixed to said linkage means, arotatable cam'operating means in engagement with said cam means and operatively linkage means associated with said pedestal to engage said pickup arm for imparting vertical movement thereto, movable cam means fixed to said linkage means, a rotatable cam operating means in engagement with said cam means and linked with said pedestal for imparting vertical movement to said cam means and said linkage and rotational movement to said pedestal, means for rotating said cam operating means, first and second lugs on said cam means, ratchet means fixed in a certain plane to said base plate for engaging said first lug for arresting movement of said cam means in a certain direction whereby the rotatable cam operating means imparts vertical movement to said cam means, and stop means fixed in another plane to said base plate for engaging said second lug for arresting rotational movement of the cam means and the pedestal in the other direction whereby to determine the position of the pickup arm.

4. An automatic phonograph comprising a base plate, a record-supporting turntable rotatably supported thereon, a rotatable pedestal on said base plate adjacent said turntable, a pickup arm pivoted on said pedestal for vertical movement, linkage means associated with said pedestal to engage said pickuparm for imparting vertical movement thereto, movable cam means fixed to said linkage means, a rotatable cam operating means in engagement with said cam means and linked with said pedestal for imparting vertical movement to said cam means and said linkage and rotational movement to said pedestal, means for rotating said cam operating means, first and second lugs on said cam means, ratchet means fixed in a certain plane to said base plate for engaging said first lug for arresting movement of said cam means in a certain direction whereby the rotatable cam operating means imparts vertical movement to said cam means, stop means fixed in another plane to said base plate for engaging said second stop lug for arresting rotational movement 01 the cam means and the pedestal in the other direction, and spring-biasing means for urging said cam operating means in said other direction to rotate said cam means, pedestal and pickup arm whereby to position the pickup arm over the initial playing groove of a record on said turntable.

JERALD D. WEAVER.