US3130597A - Servo-mechanisms - Google Patents

Description

April 28, 1964 M. GOLDBERG SERVO-MECHANISMS Filed NOV. 22, 1961 m R T H m 6 WE o G 4 A l M 3 Y m i B I I I ATTORNEY United States Patent Ofi Patented Apr. 28, 1964 ice 3,130,597 SERVS-MEQHANESMS fax Goldberg, 141 E. 3rd St., New York, NE.

Filed Nov. 22, 1961, Ser. No. 154,1ss 1 Claim. (Cl. 74-383) This invention relates broadly to servo-mechanisms and an object thereof is the provision of novel means for imparting motion or movement to an object worked upon, in two different directions at controlled speed varying between zero to a maximum determined or limited only by the power available.

Another object is the provision of a novel and useful device whereby the power of two rotating wheels, such as, merely by way of example, pulleys, may have a driven device such as, again by way of example, a winding drum, perform work upon a follower through the medium of two oppositely wound cables on the drum, wherein the wheels rotate in opposite directions on a shaft and provide a relatively large amount of power which is under control over a range between a minute fraction of the total available and the full power deliverable by the pulleys. As an example, if it is desired to move a heavy machine along the floor, with the axis of the drum at right angles to the desired line of travel of the machine, one cable is attached to the side of the machine facing the drum and the other cable is passed around a pulley secured, say, to a wall spaced from the opposite side of the machine and attached to said opposite side of the machine.

The invention is subject to numerous practical and useful applications, as will presently become evident from the following disclosure. Among such applications are, for example, the steering of a ship and the working of a capstan.

The operator of the device of the present invention may be a person who exerts his control manually upon a crank, or the control may be exercised by other means such as, for example, an electric motor which itself is, however, under the control of an operator. The operator does very little work compared with the Work output upon the object worked upon, that is, the follower.

The above as well as additional and more specific objects will be clarified in the following description wherein reference numerals designate like-numbered parts in the accompanying drawing. It is to be noted that the drawing is intended primarily for the purpose of illustration and that it is therefore neither desired nor intended to limit the invention to any or all of the exact details shown or described except insofar as they may be deemed essential to the invention.

Referring briefly to the drawing, FIG. 1 is a top plan view of a device embodying features of the present invention.

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary view illustrating a modification.

Referring more in detail to the drawing, in the embodiment of the invention illustrated the numeral indicates a base upon which are mounted two parallel shafts 11 and 12 supported, respectively, on pillow blocks 13 and 14.

The shaft 12 is shown to have two spaced pulleys 15 and 16 rotatably mounted thereon and confined to fixed longitudinal positions on the shaft by collars 17 and 18. Between the two pulleys a drum 19 is mounted on the shaft, and through the medium of one or more threads 20 on the shaft 12 and complementary internal threads 21 on the drum it is obvious that the drum may be moved longitudinally in either direction by rotating the shaft in either direction. The drawing shows a crank 22 for rotating or turning the shaft 12 manually. Complementary friction surfaces, herein illustrated as annular, are provided respecitvely on the drum at 24 and on the pulleys at 23.

On the shaft 11 there are two similarly spaced pulleys 25 and 26. An open belt 27 is trained about the pulleys 15 and 25, and a crossed belt 23 is trained about the pulleys 1d and 26. The shaft 11 is shown coupled to a motor 29 to rotate the shaft, normally through a reducing gearing.

The drum 19 is shown provided with an annular partition 31 intermediate its length. Wound on the two sides of the drum, shown at 31 and 32, separated by the partition are cables 33 and 34, Wound in opposite directions. For the sake of simplicity only a few turns of each cable are shown.

It is now apparent that when the drum is in neutral position between the pulleys 15 and 16, as shown in FIGS. 1 and 2, while the pulleys are rotating, the drum will re main stationary. It is to be noted that the clearance be tween the drum and the pulleys is shown exaggerated in the drawing, as in fact there need be no visible clearance but only insuflicient frictional engagement between the drum and the pulleys to overcome the slippage between the two surfaces owing to the inertia of the drum.

Upon rotating the shaft 12, or rather turning it, in one direction will cause the drum to increase the pressure of engagement with the pulley 15 while decreasing the pressure or increasing the distance of separation of the drum from the pulley 16. Thus, as the pulley 15 works upon the drum to, for example, wind in the cable 33, the drum 19 will simultaneously and synchronously unwind the cable 34. Thus, if the load, not shown, to which the ends of the cables 32 and 34 are attached is, for example, the rudder of a ship through whatever intermediary mechanism required, it is obvious that the rudder may be turned in either direction exactly the distance or arc desired, then stopped and continued in the same direction or reversed, at whatever speed desired, the speed at any given instant being dependent upon the degree of pressure of the drum against a pulley 15 or 16.

If the ends of the cable be attached to opposite ends of a work piece which is, say, to be moved back and forth under control, it is obvious that the same fine degree of control is obtained.

The control of the drum is obtained by the pilot or operator turning the crank 22, in the example illustrated, and thus advancing or receding the drum in one direction or the other. However, in some cases the pilot control may obviously be electrical, pneumatic, or other suitable apparatus, as may be desirable.

Assuming for the sake of simplicity that the control is manual by the operators working the crank 22, it is apparent that he has a fine degree of control over a wide range of speed and movement of the object worked upon by the cables. A very slight degree of turning of the crank will augment the frictional engagement between the drum and a pulley, thus increasing the speed of winding up one cable while simultaneously to the like degree increasing the paying out of the other cable. For most applications the rate of rotation of the shaft 12 will be only a very small fraction of the rate of rotation of the pulleys 15 and 16, so that a skilled or trained operator will have no difficulty in handling the crank to achieve the desired performance of the cables upon the work in question.

FIG. 3 illustrates a modification wherein the drum 19 is shown replaced by a sprocket wheel or gear 35 having suitable axial bosses or hubs extending therefrom for frictional engagement with the pulleys 15 and 16 in the same manner as described above in respect to the drum. The hubs 36 are shown having a substantial axial length, but

of course this would be a matter of choice. A chain 37 trained about the gear 35 may have its two ends, not shown, attached to the object worked upon in the same manner as mentioned above in the case of the cables 33 and 34. Or the gear 35 may be geared to another gear or a train of gears With the final gear of the train, all not shown, operating upon the object worked upon.

In order to minimize the wear between the interengaging surfaces of the drum or gear or the like and the pulleys 15 and 16, each such surface is preferably provided with a face plate or disc, not specifically designated in the drawing, made of suitable wear resistant material which also possesses a low heat conductivity; such materials are available on the market.

It is to be noted that instead of providing extensive interengaging screw threads between the shaft 12 and the rotating member or drum 19, the threads may be replaced by mutually interengaging cam surfaces having a circumferential length of less than one turn. In fact, such cams are equivalent to threads, as is well known.

While the invention has been described with particular reference to the embodiment illustrated in the drawing such is not to be construed as a limitation upon the invention which is best defined in the accompanying claim.

What is claimed is defined as follows:

A reversible drive mechanism comprising a rotatably supported shaft having two spaced driven wheels rotatably mounted thereon at fixed longitudinal positions on the shaft, at least a portion of the shaft between the wheels having a screw thread thereon, a drum mounted on the shaft between said wheels and having an internal screw thread meshing with said thread on the shaft, means for simultaneously rotating said wheels in opposite directions, the end surfaces of the drum being normally positioned close to but spaced from the adjacent surfaces of the wheels, and means for turning said shaft to move the drum axially into frictional engagement with either of said wheels while simultaneously moving the drum correspondingly away from the other of said wheels and for increasing or decreasing the degree of frictional engagement through a range from zero friction to a maximum friction wherein the drum is locked to the wheel.

References Cited in the file of this patent UNITED STATES PATENTS 1,580,840 McVeety Apr. 13, 1926 2,362,262 French Nov. 7, 1944 2,483,950 Watson et al Oct. 4, 1949 2,603,482 Gonzales July 15, 1952 2,641,135 Gosline June 9, 1953 3,044,312 Hall et a1. July 17, 1962 FOREIGN PATENTS 166,615 Austria Jan. 15, 1950

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