US2994877A

US2994877A - Reflector drive mechanism

Info

Publication number: US2994877A
Application number: US555817A
Authority: US
Inventors: Mott Dale H De; Richard B Higley; Frederic F Grant
Original assignee: North American Aviation Corp
Current assignee: North American Aviation Corp
Priority date: 1955-12-23
Filing date: 1955-12-23
Publication date: 1961-08-01
Anticipated expiration: 1978-08-01

Description

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ug- 1, 1961 D. H. DE MoT'r ETAL 2,994,877

REFLECTOR DRIVE MECHANISM Filed Dec.

3 Sheets-Sheet 2 IN VEN TORS. DALE H. DE MOTT RlCHARD B. HIGLEY BY FREDERIC E GRANT ATTORNEY Aug. 1, 1961 D. H. DE MoTT ETAL 2,994,877

REFLECTOR DRIVE MECHANISM Filed Dec. 25, 1955 3 Sheets-Sheet 3 INVENTORS.

By FREDERIC 'E GRANT ATTORNEY United States Patent O 2,994,877 REFLECTOR DRIVE MECHANISM Dale H. De Mott, Los Angeles, Richard B. Higley, Whittier, and Frederic F. Grant, Bellflower, Calif., assignors to North American Aviation, Inc. Filed Dec. 23, 1955, Ser. No. 555,817 11 Claims. (Cl. 343-912) This invention relates to a reflector drive mechanism and, more particularly, to a dynamically balanced drive for a reflector which requires a sine-scan motion and which is to be operated in an aircraft.

The reector drive mechanism is aV motor driven device that drives a radar antenna reflector vertically with respect to a transverse gimbal assembly during the search phase of operation. This mechanism provides an anxiliary scanning motion of the radar beam to more efciently cover a large Search area in a short time. The auxiliary scanning motion, referred to as sine-scan, causes the beam to have an elevation motion that lis sinusoidal. The reector drive mechanism accomplishes the elevation sine-scan by oscillating the reilector in elevation while the transverse gimbal sweeps horizontally.

This invention comprises a double Scotch yoke assembly which, with the reflector, is dynamically balanced, eliminating vibration, and which oscillates the reilector about `its horizontal pivot.

Therefore, an object of this invention is to provide an improved reflector drive mechanism.

A principal object of this invention is to provide a dynamically balanced reflector drive mechanism.

A further object of this invention is to provide a dynamically balanced reflector drive mechanism which employs the principle of the Scotch yoke.

Another object of this invention is to provide a dynamically balanced reector drive mechanism which comprises a modified Scotch yoke.

Other objects of invention will become apparent from the following description taken in connection lwith the accompanying drawings, in which:

FIG. l is a schematic elevational view of a dynamically balanced reflector and reflector drive mechanism cornprised of a double Scotch yoke;

FIG. 2 is a cutaway plan view of a modified Scotch yoke;

FIG. 3 is a view taken along the lines 3-3 of FIG. 2 showing the sine and cosine yokes in side elevation;

FIG. 4 is a view illustrating the geometry of the drive mechanism;

FIG. 5 is an isometric view of the upper drive mechanism employing the modified Scotch yoke;

. And FIG. 6 is a perspective assembly view of the modied Scotch yoke reilector drive mechanism.

Referring to FIG. l, reilector 1 is mounted to be driven in harmonic oscillation about the axis of pivot 2, which is supported by frame structure, not shown. On wheel 3 is mounted stud 4, which is a common stud for Scotch yokes 5 and 6. Scotch yoke 5 is connected to reector 1 by sine link 7 mass 8 above pivot 2. In order to compensate dynamically for the drive of mass 8, eccentric mass or balance weight 9 is located on wheel 3 at a point opposite stud 4. On the lower part of the drawing are shown two

Scotch yokes

13 and 19, having a common stud 22 on wheel 10. Yoke 13 is connected to rellector 1 by sine link 12 below pivot 2 at the lower representative mass point 11. Yoke 19 is Iconnected with yoke 6 by two

cosine links

17 and 18. As on wheel 3, to compensate for mass 11, mass or balance weight 14 is located eccentrically opposite stud 2.2 on wheel 10. The vertical motions of eccentric masses 9 and 14 are compensated by masses or

balance weights

15 and 16 located on links 17 and V18,-respectively,.and the system is, thus, dynamically balanced. Masses '15 and 16 can be incorporated as a single structure, as also can links 17 and 18.

Yokes

5, 6, 13 and 19 are supported by

slides

20, 20a, 21 and 21a, respectively. Motive power provided to turn wheel 3 (or wheel 10) will drive or nod reflector 1 about its pivot 2 via link 7, and wheel 10 is thus driven by link 12 or by

links

17 and 18. The purpose of the Scotch yoke assembly and of the modified embodiment shown in FIGS. 2 and 5 is to convert a rotating shaft motion into two translatory motions. One translatory motion moves the top drive link 7 in a sinusoidal displacement perpendicular to the traverse gimbal, not shown. The other translatory motion moves the cosine bar in cosinusoidal, vertical displacement.

Dynamic balancing in this drive results from three factors: (l) by the symmetry of the two driving points with respect to the reilector mounting axis of the reflector assembly; (2) by a pair of rotating eccentric weights on the main shaft of each mechanism; and (3) by the cosine weights adding to the mass of the vertical or cosine drive link. An interchange of momentum is provided from the reflector to the cosine weights and from this combination it is carried to the rotating weights so that the net reaction of the drive mechanism required to support the support structure is zero for all oscillatory forces. The drive motor, shown in FIG. 6, which is connected to the main shaft of one of the mechanisms, must provide only sulcient torque for overcoming the constant (nonoscillating) friction load.

Referring to FIGS. 2 and 3, in which a modied sinusoidal arid cosinusoidal Scotch yoke is shown in plan, drive crank shaft 26 is xedly mounted adjacent reector 1 on one side of a pivot, such as pivot 2 above. This is an embodiment of the invention developed from the one shown in FIG. l. A similar arrangement is linked to the reflector on the other side of the pivot, as indicated in F-IG. l. An electric motor, not shown, drives crank shaft Z6. v

Eccentric balance weights

29 and 30 are fixedly mounted on journals 26a and 26h, respectively, of crank shaft 26. They produce a fly wheel eiect and compensate for the mass of the reflector, as do the weights 9 and 14, above. The centers of gravity of these weights are on the opposite side of the shaft from the crank throw and pin. Sleeve 28 is mounted for relative rotation on crank pin 31a. Sine yoke or sine pickol bearing 35 and cosine yoke or cosine pickoi bearing 36 are eccentrically mounted on sleeve 28 for rotation with respect thereto. Eccentric inner portions or

races

43 and 44 of

yokes

36 and 35 respectively, and pinion 27 are Iiixedly mounted on sleeve 28 for rotation therewith.

Races

43 and 44 rotate within

yokes

36 and 35, respectively. Thus, the two inner races, the sleeve and the pinion are integral and rotate together relative to the crank pin. Internal ring gear 32 is Xedly mounted and surrounds pinion 27 which is engaged therewith for synchronous rotation on the shaft. The diameter of pinion 27 is half that of internal ring gear 32 and rotates in the opposite direction to crank pin 31a but at the same speed. Similar to the construction shown in FIG. l, sine drive yoke 35 is linked to the reilector on one side of the pivot by sine drive link 47 and 4cosine drive yoke 36 is in position to be connected by cosine drive link 48 to the lower or other pair of yokes which are linked to the reector on the other side of the pivot. In FIG. 2, sine yoke 35 and link 47 are in the position to have moved the reflector to its eXtreme distance toward the axis of shaft 26, and cosine yoke 36 is in its corresponding neutral position. The throw of the eccentric inner part of drive bearing races 44 and 43 (i.e., the distance between the centers of the inner races to the center of the

openings

41 and 42, respectively) is equal to crank throw 31 so that the

geometric centers

33 and 34 of the inner bearing races translate in a straight line during rotation, as illustrated in FIG. 4.

FIG. 4 shows the geometry of the sine and

cosine yokes

35 and 36 and pinion 27 within the internal ring gear 32. Point 32a is the center of ring gear 32 and the point about which the crank throw 31 rotates. The successive points of rotation of the crank throw and the center of pinion 27 are shown by small circles 51 through 57. The squares 61 through 67 present the consecutive positions of a point on the pitch circle of pinion 27 which, as indicated above, is half the diameter of the ring gear. The triangles 71 through 77 represent the positions of a point on the pinion diametrically opposite to the square point. Thus, as the crank is revolved through the positions designated, the sine and cosine pickoifs move through the correspondingly numbered picko points on mutually perpendicular diameters of the internal ring gear to generate sinusoidal and cosinusoidal motion. The sinusoidal motion is indicated by the centers of the squares through which a straight horizontal line could be drawn, and the cosinusoidal motion is indicated by the ycenters of the triangles through which a vertical straight line could be drawn.

FIG. 5 illustrates a designed embodiment of FIG. 2, in an isometric View. Crank shaft 86 is shown to be driven by motor shaft 81 via pinion 82 and gear 83.

Balance Weights

89 and 90 are mounted on the crank pin of shaft 86 to rotate with it. Ring gear 92 is shown surrounding and in contact with pinion 97. Sine drive yoke 8S is eccentrically mounted on a sleeve, not shown, on the crank pin of shaft 86 and has link 87 directed toward the reector, also not shown. Cosine drive yoke 96 is also shown eccentn'cally mounted on the sleeve on the crank pin of shaft 86. Vertically directed on yoke 96 is cosine drive link 88. Vertical balance weight 95, as indicated in FIG. 1 as 15, is shown as a cylindrical plug insert in link 88.V As indicated in the description of FIG. l, link 88 is connected to an identical arrangement, vertically below, on a driven shaft which is linked through a sine drive to the reector on the lower and other side of the horizontal pivot. In the manner indicated above, when drive shaft 86 is rotated, yoke 85 and its link 87 translate a straight line in a fore-and-aft direction, generally parallel to the horizontal, in a simple harmonic sinusoidal motion. Simultaneously in 90 out of phase, yoke 96 and its vertical link 88 translate up and down in a simple harmonic cosinusoidal motion.

Referring to FIG. 6, a perspective view of the reflector and the vertical oscillator drive mechanism are shown in assembly. Reflector 100 and reinforcing ring 101 are mounted on horizontal pivot 102. Drive motor 110 is mounted on traverse gimbal plate 109. Pinion 82 is mounted on motor shaft 81 to drive shaft 86 via gear 83.

The sine and

cosine yokes

85 and 96,

weights

89 and 90 and internal ring gear 92 are enclosed within cylindrical housing 103. Sine drive link 87 is shown extending from cylinder 103 and is connected to reector 100. Extending vertically downward from cylinder 103 is cosine drive link 88 connecting the equivalent driven sine and cosine drive yokes which are enclosed in cylindrical housing 104. On link 88 is indicated the vertical cosine drive Weights 95 which, with

weights

89 and 90 on drive crank shaft 86 in cylinder 103, and with balance Weights equivalent or similar thereto on the driven crank shaft in cylinder 104, complete the dynamical balancing of the entire reector drive mechanism.

By the means described above, the present invention drives a reflector at any required speed or frequency with no adverse vibration reaction on the transverse gimbal. The drive means provided by this invention is of light weight construction and is capable of being adapted in a VSimple manner to allow instantaneous stopping of the motion when power is shut olf to the motor. The power required by the motor is relatively small and steady withcut large transients.

The yoke assemblies are compact, rigid and can be located on the side of the traverse gimbal, as shown in FIG. 6, which permits the placing of critical radar parts in the center. It, therefore, could be useful in other applications where space and weight are problems and noncentered drives are required.

Although this invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

We claim:

1. A yreflector drive mechanism comprising a reector mounted on a pivot having a substantially horizontal axis, oscillating means to pivot said reflector about said axis; said oscillating means comprising a first wheel, a motor means to drive said iirst wheel,-a tirst Scotch yoke connected to said wheel and linked to said reilector, a second Scotch yoke at right angles to and in a plane substantially parallel to the plane ,of said first Scotch yoke and connected to said first wheel, a second wheel, a third Scotch yoke connected to said second wheel and being parallel to said second Scotch yoke, a link between and at right angles to said second and said third Scotch yokes, a fourth Scotch yoke connected to said second wheel and being at right angles to and in a plane substantially parallel to the plane of said third yoke, a link between said fourth yoke and said reector, said horizontal axis interspaced between said links from said yokes to said reflector, and balancing means in said oscillating means whereby said reector is oscllated free from vibration.

2. A reector drive mechanism comprising a pivotally mounted reflector, oscillating means to nod said reiiector about said pivotal mounting; said oscillating means comprising first Scotch yoke motion means having rotating eccentric balancing Weights, said first yoke means linked to said' reflector to translate sinusoidal motion thereto, second Scotch yoke motion means having cosine balancing weights connected thereto, said second yoke means connected -to said irst yoke means to translate cosinusoidal motion thereto whereby there is provided an interchange of momentum from said reector t0 said cosine and said rotating weights so that the net reaction of the drive mechanism to the supporting pivotal structure is zero for all oscillatory forces.

3. A reiiector drive mechanism comprising a pivotally mounted reector, a drive shaft adjacent to said reector on one side of said pivot, motor means to turn said drive shaft, a first yoke mounted eccentrically on said shaft for relative rotation therewith, a first link connecting said first yoke and said reflector on one side of said pivot, a second yoke mounted eccentrically on said drive shaft for relative rotation therewith, `a iirst iixedly mounted internal ring gear surrounding the axis of said drive shaft, a rst pinion mounted on and for relative rotation with said drive shaft within said iii-st ring gear, said first pinion rotatably engaged with said first ring gear, a driven shaft on the other side of said pivot and adjacent to said reflector, a third yoke mounted eccentrically on said driven shaft for relative rotation therewith, a second link connecting said third yoke and said reflector on said other side of said pivot, a fourth yoke mounted eccentrically on said driven shaft for relative rotation therewith, a third link connecting said second yoke and said fourth yoke, a second iixedly mounted internal ring gear surrounding the axis of said driven shaft, a second pinion mounted on and for relative rotation with said driven shaft within said second ring gear, said second pinion rotatably engaged with said second ring gear, and balance weights mounted on said shafts and balance weights secured in said third link between said second and said fourth yokes whereby said reector drive mechanism is dynamically balanced.

4. reflector drive mechanism comprising a pivotally mounted reector, a drive shaft adjacent to said reflector on one side of said pivot, motor means to turn said drive shaft, a plurality of eccentrically mounted rst yokes on said drive shaft for relative rotation therewith, at least one of said first yokes being a sine pickoff linked to said reector on one side of said pivot for the oscillation thereof, at least one of said lfirst yokes being a cosine pickoif, a driven shaft adjacent said reector on the other side of said pivot, a plurality of eccentrically mounted second yokes on said driven shaft for relative rotation therewith, at least one of said second yokes being a sine pickoif linked to said reiiector on said other side of said pivot, one of said second yokes being a cosine pickoif, a first cosine pickoff yoke linked to a second cosine pickoff to impart rotation from said drive shaft to said driven shaft, and balance weights mounted on said shafts and balance weights secured in said linkage between said irst and said second cosine yokes whereby said reflector drive mechanism is dynamically balanced.

5. A reector drive mechanism comprising a pivotally mounted reflector, a drive crank shaft adjacent to said reector on one side of said pivot, motor means to turn said drive shaft, a iirst sine pickotf bearing mounted on said drive shaft for rotation with respect thereto, a first sine drive link connecting said reflector and said rst sine pickoff on said one side of said pivot, a first cosine pickoi bearing mounted on said drive shaft for rotation with respect thereto, a driven crank shaft adjacent to said reflector on the other side of said pivot, a second sine pickoff bearing mounted on said driven shaft for rotation with respect thereto, a second sine drive link connecting said reector and said second sine pickoff on said other side of said pivot, a second cosine pickoff bearing mounted on said driven shaft for rotation with respect thereto, a cosine drive link connecting said first and second cosine pickoffs, and balance weights iixedly mounted for rotation on said shafts and Abalance weights secured in said cosine drive link whereby said reector drive mechanism is dynamically balanced.

6. A reflector drive mechanism comprising a pivotally mounted reflector, a drive crank shaft adjacent to said reflector on one side of said pivot, motor means to tum said drive shaft, a first yoke mounted eccentrically on a crank pin of said drive shaft for rotation with respect thereto, a first link connecting said first yoke and said reector on one side of said pivot, a second yoke mounted eccentrically on said crank pin of said drive shaft, a first Xedly mounted internal ring gear concentrically surrounding the axis of said drive shaft and eccentrically surrounding said crank pin of said drive shaft, a first pinion mounted on said crank pin of said drive shaft within said rst ring gear, said first pinion being rotatably engaged with said first ring gear, said first pinion mounted to rotate with respect to said drive shaft, a driven crank shaft on the other side of said pivot and adjacent to said reflector, a third yoke mounted eccentrically on a crank pin of said driven shaft for rotation with respect thereto, a second link connecting said third yoke and said reflector on said other side of said pivot, a fourth yoke mounted eccentrically on said crank pin of said driven shaft for rotation with respect thereto, a third link connecting said second yoke and said fourth yoke to impart rotation from said drive shaft to said driven shaft, a second xedly mounted internal ring gear concentrically surrounding the axis of said driven shaft and eccentrically surrounding said crank pin of said driven shaft, a second pinion mounted on said crank pin of said driven shaft within said second ring gear, said second pinion being rotatably engaged with said second ring gear, said second pinion mounted to rotate with respect to said driven shaft, and balance Weights mounted on journals of said shafts and balance weights secured in said link between said second and said fourth yokes fwhereby said reector drive mechanism is dynamicallybalanced.

7. A reflector drive mechanism comprising a pivotally mounted reflector, a drive crank shaft adjacent to said reector on one side of said pivot, motor means to drive said shaft, a first internal ring gear iixedly mounted and surrounding a first crank pin of said drive shaft, a first sleeve mounted on said first crank pin for rotation with respect thereto, a first pinion encircling said first sleeve and secured thereto, the diameter of said yfirst pinion being equal to the radius of said lfirst gear, said first pinion being meshed with said -iirst gear for rotation therein, a iirst sine yoke, a first sine inner bearing race tted for rotation within said first sine yoke, said first sine race eccentrically mounted on said first sleeve for rotation therewith, a first sine link connecting said first sine yoke and said reflector on one side of said pivot, a first cosine yoke, a rst cosine inner bearing race fitted for rotation within said first cosine yoke, said -irst cosine race eccentrically mounted on said first sleeve for rotation therewith, a driven crank shaft adjacent to said reector on the' other side of said pivot, a second internal ring gear iixedly mounted and surrounding a second crank pin of said driven shaft, a second sleeve mounted on said second crank pin for rotation with respect thereto, a second pinion encircling said second sleeve and secured thereto, the diameter of said second pinion being equal to the radius of said second gear, said second pinion being meshed with said second gear for rotation therein, a second sine yoke, a second sine inner bearing race 'fitted for rotation within said second sine yoke, said second sine race eccentrically mounted on said second sleeve for rotation therewith, a second sine link connecting said second sine yoke and said reflector on the other Side of said pivot, a second cosine yoke, a second cosine inner. bearing race fitted for rotation Within said second cosine yoke, said second cosine race eccentrically mounted on said second sleeve for rotation therewith, a rst cosine link connecting said first cosine yoke and said second cosine yoke, balance weights eccentrically and ixedly mounted on journal portions of said drive and driven crank shafts, said shaft weights having their centers of gravity diametrically opposite to said crank pins of sald shafts, and a balance weight secured in said cosine link between said cosine yokes whereby said reector drive mechanism is dynamically balanced.

8. A reflector drive mechanism comprising a reflector mounted on a pivot, means to oscillate said reiiector; said oscillating means including a first link mounted for reciprocating translatory movement in a first direction and connected to said reector on one side of the pivot, and a second link mounted for reciprocating translatory movement parallel to said first link, said second link being connected to said reflector on the other side of said pivot, a first and a second rotary drive means eccentrically connected to said first and second links respectively for moving said links in sinusoidal receiprocating translatory motion to oscillate said reflector, said rst and second rotary drive means each having sinusoidal balancing means for balancing the momentum forces of the reflector and the respective link in a direction parallel to the motion of said links on bearings on which the respective rotary drive means are mounted during oscillation of said reflector, and cosinusoidal balancing means connected to and actuated by said rotary drive means for balancing the forces of the sinusoidal balancing means of said iirst and second rotary drive means in the direction normal to said first and second links whereby said reector is oscillated without vibration due to dynamic loading of the bearings of the drive means and the pivot.

9. A reflector drive mechanism comprising a reiiector mounted on a pivot, means to oscillate said reflector; said oscillating means including a first link mounted for 7 reciprocating translatory movement in a first direction and connected to said reilector on one side of the pivot, and a second link mounted for reciprocating translatory movement parallel to said rst link, said second link be# ing connected to said reflector on the other side of said pivot, a iirst and a second rotary drive means eccentrically connected to said first and second link respectively for moving said link in sinusoidal reciprocating translatory motion to oscillate said reector, said first and second rotary drive means having a first and a second eccenrtrically mountedweight respectively for balancing the momentum forces of the reflector and the respective link fina direction parallel to the motion of said links on bearings on which the respective rotary drive means are mounted during oscillation of said reflector, and balancing means connected to and actuated by said rotary drive means for balancing the forces of said first and second eccentrically mounted weights in the direction normal to said first and second links whereby said reector is oscillated without vibration due to dynamic loading of the bearings of the drive means and the pivot.

l0. A reflector drive mechanism comprising a reilector mounted on a pivot, means to oscillate said reector; said oscillating means including a iirst link mounted for reciprocating translatory movement in a rst direction and connected to said refiector `on one side of the pivot, and a second link mounted for reciprocating translatory movement parallel to said rst link, said second link being connected to said reilector on the other side of said pivot, a rst and a second rotary drive means connected to said rst and second links respectively for moving said links in sinusoidal reciprocating translatory motion to oscillate said reflector, eccentrically mounted weights on each of said rotary drive means for balancing the momentum forces of the reector and the respective links on bearings on which the respective rotary drive means are mounted during oscillation of said reflector, a third link mounted for reciprocating translatory motion in a direction normal to said first and second links, said third link being connected to said iirst and second rotary drive means for cosinusoidal translatory motion, said third link having a weight substantially equal to the sum of said eccentrically mounted weights on said rotary drive means, whereby said reilector is oscillated Without vibration due to dynamic loading of the bearings of the drive means and the pivot.

1l. A reector drive mechanism comprising a pivotally mounted reector, and oscillating means to oscillate said reector, said oscillating means including a rotary drive means; at least one reciprocating means connecting said rotary drive means with said reflector, said reciprocating means mounted on said reector ofset from the pivot and on said rotary drive means eccentric from the rotary axis, said reciprocating means movable along a first path; eccentrically mounted weight means mounted on said drive means so as to compensate for the acceleration and deceleration forces of the reciprocating means and reector along said irst path when the reflector is oscillated; and balancing means operatively connected to said oscillating means for compensating for the force components of said eccentrically mounted Weight means along a line extending normal :to said rst path.

References Cited in the le of this patent UNITED STATES PATENTS