US 3419827 A
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3 8, JAMES E. WEBB 3,419,827
ADMINISTRATOR OF THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INDEXING MICROWAVE SWITCH Filed D80. 27, 1966 sheet of 2 I TO FIELD OF I 2 MICRO CONTROL IIAARMATURE a2 SWITCHES ELL "'}TO ARMATURE I fl \mu 3 z II N 4| 26b 1 II 21 a I32 I IIII t zecl MI I. I 2!! II II IIIIIII 3- 26c G iIIL lllllllnllIJIIIIIIIIIIIIIIIIIMIIIIII DAVID L. NIXON FRANK E. MCCREA INVENTORS ATT ORN EYS FIG. 4
Dec. 31, 1968 JAMES E. WEBB 3,419,827
ADMINISTRATOR OF THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION INDEXING MICROWAVE SWITCH Filed Dec. 27, 1966 Sheet 2 of 2 :Ll l l I I 51 INVENTORS DAVID L. NIXON F ANK E. MCLCREA ATTORNEYS POSJI CONTL POS l CONTL United States Patent 3,419,827 INDEXING MICROWAVE SWITCH James E. Webb, Administrator of the National Aeronautics and Space Administration with respect to an invention of David L. Nixon, Arcadia, and Frank E. McCrea, San Gabriel, Calif.
Filed Dec. 27, 1966, Ser. No. 605,099 9 Claims. (Cl. 333-98) The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).
This invention relates to microwave circuitry, and more particularly to a waveguide switch.
A waveguide switch may be defined as an apparatus for control coupling different ports of waveguides so that energy may propagate therethrough. In the simplest form, such a switch includes a stationary member which defines the waveguide ports such as one inlet and two outlets. A movable or rotatable member, hereafter also referred to simply as the rotor, includes a waveguide section or channel which is positionable in either of two positions. In one position the channels ends are aligned with the inlet and one of the outlets while in the other position the channels ends are aligned with the inlet and the other outlet. Thus, the inlet is controllably coupled to either of the two outlets. More complex switches may include more than three ports and more than one channel so that at any given fixed position of the rotor, different ports are intercoupled by different channels.
One of the major disadvantages of prior art switches is the need to periodically service the switch to insure proper alignment of the rotor with respect to the ports, so that at any fixed rotor position the rotors channel or channels are properly aligned with a different pair or pairs of ports. The misalignment can be generally attributed to the manner in which the rotors of prior art switches are switched or rotated from one position to the other. Generally, a high peak torque, during a very short period is applied to the rotor to abruptly switch it from one position to the other. A Geneva cam mechanism is one example of arrangements used in the prior art.
The abrupt change in the rotors position results in excessive high forces between the rotor and the stationary member which result in excessive wear of the various parts. In particular, the slamming action produces misalignment of the rotor at the fixed positions, resulting in improper alignment of the rotors waveguide channel with the stationary parts, causing undesired radiofrequency (RF) energy losses. These misalignments are corrected by periodically servicing the switches, which is often most undesirable, especially when the switches are part of a remote radar installation, or where the servicing of the switches inconveniently disrupts continuous operation.
Accordingly, it is an object of the invention to provide a new waveguide switch which is not limited by prior art limitations.
Another object is to provide a simple waveguide switch which requires minimal maintenance.
A further object is the provision of a waveguide switch in which the change of position of the rotor is controlled to minimize wear on the switchs related waveguide sections.
Still a further object is to provide a new relatively simple switch in which the change in position of the rotor is controlled to minimize misalignment of the rotor with respect to the switohs waveguide parts and thereby minimize RF energy losses.
These and other objects are achieved by providing a waveguide switch in which the rotational position of the rotor is controlled by means of a cam follower, extending from the rotor in a direction parallel to its axis of rotation and displaced therefrom. The switch includes a cylindrical cam, rotatable about an axis of rotation perpendicular to the axis of rotation of the rotor. The cams cylindrical surface defines a modified spiralling groove in which the cam follower is inserted. The orientational characteristics of the groove are controlled, so that irrespective of a constant rate of rotation of the cam provided by a motor, the rate of change in laterial position of the cam follower is not constant. More importantly, the rate of rotation of the rotor is controlled so that the rotor rotates gradually, rather than abruptly, toward each of its fixed positions and remains in such position despite any backlash, caused by suddently stopping the motor. As a result, proper alignment of the rotor can be maintained over a very large number of operational cycles and thereby minimize the maintenance requirements. Also, the smooth, gradual rotation of the rotor minimizes any wear between the stationary and the rotatable waveguide sections of the switch.
The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:
FIGURE 1 is a front side view of one embodiment of the novel waveguide switch of the present invention, with a portion of the exterior surface removed;
FIGURE 2 is a cross-sectional view along lines 22;
FIGURE 3 is a simplified two-dimensional diagram of the groove defined in the cam utilized in the novel switch of the present invention to control the rotational characteristics of the switchs rotor;
FIGURE 4 is a block and schematic diagram of control circuitry of the waveguide switch of the present invention actually reduced to practice in one embodiment thereof.
Attention is now directed to FIGURES 1 and 2 wherein a waveguide switch 11 is shown comprising a stationary member 12, hereafter also referred to as the stator and a rotor 14 mounted therein. The rotor is rotatable about an axis of rotation designated by numeral 15. The stator 12 defines a purality of ports designated by numerals 16 through 19, each associated with a waveguide type flange designated by 16 through 19 respectively. The flanges may be welded or fastened by any conventional means to the exterior of stator 12 so that any conventional waveguide section may be coupled thereto to supply microwave energy to any of the ports or receive energy therethrough.
In the particular arrangement shown in FIGURES 1 and 2, the rotor 14 is shown defining waveguide sections or channels, 21 and 22, each section being aligned with two of the stators ports. As is appreciated, the function of each rotor channel is to provide a path for microwave enery to propagate between the two ports with which is the aligned, while the basic function of the switch is to control the rotational position of the rotor so that any pair of ports are in communication by means of one of the channels so that energy may propagate therebetween.
The rotor 14 is provided with rotational forces by means of a cam follower 25 (FIGURE 1) which is located in a groove 26 of a cylindrical cam 28. The cam follower in essence comprises a member extending from rotor 14 in a direction prependicular to the axis of rotation 15, while being displaced therefrom, while cylindrical cam 28 is mounted on a shaft 30 which defines an axis of rotation prependicular to the axis 15 of rotor 14. A reversible motor 32 is coupled to shaft 30 by means of reduction gears 34 and 35, to provide rotational forces to the shaft 30 so as to rotate the cam 28 in either a clockwise direction, as indicated by arrow 36, or in a counter-clockwise direction as indicated by arrow 37.
As is appreciated by those familiar with the art, if groove 26 were shaped in the form of a conventional spiral the rotation of rotor 14 will be directly related to that of cam 28 and, therefore any backlash of reversible motor 32 will affect the positioning of rotor 14. However, in accordance with the teachings of the present invention, the shape of groove 26 is in the form of a modified spiral in which the groove is spirally shaped between flat groove portions, which are oriented in directions prependicu lar to the axis of rotation of the cam. The shape of the groove 26 is diagrammed in a single plane in FIGURE 3 to which reference is made herein. For the particular embodiment described herein, in which the rotor 14 is to be positioned in either of two rotational positions, the groove 26 defines two straight portions 26a and 26b, each having a directional orientation which is perpendicular to the axis of rotation on the cam, or parallel to the axis of cam follower 25. Thus, as long as the cam follower is located in either of the straight groove segments, the rotor is in a stationary position, irrespective of slight rotational movement of a cam. Only when the cam follower is located in a sloping or S-shaped segment 260 of groove 26 is lateral motion supplied to the cam follower which is in turn converted to rotational motion of rotor 40. The slope of segment 26c is controlled so that the rate of rotation of rotor 14 varies as the rotor is rotated from one fixed rotational position to the other. For example, as seen in FIGURE 3, the slopes of segment 26c adjacent segments 26a and 26b is less than the slope along the center portion thereof so that the rates at which rotor 14 rotates when cam follower 25 is in groove segment 26c varies as a function of the slope thereof.
In practice, the rotor 14 is rotated and positioned so that channels 21 and 22 are properly aligned with respect to the stators ports. Then, cylindrical cam 28 is positioned on threaded shaft 30 and secured thereon by means of one or more set screws 41, with the cam follower 25 located substantially in the center of any of the straight segments of the groove which define the fixed rotational positions of the rotor. To change the position of the rotor, motor 32 is energized to thereby rotate cam 28 to provide rotary motion to scam-follower 25 and thereby cause the rotation of rotor 14 to turn to a new position.
Due to the varied slope of segment 260, the rotor tends to accelerate gradually from a present position and thereafter move more rapidly towards the next position with the subsequent lower slope of segment 26c, enabling the rotor to decelerate into a subsequent position, which is defined by the subsequent straight groove segment in which the cam follower 25 is located. For example, let us assume that with cam follower 25 in segment 26a of groove 26, the rotor 14 is in the position shown in FIG- URE 2 defining a rotor position 1 and a clockwise rotation of cam 28 produces clockwise rotation of rotor 14 as indicated by arrow 42 (FIGURE 2). Then, from the foregoing, it should be appreciated that as long as cam follower 25 remains in groove segment 26a, as the cam is rotated the rotor remains in the position shown in FIGURE 2 with the two channels still aligned with respect to the four ports. Only when came 28 has rotated clockwise sufiiciently for segment 26c to engage cam follower 25, upward lateral motion is provided the cam follower, which starts turning rotor 14 in a clockwise direction. However, the initial turning is quite gradual due to the lower slope of segment 26c adjacent segment 2611. Then, as the cam continues to turn, the rate of rotation increases due to the increased slope of segment 260. Then, as the cam continues to rotate and cam follower 25 is located towards the upper portion of segment 260 where the slope thereof is again lower, the rate of rotation of the rotor decreases again. until the am follower 25 enters the straight segment 26b of the groove, at which time the rotor is secured in its other fixed rotational position, whereby channel 21 couples ports 17 and 18 and channel 22 couples ports 16 and 19 defining a rotor position II. Any additional coasting of cam 28 will not effect the accurate positioning of the rotor since the cam can continue to rotate a portion of a cycle without effecting the position of the rotor as long as cam follower 25 is in the straight portion of groove segment 26b. In FIGURE 3, double arrow 45 represents the range of lateral motion of cam follower 25 as a function of its location in any point along groove 26.
From the foregoing, it should thus be appreciated that by providing a cylindrical cam, with a modified spiral groove, which is assumed to represent a groove having at least two straight segments and a spiralling segment of controlled slope, the rotor 14 may be rotated from one fixed rotational position to another without excessive high forces. Rather, the change in position of the rotor is gradually accomplished with the rotor gradually accelerating as the rotor is turned from one position to the other, as well as gradual deceleration when the rotor finally reaches a subsequent rotational position to which it is switched. Also, by providing the straight groove segments, such as 26a and 26b, any effects of motor or gear backlash on the final position of the rotor is eliminated, since slight rotation of the cam may be tolerated without efiecting the rotors position. Thus, rotor positioning problems are greatly simplified, reducing the maintenance problems considerably.
The operation of the novel waveguide switch of the present invention is greatly enhanced by the use of a control circuit, shown in FIGURE 1 by a block 55 and schematically diagrammed in FIGURE 4, to which reference is made herein, and a plurality of microswitches designated, S1 through S5. Motor 32 is assumed to be a 'DC reversible motor and is shown comprising a field winding 32 and an armature winding 32a. Circuit 55 includes diodes CR1 through CR4, arranged in a full wave rectifying bridge to rectify current from an AC source (not shown) for winding 32a, while a diode bridge CR5 rectifies the current for the field winding 32f.
Circuit 55 also includes multicontact relays K1 through K4 and an input plug on board I 1. The relays K1 and K4 are shown in their deenergized state, and the switches are shown when the rotor 12 is in position I. In addition, the waveguide switch includes a cam plate 52a which defines a groove 52d. In practice plate 52a is positioned on cam 28 (FIGURE 1) so that whenever cam follower 25 (FIGURE 1) is in either straight segment 26a or 260, i.e. the rotor 12 is in either position I or II, the normally closed (NC) contact of S5 is closed (as shown). The waveguide switch also includes cam plates 52b and 52a which define lobes 52c and 52 respectively. Plates 52b and 520 are mounted on rotor 12 and adjusted so that when the rotor is in position I lobes 52c and 52 activate switches S1 and S4, respectively (as shown), while switches S2 and S3 are activated by lobes 52c and 52 respectively, when the rotor is in position II.
As previously stated, J1 in FIGURE 4 represents an input plug or board for circuit 55. Alternating current (AC) from an AC source (not shown) is supplied through terminals A and B of J1. Terminal B of I1 is used to supply a control signal to switch the rotor to position 11, designated POS H CONTROL, while terminal C is used to provide a control signal to switch the rotor 12 to position I, designated POS I CONTROL. Terminal F is connected to a lamp 57 which is energized when the rotor 12 is in position I, while terminal H is connected to another lamp 58 which indicates when energized, that the rotor 12 is in position H. In FIGURE 4 assumed to represent the element when rotor 12 is in position I, lamp 57 is energized, since AC current is applied thereto through terminal A of J 1, the normally-closed contact of S5 and the normally open-contact S4.
To switch the rotor 12 from position I, as shown, an AC control signal on J1-E completes the return circuit of K3 and K4 close to supply power to the other side of the armature winding rectifier CR5. Contacts 1, and 4, and 5 and 8, on K3 open to remove dynamic loading resistance, represented by R1, from the armature winding 32a. Closure of contacts 1 and 3, and 8 and 6, on K3 permit current from the armature rectifier bridge formed by CR1CR4 permit current from the armature rectifier to be applied to the armature winding 32a through contacts 5 and 8 on K1. The polarity of the current is such that the motor will cause the rotor 12 to be rotated in the clockwise (CW) direction. As movement starts, normally-open contact of S5 closes, producing through contacts 1 and 4 of K1 and 1 and 3 of K4, holding current for relays K3 and K4. Movement continues until the rotor 12 reaches position II, when the normally-closed contact of S5 closes again. Also, normally-open contact of S2 closes. As the result, the holding current for relays K3 and K4 is interrupted, causing the relays to drop out. Resultant openings of contacts 1 and 3 on K3 disconnects the armature winding 32a from the armature rectifier (CR1CR4). At the same time, when K3 is deenergized, R1 is again connected across the armature winding to provide dynamic braking, through closure of contacts of 1 and 4, and 8 and 5, on K3. Simultaneously, with the stopping of the rotor 12 at position II, the normally-open contact of S3 closes, providing AC current from J1A and through S5 to lamp 58, connected to Jl-H to indicate that the rotor 12 is in position II.
When the rotor is in position II, the normally-closed contacts of S2 are open, disabling position II control input through J1E. The normally-closed contacts of S1 are closed, to connect the return side of the coils K1 and K2 to the position I input control at ]1C. Completion of the return circuit (position I control signal) at the microwave switch control assembly causes K1 and K2 to be energized. When this occurs, closure of contacts 8 and 6 on K2 applied input power to the armature rectifier (CR1-CR4), and opening of contacts 8 and 5 on K1 disconnects one side of R1 from the armature winding 32a. Closure of contacts 6 and 8, and 1 and 3, on K1 connects the armature winding, causing the motor to operate. Under these conditions, the polarity of the current from the armature rectifier (CR1CR4) applied to the armature winding is opposite to that when operation to switching position I] was initiated. Thus, the rotor is turned to position I.
From the foregoing, it should be appreciated that relays K1-K4 and the microswitches Sl-SS can be advantageously employed to control the rotation of the rotor 12 from one position to another, as well as indicate at which position the rotor i positioned. The use of One microswitch, S5, which is activated whenever the cam follower 25 (FIGURE 1) is in a straight portion of the cam groove, i.e. whenever the rotor is in either position and a second microswitch such as S1 used to control the rotation of the rotor to position I, and S2 for controlling the rotation to position II greatly enhances the accuracy with which the rotors position can be controlled with relatively simple microswitches and relays. Also, the manner in which the microswitches and relays are interconnected, when the rotor is in position I, terminal C of I1 is in essence disconnected from the circuit 55 so that a control signal to switch the rotor to position I has no effect. Similarly, S2 prevents a position II control signal at I 1-15 from affecting the circuit when the rotor 12 is in position II. In addition, the use of S5 and S3 and S4 to energize the position-indicating lamps 57 and 58 is most desirable for position display purposes.
Although, in the foregoing. the novel waveguide switch of the present invention has been described in conjunction with a rotor defining two channels rotatable by 90, to be positioned in either of two positions I or II, it should be appreciated to those familiar with the art, that the invention need not be limited thereto. Rather, the rotor may include any number of desired channels, each one of which may be in communication with a pair of ports at each of the rotors rotational positions. Also, the cams groove may be shaped to include any number of fixed rotational positions of the rotor, so that whenever the cam follower 25 is urged into a straight segment of the groove by cam 28 being rotated about its axis of rotation, the rotor is in one of the desired channels, each one of which may be in communication with a pair of ports at each of the rotors rotational positions. Also, the cams groove may be shaped to include any number of fixed rotational positions of the rotor, so that whenever the cam follower 25 is urged into a straight segment of the groove by cam 28 being rotated about its axis of rotation, the rotor is in one of the desired positions. As herebefore indicated, microswitches may be provided to activate and deactivate motor 32 whenever cam follower 25 is in any of the straight groove segment to inhibit the continuous rotation of the cam and the subsequent altering of the rotors position until it is desired to rotate the rotor to another of its fixed positions.
There has accordingly been shown and described herein a novel waveguide switch in which the rotational positions of the switchs rotor are controlled by means of a cam follower following a cylindrical cam which defines a modified spiral groove, whereby the gradual or coasting rotation of the rotor from one fixed position to another may be achieved. It is appreciated that those familiar with the art may make modifications and/or substitute equivalents in the arrangements as shown without departing from the true spirit of the invention. Therefore, all such modifications and/ or equivalents are deemed to fall within the scope of the invention as claimed in the appended claims.
What is claimed is:
1. In a waveguide switch of the type having a stationary member comprising a plurality of waveguide ports, a rotor having an axis of rotation and defining at least one waveguide channel threthrough, a source of energy for rotating said rotor to selected rotational positions, whereby at each position said channel is aligned with another pair of ports, improved means for controlling the rotation of said rotor from one position to another comprising:
a cam having an axis of rotation;
means coupling said cam to said source of energy for rotating said cam about its axis of rotation, said cam defining a modified spiralling groove about its surface; and
control means including a cam follower rotor, frictionally engaging said cam in the groove thereof to control the rotation of said rotor, as a function of the rotation of said cam and the shape characteristics of said groove.
2. The waveguide switch defined in claim 1 wherein the axis of rotation of said cam is substantially perpendicular to the axis of rotation of said rotor and the directional orientation of said groove with respect to an axis perpendicular to the cams axis of rotation is controlled to control the manner of rotation of said rotor from one rotational position to another.
3. The waveguide switch defined in claim 2 wherein at least one segment of said groove is in a direction perpendicular to the cams axis of rotation defining a straight groove segment to inhibit the rotation of said rotor when the cam follower extending therefrom is located in said straight groove segment, the ends of the channel in said rotor being aligned with a pair of ports in said stationary member when the cam follower is in said straight groove segment which is perpendicular to the cams axis of rotation.
4. The waveguide switch defined in claim 3 wherein said rotor defines a plurality of channels, said groove defining a plurality of substantially parallel straight groove segments each perpendicular to said cams axis of rotation, each straight groove segment defining a rotational position of said rotor in which the ends of each channel are aligned with another pair of ports, when the cam follower is located therein, said control means including a control for controlling the rotation of said cam to control the rotational position of said rotor.
The waveguide switch defined in claim 4 wherein the slope of the groove segment between parallel segments is controlled to control the rotation of said rotor as it is rotated from one rotational position to another.
6. A waveguide switch comprising:
a stator defining a plurality of waveguide parts;
a rotor defining an axis of rotation about which said rotor is rotatable, said rotor mounted in said stator, defining at least one waveguide channel having first and second ends; and
positioning control means coupled to said rotor for controlling the rotational position thereof whereby each end of said channel is aligned with one of said waveguide ports; said positioning control means including a cam rotatable in either of opposite directions about an axis of rotation which is perpendicular to the axis of rotation of said rotor, said cam defining a modifier spiralling groove about its surface, said groove comprising of first and second straight groove segments perpendicular to the axis of rotation of said cam and a substantially S-shaped segment connecting said first and second straight groove segments, means for controllably rotating said cam in either of said opposite direction; and a cam follower extending from said rotor and engaging said cam in the groove thereof whereby said rotor is rotated as a function of the rotation of said cam, said rotor being in a first rotational position with the waveguide channel ends aligned with a first pair of waveguide parts when the cam follower is in said first straight groove segment and rotor being in a second rotational position with the ends of said waveguide channel being aligned with a second pair of waveguide ports.
7. The waveguide switch as recited in claim 6 wherein said means for controllably rotating said cam includes a reversible motor, means coupling said motor to said cam: and switching and relay means responsive to a first control signal when said rotor is in said second position to energize said motor to rotate said cam unti-l said cam follower is in said first straight groove segment, defining said first position, said switching and relay means being further responsive to a second control signal.
8. The waveguide switch as recited in claim 7 wherein said switching and relay means include a first microswitch activatable when said came follower is either in said first straight groove segment or in said second straight section and second and third microswitches, said second switch being activatable when said rotor is in said first position and said third switch being activatable when said rotor is in said second position, said second and third swtches controlling the response of said switching and relay means to said first and second control signals, respectively.
9. The waveguide switch as recited in claim 8, further including first and second position indicating means which are coupled to said switching and relay means and energized when said rotor is in said first and second positions, respectively, to indicate the rotational position of said rotor.
References Cited UNITED STATES PATENTS 178,441 6/1876 Houghtaling et al. 74569 2,999,213 9/ 1961 Olivieri et al.
HERMAN KARL SAALBACH, Primary Examiner. LOUIS ALLAHUT, Assistant Examiner.
US. Cl. X.R.