WO1979000072A1

WO1979000072A1 - Ratio preserving control system

Info

Publication number: WO1979000072A1
Application number: PCT/US1978/000047
Authority: WO
Inventors: D Pandres
Original assignee: D Pandres
Priority date: 1977-07-28
Filing date: 1978-07-25
Publication date: 1979-02-22
Also published as: EP0006879A1; JPS601602B2; GB2021286B; JPS5425819A; GB2021286A

Abstract

An interlock mechanism for an operating system such as a zoom lens with at least first and second independently controllable operating parameters comprising sending means (11, 12) for generating control outputs which are the logarithmic value to a common base of the actual value of the operating parameter with which each control output is associated and control means (14) responsive to the difference between values of the outputs to change the actual value of one of the operating parameters as the actual value of the other operating parameter is changed to maintain a selected difference between the control outputs so that a selected prescribed ratio is maintained between the actual values of the operating parameters. The disclosure contemplates electromechanical, mechanical and electrical versions of the interlock mechanism.

Description

RATIO PRESERVING CONTROL SYSTEM I. TECHNICAL FIELD

This invention is concerned with maintaining a selected ratio between multiple, independently changeable operating parameters of a control system such as those associated with a camera zoom lens system. These ratios are normally difficult to interrelate, especially where the functional relationship between each control input and its operational parameter is different for the different operational parameters. One instance where it is desirable to interrelate these parameters is the object distance parameter and the focal length parameter of a camera zoom lens in order to keep the image size from the lens system constant even through the distance between the subject being photographed and the lens system varies. II. BACKGROUND ART

It is desirable on occasion to interrelate the normally independently controlled operating parameters of a control system so as to automatically maintain selected ratios between the operating parameters as any one of the parameters is changed. One such control system in which this feature is desired is a zoom lens for a camera where the maintenance of a constant image size is desired even through the distance between the lens and the subject being photographed is changing.

With respect to zoom lens, the prior art has attempted to interrelate the object distance parameter used to focus the lens and the focal length parameter used to zoom the lens through the use of cams with non-logarithmic camming surface so as to maintain a fixed ratio between the object distance parameter and the focal length parameter of the lens. Such systems prevented the zoom lens from teing effectively used as a conventional zoom lens where the object distance parameter is controllable independently of the focal length parameter and also was unable to interrelate the operating parameters at different desired ratios. The prior art has further attempted to permit interrelating the object distance parameter with the focal length parameter by providing an object distance control member whose rotational movement was logarithmic of the actual value of the object distance parameter set by the object distance control member and by providing a focal length control member whose rotational movement was logarithmic of the actual value of the focal length parameter set by the focal length control member. The object distance control member and the focal length control member are rotatably mounted about a common rotational axis so that the operator may manually hold and rotate both control members simultaneously to maintain constant ratios between the object distance setting and focal length setting of the lens. Such systems depended on the ability of the operator to manually hold and turn the control members and required complex internal constructions to correlate the control member movement with the setting of the operating parameter. Such systems also caused a loss of effectively obtainable accuracy in certain settings of the lens. III. SUMMARY OF THE INVENTION According to the present invention, there is provided an interlock mechanism for an operating system with a plurality of independently controllable operating parameters comprising sending means for generating control outputs which correspond to the logarithmic value to a common base of the respective actual values of the different operating parameters; and control means operatively connected to the sending means and responsive to the difference between the control outputs to change the actual values of the operating parameters in response to a change in the actual value of one of the operating parameters to maintain a selected difference between the control outputs so that a prescribed ratio is maintained between the actual values of the operating parameters. Embodiments of the invention are illustrated applied to a camera zoom lens to interrelate the object distance parameter and focal length parameter of the lens without the requirement of special internal lens construction. Electromechanical, mechanical and electrical versions of the interlock mechanism are illustrated. The control means of the interlock mechanism is adjustable to permit different ratios to be selectively maintained between the operational control parameters of the operating system. The control outputs of the electromechanical version of the interlock mechanism are electrical voltages whose values are respectively representative of the logarithmic value to a common base of the actual value of the operating parameter with which the control output is associated. The control means of the electromechanical version includes an adjustment mechanism for selectively adding selected voltage values to certain of the voltage outputs to generate apparent voltage outputs with the control means responsive to any difference between one of the voltage outputs to change the actual value of the operating parameters in respons e to a change in the actual value of one of the operating parameters until one of the voltage outputs equals the apparent voltage outputs so that prescribed ratios are maintained between the actual values of the operating parameters.

The control outputs of the mechanical version of the interlock mechanism are the parallel linear movements of output members where the amount of linear movement of each of the output members corresponds to the logarithmic value to a common base of the actual value of the operating parameter with which the output member is associated. The control means of themechanical version includes interconnecting means for selectively locking the output members together so that movement of one of the output members as its associated operating parameter is changed causes a like movement in the other of the output members to change the operating parameter associated with each so that the selected prescribed ratio is maintained between the operating parameters.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partial side elevational view of a camera zoom lens on which a first embodiment of the invention is incorporated; Fig. 2 is an electrical schematic of the control circuit associated with the invention seen in Fig. 1;

Fig. 3 is a composite graph illustrating the operation of the invention of Fig. 1;

Fig. 4 is a perspective view of a second embodiment of the invention;

Fig. 5 is a plane view of a third embodiment of the invention; and

Fig. 6 is an electrical schematic for the embodiment of the invention of Fig. 5.

V. DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The invention of this application is disclosed as applied to the power zoom lens L_PZ of a movie camera C_M in Figs. 1-3, to a nonpowered zoom lens L_Z of a still camera B_C in Fig. 4 and to a three variable control system in Figs. 5 and 6. The invention can likewise be appl to a wide variety of systems which have two or more. independently variable control parameters. Va. First Embodiment

In Figs. 1-3, the lens L_PZ has a conventional manually operated object distance (focus) control member CM_OD, and a conventional power or manually operated focal length (zoom) control member CM_FL rotatably mounted on lens body B, about lens axis A_L. Camera body B_MC mounts the reversible motor drive unit MDU to selectively power control member CM_FL through gears G_M. An interlock control mechanism 10 with an object distance sending unit 11 and a focal length sending unit 12 controlling a ratio base control unit 14 powered through switch SW_I and adjusted with selector knob 15 automatically maintains any selected ratio between object distance and focal length.

The camming surface 26 on an object distance cam 25 carried by control member CM_OD axially displaces a spring urged drive rod 21 to adjust the movable contact P_OD-M of a linear potentiometer assembly 20 in sending unit 11 via a cam follower roller 24 in roller assembly 22 on drive rod 21 as control member CM_OD is rotated to adjust the object distance parameter and focus lens L_PZ. Similarly, the camming surface 36 on a focal length cam 35 carried by control member CM_FL axially displaces a spring urged drive rod 31 to adjust the movable contact P_FL-M of a linear potentiometer assembly 30 in sending unit 12 via a cam follower roller 34 in roller assembly 32 on drive rod 31 as control member CM_FL is rotated to adjust the focal length parameter of lens L_PZ. The shape of the object distance camming surface 26 is logarithmic of the values of the object distance parameter to which the lens can be set so that the voltage output at the movable contact P_OD-M on potentiometer assembly 20 is the logarithm to common base of the value of the object distance parameter to which the lens is set. Thus, the drive rod 21 is axially displaced a variable distance d from the base object distance reference plane AP_OD over the total distance range d_OD of the camming surface 26 while the drive rod 31 is axially displaced a variable distance d_b from the base focal length object distance plane AP_FL over the total distance range d_FL of the camming surface 36.

The distance d_a is the logarithmic value of the actual value to which the control member CM_OD has set the object distance parameter of the lens while the distance d_b is the logarithmic value of the actual value to which the control member CM _FL has set the focal length control parameter of the lens. The distances d_a and d_b can be determined by the following equations:

where x is any convenient base for the logarithm and where K is a constant. While the actual control parameter values may be used in the calculations, dividing the actual control parameter value by the smallest control parameter value in its operation range facilitates such calculations by allowing the camming surfaces 26 and 36 to start at "0" for graphing purposes. The shape of the camming surface 26 corresponds to the focal length curve in Fig. 3 while the shape of camming surface 36 corresponds to the object distance curve. The shape of the camming surfaces 26 and 36 are also adjusted for any axial movement of the control members CM_OD and CM_FL during adjustment.

As seen in Fig. 2, the control circuit for the interlock mechanism 10 interfaces with the already existing circuitry in the motor drive unit MDU. The conventional motor drive circuitry is seen in the upper portion of the schematic with a battery BAT_C, speed switch SW_SP, a pair of zoom switches SW_ZO and SW_ZI controlled by actuator 45 (Fig. 1), and a reversible drive motor M_FL to selectively rotate control member CM_FL. This circuit is modified by connecting the switches SW_ZOand SW_ZI to motor M_FL through the common contact and the contact shown open in Fig. 2 of selector switches SW_I3 and SW_I2 respectively in gang switch SW_I. Thus, when switches SW_I3 and SW_I2 in Fig. 2 are transferred, the switches SW_ZO and SW_ZI operate motor M_FL in conventional manner.

The ratio control unit 14 is powered by a battery BAT_I through switch SW_I1 to produce a regulated B+ output. The fixed resistance of potentiometer P_OD in sending unit 11 is connected to the B+ output through resistance R2 and to ground through resistance R3. The fixed resistance of potentiometer P_FL in sending unit 12 is connected to the B+ output through potentiometerP_A1 of ganged potentiometer assembly P_A and to ground through potentiometer P_A2 of assembly P_A where control knob 15 operates potentiometers P_A1 and P_A2 so that their effective resistances at any setting sum to the maximum resistance of each potentiometer. The voltage output O_OD at the movable contact of potentiometer P_OD is connected to opposite sign inputs of a pair of comparators CP_I and CP_O while the voltage output O_FL at the movable contact of potentiometer P_FL is connected to the other opposite sign inputs to the comparators. Cross biasing is provided with resistor R4. The output of comparator CP_O drives the coil of relay RY₀ while the output of comparator CP_I drives the coil of relay RY₁. The normally open contacts of relay RY₀ drive the motor M_FL in a first direction through switch SW_I3 while the normally open contacts of relay RY_I drive the motor M_FL in the opposite direction through switch SW_I2

The ganged potentiometer assembly P_A controls the ratio which is to be maintained between the value of the object distance parameter versus the value of the focal length parameter. The comparators CP_I and CP_O drive the motor M_FL to shift the value of the focal length parameter until the voltage output from the movable contact of potentiometer P_FL equals the voltage output from the movable contact of potentiometer P_OD In effect, this is maintaining the apparent difference in the logarithmic equivalent of the object distance value and the logarithmic equivalent of the focal length value at zero as seen by the comparators CP_I and CP_O. In effect, the ganged potentiometer assembly P_A is used to raise or lower the apparent focal length voltage output by a constant amount at each setting of the ganged potentiometer assembly P_A.

Because there is a relationship between the resistive values of the potentiometers P_OD, P_FL, P_A1 and P_A2; and the resistors R2 and R3, choosing the resistive values of the fixed resistances of potentiometers P_OD and P_FL as equal simplifies the determination of the remaining resistive values. The relationship is further simplified when the resistive values of resis tors R2 and R3 are each selected as equal to the resistive value of the fixed resistance of potentiometer P_{O D} or P_FL, and this is the case in this application. For illustration purposes, say the resistive value of the fixed resistances of potentiometers P_OD and P_FL as well as resistors R2 and R3 is selected as "R".

It will be further noted that the fixed resistances of the potentiometers P_A1 and P_A2 are selected as equal to each other to give proper voltage output curve shift. Under these conditions, it will be seen that, if full range of operation of the controls is desired, then the resistive value of each of potentiometers P_A1 and P_A2 is limited to a range of "R" to "2R". In one limiting case, that illustrated in the drawings, the resistive value of each potentiometer P_A1 and P_A2 is selected as "2R" and one end of the fixed resistance in each is left open or unconnected. In the other limiting case (not shown in the drawings), the resistive value of each potentiometer P_A1 and P_A2 would be "R" and those ends of the fixed resistances shown unconnected in the drawings would be shorted to each other. Because selecting the value for potentiometers P_A1 and P_A2 at "R" results in maximum circuit current drain while selecting the value at "2R" resuits in minimum circuit current drain, the value selected in the illustrated circuit is "2R". In the case where the resistive value of potentiometers P_A1 and P_A2 is selected somewhere between the limiting values of "R" and "2R", then some calculated resistance would be placed between the unconnected ends of the fixed resistances of the potentiometers P_A1 and

P_A2.

As seen in Fig. 3, the output O_OD (Fig. 2) of the object distance sending unit 11 is. the voltage equivalent of the logarithmic value of the value to which the control member CM_OD has set the object distance parameter while the output O_FL (Fig. 2) of the focal length sending unit 12 is the voltage equivalent of the logarithmic value of the value to which the control member CM_FL has set the focal length parameter plus the shifted value of the potentiometer assembly P_A. This allows the output O_FL to be appropriately adjusted so that the focal length voltage curve can be matched to any point on the object distance voltage curve.

A better understanding of the significance of the shifted value of the potentiometer assembly P_A can be had by considering a series of postiions to which it is set. Suppose the object distance control member CM_OD is set as seen in Fig. 1 so that the cam follower roller 24 has been shifted the distance da from the base reference plane AP_OD to generate voltage output V_a in Fig. 3. Now, if the potentiometer assembly P_a is set at the desired value, the motor drive unit MDU will shift the focal length control member CMp, until the cam follower roller 34 is shifted the distance d_b from the base reference plane AP_FL as seen in Fig. 1 to generate voltage output V_b in Fig. 3. It will be noted that at this postition, the voltage V_a is equal to voltage V_b as indicated by the phantom line in Fig.

3 labelled P_o . This takes into account the situation in which the potentiometer assembly P_A is set at the desired ratio.

If one wants the ratio to be such that, the voltage output V_b ' on the focal length voltage curve is to correspond to the voltage V_A on the object distance voltage curve, the potentiometer assembly P_A is shifted using the knob 15 until the voltage value V_S is added to the voltage value V_b ' so that the apparent voltage in the output O_FL of the sending unit 12 would be the value V_b illustrated by the shifted dashed line curve in Fig. 3. The value V_S added will be different depending on which points of correspondence on the focal length voltage curve one wants to correspond to the voltage V_a on the object distance voltage curve.

Suppose the potentiometer assembly P_A is set so that the focal length voltage curve is defined by the solid line curve in Fig. 2. Now, if the potentiometer assembly P_A remains in the same position, and the object distance control member CM_OD is rotated to a new position so that its associated sending unit 11 generates a voltage output V_{a s} as seen in Fig . 3 , then the ratio base control unit 14 will cause the motor drive unit MDU to rotate the focal length control member CM_FL so that the voltage output from its associated sending unit 12 will be changed to voltage V_bs where the voltages V_as and V_bs are again equal. This is illustrated by the phantom line seen in Fig. 3 which is labelled P_s.

From the foregoing, it will be seen that the apparent voltage in the output O_FL, is the sum of the voltage attributable directly to the potentiometer P_FL plus the voltage attributable to the potentiometer assembly P_A. This means that the equation voltage P_FL + voltage P_A = voltage P_OD is satisfied. It follows that, based on the above set forth relationships, this equation can be rewritten as

which can be rewritten as

It will be noted that, as long as the potentiometer assembly P_A remains at any one setting, the value K_V also remains constant. Since K, x, smallest object distance, smallest focal length, are all constants, it follows that log [actual object distance/actual focal length] also remains constant as long as the setting of the potentiometer assembly P_A remains constant which implies that

c

Thus, once the potentiometer assembly P_A is set, the ratio of object distance to focal length is maintained constant which is the characteristic desired. It will further be understood that changing the potentiometer assembly P_A to another constant will still cause the ratio to remain constant but to a constant of a different value. This is also a desired characteristic.

It will be further appreciated that the lens L_PZ has two degrees of freedom. The interlock mechanism 10 allows the two control parameters to be interconnected so that the number of degrees of freedom are reduced to one. This greatly simplifies the operation of the lens L_PZ so as to keep the image size constant while the distance between the subject being photographed and the lens changes. Recently, cameras with automatic focusing have been developed. The mechanism 10 can be easily added to these automatic focusing cameras when they are equipped with a zoom lens so that, with the automatic focusing feature, the number of degrees of freedom of the lens system is reduced to zero. Because the power of the electric motor Mp, required to operate the control member CM_FL is relatively low, the control member CM_FL can be manually shifted momentarily by overpowering the motor M_FL if it is desirable to momentarily change the focal length parameter. When the control member CM_FL is released, the motor M_FL will power the control member CM_FL back to its prescribed ratio position for continued operation.

Vb. Second Embodiment

Fig. 4 illustrates a second embodiment that mechanically maintains the desired ratio between focal length and object distance and is applied to a zoom lens L_Z for a still camera B_C. Lens L_Z has an object distance control member CM_OD and focal length control member CMp, mounted on lens body B_L about lens axisA_L.

Interlock mechanism 110 connects members CM_OD and CM_FL to maintain the desired image size. Mechanism 110 has an object distance control cam 111 carried by the control member CM_OD and a focal length control cam 112 carried by control member CM_FL . Cam

111 has a camming slot 121 whose logarithmic relationship with control member CM_OD corresponds to that of camming surface 26 for the first embodiment. Cam

112 has a camming slot 125 whose logarithmic relationship with control member CM_FL corresponds to that of camming surface 36 for the first embodiment. An interconnect unit 14 selectively connects the cams 111 and 112 to maintain desired ratios between the control members CM_OD and CM_FL. Housing 130 of unit 114 is mounted on lens body B_L and slidably mounts cam follower members 131 and 132 for movement along a path R_L parallel to lens axis A_L. The cam followers 131 and 132 can slide in housing 130 independently of each other but can also be locked together using the teeth 144 and 145 on members 131 and 132 and clamp 148 so that the members 131 and 132 move as a unit. It will be noted that the members 131 and 132 can be locked together at any position relative to each other over their respective ranges of movement. The member 131 is drivingly connected to the object distance camming slot 121 through follower 136 while member 132 is drivingly connected to the focal length camming slot 125 through follower 140. Thus, rotation of control member CM_OD axially displaces cam follower member 131 and axial movement of member 131 rotates member CM_OD through slot 121 while rotation of control member CM_FL axially displaces cam follower member 132 and axial movement of member 132 rotates member CM_FL through slot 125. When the cam follower members 131 and 132 are locked togeτ ther, it will be seen that rotation of one of the control members CM_OD or CM_FL causes an appropriate rotation of the other control member CM _OD or CM_FL to maintain a constant ratio between object distance and focal length.

Because the slots 121 and 126 are logarithmic, it will be seen that the displacement da of the cam follower member 131 from the base object distance plane AP_OD over its range d₁, corresponds to that of the first embodiment and that the displacement d_b of the cam follower member 132 from the base focal length plane AP_FL over its range d₂ corresponds to that of the first embodiment. It will be noted that the planes AP_OD and AP_FL are spaced apart a fixed distance d₃. When the cam follower members 131 and 132 are selectively locked together to selectively fix the distance d between the followers 136 and 140 at a constant value, it will be seen that d₃ - d_a + d_b = constant (d_c).

Because of the logarithmic nature of d_a and d_b, this equation can be rewritten as

Since K, x, smallest object distance, smallest focal length, and d, are all constants, it follows that log_x [actual object distance/actual focal length] is also constant which implies that

Thus, once the members 131 and 132 are locked together, the ratio of object distance to focal length is maintained constant so that rotation of the control members CM_OD or CM_FL also drives the other control member CM_OD or CM_FL to keep the ima.ge size constant. Any desired ratio can be maintained between object distance and focal length simply by initially setting the control members at the desired ratio before the cam follower members 131 and 132 are locked together.

Vc. Other Embodiments

While the first two embodiments of the invention are incorporated in control systems having only two degrees of freedom, the invention can be applied to any control system having any number of degrees of freedom. In any such system, each of those control parameters which are sought to be controlled would have sending means for generating an output which is logarithmic of the particular values over the operating parameter range and interlock means for selectively controlling the various control parameters so that selected fixed differences can be maintained between the logarithmic outputs of the sending means.

Figs. 5 and 6 illustrate a control system which has three independent control parameters and thus three degrees of freedom. The control system has its three control parameters controlled by three different control members CM₁-CM₃ where each can be manually adjusted with control knobs CK₁-CK₃ and/or electrically adjusted with motors M₁-M₃. The control members CM₁-CM₃ are illustrated as axially movable along respective paths P₁-P₃.

The interlock mechanism 210 has a separate sending unit 211 connected to each control member CM₁-CM₃ respectively referenced 211₁-211₃. The sending units may be mechanical or electromechanical but are illustrated as electrical by way of example. Sending units 211₁-211₃ generate respective outputs O₁-O₃ that correspond to the logarithm of the operating parameter value associated with the particular sending unit as set by the control members CM₁-CM₃.

As seen in Fig. 6, the output 0, is connected to ratio base control units 214. and 214_B; to comparators 215. and 215_B; and to selector switch 218_A, 218_B and 218_C. Output O₂ is connected to ratio base control units 214_A and 215_C; to comparators 215. and 215_C; and to selector switches 218A, 218B and 218C. Output O₃ is connected to ratio base control units 214_B and 2145_C; to comparators 215_B and 215_C; and to selector switches as 218_A, 218_B and 218_C. The ratio base control units 214 are activated by actuating switches SW which may be ganged to operate together. Closure of switches SW causes the ratio base control unit 214. to generate output O_A to the comparator 215_A representative of the difference between outputs O₁ and O ₂ at the time of closure of switch SW, causes the ratio base control unit 214_B to generate output O_B to the comparator 215_B representative of the difference between outputs O₁ and O₃ at the time of closure of switch SW, and causes the ratio base control unit 214_C to generate output O_C to the comparator 215_C representative of the difference between outputs O₂ and O₃ at the time of closure of switch SW.

Output 0. biases the comparator 215. to generate a compared control output signal S. to selector switch 218. until the difference between outputs O₁ and O₂ matches that indicated by the ratio base control unit 214_A. Output O_B biases the comparator 215_B to generate a compared control output signal S_B to selector switch 218_B until the difference between outputs O₁ and 0, matches that indicated by the ratio base control unit 214_B. Output O_C biases the comparator 215_C, to generate a compared control output signal S_C to selector switch 218_C until the difference between outputs O₂ and O₃ matches that indicated by the ratio base contiol unit 214_C. Switch 218. selectively controls motors M₁ and M₂ , switch 218_B selectively controls motors M₁ and M₃ and switch 218_C controls motors M₂ and M₃. The motors M₁-M₃ can be manually individually controlled through switches OS₁-OS₃. The operator initially sets the value of the operating parameters to the desired ratios and closes the activation switches SW to energize ratio base control units 214_A-214_C and activate the interlock mechanism 210. Now if the setting on one αf the control members is changed, the mechanism 210 will appropriately move the other control members to maintain the set ratio between the operating parameters. For example, assume control member CM₁ is moved to change its operating parameter and change output O₁. The comparator 215. senses a differential between outputs 0, and O₂ different from that set in ratio base control unit 214. and operates motor M₂ through switch 218. to shift member CM₂ until the differential sensed by comparator 215. again matches that initially set in ratio base control unit 214_A. At the same time, the comparator 215_B senses a differential between outputs O₁ and O₃ different from that set in ratio base control unit 214_B and operates motor M₃ through switch 218_B to shift member CM₃ until the differential sensed by comparator 215_B again matches that initially set in ratio base control unit 214_B. Thus, it will be seen that the control members CM₂ and CM₃ have been moved until the operating values controlled thereby have the same ratio as they had initially. It will also be noted that the first changed output O₁-O₃ appropriately enables only those selector switches 218_A-218_C to cause the other motors M₁-M₃ not associated with the first changed output O₁-O₃ to be controlled from the comparators 215_A-215_C. The mechanism 210 may be used to interlock any two of the control members as well as all three as explained above.

It will be noted that the interlocking process need not be a one step procedure, but may be performed in separate steps. For example, a control system with eight independent operating parameters V₁-V₈ would have eight degrees of freedom. One may interlock parameters V₂, V₅, and V₇; interlock parameters V₁, V₃, and V₈ ; and interlock parameters V₄ and V₆ in accordance with the invention. The system would then have three degrees of freedom with the ratios V₂/V₅, V₂/V₇ or V₅/V₇ being constant, the ratios V₁/V₃, V₁/V₆ or V₃/V₆ being constant and the ratio V₄/V₆ being constant. The ratio of the parameters in any one interlocked group to the ratio of the parameters in any other interlocked group may be independently changed as desired. At some later time, any of the three interlocked groups of parameters may be interlocked with any other interlocked group of parameters in accordance with the invention to reduce the system degrees of freedom to two, or all of the interlocked groups of parameters may be interlocked in accordance with the invention to reduce the system degrees of freedom to one.

Claims

1. An interlock mechanism for an operating system including at least a first and second independently controllable operating parameters CHARACTERIZED BY: first means for generating a first output which is the logarithmic value to a common base of the actual value of the first operating parameter; second means for generating a second output which is the logarithmic value to the common base of the actual value of the second operating parameter; and control means operatively connected to said first means and said second means, and responsive to the difference between said first and second outputs to change the actual value of one of the operating parameters in response to change in the actual value of the other operating parameter to maintain a selected difference between said first and second outputs so that a selected prescribed ratio is maintained between the actual value of the second operating parameter.

2. The interlock mechanism of Claim 1 further CHARACTERIZED BY said first and second outputs being electrical voltages whose values are respectively representative of the logarithmic value to a common base of the actual value of the operating parameter with which said output is associated, and wherein said control means is further characterized by adjustment means for selectively adding a prescribed voltage value to said second voltage output to generate a second apparent voltage output, said control means operatively connected to said first voltage output and said second apparent voltage output, and respons ive to any difference between said first voltage output and said second apparent voltage output to change the actual value of the second operating parameter in response to a change in the actual value of the first operating parameter until said first voltage output equals said second apparent voltage output so that a prescribed ratio is maintained between the actual value of the first operating parameter, and the actual value of the second operating parameter.

3. The interlock mechanism of Claim 2 further CHARACTERIZED BY said adjustment means further including means for selectively changing said prescribed voltage value added to said second voltage output to generate said second apparent voltage output.

4. The interlock mechanism of Claim 3 further CHARACTERIZED BY said adjustment means including a ganged potentiometer network.

5. The interlock mechanism of Claim 4 further CHARACTERIZED BY said first means. including a first linear potentiometer having a selectively movable first contact and means for selectively connecting said movable first contact to the first operating parameter so that the voltage output from said movable first contact is representative of the logarithmic value to a common base of the actual value of the first operational control parameter; and said second means including a second linear potentiometer having a selectively movable second contact and means for selectively connecting said movable second contact to the second operating parameter so that the voltage output from said movable second contact is representative of the logarithmic value to a common base of the actual value of the second operating parameter.

6. The interlock mechanism of Claim 5 further CHARACTERIZED BY said control means including a first comparator operatively connected to said first voltage output and said second apparent voltage output; and a second comparator operatively connected to said first voltage output and said second apparent voltage output, said first comparator operational in response to said first voltage output being greater than second apparent voltage output to change the actual value of the second operating parameter until said second apparent voltage output equals said first voltage output and said second comparator means operational in response to said second apparent voltage output being greater than said first voltage output to change the actual value of the second operating parameter until said second apparent voltage output equals said first voltage output.

7. The interlock mechanism of Claim 1 further' CHARACTERIZED BY said first output being linear movement of a first output member and said second output being linear movement of a second output member parallei to the linear movement of said first output member, the amount of linear movement of each of control members with respect to a reference point corresponding to the logarithmic value to a common base of the actual value of the operating parameter with which said control member is associated, said control means including interconnecting means for selectively locking said first and second output members together so that movement of one of said output members as its associated operating parameter is changed causes a like movement in the other of said output members to change the operating parameter associated therewith so that the prescribed ratio is maintained between the operating parameters.

8. An interlock mechanism for an operating system including a plurality of independently controllable operating parameters CHARACTERIZED BY: sending means operatively associated with each of the plurality of independently controllable operating parameters, said sending means generating a plurality of outputs corresponding to the operating parameters, each of said outputs being the logarithmic value to a common base of the actual value of the operating parameter to which said output corresponds; and control means operatively connected to said outputs of said sending means and the plurality of operating parameters, said control means responsive to the change in one of said outputs as the actual value of the operating parameter to which said output corresponds is changed to change the actual values of any of the selected other operating parameters to maintain selected differences between the one of said outputs and the selected of the other of said outputs so that selected prescribed ratios are maintained between the actual values of the selected operating parameters.