Device for producing electrical signals by means of a control stick
United States Patent [191 Pocker et al.  
 [ 51 Apr. 29, 1975 1 DEVICE FOR PRODUCING ELECTRICAL SIGNALS BY MEANS OF A CONTROL STICK [75] Inventors: Erwin Pocker, Feldolling; Gert Grundmann, Westerham. both of Germany [73] Assignee: Messerschmitt-Blokow-Blohm GmbH, Munich, Germany 22 Filed: Jan. 31, 1974 21 Appl. No.: 438,288  
 [30] Foreign Application Priority Data 3,190,131 6/1965 Daubcrt. Jr... 250/231 R X 3.223.846 12/1965 Rochester 250/230 3,513,247 5/1970 Anderson et al. 250/234 X 3,521,072 7/1970 Wipson ct al. 250/231 R Primary Examiner walter Stolwein Attorney, Agent, or Firm-McGlew and Tuttle [57] ABSTRACT A device for producing electrical signals, comprises a control stick which is pivotally mounted for back and forward movement intermediate its length. One end of the control stick, for example the bottom end, is provided with a source of luminous radiation adjacent this end, and the stick is biased into a neutral position, for example a central position, by means of spring elements engaging it from respective opposite sides. The apparatus includes at least four fixed photosensitive cells which are disposed symmetrically about the radiation source. Two of each of the photosensitive cells are connected to each of two circuits of an electrical transmission means which comprises two electrical circuits. The source of radiation is advantageously surrounded by a screen which is secured to the control stick for movement therewith. Preferably, two photosensitive cells are disposed at mutually opposed locations and connected in a common circuit with the cells disposed in one plane and the cells disposed in the opposite plane being mounted in opposition to each other.  
 9 Claims, 5 Drawing Figures DEVICE FOR PRODUCING ELECTRICAL SIGNALS BY MEANS OF A CONTROL STICK BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates in general to the construction of control devices and, in particular, to a new and useful device for producing electrical signals by means of a control stick.  
 2. DESCRIPTION OF THE PRIOR ART Control devices are known which include a pivotal control stick for effecting the transmission of control signals. With the known type of devices, the control signals produced by varying the inclination of the control stick are used for controlling the movement and position of hoisting units and machine tools or for the remote control of aircraft surfaces, for example. Control and steering operations of this kind require a sensitive actuation, if possible, with a complete elimination of inertial forces and an immediate response of the system to any change in the position of the control stick.  
  In a known remote control device for automatically moving bodies, a tilting of the control stick provided results in the adjustment of two potentiometers which are disposed in two control planes perpendicular to teach other. The control voltages, which are transformed into remote control signals corresponding to the control planes, are a function of the control stick position and are tapped off of the potentiometers.  
  Such a device has several drawbacks. From the mechanical point of view, there must be provided a certain minimum size if a statisfactory precision is to be obtained. Limits are therefore set in respect to miniaturization of such a system. Further, potentiometers permit voltage variations only in steps. They also have the disadvantage that a permanent use leads to abrasion and consequently corrosion of the sliders and turns, reducing the life of these parts and increasing the contact resistances with the necessiity of frequent adjustment as a reslt.  
 SUMMARY OF THE INVENTION The present invention provides an easily operable control stick unit of small size wherein voltages, approximately proportional to the angular position of the control stick, are delivered as control signals to a control device connected thereto and, during the operation, the mechanical wear of the parts is maintained at a minimum. In accordance with the invention, this problem is solved by providing a source of luminous radiation mounted on one end of a pivotal control stick, and at least four fixed photosensitive cells which are disposed symmetrically about the source of radiation, with two each of said cells being connected in each one of two separate electrical tranmission circuits.  
  In one embodiment of the invention, the source of radiation is surrounded by a screen which is secured to the control stick and the photosensitive cells are disposed so that, in the neutral mid position of the control stick, they extend parallel to the axis of the stick and their bottom edges are flush with the bottom edge of the screen.  
  In another embodiment of the invention, the screen is omitted and the photosensitive cells are directly exposed to the source of radiation and located in planes forming an angle with the axis of the control stick in mid position.  
  The invention further provides a circuit arrangement for the electrical part of the control stick unit in which two of the photosensitive cells are opposed to two others, and each two are connected in a common circuit and mounted electrically in opposition to each other.  
  Theinvention has many advantages with respect to the prior art. In the first place, the simple construction of the control stick, which requires no intermediate mechanical parts for producing the variable control voltages, permits a simple adaptation to the desired value of the controlvoltage. Thus, for special purposes, it is possible to provide a miniaturization of the parts in a solid state construction which has not been feasible with the known control stick units heretofore. Because the control stick is the single mobile part in the device and the source of radiation mounted thereon can be operated with undervoltage, the unit requires substantially no maintenance. The actuation of the control stick &#39;is not hindered by any mechanical transmission member so that the ease of manipulation can be adjusted at any time to the desired degree by adjusting the springs retaining the stick in the neutral mid position. The photosensitive cells may be selected in accordance with the problem to be solved. At voltages of about 3 to 4 v and more, it is preferable to use photo-emissive cells. These cells are&#39;connected into the circuit with the working voltage applied thereto and are conductive only when irradiated. Their conductivity attains a certain saturation at which the full applied voltage can pass through and may be collected.  
  It is also possible, however, to use photoconductive cells producing the voltage themselves so that only the current for the source of radiation is to be supplied from a small battery. The desired voltage value may also be predetermined by choosing not only the type but also the quantity of the photocells disposed in each plane. Another advantage is the fact that the voltage variation as a function of the stick inclination can be influenced by selecting an appropriate source of radiation. For example, with a luminous source having the lamp bulb flattened on the front end, a more flattened voltage rise will. be obtained at small angles than at large angles of inclination of the stick, which is desired for some purposes. Possible variations in the brightness of the luminous source can be made ineffective by adjusting the saturation limit of the photosensitive cell to the smallest brightness range. Thereby, a completely uniform collection of light and, consequently, delivery of voltage is obtained irrespective of the direction in which the stick has been tilted.  
  Accordingly, it is an object of the invention to provide a device for producing signals which includes a control stick which is pivotally mounted intermediate its length and which may be pivoted to effect the transmission of control signals through a transmission means which includes two electrical circuits, the stick being biased into a netural position and being provided with a source of luminous radiation on an end which is spaced from the pivotal mounting thereof which is surrounded by at least four symmetrically arranged photosensitive cells With two of each of these cells being connected in respective ones of the two circuits.  
  A further object of the invention is to provide a device for producing signals which is simple in design, rugged in construction and economical to manufacture.  
  For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.  
 BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:  
  FIG. 1 is a transverse sectional view through a control device constructed in accordance with the invention;  
  FIG. 2 is a view of the control device of FIG. 1 shown in an operative position;  
  FIG. 3 is a view similar to FIG. 1 of another embodiment of the invention;  
  FIG. 4 is a circuit diagram for one tilting plane of the control stick; and  
  FIG. 5 is a view similar to FIG. 1 of another embodiment of the invention.  
 GENERAL DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings in particular, the invention embodied therein in FIG. 1, comprises a control device, generally designated 50, which, for example, may comprise a control mechanism for operating the surfaces of an aircraft and which includes a control stick 1 in the form of a double armed lever which is pivotally mounted in a pivot bearing or gimbal mounting 2 on a top wall of a container or frame 3. The bearing 2 is ad vantageously a universal bearing and permits the control stick 1 to be tilted by an angle a in all of the planes which pass through the axis of the control stick 1. The control stick is held in a neutral position, in this case a central position, by four separate springs 4, which are connected intermediate the length of a top arm portion la of lever l and frame 3 at four locations which are spaced on frame 3 at 90 from each other. Springs 4 constitute biasing means for biasing stick 1 into a netural position.  
  In accordance with the invention, the control stick 1 also includes another end portion or bottom end portion lb which carries a luminous source 5 at a spaced location from the pivotal mounting 2, for example, at the bottom end. Luminous source 5 is supplied with electric current by a connection extending through the stick, which has not been shown. At least four separate photosensitive cells 7a to 7d are arranged at equally spaced locations from the luminous source in a fixed position inside of the frame 3 with their bottom edges flush with the bottom edge of a screen 6 which is positioned around the lower end of control stick 1. Photosensitive cell 7d, which is opposite to cell 70, shown in FIG. 2 is not indicated. In the embodiment shown, at least four photosensitive cells 7 are provided, but a number more than 4, for example 8, 12 or even more, may be used for producing higher voltages.  
  The embodiment shown in FIG. 3 comprises a control device, generally designated 52, which includes a control stick or double armed lever 1&#39;, which is pivotally mounted on a universal joint 2 and is biased into a neutral position by springs 4, similar to the embodiment shown in FIG. 1. In the construction shown in FIG. 3, the luminous source comprises a lamp 10, which is located on the arm portion lb of control stick or double armed lever 1&#39;. Lamp comprises a rounded glass bulb which irradiates the photosensitive cells 70&#39;, 7b, 7c and 7d, but without a screen interposed therebetween. Cells 7 are mounted so as to be inclined with respect to the axis of the control stick in the neutral position.  
  FIG. 4 shows a circuit diagram arrangement which includes a possible series connection of the photosensitive cells 7a and 7b which, for example, may also be photo-emissive cells and thus connected in a circuit to which a working voltage is applied. Positive voltage is applied to terminal 20 and a negative voltage is applied to terminal 21. Balancing resistances 22 and 23 are provided between the photo-emissive cells 7a and 7b, permitting a precise fixing or shifting of the starting point of the voltage increase. Between the balancing resistances 22 and 23, a load resistance 24 is connected in parallel to the two cells 7a and 7b. The signal voltage for a control device (not shown) is collected between terminals 25 and 26 which are located at the two ends of the load resistance 24. Outside of terminal 25, the circuit is closed through a ground terminal 27.  
  In the circuit arrangement shown in FIG. 4, the photosensitive cells function in a passive manner, that is they are non-conducting as long as they are not irradiated by a luminous source. Their conductivity rises linearly with the incident luminous radiation up to a maximum value. The maximum value of current flow should substantially correspond to the applied voltage which can then be collected at the terminals 25 and 26. If active, that is photoconductive or photovoltaic cells are used, terminals 20 and 21 are connected to ground terminal 27. In such a case, the voltage is produced in the cells themselves, and can also be collected at terminals 25 and 26 up to a maximum value depending on the type of end quantity of the cells used.  
 The control stick unit operates as follows:  
  In the vertical, that is, the neutral position of control stick 1, photosensitive cells 7 are not irradiated, as shown in FIG. 1, because of intervening screen 6. With the tilting of control stick 1 by an angle a, photosensitive cell 7a is irradiated by the light in a degree determined as a function of the angle, and it becomes correspondingly conductive for the current flowing from terminal 20 until it is in the limit position of the stick, as shown in FIG. 2. The full applied positive voltage can be collected between terminals 25 and 26.  
  While tilting control stick 1 by an angle a in the opposite direction, negative current flows from terminal 21 through photosensitive cell 7b and can be collected between terminals 25 and 26 as a negative voltage. The same is obtained with photosensitive cells 7c and 7d if control stick 1 is tilted perpendicularly to the drawing plane and a positive or negative voltage can be collected in the respective circuit, which is arranged in the same manner as shown in FIG. 4.  
  Control stick 1, mounted in a ball-socket swivelbearing, can be tilted in any direction, and the voltage produced corresponds to the angular position and directional orientation of the stick. In the example of FIG. 3, in the neutral position of control stick 1&#39;, the currents flowing through the two branches of the circuit and resulting from the irradiation of the photosensitive cells, compensate each other. At the tilting of stick 1&#39;, a difference voltage is obtained corresponding to the angular position and orientation and resulting from the voltages produced in the respective photosensitive cells 7a to 7d. In the same manner as described v in connection with FIGS. 1 and 2, this difference voltage can be collected at terminals 25 and 26. The embodiment of FIG. 3 has the advantage of better utilizing the radiation.  
  It is evident that instead of being a two-armed lever, as provided in the examples shown, the control stick I, 1 may also be designed as a one-armed lever, such as the control stick 3 shown in FIG. 5.  
  The control stick 3 is universally mounted on a universal mounting 2&#34; as shown in FIG. 5, and it includes a luminous source 5&#34;, which is located near its bottom end at a spaced location from pivot 2&#34;. Photoelectric cells 7a&#34;, 7b&#34;, 7c&#34; and 7d&#34;are arranged symmetrically around luminous source 5&#34;, as in the other embodiments.  
  While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.  
 What is claimed is:  
  l. A device for producing signals, comprising a control stick having a manipulatable handle portion and being universally pivotally movable to transmit control signals, universal mounting means mounting said control stick for universal pivotal movement, biasing means urging said control stick into a neutral position, transmission means comprising two electrical circuits adapted to be influenced by the angular position of said control stick, a source of luminous radiation mounted on and adjacent an end of said control stick at a spaced location from its pivotal mounting, means associated with said luminous radiation source to shield the photocells from the source in predetermined positions of said control stick, and at least four fixed photosensitive cells arranged in opposed pairs disposed symmetrically about said radiation source and two being connected in each of said two circuits, the center lines of said cells each being in a plane containing the axis of said control stick in said neutral position and being disposed at an angle to each other which is less than 180.  
  2. A device for producing signals, according to claim 1, wherein said shielding means comprises a screen surrounding said source of radiation and carried by said control stick and in which said photosensitive cells have bottom edges which extend in the same plane as the bottom edge of said screen.  
  3. A device for producing signals, according to claim 1, wherein said photosensitive cells are directly exposed to the said source of radiation.  
  4. A device for producing signals, according to claim 1, wherein said electrical circuits include a circuit having two photosensitive cells disposed at mutually opposed locations and being disposed in a plane which is perpendicular to the plane of the other two of said cells.  
  5. A device for producing signals, according to claim 1, wherein said photosensitive cells are passive cells.  
  6. A device for producing signals, according to claim 1, wherein said photosensitive cells are active cells.  
  7. A device for producing signals, according to claim 1, wherein said control stick is a double-armed lever, including an upper portion which is adapted to be engaged by a persons hand and a lower portion on the opposite side of said pivotal mounting carrying said source of luminous radiation.  
  8. A device for producing signals, according to claim 7, wherein said source of luminous radiation is carried on the outer end of the bottom of said control stick.  
  9. A device for producing signals, according to claim 1, wherein said control stick comprises a single arm lever, said luminous source of radiation being spaced from said pivotal connection upwardly along said con-