LOAD CELL FOR AIRCRAFT CONTROL STICK

• US 3,729,990 A
• Filed: 05/10/1971
• Issued: 05/01/1973
• Est. Priority Date: 05/10/1971
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Kenneth L. Oliver
• Inventors: Oliver, Kenneth L.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/141,570
• Time in Patent Office: 722 Days
• Field of Search: 73/88.5R,133,141A,147,189,117.4 244/83R,83E
• US Class Current: 73/862.05
• CPC Class Codes: G01L 5/1627 of strain gauges using piezoresistors G01L5/162
• CPC Class Codes: G01L 5/223 to joystick controls

Abstract

An aircraft control stick contains a load cell for measuring shear forces applied to the stick. The cell includes a flat base plate for mounting the cell in the control stick, an upper plate for receiving the forces applied to the control stick, and an intermediate plate for mounting the force-responsive elements of the cell. The intermediate plate is supported above and parallel to the base plate by a plurality of flat spring flexure members disposed in planes normal to the plane of the two plates and parallel to one another so as to permit relative motion between the two plates only in the direction at right angles to the planes of the spring flexure members. A plurality of flat cantilevered load beams are also mounted on the base plate in planes parallel to the spring flexure members. Yoke members mounted on the intermediate plate straddle the free ends of the load beams so as to contact and deflect the load beams when deflections of the spring flexure members exceed a preset threshold value. Electrical strain gauges in each cantilevered load beam provide electrical output signals representative of the deflection of the load beams. The upper flat plate is disposed in the plane parallel to and above the intermediate plate. The upper plate is mechanically coupled to the intermediate plate by a second array of spring flexure members and cantilevered load beams.

Claims

1. An improved electrical transducer for a control stick having a handgrip portion and a control stick portion, said transducer being of the type having a first resilient means capable of deflecting only in response to shear forces applied to said handgrip in a first direction, second resilient means capable of deflecting only in response to shear forces applied in a direction at right angles to said first direction, and first and second electrical sensing means individually responsive to deflections of said first and second resilient means respectively, said improvement comprising a top plate secured to said handgrip portion, a bottom plate secured to said control stick portion and an intermediate plate disposed between said top and bottom plates, said top and intermediate plates being mechanically coupled through said first resilient means, said intermediate and bottom plates being mechanically coupled through said second resilient means, each of said electrical sensing means being in the form of cantilevered beams arranged to flex only in the direction that the corresponding resilient means is capable of flexing, said cantilevered beams being actuated by yoke members adjusted to deflect said cantilevered beams only after the corresponDing resilient means has been deflected through a predetermined dead zone, the cantilevered beams of said first and second electrical sensing means being individually removably mounted on said intermediate and lower plates respectively.

2. A load cell for a vehicle control stick comprising a first array of elongated resilient elements disposed transversely between two parallel flat plates, each of said resilient elements being constructed to flex readily in a first lateral direction but being substantially rigid in a lateral direction at right angles to said first direction, said elements being aligned so that said first directions all lie in parallel planes, said array of resilient elements including spring flexure members and cantilevered load beams, each flexure member having its ends rigidly secured to said parallel plates, each of said cantilevered beams having a base end rigidly secured to one of said flat plates and a free end terminating near the second of said flat plates, a yoke member corresponding to each load beam, said yoke member being supported on said second flat plate and arranged to straddle the free end of the associated load beam, said yoke member being adjusted to contact the associated load beam only after the flexure members have been deflected a predetermined amount so as to establish a specified dead zone, and an electrical strain gauge in each load beam for providing an electrical signal indicative of the magnitude of any deflection in the load beam, said load cell further including a second array of resilient elements disposed transversely between one of said flat plates and a third parallel flat plate, said second array being constructed identically with said first array but being oriented to flex only in response to lateral forces at right angles to said first direction.

3. The load cell of claim 2 in which the vehicle is an aircraft and the forces to be measured are the roll and pitch forces applied to the control stick handgrip by the pilot, said first array being oriented so that said first lateral direction is parallel to the transverse axis of the aircraft to be controlled.

4. The load cell of claim 3 in which each of the resilient elements is an elongated member having a rectangular cross section proportioned to have a relatively broad dimension and a thin dimension, the resilient elements of said first array being aligned so that their broad dimensions are parallel to the longitudinal axis of the aircraft to be controlled.

5. The load cell of claim 4 wherein said third flat plate is adapted for mounting in said control stick and said second flat plate is adapted for mounting on said handgrip.

6. The load cell of claim 5 wherein the cantilevered load beams are more compliant than the spring flexure members whereby deflection forces are absorbed principally by said spring flexure members.

7. The load cell of claim 5 further including adjustable stop members for limiting the maximum motion of said third flat plate with respect to said second flat plate.

8. The load cell of claim 7 wherein said yoke members include adjustment means for altering the dead zone of individual load beams.

9. A load cell for detecting roll and pitch shear forces applied to the handgrip of an aircraft control stick comprising a flat base plate for securing the load cell to said control stick, an intermediate flat plate lying in a plane parallel to and above the plane of said base plate, said intermediate plate being mechanically coupled to said base plate by means of a first array of resilient elements, said first array including a plurality of spring flexure members each adapted to flex in response to a shear force applied to said hand grip in a first direction and being rigid in response to shear forces exerted on said handgrip in a direction orthogonal to said first direction, said first array further including a plurality of cantilevered load beams each secured to one of said plates and having a free end positioned near the other of said Plates, means on said other plate for contacting and deflecting said beam when the relative motions of said plates resulting from flexures of said spring flexure members exceeds a predetermined amount, each of said cantilevered beams including an electrical strain gauge for producing an electrical signal indicative of deflections induced in the load beam, said load cell further including a flat upper plate for securing the cell to said handgrip, said upper plate being disposed in a plane parallel to and above said intermediate plate, said upper plate being further mechanically coupled to said intermediate plate through a second array of resilient elements, said second array being constructed so as to be identical with said first array but being oriented orthogonally with respect to said first array so as to flex in response to shear forces applied orthogonally with respect to said first direction and to be rigid with respect to forces applied in said first direction.