MX2008002006A - Dual rate force transducer - Google Patents

Abstract

A dual rate force transducer is disclosed. A spring is machined to have a first spring portion with a first spring rate, a second spring portion with a second spring rate, and a platen between the spring portions. A pair of flanges are affixed to the distal ends of the spring portions. At least one sensor is affixed to one of the flanges, and at least one other sensor is affixed to another one of the flanges. Mounting hardware is used to couple the springs, flanges and platen together, including at least one mechanical stop to limit displacement of the spring.

Description

DOUBLE SPEED FORCE TRANSDUCER FIELD OF THE INVENTION This application relates, in general, to measuring devices, and more particularly, to a force transducer that uses a one-piece machined spring that provides two different spring speeds and multiple sensors that measure the different speeds. BACKGROUND OF THE INVENTION In the prior art, two separate force transducers are used to measure two different force intervals. This requires separate mounting schemes for each transducer, which adds mechanical complexity and weight to the total hardware store schema. SUMMARY OF THE INVENTION A double speed force transducer includes a double speed spring coupled between opposite members. One portion of the spring has a first elastic velocity, and another portion of the spring has a second elastic velocity. A plurality of sensors is coupled to measure the displacement of the spring. A mechanical stop is used to limit compression of the spring. BRIEF DESCRIPTION OF THE FIGURES The modality (s) described could be understood more easily with reference to the figures that the REF. 190292 accompany, in which: Figures 1A and IB are plan views of a force sensor according to a preferred embodiment. Figure 2 is a perspective view of a force sensor with the spring omitted to show the LVDT. Figures 3A-3E are plan views of the spring and the flange. Figure 4 is a perspective view of a force sensor with a separate spring portion to show the LVDTs. Figures 5A-5C are electrical diagrams for the LVDT. Figures 6A-6B are graphs of the input force versus the output deviation. The same reference numbers indicate the same parts through all the different views of the Figures. DETAILED DESCRIPTION OF THE INVENTION The preferred embodiment described herein is a double speed force transducer. A double speed spring is provided through the machining of a single piece of material (such as stainless steel) so that it has two different tension specifications at either end of the spring, with a flange or plate shared between the two spring portions . Another flange is fixed at the far end of each spring portion. A plurality of LVDT is mounted with the spring to measure the displacement thereof. For example, in the preferred embodiment, the LVDT transformers are fixed on the shared central flange, while the movable cores (armatures) are fixed on either one of the end flanges. The signals that come from all the LVDTs are connected to a signal processing circuit, where they are processed and used for the detection and control schemes. As illustrated schematically in the Figures 1A and IB, a force transducer 10 includes a pair of opposite portions of post 20L, 20R and a spring 30 mounted between the post portions. Normally, the force sensor 10 is used for aircraft applications and is ideal for cabin control applications, which include the detection of the forces applied by the pilot in the aileron, elevator and rudder controls. The pole portions 20L, 20R have the flange portions 22L and 22R formed on the rear ends of the pole portions. In a preferred embodiment, a stop rod 32 is engaged between the flange portions 22L, 22R and is used to limit the compression / retraction and expansion / extension of the spring 30, so that the spring is protected from the limit force loads. total and final of the system. Specifically, spring 30 could be deform or fracture if (i) if it is allowed to move through an unlimited range of displacement during extension or retraction, or (ii) if you experience the total amount of force loads that are applied to the 20L, 20R post portions. Mounted for operation within the spring 30, there are three linear and variable differential transformers (LVDT) 40, 41 and 42, as shown in Figure 2. An LVDT is a displacement measurement device that is well known, which produces an electrical signal that is proportional to the displacement of the movable core (armature) within a cylindrical transformer. The full description thereof is considered unnecessary for the understanding of the present invention. The construction of the post portions 20L, 20R is also generally well known. Preferably, the struts or poles are of a cylindrical shape and are machined from stainless steel or aluminum so that they have a DI diameter of 1.90 centimeters (0.750 inches). (All the dimensions indicated in this description are approximate). The coupling portions 24 of the posts have a circular hole with a diameter D2 of 0.64 centimeters (0.250 inches) and are connected with one end of the sensor in a fixed position and at the other end of the sensor with the load of interest. The portions of flange 22L, 22R are also made of stainless steel or aluminum with a diameter D3 of approximately 5.71 centimeters (2.25 inches) and are fixed on the posts, for example, by welding. The total length Ll of the sensor in the null position is 24.13 centimeters (9.5 inches) with each of the post portions that have a length L2 that measures 7.62 centimeters (3.0 inches) and the portion of spring that has a length L3 that measures 8.89 centimeters (3.5 inches). The detailed illustration of the preferred embodiment of the spring 30 is shown in Figures 3A-3C. Preferably, the spring 30 is machined from a single piece of 15-5 PH stainless steel for the specification of aerospace material ("AMS") 5659, in a solution of a heat treated condition, so as to have a configuration cylindrical Starting on the right side of Figure 3A, the spring 30 includes an annular portion 33 with a depth XI of approximately 6.40 mm (0.252 inches) and a thickness X2 of approximately 0.0762 mm (0.003 inches), within which the flange is mounted 22L. In a preferred embodiment, the flange 22L is welded in place. The left side of the spring 30, as illustrated in Figure 3A, has a similar annular portion for mounting the flange 22R. The ends of the stop rods 32 pass through the corresponding flange holes 127 in the flanges 22L, 22R, respectively. As seen in Figures 1A and 3A, the spring 30 includes two different speed portions, namely, the Flight Data Recording (FDR) portion 30a and the Electronic Flight Control portion (FCE) 30c, separated by a spring division flange 30b. The FDR portion 30a and the FCE portion 30c of the spring 30 effectively create two springs that react to the forces applied by the control system during the clutch of FDR and FCE, respectively. In general, using well-known design criteria, the spring is constituted by beams that are displaced by 90 °. The thickness of the beams is such that it provides the spring with its elastic velocity by deformation under a total load. The thickness of the beam is varied in order to produce different spring speeds that are particular for any given application. The spacings or grooves 34, 35, 36 and 37 between the beams are imposed by the thickness of the beam and the total length of the spring. This type of force transducer would normally be used in a situation that requires two intervals of force. One much larger than the other, which normally required two separate force transducers to achieve the interval and accuracy requirements. Each spring can have its spring velocity (the thickness of the beams) adapted for a single range of force without affecting the range of the other spring. For a given force and a number of cycles, each spring must be able to withstand the stress without suffering a fatigue failure. With this in mind, stops are used to ensure that the spring observes a force that is beyond its operating range. While it is preferred that the spring and the diverting flanges be machined from a single piece of plowing material, it is possible to machine two individual springs and subsequently connect them, for example by welding or welding with brass with a common split flange . In addition, a single spring having double speeds could be machined without a central flange, and the flange could be added later, for example, through pins or welding. In this preferred embodiment, a series of three slotted portions 34 is formed between the beams in the spring portion FDR 30a of the spring 30, each having a depth X3 of 5.59 centimeters (2.2 inches) and an inside radius of curvature RI of 2.413 mm (0.095 inches). The width Wl of the slots 34 is 4,826 mm (0.190 inches). Two smaller grooved portions 35 are formed in the FCE portion 30c of the spring 30, each with the same depth X3 as the grooves 34, an inner radius R2 of 1. 397 mm (0.055 inches), and a width W2 of 1,778 mm (0.070 inches). The edges of the grooves 34, 35 have to be broken on the inside and outside around a radio mixture of 0.254 to 0.762 mm (0.010 to 0.030 inches) or 0.005 to 0.030 times 45 degrees plus or minus a 10 degree bevel. In addition, marks should not be machined on any of the inner spokes of the slots or on the outer surface of the spring. A series of three spaces 36 and two spaces 37 are also formed in the spring 30. The first set of separations or spaces 36 has the same width Wl as the slots 34, and the second set of spaces 37 has the same width W2 as the spaces. slots 35. The depth X4 of the separations or spaces 36, 37 is 4.95 centimeters (1,950 inches). It can be seen that the slots 34, 35 and the spaces 36, 37 are interleaved holes that allow a small degree of compression of the spring 30. As shown in Figure 3C, the spring split flange 30b of the spring 30 has a series of holes. Each of the three holes 26A-C has a diameter D4 of 0.79 centimeters (0.3125 inches), which are provided to receive the assembly for the transformation portion of the LVDT (not shown), as described below. One of the holes 26B is placed in the center of the flange, and the other two holes 26A, 26C are located in line with the center hole at a distance X5 of 1.83 centimeters (0.719 inches) 'from the center hole. Each of the two holes 27 has a diameter D5 of 0.64 centimeters (0.250 inches), which are placed at a distance X8 of 1.65 centimeters (0.650 inches) from the central hole 26. The holes 27 are provided for the dipstick. stop 32 so that it is inserted through them. Each of the three holes 28 has a diameter D6 of 0.35 centimeters (0.138 inches), which are provided to receive the conductors 18 of the LVDT located inside the spring 30. As shown in Figures 3D-3E, the flange 22L (and similarly the flange 22R that is not shown) has a series of holes. Each of the three holes 126A-C has a diameter D7 of 0.79 centimeters (0.3125 inches), which are provided to receive a mounting for the metal core of the LVDT (not shown), as described below. One of the holes 126B is placed in the center of the flange, and the other two holes 126A, 126C are located in line with the central hole 126b at a distance X6 of 1.83 centimeters (0.719 inches) from the center hole 126B. Each of the two holes 127 has a diameter D7 of 0.64 centimeters (0.250 inches), which are placed at a distance X7 of 1.65 centimeters (0.650 inches) from the central hole 126B. The holes 127 are provided so that the stop rod 32 is inserted through them. Next, with reference to Figure 1A and Figure 4, it can be seen that the stop rod 32 includes a pair of threaded rods 50 and clamping nuts positioned through the holes 27. Specifically, the stop rod 32 it includes a pair of threaded rods 50, which are placed through the corresponding holes 27 of the spring dividing flange 30b in the spring 30 and also through corresponding holes 127 in the flange 22L and in the flange 22R. Beside the flange 22L, the clamping nut 53 is fixed on the threaded rod 50 in a position that is displaced outwardly of the flange 22L in order to provide a mechanical stop for the extension of the FDR portion 30a of the spring 30. Similarly, the clamping nut 54 is fixed on the threaded rod 50 in a position that is displaced inwardly from the flange 22L so as to provide a mechanical stop for the portion FDR 30a of the spring 30. Similarly, together to the flange 22R, the clamping nuts 51 and 52 are fixed on the threaded rod 50 in order to provide mechanical stops against the extension and retraction, respectively, of the portion FCE 30c of the spring 30 of the flange 22R. The stop clutch point of the FCE portion 30c of the spring 30 is 0.508 mm (0.020) inches) from its unloaded position and the stop clutch point of the FDR portion 30a of the spring 30 is 2.28 mm (0.090 inches) from its unloaded portion. The specification of the stop rod is imposed by the limit and final loads. The material and / or size of the rod must be able to withstand the load that will be presented to the unit without deformation. The compression load will be the limiting factor and not the tensile load. Taking into account the length of the rod and its limited support at the guided end where it continues through the flanges 22L and 22R, the force applied through the nut has to be analyzed through a column method to ensure that The rods have a safety margin large enough to withstand the limit and final loads. The stop rod used can be of a standard threaded rod material, although the size has to be chosen according to the stress analysis. And similarly, the material of the threaded rod can be changed to an exotic material in order to get a stronger rod and provide a smaller package. Normally, the nut would be of a standard type out of the counter nut casing, although it could be in any form that could serve the intended function of supporting the flange load. It is also optional to have one, two or many stops as desired, however, two is probably the preferred configuration to allow a higher safety margin with a minimum adjustment of the individual rods needed. Next, with reference to Figures 2 and 4, the LVDT 41 has a fixed transformation portion 41T in position with the spring 30 with respect to the central hole 26b on the spring dividing flange 30b and the movable core 41A is fixed at the flange 22L with respect to the central hole 126b. Similarly, the LVDT 40 has its fixed transformation portion 40T in position within the spring 30 with respect to the hole 126A in the spring dividing flange 30b and the movable core 40A is fixed in the other flange 22R with respect to the opening of the valve. end 126A. The LVDT 42 is configured in the same way as the LVDT 40, so that its transformation portion 42T is fixed with respect to the hole 26 in the spring dividing flange 30b in the spring 30 and its movable core 42A has been fixed with with respect to the hole 126A of the flange 22R. In this way, the two outer LVDTs 40, 42 have their fixed movable core on the flange 22R while the central LVDT 41 has its fixed movable core on the flange 22L. The electrical schemes for each of the LVDTs are provided in Figures 5A-5C. The output characteristic for the FCE portion 30c of the spring 30 is illustrated in Figure 6A, where the channels 1 and 2 (the LVDTs 40 and 42) are summed in phase. The output characteristic for the FDR portion 30a of the spring 30 is illustrated in Figure 6B, where the channel 3 (the LVDT 41) is measured. It is noted that the above description is a preferred embodiment, although the dimensions and measurements are approximate. In general, a sensor constructed in accordance with this description can be used to measure a total scale interval of ± 284.40 kilograms (± 627 pounds), with a load limit of ± 657.71 kilograms (± 1450 pounds) and a final limit of ± 986.56 kilograms (± 2175 pounds). The spring ratio for the FCE extension is 1000 pounds / inch ± 10%, and the spring ratio for the retraction FDR is 7000 pounds / inch ± 10%. The electrical specifications are given in Table I.

Performance specifications are given in the Table II.

Although a specific embodiment has been described, it will be evident that various modifications and changes could be made to this embodiment without departing from the spirit and scope of the invention. Consequently, the specification and the figures will be considered illustrative rather than restrictive. The suitable scope of the invention is defined by the accompanying claims. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A double speed force sensor, characterized in that it comprises a pair of opposed members that have a double speed spring coupled between them and a plurality of sensors is placed in close proximity to the spring and is adapted to measure the displacement of the spring. The double speed force sensor according to claim 1, characterized in that the double speed spring is precision machined from a single piece of material to be machined, so as to have a first spring portion with a first elastic speed, a second spring portion with a second spring speed, and a fixed stage between the proximal ends of the first and second spring portions. 3. The double speed force sensor according to claim 1, characterized in that each sensor has a fixed transformer and a movable core, at least one of the sensors having its movable core connected to an opposite member and at least one of the sensors that has its movable core connected to the other opposite member. 4. The double speed force sensor according to claim 1, characterized in that the sensors are connected to a signal processing circuit. The double speed force sensor according to claim 1, further characterized in that it comprises a mechanical stop which provides a physical limit for the displacement of the spring. 6. A double speed force transducer, characterized in that it comprises: a pair of posts, each having a flange at the proximal end thereof; a spring mounted on the flanges between the posts and having a first portion with a first elastic speed, a second portion with a second elastic speed and a fixed stage between the proximal ends of the first and second portions, wherein the first end of the the spring is coupled with a flange and the second end of the spring is coupled with the other flange; and a plurality of displacement sensors coupled proximal to the spring, each sensor having a fixed transformer and a movable core, at least one of the sensors having its movable core coupled with a flange and at least one of the sensors that has its core movable coupled with the other flange. The double speed force transducer according to claim 6, characterized in that the spring is precision machined from a single piece of material to be machined. The double speed force transducer according to claim 6, further characterized in that it comprises a mechanical stop which provides a physical limit for the displacement of the spring. 9. A double speed force sensor, characterized in that it comprises: a first spring having a first spring speed; a second spring having a second elastic velocity; first and second flanges, each one is located at the distal end of the first and second springs, respectively; a third flange that engages the proximal end of the first spring with the proximal end of the second spring; the mounting hardware item is coupled through the first, second and third flanges; and a plurality of force sensors mounted proximate the first and second springs and adapted to measure the displacement of the spring. The double speed force sensor according to claim 9, characterized in that the first spring, the second spring and the third flange are machined with precision from a single piece of material to be machined. The double speed force sensor according to claim 9, characterized in that each displacement sensor has a fixed transformer and a movable core., at least one of the sensors having its movable core coupled with the first flange and at least one of the sensors having its movable core coupled with the second flange. 12. The double speed force sensor according to claim 9, characterized in that the mounting hardware article includes a mechanical stop that provides a physical limit for spring displacement. 13. A double speed force transducer, characterized in that it comprises: a double speed spring machined from a single piece of material to be plowed, so that it has a first spring portion with a first elastic speed, a second portion of spring with a second elastic speed and a fixed stage between the ends next to the first and second spring portions; a first flange and a second flange, each coupled with the distal end of the first spring portion and the second spring portion, respectively; an assembly hardware item coupled through the flanges and the platen including a mechanical stop that provides the physical limit for the displacement of the spring; and a plurality of displacement sensors mounted within the spring, at least one of the sensors is coupled with the first flange and at least the other of the sensors is coupled with the second flange. A method of manufacturing a double speed force transducer, characterized in that it comprises: forming a double speed spring having a first portion with a first elastic velocity and a second portion with a second elastic velocity; and mounting a plurality of displacement sensors in close proximity to the spring. The method according to claim 14, characterized in that the forming step includes precision machining of the spring from a single piece of material to be machined. 16. The method of compliance with the claim 15, further characterized by comprising the formation of a platen from the single piece of material to be machined between the proximal ends of the first and second spring portions. 17. The method of compliance with the claim 16, further characterized in that it comprises the formation of a pair of flanges, each is coupled at the distal end of the first spring portion and the second spring portion, respectively. 18. The method of compliance with the claim 17, characterized in that at least one of the displacement sensors is coupled with one of the flanges and at least one of the displacement sensors is coupled with another of the flanges. 19. The method according to the claim 14, further characterized in that it comprises providing a mechanical stop to the spring in order to limit the displacement thereof. 20. A spring displacement measuring method, characterized in that it comprises: providing a double speed spring coupled between the opposing members; and providing a plurality of sensors coupled in close proximity to the spring and adapted to measure the displacement of the spring. 21. The method in accordance with the claim 20, characterized in that at least one sensor is connected to measure a first elastic velocity and at least one other sensor is connected to measure a second elastic velocity. 22. The method of compliance with the claim 21, characterized in that the sensors are connected to a signal processing circuit.