C-shaped cylindrical core for a linear variable differential transformer (LVDT) probe

Abstract

Apparatuses and related methods relate to a C-shaped cylindrical core for a linear variable differential transformer (LVDT) probe, and more particularly to a linear variable differential transformer (LVDT) probe that includes a plunger rod and a metal sheet formed as a cylinder having a C-shaped cross-section, the metal sheet being configured to be coupled to the plunger rod. In an exemplary example, the coupling can be an interference fit assisted by a spring retaining force of the metal sheet. The metal sheet can be stamped, formed, and applied to the plunger rod without annealing. One or more longitudinal metal sheet edges can be rounded. The C-shaped metal sheet can be welded to the plunger rod at the distal and / or proximal ends. In some examples, the longitudinal edges of the metal sheet can be welded together and / or welded to the plunger rod. The ratio of the relative magnetic permeability of the metal sheet to the plunger rod can be greater than 10. Various embodiments can advantageously reduce variability between batches and reduce the cost of manufacturing LVDTs.

Description

[0001] This application is a divisional application of a Chinese patent application filed on April 14, 2020, with the title "C-Shaped Cylindrical Core for Linear Variable Differential Transformer (LVDT) Probe" and the application number 201880066864.X. Technical Field

[0002] Various embodiments generally relate to displacement sensors. Background Art

[0003] Electronic sensors can detect various environmental parameters and generate response signals. For example, a pressure sensor can detect the pressure in an industrial pipeline. A temperature sensor can detect the ambient temperature or can detect, for example, the temperature in a chamber. An accelerometer can detect vibrations or shocks and can, for example, deploy an automotive airbag. A displacement sensor can detect linear or angular displacement. For example, a motion sensor can turn on a light in response to detecting a person's motion.

[0004] Displacement sensors can be implemented in various applications. In a pressure measurement application, a pressurized vessel (e.g., an oil pipeline) can include a diaphragm that moves outward in response to pressure and moves inward in response to a vacuum. A displacement sensor can be coupled to the diaphragm to measure the pressure in the pipeline by measuring the displacement of the diaphragm. Summary of the Invention

[0005] The device and related method relate to a linear variable differential transformer (LVDT) probe that includes a plunger rod and a metal sheet formed as a cylinder having a C-shaped cross-section, the metal sheet being configured to be coupled to the plunger rod. In an exemplary example, the coupling can be an interference fit assisted by the spring holding force of the metal sheet. The metal sheet can be stamped, formed, and applied to the plunger rod without annealing. One or more longitudinal metal sheet edges can be rounded. The C-shaped metal sheet can be welded to the plunger rod at the distal end and / or proximal end. In some examples, the longitudinal edges of the metal sheet can be welded together and / or welded to the plunger rod. The ratio of the relative magnetic permeability of the metal sheet to the plunger rod can be greater than 10. Various embodiments can advantageously reduce variability between batches and reduce the cost of manufacturing LVDTs.

[0006] Various embodiments can achieve one or more advantages. For example, some embodiments can improve durability, thereby reducing the risk of damage during manufacturing and during in-field use. Some embodiments can increase reliability, especially in high-vibration environments. In the case of a dual-channel LVDT example, a higher inter-channel correlation (e.g., better tracking) can be achieved. Some embodiments may exhibit lower output sensitivity and / or linear variation due to temperature limits (e.g., lower temperature coefficient). In various examples, the overall outer diameter can be reduced, which can reduce the device weight and can reduce the overall size and weight of the final application. Some embodiments can achieve a low-cost manufacturing process, such as metal stamping, forming, and press fitting. These manufacturing processes can be automated, thereby further reducing costs.

[0007] Details of various embodiments are set forth in the accompanying drawings and the following description. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1A An exemplary C-shaped probe core within a linear variable differential transformer (LVDT) for measuring the deployment state of a landing gear assembly on an aircraft is depicted.

[0009] Figure 1B An exemplary LVDT is depicted.

[0010] Figure 2 An exploded perspective view of an exemplary LVDT probe is depicted.

[0011] Figure 3 A perspective view of the distal end of an exemplary LVDT probe is depicted.

[0012] Figure 4 A perspective view of the distal end of an exemplary LVDT probe is depicted, showing a chamfer on the probe core.

[0013] Figure 5 A perspective view of the distal end of an exemplary LVDT probe is depicted, showing a single weld seam.

[0014] Figure 6 A perspective view of exemplary distal and proximal spot welds between an LVDT core and a rod is depicted.

[0015] Figure 7 A perspective view of exemplary distal and proximal circumferential welds between an LVDT core and a shaft is depicted.

[0016] Figure 8 A perspective view of an exemplary longitudinal weld between an LVDT core and a rod is depicted.

[0017] Figure 9Depicts a perspective view of an exemplary core fixture applied to an LVDT core.

[0018] Figure 10 Depicts a perspective view of an exemplary LVDT probe having a knurled rod for holding the core.

[0019] Figure 11 Depicts a perspective view of an exemplary LVDT probe showing the application of an adhesive for holding the core.

[0020] Figure 12 Depicts a perspective view of an exemplary LVDT probe showing the use of an end stop and the press - fit application of the core from the proximal end.

[0021] Like reference symbols in the various figures represent like elements. Detailed Description

[0022] For ease of understanding, this document is organized as follows. First, a use - case scenario is briefly introduced that shows an exemplary C - shaped core held on the plunger rod of a linear variable differential transformer (LVDT). Figure 1A The construction of an exemplary LVDT is further explained. Next, reference is made to Figure 1B to discuss turning to an exemplary embodiment showing the C - shaped core and its relationship to the plunger rod within the LVDT. Next, in Figure 2 and Figure 3 and Figure 4 various exemplary rounding features of the corners and edges of the core material are described in detail. Next, Figures 5 to 12 shows various exemplary holding methods. Specifically, Figure 5 、 Figure 6 and Figure 7 depict exemplary end welds, Figure 8 depicts exemplary longitudinal welds, Figure 9 depicts an exemplary holding fixture, Figure 10 depicts exemplary static friction enhancement features, Figure 11 depicts an exemplary adhesive, and Figure 12 depicts exemplary end stop features.

[0023] Figure 1ADepicts an exemplary C-shaped probe core within a linear variable differential transformer (LVDT) that measures the deployment state of a landing gear assembly on an aircraft. The LVDT use case scenario 100 includes an LVDT 105. The LVDT includes a plunger probe 110. A C-shaped core 115 is coupled to the plunger probe 110. In some examples, the C-shaped core 115 can be coupled to the plunger probe 110 by an interference fit. The C-shaped core 115 can have a magnetic permeability greater than one. In some examples, the C-shaped core 115 can have a magnetic permeability that is at least 10 times greater than the magnetic permeability of the plunger probe 110.

[0024] In some examples, the C-shaped core 115 can be manufactured from a substantially thin metal sheet. The substantially thin metal sheet can advantageously minimize the outer diameter of the C-shaped core 115 assembled onto the plunger probe 110. The plunger probe 110 coupled to the C-shaped core 115 is slidably engaged with a core housing 120. The core housing 120 includes an excitation sensing wire harness 125. The minimized outer diameter of the C-shaped core 115 can be a starting point for optimizing the overall diameter of the core housing 120. Thus, the substantially thin metal sheet included in the C-shaped core 115 can advantageously enable the design of an LVDT 105 with a small outer diameter.

[0025] The LVDT 105 is coupled to the landing gear assembly 130. The LVDT 105 can sense the deployment state of the landing gear assembly 130. The LVDT 105 can be coupled to a flight control panel within the aircraft to indicate the deployment state of the landing gear 130.

[0026] Figure 1B Depicts an exemplary LVDT. The LVDT 105 includes a plunger probe 110. The plunger probe 110 is coupled to a C-shaped core 115. The plunger probe 110 extends outside of the core housing 120. The C-shaped core 115 is surrounded by an excitation winding 135 (primary) and a pair of sensing windings 140A, 140B (secondary). The windings 135, 140A, and 140B are coupled to the excitation sensing wire harness 125. The windings 135, 140A, and 140B reside within the core housing 120. The excitation sensing wire harness 125 extends from outside of the core housing 120 to the windings 135, 140A, and 140B inside the core housing 120.

[0027] The excitation winding 135 can generate a magnetic field in response to an excitation signal. The sensing windings 140A and 140B can be magnetically coupled to the magnetic field and can generate an electrical output signal in response to the magnetic field coupling. The magnetic field coupling can vary based on the position of the C-shaped core 115 within the core housing 120. Thus, the electrical output signals from the sensing windings 140A and 140B can vary in response to the longitudinal position of the C-shaped core 115 relative to the windings 135, 140A, and 140B.

[0028] In an exemplary example, an excitation signal is applied to the excitation winding 135 via the excitation sensing harness 125. When the plunger probe 110 slides within the core housing 120, the resulting electrical output signal is sent out from the excitation sensing harness 125. In some examples, the processing module may be electrically coupled to the excitation sensing harness 125. The electrical output signal generated by the LVDT may be detected by the processing module. Thus, the processing module can determine the linear position of the plunger probe 110. In the LVDT use case scenario 100, an aircraft pilot can determine the deployment status of the landing gear assembly 130 based on the resulting output from the processing module.

[0029] Figure 2 A disassembled perspective view of an exemplary LVDT probe is depicted. The LVDT probe rod 205 is coupled to the core 210. The core 210 can be stamped from a metal sheet. In some examples, the core 210 can be die cut from a metal sheet. Additionally, the core 210 can be laser cut from a metal sheet.

[0030] The core 210 is further formed into a cylindrical shape. By way of example and not limitation, the forming process can include die forming, stamping, or pressing. In some examples, the forming process can include rolling. In other examples, the forming process can include electrical discharge machining (EDM).

[0031] The inner diameter of the cylindrical-shaped core 210 can be smaller than the outer diameter of the probe rod 205. The cross-section of the core 210 can be C-shaped. For example, a mandrel press can be used to press-fit the core 210 onto the probe rod 205. In some examples, the core 210 can be press-fitted using an automated method. The spring force inherent in the metal sheet can provide the gripping force for holding the core 210 to the probe rod 205. The use of the core 210 made of a metal sheet can reduce the final outer diameter of the LVDT assembly (e.g., Figure 1A , item 105). The spring force can hold the core 210 on a cylindrical rod (e.g., the probe rod 205).

[0032] In some examples, the core 210 can be assembled onto the probe rod 205 without a press fit. For example, the core 210 can be wound around the probe rod 205. After the winding operation, the core 210 can be squeezed to fix it to the probe rod 205. The core 210 can be tightened to firmly bond the core 210 to the probe rod 205.

[0033] In some examples, the core 210 can be slid onto the probe rod 205 without a press fit. The sliding core 210 can be welded to the probe rod 205. In some examples, the core 210 can be press-connected to the probe rod 205.

[0034] The winding operation can hold the core 210 on a cylindrical rod (e.g., the probe rod 205). The squeezing operation can hold the core 210 on a cylindrical rod (e.g., the probe rod 205). The tightening can hold the core 210 on a cylindrical rod (e.g., the probe rod 205). The welding can hold the core 210 on a cylindrical rod (e.g., the probe rod 205). The crimping can hold the core 210 on a cylindrical rod (e.g., the probe rod 205).

[0035] In an exemplary example, an LVDT assembly including a core 210 coupled to a probe rod 205 (e.g., Figure 1A , item 105) can be placed in position in an aircraft engine to measure oil pressure. The LVDT assembly within the aircraft engine may be subject to substantially high vibrations. In such cases, the term "substantially" can be up to 400 g (due to the acceleration of gravity). The core 210 can be held on the probe rod 205 by the spring force within the metal of the core 210 combined with the static friction between the probe rod 205 and the core 210.

[0036] Some embodiments can improve the durability of the core 210, which can advantageously reduce the risk of damaging the core 210 during manufacturing and during in-field use. In an exemplary example, due to the absence of an annealing process, the properties of the core (e.g., 210) can resist the effects of scratching along the core surface. The absence of an annealing process can mitigate the magnification of the grains contained within the core. The mitigation of grain magnification can produce a more consistent permeability within the core. Additionally, by maintaining finer grains, the grain distribution is averaged, which can advantageously reduce the variation between batches, thereby making the core consistent between parts and batches.

[0037] Figure 3 A perspective view of the distal end of an exemplary LVDT probe is depicted. The LVDT probe assembly 300 includes a shaft 305 and a block 310. In some examples, the block 310 can be a core (e.g., Figure 2 , item 210). The block 310 includes a longitudinally slotted opening 315. The block 310 includes longitudinal edges 320 on each side of the longitudinally slotted opening 315. The longitudinal edges 320 can be rounded. In various embodiments, the rounding of the edges 320 can be accomplished by a manufacturing process that removes material at the corners of the edges 320, thereby producing edges 320 with a certain radius. If welding is implemented, the radius on the longitudinal edges 320 can advantageously allow welding to both edges 320 through a single weld. Additionally, if welding is implemented, the radius can provide a groove to reduce the profile of the weld. Further, rounding the edges 320 can advantageously reduce the weld stress.

[0038] Figure 4A perspective view of the distal end of an exemplary LVDT probe is depicted, which shows a chamfer on the probe core. The LVDT probe assembly 400 includes a shaft 405 and a block 410. The block 410 includes a longitudinally slotted opening 415. The block 410 includes corners 420 at the distal ends on each side of the longitudinally slotted opening 415. The corners 420 are rounded (including a certain radius). If the corners are implemented, the radius on the corners 420 can advantageously provide space for end welds.

[0039] Figure 5 A perspective view of the distal end of an exemplary LVDT probe is depicted, which shows a single weld. The LVDT probe assembly 500 includes a shaft 505 and a C-shaped core 510. The C-shaped core 510 includes a longitudinal gap 515. The C-shaped core 510 includes a radial weld 520 at the distal end of the longitudinal gap 515. The radial weld 520 can advantageously fix the core 510 to the shaft 505. In some examples, the LVDT probe assembly 500 can be a plunger assembly. In some examples, the radial weld 520 can be an end weld. Various radial welds 520 can hold the C-shaped core 510 on a cylindrical rod (e.g., the shaft 505).

[0040] Figure 6 A perspective view of exemplary distal and proximal spot welds between an LVDT core and a rod is depicted. The LVDT probe assembly 600 includes a rod 605 and a C-shaped core 610. The C-shaped core 610 includes a longitudinal gap 615. The C-shaped core 610 includes a weld 620 at the distal end of the longitudinal gap 615. The C-shaped core 610 includes a weld 625 at the proximal end of the longitudinal gap 615. The welds 620 and 625 can be keyhole welds. In some examples, the welds 620 and 625 can be various other welds (e.g., spot welds, machine welds, laser welds, tungsten inert gas (TIG) welds, gas tungsten arc weld (GTAW) welds). In some examples, the welds 620 and 625 can be laser welds. In some examples, the welds can bond the rod 605 to the C-shaped core 610.

[0041] Figure 7 A perspective view of exemplary distal and proximal circumferential welds between an LVDT core and a shaft is depicted. The LVDT probe assembly 700 includes a shaft 705 and a core sleeve 710. The core sleeve 710 includes a longitudinal gap 715. A peripheral weld 720 is implemented at the distal end of the core sleeve 710. A peripheral weld 725 is also implemented at the proximal end of the core sleeve 710. The peripheral welds can advantageously prevent the core sleeve 710 from slipping off the shaft 705. Various peripheral welds 720 can hold the core sleeve 710 on a cylindrical rod (e.g., the shaft 705).

[0042] In various embodiments, the distal circumferential weld 720 can be present without the proximal circumferential weld 725. Embodiments with the distal circumferential weld 720 without the proximal circumferential weld 725 can reduce the profile of the LVDT probe assembly 700.

[0043] Additionally, the proximal circumferential weld 725 can be present without the distal circumferential weld 720. Embodiments with the proximal circumferential weld 725 without the distal circumferential weld 720 can provide additional spacing from the distal end of the LVDT probe assembly 700 to the core housing (e.g., Figure 1A , item 120). Placing the welds 720 and 725 on one end can save costs and reduce the risk of foreign object debris (FOD), while still firmly holding the core sleeve 710 on the shaft 705. In some embodiments, no additional welds can be applied, which can advantageously further reduce costs and further reduce the risk of FOD. Due to spring retention along the length of the core sleeve 710, the core sleeve 710 can be firmly held to the shaft 705.

[0044] Figure 8 A perspective view depicting an exemplary longitudinal weld between the LVDT core and the rod is shown. The LVDT probe assembly 800 includes a shaft 805 and a core sleeve 810. The core sleeve 810 includes a longitudinal gap (e.g., Figure 3 , item 315). A longitudinal weld 815 is achieved along the longitudinal gap of the core sleeve 810. As shown in detail B-B, the longitudinal weld 815 can penetrate the core sleeve 810 and into the shaft 805. The longitudinal weld 815 can firmly hold the core sleeve 810 to the shaft 805. Various longitudinal welds 815 can hold the core sleeve 810 on a cylindrical rod (e.g., shaft 805).

[0045] Figure 9 A perspective view depicting an exemplary core clamp applied to the LVDT core is shown. The LVDT probe assembly 900 includes a shaft 905 and a core sleeve 910. The core sleeve 910 includes a longitudinal gap 915. At the distal end of the LVDT probe assembly 900, a groove 920 is defined around the core sleeve 910. The groove 920 holds the clamp 925. The core sleeve 910 can be advantageously fixed to the shaft 905 at least in part by the spring force of the clamp 925. Various clamps (e.g., 925) can hold the core sleeve 910 on a cylindrical rod (e.g., shaft 905).

[0046] Figure 10A perspective view of an exemplary LVDT probe having a knurled rod for retaining a core is depicted. The LVDT probe assembly 1000 includes a rod 1005 and a core sleeve 1010. The core sleeve 1010 includes a longitudinal gap 1015. The rod 1005 includes a knurled pattern 1020. The knurled pattern 1020 can advantageously increase the static friction between the rod 1005 and the core sleeve 1010. The increased friction can securely hold the core sleeve 1010 in place in a high-vibration environment. Various knurled patterns (e.g., 1020) can hold the core sleeve 1010 on the rod 1005. Additionally, various friction-enhancing methods (e.g., grinding, sandblasting, soda blasting, laser etching, chemical etching) can hold the core sleeve 1010 on the cylindrical rod 1005.

[0047] Figure 11 A perspective view of an exemplary LVDT probe is depicted, which shows the application of an adhesive for retaining a core. The LVDT probe assembly 1100 includes a rod 1105 and a core sleeve 1110. The core sleeve 1110 includes a longitudinal gap 1115. The rod 1105 includes an adhesive 1120. The adhesive 1120 can advantageously increase the bond between the rod 1005 and the core sleeve 1010. The increased bond can securely hold the core sleeve 1010 in place in a high-vibration environment. The adhesive (e.g., 1120) can hold the core sleeve 1110 on the rod 1105.

[0048] Figure 12 A perspective view of an exemplary LVDT probe is depicted, which shows the use of an end stop and a press-fit application of a core from the proximal end. The LVDT probe assembly 1200 includes a plunger rod 1205 and a sleeve core 1210. The sleeve core 1210 includes a longitudinal gap 1215. The plunger rod 1205 is fixedly coupled to an end stop 1220. When the sleeve core 1210 is press-fitted onto the plunger rod 1205 in the assembled state, the diameter of the end stop 1220 can be less than or equal to the outer diameter of the sleeve core 1210.

[0049] During the assembly of the LVDT probe assembly 1200, the sleeve core 1210 is press-fitted onto the plunger rod 1205 until it seats against the end stop 1220. The end stop can be configured to prevent movement of the sleeve core 1210 away from the end of the plunger rod 1205. In some examples, the plunger rod 1205 can be tapered such that the narrower end is the distal end having the end stop 1220. Movement of the sleeve core 1210 toward the proximal end can be mitigated by the larger outer diameter on the plunger rod 1205. Additionally, the end stop 1220 can mitigate movement of the sleeve core 1210 toward or away from the distal end.

[0050] Once the sleeve core 1210 is press-fitted onto the plunger rod 1205, the probe coupler 1225 can be coupled to the plunger rod 1205. The plunger rod 1205 includes a threaded end 1230. In some examples, the plunger rod 1205 and the threaded end 1230 are structurally integral. Various end stop features (e.g., 1220) can hold the sleeve core 1205 on the plunger rod 1205.

[0051] Although various embodiments have been described with reference to the drawings, other embodiments are possible. For example, early in the manufacturing process, the LVDT core in a flat sheet state can be stamped using a press. The press can stamp the core one or more times. The multiple stamping process can cause the grains within the LVDT core in the flat sheet state to break and become finer. The finer grains can average the grain domains within the LVDT core in the flat sheet state. This averaging can advantageously reduce the inter-batch variation in the magnetic properties of the LVDT core in the flat sheet state. The low inter-batch variation can advantageously allow field service personnel to replace a failed LVDT with a new one, for example, without calibration and without sorting electrical characteristics.

[0052] Various embodiments can reduce zero offset. The LVDT C-core can be press-fit onto the plunger rod. The press-fit can cause the inherent spring force within the core material to hold the core on the plunger rod without welding. When the welding operation is omitted, ion carbide lines can be avoided. In the absence of ion carbide lines, the stress involved in high-temperature applications can also be reduced, which can advantageously reduce zero offset (e.g., the offset of the core). In an exemplary example, a dual-channel LVDT is installed in a turbogenerator. The design may rely on the tracking between the two channels to detect small differences in linear displacement. When the temperature within the generator increases, the non-welded design of the dual-channel LVDT allows the C-core to remain in place on the plunger rod. The reduced zero offset effect provides monitoring electronics for detecting true differential movement between the LVDT channels.

[0053] In various embodiments, the starting core material can be a metal sheet. By way of example and not limitation, the metal sheet can be about 0.005", 0.006", 0.007", 0.008", 0.009", 0.010", 0.011", 0.012", 0.013", 0.014", 0.015", 0.016", 0.017", 0.018", 0.019", 0.020", 0.021", 0.022", 0.023", 0.024", 0.025", 0.030", 0.03125", 0.035", 0.040", 0.045", 0.050", 0.055", 0.060", 0.0625", 0.065", 0.070", 0.075", 0.080", 0.085", 0.090", 0.095", 0.100", 0.125", 0.150", 0.175", 0.200", or up to at least about 0.250" or more. The metal sheet can be substantially thin. The term "substantially thin" can be defined as falling within the stated thickness of the metal sheet.

[0054] In some examples, the starting core material can be a metal sheet. The metal sheet can be any ferromagnetic or martensitic material. In some examples, the core material can be a high permeability material. By way of example and not limitation, the material can include iron and nickel. For example, the material can also include cobalt, gadolinium, dysprosium, permalloy, pyrrhotite, stilbite, magnetite, copper, chromium, molybdenum, and / or silicon. Thus, various alloys can be employed in various cores.

[0055] In various examples, the starting core material can be a metal sheet. The metal sheet can be formed by various methods. By way of example and not limitation, the forming process can include die forming, stamping, pressing, rolling, or electrical discharge machining (EDM).

[0056] In some examples, a deep drawing forming process can be used on the metal sheet. In such examples, a high permeability metal sheet can be placed into a deep drawing press. The resulting deep drawn portion can be press fit onto a plunger rod and welded at the end. In some examples, the deep drawn portion can provide an interference fit with the plunger rod and can be press fit without welding.

[0057] In various embodiments, the LVDT rod can include longitudinal ribs. The longitudinal ribs can mate with longitudinal gaps on the LVDT core. The longitudinal ribs and gaps can advantageously lock the components to ensure a consistent assembly orientation of the ribs and gaps. In some examples, the ribs can mitigate rotational movement of the LVDT core. Various rib features can hold the LVDT core on the LVDT rod.

[0058] An LVDT having a plunger rod coupled to a C-shaped core can be used in various aircraft flight controls, general engine controls, and within various power generation turbines. The C-shaped core can be advantageously used in high-vibration environments and high-temperature applications. The C-shaped core can provide a high holding force on the plunger rod, thereby reducing displacement on the rod in high-vibration environments. Even in high-temperature applications, the fine grains within the stamping core reduce batch-to-batch variability.

[0059] Since the C-shaped magnetic core can be designed as a press-fit spring, welding of the core to the probe rod can be optional. The C-shaped magnetic core design can reduce weight and can improve vibration performance. When welded to the probe rod, the C-shaped magnetic core can include a dual holding method.

[0060] The core can be stamped in a press to be punched and formed into a C-shaped cylinder. The stamping process can control the grain direction in the core blank. Additionally, the C-shaped magnetic core can be in an unannealed state. The unannealed C-shaped magnetic core can reduce the effects of handling, scratching, dropping, mechanical durability, and vibration on the sensitivity, linearity, and / or output of the LVDT into which the C-shaped magnetic core is assembled. In various examples, the C-shaped magnetic core can be annealed to advantageously increase the operating voltage. Thus, the C-shaped magnetic core can exhibit excellent temperature performance and vibration performance. Additionally, the C-shaped magnetic core can be produced with fewer processing steps and can be low-cost.

[0061] The LVDT core can be "blank stamped" and "formed stamped", which can advantageously control the grain direction. After stamping and forming, the core can be pressed onto the probe rod to a desired position. In some examples, the core and probe rod assembly can include redundant holding features (e.g., welding, brazing, gluing). The C-shaped core can be welded at one or both ends by single or multiple welding or brazing passes. In some examples, single-pass welding and welding both ends in a single pass can reduce the process cycle time. Before welding, brazing, and / or gluing, the C-shaped core can be moved to an exact position on the rod. The C-shaped core can be positioned by tools and / or embedded features such as threads on the probe rod or probe fittings. Various LVDT core designs can be implemented on single-channel or multi-channel LVDTs.

[0062] In some examples, the core 210 may be fixedly coupled to the cylindrical rod 205 in a non-slidable (e.g., holding) relationship, which can prevent the core 210 from shifting relative to the cylindrical rod 205 during operation. The present disclosure includes several ways / mechanisms for achieving such a non-slidable (e.g., holding) relationship between the core and the cylindrical rod. For example, Figures 5 to 12 illustrates various ways of configuring the core and the cylindrical rod in a non-sliding relationship. These include: end welds (at Figure 5 , Figure 6 and Figure 7in), longitudinal welds (in Figure 8 in), holding fixtures (in Figure 9 in), static friction enhancement features (in Figure 10 in), adhesives (in Figure 11 in), and end stop features (in Figure 12 in).

[0063] Multiple embodiments have been described. However, it should be understood that various modifications can be made. For example, favorable results can be achieved if the steps of the disclosed technology are performed in a different order, or if the components of the disclosed system are combined in a different manner, or if the components are supplemented with other components. Accordingly, other embodiments may be envisioned within the scope of the following claims.

Claims

1. An apparatus for use in a linear variable differential transformer (LVDT), the apparatus comprising: a core that extends along a first longitudinal axis and has a C-shaped cross-section, made of a metal sheet, the core having a core inner diameter and a core outer diameter, wherein the inner diameter defines a central cavity extending along the first longitudinal axis; and a cylindrical rod that extends along a second longitudinal axis, wherein the cylindrical rod is configured to be received in the central cavity of the core without a press fit such that when the cylindrical rod is received in the central cavity of the core, a longitudinal gap extends from a proximal end of the core to a distal end of the core, and wherein a first spot weld in direct contact with the core and the rod at the proximal end of the longitudinal gap is configured to mechanically fix the core to the rod, and a second spot weld in direct contact with the core and the rod at the distal end of the longitudinal gap is configured to mechanically fix the core to the rod, and wherein the core is fixedly coupled to the cylindrical rod in a non-slidable relationship.

2. The device according to claim 1, wherein The fixed coupling between the core and the cylindrical rod includes a circumferential weld between the cylindrical rod and the core at the distal end of the core.

3. The apparatus according to claim 1, further comprising a primary winding having a primary winding axis and two secondary windings having secondary winding axes, wherein, When the primary winding and the secondary winding are assembled with the core, the primary winding axis and the secondary winding axis are aligned with the first longitudinal axis.

4. The apparatus according to claim 3, further comprising a core housing having a core housing axis configured to be aligned with the first longitudinal axis when the core housing is assembled with the core.

5. The device according to claim 1, wherein, The core includes a nickel-iron alloy material.

6. The apparatus according to claim 1, wherein, The core includes a ferromagnetic material.

7. The apparatus according to claim 1, further comprising a C-shaped clamp configured to cooperate with a circumferential groove provided along an outer surface of the core at a distal end of the core for holding the core on the cylindrical rod when the cylindrical rod is assembled with the core.

8. The apparatus according to claim 1, wherein The cylindrical rod further includes a knurled pattern provided on an outer surface of the cylindrical rod, the knurled pattern being configured to provide increased static friction between the outer surface of the cylindrical rod and the inner surface of the core when the cylindrical rod is assembled with the core.

9. The apparatus according to claim 1, further comprising an end stop fixedly coupled to a distal end of the cylindrical rod, the end stop being configured to hold the core on the cylindrical rod when the cylindrical rod is assembled with the core.

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