Battery-free digital tire gauge

Abstract

A battery-less tire gauge (10), comprising: a housing (20); an electronic circuit assembly (110) housed in the housing (20) and including at least one sensor (48, 120) for measuring at least one parameter associated with a tire, a control processor (1160), a display (100) coupled to the control processor (1160), and a charging capacitor (1110). A converter (875) is coupled to the gear and ratchet assembly (70) in the housing (20) for converting the mechanical motion into electrical energy. A depressible handle (50) is operably coupled to the housing (20) and mechanically coupled to the gear and ratchet assembly (70), whereby depression of the handle (50) toward the housing (20) drives the gear and ratchet assembly (70) to produce mechanical motion that is converted to electrical energy by a converter (875). The converted electrical energy charges a charging capacitor (1110) to energize a control processor (1160) in the electronic circuit assembly (110) and cause a sensor (48, 120) to measure and display the measured at least one parameter.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] none. Technical Field

[0003] The present invention relates generally to sensing systems and, more particularly, to a battery-free digital tire gauge. Background Art

[0004] Periodically checking a vehicle's tire pressure and tread depth is recommended to ensure safe and efficient operation. Consequently, tire pressure gauges are common tools at the driver's disposal, as are tire tread depth gauges. Such devices typically include electronic components that can quickly, efficiently, and accurately measure and display relevant information. However, these electronic devices can consume significant amounts of energy and often require a power source such as batteries, cables, solar cells, and the like. A particular issue relates to the charging and / or recharging of such devices and energy sources. For example, significant environmental concerns arise regarding the manufacture, use, implementation, and / or disposal of batteries, cables, solar cells, and other such components used to power tire gauges. Batteries (e.g., lithium-ion batteries and / or other such energy sources commonly used in digital tire gauges) are environmentally wasteful, corrosive, and toxic, requiring the use of large quantities of raw materials, chemicals, and other hazardous elements that negatively impact the environment. Furthermore, batteries are prone to thermal issues, increasing the potential for fire or explosion. Similarly, solar cells, due to their use of toxic chemicals, have numerous negative consequences, including disposal and recycling issues, as well as the potential for overheating, among other issues. Furthermore, battery-powered devices require recharging and / or replacement during critical times when real-time, on-demand use of the device is often required, when such recharging or replacement may be impossible or difficult.

[0005] It would be highly desirable to provide alternative structures and techniques for tire gauges that alleviate one or more of the above-mentioned problems. Summary of the Invention

[0006] A battery-free digital tire gauge for measuring at least one parameter associated with a tire is disclosed. The battery-free digital tire gauge of the present disclosure offers numerous improvements and advantages over battery-powered tire gauges. The disclosed digital tire gauge requires no shipping or shipping approvals. There are no batteries to dispose of or replace, and leakage issues are avoided. Furthermore, while some batteries (e.g., lithium button cells) tend to be relatively safe, issues remain due to overcharging and / or thermal failure, fire, or explosive or volatile battery components. Furthermore, batteries are often undercharged and may fail at critical times when they are most needed. In the present disclosure, the battery-free digital tire gauge is configured to provide instant, real-time, and on-demand power without requiring concern for battery charge levels (since they are not present) or battery replacement. Furthermore, the battery-free digital tire gauge avoids storage concerns that must be addressed with battery-powered devices (or solar cells) due to potential temperature fluctuations in certain environments, such as overheating or overcooling conditions (or lack of light for the solar cell).

[0007] In one embodiment of the present disclosure, a battery-free digital tire gauge for measuring at least one parameter associated with a tire includes: a housing; an electronic circuit assembly in the housing, the electronic circuit assembly including at least one sensor for measuring at least one parameter associated with the tire. The electronic circuit assembly also includes a control processor, a display coupled to the control processor, and a charging capacitor. A converter is coupled to the gear and ratchet assembly for converting mechanical motion into electrical energy. A depressible handle (50) is operably coupled to the housing, the depressible handle mechanically coupled to the gear and ratchet assembly located in the housing, such that depressing the handle toward the housing drives the gear and ratchet assembly to generate mechanical motion, which is converted into electrical energy by the converter. The converted electrical energy generated by the driven gear and ratchet assembly charges the capacitor in the housing to energize the electronic circuit assembly and cause the at least one sensor to measure at least one parameter associated with the tire and display the measured at least one parameter on the display.

[0008] In one embodiment of a battery-free digital tire gauge, the housing includes a main body portion adapted to be held in a user's hand and including an opening for receiving an end portion of a depressible handle; and wherein, when the depressible handle is grasped in the user's hand and squeezed in a substantially linear direction toward the main body portion, the gear and ratchet assembly generates mechanical motion that is converted into electrical energy by a converter to charge a capacitor and energize a control processor in the electronic circuit assembly to enable at least one sensor to measure at least one parameter associated with the tire and to display the measured at least one parameter on a display.

[0009] In an embodiment of the present disclosure, the electronic circuit assembly further includes a low-dropout voltage regulator; a charge pump low-voltage detector for detecting when the capacitor voltage reaches a minimum threshold; and a logic gate coupled to an input of the low-dropout voltage regulator. The low-dropout voltage regulator maintains a consistent voltage for energizing the microprocessor controller in response to the charge pump low-voltage detector determining that the capacitor voltage is above the minimum threshold and an activation ON signal from the logic gate.

[0010] In an embodiment of the present disclosure, a charge pump low voltage detector is electrically coupled to a charging capacitor for converting an analog voltage signal output from the charging capacitor into a predetermined digital voltage value for input to a low dropout voltage regulator when the charge pump low voltage detector determines that the capacitor voltage is above a minimum threshold. The charge pump low voltage detector is further configured to generate a signal to cause a microprocessor to perform an operational shutdown when the capacitor voltage is less than the minimum threshold. The LDO regulator operates in response to the low voltage detector to provide a constant (e.g., 3V) output for powering a microcontroller processor.

[0011] In an embodiment of the present disclosure, the at least one sensor and the at least one parameter include a pressure sensor for sensing tire pressure and a depth sensor for sensing tire tread depth. In one embodiment, the pressure sensor includes a MEMs die. In one embodiment, the tread depth sensor includes a variable resistor and a movable rod or piston for converting mechanical displacement into an electrical analog signal.

[0012] In an embodiment of the present disclosure, a depressible handle includes an end portion including a toothed rack. The toothed rack of the depressible handle is mechanically coupled to a gear and ratchet assembly located in the housing, such that depressing the handle toward the body causes the toothed rack to drive the gear and ratchet assembly to generate mechanical motion, which is converted into electrical energy via a converter.

[0013] In an embodiment of the present invention, a gear and ratchet assembly includes a first gear including a ratchet drive portion and a second gear including a ratchet structure. The ratchet drive portion is configured to engage with the ratchet structure of the second gear and, in response to squeezing the depressible handle toward the housing, drive the second gear to rotate in a first direction, thereby causing the toothed rack to drive the first gear to rotate in the first direction.

[0014] In an embodiment of the present invention, the ratchet drive portion includes a pair of ratchet arm members arranged on opposite sides of the first gear. The ratchet structure of the second gear is positioned on an inner portion of the second gear and includes a series of angled teeth for unidirectional engagement with the ratchet arm members. That is, in one rotational direction, the ratchet arm member is configured to engage with the ratchet structure to drive the second gear, and in the opposite rotational direction, the ratchet arm member is configured to slide on the ratchet structure so that the second gear is not driven in the opposite or reverse direction. In an embodiment, a support platform coupled to the first gear is provided, which supports the first gear using arm members coupled at opposite ends of the support platform. The first gear is positioned concentric with the second gear along a vertical axis around the shaft, wherein the first arm member and the second arm member are arranged on a surface of the second gear orthogonal to the first axis for engaging with the ratchet structure.

[0015] In one embodiment, a depressible handle having a toothed rack is configured such that, by squeezing the handle, a spring force is applied, and the toothed rack on the handle engages and drives a first gear, which in turn drives ratchet arm members to rotate together. The ratchet arm members engage a ratchet structure on a second gear comprising a set of angled teeth to drive a second gear of a gear assembly, causing the engaged gear assembly to rotate together, thereby generating electricity for storage in a charging capacitor via a converter. Upon releasing the depressible handle, the spring force causes the handle to retract to a nominal position, while the ratchet structure prevents reverse rotation of the remaining portion of the gear assembly. In this manner, the engaged gear system rotates together, causing the converter to generate electricity for storage in the charging capacitor. When sufficient power resides in the capacitor, a consistent, predetermined voltage from a low-dropout voltage regulator activates a control processor of the electronic circuit assembly to enable tire gauge measurement and display. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A is a perspective view of a battery-free tire meter according to an embodiment of the present disclosure.

[0017] Figure 1B yes Figure 1A Right side view of the battery-free tire gauge.

[0018] Figure 2 is an exploded view illustrating components within the interior of a housing according to an embodiment of the present disclosure.

[0019] Figure 3 is a view showing components with the left side of a housing removed according to an embodiment of the present disclosure.

[0020] Figure 4A is a view illustrating components with the right side of the housing removed and the handle in a retracted state according to an embodiment of the present disclosure.

[0021] Figure 4B The present invention is a method of showing an embodiment of the present invention Figure 4A A more detailed view of the ratchet and gear assembly portion of the components shown in .

[0022] Figure 5 is a view illustrating components with the right side of the housing removed and the handle in a fully depressed state according to an embodiment of the present disclosure.

[0023] Figure 6A is a view illustrating various components with the right side of the housing removed and the handle in the process of returning to a retracted state according to an embodiment of the present disclosure.

[0024] Figure 6B The present invention is a method of showing an embodiment of the present invention Figure 6A A more detailed view of the ratchet and gear assembly portion of the components shown in .

[0025] Figure 7 is a more detailed view of a portion of a handle having a pivot member and a spring force according to an embodiment of the present disclosure.

[0026] Figure 8 yes Figure 4A A more detailed view of a portion of the ratchet and gear assembly.

[0027] Figure 9 It is from Figure 7 The view shown is opposite to the lower side view Figure 4A A more detailed view of a portion of the components of the ratchet and gear assembly.

[0028] Figure 10 、 Figure 11 and Figure 12 Schematic circuit components and a simplified diagram of the electronic circuit assembly of a battery-free tire meter according to an embodiment of the present invention are shown.

[0029] The same reference numbers are used to refer to the same parts throughout the drawings. DETAILED DESCRIPTION

[0030] It should be understood that the drawings and description of the present invention have been simplified to show elements relevant to a clear understanding of the present invention, while many other elements found in temperature, pressure, and depth measurement devices have been eliminated for the purpose of clarity. However, because such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. This disclosure is directed to all such variations and modifications known to those skilled in the art.

[0031] In the following detailed description, reference is made to the accompanying drawings which show, by way of example, specific embodiments in which the invention may be practiced. It will be understood that the various embodiments of the present disclosure, although different, are not necessarily mutually exclusive. Furthermore, specific features, structures or characteristics described herein in conjunction with one embodiment may be implemented in other embodiments without departing from the scope of the present invention. Furthermore, it will be understood that the position or arrangement of the various elements in each disclosed embodiment may be modified without departing from the scope of the present disclosure. Therefore, the following detailed description should not be taken as limiting, and the scope of the present disclosure is limited only by the appended claims, appropriately interpreted, and the full range of equivalents to which the claims are entitled. In the drawings, like reference numerals indicate like or similar functions throughout the several views.

[0032] Architecture Overview

[0033] Refer to Figure 1- Figure 12 , a battery-free tire gauge 10 for measuring at least one parameter associated with a tire is shown. The gauge 10 includes a housing 20 including a body portion 30 adapted to be held in a user's hand. A depressible handle 50 is operably coupled to the housing and mechanically coupled to a gear and ratchet assembly 70 (e.g., a plurality of gears) located in the housing 20. Figure 2 ) for generating mechanical energy when the handle is pressed in the direction toward the main body of the housing. The energy conversion device 875 in the housing converts the generated mechanical energy into electrical energy in response to the generated mechanical energy, and the electrical energy is supplied to the large charging capacitor 1110 ( Figure 10 ) for energizing and activating control processor 1160. Energizing control processor 1160 causes a sensor (such as pressure sensor 48 or tread depth sensor 120) to measure at least one parameter associated with the tire and display the measured at least one parameter on display 100.

[0034] Tire pressure can be measured via a nozzle 40 that includes a gasket 44 surrounding a suction tube 46 that communicates pressure fluid to a pressure sensor 48 ( Figure 4A As non-limiting examples, pressure sensor 48 may be implemented as a piezoelectric sensor, such as a diaphragm and semiconductor strain gauge connected in a bridge configuration, a capacitive sensor (e.g., fixed plate / moving plate), a thin film sensor, a ceramic thick film sensor, a MEMs sensor, and / or other such pressure sensing devices, as understood by those skilled in the art.

[0035] The tire gauge 10 may further and / or alternatively include a tread depth measuring device 120. The tread depth measuring device 120 (see, e.g., Figure 4A) includes a variable resistor 1270 electrically connected to the printed circuit board 112 of the electronic circuit assembly 110. As shown, a slider or joystick 1271 is coupled to a measuring rod or head 1272, which is movable along a longitudinal axis 1214 by a drive portion 1212. The measuring rod 1272 can be moved by a longitudinal slide along the upper portion of the housing on the outer surface of the housing (see Figure 1B ) and extends from the housing through opening 1273. When slider 1271 is moved along the longitudinal slot in the upper portion of the housing, the joystick of variable resistor 1270 moves relative to it, causing the variable resistor to change its resistance output. The change in resistance is then converted into a corresponding frequency by a distance conversion circuit in the control processor, and then into a readable distance reading for display on the screen of display 100.

[0036] The electronic circuit assembly 110 is housed, for example, on a printed circuit board 112 in the housing 20 and includes control electronics including a control processor (e.g., a microcontroller) for controlling, receiving, and processing sensed data parameters from the pressure sensor 48 and the tread depth sensor 120. The electronic circuit assembly includes a control processor (e.g., a microprocessor 1160 ( Figure 11 )), a display 100 (eg, LCD 1100, coupled to a control processor 1160, Figure 11 ) and a large capacitance charging capacitor 1110 (see Figure 10 ).

[0037] Such as coil converter 875 (see Figure 4A ) is coupled to the gear and ratchet assembly 70 for converting mechanical motion from the assembly into electrical energy. The depressible handle 50 is operably coupled to the housing 20, and the handle 50 is mechanically coupled to the gear and ratchet assembly 70 located in the housing 20.

[0038] For example, in Figure 2 、 Figure 3 Figure 4 Figure 5 As best seen in FIG6 , the handle 50 includes a first end portion 52 and a second end portion 58 opposite the first end portion. The first end portion 52 includes a relatively linear toothed rack 54 for engaging the first toothed gear 140 of the gear and ratchet assembly 70. The second end portion 58 includes a circular pivot member 59 having a through hole that is pivotally coupled to a portion of the housing via an axis 62. The axis 62 is secured through a central portion of the pivot member 59 via a complementary support post. The pivot member 59 is configured to rotate about the axis 62 to a predetermined extent. The pivot member 59 includes a spring force member 240 (see Figure 4A 、 Figure 5 、 Figure 6A 、 Figure 7 ), the spring force member 240 is arranged around the axis 62 and is constrained to the pivot member 59 ( Figure 7 ) between the parallel sections 59a and 59b. More specifically, the spring 240 includes a first end and a second end, wherein the center section is wound around the axis 62 and held between the parallel sections 59a and 59b. As shown in the figure, the first end of the spring 240 is away from the pivot member and extends a predetermined distance from the pivot member to contact the stopper 210 / 212 ( Figure 4A ) engagement. The respective ends 52 and 58 of the handle 50 are received in the housing openings 32 and 34 (see, for example, Figure 2 ). As shown in Figures 4, 6 and Figure 7 As best shown in , when the spring 240 is deformed from its free state (e.g., the handle is pressed), the spring stores energy in the form of elastic potential energy, and when the spring is released (e.g., the spring is released), the elastic potential energy is released. It will be understood that the housing and / or handle can take a variety of shapes or forms. However, in an embodiment, an important feature of the device is that the housing body is configured to be held in the hand of a user, and the handle is positioned and configured so that it can be grasped and pressed in a direction toward the housing (and subsequently released in a direction away from the housing) so that the rack portion 54 of the handle can be moved substantially in a direction toward the housing (and subsequently moved away from the housing) and engage with the ratchet assembly, together with the pivoting of the opposite end portion 59 of the handle.

[0039] As shown in the figures, complementary post connectors 210a-210d and 210a'-210d' connect and secure the two sides of the housing 20. Fasteners such as screws or other connectors can be inserted from the exterior surface of the housing into the housing, generally designated 210 ( Figure 1B ) in a column connector to hold or secure the housing 20 together.

[0040] Shell support column 220 ( Figure 2 ) and corresponding support posts (not shown) located on the opposite half of the housing 20 are configured to receive and retain the shaft 240 so as to enable the gear and ratchet assembly 70 to rotate.

[0041] Support elements 220a-220d ( Figure 4A ) is adapted to receive, support and secure the generator transmission gear mechanism 80 within the housing 20.

[0042] like Figure 4AAs best shown in FIG, support member 210c includes a stop member 212 that is arranged as a stop to prevent movement of spring 240 in the direction of arrow D when handle 50 is pressed (biased) in a direction toward housing 20 (arrow A). Figure 6A As best shown in FIG, when the handle is released, the spring 240 provides a return force (arrow D') that moves the handle back to its initial (unbiased) position (arrow A').

[0043] Still combined Figure 6A-6B and Figure 7 refer to Figure 4A-4B and Figure 5 , by squeezing or pressing the handle 50 toward the housing 20, a force F is applied in direction A, causing the toothed rack portion 54 of the handle end 52 to engage with the first pinion 140 to drive the gear and ratchet assembly 70 to generate mechanical motion, which is converted into electrical energy by the converter 875. More specifically, when the user grasps the housing of the handheld device (e.g., in the palm of their hand), and grasps and squeezes the handle (e.g., with their fingers), thereby applying a biasing force F sufficient to overcome the spring force to the handle end 52, this causes the toothed rack portion 54 of the handle to move in direction A, which in turn causes rotational motion of the first pinion 140 in a rotational direction B. This, in turn, causes the ratchet arm members or pawls 120a, 120b to index and engage the internal ratchet structure of the second gear 142 to rotate the second gear in the same clockwise direction B′ as B. As is understood in the art, the ratchet structure 144 of the second gear 142 includes a plurality of uniform but asymmetrical teeth, each of which has a moderate slope on one edge and a steeper slope on the other edge. The ratchet arm members 120a, 120b index the internal pinion, which is spring-loaded and applies force to the external gear that runs the motor. The blades in the pinion include retaining springs that snap and hold in place to transfer energy to the external gear that drives the motor. In this way, the energy storage spring is rotated by the handle. The ratchet only provides one-way motion (preventing reciprocating or bidirectional motion), with the second gear 142 being locked by the ratchet. When the handle 50 is squeezed, the rotation of the second gear 142 causes the external teeth 142a of the second gear 142 to engage with the external teeth 832 of the third gear 830, causing the third gear to rotate in the opposite direction to the direction of gears 140 and 142.

[0044] like Figure 9As best shown in FIG, the gear transmission system 80 is mechanically coupled to the gear and ratchet system 70 and includes a third gear 830, dual gear assemblies 840 and 850, and a gear 860. As shown, the dual gear 840 is mechanically coupled to the third gear 830 and the dual gear 850. The dual gear 840 includes a lower fourth gear 842 having teeth (not shown) that engage with the teeth 832 of the third gear 830. The dual gear 840 further includes an upper fifth gear 844 having teeth 844a.

[0045] The dual gear 850 includes an upper sixth gear 852 having teeth 852a, wherein teeth 852a engage teeth 844a of the fifth gear 844. The dual gear 850 further includes a lower seventh gear 854 having teeth 854a, wherein teeth 854a engage teeth 860a of the eighth gear 860. As is understood in the art, the eighth gear 860 is rotationally coupled to a coil converter 875 via shaft 864 to convert rotational motion into electrical energy at the converter's output. The third gear 830, the first dual gear 840, and the second dual gear 850 are rotatable about shafts 836, 846, and 856, respectively, which are fixedly connected to the first surface 800a of the support platform 800. In the disclosed embodiment, the coil converter 875 is disposed on a second surface 800b opposite the first surface 800a. The gear train provides the rotational speed to enable the converter or motor to rotate quickly enough to generate sufficient electrical energy to power the device. Module 875 represents a converter with windings, such as a spin converter with permanent magnets.

[0046] like Figure 8 As best shown in FIG. 1 , the ratchet arm members 120a, 120b are preferably positioned 180 degrees apart and engage corresponding ratchet pinions or grooves 144 to lock the position so that the second gear cannot be reversed. That is, in one rotational direction (by pressing the handle in direction A), the ratchet arm members are configured to engage the ratchet structure ( Figure 4A 、 Figure 4B and Figure 5 ) engages to drive the second gear 140 in the clockwise direction B. Figure 5 The handle is shown pressed maximally toward the housing. Figure 6A As shown, when the handle 50 is released, the bending spring 240 rebounds (D') to drive the handle back (in direction A'). The teeth 54 on the handle 50 drive the first gear 140 to rotate in the opposite direction (i.e., rotate in the counterclockwise direction B"), and the ratchet arm member disengages from the second gear 142 and is in the ratchet structure ( Figure 6A) so that the second gear is not driven in the opposite or reverse direction. In an embodiment, the support platform 72 supports the first gear 140 and has a pair of ratchet arm members connected thereto. The support platform 72 with the ratchet arm members is arranged on the surface of the second gear 142 and is surrounded by the angled groove or ratchet pinion 144 for one-way engagement with the ratchet arm members 120a, 120b.

[0047] Electronic circuit components

[0048] Now refer to Figure 10-12 , combined with Figure 4A The tire meter 10 includes an electronic circuit assembly 110 that is disposed on a printed circuit board (PCB) 112 within the housing 20. The converter 875 is electrically coupled to the electronic circuit assembly ( Figure 10 ). The electronic circuit assembly 110 includes a large capacitance charging capacitor 1110 (eg, a 2200 microfarad (uF) capacitor), a control processor 1160, and an LCD 1100 ( Figure 11 The circuit further includes a low-dropout regulator 1140, a charge pump low-voltage detector 1120 for detecting when the capacitor voltage reaches a minimum threshold, and a logic gate coupled to an input of the low-dropout regulator. The low-dropout regulator (LDO) 1140 maintains a consistent voltage for energizing the microprocessor controller 1160 in response to the charge pump low-voltage detector 1120 determining that the capacitor 1110 voltage is above the minimum threshold and receiving an activation ON signal from the logic gate.

[0049] In an embodiment of the present disclosure, the charge pump low voltage detector 1120 is electrically coupled to the charging capacitor 1110 for converting an analog voltage signal output from the charging capacitor into a predetermined digital voltage value for input to the low dropout regulator 1140 when the charge pump low voltage detector determines that the capacitor voltage is above a minimum threshold. The charge pump low voltage detector is further configured to generate a signal to cause the control processor 1160 to perform an operation shutdown when the capacitor voltage is less than the minimum threshold.

[0050] exist Figure 11In the circuit diagram of FIG, a winding converter or generator 875 is shown electrically coupled to transistors Q2 and Q3 (e.g., NPN transistors) for providing a full-bridge rectifier circuit. As is known in the art, a full-bridge achieves a full-wave voltage, thereby increasing the amplitude of the voltage output therefrom. Diode D3 operates to prevent any undesirable reverse current. Capacitor 1110 (C3) is a relatively large capacitor and represents a primary energy storage element and is charged by the circuit. A charge pump voltage converter 1120 responds to the large charge stored on large capacitor 1110 for energy transfer and voltage reduction to produce a reduced output voltage that is regulated to a predetermined level (e.g., a 2.2 volt level) so that it can be used by a processor 1160 (e.g., a microprocessor controller) operating at 2.2 volts.

[0051] In operation, in response to the handle 50 being squeezed toward the housing 20 to generate mechanical energy, the AC voltage output from the generator or motor 875 is converted to DC volts via the charge pump 1120, and the low dropout voltage (LDO) module 1140 responds to the charge pump voltage converter 1120 to make it a regulated 3 volt DC.

[0052] exist Figure 11 In the circuit, the charge pump 1120 operates as a low voltage detector (i.e., voltage drop control), which enables the system to determine whether there is sufficient power in the circuit to perform the necessary functions (e.g., make pressure measurements, process data to determine the necessary pressure values, activate and communicate with the display, etc.). By implementing the large capacitor 1110 in combination with the charge pump 1120, the system can maintain the required energy level, thereby avoiding any harmful "hang state" or unrecoverable machine state by properly powering on (when sufficient energy is present) and / or powering off (when there is insufficient energy to continue active measurement processing, but there is still sufficient energy to perform a proper power-off) the circuit. The low power voltage detector 1120 provides monitoring of the required energy level, including the regulated system voltage.

[0053] In one embodiment, charge pump 1120 is implemented as an STM1061 2.2V low-power voltage detector manufactured by STMicroelectronics. A precision voltage reference and comparator monitors the VCC input and compares it to specified voltage threshold conditions. When VCC drops below the specified trip point threshold, the output (OUT) is forced low and remains active low as long as the VCC input remains below VTH-plus a hysteresis voltage (VHYST). Detector 1120 is configured to output the correct logic state when VCC drops to 0.7V and to ignore fast transients on VCC.

[0054] A low-dropout (LDO) regulator 1140 is configured downstream of the charge pump 1120 and is responsive to the output of the charge pump 1120 to provide a regulated 3-volt output. In an embodiment, the LDO regulator 1140 is an XC6206P332MR LDO regulator and is a fixed-output positive low-dropout (LDO) regulator. The module operates as a high-precision, high-voltage positive voltage regulator manufactured using CMOS and laser trimming techniques. The device provides high current with minimal dropout voltage. The LDO may include a current limiter circuit, a driver transistor, a precision voltage reference, and an error correction circuit, and is compatible with low-ESR ceramic capacitors. The current limiter's foldback circuit also operates as an output current limiter and short-circuit protection for the output pin. The output voltage can be set internally by laser trimming.

[0055] This small, low-power device is ideal for portable applications and is available in different space-saving packages (e.g., the SOT23-3 and SOT323-3 (SC70-3) packages).

[0056] Still refer to Figure 11 , a very small resistor R11 acts as a protective impedance element (having a small impedance) to prevent a short circuit, allowing a very large capacitor to be charged through a very small impedance (R11). The system is designed to place the maximum amount of voltage or energy charge on the capacitor, regardless of size, and then uses a small charge pump 1120 to reduce the voltage to a level (i.e., regulate it to a predetermined level (e.g., 2.2 volts)) so that it can be used by the microcontroller at 2.2 volts. Since element 1120 is a small charge pump device that generates a DC voltage from the AC voltage output from the motor generator 875, the LDO module 1140 downstream of the charge pump 1120 operates to produce a regulated output of 3 volts (line 5).

[0057] Resistive element R12 and diodes D2 and D4 operate as a logic gate (OR gate) to keep LDO regulator 1140 ON, which keeps microcontroller 1160 powered and energized for performing normal meter operations such as measurement of pressure received at the nozzle, measurement of tread depth from the variable resistor circuit, and display of the resulting measurement and units on the display.

[0058] System Operation

[0059] As will be understood from this disclosure, the principle of a battery-free digital tire gauge is electromagnetic induction. Typically, a coil generates an induced electromotive force in a rotating magnetic field. The basic structural components of a "manual generator" include a stator and a rotor. The stator is typically a permanent magnet, and the rotor is a coil. When the internal coil passes through brushes to form a closed loop with the external circuit, a current is generated in a rectifier circuit with a large capacitor (e.g., element 1100), which is used to store energy. In an embodiment, the minimum operating voltage of the microcontroller unit 1160 (MCU) is 2.4V. The MCU (e.g., CSU8P1001) operates when the stored energy can be supplied with a voltage greater than 2.4V via an external LDO (e.g., XC6206P25) regulator. The MCU's internal LDO provides a stable 2.8V voltage for the LCD and a stable 2.4V voltage for the sensor power supply. The MCU collects the sensor analog signal data and calculates the pressure value through internal analog-to-digital conversion, which is then displayed on the LCD. When the power continues to be consumed and the LDO regulation voltage drops below 2.4V, the MCU will stop working and the battery-less tire pressure gauge will shut down.

[0060] In operation, in order to maintain the microprocessor controller in an active or ON state, a valid logic signal (PT22) from the controller is required and sufficient voltage (exceeding a predetermined threshold, e.g., 0.7V) is provided on the output line 1 of the charge pump 1120. The microcontroller connection is PT22. Under these conditions, the LDO regulator 1140 provides a constant (e.g., 3V) output voltage signal for powering the microprocessor controller and enabling measurement, processing, and display of the measured pressure and / or measured fatigue tread depth received at the nozzle. The output (5) voltage signal of the LDO 1140 is further processed by downstream capacitors C2 (relatively large capacitor) and C1 (relatively small capacitor). Capacitor C2 (e.g., in the relative range of 1uF capacitance) is designed to store or smooth the energy output by reducing ripple or transient signals output from the LDO. Capacitor C1 (e.g., a ceramic capacitor in the relative range of 0.1 microfarad (uF) capacitance) is designed to mitigate higher frequency noise. In the system according to the embodiment of the present disclosure, the motor is a noise generator that needs smoothing to reduce noise. The microcontroller further includes software code or software algorithms to reduce signal ripple and noise fluctuation.

[0061] Figure 11 An exemplary microprocessor controller 1160 is shown in greater detail, along with associated electronic components ( Figure 12 ) and electronic circuit 110 ( Figure 10By way of example, the display 100 may be embodied as an LCD display circuit 1100 for displaying associated unit values and measurement data generated by the measured pressure and / or tread depth gauge measurement results.

[0062] like Figure 12 As shown, sensor element circuit 11500 is an exemplary pressure sensor, such as, for example, a MEMs die manufactured by UniSense, for detecting pressure received from the metering nozzle 40 (Figure 1).

[0063] The switch element circuit 11530 is a depressible switch element that changes the units on the display in response to the pressing of the button 530 on the housing 20 (Figure 1).

[0064] As a non-limiting example, memory circuit element 11580 ( Figure 11 ) is shown electrically coupled to the microprocessor controller 1160 and embodied as an EEPROM for factory programming to enable flashing and / or writing of memory, including calibration coefficients. Circuit element 11520 ( Figure 12 ) is a connector that serves as an interconnect between circuit boards and includes port lines and reset lines that operate for the purpose of programming circuits.

[0065] Circuit element 11510 ( FIG. 13 ) represents a fine-tuning module that includes a resistance adjustment module for fine-tuning of a tread depth module, such as tread depth gauge 120 ( FIG. Figure 3 ) of the slide potentiometer.

[0066] Operation Scenario

[0067] Refer to Figure 1- Figure 12 , when the user squeezes the depressible handle ( Figure 4A 、 Figure 5 ), the spring 240 bends, and the toothed rack on the handle drives the first gear 140 to rotate, which in turn drives the ratchet to rotate together. As the ratchet engages the second gear 142, it drives the second gear to rotate, and the engaged gear transmission system 830, 840, 850, 860 (the third gear, the fourth gear, the fifth gear, the sixth gear, the seventh gear, and the eighth gear) rotates to generate mechanical motion, which is converted into electrical energy by the converter 875 to be stored in the capacitor 1110. When there is sufficient power in the capacitor 1110, the consistent power (e.g., 3V) through the LDO regulator will activate the control processor.

[0068] In one embodiment of the present disclosure, an ultra-low clock and ultra-low power controller is provided for use in the configurations described herein, wherein the bridge or pressure sensor is gated to conserve power (i.e., intermittently powered) to maximize the period of time the unit can remain on. Since the bridge or sensor is essentially a resistor, it consumes power. Therefore, the microprocessor controller operates to gate the sensor by multiplexing, sampling, disconnecting, and then switching on to quickly obtain a reading. By operating the device in this manner with relatively few electronic components, and the reduced power levels required due to the reduced number of electronic components and their relatively low power requirements, self-heating is minimal, which also avoids further issues with battery-free tire gauge devices.

[0069] In an alternative embodiment, a stack of piezoelectric elements may be used instead of a converter and gear train to charge the charging capacitor 1110 .

[0070] In another alternative embodiment, the device includes a retaining spring rather than a trigger, which moves the magnet through the coil rather than running the motor and gear train.

[0071] As previously discussed, in operation, the meter 10 is powered by pressing the handle 50 toward the meter body 30, which is connected via the gear and ratchet assembly 70 and the gear generator system 80, to generate mechanical motion within the housing, which is converted into electrical energy sufficient to charge the capacitor 1110, thereby enabling the voltage to close the circuit (via the converter, capacitor, charge pump, and LDO) and start the microprocessor 1160 and corresponding electronic components. With the capacitor 1110 charged and the unit operational, the microprocessor controller strobes the pressure sensor bridge (via the A / D controller) for detecting pressure readings via the sensor 11510.

[0072] Once the device senses pressure, the microprocessor accumulates the number of counts and factors it according to an algorithm (e.g., number of counts per psi), formats the value, and writes it to the LCD controller, which displays the internal pressure value in decimal form, as will be understood by those skilled in the art. A similar process is performed for tire tread measurements, as described above. Because all processing performed in the tire gauge of the present invention is accomplished without any batteries, environmental, regulatory, volatility, rechargeability, thermal, and time issues associated with on-demand measurements are minimized, if not eliminated.

[0073] The tire gauge is calibrated to enable charging when the handle is forced toward the body. The spring-triggered retraction of the handle provides a quick response to reset the handle to a nominal or unbiased position, enabling additional biasing of the operating device as needed. When the energy in circuit 110 drops below a predetermined level (e.g., after a timeout period), display 100 is disconnected. Circuit module 1120 is configured to protect the device from a locked-out state (e.g., caused by improperly powering off or powering on the circuit), where the device enters an undefined state or mode from which the microprocessor cannot recover. In other words, when low-voltage detector 1120 detects a voltage at its input that is less than a threshold condition (e.g., 7V or 8V caused by the discharge of energy from capacitor 1110), detector 1120 de-energizes circuit 110 via a logic signal, thereby avoiding complete (or constant) drain of the circuit and potentially undefined state conditions associated with the circuit. This prevents the oscillator or processor from shutting down and entering an undefined state from which it cannot recover.

[0074] Operating parameters:

[0075] In one embodiment, the operating range requirements of a battery-free tire gauge according to the present disclosure include:

[0076] 1. Operating range:

[0077] a) Pressure: 5psi~99psi / 0.35bar~6.80bar / 35kPa~680kPa / 0.4kg / cm 2 ~7.00kg / cm 2 ;

[0078] b) Depth: 0mm-15mm / 0-19 / 32 inches;

[0079] 2. Accuracy:

[0080] a) Pressure: ±(1%+1LSD);

[0081] b) Depth: ±0.2mm / ±1 / 32 inch;

[0082] 3. Activation pressure: >5psi / 0.35bar / 35kPa / / 0.4kg / cm 2 ;

[0083] 4. Measurement unit: psi / bar / kPa / kg / cm 2 / inch / mm;

[0084] 5. Display format: 8.8 / .8.8PSI / BAR / KPA / Kg / cm 2 / INCH / MM;

[0085] 6. Function: automatic zeroing and automatic shutoff.

[0086] Pressure measurement mode:

[0087] In an exemplary embodiment, the user squeezes the handle of the gauge to generate enough mechanical energy to electrical energy to initialize (i.e., wake up) the gauge. The display will first flash a full screen initialization. The LCD display will show "0.0, 0.00, or 0" along with the last measured mode and a unit icon. If the last measured mode was tread depth mode, pressing the "ON" button again causes the gauge to enter pressure mode. Press and hold the ON button for T = 2 seconds to change units, and the unit icon will flash (press ON to sequentially change units psi / bar / kPa / kg / cm 2 ). If no further action is taken within a time of T=3 seconds, the unit icon will stop flashing, indicating confirmation and confirmation of the selection. Next, the pressure reading is displayed by placing and holding the nozzle of the meter on the valve stem. The pressure reading is maintained on the LCD display when the meter is removed from the valve stem. In order to convert the pressure reading to the unit of measurement on the LCD, the user will push the "ON" button for T=2 seconds to activate (flashing) the current unit icon. Pressing the ON button selects the unit and causes the pressure reading to be converted to the selected unit. The meter will then reset to zero and be displayed as zero (in the relevant unit) on the LCD display. If the user does not further activate the meter by squeezing the handle, the meter will disconnect after a time of T=1 minute from start-up.

[0088] Tread depth measurement mode:

[0089] In an exemplary embodiment, the user squeezes the gauge's handle to generate sufficient mechanical and electrical energy to initialize (i.e., wake up) the gauge. The display will initially flash full screen. The LCD display will show "0.0, 0.00, or 0" along with the last measurement mode and a unit icon. If the last measurement mode was pressure mode, pressing the "ON" button again causes the gauge to enter tread depth mode. Press and hold the ON button for T = 2 seconds to change the depth measurement unit, and the unit icon will flash (press ON to sequentially change units from INCH / MM). If no further action is taken within T = 3 seconds, the unit icon will stop flashing, indicating confirmation of the selection (if necessary, press ON again to measure tire pressure later). Next, slide the button on the side of the gauge housing until the metal rod contacts the bottom of the groove. Push the gauge downward toward the tire until the flat surface of the gauge is on the tread surface, and the tire depth reading will be displayed. If the user does not further activate the gauge by squeezing the handle, the gauge will shut off after T = 1 minute from activation.

[0090] It should be noted that embodiments of the present invention may include any number of additional components not shown in the simplified schematic diagrams presented herein for the sake of brevity.

[0091] Therefore, a battery-free digital tire gauge for measuring at least one parameter associated with a tire is disclosed, the battery-free digital tire gauge comprising: a housing; an electronic circuit assembly in the housing, the electronic circuit assembly including at least one sensor for measuring at least one parameter associated with the tire. The electronic circuit assembly further comprises a control processor, a display coupled to the control processor, and a charging capacitor. A converter is coupled to the gear and ratchet assembly for converting mechanical motion into electrical energy. A depressible handle (50) is operably coupled to the housing, the depressible handle mechanically coupled to the gear and ratchet assembly located in the housing, such that depressing the handle toward the housing drives the gear and ratchet assembly to generate mechanical motion, which is converted into electrical energy by the converter. The converted electrical energy generated by the driven gear and ratchet assembly charges the capacitor in the housing to energize the microprocessor in the electronic circuit assembly and cause the at least one sensor to measure at least one parameter associated with the tire and display the measured at least one parameter on the display.

[0092] In one embodiment of a battery-free digital tire gauge, the housing includes a main body portion adapted to be held in a user's hand and including an opening for receiving an end portion of a depressible handle; and wherein, when the depressible handle is grasped in the user's hand and squeezed in a substantially linear direction toward the main body portion, the gear and ratchet assembly generates mechanical motion that is converted into electrical energy by a converter to charge a capacitor and energize a control processor in the electronic circuit assembly to enable at least one sensor to measure at least one parameter associated with the tire and to display the measured at least one parameter on a display.

[0093] In an embodiment, the electronic circuit assembly further includes: a low dropout voltage regulator; a charge pump low voltage detector for detecting when the capacitor voltage reaches a minimum threshold; and a logic gate coupled to an input of the low dropout voltage regulator; wherein the low dropout voltage regulator maintains a consistent voltage for energizing the microprocessor controller in response to the charge pump low voltage detector determining that the capacitor voltage is above the minimum threshold and an activation ON signal from the logic gate.

[0094] In an embodiment, the depressible handle includes an end portion, the end portion including a toothed rack; and wherein the toothed rack of the depressible handle is mechanically coupled to a gear and ratchet assembly located in the housing, such that pressing the handle toward the body causes the toothed rack to drive the gear and ratchet assembly to generate mechanical movement, and the mechanical movement is converted into electrical energy through a converter.

[0095] In an embodiment, the gear and ratchet assembly further includes: a first gear, the first gear including a ratchet drive portion; a second gear, the second gear including a ratchet structure; wherein the ratchet drive portion is configured to engage with the ratchet structure of the second gear and drive the second gear to rotate in a first direction in response to squeezing the depressible handle toward the housing, so that the toothed rack drives the first gear to rotate in the first direction.

[0096] In an embodiment, when the depressible handle is released, the spring force applied by the retaining spring causes the depressible handle to retract to a nominal position, the toothed rack drives the first gear to rotate opposite to the first direction, and simultaneously the ratchet driving portion slides opposite to the ratchet wheel of the ratchet structure of the second gear, thereby preventing the second gear from rotating in the opposite direction.

[0097] In an embodiment, the ratchet drive comprises a pair of ratchet arm members. In an embodiment, the pair of ratchet arm members are positioned 180 degrees apart and connected to the first gear.

[0098] In an embodiment, a support platform supporting the first gear has a pair of ratchet arm members connected thereto.

[0099] In an embodiment, a support platform having a ratchet arm member is arranged on a surface of the second gear and surrounded by a set of angled teeth, wherein the ratchet arm members are engageable with the set of angled teeth to rotate the second gear in a first rotational direction when the toothed rack is engaged with the first gear.

[0100] In an embodiment, the gear and ratchet assembly further comprises a plurality of transmission gears operably coupled between the second gear and the converter, wherein a first transmission gear of the plurality of transmission gears engages with and is rotatably driven by the second gear, and wherein a last transmission gear of the plurality of transmission gears engages with and drives a shaft of the converter.

[0101] In an embodiment, the spring force comprises a metal spring coupled to an end portion of the depressible handle.

[0102] In an embodiment, the plurality of transfer gears further includes a first set of double gears and a second set of double gears coupled between the first transfer gear and the final transfer gear.

[0103] In an embodiment, the battery-free digital tire meter further includes a ripple filter including a second capacitor, and the second capacitor is coupled to the output terminal of the LDO regulator and is configured to reduce a ripple voltage input to the control processor.

[0104] In an embodiment, the battery-free digital tire meter further includes a noise filter including a third capacitor coupled to an output terminal of the LDO regulator and configured to reduce high frequency noise.

[0105] In an embodiment, the charging capacitor has a capacitance that is at least 1000 times greater than the capacitance of the second capacitor.

[0106] In an embodiment, the second capacitor has a capacitance at least 100 times greater than a capacitance of the third capacitor.

[0107] These exemplary descriptions are provided by way of example only, and other embodiments for implementing the processes described herein may be contemplated by those skilled in the relevant art(s) without departing from the intended scope of the present disclosure. For example, the processes may be implemented, by way of example, by a memory containing instructions that, when executed by a processor, cause the steps of a method for measuring tire pressure and / or tread depth to be performed. It will be understood that these may also be implemented in hardware. Thus, the entire process or any portion thereof may be performed in hardware, software, or any combination of hardware and / or software. The software may be embodied in a non-transitory machine-readable medium on which software instructions may be stored, the stored instructions, when executed by a processor, causing the processor to perform the steps of the method described herein. Furthermore, while a depressible handle and housing in conjunction with a gear and ratchet assembly and converter generator have been shown and described for delivering electrical energy to a charged capacitor to power electronic circuit components and a control processor, it is contemplated that mechanical motion may also be utilized to excite a piezoelectric (or piezoelectric ceramic) generator, such as a PZT stack or other configuration that may be subjected to vibrational forces or shock, or a coil and magnet in relative rotational motion, or other converter devices that may be subjected to mechanical motion to generate electrical energy within a housing for powering a control processor, sensors, detectors, and the like.

[0108] Although the foregoing invention has been described with reference to the above-mentioned embodiments, various modifications and changes can be made without departing from the spirit of the present invention. Therefore, all such modifications and changes are considered to be within the scope of the appended claims. Therefore, the specification and the drawings are considered to be illustrative and not restrictive. The drawings forming a part of this document show, by way of example and not limitation, specific embodiments in which the subject matter can be practiced. The illustrated embodiments are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments can be utilized and derived therefrom so that structural and logical substitutions and changes can be made without departing from the scope of this disclosure. Therefore, the specific embodiments should not be considered restrictive, and the scope of the different embodiments is limited only by the appended claims and the full scope of equivalents to which these claims are entitled.

[0109] Such embodiments of the subject matter of the present invention may be referred to herein, individually and / or collectively, by the term "invention," which term is used for convenience only and is not intended to actively limit the scope of this application to any single invention or inventive concept (if more than one is actually disclosed). Thus, although specific embodiments have been shown and described herein, it should be understood that any arrangement intended to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations and variations of the various embodiments. In conjunction with the above embodiments, as well as other embodiments not specifically described herein, it will be apparent to those skilled in the art upon reviewing the above description.

Claims

1. A battery-free digital tire gauge for measuring at least one parameter associated with a tire, comprising: case; an electronic circuit assembly within the housing, the electronic circuit assembly including at least one sensor for measuring at least one parameter associated with the tire, the electronic circuit assembly further comprising a control processor, a display coupled to the control processor, and a charging capacitor; a converter coupled to the gear and ratchet assembly for converting the mechanical motion into electrical energy; a depressible handle operably coupled to the housing, the depressible handle mechanically coupled to the gear and ratchet assembly located in the housing, and having a retaining spring such that depression of the handle toward the housing drives the gear and ratchet assembly to produce mechanical motion, which is converted into electrical energy by the converter; wherein the converted electrical energy generated by the driven gear and ratchet assembly charges the capacitor in the housing to energize the control processor of the electronic circuit assembly and cause the sensor to measure at least one parameter associated with the tire and display the measured at least one parameter on the display.

2. The battery-free digital tire gauge according to claim 1, wherein: The housing includes a main body portion adapted to be held in a hand of a user, and the main body portion includes an opening for receiving an end portion of the depressible handle; and wherein, when the depressible handle is grasped in a user's hand and squeezed toward the main body in a substantially linear direction, the gear and ratchet assembly generates mechanical motion, which is converted into electrical energy by a converter to charge the capacitor and stimulate the control processor in the electronic circuit assembly to enable the at least one sensor to measure at least one parameter associated with the tire and display the measured at least one parameter on the display.

3. The battery-free digital tire gauge according to claim 1, wherein: The electronic circuit assembly further comprises: Low dropout voltage regulator; a charge pump low voltage detector for detecting when the capacitor voltage reaches a minimum threshold; and a logic gate coupled to an input terminal of the low dropout regulator; The low dropout regulator maintains a consistent voltage for energizing the microprocessor controller in response to the charge pump low voltage detector determining that the capacitor voltage is above the minimum threshold and an activation ON signal from the logic gate.

4. The battery-free digital tire gauge according to claim 1, wherein: The desqueezable handle includes an end portion, the end portion including a toothed rack; and wherein the toothed rack of the desqueezable handle is mechanically coupled to the gear and ratchet assembly located in the housing, so that pressing the handle toward the body causes the toothed rack to drive the gear and ratchet assembly to generate the mechanical motion, and the mechanical motion is converted into electrical energy by the converter.

5. The battery-free digital tire gauge according to claim 4, wherein: The gear and ratchet assembly comprises: a first gear including a ratchet drive; a second gear, the second gear comprising a ratchet structure; The ratchet drive portion is configured to engage with the ratchet structure of the second gear and drive the second gear to rotate in the first direction in response to the pressing of the depressible handle toward the housing, thereby causing the toothed rack to drive the first gear to rotate in the first direction.

6. The battery-free digital tire gauge according to claim 5, wherein: When the depressible handle is released, the spring force applied by the holding spring causes the depressible handle to retract to the nominal position, the toothed rack drives the first gear to rotate opposite to the first direction, and at the same time the ratchet driving portion slides opposite to the ratchet wheel of the ratchet structure of the second gear, thereby preventing the second gear from rotating in the opposite direction.

7. The battery-free digital tire gauge according to claim 6, wherein: The gear and ratchet assembly further includes a plurality of transmission gears operably coupled between the second gear and the converter, wherein a first transmission gear of the plurality of transmission gears engages with and is rotationally driven by the second gear, and wherein a last transmission gear of the plurality of transmission gears engages with and drives a shaft of the converter.

8. The battery-free digital tire gauge according to claim 6, wherein: The spring force includes a metal spring coupled to an end portion of the depressible handle.

9. The battery-free digital tire gauge according to claim 7, wherein: The plurality of transfer gears further include a first set of double gears and a second set of double gears coupled between the first transfer gear and the final transfer gear. 10 . The battery-free digital tire meter of claim 5 , further comprising a ripple filter including a second capacitor coupled to an output terminal of the LDO regulator and configured to reduce a ripple voltage input to the control processor. 11 . The battery-free digital tire meter of claim 5 , further comprising a noise filter comprising a third capacitor coupled to an output terminal of the LDO regulator and configured to reduce high frequency noise.

12. The battery-free digital tire gauge according to claim 11, wherein: The second capacitor has a capacitance at least 100 times greater than a capacitance of the third capacitor.

13. The battery-free digital tire gauge according to claim 2, wherein: The at least one sensor includes a pressure sensor, and wherein the housing includes a nozzle for communicating fluid pressure from the tire to the pressure sensor for measurement and display.

14. The battery-free digital tire gauge according to claim 2, wherein: The at least one sensor includes a tread depth sensor having an adjustable stem and a variable resistor in the housing for engaging a tire to measure and display tread depth.

15. The battery-free digital tire gauge according to claim 2, wherein: The at least one sensor includes a pressure sensor and a tread depth sensor.

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