Apparatus and method for determining web retractor spool position

Abstract

A web retractor may include a frame including spaced-apart side walls, a spool assembly rotatably mounted to and between the side walls, a guide disk rotatable with the spool assembly about a common axis of rotation, at least one magnet mounted to, or integral with, the guide disk so as to expose alternating magnetic poles of the at least one magnet, and a sensor assembly including a magnetic sensor fixed in position relative to the frame, the magnetic sensor configured to sense passage thereby of the exposed, alternating magnetic poles of the at least one magnet as the guide disk rotates about the common axis, and to produce sensor signals corresponding thereto.

Description

APPARATUS AND METHOD FOR DETERMINING WEB RETRACTOR SPOOL POSITIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 554,495, filed February 16, 2024, and to U.S. Provisional Patent Application No. 63 / 693,368, filed September 11 , 2024, the disclosures of which are both expressly incorporated herein by reference in their entireties.TECHNICAL FIELD

[0002] The present disclosure relates generally to web retractors, and more specifically apparatuses and methods for determining the position of a spool assembly including a spool upon which a web of a web retractor is wound.BACKGROUND

[0003] Web retractors may typically be implemented in occupant restraint systems of motor vehicles and other transportation vehicles. Conventional web retractors include a spool assembly including a spool upon which a web or belt is wound, and many are configured to take up web on the spool under the biasing force of the spring or spring assembly and to allow the web to be paid out of the retractor against the biasing force. Some web retractors include a locking feature which prevents the web from being paid out of the retractor under certain operating conditions of the vehicle in which the retractor is mounted. It may be desirable in some web retractor implementations to be able to determine the position of the spool and thus an amount or length of web paid out of and / or taken up on a web retractor.SUMMARY

[0004] The present disclosure may comprise one or more of the features recited in the attached claims, and / or one or more of the following features and combinations thereof. In a first aspect, a web retractor may comprise a frame including spaced-apart side walls, a spool assembly rotatably mounted to and between the side walls, a guide plate rotatable with the spool assembly about a common axis of rotation, the guide plate defining therein a spiral channel extendingabout the axis of rotation, a sensor assembly including a first sensor component fixed in position relative to the frame and a second sensor component, and a movable sensor arm having the second sensor component mounted thereto, the sensor arm including at least one projection configured to be received within the spiral groove such that rotation of the guide plate by the spool assembly causes the at least one projection to move along the spiral channel and thereby move the second sensor component relative to the first sensor component, wherein a relative position between the first and second sensor components corresponds to a rotational position of the spool assembly relative to a reference position.

[0005] A second aspect includes the features of the first aspect, and wherein the guide plate comprises a body with an opening defined centrally therethrough which is sized to receive a rotatable shaft of the spool assembly therein so as to mount the body to the shaft of the spool assembly, and wherein the common rotational axis passes centrally through the opening in the body of the guide plate and passes axially through the rotatable shaft of the spool assembly.

[0006] A third aspect includes the features of the second aspect, and wherein the body of the guide plate is mounted to the rotatable shaft along an outwardly- facing surface of one of the side walls of the frame, and wherein an outwardly-facing surface of the body of the guide pate defines the spiral groove therein and extending in a spiral pattern about the opening in the body of the guide plate.

[0007] A fourth aspect includes the features of any of the first through third aspects, and wherein the sensor arm comprises an elongated body rotatably mounted and an opposite end having the at least one projection extending therefrom, and wherein the second sensor component is fixed to the body of the sensor arm, and wherein rotation of the guide plate causes the at least one projection to move along the spiral channel, thereby causing the one end of the body to rotate such that the second sensor component mounted thereto moves relative to the first sensor component.

[0008] A fifth aspect includes the features of the fourth aspect, and wherein the first sensor component has a sensing surface, and wherein the relative position between the first and second sensor components corresponds to a relative position between the sensing surface of the first sensor component and the second sensor component.

[0009] A sixth aspect includes the features of the fifth aspect, and wherein the second sensor component is mounted along an edge of the body of the sensor arm facing the first sensor component, and wherein rotation of the body by the guide plate relative to the one of the side walls of the frame causes the edge of the body of the sensor arm and the second sensor component to move toward or away from the sensing face of the first sensor component.

[0010] A seventh aspect includes the features of any of the first through sixth aspects, and may further comprise a housing mounted to an outwardly-facing surface of one of the side walls of the frame, wherein the guide plate, the sensor arm and the sensor assembly are between the housing and the outwardly-facing surface of the one of the side walls of the frame.

[0011] An eighth aspect includes the features of the seventh aspect, and wherein the first sensor component is fixed to one of an inner surface of the housing and the outwardly-facing surface of the one of the side walls of the frame.

[0012] A ninth aspect includes the features of any of the first through eighth aspects, and wherein one end of the sensor arm is rotatably mounted to the outwardly-facing surface of the one of the side walls of the frame such that the one end of the body is rotatable relative to the one of the side walls, or is mounted to an inner surface of the housing such that the one end of the body is rotatable relative to the housing.

[0013] A tenth aspect includes the features of any of the first through ninth aspects, and wherein the sensor arm includes a plurality of projections, and wherein multiple, full rotations of the guide plate cause each of the plurality of projections to be sequentially received within the spiral channel.

[0014] An eleventh aspect includes the features of the tenth aspect, and wherein further multiple, full rotations of the guide plate cause at least some of the plurality of projections to sequentially exit the spiral channel.

[0015] A twelfth aspect includes the features of any of the first through eleventh aspects, and wherein rotation of the guide plate in one rotational direction causes the sensor arm to move in a direction in which the relative position between the first and second sensor components increases, and wherein rotation of the guide plate in a rotational direction opposite to the one rotational direction causes the sensor arm to move in a direction in which the relative position between the first and second sensor components decreases.

[0016]

[0017] A thirteenth aspect includes the features of any of the first through twelfth aspects, and wherein the first sensor component comprises a sensing component and the second sensor component comprises at least one component configured to be sensed by the sensing component.

[0018] A fourteenth aspect includes the features of the thirteenth aspect, and wherein the sensor assembly is a Hall effect sensor assembly in which the first sensor component is a Hall effect sensor and the second sensor component comprises at least one magnet.

[0019] In a fifteenth aspect, an apparatus for determining a rotational position of a spool assembly of a web retractor relative to a reference position of the spool assembly may comprise the web retractor of any of the first through fourteenth aspects, wherein the sensor assembly is configured to produce a sensor signal corresponding to the relative position between the first and second sensor components, and a signal processor configured to process the sensor signal to determine the rotational position of the spool assembly relative to the reference position.

[0020] A sixteenth aspect includes the features of the fifteenth aspect, and may further comprise a memory unit having the reference position of the spool assembly stored therein, wherein the signal processor is configured to retrieve the reference position from the memory unit, and to determine the rotational position of the spool assembly relative to the retrieved reference position.

[0021] In a seventh aspect, an apparatus for determining an amount or length of web paid out of a spool assembly of a web retractor may comprise the web retractor of any of the first through fourteenth aspects, wherein the web retractor includes a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, and wherein the sensor assembly is configured to produce a sensor signal corresponding to the relative position between the first and second sensor components, and a signal processor configured to process the sensor signal to determine a rotational position of the spool assembly relative to a reference position, and to correlate the determined rotational position of the spool assembly to the amount or length of the web paid out of the spool assembly.

[0022] An eighteenth aspect includes the features of the seventeenth aspect, and may further comprise a memory unit having the reference position of the spool assembly stored therein, wherein the signal processor is configured to retrieve the reference position from the memory unit, and to determine the rotational position of the spool assembly relative to the retrieved reference position.

[0023] In a nineteenth aspect, a web retractor may comprise a frame including spaced-apart side walls, a spool assembly rotatably mounted to and between the side walls, a guide disk rotatable with the spool assembly about a common axis of rotation, at least one magnet mounted to, or integral with, the guide disk so as to expose alternating magnetic poles of the at least one magnet, and a sensor assembly including a magnetic sensor fixed in position relative to the frame, the magnetic sensor configured to sense passage thereby of the exposed, alternating magnetic poles of the at least one magnet as the guide disk rotates about the common axis, and to produce sensor signals corresponding thereto.

[0024] A twentieth aspect includes the features of the nineteenth aspect, and wherein the at least one magnet includes a single magnet having a magnet face defining the alternating poles thereon, the single magnet mounted so as to rotate with the spool assembly about the common axis of rotation with the magnet face facing the sensor assembly.

[0025] A twenty first aspect includes the features of the twentieth aspect, and wherein the magnet face is diametrically magnetized so as to define a first magnetic pole on one portion of the magnet face and a second magnetic pole, opposite the first magnetic pole, on an opposition portion of the magnet face.

[0026] A twenty second aspect includes the features of the nineteenth aspect, and wherein the at least one magnet includes a plurality of magnets mounted to the guide disk about or adjacent to an outer periphery of the guide disk, the plurality of magnets mounted so as to expose alternating magnetic poles extending along or adjacent to the outer periphery of the guide disk, and wherein the magnetic sensor is configured to sense passage thereby of respective ones of the exposed magnetic poles of the plurality of magnets as the guide disk rotates about the common axis.

[0027] A twenty third aspect includes the features of the nineteenth aspect, and wherein the at least one magnet includes a plurality of magnets integral with the guide disk about or adjacent to an outer periphery of the guide disk, the plurality of magnets alternating in magnetic polarity so as to expose alternating magnetic polesextending along or adjacent to the outer periphery of the guide disk, and wherein the magnetic sensor is configured to sense passage thereby of respective ones of the exposed magnetic poles of the plurality of magnets as the guide disk rotates about the common axis.

[0028] A twenty fourth aspect includes the features of the twenty third aspect, and wherein the guide disk and the plurality of magnets are together of unitary construction.

[0029] A twenty fifth aspect includes the features of any of the nineteenth through twenty fourth aspects, and wherein the sensor assembly includes a housing configured to be mounted to the frame so as to fix the housing to the frame, the magnetic sensor mounted to the housing with the magnetic sensor positioned to face the at least one magnet.

[0030] A twenty sixth aspect includes the features of any of the nineteenth through twenty fifth aspects, and wherein the sensor assembly includes a sensor signal processing circuit configured to process the sensor signals produced by the magnetic sensor and produce processed sensor signals corresponding rotational direction and position of the spool assembly relative to a reference position.

[0031] A twenty seventh aspect includes the features of the twenty sixth aspect, and wherein the magnetic sensor includes a plurality of magnetic sensor elements.

[0032] A twenty eighth aspect includes the features of the twenty seventh aspect, and wherein the processed sensor signals include a pair of quadrature encoded signals from which the rotational direction and position of the spool assembly are determined.

[0033] A twenty ninth aspect includes the features of any of the nineteenth through twenty eighth aspects, and wherein the guide disk has a circular profile and includes a central portion through which the common axis of rotation passes, and wherein the central portion of the guide disk is configured to be mounted to the spool assembly.

[0034] A thirtieth aspect includes the features of the twenty ninth aspect, and wherein the spool assembly may comprise a shaft rotatably mounted to and between the side walls of the frame such that the shaft rotates relative to the side wall about the common axis of rotation, and a web spool mounted to the shaft so as to rotate with the shaft relative to the side walls of the frame, the web spool configured toattach to one end of a web so as to take up the web on the web spool, or pay out the web from the we spool, as the web spool rotates relative to the side walls of the frame.

[0035] A thirty first aspect includes the features of any of the nineteenth through thirtieth aspects, and may further comprise a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, a lock pawl normally biased to a locked position in which the lock pawl engages the spool assembly, wherein, upon complete wrapping of the web onto the spool, the web on the spool acts against the lock pawl and moves the lock pawl to an unlocked position, and a sensor arm having one end engaged with the lock pawl and an opposite end carrying a magnet, wherein the sensor assembly includes another magnetic sensor fixed in position relative to the frame, and wherein the lock pawl, in one of the locked and unlocked positions, positions the magnet carried by the sensor arm over the another magnetic sensor such that the another magnetic sensor senses the magnet carried by the sensor arm, and in the other of the locked and unlocked positions, the lock pawl positions the magnet carried by the sensor arm away from the another magnetic sensor such that the magnetic sensor does not sense the magnet carried by the sensor arm.

[0036] A thirty second aspect includes an apparatus for determining an amount or length of web paid out of a spool assembly of a web retractor, wherein the apparatus may comprise the web retractor of any of the twenty sixth through thirtieth aspects, and wherein the web retractor may include a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, and a signal processor configured to be responsive to the processed sensor signals to correlate the determined rotational direction and position of the spool assembly to the amount or length of the web paid out of, or taken up on, the spool assembly.

[0037] A thirty third aspect includes the features of the thirty second aspect, and may further comprise a lock pawl normally biased to a locked position in which the lock pawl engages the spool assembly, wherein, upon complete wrapping of the web onto the spool, the web on the spool acts against the lock pawl and moves the lock pawl to an unlocked position, and a sensor arm having one end engaged with the lock pawl and an opposite end carrying a magnet, wherein the sensor assemblyincludes another magnetic sensor fixed in position relative to the frame, and wherein the lock pawl, in one of the locked and unlocked positions, positions the magnet carried by the sensor arm over the another magnetic sensor such that the another magnetic sensor senses the magnet carried by the sensor arm, the lock pawl positions the magnet carried by the sensor arm away from the another magnetic sensor such that the magnetic sensor does not sense the magnet carried by the sensor arm, and wherein, after loss of electrical power is restored to the signal processor, the signal processor is configured to be responsive to a sensor signal produced by the another magnetic sensor to assign the reference position of the spool assembly to the position of the spool assembly at detection of the unlocked position of the lock pawl.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a top plan view of an embodiment of a web retractor including an embodiment of an apparatus for determining the position of the web spool assembly relative to a reference position.

[0039] FIG. 2 is a side elevational view of the web retractor of FIG. 1 with the housing shown in partial cutaway to illustrate components of the apparatus for determining the position of the web spool assembly, wherein the sensor arm is shown in a home position corresponding to a fully retracted web.

[0040] FIG. 3 is a side perspective view of an embodiment of the sensor arm of the apparatus for determining the web spool assembly position.

[0041] FIG. 4 is a magnified perspective view illustrating coupling of the sensor arm to the scroll plate for controlled position of the sensor arm by the scroll plate, wherein the sensor arm is shown in a position slightly advanced from the home position, with the second tooth poised to enter the scroll plate channel, corresponding to a small length of web paid out from the spool assembly.

[0042] FIG. 5A is a magnified perspective view similar to FIG. 4, wherein the sensor arm is shown in a fully advanced position corresponding to a maximum length of web paid out from the spool.

[0043] FIG. 5B is a cross-sectional view of the apparatus of FIGS. 1 -5A, as viewed along section lines 5B-5B, of FIG. 5A.

[0044] FIGS. 6A and 6B are assembly views of another embodiment of a web retractor including an embodiment of an apparatus for determining the position and rotational direction of the web spool assembly.

[0045] FIGS. 7A and 7B are assembled views of yet another embodiment of an apparatus for determining the position and rotational direction of a web spool assembly of a web retractor.

[0046] FIG. 8A is an assembled view of still another embodiment of an apparatus for determining the position and rotational direction of a web spool assembly of a web retractor.

[0047] FIG. 8B is a perspective view of the underside of the housing or cover component of the apparatus of FIG. 8A showing the sensor circuit assembly mounted thereto.

[0048] FIG. 8C is a perspective view of the sensor circuit assembly and guide disk of the apparatus of FIG. 8A.

[0049] FIG. 9A is a top perspective view of the shaft engaging side of the guide disk of the apparatus of FIGS. 7A-8C.

[0050] FIG. 9B is a perspective view of an alternate embodiment of the guide disk of the apparatus of FIGS. 7A-8C.

[0051] FIG. 10 is an example electrical schematic of an embodiment of the sensor circuit assembly of FIGS. 8A-8C.

[0052] FIG. 11 is an output waveform diagram illustrating an example output of the sensor circuit of FIGS. 7A-10 in response to passage thereby of alternating magnetic poles mounted to or integral with the guide disk.

[0053] FIG. 12A an assembled view of an embodiment of another apparatus, similar to that of FIGS. 8A-8C, in which the cover or housing is removed for clarity of illustration, and which shows a locked position of the lock pawl of the web retractor under conditions in which the web is not fully wound upon the spool.

[0054] FIG. 12B is an assembled view similar to FIG. 12A, showing an unlocked position of the lock pawl of the web retractor under conditions in which the web is fully wound upon the spool.

[0055] FIG. 13A is an assembled view similar to FIG. 12B illustrating some additional components for sensing and determining the position of the lock pawl, with the lock pawl positioned in the unlocked position depicted by example in FIG. 12B.

[0056] FIG. 13B is a cross-sectional view, as viewed along section lines 13B- 13B of FIG. 13A, illustrating operation and positioning of the lock pawl position sensor components when the lock pawl is in the unlocked position.

[0057] FIG. 14 is an assembled view similar to FIG. 13A illustrating operation and positioning of the lock pawl position sensor components when the lock pawl is in the locked position.DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0058] For the purposes of promoting an understanding of the principles of this disclosure, reference will now be made to a number of illustrative embodiments shown in the attached drawings and specific language will be used to describe the same.

[0059] This disclosure relates to devices, apparatuses, systems, and techniques for instantaneously determining the position of a web retractor spool relative to a reference position, from which the amount of length of web paid off from, i.e., extending out from, the spool at any point in time can then be directly and instantaneously determined. Referring now to FIGS. 1-5, an embodiment is shown of a web retractor 10 including an embodiment of a spool position sensing apparatus 30 for determining the position of a web spool assembly 14 of the retractor 10 relative to a reference web spool assembly position. The web retractor 10 may be any conventional web retractor including a rotatable spool assembly 14 about which a conventional flexible or semi-flexible web 16 is wound, wherein the web 16 is taken up on, i.e., wound onto and about, the spool assembly 14 as the spool assembly rotates in one direction (hereinafter a “web take up direction”), and wherein the web 16 is paid off from, i.e., wound off from, the spool assembly 14 as the spool assembly 14 rotates in a direction opposite the web take up direction (hereinafter a “web payout direction”). The web retractor 10 illustratively includes a conventional frame 12 having spaced-apart, upstanding side walls 12A, 12B each extending upwardly away from opposite sides of a bottom wall 12C of the frame 12, such that the walls 12A-12C together form a hard “C” or “U” shape. The bottom wall 12C and / or a side wall 12A, 12B of the frame 12 may, in some embodiments, be configured to mount to a structure, examples of which may include, but are not limited to, a mobile structure such as a motor vehicle, a trailer or the like, any stationary structure such as a wall, floor, pallet or other product transport device orassembly, a rail or frame member coupled to a motor vehicle, trailer or stationary structure, or the like. As depicted by example in the illustrated embodiment, the web 16 illustratively exits the frame 12 adjacent to a forward edge of the bottom wall 12C of the frame 12, although in alternate embodiments the web 16 may be coupled to the spool assembly 14 in a manner which causes the web 16 to exit the frame 12 adjacent to an opposite end or edge of the frame 12.

[0060] The rotatable spool assembly 14 illustratively includes a shaft 18 rotatably mounted to and between the side walls 12A, 12B such that one end 18A of the shaft 18 extends through the side wall 12A, and an opposite end of the shaft extends through the side wall 12B, and such that the shaft 18 rotates about a longitudinal axis, defined centrally through the shaft 18, relative to the side walls 12A, 12B of the frame 12. In some embodiments, a web spool 20 is mounted, i.e., secured, to the shaft 18 such that the web spool 20 rotates with the shaft 18, about the central, longitudinal axis of the shaft 18, relative to the side walls 12A, 12B of the frame 12. In such embodiments, the web spool 20 is conventional, and is configured to attach one end of the web 16 thereto in a conventional manner such that the web 16 is taken up on, and is paid off from, the spool 20 depending upon the rotational direction of the spool assembly 14. In the illustrated embodiment, the web retractor 10 includes a power spring assembly 22 which includes a housing mounted to an exterior (i.e., outwardly-facing surface) of the side wall 12B of the frame 12, and a conventional power spring carried within the housing. The power spring assembly 22 is conventional and includes at least one conventional biasing member, e.g., a coiled spring, configured to engage the respective end of the shaft 18, and / or a portion of the shaft 18 adjacent to the end thereof, and to bias the shaft 18 of the spool assembly 14 to rotate in the web take-up direction. To draw web 16 from the retractor 10 (without the spool assembly 14 rotationally locked or otherwise impeded as described below), sufficient force must be applied to the web 16 in the web payout direction, i.e., out of and away from the retractor 10, to overcome the biasing force of the biasing member of the power spring assembly 22 as is conventional.

[0061] In some embodiments, the web retractor 10 may include a spool locking mechanism configured to prevent the spool assembly 14 from rotating in the web payout direction under certain operating conditions. In some embodiments, for example, a conventional spool locking assembly may engage the shaft 18 at or adjacent to one of the ends thereof, and may act on the end, or adjacent to the endof the shaft 18 to prevent the shaft 18, and thus the spool assembly 14, from rotating in the web pay out direction under certain operating conditions. In other embodiments, such as illustrated by example in FIGS. 1-2 and 4-5, conventional toothed gears or wheels 24A, 24B may be mounted to the shaft 18 each adjacent to an inwardly-facing surface of a respective one of the side walls 12A, 12B of the frame 12, and a conventional lock pawl 25 is movably mounted to and between the side walls 12A, 12B of the frame and operable to engage between teeth of the toothed gears 12A, 12B under certain operating conditions to prevent the spool assembly 14 from rotating in the web pay out direction. In some such embodiments, only one of the toothed gears 24A, 24B may be included. In either case, some embodiments which include one or both of the toothed gears 24A, 24B may further include a ratchet handle rotatably mounted to the spool assembly 14 and movable relative to the side walls 12A, 12B of the frame 12, wherein such a ratchet handle may be operable in a conventional manner to be manually moved relative to the side walls 12A, 12B of the frame, while the locking mechanism prevents the spool assembly 14 from rotating in the web pay out direction, to engage between the teeth of the toothed gear(s) 12A and / or 12B, and rotate or “ratchet” the spool assembly 14 in the web take up direction so as to incrementally advance the web 16 onto the spool assembly 14 in a conventional manner. In some embodiments in which the web retractor 10 includes a locking mechanism, the web retractor 10 may be a conventional automatic locking retractor (ALR) or a conventional emergency locking retractor (ELR). In still other embodiments, the retractor 10 may not include any spool locking mechanism.

[0062] In the illustrated embodiment, the spool position sensing apparatus 30 includes a housing or cover 28 configured to be mounted to the external, i.e. , outwardly-facing side, of the side wall 12A of the frame 12, as depicted by example in FIGS. 1 and 2. In the illustrated embodiment, the spool position sensing apparatus 30 further includes a movable sensor arm 32 configured to operatively engage a guide plate 34, and a sensor assembly 36 configured to produce a sensor signal corresponding to the position of the sensor arm 32 relative to a reference position of the sensor arm 32. The sensor arm 32, the guide plate 34 and the sensor assembly 36 are all illustratively disposed between the housing 28 and the outwardly-facing surface of the side wall 12A of the frame 12 such that the housing 28 covers or carries all of the components 32, 34, 36. In some embodiments, thehousing 28 is sealed to, or relative to, the side wall 12A of the frame 12 so as to protect the components 32, 34, 36 from contaminants such as dirt and / or moisture.

[0063] The sensor assembly 36 illustratively includes two sensor components; one mounted so as to be fixed in position and the other mounted so as to be movable with the sensor arm 32, wherein the relative position between the two sensor components corresponds to a rotational position of the spool assembly 14 relative to a reference position. In the illustrated embodiment, the sensor assembly 36 is illustratively provided in the form of a conventional Hall effect sensor assembly including a conventional Hall effect sensor 38 as a sensing component and at least one magnet 42 as a sensed component, wherein the Hall effect sensor 38 operates in a conventional manner to produce an analog sensor signal on a signal line of a wiring harness 40, e.g., a voltage, having an amplitude that depends on the distance of the sensor 38 from the magnet 42, although in alternate embodiments the sensor signal produced by the Hall effect sensor 38 may be converted to a current and / or to a digital value for further processing. In the illustrated embodiment, the Hall effect sensor 38 is mounted to one side of the housing 28, and at least one magnet 42, e.g., one such magnet 42 shown in the FIGS. 1 and 2, is mounted to the sensor arm 32, and the reference position, which may be referred to herein as a “home position,” is illustrated in FIG. 2 in which the magnet 42 is positioned adjacent, i.e. , proximate, to the sensing surface 38A of the sensor 38. In alternate embodiments, the sensor 38 may be mounted to another stationary object such as the outwardly-facing surface of the side wall 12A of the frame 12. In other alternate embodiments, the magnet(s) 42 may be mounted to the housing 28 and / or to the side wall 12A of the frame 12, and the sensor 38 may be mounted to the sensor arm 32 such that the sensor 38 moves with the sensor arm 32. In still other alternate embodiments, the sensor assembly 36 may be provided in other conventional forms, examples of which may include, but are not limited to, a magnetoresistive sensor, one or more reed switches, a variable reluctance sensor, a capacitive proximity sensor, an inductive proximity sensor, a retroreflective sensor, e.g., a reflective photo sensor, or the like, and in any such alternate embodiments one component of the sensor assembly 36, which may be the sensing component or the sensed component, will be stationary and the other will move with, or be otherwise driven by, the sensor arm 32. In some such alternative embodiments, the sensed component may be or include one or more magnets as described above, or may be or include one or moreother non-magnetic structures, the presence of, or proximity to, which may be sensed or otherwise be detected by the sensing component in whatever form provided. In one particular example, the sensing component may include one or more embedded magnets, and the sensed component may be a structure, e.g., made of steel or other conventional material(s), which cause a change in the magnetic field produced by the one or more magnets as a function of a change in the relative distance between the sensing and sensed components. In any case, at least the signal output line of the wiring harness 40 is configured to be operatively connected to conventional signal processing circuit 44 configured to process the sensor signals produced by the sensor 38. In some embodiments, the signal processing circuit 44 may be provided in the form of a conventional microprocessor or microcontroller including, or electrically connected to a memory unit 46 having instructions stored therein which are executable by the microprocessor or controller to process the sensor signals produced by the sensor 38. The retractor 10, and the signal processing circuit 44 and associated memory unit 46, together form an apparatus or system for determining a rotational position of the spool assembly 14 of the web retractor 10 relative to a reference position of the spool assembly 14, and thus for determining an amount or length of the web 16 paid out of the spool assembly 14 of the web retractor 10.

[0064] The sensing arm 32 is illustratively provided in the form of an elongated body 50 having one end 50A configured to be movably, e.g., pivotably or rotationally, mounted to the outwardly-facing side wall 12A of the frame 12, and an opposite end 50B configured to engage the guide plate 34 such that rotation of the guide plate 34 drives movement of the sensor arm 32 relative to the sensor 38 as briefly described above. In the illustrated embodiment, the body 50 of the sensor arm 32 defines an opening 52 therethrough which is sized complementary to an opening 12D defined through the side wall 12A of the frame (see, e.g., FIG. 2), and the sensor arm 32 is illustratively mounted to the side wall 12A, with an inner surface 50C of the body 50 facing the outwardly-facing surface of the side wall 12A, via a conventional fixation element 35, e.g., a bolt, passed through the openings 52 and 12D and into engagement with the side wall 12A of the frame 12 such that the sensor arm 32 is pivotable, i.e., rotatable, about an axis of rotation defined centrally through the opening 52 and relative to the side wall 12A of the frame 12. By engagement of the sensor arm 32 with the guide plate 34, rotational movement of the guide plate 34 bythe shaft 18 of the retractor 10 causes the sensor arm 32 to pivot or rotate about the fixation element 35 toward and away from the sensor 38.

[0065] In the illustrated embodiment, a wall 54 extends about the opening 52, and the height or length of the wall 54 is sized to offset the inwardly-facing surface 50C of the body 50 of the sensor arm 32 sufficiently away from the outwardly-facing surface of the side wall 12A to provide for engagement of the sensor arm 32 with the guide plate 34 as will be described in detail below. In alternate embodiments, the sensor arm 32 may be movably mounted to an inwardly-facing surface of the housing 28, and in some such embodiments both components, e.g., 38 and 42, of the sensor assembly 36 may therefore be mounted to, and thus carried by, the housing 28. In any case, one elongated edge 50D of the body 50 of the sensor arm 32 generally faces the sensor 38, and a pocket 50E is formed along, and into, the edge 50D such that, when the sensor arm 32 is mounted as just described, the pocket 50E is positioned adjacent to, and is aligned with, the sensing surface 38A of the sensor 38 that is mounted (in a fixed position) to the housing 28 as described above. The pocket 50E is illustratively sized to receive the at least one magnet 42, and the at least one magnet 42 is mounted (i.e. , secured) to the body 50 of the sensor arm 32 within the pocket 50E to position the magnet(s) 42 on the sensor arm 32 so as to be aligned with the sensing surface 38A of the sensor 38 in the reference or “home” position of the sensor arm 32.

[0066] At or adjacent to the end 50B of the body 50 of the sensor arm 32, at least one protrusion 56 extends outwardly away from the inner surface 50C, i.e., the surface 50C of the body 50 of the sensor arm 32 that faces the side wall 12A of the frame 12 when the sensor arm 32 is mounted as described above. In the illustrated embodiment, eight such protrusions 56i - 56s are equally distributed across the surface 50C, i.e., such that the protrusions 56i - 56s are spaced equidistant from one another, at or adjacent to the end 50B of the body 50 of the sensor arm 32. In alternate embodiments, more or fewer protrusions 56 may be provided, although it will be understood that the number of protrusions 56, the width of the body 50 of the sensor arm 32 between the opposite edges 50D, 50F thereof along which the protrusion(s) 56 extend, and the length of the span across all such protrusions 56 relative to width of the body 50 along which the protrusion(s) 56 extend, will all have a bearing on the number of rotations of the spool assembly 14 (and fractions thereof) that can be measured with the sensing apparatus 30, as will become more apparentfrom the description below. In any case, in the illustrated embodiment the lengths of the protrusions 56i - 56s and the spacing therebetween are configured complementarily to the corresponding features of the guide plate 34 so as to facilitate guided movement of the sensor arm 32 by the guide plate 34 as will be described below.

[0067] Referring now particularly to FIGS. 2, 4 and 5, details of the guide plate 34 and of the guided movement of the sensor arm 32 by the guide plate 34 are depicted by example. In the illustrated embodiment, the guide plate 34 is provided in the form of a circular disk having a body 60 which defines an opening 60A centrally therethrough sized to receive therein at least a portion of the shaft 18 of the spool assembly 14, adjacent to the end 18A of the shaft 18, which extends outwardly away from the outwardly-facing surface of the side wall 12A of the frame 12. The opening 60A is illustratively fitted to the shaft 18 adjacent to the outwardly-facing surface of the side wall 12A of the frame 12 so as to mount the body 60 of the guide plate 34 to the shaft 18 such that the body 60 of the guide plate 34 rotates with the shaft 18 about a common axis of rotation relative to the side wall 12A with an external surface 60B of the body 60 of the guide plate 34 facing away from the outwardly-facing surface of the side wall 12A of the frame 12. A continuous wall 62 projects outwardly away from the surface 60B of the body 60 of the guide plate 34, and extends inwardly in a spiral shape from one end 62A adjacent to an outer edge of the body 60 to and toward an opposite end 62B near the central opening 60A defined through the body 60. The wall 62 illustratively defines a corresponding continuous, spiralshaped groove or channel 64 between adjacent ones of the wall 62 as the wall 62 spirals inwardly between the two ends 62A, 62B. In the illustrated embodiment, the channel 64 defines a first channel opening 64A between the end 62A of the wall 62 and the adjacent portion of the wall 62 in the spiral pattern, and defines a second channel opening 64B between the end 62B of the wall 62 and the adjacent portion of the wall 62 in the spiral pattern, as best shown in FIG. 4.

[0068] As also best shown in FIG. 4, the projections 56i - 56s, the spacing between the projections 56i - 56s, the spiral wall 62, and the spiral channel 64 are all sized such that only one projection 56i - 56s can be accommodated within any portion of the spiral channel 64 defined between adjacent portions of the wall 62. In the view depicted in FIG. 2, for example, in which the sensor arm 32 is in the home position as described above (i.e. , with the edge 50D of the body 50 of the sensorarm 32 positioned proximate to the sensor 38 such that the outer edge of the magnet(s) 42 is positioned adjacent or proximate to the sensing surface 38A of the sensor 38), only the projection 56i is disposed within a portion of the channel 64 defined beyond the opening 64A. In the illustrated embodiment, sufficient space is provided between the opening 64A of the channel 64 and the position of the projection 56i beyond the opening 64A when the sensor arm 32 is in the home position so as to prevent the projection 56i from becoming disengaged from the channel 64. In alternate embodiments, the projection 56i may be positioned at any desired location beyond the opening 64A when the sensor arm 32 is in the home position.

[0069] In any case, with the projection 56i positioned within the channel 64 and the sensor arm 32 in the home position, as depicted by example in FIG. 2, rotation of the body 60 of the guide plate 38 in the web payout direction, driven by the spool assembly 14 rotating in the web pay out direction (counterclockwise in FIGS. 2, 4 and 5), causes the next sequential projection 562 to enter the spiral channel 64 as the opening 64A of the spiral channel 64 sufficiently advances toward the projection 562, as illustrated by example in FIG. 4, thus causing the body 50 of the sensor arm 32 to rotate about the rotational axis of the opening 52 of the body 50 so as to draw the edge of the body 50 of the sensor arm 32 away the sensor 38 such that the outer edge of the magnet(s) 42 is drawn away from the sensing surface 38A of the sensor 38. Then, as the body 60 of the guide plate 38 continues to rotate in the web payout direction, the next projection 563 in the sequence of projections 56i - 568 enters the spiral channel 64 as the body 60 of the guide plate 38 completes another (360 degree) rotation, and so on, so as to further draw, i.e., pivot or rotate, the body 50 of the sensor arm 32, including the magnet(s) 42, away from the sensor 38. Then, as the body 60 of the guide plate 38 continues to rotate in the web payout direction, the first projection 56i eventually exits the opening 64B of the channel 64, and as the body 60 of the guide plate 38 further rotates in the web payout direction the next projection 562 in the sequence of projections 56i - 56s exits the spiral channel 64 via the opening 64B, and so on, until only the projection 56s remains in the spiral channel 64 at the maximum displacement of the sensor arm 32 from the sensor 38, as depicted by example in FIGS. 5A and 5B. In the view depicted in FIGS. 5A and 5B in which the sensor arm 32 is in the maximum displacement position, the body 50 of the sensor arm 32 has fully rotated about the rotational axisof the opening 52 so that the edge 50D of the body 50 of the sensor arm 32 positioned at a maximum distance from the sensor 38, and such that the outer edge of the magnet(s) 42 is positioned at a maximum distance from the sensing surface 38A of the sensor 38. In some embodiments, the maximum displacement position of the sensor arm 32 may be the reference position of the sensor arm 32. In any case, in the maximum displacement position of the sensor arm 32, sufficient space is provided between the opening 64B of the channel 64 and the position of the projection 56s within the channel 64 so as to prevent the projection 56s from becoming disengaged from the channel 64. The projection 56s may be positioned at any desired with the channel 64 relative to the opening 64B when the sensor arm 32 is in the maximum displacement position.

[0070] The sensor arm 32 is thus movable relative to the sensor 38, i.e., pivotable or rotatable about the rotational axis of the opening 52 defined through the body 50 of the sensor arm 32, in the web payout direction of the spool assembly 14 between the home position illustrated by example in FIG. 2 and the maximum displacement position illustrated by example in FIGS. 5A and 5B. In the illustrated embodiment, the home position of the sensor arm 32 corresponds to the web 16 being fully retracted within the retractor 10, i.e., such that the web 16 is fully taken up on the spool assembly 14, and the maximum displacement position of the sensor arm 32 corresponds to the web 16 being fully paid out of the spool assembly 14, i.e., a maximum amount or length of web that can be paid out of the spool assembly 14. In some alternate embodiments, the home position of the sensor arm 32 may correspond to some amount of web 16 paid out of the spool assembly 14 and / or the maximum displacement position of the sensor arm 32 may correspond to an amount of web 16 paid out of the spool assembly 14 that is less than the maximum amount or length of web 16 that can be paid out of the spool assembly 14. In any case, as the spool assembly 14 rotates in the opposite, web take up direction (clockwise in the examples depicted in FIGS. 2, 4 and 5A and 5B), the projections 56i - 56s advance back through the spiral channel 64 in the opposite direction from that just described until the sensor arm 32 reaches the home position.

[0071] In some alternate embodiments, the sensor arm 32 may be configured to move linearly or along an arc or other continuous shape relative to the side wall 12A or relative to the housing 28 such that relative movement between the sensed component and the sensing component of the sensor assembly 36 takes place alonga corresponding linear, arch-shaped or other continuous-shaped path. In some such embodiments, the sensed component may be carried by the sensor arm 32 and the sensing component may be fixed in position on the housing 28, on the side wall 12A of the frame 12 or to some other stationary structure disposed between the side wall 12A and the housing 28 and / or fixed to the side wall 12A and / or to the housing 28, and in other such embodiments the sensing component may be carried by the sensor arm 32 and the sensed component may be fixed in position on the housing 28, on the side wall 12A of the frame 12 or to some other stationary structure disposed between the side wall 12A and the housing 28 and / or fixed to the side wall 12A and / or to the housing 28. In any such embodiment in which the sensor arm 32 is configured to move linearly, along an arc or along some other continuous-shaped path relative to the side wall 12A or relative to the housing 28 such that relative movement between the sensed component and the sensing component of the sensor assembly 36 takes place along a corresponding linear, arch-shaped or other continuous-shaped path, the sensor assembly 36 may take any of the forms described by example above. As one non-limiting example, in embodiments in which the sensor assembly 36 is provided in the form of a Hall effect sensor 38 (or equivalent) and at least one magnet 42 as illustrated by example in the attached figures and described above, the opening 52 defined through the sensor body 50 may illustratively be provided in the form of a linear or arch-shaped slot or channel, and the sensor arm 32 may be configured to be mounted through the channel to the side wall 12A or to the housing 28 so as to be translatable along the linear or arcshaped channel as movement of the sensor arm 32 is driven by the guide plate 34 as described above.

[0072] In any case, between the home and the maximum displacement positions, the distance between the edge of the magnet(s) 42 along the edge 50D of the body 50 of the sensor arm 32 and the sensing face 38A of the sensor 38 corresponds to the number (and fractional number) of rotations of the spool assembly 14 from the home position (or from the maximum displacement position, and thus corresponds to the length of web 16 presently paid out from the spool assembly 14. With the home and / or the maximum displacement positions of the sensor arm 32 known (e.g., via appropriate calibration), the sensor signal produced by the sensor 38 thus corresponds at any instant in time to the rotational position of the spool assembly 14, in terms of degrees of rotation and / or number of rotations,including fractional rotations, relative to the home or maximum displacement position of the spool assembly 14, and the amount or length of web 16 presently paid out from the spool assembly 14 can, in turn, be instantaneously determined from the rotational position of the spool assembly 14. In this regard, the signal processing circuit 44 may be configured to process the sensor signals produced by the sensor 38 in a conventional manner to determine the rotational position of the spool assembly 14 and, in some embodiments, to correlate the determined rotational position of the spool assembly 14 to the amount or length of web 16 presently paid out of the spool assembly 14 in a conventional manner. In embodiments in which the signal processing circuit 44 is provided in the form of a conventional microprocessor or microcontroller, instructions may be stored in the memory 46 which are executable by the microprocessor or microcontroller to make such determinations.

[0073] It will be understood that in some alternate embodiments, the spool assembly 14 may illustratively be configured to rotate in the opposite direction than described above (i.e. , clockwise in the web pay out direction and counterclockwise in the web take up direction), and in such embodiments the guide plate 34 may be configured to form the spiraled channel 64 in the opposite direction so as to drive the sensor arm 32 between the home and maximum displacement positions as described above as the spool assembly rotates clockwise in the web pay out direction and counterclockwise in the web take up direction.

[0074] In embodiments in which the sensor 38 of the sensor assembly 36 is provided in the form of a Hall effect sensor, the wiring harness 40 includes a conventional input voltage line to supply electrical power to the sensor 38 for conventional operation thereof. In such embodiments, and in any embodiment in which the sensor 38 requires electrical power for operation thereof, loss of electrical power will not affect operation of the spool position sensing apparatus 30 because the position of the sensor arm 32, and thus the position of the magnet(s) 42 relative to the sensing surface 38A of the sensor 38, is controlled mechanically by the guide plate 34 as described above. Thus, with the home and / or maximum displacement positions known as also described above, the rotational position of the spool assembly 14 can be accurately and instantaneously determined once power is restored even if the rotational position of the spool assembly 14 has changed since the loss of electrical power.

[0075] Referring now to FIGS. 6A and 6B, another embodiment is shown of a web retractor 100 including an embodiment of a spool position and rotational direction sensing apparatus 130 for determining the position of a web spool assembly of the retractor 100 relative to a reference web spool assembly position and for determining a direction of rotation of the web spool assembly. The web retractor 100 may be any conventional web retractor, e.g., identical or similar to the web retractor 10 illustrated in FIG. 1 and described above or any other conventional retractor, and in any case may may include any one or combination of the various structures 12-25 associated with the web retractor 10 and described above. The web retractor 100, along with the processing circuit 44 and the memory unit 46 illustrated in FIG. 1 , may together form an apparatus or system for determining a rotational position of the spool assembly 14 relative to a reference position of the spool assembly 14 as well as a direction of rotation of the spool assembly 14, and thus for determining an amount or length of the web 16 paid out of the spool assembly 14. The web retractor 100 illustratively differs from the web retractor 10 illustrated and described with respect to FIGS. 1-5B in that the spool position sensing apparatus 30 of FIGS. 1 -5B is replaced with a spool position and rotational direction sensing apparatus 130 depicted by example in FIGS. 6A and 6B. The various structures 12- 25 associated with the web retractor 10, as well as the processing circuit 44 and the memory unit 46, or functional equivalents thereof, should thus be understood to be included with the retractor 100 and / or as part of an apparatus or system which includes the retractor 100, and some or all of these structures may accordingly be referred to and identified by the corresponding reference number illustrated in FIG. 1 in the following description of the structure and operation of the web retractor 100.

[0076] In the embodiment illustrated in FIGS. 6A and 6B, the spool position and rotational direction sensing apparatus 130 includes a magnet holder 132 configured to engage the end 18A of the shaft 18 extending outwardly away from the side wall 12A of the frame 12 such that the magnet holder 132 rotates with the shaft 18 about a longitudinal axis, defined centrally and axially through the shaft 18, relative to the side walls 12A, 12B of the frame 12. The magnet holder 132 may be formed of any non-ferrous material(s), examples of which include, but are not limited to, plastic, aluminum, copper, etc. In the illustrated embodiment, the end 18A of the shaft 18 defines an opening 102 centrally therethrough flanked by opposed linear projections 104A, 104B, and a respective end of the body 138 of the magnet holder132 defines a corresponding projection 134 extending centrally away from the body 138 through an opening flanked by opposed linear sides 136A, 136B. The magnet holder 132 is mounted to the end 18A of the shaft 18 by passing the projection 134 into the opening 102 with the sides 136A, 136B of the opening in the body 138 received against the respective linear projections 104A, 104B, such that the magnet holder 132 is secured to the end 18A of the shaft 18 so as to rotate with the shaft 18 about the rotational axis of the shaft 18. In some embodiments, the magnet holder 132 may be fixed, i.e., secured, to the end 18A of the spool shaft 18, e.g., via adhesive, and / or press-fit, and / or a non-ferrous fixation element (e.g., screw). In alternate embodiments, the opening 102 and the linear projections 104A, 104B may be defined not on and by the end 18A of the shaft 18, but rather on a separate structure that is mounted and secured to the end 18A of the shaft 18. In any case, it will be understood that the engagement structures of the end 18A of the shaft 18 and of the respective mounting end of the body 138 of the magnet holder 32 illustrated in FIGS. 6A and 6B and described herein are provided only by way of example, and that the end 18A of the shaft 18 (or any structure mounted thereto) and the mounting end of the magnet holder 132 may be alternatively configured in any conventional manner which provides for securement of the body 138 of the magnet holder 132 to the end 18A of the shaft 18 such that the magnet holder 132 rotates with the shaft 18 relative to the side walls 12A, 12B of the frame 12 of the retractor 100.

[0077] A magnet 140, e.g., in the form of a disk or cylinder, is provided and sized to be received within an opening 139 defined in an opposite end of the body 138 of the magnet holder 132, so as to mount the magnet 140 to the body 138 of the magnet holder 132 with one exposed face of the magnet 140 facing away, i.e., opposite, from the end 18A of the shaft 18. In this regard, the magnet holder 132 operates as a “guide disk” that is responsive to rotational drive by the shaft 18 to rotate the magnet 140 with the shaft 18 about the rotational axis of the shaft 18. As depicted by example in FIGS. 6A and 6B, the polarity of the exposed face of the magnet 140 is split along a central, bisecting line 142 between opposite poles 144, 146, i.e., such that the exposed face of the magnet 140 is diametrically magnetized, and so as to form a diametrically-magnetized cylinder magnet. In the illustrated example, the pole 144 is illustratively a “north” pole and the pole 146 is a “south” pole, although in alternate embodiments the polarities 144, 146 may be reversed. In other alternate embodiments, the magnet 140 may be configured such that theexposed face of the magnet 140 defines more than two poles, e.g., with sections of alternating poles extending radially about the exposed face of the magnet 140. In any case, the magnet 140 is illustratively mounted such that the exposed face is proud of the magnet holder 132 sufficiently to prevent, or at least reduce the likelihood, of interference by the spool shaft 18 with the magnetic field(s) produced by the magnet 140. In some embodiments, the magnet 140 is fixed to the magnet holder 132, e.g., via adhesive. In some embodiments, the magnet 140 may be integral with the magnet holder 132, i.e., so as to form a unitary structure. In any case, the disk-shaped magnet is illustratively circular in transverse cross-section, such that the two poles 144, 146 rotate about the rotational axis of the shaft 18 as the magnet housing 132 is rotationally driven by the shaft 18.

[0078] A sensor housing 150 has a body 154 with one side configured to be secured to the side wall 12A of the frame 12, and the body 154 defines an opening 156 centrally therethrough which is sized to receive the magnet holder 132 (and magnet 140) therein as the body 154 is mounted to the side wall 12A. The body 154 of the sensor housing 150 is illustratively formed of any non-ferrous material(s), examples of which include, but are not limited to, plastic, aluminum, copper, etc. A plurality of legs extend radially away from the body 154 of the sensor housing 150, and each leg is configured to be secured to the side wall 12A of the frame 12 with the magnet holder 132 and magnet 140 received within the opening 156. In the illustrated embodiment, three such legs 152A, 152B, 152C extend radially away from the body 154 and are spaced apart from one another so as to each engage the side wall 12A of the frame 12, although in alternate embodiments more or fewer such legs may be used. The legs may be secured to the side wall 12A of the frame 12 via adhesive and / or any conventional fixation element(s), e.g., screws. In any case, with the sensor housing 150 mounted to the side wall of the frame 12, the sensor housing 150 is fixed in position on and relative to the frame 12 such that the sensor housing 150 remains stationary as the magnet holder 132 and magnet 140 rotate about the axis of the shaft 18 within the opening 156 of the sensor housing 150.

[0079] An opposite side of the body 154 of the sensor housing 150 defines a circuit board mounting recess 158 which extends into the body 154 and intersects, and extends at least partially about, the opening 156. The recess 158 is illustratively sized to receive a circuit board 160 therein such that a circuit-mounting face of the circuit board 160 faces the opening 156, and thus faces the pole-defining face of themagnet 140 that is mounted to the magnet holder 132. The circuit board 156 may be secured to the sensor housing 150, within the recess 158, via adhesive, via one or more conventional fixation elements, or via a combination thereof. In any case, a magnetic sensor circuit 162 is mounted to the circuit-mounting face of the circuit board 160 so as to be positioned facing the pole-defining face of the magnet 140. As the magnet holder 132 is rotationally driven by the shaft 18 of the retractor 100, the pole-defining face of the magnet 140 rotates about the rotational axis of the shaft 18 and relative to the magnetic sensor circuit 162 which is fixed in position, by the sensor housing 150, relative to the frame 12. The magnetic sensor circuit 162 includes a plurality of sensor elements responsive to rotation of the pole-defining face of the magnet 140 to produce sensor signals from which a position of the shaft 18, relative to a reference position, can be determined, and from which a rotational direction of the shaft 18 can be determined. In some embodiments, the magnetic sensor circuit 162 may be a 64 element circular sensor array, although in other embodiments the magnetic sensor circuit 162 may take other conventional forms.

[0080] In some embodiments, an example of which is depicted in FIG. 11 , the magnetic sensor circuit 162 may be configured to produce two quadrature encoded output signals from which the position and rotational direction of the shaft 18 can be determined in a conventional manner. From such signals, the processing circuit 44 (see FIG. 1 ) is configured, in a conventional manner, to determine the position and rotational direction of the shaft 18, and thus instantaneously determine an amount or length of the web 16 that is paid out of the spool assembly 14.

[0081] Referring now to FIGS. 7A and 7B, another embodiment is shown of a web retractor 200 including an embodiment of a spool position and rotational direction sensing apparatus 230 for determining the position of a web spool assembly of the retractor 200 relative to a reference web spool assembly position and for determining a direction of rotation of the web spool assembly. The web retractor 200 may be any conventional web retractor, e.g., and may be identical or similar to the web retractor 10 illustrated in FIG. 1 and described above, and may therefore include one or any combination of the various structures 12-25 associated with the web retractor 10. The web retractor 200, along with the processing circuit 44 and the memory unit 46 illustrated in FIG. 1 , may together form an apparatus or system for determining a rotational position of the spool assembly 14 relative to a reference position of the spool assembly 14 as well as a direction of rotation of thespool assembly 14, and thus for determining an amount or length of the web 16 paid out of the spool assembly 14. The web retractor 200 illustratively differs from the web retractor 10 illustrated and described with respect to FIGS. 1 -5B in that the spool position sensing apparatus 30 is replaced with a spool position and rotational direction sensing apparatus 230 depicted by example in FIGS. 7A and 7B. The various structures 12-25 associated with the web retractor 10, as well as the processing circuit 44 and the memory unit 46, or functional equivalents thereof, should thus be understood to be included with the retractor 200 and / or as part of an apparatus or system which includes the retractor 200, and some or all of these structures may accordingly be referred to and identified by the corresponding reference number illustrated in FIG. 1 in the following description of the structure and operation of the web retractor 200.

[0082] The spool position and rotational direction sensing apparatus 230 depicted by example in FIGS. 7A and 7B differs from the spool position and rotational direction sensing apparatus 130 depicted in FIGS. 6A and 6B in that the guide disk is provided in the form of a disk-shaped gear or wheel 232, a plurality of end-to-end magnetized cylinder magnets 240A, 240B are mounted to and along the edge of the gear or wheel 232 so as to define alternating poles along the edge of the gear or wheel 232. As illustrated by example in FIG. 8B, the poles of the magnets 240A are illustratively “north,” and the poles of the magnets 240B are illustratively “south,” and the magnets 240 are arranged so that the poles alternate along the edge of the guide disk 232.

[0083] A sensor circuit 234 includes a circuit board 236 to which a magnetic sensor circuit 238 is mounted in a fixed position adjacent to the edge of the gear or wheel 232. A cover or housing will typically be mounted to the side wall 12A of the frame 12, and the sensor circuit 234 may be mounted to such a cover or housing to fix the sensor circuit 234 in position relative to the gear or wheel 232. One example of such a cover or housing is illustrated by example in FIGS. 8A-8C. In other embodiments, the sensor circuit 234 may be mounted to the side wall 12A so as to be fixed in position on the side wall 12A relative to the gear or wheel 232. In any case, as the guide disk, in the form of the gear or wheel 232, rotates in response to rotational drive applied by the shaft 18, the alternating-pole magnets 240A, 240B mounted to the edge of the gear or wheel 232, e.g., on or in and about the outer periphery of the gear or wheel 232, pass by the magnetic sensor 238 of the magneticsensor circuit 234. The magnetic sensor 238 is responsive to passage thereby of the alternating-pole magnets 240A, 240B resulting from rotation of the gear or wheel 232 by the shaft 18 of the retractor 200 to produce sensor signals from which a position of the shaft 18, relative to a reference position, can be determined, and from which a rotational direction of the shaft 18 can be determined.

[0084] Referring now to FIGS. 8A-8C, another variant 300 of the web retractor 200 of FIGS. 8A and 8B is shown. In this variant, an example of the housing or cover 328 described above with respect to FIGS. 7A and 7B is shown in partial breakaway and is mounted to the side wall 12A of the frame 12 so as to be fixed to the frame 12. Another embodiment of a sensor circuit 336 is mounted to the housing or cover 328 so as to be fixed to the housing or cover 328, and the housing or cover 328 is further configured to extend over a guide disk 334 identical or similar to the guide disk 232 described above, such that the guide disk 334 rotates within and relative to the housing or cover 328 adjacent and proximate to the sensor circuit 336.Alternatively or additionally, the sensor circuit 336 may be mounted to, i.e. , fixed to, one or more components of the frame 12, e.g., to the side wall 12A of the frame 12.

[0085] The housing or cover 328 has a body 350 which defines a connector port 352, sized and configured to receive therein a connector 362 of the sensor circuit 336, which leads to a recessed sensor circuit mounting section or mounting port 354 sized and configured to mount the circuit board 360 of the sensor circuit 336 thereto via at least one conventional fixation element F, e.g., two conventional headed screws illustrated by example in FIGS. 8A-8C. The sensor circuit mounting section 354 illustratively opens to a circular well 356 sized and configured to receive the guide disk 334 therein and to allow the guide disk 334 to rotate therein unobstructed.

[0086] The guide disk 334, like the guide disk 232 illustrated in FIGS. 7A and 7B, has a disk-shaped body 370, e.g., circular in cross-section, with magnets of alternating polarity illustratively extending into and along the circular outer periphery 372 of the disk-shaped body 370. As illustrated by example in FIG. 8C, disk or cylinder-shaped magnets of alternating polarity 374 (e.g., South or “S”) and 376 (e.g., North or “N”) extend into and along the outer periphery 372. An exterior face 375A of the body 370 of the guide disk 334 extends into the circular well 356 of the housing or cover 328 and faces the disk-shaped interior surface 357 of the circular well 356. A mounting face 375B of the body 370 of the guide disk 334 defines acentral mounting section 378, see FIG. 9A, via which the body 370 of the guide disk 334 is mounted to the shaft 18 and / or web spool 20 such that the body 370 of the guide disk 334 rotates with the shaft 14 and / or web spool 20 relative to the side walls 12A, 12B of the frame 12. The body 370 of the guide disk 334, like the body of the guide disk 232 illustrated in FIGS. 7A and 7B, is illustratively formed of any nonferrous material(s), examples of which include, but are not limited to, plastic, aluminum, copper, etc.

[0087] In some alternate embodiments, the magnets 374, 376 may have different shapes, i.e., other than disk or cylinder-shaped, and / or may be affixed, e.g., with fasteners and / or adhesive, on and along the outer periphery 372 and / or to either face 375A, 375B of the disk-shaped body 370 adjacent to and about the outer periphery 372. In still other embodiments, the magnets 374, 376 may be formed integral with the guide disk 334 so as to form a unitary magnetic structure 334’ as depicted by example in FIG. 9B in which the magnetic disk 334’ defines alternating sections of magnetic poles 374’, 376’ extending radially about the disk 334’.

[0088] The sensor circuit 336 illustratively includes an electrical connector 362 mounted to the circuit board 360 and configured to electrically connect to and with a complementarily configured electrical connector 341 that is electrically connected to the wiring harness 40 so as to be electrically connectable to the signal processing circuit 44 (see FIG. 1 ). The electrical connector 362 is electrically connected, e.g., via conductive traces, to a magnetic sensor circuit 364 also mounted to the circuit board 336. The magnetic sensor circuit 364 is thus fixed to the circuit board 360 which is, in turn, affixed to the housing or cover 328 as depicted in FIG. 8B. The sensor circuit mounting section or port 354 and the circular well 356 of the housing or cover 328 are together configured such that the guide disk 334, rotationally driven by the shaft 14 of the retractor 300, rotates within the circular well 356 with the outer periphery 372 of the body 370 rotating adjacent and proximate to the magnetic sensor circuit 364 as depicted by example in FIGS. 8B and 8C, such that the magnetic sensor circuit 364 can detect passage thereby of the magnets 374, 376 and such that the signal processing circuit 44 can determine a speed and rotational position (relative to a reference rotational position) of the guide disk 334 as it rotates with the shaft 18 of the retractor 300. Accordingly, and as described above, the signal processing circuit 44 may be programmed, e.g., via instructions stored in the memory 46, to use such guide disk rotational speed and position to determine at anytime, i.e., instantaneously, an amount of web 16 that is presently drawn from, and / or that remains wrapped about the spool 20, whether web 16 is presently being drawn from or wrapped onto the spool 20, and the speed of any such movement of the web 16.

[0089] Referring now to FIG. 10, an example electrical schematic is shown of the sensor circuit 336 of FIGS. 8A-8C which includes the electrical connector 362 and the magnetic sensor circuit 364. In the illustrated embodiment, the electrical connector 262 is illustratively provided in the form of a conventional 4-pin electrical connector (e.g., VDD, GND, and two signal outputs of the sensor circuit 364) having a part identification number 53261 -0471 which is commercially available from Molex® Inc. of Lisle, IL, although in alternate embodiments other conventional electrical connectors, e.g., with 4 pins, with fewer pins, or with more pins, may alternative be used. Also in the illustrated embodiment, the magnetic sensor circuit 364 is illustratively provided in the form of a conventional Hall effect sensor having a part identification number MLX9235 which is commercially available from Melexis® Inc. of Novi, Ml, although in alternate embodiments other conventional magnetic sensor circuits may alternatively be used. As briefly described above, the magnetic sensor circuit 238, 364 illustratively has quadrature-encoded outputs OUT1 , OUT2 which illustratively produce out-of-phase outputs of the type illustrated by example in FIG. 11 in response to passage thereby of alternating poles “N” and “S” of the magnets 240A, 240B and 374, 376. Spool rotational direction and spool position can be determined based on sequencing of the signal edges, in a conventional manner, as also depicted in FIG. 11 . It will be understood, however, that in some embodiments other conventional magnetic sensor circuits may alternatively be used.

[0090] Referring now to FIGS. 12A-14, a variant 400 of the web retractor is shown which includes the ability to reset the reference position, e.g., the “home” position of the spool 20 and the web 16 in the event of loss of electrical power. In the embodiment illustrated in FIGS. 12A-14, the web retractor 400 is identical in many respects to the web retractor 300 illustrated in FIGS. 8A-9B, and like numbers are therefore used in FIGS. 12A-14 to identify like components. In the embodiment illustrated in FIGS. 12A-14, for example, the guide disk 334 is illustratively identical to that used in the web retractor 300, although the guide disk 334 may alternatively be modified or implemented according to any one or more of the alternate embodiments described above with respect to FIGS. 8A-9B. The sensor circuit 336’illustratively includes an additional magnetic sensor circuit 402 mounted to the circuit board 360’, and the electrical connector 362’ accordingly includes at least one extra electrical pin to provide for supply of the sensor signal produced by the additional magnetic sensor circuit 402 to the signal processing circuit 44. The embodiment 400 illustrated in FIGS. 12A-14 further illustratively includes a sensor arm 404 operatively coupled to the lock pawl 25 briefly described above with reference to the embodiment 10 illustrated in FIGS. 1-5B. The housing or cover 334 (not shown in FIGS. 12A-14) is modified to accommodate the sensor arm 404, but is otherwise identical in structure and function to the housing or cover 334 illustrated in FIGS. 8A- 8C and described above. The sensor arm 404 illustratively carries a magnet which is detectable by the additional magnetic sensor 402 depending upon the position of the lock pawl 25, as will be described in detail below. In the event of loss of electrical power, the web 16 is manually controlled, in a conventional manner, to fully retract within the retractor 400 to reset the reference position, e.g., the “home” position of the spool 20 and the web 16, as will also be described in detail below.

[0091] Referring now specifically to FIGS. 12A and 12B, the sensor arm 404 is omitted in these figures so as to demonstrate and describe the conventional operation of the lock pawl 25 in the web retractor 400. As illustrated in both of FIGS. 12A and 12B, the portion of the lock pawl 25 extending outwardly through the opening 12E in the side wall 12A is attached to a one end of a biasing member 27, e.g., a spring, the opposite end of which extends through another opening 12F in the side wall 12A so as to fix the respective end of the biasing member 27 to the side wall 12A. The biasing member 27 is configured to bias the lock pawl 25 toward the shaft 18 and spool 20. With a sufficient amount, i.e., length, of the web 16 drawn from the spool 20, the force of the biasing member 27 acting on the lock pawl 25 will force the lock pawl 25 into a locked position, depicted by example in FIG. 12A, in which the lock pawl 25 engages the toothed gears or wheels 24A, 24B mounted to the spool on either side of the web 16 (see FIGS. 1 , 4 and 5A).

[0092] As the shaft 18 and spool 20 are thereafter rotated together in the web take-up direction, the web 16 previously drawn from the spool 20 will then be taken up on the spool 20. As the spool 20 continues to rotate in the web take-up direction, the thickness of the layers of web 16 wrapped on the spool 20 will build and the total thickness of the web 16 on the spool 20 will eventually become sufficient to bear against the lock pawl 25 and force the lock pawl 25 away from the locked positionagainst the toothed gears or wheels 24A, 24B and into an unlocked position as depicted by example in FIG. 12B. Generally, the total thickness of the web 16 on the spool 20 will force the lock pawl 25 to rotate from the locked to the unlocked position as, or when, the spool 20 reaches the “home” position in which the web 16 is fully retracted within the retractor 400, i.e., such that the web 16 is fully taken up on the spool assembly 20, as described above with respect to FIGS. 1-5B. As the shaft 18 and spool 20 are thereafter rotated together in the web pay-out direction, the biasing force of the biasing member 27 acting on the lock pawl 25 will force the lock pawl 25 to rotate to the lock position illustrated in FIG. 12A when a sufficient length of web 16 has been drawn from the spool 20 so as to allow the lock pawl 25 to rotate back to the locked position. This feature of the lock pawl 25 exploited in the system 400 to determine when the spool assembly 14, and thus the spool 20 and the web 16, is in the home position so as to allow for a reset of the reference or “home” position of the spool 20 and the web 16.

[0093] As illustrated in FIGS. 13A, 13B and 14, the sensor arm 404 has a sensor body 406 including a lock pawl engaging end 408 and a sensing end 410 extending away from the lock pawl engaging end 408. As depicted by example in FIG. 13B, the lock pawl engaging end 408 of the sensor arm 404 defines an opening 416 sized and configured to receive therein and engage an end portion 25A of the lock pawl 25 which extends outwardly away from the side wall 12A of the frame 12, such that the sensor arm 404 moves, i.e., rotates, with the lock pawl 25 as the lock pawl 25 rotates between the lock and unlocked positions. As also depicted by example in FIG. 13B, the sensing end 410 of the sensor arm defines another opening 412 sized and configured to receive therein a magnet 414, e.g., in the form of a disk-shaped or cylindrical magnet. The sensor arm 404 is illustratively sized and configured such that when the lock pawl 25 is in the unlocked position as illustrated by example in FIG. 12B, the sensing end 410 of the sensor arm 408 is positioned by the lock pawl 25 over the magnetic sensor circuit 402 so as to detect the presence of the magnet 414 carried by the sensor arm 404 as depicted by example in FIGS. 13A and 13B. When the lock pawl 25 rotates from the unlocked to the locked position, as illustrated by example in FIG. 12A, the sensing end 410 of the sensor arm 404 rotates downwardly away from the magnetic sensor circuit 414 so as to detect an absence of the magnet 414 carried by the sensor arm 404.

[0094] Upon loss of electrical power to the web retractor 400, the “home” position can be reset after electrical power is restored by manually controlling the web 16 to be fully retracted within the web retractor 400, i.e., to be fully wound upon the spool 20 so as to force the lock pawl 25 to the unlocked position. As described above, the web 16 wrapped on the spool 20 forces the lock pawl 25 from the locked to the unlocked position as the spool 20 (and web 16) reaches the “home” position, at which point the signal produced by the additional sensor circuit 402 will change state and thereby inform the signal processing circuit 44 of that the spool 20 is in the home position. Unless and until electrical power is again lost, this home position will illustratively be used by the signal processing circuit as the “home” or reference position.

[0095] It will be understood that whereas the web retractor 400 is illustrated and described as detecting an unlocked lock pawl 25 when the sensor arm 404 positions the magnet 414 over the magnetic sensing circuit 402, and as detecting a locked lock pawl 25 when the sensor arm 404 positions the magnet away from the magnetic sensing circuit 402, the sensor arm 404 may alternatively be designed so as to position the magnet 414 in the sensor arm 404 over the magnetic sensing circuit 402 when the lock pawl 25 is locked and to position the magnet 414 in the sensor arm 404 away from the magnetic sensing circuit 502 when the lock pawl 25 is unlocked.

[0096] While this disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of this disclosure are desired to be protected. For example, whereas the embodiments illustrated in FIGS. 8A-8C, FIG. 10, and FIGS. 12A-14 illustrate the use of electrical connectors for electrically connecting the circuitry onboard the sensor circuits 336, 336’ to the signal processing circuit 44, it will be understood that in alternate embodiments such electrical connectors may be omitted, and the sensor circuit 336 and / or 336’ may be hard-wired directly to the signal processing circuit 44.

Claims

What is claimed is:1 . A web retractor, comprising: a frame including spaced-apart side walls, a spool assembly rotatably mounted to and between the side walls, a guide plate rotatable with the spool assembly about a common axis of rotation, the guide plate defining therein a spiral channel extending about the axis of rotation, a sensor assembly including a first sensor component fixed in position relative to the frame and a second sensor component, and a movable sensor arm having the second sensor component mounted thereto, the sensor arm including at least one projection configured to be received within the spiral groove such that rotation of the guide plate by the spool assembly causes the at least one projection to move along the spiral channel and thereby move the second sensor component relative to the first sensor component, wherein a relative position between the first and second sensor components corresponds to a rotational position of the spool assembly relative to a reference position.2 The web retractor of claim 1 , wherein the guide plate comprises a body with an opening defined centrally therethrough which is sized to receive a rotatable shaft of the spool assembly therein so as to mount the body to the shaft of the spool assembly, and wherein the common rotational axis passes centrally through the opening in the body of the guide plate and passes axially through the rotatable shaft of the spool assembly.

3. The web retractor of claim 2, wherein the body of the guide plate is mounted to the rotatable shaft along an outwardly-facing surface of one of the side walls of the frame, and wherein an outwardly-facing surface of the body of the guide pate defines the spiral groove therein and extending in a spiral pattern about the opening in the body of the guide plate.

4. The web retractor of any of claims 1 through 3, wherein the sensor arm comprises an elongated body rotatably mounted and an opposite end having the at least one projection extending therefrom, and wherein the second sensor component is fixed to the body of the sensor arm, and wherein rotation of the guide plate causes the at least one projection to move along the spiral channel, thereby causing the one end of the body to rotate such that the second sensor component mounted thereto moves relative to the first sensor component.

5. The web retractor of claim 4, wherein the first sensor component has a sensing surface, and wherein the relative position between the first and second sensor components corresponds to a relative position between the sensing surface of the first sensor component and the second sensor component.

6. The web retractor of claim 5, wherein the second sensor component is mounted along an edge of the body of the sensor arm facing the first sensor component, and wherein rotation of the body by the guide plate relative to the one of the side walls of the frame causes the edge of the body of the sensor arm and the second sensor component to move toward or away from the sensing face of the first sensor component.

7. The web retractor of any of claims 1 through 6, further comprising a housing mounted to an outwardly-facing surface of one of the side walls of the frame, wherein the guide plate, the sensor arm and the sensor assembly are between the housing and the outwardly-facing surface of the one of the side walls of the frame.

8. The web retractor of claim 7, wherein the first sensor component is fixed to one of an inner surface of the housing and the outwardly-facing surface of the one of the side walls of the frame.

9. The web retractor of any of claims 1 through 8, wherein one end of the sensor arm is rotatably mounted to the outwardly-facing surface of the one of the side walls of the frame such that the one end of the body is rotatable relative to the one of the side walls, or is mounted to an inner surface of the housing such that the one end of the body is rotatable relative to the housing.

10. The web retractor of any of claims 1 through 9, wherein the sensor arm includes a plurality of projections, and wherein multiple, full rotations of the guide plate cause each of the plurality of projections to be sequentially received within the spiral channel.11 . The web retractor of claim 10, wherein further multiple, full rotations of the guide plate cause at least some of the plurality of projections to sequentially exit the spiral channel.

12. The web retractor of any of claims 1 through 11 , wherein rotation of the guide plate in one rotational direction causes the sensor arm to move in a direction in which the relative position between the first and second sensor components increases, and wherein rotation of the guide plate in a rotational direction opposite to the one rotational direction causes the sensor arm to move in a direction in which the relative position between the first and second sensor components decreases.

13. The web retractor of any of claims 1 through 12, wherein the first sensor component comprises a sensing component and the second sensor component comprises at least one component configured to be sensed by the sensing component.

14. The web retractor of claim 13, wherein the sensor assembly is a Hall effect sensor assembly in which the first sensor component is a Hall effect sensor and the second sensor component comprises at least one magnet.

15. An apparatus for determining a rotational position of a spool assembly of a web retractor relative to a reference position of the spool assembly, the apparatus comprising: the web retractor of any of claims 1 through 14, wherein the sensor assembly is configured to produce a sensor signal corresponding to the relative position between the first and second sensor components, and a signal processor configured to process the sensor signal to determine the rotational position of the spool assembly relative to the reference position.

16. The apparatus of claim 15, further comprising a memory unit having the reference position of the spool assembly stored therein, wherein the signal processor is configured to retrieve the reference position from the memory unit, and to determine the rotational position of the spool assembly relative to the retrieved reference position.

17. An apparatus for determining an amount or length of web paid out of a spool assembly of a web retractor, the apparatus comprising: the web retractor of any of claims 1 through 14, wherein the web retractor includes a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, and wherein the sensor assembly is configured to produce a sensor signal corresponding to the relative position between the first and second sensor components, and a signal processor configured to process the sensor signal to determine a rotational position of the spool assembly relative to a reference position, and to correlate the determined rotational position of the spool assembly to the amount or length of the web paid out of the spool assembly.

18. The apparatus of claim 17, further comprising a memory unit having the reference position of the spool assembly stored therein, wherein the signal processor is configured to retrieve the reference position from the memory unit, and to determine the rotational position of the spool assembly relative to the retrieved reference position.

19. A web retractor, comprising: a frame including spaced-apart side walls, a spool assembly rotatably mounted to and between the side walls, a guide disk rotatable with the spool assembly about a common axis of rotation, at least one magnet mounted to, or integral with, the guide disk so as to expose alternating magnetic poles of the at least one magnet, and a sensor assembly including a magnetic sensor fixed in position relative to the frame, the magnetic sensor configured to sense passage thereby of the exposed, alternating magnetic poles of the at least one magnet as the guide disk rotates about the common axis, and to produce sensor signals corresponding thereto.

20. The web retractor of claim 19, wherein the at least one magnet includes a single magnet having a magnet face defining the alternating poles thereon, the single magnet mounted so as to rotate with the spool assembly about the common axis of rotation with the magnet face facing the sensor assembly.21 . The web retractor of claim 20, wherein the magnet face is diametrically magnetized so as to define a first magnetic pole on one portion of the magnet face and a second magnetic pole, opposite the first magnetic pole, on an opposition portion of the magnet face.

22. The web retractor of claim 19, wherein the at least one magnet includes a plurality of magnets mounted to the guide disk about or adjacent to an outer periphery of the guide disk, the plurality of magnets mounted so as to expose alternating magnetic poles extending along or adjacent to the outer periphery of the guide disk, and wherein the magnetic sensor is configured to sense passage thereby of respective ones of the exposed magnetic poles of the plurality of magnets as the guide disk rotates about the common axis.

23. The web retractor of claim 19, wherein the at least one magnet includes a plurality of magnets integral with the guide disk about or adjacent to an outer periphery of the guide disk, the plurality of magnets alternating in magneticpolarity so as to expose alternating magnetic poles extending along or adjacent to the outer periphery of the guide disk, and wherein the magnetic sensor is configured to sense passage thereby of respective ones of the exposed magnetic poles of the plurality of magnets as the guide disk rotates about the common axis.

24. The web retractor of claim 23, wherein the guide disk and the plurality of magnets are together of unitary construction.

25. The web retractor of any of claims 19 through 24, wherein the sensor assembly includes a housing configured to be mounted to the frame so as to fix the housing to the frame, the magnetic sensor mounted to the housing with the magnetic sensor positioned to face the at least one magnet.

26. The web retractor of any of claims 19 through 25, wherein the sensor assembly includes a sensor signal processing circuit configured to process the sensor signals produced by the magnetic sensor and produce processed sensor signals corresponding rotational direction and position of the spool assembly relative to a reference position.

27. The web retractor of claim 26, wherein the magnetic sensor includes a plurality of magnetic sensor elements28. The web retractor of claim 27, wherein the processed sensor signals include a pair of quadrature encoded signals from which the rotational direction and position of the spool assembly are determined.

29. The web retractor of any of claims 19 through 28, wherein the guide disk has a circular profile and includes a central portion through which the common axis of rotation passes, and wherein the central portion of the guide disk is configured to be mounted to the spool assembly.

30. The web retractor of claim 29, wherein the spool assembly comprises: a shaft rotatably mounted to and between the side walls of the frame such that the shaft rotates relative to the side wall about the common axis of rotation, and a web spool mounted to the shaft so as to rotate with the shaft relative to the side walls of the frame, the web spool configured to attach to one end of a web so as to take up the web on the web spool, or pay out the web from the we spool, as the web spool rotates relative to the side walls of the frame.31 . The web retractor of any of claims 19 through 30, further comprising: a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, a lock pawl normally biased to a locked position in which the lock pawl engages the spool assembly, wherein, upon complete wrapping of the web onto the spool, the web on the spool acts against the lock pawl and moves the lock pawl to an unlocked position, and a sensor arm having one end engaged with the lock pawl and an opposite end carrying a magnet, wherein the sensor assembly includes another magnetic sensor fixed in position relative to the frame, and wherein the lock pawl, in one of the locked and unlocked positions, positions the magnet carried by the sensor arm over the another magnetic sensor such that the another magnetic sensor senses the magnet carried by the sensor arm, and in the other of the locked and unlocked positions, the lock pawl positions the magnet carried by the sensor arm away from the another magnetic sensor such that the magnetic sensor does not sense the magnet carried by the sensor arm.

32. An apparatus for determining an amount or length of web paid out of a spool assembly of a web retractor, the apparatus comprising: the web retractor of any of claims 26 through 30, wherein the web retractor includes a web mounted to a spool of the spool assembly, the spool assembly rotatable in a web take-up direction to wrap the web onto the spool and in a web payout direction to unwrap the web from the spool, anda signal processor configured to be responsive to the processed sensor signals to correlate the determined rotational direction and position of the spool assembly to the amount or length of the web paid out of, or taken up on, the spool assembly.

33. The apparatus of claim 32, further comprising: a lock pawl normally biased to a locked position in which the lock pawl engages the spool assembly, wherein, upon complete wrapping of the web onto the spool, the web on the spool acts against the lock pawl and moves the lock pawl to an unlocked position, and a sensor arm having one end engaged with the lock pawl and an opposite end carrying a magnet, wherein the sensor assembly includes another magnetic sensor fixed in position relative to the frame, and wherein the lock pawl, in one of the locked and unlocked positions, positions the magnet carried by the sensor arm over the another magnetic sensor such that the another magnetic sensor senses the magnet carried by the sensor arm, the lock pawl positions the magnet carried by the sensor arm away from the another magnetic sensor such that the magnetic sensor does not sense the magnet carried by the sensor arm, and wherein, after loss of electrical power is restored to the signal processor, the signal processor is configured to be responsive to a sensor signal produced by the another magnetic sensor to assign the reference position of the spool assembly to the position of the spool assembly at detection of the unlocked position of the lock pawl.

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