WO2019152891A2

WO2019152891A2 - Wheel end flow indicator

Info

Publication number: WO2019152891A2
Application number: PCT/US2019/016422
Authority: WO
Inventors: Dane HENRY
Original assignee: Equalaire Systems, Inc.
Priority date: 2018-02-01
Filing date: 2019-02-01
Publication date: 2019-08-08
Also published as: WO2019152891A3

Abstract

A tire inflation system fluid flow indicator having flow body with a supply port and a distribution port and a fluid channel disposed for sealed fluid communication therebetween. A plunger is disposed in the flow body, the plunger configured to substantially seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position, the plunger further configured to permit fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a second position, the plunger further configured to translate from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port. A visual indicator is disposed with respect to the flow body so as to indicate the first position or the second position of the plunger.

Description

WHEEL END FLOW INDICATOR

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to ET.S. Provisional Patent Application 62/625,273 entitled“Wheel End Flow Indicator” filed February 1, 2018, which is hereby entirely incorporated herein by reference.

FIELD

[0002] This application relates generally to tire pressure inflation systems.

BACKGROUND

[0003] Automatic tire inflation systems (ATIS) may be used to control vehicle tire pressure by adding fluid to one or more vehicle tires as needed during vehicle operation.

[0004] There exists a need for a device for indicating fluid flow to individual tires, particularly with respect to dual-tire configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 illustrates a vehicle with a tire inflation system installed.

[0006] FIG. 2 illustrates a set of tires with flow indicators installed.

[0007] FIG. 3 A illustrates an unactivated flow indicator.

[0008] FIG. 3B illustrates an activated flow indicator.

[0009] FIG. 4A is a partial section view of an unactivated flow indicator.

[0010] FIG. 4B is a partial section view of an activated flow indicator.

[0011] FIGS. 5A-5C illustrate shuttle plug positioning under different flow events.

[0012] FIG. 6A is a section view of an unactivated flow indicator.

[0013] FIG. 6B is a section view of an activated flow indicator.

[0014] FIG. 7 is a section view of a dual tire flow indicator.

[0015] FIG. 8 is a plan view of a flow indicator with offset indicator plungers.

[0016] FIG. 9A is a partial section view of an unactivated dual tire flow indicator.

[0017] FIG. 9B is a partial section view of a dual tire flow indicator having activated and unactivated states.

[0018] FIG. 10 illustrates a flow indicator having a rotary union disposed in the supply port.

[0019] FIG. 11 illustrates a flow indicator having a rotary union disposed in the supply port. SUMMARY

[0020] A fluid flow indicator comprising a flow body having a supply port and a distribution port and a fluid channel disposed for sealed fluid communication therebetween, the flow body being configured for mounting to a vehicle wheel end having a pneumatic tire, the distribution port being configured for sealed communication with the pneumatic tire, the supply port being configured for sealed communication with a vehicle fluid pressure supply; a plunger disposed in the flow body, the plunger configured to substantially seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position, the plunger further configured to permit fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a second position, the plunger further configured to translate from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port; and a visual indicator disposed with respect to the flow body so as to indicate the first position or the second position of the plunger.

DETAILED DESCRIPTION

[0021] As may be seen in FIG. 1, a vehicle 100 may comprise a truck 102 and a trailer 104. The truck 102 may include one or more drive axles 106 as part of the vehicle's powertrain. The truck 102 may further include a steer axle (not shown in detail) having pivotable spindles that may provide steering capability for the vehicle 100. The trailer 104 may include one or more fixed axles (not shown). Each axle may have one or more wheels 108 mounted thereto. A pneumatic tire 110 may be mounted to each wheel 108.

[0022] The vehicle 100 may be provided with an automatic tire inflation system (such as is shown in more detail in FIG. 2) that may use pressurized air from the vehicle's air brake system or some other source of pressurized air to maintain the tires at a desired air pressure. The automatic tire inflation system may be used to control air pressure in one or more of the tires 110 mounted to the steer axle (not shown), drive axle 106 and/or trailer axles (not shown). The automatic tire inflation system may include one or more air hoses 112 in fluid communication with each tire 110 for communicating air from the air pressure source to and from one or more of the tires 110.

[0023] FIG. 2 illustrates in more detail multiple embodiments of an automatic tire inflation system. A trailer 200 may include two axles 202, 204. Some trailers 200 may have dual tires 206, 208 mounted at each end of the axles 202, 204, as may be seen with respect to axle 202. Other trailers 200 may have a single tire 210, such as a super-single tire or a wide- base tire, mounted at each end of the axles 202, 204, as may be seen with respect to axle 204. The automatic tire inflation system may generally include a pressure regulator 214, which may be mounted in a control box, and one or more rotary air connections or rotary unions 216, 218 mounted in or near the axle ends as described in more detail below. The pressure regulator 214 may receive pressurized air from an air pressure source 220 through a conduit 212. The air pressure source 220 may comprise, for example, a vehicle air brake system air supply or a step-up or booster pump. The pressure regulator 214 may control, or increase or reduce the air pressure from the air pressure source 220 to an air pressure level suitable for inflating the tires 206, 208, 210, such as, for example, 110 psi. Pressurized air may flow from the pressure regulator 214 through conduit 222 to the axles 202, 204. From there, the air may flow through lines 230 (as seen with respect to axle 202) or through the sealed axle (as seen with respect to axle 204) to rotary connections 216, 218 to hoses 224, 232 to tire valves 219, 221, 223 connected to tires 208, 210, 206, respectively.

[0024] The axles 202, 204 may be wholly or partially solid or hollow, and may be configured in a variety of ways. For illustration purposes only, axles 202, 204 are hollow. For example, in some embodiments, an axle may comprise a solid beam having a spindle attached to each end (not shown). The axle spindles may be configured to allow mounting of wheel bearings upon which a hub may be rotatably mounted (not shown). In other embodiments, an axle may comprise a hollow tube having a spindle attached to each end. The spindles may be hollow, resulting in a hollow axle that is open at each end. Alternatively, the spindles may be wholly or partially solid, resulting in a hollow axle that is closed at each end.

[0025] In the embodiment of FIG. 2, for example, for truck trailers having a single tire 210 instead of dual tires, a single air hose 224 may be used to connect the single tire 210 to a port 226 of a rotary union or rotary fluid connection 216. A flow indicator 234 as describe more fully herein may be connected between the air hose 224 and the rotary union port 226, or between the tire valve 221 and the air hose 224, or at any point along the fluid flow path from the rotary union 216 to the tire valve 221. That is, the fluid flow indicator 234 may be coupled to a terminal end of the air hose 224 and to the tire inlet valve 221, or the fluid flow indicator 234 may be disposed between sections of hose 224 that overall join the rotary union 216 and the tire valve 221. In other embodiments, the rotary union and fluid flow indicator, or the air hose and fluid flow indicator may be integrated to form a unitary assembly.

[0026] Similarly, for dual-tire applications using two air hoses 232 (as seen in connection with tires 206 and 208 in FIG. 2), a dual-valve fluid flow indicator 236 may be attached to a rotary union 218 such that the outlet of the rotary union is coupled to the inlet port the fluid flow indicator 236. In other embodiments, a dual-valve fluid flow indicator may include the rotary union 218. The outlet ports of the fluid flow indicator may then have air hoses connected so as to allow fluid flow from the fluid flow indicator, through the hoses, and finally to the respective tire.

[0027] In other embodiments, two single-valve fluid flow indicators may be used for dual-tire applications, with each single-valve fluid flow indicator corresponding to one of the tires in the dual-tire arrangement. As with the single-tire application, a flow indicator may be connected between an air hose 232 and a port of the rotary union 218, or between the tire valve 219, 223 and an air hose 232, or at any point along the fluid flow path from the rotary union 218 to the tire valves. That is, the fluid flow indicator 236 may be coupled to a terminal end of an air hose 232 and to the tire inlet valve 219, 223 or the fluid flow indicator 236 may be disposed between sections of hose 232 that overall join the rotary union 218 and the tire valves 219, 223.

[0028] In yet other embodiments, a single-valve fluid flow indicator may be used to indicate fluid flow to dual tires in a dual-tire configuration. In such an embodiment, the distribution port may be in fluid communication with both tires. For tire inflation systems that rely on a single warning light to indicate fluid flow, such an embodiment can be used to indicate which wheel-end assembly on the truck or trailer is receiving fluid flow.

[0029] A flow indicator indicates whether or not a fluid flow is or has been present through the fluid flow indicator. The flow indicator includes a flow body, a plunger (not visible) disposed in the flow body, and a visual indicator. The flow body includes a supply port S and a distribution port D, and a fluid channel configured to provide fluid flow F between the supply port and the distribution port. The plunger is configured to translate in the fluid body in the fluid channel between a first position and a second position. In the first position, the plunger seals the fluid channel so that fluid cannot flow between the supply port and the distribution port. In the second position, the plunger allows fluid to flow in the fluid channel between the supply port and the distribution port. The plunger may comprise a seal that seals the fluid channel when in the first position. The seal may have a surface area on which fluid may impinge to translate the plunger from the first position to the second position.

[0030] When the fluid pressure in the supply port exceeds the fluid pressure at the distribution port, the plunger translates from the first position to the second position, thereby opening the fluid channel for fluid flow. When the plunger is in the first position, the visual indicator indicates no fluid flow. When the plunger is in the second position, the visual indicator indicates that fluid flow is occurring or has occurred. When the plunger moves to the second position from the first position, the plunger will remain in the second position even if fluid has stopped flowing from the supply port to the distribution port. The plunger may be reset by manually moving the plunger from the second position to the first position.

[0031] In some embodiments, the plunger may be configured to translate in the fluid body in the fluid channel between the second position and a third position. The plunger may move from the second position to the third position if the volume or pressure differential of fluid flowing through the fluid channel is sufficiently high. The volume or pressure differential of fluid sufficient to move the plunger from the second position to the third position may be set as a threshold volume or pressure differential to indicate or roughly correspond to the severity of tire damage. For example, a small tire puncture may not cause a large pressure drop in the tire and may require only a low volume of fluid to remain suitably inflated, whereas a larger gash or more significant tire damage may cause a larger pressure drop and permit higher volumes of fluid flow. In some embodiments, the second position and third position may be just two of a plurality of positions indicating various fluid flows.

[0032] As seen in FIGS. 3 A and 3B, a flow indicator 300 may signal whether or not a fluid flow is or has been present through the fluid flow indicator 300. The flow indicator 300 includes a flow body 304, a plunger (not visible) disposed in the flow body, and a visual indicator. In the embodiment of FIGS. 3A and 3B, the visual indicator comprises a cap 302 and stem 308. The stem 308 may be coupled to or be part of the flow body 304, such as at a stem portion 306. The cap 302 may be coupled to or be part of the plunger, and will move with the plunger as it translates in the flow body 304 from position to position.

[0033] A lack of flow since resetting of the fluid flow indicator 300 may be indicated by the plunger cap 302 being in a first position such that the rim of the plunger cap 302 is adjacent the stem portion 306 of the flow body 304. In such a position, the plunger cap 302 substantially covers the stem 308, thus shielding the stem 308 from view. A past or present flow may be indicated by the plunger cap 302 being in a second or raised position such that the stem 308 is visible. In some embodiments, the stem may have high visibility markings 310. In other embodiments, the position of the plunger cap relative to the stem may show translation of the plunger from a first position to a second position, thus indicating fluid flow. To reset the flow indicator, such as after remediation of a flow event that resulted in a raised plunger cap 302, the plunger cap 302 may have a downward force applied to the cap so as to return to the lowered position and covering the plunger stem 308 and high visibility markings 310. A flow event may be caused, for example, by a tire puncture or gash, or tire blowout.

[0034] As illustrated in FIGS. 4A and 4B, a single-value flow indicator 400 may generally comprise a flow body 402, a plunger 404, and a supply port S and a distribution port D connected by a fluid channel. In some embodiments, the flow body 402 may comprise a plurality of sub-bodies to allow for ready disassembly and maintenance, such as shown in FIG. 4A and 4B. In the embodiment of FIG. 4A and 4B, a sub-body lower plunger head 410 and sub-body flow indicator body 408 may be joined to a sub-body flow channel body 406 which together form the flow body 402. The sub-bodies 406, 408, and 410 may be joined by fasteners, bolts, adhesive, RF weld, screws, rivets, latches, threaded coupling, or any other suitable joinder. In other embodiments, the flow indicator may comprise a unitary body or other sub assemblies. The flow channel body 406 may comprise a fluid supply port S and distribution port D wherein the ports are connected by a series of fluid transportation channels that form a fluid channel in the channel body 406. A fluid supply channel 414 extends in the fluid supply port S to a plunger channel 412. An upper seal 430 may be disposed on the plunger rod 424 at the upper terminus of the plunger channel 412 so as to prevent fluid leakage at the point. A lower seal 432 may be disposed on the rod 424 at the lower terminus of the plunger channel 412 so as to prevent fluid leakage at the point. A delivery fluid channel 416 extends from the plunger channel 412 in the distribution port D.

[0035] In some embodiments, plunger rod 424 may enable pressure biasing by means of variation in the rod diameter or tightness of the seal around the plunger rod. For instance, a larger outer diameter of the rod or tighter seal may increase the threshold pressure at which the associated indicator translates, or the amount of translation affected by a particular flow event. In some embodiments, the rod 424 may be of different diameters at the upper seal 430 and the lower seal 432 so as to enable the biasing feature.

[0036] In some embodiments, the flow channel body may have a removable top plate 444 that couples to the flow channel body and the fluid flow indicator body 408. The top plate may have a toroidal boss 446 concentric with the plunger channel 412. The boss may have a seal 448, such as an o-ring, disposed such that the seal aids to prevent fluid leakage at points where the top plate and plunger channel interact. A top plate 444 as described may enable access to plunger channel and components of the fluid flow indicator plunger for maintenance and repair functions. In other embodiments the top plate and fluid flow indicator body 408 may be a unitary structure.

[0037] In some embodiments, the lower plunger head may comprise an attachment flange 418 and a rod acceptance body 420. The attachment flange 418 may follow the same profile as the flow channel body 406 and have holes disposed to accept fasteners as needed. The rod acceptance body 420 may be located at the lower face of the attachment flange 418 and have a lower orifice along its central axis so as to form a void into which the end of the plunger 404 may reside. This body may also have a vent 421 that connects the lower orifice to atmosphere so as to prevent pressure differentials when the plunger translates along its path.

[0038] In the embodiment of FIG. 4B, the fluid flow indicator body 408 may comprise an indicator stem 422 extending from stem flange 423. The stem flange 423 may have holes disposed so as to accept fastenings for assembling the sub-bodies 406, 408, and 410 into the unified flow body 402. The rod 424 of the plunger 404 may pass through the stem and into the flow body 402. A plunger cap 426 of indicator plunger 404 may fit over and substantially cover the indicator stem 422 when indicating that a flow event has not occurred.

[0039] The exterior of the indicator stem 422 may include high visibility markings 434 that visually convey that a fluid flow event has occurred with the tire associated with the fluid flow indicator plunger 404. These markings 434 may be realized as one or more graduated rings along the length of the stem 422 so as to indicate the degree of pressure differential or volume of fluid flowing between the supply port and distribution port of the fluid flow indicator 400 associated with the tire in question. The markings 434 may, for example, comprise colored o-rings, or painted or etched markings. In some embodiments, the markings may provide a dust or moisture seal between the plunger cap and the stem so as to resist debris and fluid ingress that might occur, such as during pressure washing of the wheel end.

[0040] A plunger 404 may comprise a plunger cap 426, plunger rod 424, and a shuttle plug 428. The plunger cap 426 may be a hollow cylinder that fits over an indicator stem 422 of the fluid flow indicator body 402. To the interior of the cap 426 may be attached the plunger rod 424. The rod 424 may extend into and through the plunger channel 412 of the flow body 402. The shuttle plug 428 is coupled to the rod 424 at a point so as to be disposed in the plunger channel 412 such that fluid flow is possible from the supply channel 414 through the plunger channel 412 and on through the distribution channel 416 when the plunger in a second position and the cap 426 is urged away from the fluid flow indicator body 408 (FIG. 4B), and disposed such that fluid flow is blocked from traveling through the plunger channel 412 to the distribution channel 416 (FIG. 4A) when the plunger is in a first position. When the shuttle plug 428 is in the first position to block fluid flow and a flow is presented at the plunger channel 412 from the supply channel 414, the resultant pressure force on the shuttle plug 428 will, in the absence of countervailing fluid pressure from the distribution channel 416, urge the fluid flow indicator plunger 404 as a whole to translate upward and thus the plunger cap 426 is urged away from the fluid flow indicator body 408. The fluid flow indicator plunger 404 will remain in this position until reset manually by user.

[0041] In some embodiments, the plunger rod 424 may be hollow and maintain a vent orifice 429 adjacent to the upper terminus of the rod. The vent orifice may be in fluid communication with the vent orifice 421 through the plunger rod 409 so as to prevent fluid vacuums to occur at the ends of the plunger 409.

[0042] The shuttle plug 428 may be of any suitable shape, such as a disc, a toroid or a cylinder. Other geometries may be suitable for a shuttle plug depending on the bore shape of the fluid channel. For example, a generalized diamond shape or a slightly rhombus like design may be utilized. The shuttle plug 428 may have a seal 436, such as an o-ring, disposed circumferentially so as to prevent or substantially prevent pressurized fluid from the fluid supply S from escaping past the shuttle plug 428. In some embodiments, the shuttle plug 428 may be a seal 436 having a surface area against which fluid pressure may act so as to provide translation force to the plunger 404. In some embodiments, the seal 436 may the seal 436 may fully seal the fluid channel between the supply port S and the distribution port D so as to prevent fluid from passing from the supply port S to the distribution port D. In other embodiments, the seal 436 may substantially seal the supply port S fluid channel between the distribution port D so as to allow a trickle of fluid to pass from the supply port S to the distribution port D without causing translation of the plunger 404. Such substantial sealing permits minor pressure maintenance of the tire while allowing fluid flow due to larger tire leaks (such as may be caused by small punctures) to move the plunger 404. For example, substantial sealing may be provided by a groove in the fluid channel wall or an undersized shuttle plug or seal so as to allow such a trickle of fluid.

[0043] In some embodiments, such as embodiments in which the seal 436 fully seals the fluid channel between the supply port S and the distribution port D so as to prevent fluid from passing from the supply port S to the distribution port D, a bypass channel connecting the supply port S to the distribution port D separately from the fluid channel may be provided to allow such a trickle of fluid. In yet other embodiments, a fluid channel groove may be provided in addition to a bypass channel.

[0044] In some embodiments, the shuttle plug 428 may be formed as part of the rod

424 [0045] In further embodiments, the plunger cap 426 may comprise a knob or flared portion of the plunger rod 424 instead of a cap shape. The rod end may be flared so as to permit manual movement of the rod. In such embodiments, indicator markings may be provided on the rod 424 rather than on the stem. In yet further embodiments, stems need not be used, such that the rod 424 may extend out of the flow body. In other embodiments, indicator markings may be provided on the flow body 402, such that movement of the rod 424 to allow fluid flow between the fluid supply S and distribution port D will reveal or uncover an indicator marking. In yet other embodiments the flow body may comprise a window through which the plunger rod may be seen. In such embodiments, the plunger may comprise an indicator portion that forms a visual indicator or part through. In some embodiments, the rod 424 may be held by friction to the flow body 402 so as to permit the rod end to remain translated away from the flow body 402 after fluid flow has decreased or stopped, thus providing a record of fluid flow.

[0046] In some embodiments, such as may be seen in FIGS. 5A-5C, the bore of plunger channel 502 may be tapered at least partially along its length. Such tapering may prevent seal (such as an o-ring) damage when the seal 508 traverses the intersection of the plunger channel and supply channel 506 or distribution channel 504. Such tapering may also allow rough indication of flow volume. The taper may be graded such that the shuttle plug 510 would travel along the bore sufficient to allow the air to flow, with the amount of travel corresponding roughly to the volume of air flow, as depicted in FIGS. 5A, 5B and 5C. As the plunger travels, so the plunger cap (not shown) will travel, thus permitting visual indication of the amount of air flow.

[0047] Another embodiment of a single valve flow indicator 600 may be seen in FIGS. 6 A and 6B. In FIG. 6 A, the fluid flow indicator 600 shows that there has not been a flow event as the plunger cap 602 is adjacent the top face of the fluid flow indicator body 604 and thus high visibility markers 606 are not exposed to sight. In the disclosed embodiment, the markers 606 may be one or more equidistant parallel indentions on the face of the fluid flow indicator stem 608. In FIG. 6B, the fluid flow indicator 600 communicates that there has been or there is currently a flow event as the plunger cap 602 been urged away from the top face of the fluid flow indicator body 604 and thus high the visibility markers 606 are exposed to sight. In such an embodiment, the markers 606 may be one or more equidistant parallel indentions on the face of the fluid flow indicator stem 608. In some embodiments, the delivery port S and the distribution port D may extend from the side walls of the flow channel body 610 whereas in the embodiments of FIGS. 6A and 6B the ports S and D are at the surface of the walls of the flow channel body 610 such that threaded connections 611 for air hose adapters (not shown) are recessed into the flow channel body. A lower vent 614 may be disposed at the terminal end of the plunger channel 616 such that a pressure differential cannot form when the plunger translates. In some embodiments, the plunger rod 618 may be hollow with a vent orifice 612 adjacent to the upper terminal end of the rod a pressure differential cannot form when the plunger translates. In the embodiment of FIGS. 6A and 6B, the plunger channel 616 has a non-tapered bore.

[0048] As illustrated in FIG. 7, a dual valve flow indicator 700 may be similar in function and design as a single tire indicator but with two indicator plungers incorporated into the indicator. Such a flow indicator 700 may be used for dual tire applications, and may comprise a flow channel body 702, an indicator body 714, a lower plunger body 712, a fluid supply port S, two distribution ports Dl and D2 each corresponding to a tire, and two plungers 704 and 705 each corresponding to a distribution port Dl or D2. The fluid flow indicator 700 may be mounted at a vehicle wheel end, such as to a hubcap-mounted rotary union, or by a wheel-end bracket, by attachment to a vehicle fairing or wheel cover, or may have a rotary union as a component of the fluid flow indicator and attached to the vehicle in place of a non-indicating rotary union of a tire inflation system.

[0049] In some embodiments, the flow channel body 702 may comprise a plurality of parts to allow for ready disassembly and maintenance. A lower plunger body 712 and fluid flow indicator body 714 may be joined to the flow channel body 702. The parts may be joined by fasteners, bolts, adhesive, RF weld, screws, rivets, latches, threaded coupling, or any other suitable joinder. The channel body 702 includes a fluid supply port S and distribution ports Dl and D2. A first fluid supply channel 716 extends from the fluid supply port S to a first plunger channel 718. A first distribution channel 720 extends from the plunger channel 718 to the distribution port Dl. A second fluid supply channel 722 extends from the fluid supply port S to a second plunger channel 724. A second distribution channel 726 extends from the plunger channel 724 to the distribution port D2. A first indicator plunger 704 may be associated with a distribution port Dl. A second indicator plunger 705 may be associated with a distribution port D2. Plunger channels 718 and 724 may

respectively have vents 719 and 725 to atmosphere disposed at or adjacent to the lower terminus of the channels.

[0050] An indicator plunger 704 may comprise a plunger cap 732, plunger rod 734, and shuttle plug 736. The plunger cap 732 may be a hollow cylinder that fits over a stem 738 of the fluid flow indicator body 714. To the interior of the cap 732 may be attached the rod 734. The plunger rod 734 may extend along the plunger channel 718. The shuttle plug 736 is coupled to the rod 734 at a point so that the shuttle plug 736 position in the plunger channel 718 exposes the supply channel 716 opening to fluid flow when the pressure differential between supply and port Dl urge the plug 738 away from the first fluid supply channel 716, and seals the distribution channel 720 from fluid flow when the cap 732 is urged toward the fluid flow indicator body 714 (similar to the position shown by plunger cap 744 and shuttle plug 748). In the second position shown for plunger rod 734, pressurized fluid may flow from the fluid supply S to the distribution port Dl. Seals 740 and 742 may be provided so as to seal the rod 734 to the channel body 702.

[0051] A second indicator plunger 705 similarly comprises a plunger cap 744, plunger rod 746, and shuttle plug 748. The plunger cap 744 may be a hollow cylinder that fits over a stem 750 of the fluid flow indicator body 714. To the interior of the cap 744 may be attached the rod 746. The rod 746 may extend along the plunger channel 724. The shuttle plug 748 is coupled to the rod 746 at a point so that the plug 748 position in the plunger channel 724 exposes the distribution channel 726 opening to fluid flow when the pressure differential between the supply and port D2 urges the plug 748 away from the second fluid supply channel 722 (similar to the position shown by plunger cap 732 and shuttle plug 736), and seals the distribution channel 726 from fluid flow when the cap 744 is urged toward the fluid flow indicator body 714 (as shown). In the position shown, pressurized fluid may be prevented from flowing from the fluid supply S to the distribution port D2. Seals 741 and 743 may be provided so as to seal the rod 746 to the channel body 702. Further seals 737 and 749 may be respectively disposed at the shuttle plugs 736 and 748 to seal the plug to the plunger channels 718 and 724, respectively. In some embodiments, plunger rods 734 and 746 may be generally hollow with a vent 735 and 747 to atmosphere disposed respectively at or adjacent to the upper terminus of the rods.

[0052] In the embodiment shown in FIG. 7, the fluid flow indicator body 714 comprises two indicator stems 738 and 750. In applications involving more than two tires at a wheel end, a suitable number of plunger valves may be provided to correspond to the number of times on the wheel end. The rods 734 and 746 of the indicator plungers may respectively pass through the stems and into the channel body. The plunger caps 732 and 744 of indicator plungers 704 and 705 may fit over indicator stems 738 and 750 when indicating that a flow event has not occurred. The exterior of these indicator stems 738 and 750 may include high visibility markings 752 that visually convey that a fluid flow event has occurred with the tire associated with that particular indicator plunger 704 or 705. Such indication may be provided when the end of the plungers 704 and/or 705 translate away from the fluid flow indicator body 714, thus revealing the high visibility markings 752. These markings 752 may be realized as a set of graduated rings along the length of the stem 738 so as to indicate the degree of pressure differential or flow volume seen between the supply and tire delivery ports of the fluid flow indicator associated with the tire in question. The markings may, for example, comprise colored O-rings, elongated triangular markings along the stems, or painted or etched markings. In some embodiments, the plunger position relative to the flow body may provide a visual indicator to indicate flow. In some embodiments, the markings may provide a dust or moisture seal between the plunger cap and the stem so as to resist fluid ingress that might occur, such as during pressure washing of the wheel end.

[0053] In further embodiments, the plunger cap may comprise a knob or flared portion of the plunger rod instead of a cap shape. The rod end may be flared so as to permit manual movement of the rod. In such embodiments, indicator markings may be provided on the rod rather than on the stems. In yet further embodiments, stems need not be used, such that the rods may extend out of the flow body. In other embodiments, indicator markings may be provided on the flow body, such that movement of the rod to allow fluid flow between the fluid supply S and distribution port D will reveal or uncover an indicator marking. In some embodiments, the rod may be sealed to the flow body so as to permit the rod end to remain translated away from the flow body after fluid flow has decreased or stopped, thus providing a record of fluid flow.

[0054] Referring again to FIG. 7, it may be seen that the channel body 702 may have fluid channels disposed through the channel body 702. These channels may serve to allow transfer of the delivered fluid from the supply port S to the delivery ports Dl and D2. During the fluid transfer, the fluid may flow from the supply port S, through the desired supply channel 716 or 722, and to the associated plunger channel 718 or 724. If, for example, the tire pressure at port Dl is lower than the desired tire fluid pressure provided at supply port S, pressurized fluid from supply port S may interact with the shuttle plug 736 and effect a translation of the plug 736 and plunger 704 due to the pressure differential created by the low tire pressure and higher supply pressure seen at opposing faces of the shuttle plug 736. This translation of the plunger 704 may move the shuttle plug 736 upward through the plunger channel 718 and thus expose the associated distribution channel 720. The fluid may then flow through the first distribution channel 720 to the associated distribution port Dl . Fluid pressure may similarly act on shuttle plug 748 if the fluid pressure at distribution port D2 is lower than the fluid pressure from the fluid supply S. In other embodiments, the third channels 718 and 724 may be tapered as described in connection with the embodiment of FIGS. 4 A and 4B.

[0055] A tire of proper inflation may not allow the actuation of a plunger as there would be substantially equal pressure forces acting on the supply and tire delivery faces of the plunger. Furthermore, a tire of low pressure whose pressure has not fallen below the threshold required for the tire inflation system to engage may also not allow the plunger to translate far enough to expose the tire delivery channel to communication with the supply channel. This prevention of communication for slightly deflated tires may be realized by the frictional forces of the plug and plunger channels exceeding the difference in pressure forces exerted at the opposing faces of the plug.

[0056] In some embodiments, the length of the shuttle plug 736 may be such that slight translation of the plug may not facilitate fluid communication between the supply and delivery channels. In such cases, minor shifts from vibration from the vehicle or minor pressure differentials between the channels may not result in false flow event indications.

[0057] In some embodiments, the seals 737, 749 may allow a trickle of fluid to pass from the supply port S to the distribution ports Dl and D2 without causing translation of the plungers 704, 705, so as to permit pressure maintenance of the tire while allowing fluid flow due to larger tire leaks (such as may be caused by small punctures) to move the plungers 704, 705. In some embodiments, one or more bypass channels as described above may be provided to allow such a trickle of fluid. In some embodiments, the shuttle plugs 736, 748 may be formed as part of the rods 734, 746.

[0058] Furthermore, the ports S and D may accept air hose connectors at the port. These connectors may allow for the mating of the fluid flow indicator to hoses or other upstream and downstream tire inflation system components.

[0059] In yet another embodiment, as seen in FIG. 8, not all indicator plungers may be located on the same side as one another. Plungers may be offset from one another so as to balance the mass distribution around the centroid of the fluid flow indicator and thus prevent a misbalance in the wheel to which the fluid flow indicator is attached. An indicator plunger 802 may be disposed on one side of the fluid flow indicator while another plunger 804 is on the opposing side of the fluid flow indicator in relation to axis H and axis W.

[0060] Referring to FIGS. 9 A and 9B, an inflation indicator 900 may have a plurality of indicator plungers 902, 904. In the embodiment of FIG. 9A, both plungers 902, 904 are unactivated and thus showing there has not been a flow event since the fluid flow indicator was last reset. In FIG. 8B, an indicator plunger 904 is in the activated position, thus showing a flow event has occurred. An indicator 902 is in the unactivated position, thus indicating no flow event has occurred since the last reset. Resetting of an activated plunger may be accomplished by applying force to the plunger cap to urge the cap toward the flow body 906 when the flow event has been resolved. A fluid flow indicator may include more than two plungers, depending on the number of tires associated with the fluid flow indicator.

[0061] The fluid flow indicator may be formed of any material compatible with the environmental conditions and hazards associated with a commercial vehicle. Such hazards may include, but are not be limited to, prolonged UV exposure, high temperatures from weather and vehicle operation, low temperatures as experienced from weather local to the vehicle, corrosive chemicals associated with vehicle systems and vehicle maintenance, abrasion, and mechanical and temperature related stresses. A synthetic polymer or monomer material, such as ABS, may be an ideal material for construction of the bodies. Yet, other materials such as aluminum, steel, other metals, or metal alloys may also be considered as suitable materials, brass being an example of one possible suitable alloy.

[0062] As noted above, yet further embodiments, the flow indicator may be coupled to a rotary union for a tire inflation system. In other embodiments, the flow indicator may comprise a portion of a rotary union or rotary air connection for a tire inflation system. For example, as may be seen in Fig. 10, a rotary air connection may be provided as generally described in US Patent 6,698,482, which is incorporated herein fully by reference. The rotary union may be configured for mounting to a vehicle hubcap for use with an automatic tire inflation system having a pressure supply internal to the vehicle axle to which the wheel end is mounted. The vehicle axle may be hollow and sealed to serve as a conduit for pressurized fluid from a vehicle fluid pressure source, or may have an air conduit disposed within connecting the rotary union to a vehicle fluid pressure source. A flow indicator 950, such as the embodiment of Fig. 8, may have a tubular member 952 disposed in the supply port 954. The tubular member 952 may in various embodiments rotate or be stationary with respect to the flow indicator 950. The tubular member 952 may be configured for translatable and/or rotatable disposition in a stator disposed in the end of an axle. A bearing 956 may be disposed between an end 958 of the tubular member 952 and a face 960 of the supply port. A fluid channel 962 in the bearing may allow pressurized fluid to flow from a fluid supply source through the tubular member into the supply port. A seal 964, such as an o-ring or lip seal, may be disposed about the tubular member so as to seal the tubular member and flow indicator. A cap 966 may be disposed in the inlet about the tubular member so as to retain the end 958 of the tubular member and bearing 956 in the flow indicator. The tubular member may be rigid, flexible, or a combination of rigid or flexible members. Distribution ports Dl and D2 may each be sealingly connected to a vehicle tire.

[0063] A flow indicator 970 (whether for one or more vehicle tires) as described herein may be used in connection with any other rotary air connection suitable for a vehicle tire inflation system. For example, as may be seen in Fig. 11, a face seal 972 may be provided in connection with the flow indicator 970, such as the face seal disclosed in US Patent 6,105,645, which is incorporated herein fully by reference. The rotary union may comprise a rigid shaft 974, a graphite member 976 and a spring 978. The spring and graphite member may be disposed in the supply port 980 of the flow indicator. The spring may urge the graphite member 976 against the rigid shaft 974, thereby forming a face seal 972.

Bearings 982 may allow the valve assembly to rotate with respect to the rigid shaft. The rigid shaft may be sealingly connected to a flexible tubular member 984, which may in turn be sealingly connected to a fluid source in an axle 986. Pressurized fluid may flow through the flexible tubular member, rigid shaft, graphite member and spring into the supply port. The rigid shaft may comprise steel. A washer and o-ring may be disposed between the spring and graphite member. The flow indicator 970 may be mounted to the exterior of a hubcap 988. Distribution ports Dl and D2 may each be sealingly connected to a vehicle tire.

[0064] In yet other embodiments, a flow indicator as described herein may be used in connection with an external rotary union, such as is disclosed in PCTUS2014065006 and incorporated herein by reference. The supply port may be coupled to the external rotary union, which may be mounted to a vehicle fairing or to a wheel end. The external rotary union may be mounted to a bracket. The bracket may be coupled to a wheel end, and may rotate with the wheels on that wheel end. Alternatively, the bracket may be mounted to a wheel or fairing by any suitable fastener.

[0065] An external rotary union may comprise a shaft disposed within a housing. A radial bushing may be disposed between the shaft and the housing. The bushing may comprise an oil- impregnated material, such as oilite bronze alloy, or PTFE, nylon, or any other suitable wear- resistant material with a relatively low coefficient of friction. In other embodiments, roller or ball bearings may be used in place of a bushing. The housing may comprise a lip which may help retain the bushing within the housing. In some embodiments, an annular seal may be disposed between the lip and the bushing. In some embodiments, the annular seal may comprise a lip seal.

[0066] In some embodiments, the shaft may be restrained from translating within the bushing (or bearing) by placement of a retaining ring disposed about the shaft. A washer may be disposed between the bushing and the retaining ring.

[0067] In some embodiments, an end cap may be coupled to the housing, e.g., by screw threads. In other embodiments, the housing and end cap may comprise a unitary item of manufacture. A splash shield may be disposed about the shaft against the lip end of the housing to shield the annular seal from debris, high-volume or high- velocity liquid flow and other environmental hazards. In some embodiments, a washer may be disposed between the splash shield and the end of the housing. A retaining ring may be used to prevent the splash shield from sliding off of the shaft.

[0068] A fluid flow indicator as described herein may be coupled to such an external rotary union. The supply port of the fluid flow indicator may be coupled to the shaft or to the housing of the external rotary union.

[0069] The foregoing may thus be variously embodied according to the following numbered clauses:

[0070] 1. A fluid flow indicator comprising a flow body having a supply port and a distribution port and a fluid channel disposed for sealed fluid communication therebetween, the flow body being configured for mounting to a vehicle wheel end having a pneumatic tire, the distribution port being configured for sealed communication with the pneumatic tire, the supply port being configured for sealed communication with a vehicle fluid pressure supply; a plunger disposed in the flow body, the plunger configured to substantially seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position, the plunger further configured to permit fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a second position, the plunger further configured to translate from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port; and a visual indicator disposed with respect to the flow body so as to indicate the first position or the second position of the plunger.

[0071] 2. The fluid flow indicator of clause 2, the plunger comprising a seal configured to seal the fluid channel between the supply port and the distribution port when the plunger is disposed in the first position, the seal having a surface area against which fluid may exert translating pressure.

[0072] 3. The fluid flow indicator of clause 2 the plunger configured to permit a first fluid flow in the fluid channel when the plunger is disposed in the second position, and the plunger further configured to permit a second fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a third position, the second fluid flow being greater than the first fluid flow; and the visual indicator further disposed with respect to the flow body so as to indicate the third position of the plunger.

[0073] 4. The fluid flow indicator of clause 3, the fluid channel having a tapered bore along which the plunger may translate between the first position and the second position, and along which the plunger may translate between the second position and the third position.

[0074] 5. The fluid flow indicator of clause 4, the plunger being configured to move from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port, and to move from the second position to the third position when the volume of fluid flow exceeds a threshold volume.

[0075] 6. The fluid flow indicator of clause 1, the visual indicator comprising a stem coupled to the flow body; and a cap coupled to the plunger and configured to substantially cover the stem when the plunger is in the first position and reveal the stem when the plunger moves from the first position to the second position.

[0076] 7. The fluid flow indicator of clause 3, the visual indicator comprising a stem coupled to the flow body; and a cap coupled to the plunger and configured to substantially cover the stem when the plunger is in the first position and reveal the stem when the plunger moves from the first position to the second position and further reveal the stem when the plunger moves from the second position to the third position.

[0077] 8. The fluid flow indicator of clause 7, the stem having a first visually- perceptible marking corresponding to the second plunger position, and a second visually- perceptible marking corresponding to the third plunger position.

[0078] 9. The fluid flow indicator of clause 8, first visually-perceptible marking having a different color from the second visually-perceptible marking.

[0079] 10. The fluid flow indicator of clause 1 or clause 3, the plunger comprising an indicator portion extendable from the flow body, the visual indicator comprising the indicator portion.

[0080] 11. The fluid flow indicator of clause 10, the indicator portion configured to extend a first distance from the flow body when the plunger is in the second position and extend a second distance from the body when the plunger is in the third position.

[0081] 12. The fluid flow indicator of clause 11, the indicator portion having a first visually-perceptible marking corresponding to the second plunger position, and a second visually-perceptible marking corresponding to the third plunger position.

[0082] 13. The fluid flow indicator of clause 1 or clause 3, the flow body comprising a window, the plunger comprising an indicator portion visible through the flow body window, the visual indicator comprising the indicator portion.

[0083] 14. The fluid flow indicator of clause 13, the indicator portion comprising a first section visible in the flow body window when the plunger is in the second position and a second section visible in the flow body window when the plunger is in the third position.

[0084] 15. The fluid flow indicator of clause 13, the indicator portion having a first visually-perceptible marking corresponding to the second plunger position, and a second visually-perceptible marking corresponding to the third plunger position.

[0085] 16. The fluid flow indicator of clause 1 further comprising a rotary union coupled to the supply port.

[0086] 17. The fluid flow indicator of clause 16, the rotary union comprising a tube having an end pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a pivotable sealing interface between the tube and the supply port.

[0087] 18. The fluid flow indicator of clause 17, the annular seal comprising an o- ring or a lip seal.

[0088] 19. The fluid flow indicator of clause 18, the rotary union comprising a bearing disposed between the end of tube and the supply port.

[0089] 20. The fluid flow indicator of clause 16, the rotary union comprising a rigid shaft rotatably and non-pivotably disposed in the supply port; and a bearing non- rotatably disposed between the shaft and the supply port, the interface between the bearing and the shaft forming a fluid face seal.

[0090] 21. The fluid flow indicator of clause 16, the rotary union comprising a tube rotatably and non-pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a sealing interface between the tube and the supply port.

[0091] 22. The fluid flow indicator of clause 21, the annular seal comprising an o- ring or a lip seal.

[0092] 23. The fluid flow indicator of clause 1 further comprising a rotary union disposed in the supply port.

[0093] 24. The fluid flow indicator of clause 1, the plunger comprising a hollow rod; and the flow body comprising one or more vents to atmosphere in fluid communication with the hollow rod.

[0094] 25. The fluid flow indicator of clause 1, the fluid channel comprising a groove configured to permit a trickle of fluid from the supply port to the distribution port past the plunger. [0095] 26. The fluid flow indicator of clause 1, the flow body comprising a bypass channel configured to permit a trickle of fluid from the supply port to the distribution port separate from the fluid channel.

[0096] 27. The fluid flow indicator of clause 1 or clause 26, the plunger configured to fully seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position.

[0097] 28. The fluid flow indicator of clause 1 further comprising the distribution port being a first distribution port, the fluid channel being a first fluid channel, the pneumatic tire being a first pneumatic tire, the plunger being a first plunger, the visual indicator being a first visual indicator, and the vehicle wheel end having a second pneumatic tire; a flow body having a second distribution port and a second fluid channel disposed for sealed fluid communication between the supply port and the second distribution port, the second distribution port being configured for sealed communication with the second pneumatic tire; a second plunger disposed in the flow body, the plunger configured to substantially seal the second fluid channel between the supply port and the second distribution port when the second plunger is disposed in a third position, the second plunger further configured to permit fluid flow in the second fluid channel between the supply port and the second distribution port when the second plunger is disposed in a fourth position, the second plunger further configured to translate from the third position to the fourth position when fluid pressure at the supply port exceeds the fluid pressure at the second distribution port; and a second visual indicator disposed with respect to the flow body so as to indicate the third position or the fourth position of the second plunger.

[0098] 29. The fluid flow indicator of clause 28 further comprising a rotary union disposed in or coupled to the supply port.

[0099] 30. The fluid flow indicator of clause 29, the rotary union comprising a tube having an end pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a pivotable sealing interface between the tube and the supply port.

[0100] 31. The fluid flow indicator of clause 30, the annular seal comprising an o- ring or a lip seal.

[0101] 32. The fluid flow indicator of clause 31, the rotary union comprising a bearing disposed between the end of tube and the supply port.

[0102] 33. The fluid flow indicator of clause 29, the rotary union comprising a rigid shaft rotatably and non-pivotably disposed in the supply port; and a bearing non- rotatably disposed between the shaft and the supply port, the interface between the bearing and the shaft forming a fluid face seal.

[0103] 34. The fluid flow indicator of clause 29, the rotary union comprising a tube rotatably and non-pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a sealing interface between the tube and the supply port.

[0104] 35. The fluid flow indicator of clause 34, the annular seal comprising an o- ring or a lip seal.

[0105] 36. The fluid flow indicator of clause 29, the vehicle wheel end comprising a hubcap, the rotary union configured to mount to a hubcap.

[0106] 37. The fluid flow indicator of clause 29, the rotary union being an external rotary union.

[0107] Although the present flow indicator and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular

embodiments of the process, machine, manufacture, composition, or matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. For example, although the disclosed apparatus, systems and methods may be described with reference to a manual or manually-activated pressure reduction valve, an electric valve or other automatic electronic or mechanical valve may be used to accomplish relatively rapid reduction of fluid pressure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, systems or steps.

Claims

I claim:

1 A fluid flow indicator comprising:

a flow body having a supply port and a distribution port and a fluid channel

disposed for sealed fluid communication therebetween, the flow body being configured for mounting to a vehicle wheel end having a pneumatic tire, the distribution port being configured for sealed communication with the pneumatic tire, the supply port being configured for sealed communication with a vehicle fluid pressure supply;

a plunger disposed in the flow body, the plunger configured to substantially seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position, the plunger further configured to permit fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a second position, the plunger further configured to translate from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port; and

a visual indicator disposed with respect to the flow body so as to indicate the first position or the second position of the plunger.

2. The fluid flow indicator of claim 2, the plunger comprising a seal configured to

substantially seal the fluid channel between the supply port and the distribution port when the plunger is disposed in the first position, the seal having a surface area against which fluid may exert translating pressure.

3. The fluid flow indicator of claim 2:

the plunger configured to permit a first fluid flow in the fluid channel when the plunger is disposed in the second position, and the plunger further configured to permit a second fluid flow in the fluid channel between the supply port and the distribution port when the plunger is disposed in a third position, the second fluid flow being greater than the first fluid flow; and

the visual indicator further disposed with respect to the flow body so as to indicate the third position of the plunger.

4. The fluid flow indicator of claim 3, the fluid channel having a tapered bore along which the plunger may translate between the first position and the second position, and along which the plunger may translate between the second position and the third position.

5. The fluid flow indicator of claim 4, the plunger being configured to move from the first position to the second position when fluid pressure at the supply port exceeds the fluid pressure at the distribution port, and to move from the second position to the third position when the volume of fluid flow exceeds a threshold volume.

6. The fluid flow indicator of claim 1, the visual indicator comprising:

a stem coupled to the flow body; and

a cap coupled to the plunger and configured to substantially cover the stem when the plunger is in the first position and reveal the stem when the plunger moves from the first position to the second position.

7. The fluid flow indicator of claim 3, the visual indicator comprising:

a stem coupled to the flow body; and

a cap coupled to the plunger and configured to substantially cover the stem when the plunger is in the first position and reveal the stem when the plunger moves from the first position to the second position and further reveal the stem when the plunger moves from the second position to the third position.

8. The fluid flow indicator of claim 7, the stem having a first visually-perceptible

marking corresponding to the second plunger position, and a second visually- perceptible marking corresponding to the third plunger position.

9. The fluid flow indicator of claim 8, first visually-perceptible marking having a

different color from the second visually-perceptible marking.

10. The fluid flow indicator of claim 1 or claim 3, the plunger comprising an indicator portion extendable from the flow body, the visual indicator comprising the indicator portion.

11. The fluid flow indicator of claim 10, the indicator portion configured to extend a first distance from the flow body when the plunger is in the second position and extend a second distance from the body when the plunger is in the third position.

12. The fluid flow indicator of claim 11, the indicator portion having a first visually- perceptible marking corresponding to the second plunger position, and a second visually-perceptible marking corresponding to the third plunger position.

13. The fluid flow indicator of claim 1 or claim 3, the flow body comprising a window, the plunger comprising an indicator portion visible through the flow body window, the visual indicator comprising the indicator portion.

14. The fluid flow indicator of claim 13, the indicator portion comprising a first section visible in the flow body window when the plunger is in the second position and a second section visible in the flow body window when the plunger is in the third position.

15. The fluid flow indicator of claim 13, the indicator portion having a first visually- perceptible marking corresponding to the second plunger position, and a second visually-perceptible marking corresponding to the third plunger position.

16. The fluid flow indicator of claim 1 further comprising a rotary union coupled to the supply port.

17. The fluid flow indicator of claim 16, the rotary union comprising a tube having an end pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a pivotable sealing interface between the tube and the supply port.

18. The fluid flow indicator of claim 17, the annular seal comprising an o-ring or a lip seal.

19. The fluid flow indicator of claim 18, the rotary union comprising a bearing disposed between the end of tube and the supply port.

20. The fluid flow indicator of claim 16, the rotary union comprising a rigid shaft

rotatably and non-pivotably disposed in the supply port; and a bearing non-rotatably disposed between the shaft and the supply port, the interface between the bearing and the shaft forming a fluid face seal.

21. The fluid flow indicator of claim 16, the rotary union comprising a tube rotatably and non-pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a sealing interface between the tube and the supply port.

22. The fluid flow indicator of claim 21, the annular seal comprising an o-ring or a lip seal.

23. The fluid flow indicator of claim 1 further comprising a rotary union disposed in the supply port.

24. The fluid flow indicator of claim 1, the plunger comprising a hollow rod; and the flow body comprising one or more vents to atmosphere in fluid communication with the hollow rod.

25. The fluid flow indicator of claim 1, the fluid channel comprising a groove configured to permit a trickle of fluid from the supply port to the distribution port past the plunger.

26. The fluid flow indicator of claim 1, the flow body comprising a bypass channel configured to permit a trickle of fluid from the supply port to the distribution port separate from the fluid channel.

27. The fluid flow indicator of claim 1 or claim 26, the plunger configured to fully seal the fluid channel between the supply port and the distribution port when the plunger is disposed in a first position.

28. The fluid flow indicator of claim 1 further comprising:

the distribution port being a first distribution port, the fluid channel being a first fluid channel, the pneumatic tire being a first pneumatic tire, the plunger being a first plunger, the visual indicator being a first visual indicator, and the vehicle wheel end having a second pneumatic tire;

a flow body having a second distribution port and a second fluid channel disposed for sealed fluid communication between the supply port and the second distribution port, the second distribution port being configured for sealed communication with the second pneumatic tire;

a second plunger disposed in the flow body, the plunger configured to substantially seal the second fluid channel between the supply port and the second distribution port when the second plunger is disposed in a third position, the second plunger further configured to permit fluid flow in the second fluid channel between the supply port and the second distribution port when the second plunger is disposed in a fourth position, the second plunger further configured to translate from the third position to the fourth position when fluid pressure at the supply port exceeds the fluid pressure at the second distribution port; and

a second visual indicator disposed with respect to the flow body so as to indicate the third position or the fourth position of the second plunger.

29. The fluid flow indicator of claim 28 further comprising a rotary union disposed in or coupled to the supply port.

30. The fluid flow indicator of claim 29, the rotary union comprising a tube having an end pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a pivotable sealing interface between the tube and the supply port.

31. The fluid flow indicator of claim 30, the annular seal comprising an o-ring or a lip seal.

32. The fluid flow indicator of claim 31, the rotary union comprising a bearing disposed between the end of tube and the supply port.

33. The fluid flow indicator of claim 29, the rotary union comprising a rigid shaft rotatably and non-pivotably disposed in the supply port; and a bearing non-rotatably disposed between the shaft and the supply port, the interface between the bearing and the shaft forming a fluid face seal.

34. The fluid flow indicator of claim 29, the rotary union comprising a tube rotatably and non-pivotably disposed in the supply port; and an annular seal disposed about the tube so as to provide a sealing interface between the tube and the supply port.

35. The fluid flow indicator of claim 34, the annular seal comprising an o-ring or a lip seal.

36. The fluid flow indicator of claim 29, the vehicle wheel end comprising a hubcap, the rotary union configured to mount to a hubcap.

37. The fluid flow indicator of claim 29, the rotary union being an external rotary union.