Electrical Brush Contact

The present invention relates to an electrical brush contact and more particularly to such a contact which has improved resilience, greater durability and improved dependability.

The applicant is the owner of U.S. Pat. No. 3,252,135 on a Pressure Monitoring Apparatus, which discloses a system for the remote indication of tire pressures on automotive vehicles during movement of the vehicles. That apparatus of the patent employs a bellows which is mounted on a wheel and which is capable of expansion and contraction in response to tire pressure changes to activate a signal device visible to a vehicle operator when the tire pressure falls below a predetermined level. An electrical circuit is utilized which includes a stationary brush having one end rigidly mounted on the vehicle and an opposite end which makes intermittent contact with a contactor block 62 mounted on and rotating with a wheel so as to complete the circuit between the rotating wheel and the vehicle.

The contact of the present invention was invented in the solution to certain problems encountered by the Pressure Monitoring Apparatus and is conveniently described in relation thereto although not limited to such illustrative environment. As disclosed in the patent, each wheel rotation caused a closing and an opening of a brush contact. Such actuation results in fatigue and contact failure due to distortion or breakage.

It is therefore an object of the present invention to provide an improved electrical brush contact adapted reliably to complete and interrupt a circuit from a rotating circuit component to a non-rotating component.

It is another object to provide such a contact which resists deformation and breakage by protracted operation.

A further object is to provide such a contact capable of economical manufacture.

An additional object is to provide a contact which reacts cooperatively with a rotating member to conduct a pulse current.

A still further object is to provide a contact which allows intermittent electrical contact with a rotating member.

These and other objects and advantages will become more fully apparent upon reference to the following description.

FIG. 1 is a perspective view of an electrical brush contact embodying the principles of the present invention mounted on portions of an automotive vehicle which are fragmentarily represented.

FIG. 2 is an enlarged section taken on line 2--2 of FIG. 1.

FIG. 3 is an enlarged fragmentary top plan view of the contact shown in FIG. 1 together with an illustrative electrical circuit which is schematically represented.

FIG. 4 is a side elevation of a mounting plate of the invention of FIG. 1.

Referring in greater detail to the drawing, an environment for the present invention illustratively includes a wheel 10, shown in FIG. 1, rotatably mounted by an axle 13 having a housing 14. The wheel and axle constitute portions of an automotive vehicle not fully shown. A rotational direction corresponding to the forward movement of the vehicle is shown by the arrow 15. The wheel includes a rim 16 and an inflated pneumatic tire 17 mounted thereon. An elongated leaf spring 18 is disposed above and orthogonal to the axle and is mounted on the axle housing by encircling shackles 19. As a mounting facility for a portion of the present invention to which specific reference will be made, a U-bolt 20 with a crosspiece 21 is secured by nuts 22 around the spring forward of the axle.

As described, the present invention resulted as an improvement to the Pressure Monitoring Apparatus of U.S. Pat. No. 3,252,135 which provides an indication to a vehicle operator when the pressure in his tires has fallen below a predetermined level. The entire monitoring apparatus is not fully described herein but is completely described in the designated patent. It includes means in the form of a tire pressure detector to close a circuit on the wheel 10 when and if the tire pressure falls below a predetermined level, the wheel circuit being electrically connected to circuitry elsewhere on the vehicle by contact means which intermittently connects with the rotating wheel. The present invention relates only to an improvement in that contact means.

A portion of the monitoring apparatus is shown in FIG. 2 mounted on wheel 10 but is not part of the present invention, being included herein for clarity. The tire pressure detector 23, shown in FIG. 2, is mounted on the rim 16 in pneumatic communication with the inflated tire 17. A wire 24 electrically connects the detector 23 with a grooved contactor block 25 disposed on the periphery of the rim 16 adjacent to the axle housing 14 and serves as a contact rotating with wheel 10 which intermittently is connected to a non-rotating contact, next described.

Mounted on the crosspiece 21 is an embodiment of the present invention, an electrical brush contact, shown generally at 28, disposed to serve as the aforementioned non-rotating contact cooperating with the rotating block 25. A flat elongated bracket 30 of insulating material is mounted on the crosspiece 21 parallel with the spring 18 in spaced relation to the rim 16 and secured to the crosspiece by any suitable means, such as a bolt 31 and a nut 32. The crosspiece 21 preferably has an elongated slot 34 therein through which the bolt 31 extends to accommodate adjustment of the bracket toward and from the wheel. An elongated stud or pivot pin 35 is mounted on the top of the bracket 30 extending axially upwardly therefrom and protruding downwardly through the bracket 30. The pin is conveniently secured in position by a nut 36 screw-threadably mounted thereon and tightened upwardly against the bracket 30. A terminal 37 is axially mounted on the pin and secured by nut 36. A conductor wire 38 is connected to the terminal.

A helically coiled spring 42 circumscribes and is mounted on the pin 35. The spring has a lower end 43 anchored to the bracket 30 and a free end 44 extended toward the wheel when the spring is relaxed. A clamp 45 is connected to the free end of the spring. A brush consisting of a plurality of electrically conductive elongated wire bristles 57 of spring steel or the like is secured at one end thereof to the clamp and has an opposite end disposed in the path of travel of the contactor block 25. When the brush engages the block an electrical circuit is completed between the rotating and non-rotating members 10 and 14. The spring 42 serves as a resilient mount for the bristles, allowing flexing in the forward direction as the block 25 meets and passes beyond the bristles 57 in its rotary pattern thereby preventing deformation and damage to the bristles. A stop 60 is mounted atop the bracket 30 and secured by a screw 62 and a nut 64, adjacent to the pin 35 and rearwardly thereof in relation to the direction of wheel rotation. The stop is adapted to limit rearward pivotal movement of the clamp 45 and bristles 57.

The wire 38 connects the pivot pin 35, and hence the bristles 57, to a non-revolving electrical circuit 70, shown schematically in FIG. 3. The circuit includes terminals 71 representing possible connections to devices on other wheels of the automotive vehicle which would be connected in parallel with the electrical system shown for wheel 10. All such interconnections are fed into one side of a transformer primary 72 having a corresponding secondary 73 which is connected to a neon bulb 74 located within view of the vehicle operator and adapted for excitation by passage of a fluctuating current through the transformer primary inducing a voltage therein which is increased in the secondary to a level adequate to excite the bulb. A voltage source 75 is connected through a switch 76 to the other side of the transformer primary 72 providing a current path through the primary 72. When the block 25 is in contact with the bristles 57 and switch 76 is closed there is a completed circuit from one side of the circuit, disposed on the wheel 10 to the voltage source 75 through the brush contact 28 of the instant invention. Current flow through primary 72 and the resultant excitation of bulb 74 ensue when and if the circuit on the wheel 10 is connected to ground, as will later be discussed.

The operation of the described embodiment of the present invention is believed to be clearly apparent and is summarized briefly at this point. The bracket 30 is first positioned in proper spaced relation to the rim 16 to provide periodic contact between block 25 and bristles 57 as the wheel 10 is rotated. The wire 38 extending from pin 35 below bracket 30 is connected to the circuit 70. The Pressure Monitoring Apparatus is adjusted to close the wheel circuit to ground at a desired pressure. The operator determines that the switch 76 is closed, thus providing electrical continuity between the grounded side of the voltage source 75 and the bristles 57. As the vehicle is moving the bristles intermittently contact block 25 providing intermittent continuity to the wheel circuit which is open until the tire pressure has dropped below the desired level.

In the event that tire pressure falls below the desired level, the detector 22 on the wheel 10 closes. Since the bristles 57 provide intermittent contact to the block 25, a completed circuit exists with every revolution of the wheel with a duration corresponding to the time for which contact is maintained between the bristles and the block. The intermittent continuity allows a transient current to flow through primary 72 inducing a voltage therein. The primary voltage is stepped up in the secondary 73 to a level adequate to excite bulb 74, which lights during the period of the transient current. Thus the neon bulb 74 is caused to flicker on and off with each wheel rotation as the bristles 57 contact rotating block 25 thus creating a highly visible signal for the operator. When the operator observes the flashing bulb he is alerted to take proper action as by stopping the vehicle and inspecting or replacing the tire.

The contact of the block 25 with the bristles 57 causes the bristles to flex in the direction of the rotation of wheel 10 and also to tighten spring 52. When the block 25 has rotated beyond the area of contact with the bristles the latter snap back into the ready position shown in FIG. 1. As best seen in FIG. 2, the block is concave to gather or bunch the bristles when engaged therewith. As indicated in FIG. 1, the concavity is arcuately elongated concentrically of the wheel. The stop 60 serves to limit the rearward travel of the clamp 55 and bristles 57. The resiliency inherent in the bristles and spring along with the action of the stop and the disposition of the bristles enable the bristles to maintain their original shape for a prolonged period and represents an improved method of making electrical contact with a rotating body. In actual operation, the contact has proved much more dependable and durable than those previously known for the purpose.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention.