Gap Adjusting Sensor

Technical Field

This invention relates generally to electronic sensors for determining the velocity, angular position, or direction of motion of a driven element and more particularly to an apparatus for adjusting the gap between the electronic sensor and the driven element.

Background Art

Electronic sensors for determining the velocity, angular position, or direction of motion of a driven element, such as a gear, are well-known in the art, as evidenced by patents 4,045,738 issued to Buzzell on September 8, 1977; 4,262,251 issued to Fujishiro et al. on April 14, 1981, and 4,331,917 issued to Render on May 25, 1982. Each of these patents employs a similar sensing device for producing a pulse train representative of the gear teeth moving past the sensor. Consequently, each of the three, and furthermore, all similar sensors, suffer from an inherent disadvantage. All of the sensors rely on a change in flux density induced by the gear teeth, this change in flux density is influenced greatly by the air gap present between the gear tooth and the sensor. It is, therefore, necessary to minimize the air gap to

_* obtain a pulse train of a sufficient magnitude. None of the prior art addresses the problem of obtaining a minimum air gap in a variety of different applications without the use of either shims or customized sensor bodies and all require very exacting torques, making assembly a difficult and error prone procedure.

The present invention is directed to over¬ coming one or more of the problems as set forth above.

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Disclosure of the Invention

In accordance with one aspect of the present invention a sensing apparatus, adapted for mounting adjacent a moveable element, has an electronic sensor and means for adjusting the position of the electronic sensor relative to the moveable member in response to contact of the sensing apparatus with the moveable member.

The prior art makes no attempt to provide a generic sensor body responsive to different air gaps present in different applications. The present invention directs itself to providing a single sensor functional in a wide variety of applications by adjusting the position of the electronic sensor in response to contacting the moveable member. The mounting of the sensing apparatus is also greatly simplified, thereby reducing the probability of error during assembly.

Brief Description of the Drawings

FIG. 1 is a schematic drawing of a first embodiment of the sensing apparatus; and

FIG. 2 is a schematic drawing of a second embodiment of the sensing apparatus.

Best Mode For Carrying Out the Invention

Referring to FIG. 1, a sensing apparatus 10, adapted for mounting adjacent a moveable element 24, has a first body 12 and an electronic sensor 18. The first body 12 additionally has an opening 20 and an opening inner surface 22. A plunger element 14 associated with the electronic sensor 18 is adapted for positioning and moving within the opening 20 of the first body 12. The plunger element 14 is moveable to a preselected location relative to the moveable element

24 in response to contacting the moveable element 24. Holding means 16 is provided for maintaining the plunger element 14 at this preselected location. By compressing the holding means 16 the plunger element 14 can be inserted into the opening 20 of the body 12. The holding means 16 will expand, thus contacting the opening inner surface 22 and the plunger element 14, thereby acting as a frictional device to prevent undesirable movement of the plunger element 14. The holding means 16 maintains the position of the plunger element 14 until a force adequate to overcome the frictional coefficient of the holding means 16 is applied to the plunger element 14. The frictional coefficient should be sufficient to prevent undesirable movement of the plunger element 14 caused by vibrational forces experienced in the most severe applications. This application shows two embodiments of the holding means 16. Fig. 1 shows a pair of conventional coiled springs 26 radially disposed about the plunger element 14 and Fig. 2 shows a hollow cylindrical body with a flanged portion 42 adjacent one end and slots extending the length of the cylinder. This device shall be referred to as a segmented spring 30 and provides a frictional force by the flanged portion 42 contacting the opening inner surface 22 of the first body 12. It is readily apparent that a number of well-known frictional devices could be substituted for those disclosed here without departing from the spirit of the invention. Means 36 for mounting the first body 12 and positioning the plunger element 14 within the pathway of the moveable element 24 is shown to be a threaded portion of the body 12, but it is recognized by those skilled in the art that any means for mounting the apparatus 10 (i.e., press fit, weld, etc.) would be considered equivalent.

The plunger element 14 consists essentially of a hollow cylindrical body formed from any of a variety of materials, preferably organic plastic. The body is hollow to accept the electronic sensor 18 within the plunger element 14 adjacent a first end 25 nearest the moveable element 24. In this embodiment of the invention, the electronic sensor 18 is a Hall effect device 28, but the invention is not directed toward the type of electronic sensor 18 and any type of sensor capable of detecting speed, direction, or angle of motion could be readily substituted for the Hall effect device 28 shown here and not depart from the scope of the intended invention. The first end 25 includes a flanged portion 40 acting as a means 32 for returning the adjustable means 38 to a first original position by urging the flanged portion 40.

Industrial Applicability

At the time the sensing apparatus 10 is to be installed, the plunger element 14 should extend at least a sufficient distance to contact the gear 34 when the apparatus 10 is fully installed. This is easily accomplished by applying a force on the flanged portion 40 of the plunger element 14. As the body 12 is threaded into its mounting, the plunger element 14 will contact the gear 34 and be forced further into the opening 20. Installation of the apparatus 10 is complete once the body 12 has been adequately tightened to prevent loosening during severe vibratory periods. The mechanics of installing the sensing apparatus 10 are essentially complete and positioning of the electronic sensor 18 to obtain a minimum air gap is automatically accomplished during normal operation. During the initial operating period, motion of the gear 34 causes contact between the plunger element 14 and the gear 34 resulting in the plunger element 14

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being forced into the opening 20 of the sensor body 12 to a preselected position. In this way the air gap between the plunger element ,14 and the gear 34 is equal to the run out of the gear 34 which is the minimum attainable air gap. The holding means 16 will continue to hold the plunger element 14 at this preselected or minimum air gap position under the most severe applications.

If at any time it becomes necessary to remove the sensing apparatus 10, reinstalling the device is easily accomplished even under adverse field conditions. The same minimum air gap can be obtained by prying on the flanged portion 40 of the plunger element 14 to restore the plunger element 14 to the extended position and then reinserting the apparatus 10 into its mounting. The minimum air gap is once again established during normal operation.

As evidenced by the preceeding description, the sensing apparatus 10 provides a desirable function lacking in the prior art. The ability to obtain a minimum air gap from a single generic sensor body is economically advantageous as well as important in that it greatly simplifies installation of the apparatus 10 and reduces the waste of materials, labor, and time. Other aspects, objectives and advantages of

^" this invention can be obtained from a study of the drawings, the disclosure, and the appended claims.

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