Aligning and Protective Cover for a Motor

(1) Field of the Invention

This invention relates to an aligning and protective apparatus to be used with a motor like a stepping motor.

(2) Description of the Related Art

Some stepping motors utilize first and second sensors which cooperate with a timing disk which is secured to the output member of the motor. The first and second sensors are utilized to adjust the various lead angles which are associated with the operation of the stepping motor. When the first and second sensors are mounted separately, it is difficult to adjust the sensors so as to effect the appropriate lead angle for the motor. Another problem with the stepping motors is that the output member of the motor is very often a timing pulley which tends to generate a lot of dust particles from the associated timing belt. The dust particles tend to accumulate between the timing disk and the associated light sensors, making frequent cleaning necessary. The cleaning requires machine downtime and maintenance costs which could be expensive.

In contrast with the above, the present invention obviates the problems mentioned. The apparatus of this invention includes a housing in which the two sensors are mounted and accurately located relative to each other. The housing is placed within a cover and mounted on the stepping motor. The cover with the housing therein is mounted on the motor so that the cover with the sensors therein is rotated relative to the motor until the proper lead angle is obtained. Thereafter, the cover is locked against movement relative to the motor.

An advantage of this invention is that only one adjustment is required.

Another advantage is that the time for making the adjustment is greatly reduced compared to the prior art method.

Still another advantage is that the cover provides a multi-function element; it keeps dirt away from the timing disk associated with the motor and the two sensors, also facilitates the adjusting of the sensors.

In a first preferred embodiment of the invention, there is provided an aligning and protective apparatus (hereinafter referred to as apparatus) for a motor, said motor having:

a cylindrical housing and an end portion joining said cylindrical housing to form a circular rim,

an output member extending from said end portion; and

a timing member fixed to said output member to rotate therewith;

said apparatus comprising:

a sensor housing having at least one sensor therein to coact with said timing member when said sensor housing is positioned on said motor; and

a cover means for adjustably securing said sensor housing on said motor;

said cover means being generally circular in shape to cover an area of said end portion, an area of housing, and said circular rim; said cylindrical

said cover means having a receiving area therein to receive said sensor housing;

said cover means being discontinuous in one area thereof to enable said cover means to be expanded to facilitate mounting said cover means with said sensor housing therein on said motor; and

said cover means having locking means for adjustably locking said cover means on said motor after said cover means is rotated on said motor so as to position said sensor in said sensor housing in operative relationship with said timing member and said motor.

In a second embodiment of the invention, there is provided an apparatus comprising:

a stepping motor having a cylindrical housing and an end portion, with said end portion joining said cylindrical housing to form a circular rim;

an output member extending from said end portion;

a timing disk fixed to said output member to rotate therewith;

a sensor housing having first and second sensor pairs located therein and also having a flange member secured to said sensor housing to enable said first and second sensor pairs to coact with said

timing disk when said flange member is seated on said circular rim;

a cover means for adjustably securing said sensor housing on said motor;

said cover means being generally circular in shape to cover an area of said end portion, an area of said cylindrical housing, and said circular rim;

said cover means having a receiving area therein to receive said sensor housing;

said cover means being separated along a separation line in one area thereof to enable said cover means to be expanded to facilitate mounting said cover means with said sensor housing therein on said motor; and

said cover means having locking means for adjustably locking said cover means on said motor after said cover means is rotated on said motor so as to position said first and second sensors in said sensor housing in operative relationship with said timing disc and said motor.

These advantages, and others, will be more readily understood in connection with the following specification, claims, and drawing.

FIG. 1 is a general, perspective view of a stepping motor, showing its associated output member and timing disk, and also showing a sensor housing made according to this invention;

FIG. 2 is a view, similar to FIG. 1, showing a cover made according to this invention, and also showing the locking means to enable the sensors within the housing to be fixed relative to the motor;

FIG. 3 is a general perspective view, showing the sensor housing shown in FIG. 1;

FIG. 4 is a plan view, looking down on a portion of the apparatus shown in FIG. 1;

FIG. 5 is a cross-sectional view, taken along the line 5--5 of FIG. 4 to show additional details of the apparatus shown in FIG. 4; and

FIG. 6, shown on the sheet containing FIGS. 3 and 4, shows an enlarged view of a portion of the apparatus shown in the circle in FIG. 5.

FIG. 1 shows a typical stepping motor 10 which may receive the aligning and protective apparatus of this invention which is designated generally as apparatus 12 (FIG. 2). The motor 10 includes a mounting flange 14, an output shaft 16, and an additional output member, like the timing pulley 18 which is fixed to the output shaft 16 to rotate therewith. The timing pulley 18 drives a timing belt 20 which drives a device (not shown) as is done conventionally. The motor 10 also includes a timing disk 22 which includes a plurality of radially-aligned timing slots 24 which coact with sensors included in the sensor housing 26. The timing disk 22 is secured to a metal hub 23 (FIG. 5) which is secured to the output shaft 16.

The sensors included in the housing 26 are used to set the lead angles associated with the stepping motor 10. A useful definition of a stepping motor is that it "is a motor possessing the ability to rotate in either direction as well as start and stop at various mechanical rotational positions, and whose shaft (rotor) moves in precise angular increments for each excitation change or step." U.S. Pat. No. 4,710,690, which is assigned to the same assignee as is this application, discusses first and second sensors which are used in energizing a stepping motor. The present apparatus 12 facilitates aligning the first and second sensors so as to effect certain lead angles in the energization of the motor.

The first and second sensors alluded to are actually first and second sensor pairs 28 and 30 shown in dashed outline in FIG. 4. Sensor pair 28 includes a light emitter 28-1 and a light detector 28-2 which are shown in FIG. 5. The light emitter 28-1 has a spherical lens 28-11 formed therein to direct light at the light detector 28-2 positioned in opposed relation with the light emitter 28-1. The light detector 28-2 also has a spherical lens 28-22 formed therein to gather light from the light emitter 28-1. The sensor pair 30 is exactly the same as sensor pair 28. The light emitter 28-1 and the associated light detector 28-2 included in a sensor pair, like 28, may be reversed from the positions shown in FIG. 5 without affecting the operation of the apparatus 12.

The sensor housing 26 comprises a first body portion 26-1, a second body portion 26-2, and a joining portion 26-3 which are formed into a general "C" configuration as shown best in FIG. 3. The sensor housing 26 also includes a flange portion 32 which is used to mount the sensor housing 26 on the motor 10. In this regard, the motor 10 has a cylindrical housing 34 and an end portion 36 which joins the cylindrical housing 34 to form the circular rim 38. The flange portion 32 is generally "L" shaped, having a portion 40 to rest on the circular rim 38, with the flange portion also being arcuately shaped to receive a portion of the cylindrical housing 34 therein. The light emitters 28-1 and 30-1 of the first and second sensor pairs 28 and 30 are located in the first body portion 26-1, and correspondingly, the light detectors 28-2 and 30-2 are located in the second body portion 26-2. The first and second body portions 26-1 and 26-2 are spaced apart as shown best in FIG. 1, for example, to receive the timing disc 22 therebetween.

The sensor housing 26 also has an insert 42 which provides a strain relief for the wires associated with the sensor pairs 28 and 30, and the insert 42 also has a pair of slits associated with each of the sensor pairs 28 and 30. The insert 42 has a general "C" section formed by plates 42-1 and 42-2 which are positioned in opposed relation as shown best in FIG. 5. A pair of slits includes the slit 44-1 located in the plate 42-1 and also includes the slit 44-2 located in plate 42-2, as shown best in FIG. 5. The slits 44-1 and 44-2 are accurately located in vertical alignment in the insert 42, with the associated spherical lens 28-11 being aligned with the slit 44-1 and with the spherical lens 28-22 being aligned with the slit 44-2. There are similar slits associated with the second sensor pair 30, with only the slit 46-1 being shown in FIG. 4. The insert 42 is made of opaque plastic so that the slits mentioned, like 44-1 for example, permit light to pass therethrough: In the embodiment described, the slits, like 44-1 and 46-1, are spaced apart a distance of 5.25 mm on a line which is perpendicular to a radial line of the cylindrical housing 34, with the width of the slits, like 44-1, being 0.25 mm. Naturally, these dimensions are just exemplary for a stepping motor which has a diameter of about 5.64 cm and which has 200 stator poles, for example.

The insert 42 also has a detent 50 which coacts with a recess 52 (FIG. 6) in the housing 26 to conventionally, detachably retain the insert 42 within the housing 26. The housing 26 is a clear plastic member which surrounds the insert 42 as shown in Fig. 5. The housing 26 keeps dust from clogging the slits, like 44-1, in the insert 42, and it also keeps dust from accumulating on the timing disk 22.

To assemble the elements of the sensor housing 26, the wires 54 (FIG. 3) associated with the sensor pairs 28 and 30 are threaded through the openings, like 56 and 58 in FIG. 5, and then the sensor pairs 28 and 30 are positioned on the insert 42. The insert 42 is then pushed into the sensor housing 26 until the detent 50 (FIG. 6) engages the recess 52. The sensor housing is then ready to be installed in the aligning and protective cover hereinafter referred to as cover 60, shown in perspective in FIG. 2.

The cover 60 is generally circular in shape, and it is designed to cover a portion of the end portion 36, a portion of the cylindrical housing 34, and the corner rim 38 of the motor 10 as shown best in FIG. 2. The cover 60 has a cut line, shown as dashed line 62, to enable the cover to be expanded to facilitate mounting the entire apparatus 12 on the motor 10. There is an "L" shaped member 64 which is secured to the cover 60 on one side of the cut line 62; its function is to prevent dust from getting on the timing disk 22 via the cut line 62.

The cover 60 also has a receiving area 60-1 (FIG. 2) therein which is used to house the sensor housing 26 and to maintain the sensor housing in a fixed position on the motor 10 after it is properly aligned thereon as will be described hereinafter. The receiving area 60-1 is generally rectangular in shape and conforms to the external shape of the sensor housing 26 so as to maintain it in a fixed position on the motor 10 when the cover 60 is locked thereon.

The locking means for locking the cover 60 on the motor 10 includes the first and second flange portions 66 and 68 which extend from the cover as shown in FIG. 2. The flange portions 66 and 68 have reinforcing portions, like 66-1, to enable the internal diameter of the cover 60 to be enlarged somewhat by moving the flange portions 66 and 68 away from each other. This movement enables the cover 60 to accommodate the sensor housing 26 when this housing is positioned on the motor 10. The locking means also includes the fastener 72 and a threaded metal insert 74, which, when tightened, are used to lock the cover 60 in place on the motor 10. The threaded metal insert 74 is conventionally, ultrasonically bonded in the plastic cover 60 to keep the insert 74 stationary while the fastener is rotated to lock the cover 60 in place.

The apparatus 12 is installed in the following manner. After the sensor pairs 28 and 30 are installed in the sensor housing 26 as previously described, the sensor housing 26 is placed on the motor 10 as shown in FIG. 1. The timing disk 22 is positioned between the first and second body portions 26-1 and 26-2, with the flange portion 32 resting on the corner rim 38. The aligning cover 60 is then expanded somewhat by pushing the flange portions 66 and 68 apart. While so expanded, the cover 60 is placed over the motor 10, with the receiving area 60-1 aligned with the sensor housing 26, and thereafter, the cover 60 is moved downwardly (as viewed in FIG. 1) to enable the sensor housing 26 to be embraced in the receiving area 60-1. The side of the cover 60 which is opposite to the receiving area 60-1 is then lowered on the motor 10, and thereafter, the flange portions 66 and 68 are released, permitting the cover 60 to wrap around the motor 10. The fastener 72 and metal insert 74 are then tightened somewhat to enable the cover 60 to snugly fit the motor 10, while permitting the whole apparatus 12 to be rotated somewhat on the motor 10.

The apparatus 12 is aligned in the following manner. The wires 54 coming from the sensor housing 26 are fed into the controller 75 which also has a test routine or circuit 76 (Fig. 2) included therein. In the embodiment described, the lead angle for the stepping motor 10 is varied by changing the locations of the first and second sensor pairs 28 and 30 within the sensor housing 26 relative to the stators (not shown) within the cylindrical housing 34. The test circuit 76 operates by giving a visual indication when the sensor pairs 28 and 30 are properly positioned to effect the desired lead angle. When this occurs, a predetermined number of lights 78 are energized by the test circuit 76. The test operator then tightens the fastener 72 to fix the apparatus 12 on the motor 10. Because the test circuit 76 is not a part of this invention, it need not be described in any further detail.