Labyrinth seal for a motor-fan unit

A labyrinth seal for a bypass discharge-type motor-fan unit includes a motor unit from which extends a rotating shaft that passes through an aperture in an end plate to drive a fan unit. Disposed within the aperture is a labyrinth seal configured to prevent liquid entrained in a working airflow from entering the motor unit. The rotating shaft also includes a vacuum bore, such that the negative pressure generated by the operation of the fan unit draws any liquid out of an evacuation zone maintained between the motor unit and the end plate. As such, the components of the motor unit are protected from being exposed to the liquid, thereby extending the operating life motor-fan unit.

TECHNICAL FIELD

The present invention is generally directed to a seal for use with a rotating shaft of a motor-fan unit. Particularly, the present invention relates to a labyrinth seal for a rotating shaft of a motor-fan unit which prevents liquid from penetrating therethrough. More particularly, the present invention relates to a vacuum bore maintained by the rotating shaft of the motor-fan unit that is configured to evacuate moisture that accumulates in an evacuation zone.

BACKGROUND ART

Electric motors are well known in the art and have been placed into use in a variety of applications, including the handling of air. In this circumstance, an electric motor is coupled to a fan by a rotating shaft, creating a motor-fan unit, which produces a flow of air as needed. For example, the motor-fan unit may be used to generate working air for vacuum-type devices, such as vacuum cleaners, utility vacuums, as well as other devices that operate in environments that are dry, or that have varying degrees of moisture. One particular type of motor-fan unit is referred to as a bypass discharge-type motor-fan unit and operates such that working air is moved by the fan unit to create a vacuum that draws debris and liquid entrained air into the fan unit, while a separate cooling fan pulls cooling air into the motor unit to keep it cooled. Due to this operation, bypass discharge-type motor-fan units are configured such that the motor unit receiving the cooling air is separated from the fan unit generating the working air by a plate or other partition. This plate or partition provides an aperture or other interface to allow the shaft maintained by the motor unit to extend therethrough so as to rotate the fan. Unfortunately, during operation of the motor-fan unit, the liquid entrained in the working air tends to penetrate the area of the partition through which the shaft extends. As a result, water, detergents, and other liquid is permitted to come in contact with one or more bearings that carry the rotating shaft of the motor unit, causing it to become degreased, which may contribute to the premature failure of the motor unit. In addition, liquid and debris that penetrates into the region of the motor unit may cause the electrical components of the system to be damaged, causing the motor unit to fail.

In response to this problem, techniques have been developed, which utilize various arrangements of seals to prevent liquid and other debris from entering the motor unit around the portion of the shaft that extends through the partition. However, such techniques are inefficient, and do not provide a commercially acceptable level of performance. For example, air seals have been used in the past to provide a seal about the portion of the shaft of the motor unit that extends into the fan unit. These air seals generate a vacuum to evacuate liquid that has penetrated into the vicinity of the air seal. Unfortunately, such air seals generate an insufficient amount of vacuum pressure, and thus are generally ineffective in thoroughly evacuating liquid and moisture from about the shaft carrying bearing and the electrical components maintained by the motor.

Therefore, there is a need in the art for a bypass discharge-type motor-fan unit that utilizes a labyrinth seal that is disposed about a rotating shaft of the motor unit to prevent liquid from penetrating through the fan unit and into the motor unit. In addition, there is a need for a bypass discharge-type motor-fan unit that maintains a rotating shaft that includes a vacuum bore to evacuate liquid that enters an evacuation zone. Furthermore, there is a need for a bypass discharge-type motor-fan unit that rotates a fan via a shaft to generate a negative-pressure region proximate a vacuum bore maintained by the shaft so that liquid that has entered an evacuation zone can be evacuated by the vacuum generated within the vacuum bore.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide a labyrinth seal for a motor-fan unit.

Another aspect of the present invention to provide a motor-fan unit comprising an end plate having an aperture therethrough, a motor unit attached to the end plate and defining an evacuation zone therebetween, the motor unit having a rotating shaft which has a shaft end that is received through the aperture, the shaft maintaining a vacuum bore extending from an outlet port disposed proximate the shaft end to a vacuum port disposed upon an outer surface of the shaft located proximate the evacuation zone, wherein liquid collected within the evacuation zone is discharged through the vacuum bore, a fan unit attached to the shaft end, the fan generating a negative pressure about the outlet port when moved, and a labyrinth seal disposed within the aperture, the labyrinth seal maintaining a seal about the shaft, so as to prevent the intrusion of liquid through the end plate.

Still another aspect of the present invention is to provide a motor-fan unit comprising an end plate having an aperture disposed therethrough, a motor unit attached to the end plate, the motor unit having a rotating shaft which has a shaft end that is received by the aperture, a labyrinth seal disposed within the aperture, the labyrinth seal maintaining a seal about the shaft so as to prevent the intrusion of liquid through the end plate, and a fan attached to the end of the shaft.

Yet another aspect of the present invention is to provide a motor-fan unit comprising an end plate having an aperture therethrough, a motor unit attached to the end plate and defining an evacuation zone therebetween, the motor unit having a rotating shaft which has a shaft end that is received through the aperture, the shaft maintaining a vacuum bore extending from an outlet port disposed proximate the shaft end to a vacuum port disposed upon an outer surface of the shaft located proximate the evacuation zone, wherein liquid collected within the evacuation zone is discharged through the vacuum bore, and a fan unit attached to the shaft end, the fan generating a negative pressure about the shaft end when moved.

Still another aspect of the present invention is to provide a method for forming a labyrinth seal for a motor-fan unit comprising providing a motor unit having a rotating shaft that extends through an end plate attached to the motor unit, the shaft moving a fan attached thereto, attaching a engagement seal to the end plate, placing a spacer upon the fabric seal, such that an outer wall extending from an inner surface of the spacer is adjacent the fabric seal, applying pressure to the spacer, and rotating the spacer so as to form a groove in the fabric seal, so as to form a labyrinth seal about the shaft.

BEST MODE FOR CARRYING OUT THE INVENTION

A bypass discharge-type electric motor-fan unit in accordance with the concepts of the present invention is generally referred to by the numeral10, as shown inFIG. 1of the drawings. The motor-fan unit10includes a motor unit12and a fan unit14that are separated by an end plate16. The motor unit12maintains a shaft20that is rotatably supported at each end by bearings22,24, and which passes through a labyrinth seal30maintained by the end plate16.

The labyrinth seal30serves to impede the penetration of liquid or moisture into an evacuation zone40that is defined as the region between the motor unit12and the endplate16. For the purposes of the following discussion, it should be appreciated that the term “liquid” also includes any liquefied material, including moisture, liquefied debris, and liquids that carry solid debris. In addition, the shaft20maintains a vacuum bore42that fluidly connects a vacuum port44disposed on the outer surface of the shaft20with an outlet port46disposed at the end of the shaft20that is proximate the fan unit14. Any liquid that penetrates through the labyrinth seal30, or otherwise enters the evacuation zone40is evacuated therefrom by the negative pressure, or vacuum, generated within the vacuum bore42by the operation of the fan unit14. As such, the labyrinth seal30and the vacuum bore42prevent any liquid or debris from accumulating in and about the region of the bearing22that is proximate the fan unit14. Such operation prevents the bearing22from being degreased, thereby extending the operating life of the motor-fan unit10, while liquid is prevented from corroding or otherwise harming the components of the motor unit12. Furthermore, while the operation of the labyrinth seal30and the vacuum bore42complement each other when used together, it is contemplated that either of the labyrinth seal30or vacuum bore42may be used independently in connection with the motor-fan unit10. With the general aspects of the present invention set forth, the discussion that follows will present components of the motor-fan unit10and that of the labyrinth seal30and the vacuum bore42.

Continuing with reference toFIGS. 1-2A, the motor unit12includes an armature100that is rotatably disposed within a fixed lamination stack102. Although not shown in detail, skilled artisans will appreciate that respective windings are separately wrapped around the armature and the lamination stack. The armature100is carried by the shaft20that is rotatably supported at each end120and122by respective support bearings22and24. The armature100carries a commutator124that is configured to receive electrical current from a pair of brushes which are not shown in detail. The bearing24is retained in a bearing retainer142that is maintained by a support bracket143that is attached proximate end122of the shaft20by a pair of suitable threaded fasteners. For example, threaded fasteners144and146connect the support bracket143to a motor bracket160. Indeed, bracket160provides corresponding threaded bores148and150to receive fasteners144and146. It should be appreciated that the support bracket143and the motor bracket160may be formed from any suitable material, including but not limited to steel, aluminum, and/or plastic. In addition, the motor bracket160maintains an aperture170through which the shaft20is received. Disposed about the aperture170is a bearing mount172which retains bearing22therein. As such, the motor bracket160provides a point of attachment for the motor unit12via the mounting bores148,150. The bracket160also serves as an interface for attaching the motor unit12to the end plate16, by using a frictional fit or any suitable fastener, such as screws, rivets, adhesive, and the like. However, it should be appreciated that in lieu of the motor bracket160, the motor unit12may be directly attached to the end plate16using known techniques.

During operation of the motor unit12, electrical current is supplied to the commutator124via the brushes, causing the armature100to rotate so as to apply a driving force to a fan within the fan assembly14. In addition to rotating the fan, which will be discussed in detail below, the shaft20may also rotate a cooling fan190, which is mounted at a point on the shaft20that is between the motor bracket160and the end plate16. The cooling fan190serves to generate a cooling airflow for the commutator124, brushes, as well as the other components of the motor unit12to prevent overheating and thermal wear.

The end plate16comprises an inner surface200that is disposed proximate the motor unit12, and an opposing outer surface202, disposed proximate the fan unit14. Disposed through the endplate16is an aperture204, which is substantially coaxial with the aperture170of the motor bracket160, and which is oriented to receive the shaft20therethrough. It should be appreciated that the aperture204is dimensioned so that there is a gap206, best seen inFIG. 2A, maintained between the shaft20and the perimeter of the aperture204. In addition, disposed upon the outer surface202is a substantially square counterbore210, although the counterbore210may be dimensioned to take on any desired shape. Disposed between the end plate16and the fan unit14is the labyrinth seal30, which includes an engagement seal220and a spacer222.

The engagement seal220, as shown inFIGS. 3A-Bis substantially square-shaped, although any other suitable shape may be utilized that substantially matches the shape of the counterbore210, and is formed from polytetrafluoroethylene (PTFE) material, such as TEFLON®. In particular, the engagement seal220maintains an attachment surface230that is opposite a receiving surface240, wherein the attachment surface230maintains a suitable adhesive for retaining the engagement seal220within the counterbore210of the end plate16. In addition, the engagement seal220maintains an aperture250through which the shaft20is received. However, it should be appreciated that the aperture250is dimensioned so that gap260, best seen inFIG. 2A, is maintained between the shaft20and the perimeter of the aperture250.

To complete the labyrinth seal30, the spacer222, as shown inFIGS. 4A-B, is utilized. The spacer222, which includes an aperture310, is formed of powdered metal, although other suitable materials may be used including: aluminum, steel, and/or plastic. In addition to maintaining an aperture310therethrough, the spacer222is substantially cylindrical in shape and maintains an inner surface320that is opposite an outer surface330. In addition, the outer dimension of the spacer222is defined by an outer edge340, while the aperture310is defined by an inner edge350. Extending at a substantially right angle from inner surface320of the spacer222about the outer edge340is an outer wall360, while an inner wall370extends at a substantially right angle from the inner surface320of the spacer222. In particular, the inner wall370is dimensioned to engage a ledge or step surface380maintained by the shaft20so as to be rotatably carried thereby, while the outer wall360of the spacer222is dimensioned to penetrate into, or otherwise engage the receiving surface240of the engagement seal220. Alternatively, the spacer222may be configured such that it does not engage the ledge380, but is affixed to the shaft20in any suitable manner so as to be rotatably carried thereby.

In one aspect, to ensure that the outer wall360of the spacer222thoroughly engages the engagement seal220, a “cutting” process is implemented, whereby sufficient force is applied to the spacer222so that the outer wall360fully engages the receiving surface240of the engagement seal220. Once engaged, the shaft20is rotated causing the spacer222to rotate thereby creating a groove384to be “cut” or otherwise formed in the engagement seal220, as shown inFIG. 2A. To facilitate the “cutting” process, and reduce the possibility of tearing the engagement seal220, the spacer222may be impregnated or otherwise treated with oil or other suitable lubricant. In one aspect, the use of powdered metal to form the spacer222facilitates its ability to retain lubricants, such as oil, and thus is beneficial for use in the operation of the labyrinth seal30. It should be appreciated that the dimension of the outer and inner walls360,370are selected so that a gap386is maintained between the engagement seal220and the spacer222when they are engaged with each other.

To facilitate the movement of working air, the end plate16also maintains an intake port390, which directs or otherwise routes working air generated by the fan unit14to a discharge port392where the air is exhausted from the motor-fan unit10. Furthermore, it should be appreciated that the end plate16may be formed of plastic, steel, aluminum or any other suitable material.

The fan unit14comprises a fan400having a base end410that is opposite a tapered end420through which a fan intake430is disposed therethrough. The base end410and the tapered end420are separated by vanes which form a plurality of voids432or open regions. Further, the base end410maintains an inner surface440that is opposite an outer surface450through which is disposed an aperture460that is dimensioned to receive the shaft20. The shaft20extends through the aperture460such that the end120of the shaft20is disposed within the void432. The fan400is attached to the shaft20via a washer470and a suitable fastener, such as a nut480that is threadably attached the end120of the shaft20. In addition to retaining the fan400to the shaft20, the nut480also serves to ensure that the inner surface440of the fan400applies a suitable amount of force to the spacer222so that it is both carried by the shaft20and is urged against the engagement seal220during the operation of the motor-fan unit10.

Covering the outside of the fan400is a shroud500that is attached to the end plate16using any suitable means, such as a friction fit for example. The shroud500includes an intake port510that is substantially aligned with the fan intake430that opens into the void432. The intake port510allows the fan400to generate a working airflow that forms a region of negative pressure or a vacuum about the end120of the shaft20that extends within the void432. Thus, as the fan400is rotated by the shaft20, the outer wall360of the spacer222rotates within the groove384maintained by the engagement seal220, thus enabling the labyrinth seal30to resist the intrusion of any liquid entrained in the working airflow from entering the motor unit12.

However, in the event that liquid is able to penetrate through the labyrinth seal30, it is permitted to collect in and about the evacuation zone40. Once collected in the evacuation zone40, the liquid is evacuated therefrom by operation of the vacuum bore42that is substantially coaxial with the shaft20. Specifically, the vacuum bore42is fluidly coupled at each end by the vacuum port44and an outlet port46. In particular, the vacuum port44is disposed upon an outer surface600of the shaft20at a point that is within the aperture204maintained by the end plate16. However, it should be appreciated that the vacuum port44may be located at any point on the outer surface600of the shaft20that is between the cooling fan190and the aperture250maintained by the engagement seal220. Furthermore, the vacuum port44may extend from the vacuum bore42to the outer surface of the shaft20at a substantially right angle, although any suitable angle may be utilized. In one aspect, the vacuum port42maybe comprised of one or more apertures disposed about the outer surface600of the shaft120. The outlet port46is disposed at the end120of the shaft20that is maintained within the void432of the fan400. It should be appreciated that the outlet port46may be comprised of one or more apertures disposed about the end120of the shaft20. Alternatively, the output port46may be disposed about the outer surface600of the shaft20proximate the end120. Thus, as the motor unit12rotates the fan400by the shaft20, a negative pressure is generated in the region about the outlet port46. This negative pressure region serves to create a vacuum within the vacuum bore42, thereby resulting in any liquid that has accumulated within the evacuation zone40being drawn into the vacuum bore42via the vacuum port44. Once within the vacuum bore42, the liquid is discharged into the void432via the outlet port46, where it combines with the working airflow generated by the fan400.

Thus, liquid that penetrates through the labyrinth seal30, during operation of the motor-fan unit10is collected within the evacuation zone40. As the shaft20rotates the fan400, negative pressure, or a vacuum, is generated in the region of the outlet port46. This negative air pressure causes the liquid anywhere within the evacuation zone40to be drawn from the vacuum port44and through the vacuum bore42, where it is discharged back into the void432via the outlet port46. Therefore, because liquid is contained and evacuated from the evacuation zone40, it does not accumulate, and, as such, it is prevented from coming into contact with the bearing22. This prevents the bearing22from becoming degreased and prevents the corrosion of any of the other components of the motor unit12, thereby extending the operating life of the motor unit12. It should be appreciated that the operation of the cooling fan190also serves as an additional barrier to liquid that may enter the evacuation zone40. That is, liquid entering the evacuation zone40tends to be deflected away from the bearing22and other components of the motor unit12by the movement of the cooling fan190.

It will therefore be appreciated that one advantage of one or more embodiments of the present invention is that a bypass discharge-type motor-fan unit utilizes a labyrinth seal to prevent the intrusion of liquid entrained in a working airflow from entering the motor unit. Another advantage of the present invention is that the shaft of the motor-fan unit includes a vacuum bore that maintains a negative pressure therein, such that liquid collected in an evacuation zone is evacuated therefrom to prevent the premature wear of the components of the motor unit.

Thus, it can be seen that the objects of the invention have been satisfied by the structure and presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.