Cooled motor for a paper shredder

A paper shredder motor cooling assembly having a paper shredder motor coupled to a fan shaft, an enclosure surrounding the paper shredder motor and having selected input and selected output vents to control airflow to the paper shredder motor, a fan coupled to the fan shaft, communicating with the selected input vents or the selected output vents; when the paper shredder motor is operating, the rotor shaft turns the fan to generate a differential air pressure between the selected input vents and the selected output vents, removing heat from the motor. A duty cycle of greater than 15 minutes is obtained. The fan can be coupled to the motor by speed increasing gearing, attached to the cutter blade assembly, such that the fan turns faster than the motor. The fan also can be attached to the motor shaft. An input fan and an output fan can be used.

BACKGROUND

1. Field of the Invention

The present invention relates to electric motors and more particularly to paper shredders having electric motors with cooling apparatus.

2. Background Art

Consumer product satisfaction is driven at a particular product price point by product safety, product reliability, and product longevity. This is particularly so in the field of consumer paper shredders, where a shredder can endure excessive or rough wear despite the non-industrial focus of the shredder product specifications. Such excessive or rough wear can, over time, degrade the reliability and longevity of the shredder product causing the consumer to become dissatisfied with the product. In some cases, repeated stresses on the moving parts of the shredder may cause part failure, leading to the expense of product repair or replacement, a further decrease in satisfaction, or even loss of goodwill for the respective consumer in the paper shredder brand. Even marginally stressful moments of operation may in the aggregate take their toll on the operating machinery of the shredder.

One shredder part which can be vulnerable to mechanical and thermal stresses is the shredder electric motor, which can arise from, for example, frequent starting, overloading, jamming, and continuous, beyond-rating use. Over time, the cumulative stresses faced by a shredder motor may lead to premature failure or poor performance. A common thread with these stressors is the heating effects of motor current (I2R losses). Many sophisticated electronic controllers have been devised to reduce the effects of I2R losses upon motors. Complex mechanical cooling systems have been advanced for large motors, as well. However, in the sphere of fractional-horsepower electric motors, as used in light- to medium-duty paper shredders, sophisticated electronic controllers and complex mechanical coolers can add prohibitive premiums to the motor cost, and to the cost to consumers, reducing a manufacturer's market share. An inexpensive but efficacious cooling apparatus for paper shredder motors is needed.

SUMMARY

The foregoing need is met by cooling apparatus and methods for a motor for a paper shredder. (To be filled in when Claims finalized)

DETAILED DESCRIPTION

Embodiments of the present invention can assist in reducing overheating in a motor. In particular, selected embodiments can be used as a forced-air cooled motor, as may be used without limitation, to power a home or office paper shredder.

FIG. 1illustrates an embodiment of a shredder motor cooling apparatus having shredder assembly100, including motor1, cooling fan2, overdrive gearing3, fan shaft4, fan tube5, first side plate8, second side plate11, and shredder gearing housing13. Perspective is that of first side plate8forward, with one of shredder gearing exposed through a slot in housing13. Motor1is disposed between first side plate8and second side plate11. Shredder gearing housing13is disposed over gears (seen in part) coupled to the shaft (not shown) of motor1, and is disposed on the outer side of second side plate11. Shredder gearing (not shown) is a reduction gearing, which also is coupled to shredder blade shaft (not shown). In assembly100, overdrive gearing, which also is speed increasing gearing,3is coupled to and motivated by the shredder blade shaft (not shown) and coupled to fan shaft4. Fan shaft4couples the shaft rotation through first side plate8to cooling fan2. Fan tube5may be fitted tightly to motor1end, which motor1end may have selected ventilation holes (not shown) to admit the cooling air. In operation, motor1operates shredder gearing (not shown), which is coupled to the shredder blade shaft (not shown). The shredder blade shaft (not shown) can be coupled to overdrive gearing3. Overdrive gearing3may be configured to turn shaft4and thus, cooling fan2, providing a rotation of between about 4,000 RPM to about 10,000 RPM. Such a high-speed rotation can create a forceful current of air by cooling fan2, which can be confined by fan tube5and directed to cool motor1. Such a fan configuration is capable of operating at a different speed from that of the motor1, increasing cooling of motor1at a high thermal efficiency. Indeed, the produced efficiency may provide a shredder motor duty cycle of greater than 50%.

Referring toFIG. 2, shredder blade shaft assembly can be seen to include first driver shaft7and shredder blade shaft6, both of which are motivated by shredder gearing12, which is partially seen through cover13. Shredder blades have been removed for clarity of presentation. Shredder blade shaft6can protrude through first side plate8and be coupled to overdrive gearing3. Motor1can be affixed to second side plate11and coupled to shredder gearing (partially shown through cover13). With fan tube5removed, selected tube vent holes may be seen in the end of the can. Cooling fan2can be a simple axial fan, for low cost. InFIG. 3, shaft bushings9(bearings) are illustrated on the outer side of first side plate8. Protective coverings are illustrated as being in place on the shredder blade assembly.

FIG. 4present an shredder assembly100from the vantage of second side plate11forward, with shredder gearing housing13removed and shredder gearing12shown exposed. Protective coverings conceal the shredder blades inFIG. 4. Fan bezel10can be seen on the inner side of first side plate8. Fan bezel10is sized to admit fan shaft4therethrough and may provide additional support to high revolution speed of cooling fan2.

FIG. 5is an embodiment of shredder assembly200with forced cooling by cooling fan2, without containment by fan tube5. The perspective is that of the first side plate8being forward. The operation and functionality ofFIGS. 1-4of shredder assembly100is substantially the same in shredder assembly200without confinement of the air current generated by cooling fan2within fan tube5.FIG. 6depicts shredder assembly200from the perspective of the second side plate11being forward and gearing housing13being in place.

Turning toFIG. 7, still another embodiment of the present invention is depicted. Motor700combined with cooling fans720,740is shown, in which each of cooling fans720,740can be enclosed within motor air chamber722,742, respectively. Motor700can be confined to a sealed can750, with limited paths for air flow with motor air chamber722,742, and creating a defined heat transfer path within motor700. Cooling fan720is disposed to be a forced air intake fan720coupled to the shaft705of motor700. Cooling fan740is disposed to be a forced air outlet fan740coupled to the shaft705of motor700. Fans720and740are positioned inline with motor rotor710. When power is applied to motor700, rotor710rotates relative to stator715to translate mechanical power on shaft705from applied electrical energy. Fan720insufflates air for cooling across motor700. Fan740extracts air for cooling across motor700. Either fan720, or fan740, or both, may be used. A portion of the mechanical power applied to shaft705is employed by fans720,740. Fans720,740tend to rotate at the speed of shaft705, for example at about 3700 RPM. In selected embodiments, motor700with inlet fan720and outlet fan740generate an energetic stream of air directed from intake vent724to outlet vent744, and through the region of rotor710and stator715, when energized. Sealed can750can include vent holes755,765disposed on outlet side724of intake fan720, and disposed on intake side744of outlet fan740, to provide directional flow of air. Such forced air flow can be effective in removing heat from rotor710and stator715, increasing the duty cycle of motor700to nearly an order of magnitude greater than ordinary paper shredder motors, for example, up to about 45 minutes. In selected configurations, only one fan assembly may be used. In some configurations, a type of centrifugal fan can produce large volumes of air because of a forced pressure differential across motor700from intake fan720to outlet fan740created by at least one of fans720,740and guided by selected flow holes755,765. A centrifugal fan may be used for fan720and fan740, although fans720,740are not confined to such configurations. In other configurations, an axial fan can be used. In yet other configurations, a vane-axial fan may be configured to produce an efficacious forced airflow by differential pressure. The heat removed from motor700is increased over present paper shredder motors due to the increased forced air mass flow rate passing by the motor elements. The configuration ofFIG. 7may be disposed within the interior of a paper shredder or in communication with the exterior of the paper shredder.

FIG. 8illustrates that effective cooling also may be obtained by using a single outlet fan820as a forced air outlet fan assembly for motor800. As before, shaft805of rotor810can provide the mechanical motive force for fan820, derived from the electromagnetic interaction of rotor810and stator815. Motor800can be confined to an enclosure, e.g., a sealed can,850with limited paths for air flow and for creating a defined air flow and a heat transfer path within motor800. Vent holes855,865can be disposed to direct forced air flow from air intake side811to air outlet side842. Vent holes855provide for input cooling air into motor800and manifold vent holes865provide for motor cooling air extraction into intake845of outlet fan800. Fan820can be enclosed within motor air chamber822, which can be communicatingly affixed to enclosure850to allow air flow through an end of the enclosure. A centrifugal fan in such embodiments also can produce large volumes of air because of a pressure differential across motor800, created by fan820and by guided vents, or flow holes855,865, from air intake side811at one end of the enclosure to air outlet side842at the other end of the enclosure. However, and axial fan also may be used. This configuration may be disposed within the interior of a paper shredder or in communication with the exterior of the paper shredder. The heat removed from motor800is increased over present paper shredder motors due to the increased forced air mass flow rate passing by the motor elements. NeitherFIG. 7norFIG. 8require a separate controller or power supply for the forced air fans due to their integration with the shaft of the motor rotor. As withFIG. 7, an axial or a centrifugal fan assembly may be used.

Turning toFIG. 9, a motor900, such as motor700, can be seen positioned in paper shredder housing970, having an air input duct975and an air output duct985disposed in housing970. Air input duct975can communicate with input vent holes955; air output duct can communicate with output vent holes960. In this configuration, the intake air manifold opening930is positioned on the exterior of shredder housing970, and communicates with air input duct975, preventing internal shredder debris from being drawn into motor900. Similarly, output air manifold opening945is disposed at the exterior of shredder housing970, and in communication with air output duct985, so that the forced air from900does not cause the creation of a debris cloud by exhausting air onto the shreddant (not shown), which may be in or near housing970. Air input duct975or air output duct985, or both, may be positioned such that human access to input fan920or output940is difficult. Screen972,973may be placed over one or both external openings930,945. In certain embodiments, motor900is disposed in the interior of shredder housing970, without direct communication with the exterior of shredder housing970. The heat removed from motor900is increased over present paper shredder motors due to the increased forced air mass flow rate passing by the motor elements. As withFIG. 1, an axial or a centrifugal fan assembly may be used.

InFIG. 10, a single-fan motor1000, similar to motor800, is shown in communication with exterior1008of paper shredder housing1010. Similar toFIG. 9, the input air flow and output air flow is routed through ducts1032,1044which are in communication with airflow manifold openings1030,1045. InFIG. 10, air is extracted from motor1000. It should be noted that forced air fan1040which, in the example ofFIG. 10, is disposed on the outlet side of airflow, may instead be disposed on the input side of airflow. In the latter configuration, the forced air fan may be positioned to insufflate air into the motor1000instead of extracting air from motor1000. In either case, a forced differential air pressure causes a large volume of air to be moved past motor1000. In still another embodiment, cooling fans may be located on the motor air input and the motor air output. The heat removed from motor1000is increased over present paper shredder motors due to the increased forced air mass flow rate passing by the motor elements. Air can be taken in through manifold opening1030and then through selected input vent holes1055. Air can be exhausted through selected output vent holes1065and out through manifold opening1045. As withFIG. 7orFIG. 8, an axial or a centrifugal fan assembly may be used.

The embodiments of the present invention disclosed herein are intended to be illustrative only, and are not intended to limit the scope of the invention. It should be understood by those skilled in the art that various modifications and adaptations of the prevent invention as well as alternative embodiments of the prevent invention may be contemplated or foreseeable. It is to be understood that the present invention is not limited to the sole embodiments described above, but encompasses any and all embodiments within the scope of the following claims.