Anchoring system for injection molded magnets on a flux ring or motor housing

A power tool includes a flux ring with an annular member. At least one molded magnet is received on the annular member. An anchor is on the annular member to retain the at least one magnet on the annular member. The anchor is unitarily formed with the annular member to receive the magnet. The anchor includes at least one bend with a reinforcement member at the at least one bend.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to power tools and, more particularly, to motors for power tool flux rings with anchors to retain molded magnets on the flux ring.

In motor construction, the motor magnets must be retained on the housing or separate flux ring within the housing. Ordinarily, these magnets have been glued or adhered to the metallic ring or housing. In adhering the magnets to the metallic surface so that the magnets do not shift during use, various types of adhesives have been used. While some of the adhesives have been satisfactory, some adhesives work better than others. As the adhesives age, it is possible that if the power tool is dropped, that the sudden shock will destroy the bond between the magnet and the housing or ring, enabling the magnet to travel within the motor. When this occurs, the motor ceases to function. Thus, it would be desirable to provide a mechanism to retain the magnets in position on the ring or housing.

The present invention provides the art with a mechanism to retain magnets onto a flux ring or motor housing. Due to the advent of molded magnets, it is possible to provide an anchor in the flux ring or housing to retain the molded material on the ring or housing. One such anchoring member is an aperture having a counter-sink on the exterior of the ring or housing. Thus, when the magnet is molded onto the ring, the magnetic material that passes through the ring into the counter-sink forms a solid rivet-shaped fastener. Also, anchors may be stamped out of the ring or housing and project into the interior of the ring to receive the molded magnetic material. The anchors include gussets to reinforce the bend points to enhance the strength of the anchors and help resist deformation during molding. Due to the anchors being unitarily formed or stamped from the ring or housing, an aperture is left in the ring or housing after stamping, which is likewise filled with the molded magnetic material.

In accordance with a first aspect of the invention, a flux ring comprises an annular housing. At least one molded magnet is received on the housing. An anchor on the housing retains the at least one magnet on the annular housing. The anchor is unitarily formed with the housing. The anchor includes at least one bend. A reinforcement member is positioned at the bend to strengthen the anchor. The annular housing is metal with the anchor projecting radially from the housing. The projecting anchor has an aperture immediate the anchor on the housing. Thus, the magnetic material molds around the anchor and into the aperture. The anchor may have several different shapes. Preferably, the anchor has a rectangular shape, with one or both ends connected to the housing. Also, the anchor may have an L- or T-shape with one end connected to the housing.

In accordance with a second aspect of the invention, a motor comprises a stator assembly with the stator assembly including a flux ring. The flux ring comprises an annular housing. At least one molded magnet is received on the housing. An anchor on the housing retains the at least one magnet on the annular housing. The anchor is unitarily formed with the housing. The anchor includes at least one bend. A reinforcement member is positioned at the bend to strengthen the anchor. The annular housing is metal with the anchor projecting radially inward from the housing. The projecting anchor has an aperture immediate the anchor on the housing. Thus, the magnet molds around the anchor and into the aperture. The anchor may have several different shapes. Preferably, the anchor has a rectangular shape, with one or both ends connected to the housing. Also, the anchor may have an L- or T-shape with one end connected to the housing. Also, the motor comprises an armature rotatable within the stator assembly. A commutator is rotatable with the armature and connected to the armature via a shaft. A brush assembly is associated with the commutator.

In accordance with a third aspect of the invention, a power tool comprises a housing with a motor in the housing. The motor comprises a stator assembly with the stator assembly including a flux ring. The flux ring comprises an annular housing. At least one molded magnet is received on the housing. An anchor on the housing retains the at least one magnet on the annular housing. The anchor is unitarily formed with the housing. The anchor includes at least one bend. A reinforcement member is positioned at the bend to strengthen the anchor. The annular housing is metal with the anchor projecting radially inward from the housing. The projecting anchor has an aperture immediate the anchor on the housing. Thus, the magnet molds around the anchor and into the aperture. The anchor may have several different shapes. Preferably, the anchor has a rectangular shape, with one or both ends connected to the housing. Also, the anchor may have an L- or T-shape with one end connected to the housing. Further, the anchor may have a truncated cone shape with an axial aperture through the cone. Also, the motor comprises an armature rotatable within the stator assembly. A commutator is rotatable with the armature and connected to the armature via a shaft. A brush assembly is associated with the commutator. Also, the power tool includes an output member coupled with the motor shaft. An actuator member is electrically coupled between the motor and the power source to energize and de-energize the motor. In turn, when the motor is energized, the output member rotates.

Additional objects and advantages of the present invention will become apparent from the detailed description of the preferred embodiment, and the appended claims and accompanying drawings, or may be learned by practice of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning toFIG. 1, a power tool in accordance with the present invention is illustrated and designated with the reference numeral10. The power tool10is illustrated as a drill; however, any type of power tool such as a screwdriver, sander, rotary tool, clippers, saw or the like which utilize an electric motor may be used with the motor of the present invention. The power tool10includes a housing12which surrounds a motor14. An activation member16is coupled with the motor14as well as with a power source18. The power source18may be a power cord (AC current) or the power tool may have a battery (DC current) as shown. The motor14is coupled with an output20which may include a transmission22and a chuck24to retain a tool (not shown) with the drill.

The motor14includes a stator assembly30which includes a housing32, flux ring34, and magnets36and38. An armature40includes a shaft42, a rotor44with laminations46and windings48, as well as a commutator50coupled with the shaft42. The motor also includes end plates52and54. End plate52includes a bearing56which balances one end of the shaft58which is coupled with a pinion60which is part of the power tool output. Brushes62and64which are associated with the commutator50. A bearing70is also coupled with the end cap to balance rotation of the shaft42.

Turning toFIG. 2, the flux ring34is illustrated with magnets36and38. The magnets36and38are of a molded magnetic material. Preferably, the molded material is an injection molded material. The ring34is positioned within a die and the magnetic material is molded onto the flux ring. Also, the housing32may be used as the flux ring. Thus, the discussion with respect to the ring34may equally apply to the metallic housing32of the motor14.

The flux ring34includes anchors80to retain the magnets36and38onto the ring34. The anchors80may be of two types. First, anchor82is an aperture formed in the housing34. The aperture82has a first portion84and a second counter-sink portion86. The counter-sink portion86extends to the exterior88of the ring34. Thus, as seen in the cross-section inFIG. 3, as the molded magnetic material is received in the aperture82, the molded material has a neck92and a head94. The head94and neck92provide an overall rivet appearance, thus the large head94acts to retain the magnet36,38on the ring34. The ring34may be comprised of just a plurality of aperture anchors82to retain the magnets on the ring34.

Additional anchors96may be utilized on the ring. Anchors96project from the interior surface98of the ring34. Ordinarily, the anchors96are stamped or the like into the ring34forming an aperture100immediately adjacent the projecting anchor96. Thus, when the molded magnetic material forms around the projecting anchor96, it likewise goes under the anchor96and fills in the aperture100. This provides a firm securement for the magnet onto the ring34.

The ring34illustrated inFIG. 2is illustrated inFIG. 4without the magnetic material. As can be seen, the projecting anchor96has an overall rectangular shape with ends102and104unitarily formed with the ring34. The anchor has bends106,108between the legs110,112and web114. A reinforcement gusset116is positioned at the bends106,108. The reinforcement gusset116strengthens the anchor during the molding process to maintain its shape. The reinforcement gusset116may be a dimple or indent at the bend. Likewise, the aperture anchors82are illustrated in FIG.4. Also, aperture anchors82could be removed and only radially projecting anchors96would be used to retain the magnets on the housing.

The rings34are ordinarily formed from a rectangular stamped sheet material. The rectangular shaped sheet metal is stamped to form the apertures82or the projecting anchors96including the reinforcement gussets116, or both, depending upon which anchoring system is desired. The flat sheet metal part is then rolled into an annular ring and may have a butt joint99(as shown), meshing end101(as seen in FIG.6), or the like, forming the ring. The ring is then placed within a die where the magnetic material is injection molded onto the ring. The injection molded material moves through the apertures82and around the projecting anchors96as illustrated in FIG.3. Then the ring is removed from the die, it is ready for insertion into the motor housing. Likewise, the motor housing itself could be utilized as the ring. In this case, the ring would not be present and the magnets would be molded directly onto the housing with the housing being formed as described.

Moving toFIGS. 5-8, additional embodiments of the present invention are illustrated. InFIG. 5, the flux ring34′ includes optional aperture anchors82like those previously described. Here, the projecting anchors120have an overall rectangular shape with one end secured to the ring34′. The reinforcement gusset116is formed at the bend. Also, aperture122is immediately adjacent the projecting anchor120.

Moving specifically toFIG. 6, another ring34″ is shown. Here, the ring34″ includes optional aperture anchors82like those previously described. Here, the projecting anchor130has an overall L-shape. The projecting L is secured at one end to the ring34″. The reinforcement gusset116is formed near the ring34″. The aperture132immediately adjacent the projecting L-shaped anchor130likewise has an L-shape.

Turning toFIG. 7, an additional embodiment is shown. Here, the ring34′″ includes optional aperture anchors82like those previously defined, as well as projecting anchors140. The projecting anchors140have an overall rectangular shape and are angled inward directly out of the ring34′″. The reinforcement gusset116is formed near the ring34′″. Also, the aperture142is immediately adjacent the projecting anchor140.

FIG. 8illustrates an additional embodiment of the present invention. The flux ring34″″ includes optional aperture anchors82like those previously defined. The projecting anchors160have an overall T-shape. The apertures162immediately adjacent the T-shaped projecting member160likewise have a corresponding T-shape. The reinforcement gusset116is formed near the ring34″″. Thus, as the magnetic material is molded onto the ring, the T-shaped projection160is covered by the magnetic material while the T-shaped aperture162receives magnetic material both holding the magnets in place on the ring34″″.

While the above detailed description describes the preferred embodiment of the present invention, the invention is susceptible to modification, variation, and alteration without deviating from the scope and fair meaning of the subjoined claims.