Patent Application
20220168084
The present invention is directed to powered devices, and, more particularly, to powered devices such as an electric toothbrush drive unit.
One method for actuating the bristles, or other cleaning elements, of an electric toothbrush or another device having a powered handle is a drive mechanism positioned within the handle portion of the toothbrush or other device. These drive mechanisms generally convert energy from a motor into a desired movement of the bristles. The motor can be actuated by a switch to operate the drive mechanism.
There are a number of common drive mechanism styles. One style includes an electromagnetic drive, wherein the motor is operated to energize an electromagnet, and a movable permanent magnet (or a pair of permanent magnets) is positioned proximate to the electromagnet, such that the permanent magnet is driven to oscillate at an oscillating frequency by the electromagnet when the electromagnet is actuated. The electromagnetic drive unit generally results in a back-and-forth oscillating movement of the bristles.
Another common drive mechanism type is a gear drive. In gear drive mechanisms, the motor is operated to rotate a drive shaft, and a series of gears are connected between the drive shaft and a brush shaft to convert the motion of the brush shaft into a desired motion of the bristles. Gear driven mechanisms generally produce an oscillating rotational movement of the bristles.
Yet another known drive mechanism style includes the use of an eccentric weight. In this type of mechanism, the eccentric weight is connected to the motor drive shaft and positioned within a drive unit housing. Operation of the motor rotates the eccentric weight at a high speed, and causes vibration of the entire drive unit and bristles.
A workpiece, such as a brush head, for supporting the bristles or other cleaning elements is typically attached to the drive mechanism such that the workpiece is driven to move in a desired motion to by the movement of the respective drive mechanism. The workpiece generally includes a neck, which may be elongated, having a first end that is designed to attach to the drive mechanism, and a second end that supports a head and the cleaning elements. Recognizing the need to replace certain aspects of these workpieces, such as toothbrush bristles, after they are worn out or in order to provide more options, e.g., to attach a different head with a different function, manufacturers have designed these workpieces as replacement heads that fit onto separate drive units. The replacement heads can be removably attached to the drive units, for instance, by threading or otherwise connecting a portion of the replacement head onto a portion of the drive unit.
More recently, manufacturers have attempted to more efficiently control the movement of these workpieces, in order to provide a desirable workpiece motion that is cost effective to manufacture. For example, in the case of electromagnetic drive mechanisms, manufacturers have attempted to reduce the size and weight of the magnets in order to reduce costs and vibration within the handle. In the case of gear driven mechanisms, manufacturers have reduced and resized gears. Difficulties arise in these attempts, however, as small changes to the drive mechanisms can have a meaningful impact on the motion of the brush head, and on the motion conversion from the initial movement at the magnets or motor shafts to the desired movement at the bristles.
The present invention provides a drive mechanism for a powered device that efficiently converts or translates the movement of a power source and motor into a desired movement of the workpiece. More particularly, the drive unit of the present invention uses a motor driven eccentric weight in combination with a pivot housing to provide a desired oscillating movement of the brush head.
In one embodiment, the drive mechanism includes a grip housing and a pivot housing mounted within the grip housing. The pivot housing has a fixed portion, a movable portion with a free end spaced from the fixed portion, and a fulcrum. A motor is mounted within the pivot housing, and an eccentric weight extends from the motor with the motor operable to rotate the eccentric weight. A brush shaft is attached to the pivot housing opposite the free end. The brush shaft extends along the longitudinal length of the grip housing and beyond one end of the grip housing, the brush shaft having a handle end mounted to the pivot housing and a brush end opposite the handle end, the brush end adapted to receive a toothbrush head with a plurality of cleaning elements. A power source is adapted to activate the motor and rotate the eccentric weight, such that the free end of the pivot housing is driven to move by the movement of the eccentric weight, the pivot housing pivots at the fulcrum, and the brush end of the brush shaft oscillates about the fulcrum.
In one embodiment, a motor shaft extends from the motor, and when the motor is activated, the motor shaft and the eccentric weight rotate about a motor axis that is parallel to the longitudinal length of the grip housing.
In another embodiment, the fulcrum is positioned between the fixed portion of the pivot housing and the free end. The pivot housing may include a circumferential outer wall section and a circumferential inner wall section, the inner wall section spaced from and positioned within the outer wall section, the outer wall section and the inner wall section connected by a bridge, wherein the bridge forms the fulcrum for the pivoting of the pivot housing. The bridge may include one or more bridge segments that twist in torsion as the pivot housing pivots. The bridge segments may be aligned, and may extend along a diameter of the outer wall section and the inner wall section, with the pivot housing further defining a first gap between the outer wall section and the inner wall section on a first side of the bridge and a second gap between the outer wall section and the inner wall section on a second side of the bridge. The first gap and the second gap may be at least partially filled with a thermoplastic elastomer to fill and seal the gaps but enable the twisting of the bridge segments.
The grip housing may include an open mouth at one end and a closed second end, with the pivot housing mounted adjacent to the open mouth to substantially close off the open mouth. In one embodiment, a cap is connected to the pivot housing and over the open mouth to seal the pivot housing within the grip housing. The fixed portion of the pivot housing may be designed to fixedly attach to the grip housing. In one embodiment, the outer wall section of the pivot housing includes structure adapted to snap fit into the open mouth of the grip housing.
In one embodiment, the pivot housing is at least partially enclosed by a circuit board housing, wherein a printed circuit board is mounted to the circuit board housing and at least one switch is operably connected to the circuit board, the printed circuit board is electrically connected to the switch and the battery such that actuation of the switch by the user causes the motor to rotate at a speed and time as programmed.
The drive mechanism of the present invention provides an efficient, cost effective method for providing oscillating side-to-side movement of a brush head without the need for springs, gears or magnets. The characteristics of the drive motion can be tuned with small alterations to the bridge segments, and the speed and timing of operation can be programmed via the printed circuit board as desired for a particular tooth brushing application.
The drive mechanism of the present invention efficiently converts or translates rotational movement of a drive shaft and eccentric weight into a desired back-and-forth movement of the workpiece, such as a brush head. The pivot housing enables such a conversion without the need for springs, magnets, or a complex gearing arrangement.
I. Overview
A drive mechanism for use in powered devices such as an electric toothbrush is shown in
II. Structure
The drive unit 12 includes a grip housing 26 that forms an exterior shell of the drive unit 12. The grip housing 26 has an exterior surface 28 forming a grip surface for a user, and an interior surface 30 opposite the exterior surface and defining a hollow internal cavity 32. In one embodiment, the grip housing 26 is generally tubular, and in a more specific embodiment, the grip housing 26 is generally a cylindrical tube. The grip housing 26 includes a first end 34 and a second end 36 opposite the first end 34. In the illustrated embodiment, the cylindrical shape has a slight flare approaching the first end 34, and the first end 34 forms an opening or mouth 38. The grip housing 26 has a second end 36 opposite the first end, and in the illustrated embodiment the second end 36 is rounded and closed. The grip housing 26 may be formed from a variety of materials, but in the illustrated embodiment the grip housing 26 is formed from a molded thermoplastic, such as PVC. In the illustrated embodiment, the exterior grip surface 28 is generally smooth and rigid, but in another embodiment it may be formed from, or overlaid with, a tactile grip material such as a thermoplastic elastomer. In one embodiment, the grip housing 26 is a two piece housing, with a motor portion 40 including the first end 34, and a battery portion 42 including the second end 36. The battery portion 42 may be removable from the motor portion 40, for example, by a snap fit or a series of threads, for access to the internal cavity 32 and for battery replacement. As illustrated, the battery portion 42 snap fits to the motor portion and an elastomeric sealing ring 44 is positioned between the portions 40, 42 for preventing liquid or other debris from entering the internal cavity 32. The grip housing 26 defines a longitudinal axis 35 for the drive unit 12 extending centrally through the cylindrical grip housing 26 from the first end 36 to the second end 36.
In one embodiment, a cap 46 is fitted into the mouth 38 of the grip housing 26 to cover the mouth 38 of the grip housing 26. Referring now to
The pivot housing 16 is positioned within the interior cavity 32 of the grip housing 26 adjacent to the mouth 38 of the grip housing 26. In one embodiment, the pivot housing 16 includes an outer, fixed housing 68 and a central, pivoting housing 70. The outer housing 68 is fixed within the grip housing 26, whereas the central housing 70 is spaced inside the outer housing 68 and movable with respect to the outer housing 68 and grip housing 26 as described in more detail below. More particularly, the outer housing 68 has a sidewall 71 with a diameter that generally fits tightly within and against the inner surface 30 of the grip housing 26. Referring to
Referring to
The motor housing portion 104 of the central housing 70 houses the motor 20. In the illustrated embodiment, the motor housing 104 is a two piece housing, with an upper section 112 and a lower section 114 that snap together to house the motor 20. The upper section 112 is a generally cylindrical, tubular section that extends around the part of the sleeve 102 that is immediately below the outer housing 68. The upper section 112 has an open lower end 126. Similar to the upper section 112, the lower section 114 may be a generally cylindrical, tubular section. The lower section 114 may have an open upper end 128, and at least one opening 130 that aligns and receives a corresponding detent 124 in the sleeve 102 such that the upper section 112 and lower section 114 can together to define an internal cavity 132. As shown, for example, in
Notably, the outer housing 68 and the central housing 70 of the pivot housing 16 are connected to one another, and the location of such connection forms a fulcrum 24 for pivoting of the pivot housing 16.
The motor 20 is positioned within the interior cavity 132 in the motor housing 104. In one embodiment, the motor 20 is a DC motor including a motor shaft 150 and an eccentric weight 22 attached to the motor shaft 150 such that activation of the motor 20 will rotate the motor shaft 150 and the eccentric weight 22 at a desired speed, causing a vibratory movement at the location of the eccentric weight 22. As shown in
In one embodiment, a circuit board housing 180 is positioned in the grip housing 26 between the grip housing 26 and the pivot housing 16. With reference to
Referring to
As shown in
The brush shaft 18 is mounted to the pivot housing 16 such that the brush shaft 18 is movable with respect to the grip housing 26. The brush shaft 18 as illustrated is a straight shaft, generally comprised of metal or another rigid material, and extending along the longitudinal axis of the drive unit 12. In one embodiment, the brush shaft 18 is mounted in the recess 110 in upper end 106 of the sleeve 102. The sleeve 102 may be overmolded onto the brush shaft 18, or the brush shaft 18 may be attached within the recess by another method. As illustrated, the brush shaft 18 includes an annular recess 210 to prevent axial removal of the brush shaft 18 from the sleeve 102. The brush shaft 18 also includes structure to receive a replacement brush head 14. The brush head 14 generally includes a central bore or receptacle (not shown) that receives the brush shaft 18 for operation of the toothbrush 100. In one embodiment, the brush shaft 18 and receptacle are keyed to properly align the brush head 14 on the brush shaft 18. As shown in
Various characteristics of the drive mechanism 10 can be altered in order to control the movement of the brush head 14. For example, the lengths of the respective moment arms 161, 163 can be predetermined, and altered as desired, to provide a desired movement of the brush head 14. In one embodiment, the length of the second moment arm 163 is approximately 90-95% of the length of the first moment arm 161 to provide a desired side-to-side (and slightly arcuate) motion of the brush head 14. The lengths of the moment arms 161, 163, and the length of each moment arm 161, 163 with respect to the other, may be altered by the manufacturer as desired to produce greater or lesser movement of the second moment arm 161 (which is approximately the same as the movement of the brush head 14). In another embodiment, the characteristics of the bridge 156 and bridge segments 158, 160 can be altered to provide a desired movement. For example, the thickness or cross sectional geometry of the bridge segments 158, 160 can be changed in order to increase or decrease the amplitude and speed of the brush head 14 movement. In the illustrated embodiment, the bridge segments 158, 160 have a generally rectangular cross section, but may otherwise be provided with a square cross section, circular cross section, hexagonal cross section, or otherwise in order to provide the desired movement. In another embodiment, the stiffness of the elastomer 170 can be altered to provide a desired brush head 14 movement.
III. Operation
The toothbrush 100 is designed such that, in operation, the switch 192 can be actuated by a user to activate the motor 20 and oscillate the brush head 14 back and forth in a side-to-side motion by pivoting about the fulcrum 24 created by the pivot housing 16. The steps of operation are described below in more detail.
Initially, a user will attach a brush head 14 to the brush shaft 16 by inserting the brush shaft 18 into the central recess within the brush head 14. The keyed shape of the brush shaft 18 and brush head 14 acts to orient the brush head 14 with the cleaning elements 220 extending in a desired direction. In one embodiment, the cleaning elements 220 have cleaning element direction that extends generally perpendicular to the pivot axis 155 of the spring mechanism 10 as described in more detail below.
The toothbrush 100 is operated by a user by pressing the switch 192, whereby the battery 200 is electrically connected to the circuit board 190 and the motor 20. The motor 20 thus operates to rotate the motor shaft 150 and eccentric weight 22 at the speed and timing that has been programmed. The rotating motor shaft 150 is aligned with the longitudinal axis of the drive unit 10 (defined by the central axis of the grip housing 26), and the eccentric weight 22 is offset from the longitudinal axis, such that rotation of the eccentric weight causes an oscillating vibration at the location of the eccentric weight 22.
The oscillating vibration of the eccentric weight 22 is converted into side-to-side oscillation of the brush shaft 18 (and brush head 14) about the fulcrum 24 due to the structure of the pivot housing 16. In short, the pivot housing 16 has a fixed outer housing 68 and a movable central housing 70 that are connected to one another by a bridge 156. The bridge 156 forms the fulcrum point 24 for pivoting of the central housing 70 portion of the pivot housing 16, and controls the direction of oscillation via the orientation of the direction of the bridge 156 with respect to the grip housing 26 and the direction of the cleaning elements 220. In the specific embodiment illustrated, the bridge 156 is formed by a pair of bridge segments 158 that extend between a sleeve 102 of the central housing 70 and an inner surface 30 of the outer housing 68. The bridge segments 158 align with each other along a diameter of the grip housing 26, outer housing 68 and central housing 70, with each bridge segment 158 extending from an opposite side of the sleeve 102 to the inner surface 84 of the outer housing 68. The direction of the bridge segments 158 and bridge 156 sets the orientation the pivot axis 155 in a desired direction, which in the illustrated embodiment is a direction perpendicular to the flat surface 214 of the brush shaft 18. As a result, operation of the motor 20 and the oscillatory vibration of the eccentric weight 22 causes pivoting of the central housing 70 in a generally back-and-forth oscillating movement about the bridge 156, such that the bridge segments 158 twist together in torsion about the pivot axis 155 and the central housing 70 pivots about the pivot axis 155 in the manner of a seesaw. The direction of the movement of the motor housing 104 would be generally up and down as illustrated in
The above description is that of the current embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.
