U.S. patent application number 12/996638 was filed with the patent office on 2011-05-12 for brushhead assembly for a power toothbrush.
This patent application is currently assigned to KONINKLIJKE PHILIPS ELECTRONICS N.V.. Invention is credited to Christopher Dabrowski, Patrick A. Headstrom.
Application Number | 20110107536 12/996638 |
Document ID | / |
Family ID | 40394220 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110107536 |
Kind Code |
A1 |
Dabrowski; Christopher ; et
al. |
May 12, 2011 |
BRUSHHEAD ASSEMBLY FOR A POWER TOOTHBRUSH
Abstract
A brushhead assembly for use with a power toothbrush, comprising
a toothbrush element (18), a mounting neck (22) on which the
toothbrush element is mounted and a coupling member (24) which
mates a driveshaft (from a drive system in a handle assembly
portion (12) of the toothbrush to the mounting neck. A ring member
(34) is positioned within a groove (30) at the proximal end (32) of
the coupling member to create a desired brushhead assembly inertia.
On an extending portion of the coupling member is mounted a spring
member (28) which is configured and arranged and has such a spring
rate that when the coupling member and mounting neck are installed
into a driveshaft, a preload force is created between the brushhead
assembly and the driveshaft sufficient to react the torque created
by the rotating inertia movement of the brushhead assembly, without
lost motion or noise.
Inventors: |
Dabrowski; Christopher;
(Lynwood, WA) ; Headstrom; Patrick A.; (Seattle,
WA) |
Assignee: |
KONINKLIJKE PHILIPS ELECTRONICS
N.V.
Eindhoven
NL
|
Family ID: |
40394220 |
Appl. No.: |
12/996638 |
Filed: |
July 2, 2008 |
PCT Filed: |
July 2, 2008 |
PCT NO: |
PCT/IB2008/052667 |
371 Date: |
January 10, 2011 |
Current U.S.
Class: |
15/167.1 |
Current CPC
Class: |
A61C 17/3418 20130101;
A61C 17/222 20130101 |
Class at
Publication: |
15/167.1 |
International
Class: |
A46B 9/04 20060101
A46B009/04 |
Claims
1. A brushhead assembly for use with a power toothbrush which
includes a handle assembly to which the brushhead assembly is
mounted, comprising: a toothbrush member (18); a mounting neck
member (22) on which the toothbrush member is mounted; a coupling
member (24) which mates a motor driveshaft (14) from a handle
assembly portion (12) of the toothbrush to the mounting neck
member; and an inertia member assembly (34) associated with the
coupling member for producing a pre-selected inertia ratio between
the brushhead assembly and the handle assembly of the
toothbrush.
2. The brushhead assembly of claim 1, wherein the inertia member
assembly is positioned so as to be symmetrical about a rotational
axis of the toothbrush.
3. The brushhead assembly of claim 1, wherein the inertia member
assembly is positionable within the coupling member.
4. The brushhead assembly of claim 1, wherein the inertia member is
positionable on the outside of the coupling member.
5. The brushhead assembly of claim 1, wherein the inertia assembly
is a continuous ring.
6. The brushhead assembly of claim 1, wherein the ring is
metal.
7. The brushhead assembly of claim 5, wherein the ring has a
dimension which is greater than the other parts of the brushhead
assembly.
8. The brushhead assembly of claim 5, wherein the ring is a ceramic
or plastic material.
9. The brushhead assembly of claim 1, wherein the inertia assembly
is positioned in a circumferential groove (30) at a proximal end
(32) of the coupling member.
10. The brushhead assembly of claim 5, wherein the friction force
between the inertia ring and the coupling member is sufficient to
prevent rotational slippage of the ring at torque values
encountered during normal operation of the toothbrush.
11. The system of claim 9, wherein the circumferential groove
includes elements (74) tending to prevent axial and/or rotational
movement of the ring during operation of the toothbrush.
12. In a brushhead assembly for use in a power toothbrush which
comprises a toothbrush member (18), a mounting neck element (22) on
which the toothbrush member is mounted and a coupling member (24)
which mates a motor driveshaft (14) from a motor drive assembly
present in a handle assembly portion (12) of the power toothbrush
to the mounting neck, the improvement comprising: a ring member
(34) connected to the coupling member for tuning the inertia of the
brushhead assembly relative to the inertia of the handle assembly
portion of the toothbrush to a pre-selected ratio.
13. The improvement of claim 12, wherein the ring member is
positioned within a circumferential groove (30) in the coupling
member so that it is symmetrical about the rotational axis of the
toothbrush.
14. The improvement of claim 12, wherein the ring member is metal,
and, wherein the friction force between the ring member and the
groove in the coupling member is such as to substantially prevent
rotational slippage of the ring member at values of torque on the
coupling member produced during operation of the toothbrush.
15. A brushhead for use with a power toothbrush, comprising: a
toothbrush member (18); a mounting neck (22) on which the
toothbrush element is mounted; a coupling member (24) which mates a
driveshaft (14) from a motor drive assembly contained within a
handle assembly portion (12) of the toothbrush to the mounting
neck; and a spring member (28) fitted on an extending portion of
the coupling member, into which coupling member the driveshaft fits
sufficiently tightly, with the force of the spring member, to
transfer the oscillating action of the driveshaft to the mounting
neck, and vice versa, as the brushhead member oscillates in
response to action of the driveshaft.
16. The brushhead assembly of claim 15, wherein the spring member
is insertable onto and removable from the extending portion of the
coupling member and wherein the spring member is configured and
arranged structurally to produce a sufficiently tight fit between
the spring member, coupling member and the driveshaft to react
and/or transfer torque between the driveshaft and the brushhead
assembly when the driveshaft is operatively inserted into the
coupling member and the coupling member is operatively inserted
into the mounting neck.
17. The brushhead assembly of claim 15, wherein the spring member
produces a preload which is sufficient to prevent relative movement
between the brushhead member and the driveshaft while permitting
convenient removal of the mounting neck and brush element from the
driveshaft.
18. The brushhead assembly of claim 15, wherein the spring member
is an angular C shape which fits around the exterior surface of the
coupling member.
19. The brushhead assembly of claim 15, wherein the spring member
is in the form of a closed oval, a closed circle, a coil spring or
a leaf spring.
20. In a brushhead assembly for use with a power toothbrush which
comprises a toothbrush element (18), a mounting neck (22) on which
the toothbrush element is mounted and a coupling member (24) which
mates a driveshaft (14) from a motor drive assembly within a handle
assembly portion (12) of the toothbrush to the mounting neck, the
improvement comprising: a spring member (28) fittable onto an
extending portion of the coupling member (24), into which coupling
member the driveshaft fits sufficiently tightly, with the force
produced by the spring member, that the coupling member follows the
oscillating action of the driveshaft and reacts the torque from the
resulting oscillating action of the brushhead assembly.
21. In the brushhead assembly of claim 20, the spring member
comprises a metal element, with a spring rate which prevents lost
motion between the driveshaft and the mounting neck.
Description
[0001] This invention relates generally to brushhead assemblies for
power toothbrushes and more specifically concerns specific elements
within a coupling portion of the brushhead assembly which provides
improved operation of the toothbrush.
[0002] There are many types of brushhead assemblies which are
currently used on power toothbrushes. These brushhead assemblies
include coupling members which connect a toothbrush motor
driveshaft to a support arm/neck portion of the brushhead assembly,
on which is mounted a toothbrush member. The coupling member
transfers torque loads between the driveshaft and the brushhead
assembly, and vice versa, as the driveshaft and the brushhead
rotate or oscillate through a particular angle. If the coupling
member cannot react action of the driveshaft and the corresponding
action of the brushhead assembly, the result is lost motion and/or
noise in operation of the toothbrush.
[0003] The acceleration of the mass of the brushhead assembly in
response to oscillating action of the driveshaft creates a large
torque load on the driveshaft. When coupling members include
plastic elastic springs to preload the brushhead assembly to the
driveshaft, the forces on brushhead assemblies of certain power
toothbrushes become too great for the plastic springs to withstand,
given the current required small size of the brushhead
assembly.
[0004] Accordingly, it is desirable to be able to reliably react
the torque created by action of the driveshaft and the related
acceleration of the brushhead assembly, without lost motion and/or
noisy operation.
[0005] An important consideration in a power toothbrush is the
tuning of the rotational inertia of the system. It is desirable
that the brushhead assembly and the remainder of the toothbrush
(the handle with the drive train) have an inertia ratio which
produces good cleaning results. Presently, it is difficult and
expensive to tune the system inertia to achieve the desired ratio
with different sizes of brushheads or attachments and a common
drive system/platform. It would hence be desirable to have a
brushhead assembly which includes the capability of conveniently
and simply adjusting, i.e. "tuning", the inertia of a variety of
brushhead assemblies to achieve a desired inertia ratio with a
given drive system/handle assembly.
[0006] One aspect of the embodiments disclosed herein is directed
toward a brushhead assembly for use with a power toothbrush which
includes a handle assembly to which the brushhead assembly is
mounted, comprising: a toothbrush member; a mounting neck member on
which the toothbrush member is mounted; a coupling member which
mates a motor driveshaft from a handle assembly portion of the
toothbrush to the mounting neck member; and an inertia member
assembly associated with the coupling member for producing a
pre-selected inertia ratio between the brushhead assembly and the
handle assembly.
[0007] Another aspect of the disclosed embodiments is directed
toward a brushhead for use with a power toothbrush, comprising: a
toothbrush member; a mounting neck on which the toothbrush member
is mounted; a coupling member which mates a driveshaft from a motor
drive assembly contained within a handle assembly portion of the
toothbrush to the mounting neck; and a spring member fitted on an
extending portion of the coupling member, into which coupling
member the driveshaft fits sufficiently tightly, with the force of
the spring member, to transfer the oscillating action of the
driveshaft to the mounting neck, and vice versa, as the brushhead
member oscillates in response to action of the driveshaft.
[0008] FIG. 1 is a partially exploded view of a toothbrush with a
removable brushhead assembly.
[0009] FIG. 2 is an exploded view of the removable brushhead
assembly of FIG. 1, which includes a coupling portion.
[0010] FIGS. 3A, 3B and 3C are front elevational, side elevational
and rear elevational views of the coupling portion of FIG. 2.
[0011] FIG. 3D is a cross-sectional view of FIG. 3B.
[0012] FIG. 4 is a perspective view showing a coupling spring
element in place on the coupling portion.
[0013] FIGS. 5A and 5B are perspective and elevational views of the
coupling spring of FIG. 2.
[0014] FIG. 6 is a simplified diagram showing a nodal-mounted
resonance system for a power toothbrush.
[0015] FIG. 7 is an exploded view of a coupling member showing the
inertia ring relative thereto.
[0016] FIG. 8 is a cross-sectional view showing the inertia ring in
place on the coupling member.
[0017] FIG. 9 is a perspective, partially cutaway view of a
coupling member with the inertia ring therein.
[0018] FIG. 1 shows a power toothbrush 10, comprising generally a
handle portion 12 which includes a drive assembly which oscillates
a driveshaft 14 through a specific angle. In one example, the angle
is .+-.8.degree. for a total of brushhead movement of 16.degree..
Other angles of movement may be used. Mounted on an end portion 15
of driveshaft 14 is a brushhead assembly 16. Brushhead assembly 16
includes a toothbrush member 18, a mounting arm or neck 22 and a
coupling member 24.
[0019] Referring to FIG. 2, mounted on the distal end 26 of
coupling member 24 is a coupling spring 28. Coupling member 24
connects, i.e. couples, the driveshaft 14 to mounting arm 22.
Mounted in a circular groove 30 in the proximal end 32 of coupling
member 24 is an inertia ring 34. Mounted on the proximal end 32 of
coupling member 24 is a color ring 38 which abuts handle portion 12
when the brushhead assembly is operatively positioned on the handle
portion.
[0020] Disclosed herein is inertia ring 34 which is used to create
a desired inertia ratio between brushhead assembly 16 and the
remainder (the handle with the drive train) of the toothbrush. Also
disclosed herein is coupling spring 28 which mates coupling member
24 to the driveshaft 14 for reliably transferring drive torque from
driveshaft 14 to the brushhead assembly 16 and for reacting torque
from the accelerating brushhead assembly 16 back to the driveshaft
14 without a loss of torque/motion or vibration.
[0021] FIGS. 3A, 3B, 3C and 3D show coupling member 24 in more
detail. Coupling member 24 in the embodiment shown is plastic. It
has a color ring groove 42 at the proximal end exterior surface for
locating and retaining color ring 38. This arrangement permits ease
of user installation and removal of color ring 38; different color
rings are used to identify different users.
[0022] Forward of groove 42, the coupling member 24 has an inwardly
angled surface portion 43, i.e. cone-shaped, with a length of
approximately 1/4 inch, until a lower radial locating ring 44 is
reached. Locating ring 44 is used to adjust the fit of the coupling
member 24 and to positively locate the coupling member to the lower
edge 27 of mounting neck 22.
[0023] Extending forwardly from the radial locating ring 44 is a
brushhead assembly axial retention portion, comprising two opposing
recesses 46 and 48. These are configured to mate with matching
portions on the interior surface of mounting neck 22, and provide
the retention capability to maintain coupling member 24 in mounting
neck 22 during operation. Extending between the end of angled
surface portion 43 to the distal end 26 of coupling member 24,
located peripherally around the mounting member half-way angularly
between recesses 46 and 48, is a torque transfer rib 52. Rib 52 is
approximately 1/8-inch wide and 1/2-inch long. Rib 52 interfaces
with a mating recess in mounting neck 22 and acts as a primary
element for transfer of torque between driveshaft 14 and mounting
neck 22.
[0024] Positioned 180.degree. from rib 52 is a preload contact
element 56. As discussed in more detail below, element 56 acts to
take up the clearance between coupling spring 28 and driveshaft 14,
and transfers the preload force of spring 28 into a clamping action
on the driveshaft, to provide torque transfer. An alignment rib 60
is aligned with contact element 56, positioned between angled
surface portion 43 and the proximal end of contact element 56. The
alignment rib 60, along with rib 52, acts to transfer torque
between coupling member 24 and mounting neck 22, as well as
minimizing angular motion between these two members.
[0025] Coupling member 24 includes a cap element 58 at the distal
end 26 of coupling member 24. The cap 58, along with ring 44,
transfers user-generated loads on the brushhead from mounting neck
22 to coupling member 24, as well as reinforces and provides
additional stiffness to the distal end surface of coupling member
24.
[0026] Referring now to FIG. 3D, the coupling member 24 at its
proximal end 32 thereof includes a circular groove 70 which extends
into the coupling member, the groove including a swage lip 72 at
the rear outer peripheral edge thereof. The inertia ring 34 (not
shown) fits within groove 70. Groove 70 locates and restrains the
inertia ring 34. Three crushable ribs 74 are spaced around the
outer peripheral surface of groove 70 to adjust and maintain the
fit and tolerances between inertia ring 34 and groove 70, assisting
in preventing rotational slippage of the inertia ring 34 relative
to the coupling member 24 during operation of the appliance. This
will be described in more detail below.
[0027] FIG. 4 and FIGS. 5A and 5B show the coupling spring member
28 in more detail, including in its operative position around the
distal end of coupling member 24 within driveshaft 14 in place
within coupling member 24. In the embodiment shown, spring 28 is
made from metal and is formed into a generally angular "C" shape,
that fits around the distal end portion 26 of the coupling member.
The "C" shape spring member 28 is 5.0 mm in dimension 57 and 3.55
mm in dimension 59, with an opening 61 of 1.7 mm. Spring member 28
is made from stainless steel, approximately 0.15 mm thick.
[0028] When operatively positioned, it is in contact with transfer
rib portion 56, which is pushed slightly outwardly by the insertion
of driveshaft 14. The C-shaped spring member 28 extends around the
distal end portion of the coupling member, with the longitudinal
edges of the opening contacting alignment rib 52.
[0029] Spring 28 is arranged so that the torque provided by
driveshaft 14 through coupling 24 is transferred to the mounting
neck 22; the arrangement also reacts the torque produced by
acceleration of the brushhead assembly back to the driveshaft. A
minimum force F.sub.min is required to stop the spring 28 from
opening and causing lost motion in the system. The force designated
F in FIG. 4 is created against the spring member, when operatively
positioned, to allow tolerances in the parts. The force F must be
great enough to maintain good torque transfer, without slippage,
while not being so great as to make the force necessary for axial
removal of the combination of the mounting neck and brush element
mounted thereon from the coupling member inconvenient for the
average user.
[0030] The force F is created by deforming the spring member 28,
which has a stiffness K. The important parameters of the spring are
the maximum spring deflection, the minimum preload force and the
maximum preload force. The minimum preload force F.sub.min
discussed below is defined by the torque transfer requirement
between the driveshaft 14 and the brushhead assembly 16. The
maximum force F.sub.max is determined by the maximum displacement
of the spring and the spring rate. Spring rate deflection is based
on the clearances between the coupling member 24 and the mating
surfaces of the driveshaft. The minimum preload force is
F.sub.min=T.sub.max/d, where T.sub.max is equal to the maximum
torque on the device, and d is equal to the distance 73 in FIG. 4.
In one example, T.sub.max is 50.2 Newton-mm, while d=1.47 mm, and
F.sub.min is 34.15N.
[0031] The spring rate K can be calculated as follows:
K = F min i min ##EQU00001##
where i.sub.min equals i.sub.nominal-tolerance value. i.sub.nominal
equals 0.5 mm, while tolerance value equals .+-.0.17 mm; i.sub.min
thus equals 0.5-0.17=0.33 mm. From above, where F.sub.min equals
34.15 N in order to provide the desired torque transfer, K equals
103.5 N/mm. The maximum spring force now can be calculated. Using
the above spring rate and the interference tolerance, the maximum
spring force is 69.4 N.
[0032] In actual use, spring 28 opens after insertion of the
coupling member into the mounting neck until it contacts the
internal surface of the mounting neck 22, thereby engaging the
coupling member 24 with the mounting neck 22. With such an
arrangement, points 78 and 80 (FIG. 4) between driveshaft 14 and
the coupling member 24 do not rock or open as the driveshaft 14
oscillates in operation.
[0033] Hence, in functional summary, coupling spring 28 deforms
slightly as the driveshaft 14 is inserted into the coupling member
24, thereby creating a preload that is sufficient to react the
dynamic torque between the driveshaft and the coupling neck without
lost motion or noise.
[0034] Further, the spring rate discussed above, with the stated
minimum and maximum spring forces, results in a convenient pull-off
force for the mounting neck. The coupling spring 28 produces a
sufficiently high preload, in a small size, that smaller components
can be used for the toothbrush, which is desirable.
[0035] There are alternatives to the specific angular C-shaped
configuration of FIGS. 5A and 5B. The spring could be a closed
oval, or a closed circle. Further, the spring could be a coil
spring, while in still another alternative, a leaf spring is
attached to the coupling member, extending more or less parallel to
the axis of the shaft. The spring deforms when the shaft is
inserted and provides a preload to react torque back to the shaft
from the acceleration of the rotating mass. The leaf spring could
be attached to the mounting neck instead of the coupling.
[0036] The inertia ring 34, as indicated above, fits into the
circular groove 70 in the proximal end 32 of the coupling member
24, as shown most clearly in FIGS. 7 and 8. While the ring 34 is
preferably made from metal, it can also be made from various
ceramics, plastic or wire, although the material should preferably
have a higher density than the other components of the brushhead
assembly. The significance of the ring is illustrated in FIG. 6,
which is a schematic illustration of a nodal-mounted resonance
system 86 for a power toothbrush. It should be understood, however,
that the inertia ring is not limited to a nodal system. The inertia
ring creates a desired ratio between both sides of the node in a
nodal system. The nodal resonance system 86 includes two
counter-rotating masses 88 and 90 and a central nodal mount 92
which remains still while masses 88 and 90 counter-rotate. Spring
members 89 and 91 connect the masses to the nodal mount. The nodal
mount 92 is connected to the housing (handle) 94 by spring 95.
[0037] The counter-rotating masses have specific values of
rotational inertia, such that a given rotational excitation input
results in a given rotational output, with the system operating at
a resonant frequency. The inertia ring provides an ability to
easily produce the desired inertia ratio between the input system
88 and the output system 90. The inertia ring positioned in the
proximal end of the coupling member, when properly selected,
produces a desired inertia ratio between the brushhead assembly and
the handle/drive system assembly. The size, configuration and
material of the ring can be adjusted so that the resulting inertia
of the brushhead portion of the system is such as to produce the
desired inertia ratio between the brushhead portion and the handle
portion of the system. For instance, in a given toothbrush, it may
be desirable to change the brushhead with a different inertia. The
inertia ring is then designed to produce the desired ratio between
the brushhead and handle portions. The ratio can vary. One example
of an inertia ratio which produces good cleaning results is 1.5.
The design of the inertia ring is carried out as follows.
[0038] The brushhead system will have a specific inertia value,
i.e. the rotational inertia of the brushhead about the axis of
rotation 80 (FIG. 7). The difference between the required brushhead
inertia to provide the desired ratio and the sum of the actual
calculated inertia of the various brushhead assembly components
must be made up by the inertia ring. An example of an inertia ring
is shown in FIGS. 7 and 8, which includes inertia ring 34
positionable in coupling member 24, at the distal end of which is
the coupling spring 28. When ring 34 is in an operative position,
it is contained within circular groove 70, as shown in FIG. 8. In
one specific embodiment, the ring is made from metal, such as
stainless steel, with an outside diameter of 12.2 mm, a thickness
of 1.0 mm and a width of 3.30 mm. The peripheral edges of the ring
are typically chamfered.
[0039] A ring configuration is most convenient to accomplish the
matching inertia function, since it has inherently the important
characteristic of being symmetrical about the rotational axis of
the appliance when it is located within groove 70. However, while
ring 34 is shown as a single member, it could be a plurality of
separate elements, such as arcuate segments, as long as the
segments in combination are symmetrical in position about the
rotational axis of the appliance. It is possible for the inertia
member to be asymmetrical if correctly compensated for. Also, while
preferably the ring is within the coupling member, it could be
positioned outside the coupling member.
[0040] It is important that the inertia ring be held firmly within
the groove, as if it were rigidly attached to the driveshaft. Any
movement of the ring within groove 70 must thus be prevented,
axially as well as rotationally. Axial movement is prevented by the
crushable ribs 74 present in groove 70, which tend to hold the ring
against axial movement. Rotational movement is prevented by
frictional contact between the outer surface of the ring and the
matching groove surface.
[0041] There is a maximum torque which can be tolerated by the
combination before slippage of the ring occurs. The maximum torque
T=r*F.sub.f=rUF.sub.N, where r is the distance between the exterior
surface of the ring and the axis of the coupling member, U is the
coefficient of friction between the exterior surface of the ring
and the surface of the coupling member groove and F.sub.N is equal
to the normal force exerted against the ring toward the axis. The
friction force (i.e. the coefficient of friction U, multiplied by
the normal force F.sub.N) must be large enough to prevent slippage
of the ring within the groove 70, which would lead to noise and an
inefficient transfer of torque between the brushhead assembly and
the driveshaft. With a known radius, coefficient of friction and
normal force, the maximum torque which can be placed on the
coupling member can be readily calculated.
[0042] Hence, a coupling spring and an inertia ring have been
disclosed which increase the operating effectiveness of brushhead
assembly action in a power toothbrush which includes a driveshaft
extending from the handle portion thereof. The inertia ring is used
in a nodal-mounted dynamic resonance system.
[0043] Although a preferred embodiment of the invention has been
disclosed here for the purposes of illustration, it should be
understood that various changes, modifications and substitutions
may be incorporated in the embodiment without departing from the
spirit of the invention, which is defined by the claims which
follow.
* * * * *