Mechanical-type toothbrush having a removable brushhead

A toothbrush includes a brush part and a hollow handle part exhibiting an axial bearing, a coupling rod, which is slidably mounted in the axial bearing and which is connected to the brush part, a return spring, which is pretensioned on the coupling rod in the direction of the handle part opposite the brush part, and a latching device for rotationally locking the coupling end of the brush part and the coupling end of the handle part. A securing device serves to prevent axial motion of the coupling rod. A first part of the securing device is associated with the coupling rod and a second part of the securing device is associated with the handle part. The second part of the securing device is movable between a securement setting and a release setting and is pretensioned by a spring in the direction of the securement setting. An actuating device in the wall of the handle part serves to actuate the second part of the securing device. An axial motion of the brush part relative to the handle part, for releasing the rotationally secure connection of the two parts, is therefore reliably prevented.

BACKGROUND OF THE INVENTION 
The invention relates to a toothbrush having the desired characteristic of 
a removable and therefore, replaceable brushhead. 
When a used brush such as the type disclosed in DE 4136537 C1 is removed 
from the handle part of this known toothbrush, the brush part has to be 
pulled quite a long way out of the handle before it can be detached, by a 
rotational motion, from the screw thread of a threaded pin located at the 
protruding end of the coupling rod. For this purpose, the coupling rod 
must firstly be moved in the handle part a certain distance axially away, 
counter to the action of the return spring. 
SUMMARY OF THE INVENTION 
The object of the invention is to improve the abovementioned known 
toothbrush such that the described axial relative motion of the brush part 
relative to the handle part, for releasing the rotationally secure 
connection of the two parts, can be reliably prevented. 
The effect of using a securing device to accomplish this object is that 
under no circumstances can the brush part be moved into a dismantling 
setting by a relative axial motion relative to the handle part, when this 
is not intended. Accordingly, the actuating device has to be actuated in 
order for a used brush part to be removed and for a new brush part to be 
fitted to the handle part. Moreover, the design of the actuating device 
and of the pretensioning spring acting on the coupling rod enables an 
additional facility for preventing the detachment of the brush part from 
the handle part by smaller children. 
According to a preferred embodiment of the invention, the coupling rod is 
simultaneously configured as a control device, which interacts with a 
locking lever. This control device for the locking lever is designed such 
that when the brush part is fitted, as a result of the locking lever being 
unlocked by the actuating device, the locking lever is moved into the 
range of influence of a control cam and is held by the control cam in the 
unlocked setting, counter to the force of a pretensioning spring, up to an 
axial setting of the coupling rod in which the brush part can be unlatched 
and detached from the handle part. In this setting, the locking lever 
slides out of the control cam, so that the locking lever is moved, under 
the action of the pretensioning spring acting on it, into a pre-locking 
setting in which the locking catch slides along a control rod, configured 
in one part with the coupling rod, to the point where the locking paw of 
the locking lever falls into a locking groove of the control rod under the 
influence of the pretensioning force of the spring acting on the locking 
lever and thereby locks the coupling rod and the brush part connected 
thereto such that they are axially immovable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate a toothbrush 30, the brush part 32 of which is 
removably fastened to a handle part 34. A coupling rod 36, which is 
preferably made of plastic and projects from the front end of the handle 
part 34 facing the brush part 32, can be screwed into an integral coupling 
opening 38, provided with a screw thread, in the brush part, which brush 
part is disposed in a reinforced part of a bristle bed 33, the reinforced 
part receiving bristles 39 of the brush part 32, in a rear end of the 
brush part 32 facing the handle part 34. 
The coupling rod 36 is mounted in an axial sliding bearing 40 in the front 
end of a neck 41 of the handle part 34, such that it can be moved to a 
limited extent axially, counter to the force of a pretensioning device 42, 
out of the front end of the handle part 34, yet cannot be rotated. The 
coupling rod 36 is provided at its front end with a thread 44, which can 
be screwed into the coupling opening 38 in the brush part 32. The thread 
has an angle of rotation of no more than 180.degree.. Projecting axially 
from the rear end of the brush part 32, on the side of the bristles 39, is 
a stop cam 46, which is matched by an axial recess 48 in the front end of 
the handle part 34. As the brush part 32 is screwed on, the stop cam 46, 
after a small angle of rotation, comes to bear against an end face 50 of 
the front end of the handle part 34. Upon a continuing screw-on motion of 
the brush part 32 or a corresponding screw-in motion of the handle part 34 
into the brush part 32, the threaded coupling rod 36, according to the 
thread pitch, is pulled out of the front end of the handle part 34, 
counter to the action of the pretensioning device 42, until the stop cam 
46 engages in the axial recess 48 at the front end of the handle part 34 
and adopts its non-twistable work setting which is axially braced relative 
to the handle part 34. If the brush part 32 is intended to be exchanged 
for a different, new brush head, the brush part 32 needs only to be pulled 
by the length of the stop cam 46, counter to the force of the 
pretensioning device 42, axially away from the end face 50 at the front 
end of the handle part 34, in order to unscrew the handle part 34, in the 
opposite direction of rotation, from the thread 44. 
From FIG. 1, it can further be seen that a conical centering, ring 58 is 
disposed, at an axial distance from the thread 44, at the front end of the 
coupling rod 36. In the region of the mouth of the coupling opening 38 in 
the brush part 32, there is provided a correspondingly shaped, 
smooth-walled segment 37 of the coupling opening 38 for receiving the 
centring ring 58. The diameters of the thread 44 and of the centring ring 
58 of the coupling rod 36 are dimensioned larger than that of the stem 62 
of the coupling rod 36, which stem is mounted displaceably in the handle 
part 34. Expediently, the thread 44 and the centring ring 58 exhibit the 
same diameter. The stem 62 is provided, according to FIG. 3, with two 
diametrically opposing, longitudinally extending guide beads 64, 66, which 
are guided axially displaceably into corresponding longitudinal grooves 
68, 70 in the neck 41 and ensure that the coupling rod 36 cannot be 
twisted. 
As further shown by FIG. 2, the sliding bearing 40 in the handle part 34 
for the coupling rod 36 is limited by a transverse wall 72, which serves 
as a stop for an annular shoulder 74 on the inner end of the coupling rod 
36. The transverse wall 72 is provided with an axial bore 76 exhibiting a 
diameter which is smaller relative to the stem 62 of the coupling rod 36. 
Through this bore 76 in the transverse wall 72, a cylindrical guide rod 80 
extends from that end of the stem 62 of the coupling rod 36 forming the 
annular shoulder 74, there being fastened to the outer end of this guide 
rod 80, by means of a frontal, cylindrical projection 84, a locking block 
82. The projection forms an annular shoulder, on which is supported one 
end of a helical compression spring 86, the other end of which bears 
against an annular shoulder forming the axial bore 76 in the transverse 
wall 72. It can thus be seen that the brush part 32 can be pulled by its 
stop can 46 out of the axial recess 48 in the front end of the handle neck 
41, counter to the action of the pretensioning spring 86, and can 
afterwards be unscrewed, by a rotational motion, from the coupling end of 
the coupling rod 36. 
The locking block 82 fastened to the rear end of the guide rod 80 is a 
component part of a securing device 88. The securing device 88 exhibits on 
its top side facing the front side of the toothbrush, i.e. the side of the 
toothbrush against which the thumb of the user bears when the toothbrush 
is in use, a locking lever 90 in the form of a two-sided lever. The 
locking lever 90 is mounted rotatably in a swivel axle 92, which is 
perpendicular to the central longitudinal plane of the handle part 34 and 
which lies in a spigot-shaped bracket 96 jutting up from the inner side of 
a rear wall 94 of the hollow handle part 34 (FIG. 4). Disposed helically 
around the bracket 96 is a pretensioning spring 98, which acts upon that 
side of a feeler arm 100 of the double-armed locking lever 90 facing the 
locking block 82 and acts upon the said locking lever with the aim of 
locking the locking lever 90 with the locking block 82. The feeler arm 100 
extends from the swivel axle 92 to the rear end of the handle part 34, 
whilst a locking arm 102 of the locking lever 90, which locking arm has a 
locking boss 104 at the outer end, is directed towards the brush part 32. 
The locking arm 102 is herein configured tapered in the direction of its 
locking boss on the side 106 facing away from the locking boss, so that 
this rear-sided taper 106 of the locking arm 102 forms with the inner side 
108 of the box-shaped wall 110 of the handle part 34 an acute angle 
opening in the direction of the brush part 32, whenever the locking lever 
90 engages in a transversely running locking groove 112 in the locking 
block 82 and secures the brush part 32 against an axial pull-out motion 
from the neck 41 of the toothbrush. The acute-angled free space allows an 
unlatching motion of the locking arm 102 from the locking block 82, as is 
more accurately described below. 
The feeler arm 100 is provided, on its longitudinal side facing away from 
the locking block 82, with an actuating plate 116 angled-off in the 
direction of the rear wall 94 of the handle part 34. The actuating plate 
116 lies behind an elastically configured wall segment 120, which is 
configured in that wall of the handle part 34 of the toothbrush lying 
opposite the feeler arm 100. The elastic wall segment 120 enables the 
locking lever 90 to be actuated. As is shown in FIG. 5, when pressure is 
applied to the elastic wall segment 120, the elastic wall segment 120 
comes to bear against the actuating plate 116 situated behind it and moves 
the said actuating plate inwards up to the locking block 82, whereupon the 
feeler arm 100 moves laterally past the locking block 82, as is more 
accurately described later. Consequently, the locking arm 102 of the 
locking lever 90 moves away from the locking block 82, so that the locking 
boss 104 is released from the locking groove 112 in the locking block 82. 
The axial motion of the coupling rod 36 connected to the locking block 82 
is thus no longer blocked, thereby enabling the brush part 32 to be pulled 
axially away from the handle part 34 and unscrewed from the thread 44. 
As is shown in particular in FIGS. 6 and 7, that side of the locking block 
82 lying opposite the feeler arm 100 is configured essentially flat at the 
rear end of the said locking block and exhibits a lug 122, which forms on 
the locking block 82 a shoulder 124 which runs straight, in the 
longitudinal direction of the toothbrush, in a rearward direction parallel 
to the central longitudinal axis of the toothbrush or ascends gently in 
the form of a ramp. Towards the end, the locking block 82 thickens out 
such that the surface lying opposite the feeler arm 100 ascends gradually, 
in a region 126, towards the surface of the lug 122, so that the shoulder 
124 thus disappears back to the end of the locking block 82. 
The locking lever 90 is of lamellar configuration in the plane 
perpendicular to the swivel axle 92 and is placed onto the bracket 96 in 
such a way that a feeler pin 128 attached to the rear end of the feeler 
arm 100, in the locking state of the locking lever 90 (cf. FIG. 2), bears 
under pretensioning upon the lug 122 of the locking block 82. The 
pretensioning is achieved by virtue of the fact that, in this position, 
the feeler arm 100 is bent elastically out of the plane lying 
perpendicular to the swivel axle 92 (FIG. 7). 
The shoulder 124 running parallel to the central longitudinal axis or 
ascending gently in the direction of the rear end of the toothbrush forms, 
together with the region 126 ascending perpendicular to the lamellar plane 
of the feeler arm 100, a control cam unit for the feeler pin 128. 
If, as shown in FIG. 5, a pressure is applied to the elastic wall segment 
120 and the feeler arm 100 is thereby moved inwards, the feeler pin 128 
slides over the lug 122 and engages on the shoulder 124 (FIGS. 8, 9). Even 
after the elastic wall segment 120 has been set free, the locking lever 90 
is thus fixed in the setting in which the locking block 82 is freed and 
can be moved axially (FIG. 10). The user, in order to unscrew the brush 
part, is not therefore reliant upon simultaneously pressing onto the 
elastic wall segment 120 and pulling the brush part 32 away from the 
handle part 34, but is able to perform these actuating steps successively. 
Once the brush part 32 is pulled away from the handle part 34, the locking 
block 82, along with the coupling rod 36, also moves to the left in the 
representation of FIG. 10. The feeler pin 128 hereupon slides along the 
shoulder 124 forming a control cam, until it reaches the thickening region 
126. In the region 126, the feeler pin 128, counter to the elastic action 
of the lamellar form of the locking lever 90, is forced back outwards away 
from the locking block 82 (FIG. 11) and thereby disengaged from the 
shoulder 124, so that the locking lever 90 moves, under the action of the 
pretensioning spring 98, into the setting shown in FIG. 12, which setting 
corresponds to the setting of the locking lever 90 in FIG. 2, except that 
the locking boss 104 now bears behind the locking groove 112 against the 
locking block 82, since the latter has, of course, been moved to some 
extent in the direction of the neck 41 in order to screw on a new brush 
part 32. Once, after the new brush part 32 has been screwed on, its stop 
cam 46 has moved back into the axial recess 48 and the locking block 82 
has thus moved to the right in the representation of FIG. 12, the locking 
boss 104 also finally engages in the locking groove 112 of the locking 
block 82 and again reaches the original setting shown in FIG. 2, in which 
the coupling rod 36 is blocked. 
In FIGS. 13 and 14, a second embodiment of a securing device 200 for the 
toothbrush 30 is shown. The neck 41 of the toothbrush consists, in this 
embodiment, of a flexible plastic which, at the front end of the handle 
part 34 facing the brush part 32, is attached to the said handle part. 
Into this neck 41 there is inserted a separate housing 210 for the 
coupling device. In the front segment of the housing 210, the axial 
sliding bearing 40 for the stem 62 of the coupling rod 36, including the 
longitudinal grooves for the guide beads 64, 66, is configured on the stem 
62. The front part of the housing 210 is closed off by the transverse wall 
72. After the transverse wall 72, the housing 210 merges integrally into a 
rear segment surrounding the guide rod 80. 
The securing device 200 comprises, like the securing device 88 of the first 
embodiment, a two-sided locking lever 220, which is rotatable about a 
swivel axle 222 perpendicular to the central longitudinal axis of the 
toothbrush and exhibits a locking arm 224 and a feeler arm 226. The feeler 
arm 226 is provided at its end with an actuating plate 228, which lies 
behind an elastic wall segment 230 in the wall of the handle part 34. The 
swivel axle 222 is located close to the transverse wall 72 and is attached 
to the housing 210. 
The locking arm 224 extends beyond the region of the transverse wall 72 
forward into a notch in the neck region 41 of the toothbrush. A locking 
boss 234 at the outer end of the locking arm 224 engages, in the locking 
state, in a notch 236 in one of the guide beads 64, 66 on the stem 62 of 
the coupling rod 36, which coupling rod is thereby blocked in terms of its 
axial mobility. The locking lever 220 is held in the locking state by a 
pretensioning spring 238, for example, as shown in FIG. 13, a leaf spring. 
The elastic wall segment 230 can be configured in one piece with the neck 
41 of the handle part 34; it then extends up to a hole in the wall of the 
relatively rigid handle part 34 and fills up the hole. 
When pressure is applied to the elastic wall segment 230 and thereby to the 
actuating plate 228, the locking boss 234 is disengaged from the notch 236 
and the coupling rod 36 thereby freed, which coupling rod thus allows the 
stop cam 46 to be pulled out of the axial recess 48 and hence allows the 
brush part 32 to be unscrewed and replaced. 
In FIGS. 15 and 16, a third embodiment of the securing device is shown, 
which is similar to the second embodiment. In this third embodiment, the 
guide rod 80 is provided however with an extension 240, which juts through 
a second transverse wall 242, forming the closure of the housing 210, 
rearwards into the hollow handle part 34. The extension 240 exhibits, in 
the region behind the second transverse wall 242, a circumferential, 
radial notch 244, which serves as a locking groove in which the locking 
boss 234 of the locking arm 224 engages. For this purpose, the swivel axle 
is attached in the proximity of the second transverse wall 242 to the 
housing 210 and the locking arm 224 extends beyond the region of the 
second transverse wall 242 rearwards into the cavity in the handle part 
34. In this embodiment also, the locking lever 220 is moved by means of an 
elastic wall segment 230 in the wall of the handle part 34 and an 
actuating plate 228 on the feeler arm 226. 
In FIGS. 17 and 18, finally, a fourth embodiment of the securing device 200 
is shown. In this securing device also, the guide rod 80 is provided with 
an extension 240, which extends rearwards through the second transverse 
wall 242. The locking arm 224 and the feeler arm 226 of the locking lever 
220 are here however attached to each other at an angle of 90.degree., the 
swivel axle 222 still being situated behind the second transverse wall 242 
and outside the central longitudinal axis of the toothbrush and the feeler 
arm 226 crossing this central longitudinal axis. An axial pressure at play 
in the central longitudinal axis thus enables the locking boss 234 of the 
locking lever 220 to be disengaged from the notch 244 in the extension 
240. The axial pressure is applied to the feeler arm 226 by means of a 
pressure rod 246. The pressure rod 246 runs essentially along the central 
longitudinal axis of the handle part 34. The one end of the pressure rod 
246 is fastened in an articulated manner to the feeler arm 226 and the 
other end thereof lies in an elastic endpiece 248 at the end of the handle 
part 34. When pressure is applied to the elastic endpiece 248, the 
pressure rod 246 moves to the left in the representation of FIG. 17, 
whereby the locking lever 220 is pivoted and the locking boss 234 frees 
the coupling rod 36. 
REFERENCE SYMBOL LIST 
30 toothbrush 
32 brush part 
33 bristle bed 
34 handle part 
36 coupling rod 
37 smooth-walled segment 
38 coupling opening 
39 bristles 
40 axial sliding bearing 
41 neck 
42 pretensioning device 
44 thread 
46 stop cam 
48 axial recess 
50 end face 
58 centring ring 
62 stem of 36 
64,66 guide beads 
68,70 longitudinal grooves 
72 transverse wall 
74 annular shoulder 
76 bore of 72 
80 guide rod 
82 locking block 
84 projection 
86 spring 
88 securing device 
90 locking lever 
92 swivel axle 
94 rear wall 
96 bracket 
98 pretensioning spring 
100 feeler arm 
102 locking arm 
104 locking boss 
106 tapered side 
108 inner side 
110 wall of 34 
112 locking groove 
116 actuating plate 
120 elastic wall segment 
122 lug 
124 shoulder 
126 ascendant region 
128 feeler pin 
200 securing device 
210 housing 
220 locking lever 
222 swivel axle 
224 locking arm 
226 feeler arm 
228 actuating plate 
230 elastic wall segment 
234 locking boss 
236 notch 
238 pretensioning spring 
240 extension of 80 
242 second transverse wall 
244 notch 
246 pressure rod 
248 elastic endpiece