Toothbrush

An interdental toothbrush has a hinged locking retainer on the end of an elongated handle. The locking retainer has a hole which is positioned relative to a groove in the handle so that a twisted wire brush may be locked into place simply by inserting it and closing the retainer. A latch on the locking retainer has a top end with a double cam surface thereon. One of the cam surfaces guides the latch into a locking position as the retainer is closed. The other of the cam surfaces releases the locking retainer when pushed.

This invention relates to handles for interdental toothbrushes, and more 
particularly to toothbrush handles which have a lower cost and which, 
nevertheless, firmly and securely hold a twisted wire brush in place. 
A number of U.S. patents show interdental toothbrushes: U.S. Pat. Nos. 
3,559,226; 4,303,199; 4,222,143; 4,319,377; 4,572,223; 4,691,404; 
4,710,996; and 4,780,923. 
A regular toothbrush is severely limited as to the tooth and gum surfaces 
that it can reach. One importance of brushing includes a cleaning of the 
tooth itself. However, it also includes a massaging of the gums and a 
cleaning of the sulcus or marginal area below the nominal gum line and 
between the tooth and gum. This massaging tends to thicken the gum tissue 
and to make it healthier. 
As a result of these needs, it is common practice to provide a small 
twisted wire brush which may fit within and through the spaces between, 
around, and under teeth, bridges, and the like. This use of a twisted 
brush leads to two problems. One problem is to provide a brush which 
projects from a handle at approximately a right angle thereto. The other 
problem is to securely lock the brush in place at the lowest possible 
cost. The locking is a relatively severe problem since there is a 
substantial leverage acting upon the brushes. The low cost is also a 
relatively severe problem since the field of personal appliances, 
especially toothbrushes, is a highly competitive field. Fractions of a 
cent per unit make the difference between commercial success and failure. 
A conventional toothbrush handle structure is made on automatic plastic 
molding machines, many of which work unattended. For example, it is 
possible to switch on such a machine and then go home for the night. All 
night long, the machine is producing parts with no one present to observe 
the machine in operation. With a use of such convention production 
techniques, the cost of the interproximal handle may also be reduced to 
something in the order of a mere fraction of a cent. 
Another consideration is the convenience for the user. Many people who have 
bridges or a large gap between their teeth, especially at the root line, 
are quite elderly. Their hands may be stiff, their eyesight impaired, etc. 
Thus, there may be many reasons why they find it most difficult to use 
some of the prior art interdental handles where the brush stem has to be 
manipulated. Therefore, the ease of brush installation and replacement is 
also a very important consideration. 
The parent application Ser. No. 07/475,724 shows an automatic locking 
arrangement for capturing the twisted wire brush. However, as good as it 
is, it had some contours which have a little less acceptability than 
expected. These contours enabled a user to put his thumb nail in a slot in 
order to open the brush locking mechanism. Also, the present invention now 
offers improvements in the twisted wire brush locking arrangements. 
Accordingly, an object of the invention is to provide new and novel handles 
for interdental toothbrushes. Here, an object is to reduce cost by making 
a single piece part which provides the above described features. Stated 
otherwise, an object is to eliminate loose parts which must be manipulated 
while holding the brush in position. 
In this connection, an object of the invention is to provide a system 
wherein the brushes may be installed and replaced quickly and easily, even 
by a person having impaired eyesight and with less than completely normal 
facility to use their hands. 
In keeping with an aspect of the invention, these and other objects are 
accomplished by providing an elongated toothbrush handle with a locking 
retainer hinged thereto. A hole in the retainer and a groove in the handle 
receive the twisted wire stem. One only has to pass the twisted wire stem 
through the hole in the retainer and then close it. As the retainer 
closes, the wire stem is captured within the groove. A latch on the 
retainer passes through a hole in the handle, with a positive capture 
latching. When the latch has so passed through the hole, the retainer is 
locked in place with the wire stem of the brush firmly held thereby. The 
top of the latch is shaped so that the twisted wire brush may be released 
by a push button convenience.

The inventive toothbrush is best seen in FIGS. 1-4, as comprising handle 20 
having a locking retainer 22 joined thereto by a double living hinge at 
24. A twisted wire brush is seen at 26. When the locking retainer 22 is 
closed over the handle 20, the brush is firmly locked in place. 
The exterior contours of the handle with the locking retainer 22 closed 
over it are generally smooth with a blended curve so that there are no 
rough or projecting members which may catch or feel rough to the cheek or 
gum tissue. There is no need to provide any thumb nail notches or catches 
in order to facilitate an opening of the locking retainer since there is a 
novel push button opening mechanism. 
The double living hinge 24 includes a member 30 (FIG. 4) having a generally 
triangular cross section with a 90.degree. apex angle and joined on one 
side to the handle 20 by a thin membrane 32 and joined on the other side 
to the locking retainer 22 by a thin membrane 34. The thin membranes 32, 
34 function as the living hinge on which the locking retainer 22 and 
handle 20 pivot relative to each other. The membranes 32, 34 are formed at 
the roots 33 of angles A, B by radiusing a mold at about 0.005-inch. The 
opposite side of the handle has two sharp indentations, as at 35, which 
together form triangular member 30 and which define the undersides of 
living hinges 32, 34. 
The locking retainer 22 has a projecting chimney like member 37 with a hole 
36 formed therein for receiving the stem ST of a twisted wire brush. The 
outer end of the hole 36 is chamfered or beveled at 38 in order to form a 
funnel shaped opening for guiding, directing, and receiving the end of the 
twisted wire brush, to facilitate an insertion thereof. Therefore, wire 
stem ST projects through hole 36 to be bent over to lie in the groove 40. 
A groove 40 is formed preferably in the handle 20 at a location which is 
aligned with the hole 36. The hole 36 and groove 40 may also be at 
reversed locations in a slightly redesigned handle. The end of the wire 
stem ST engages the retainer 22 and is guided to bend and enter groove 40. 
The twisted wire brush stem ST is thus trapped automatically in groove 40 
when the locking retainer 22 is closed, (swung in direction C). 
When the locking retainer 22 is locked in a closed position, the wire stem 
ST is located and locked in position within both the hole 36 and the 
groove 40. At this time the wire stem ST is bent to have a somewhat 
L-shape, with one arm of the "L" locked in groove 40 and the other arm of 
the "L" passing through the hole 36. The brush is on the opposite end of 
the stem arm which passes through hole 36. 
The locking retainer 22 includes an upstanding latch 44 (FIG. 9). A 
corresponding keeper hole 46 (FIG. 3) is positioned in the handle 20 at a 
point which the latch 42 engages as the locking retainer 22 swings from an 
open to a closed position. Once the latch 42 clears the far side of the 
keeper hole 46, the locking retainer 22 is locked into position. As seen 
in FIGS. 2, 9 the latch edge 44 on the top of latch 42 and at the far end 
of keeper hole 46 is a double cam which both helps latch and acts as a 
push button which may be pushed in order to help initiate an opening of 
the retainer. 
The action of the latch 42 may be best understood from a review of FIG. 10. 
Latch 42 comprises a shaft topped by a double cam formed by two beveled 
surfaces S3, S4. The shaft is flexible enough to flex back and forth in 
directions D, E, as the shaft enters and leaves keeper hole 46. The first 
cam or beveled surface S4 causes the shaft to flex in direction E as it 
encounters the perimeter of the keeper hole 46. The memory of the plastic 
is such that after latch 44 passes through keeper hole 46, the latch 42 
returns in direction D, engages and locks over the far edge of the handle 
20 (FIG. 2) at the perimeter of keeper hole 46. 
When the user wishes to release the locking retainer 22, he holds handle 20 
in his hand and presses against surface S3, preferably with his thumb 
nail. As shown in FIG. 10, the downward pressure of the user's thumb nail 
acts on the second cam or beveled surface S3 to exert a downward force F1 
against the top of the shaft. This downward force acts on the cam formed 
by sloping top S3 of latch 42 to produce a horizontal vector F2 which 
flexes the shaft in direction E. As the shaft so flexes, the latch 42 
moves away from the capture position over the far side of the handle 20 
and passes through the keeper hole 46, thus releasing the locking retainer 
22. It should be noted that the back of the latch 42 has a slanted relief 
area R which enables the latch shaft to move back and forth in directions 
D,E, while in the keeper hole 46. 
The construction of the toothbrush handle may become more apparent from a 
study of FIGS. 5-8, which are four cross sections taken at locations 
identified in FIG. 1. As shown in FIG. 5, above the locking retainer 22 
(section line 5--5), the handle is simply a solid piece of molded plastic, 
of any suitable geometric configuration (here circular cross-section). 
At the latching end (section 6--6), the locking retainer 22 (FIG. 6) and 
the handle together form a smooth and substantially uninterrupted contour 
which does not irritate the gum, cheek or other soft tissue inside the 
mouth. That is, since the latch 42 opens with a push button action, it is 
not necessary to provide an opening or thumb nail catch at the parting 
line between handle 20 and locking retainer 22. Such a catch might 
irritate the soft mouth tissue for people. 
Further down the handle (section 7--7) toward the hinged end 24, the 
locking retainer 22 (FIG. 7) and handle 20 have substantially the same 
dimensions to continue the smooth irritation free contour. At this point, 
the groove 40 forms a locking area for receiving the end of the twisted 
wire stem ST when the locking retainer 22 is latched in a closed position. 
Still further down the handle (Section 8--8), the retainer is formed into 
a chimney 37 or extension having a height H which further helps stabilize 
the twisted wire stem ST. Preferably, the height H extends far enough to 
reach the bristles of the brush, thus lessening any tendency for the wire 
stem to bend, at random, during the use thereof. 
Those who are skilled in the art will readily perceive how to modify the 
invention. Therefore, the appended claims are to be construed to cover all 
equivalent structures which fall within the true scope and spirit of the 
invention.