Bicycle spoke rim wheel for tubeless tire

A bicycle spoke rim wheel for a WO type tubeless tire is disclosed having a rim construction which can secure an airtightness, reduce a weight of the wheel, and easily fit a tire. Particularly, a seal material within a recess can be reduced in weight, and mounting of a tire bead on the rim is facilitated by placing the tire bead into the recess. This provides an arrangement, wherein a rim (1) is provided with a diaphragm (5) on a rim outer side (3), a nipple hole (20) of the diaphragm (5) is airtightened by a seal material (24) in the form of a metal tape and, when air is filled into a tubeless tire (37), a soft foam (25) is further bonded to the upper surface of the seal material (24) so that a tire bead portion (38) is readily placed on a bead-seating portion (11), whereby even a thin tire bead portion (38) can be easily sealed, as a result of which the shape of the bead-seating portion from a rim ear portion (7) to a hump portion (12) is curved to enlarge a sealing area, a valve (29) is pressed against the diaphragm (5) through a packing (34) and airtightened, a spoke mounting-hole (23) is bored in thick-wall portion of the rim body surface (18), and a spoke end (28) and a nipple head (26) are received in a hollow portion (8).

TECHNICAL FIELD 
The present invention relates to a bicycle spoke rim wheel having spokes 
extended between a rim and a hub, and particularly to a spoke rim wheel 
for a bicycle on which a tubeless tire can be mounted. 
BACKGROUND OF THE INVENTION 
In general, the spoke rim wheel for a bicycle comprises an annular rim for 
holding a tire, a hub located in the center of the rim to hold the rim on 
a wheel, and spokes for connecting the rim and the hub. The spoke is 
inserted into a mounting hole bored in a flange portion of the hub. A head 
of the spoke is placed in engagement with the mounting hole, and an end 
with a thread tapped is threadedly mounted by a nipple inserted into a 
through-hole bored in a zigzag manner in a peripheral direction of the rim 
from the outer side of the rim, that is, from the side on which a tire is 
put to apply tension to the spoke. Therefore, the through-hole of the rim 
has no airtightness at all, and, since the head of the nipple and the end 
of the spoke project on the outer side of the rim, it is impossible to 
make use of the tubeless tire on the spoke rim wheel. 
Some constructions in which a tubeless tire is used are disclosed in 
Japanese Utility Model Application Laid-Open Nos. S50-134857, S50-134858, 
and S51-156147 Publications. In these constructions, spoke-mounting 
tongues are provided over the entire periphery on the inner side of the 
rim; that is, on the spoke-mounting side, the tongues being bored with 
spoke-inserting through-holes. However, these constructions are 
complicated, and besides, since tightening of spokes is done in a special 
way, the operation for applying tension to the spokes is cumbersome. 
On the other hand, other constructions are disclosed in Japanese Utility 
Model Publication No. S35-29401 Publication and Japanese Utility Model 
Application Laid-Open No. S48-64903 Publication. In these constructions, 
airtightness means using a special seal material is employed in order to 
close through-holes into which spokes are inserted, the holes being bored 
in a zigzag manner on the outer side of the rim. However, even if these 
seal materials are used, since the head of the nipple mounted on the rim 
or the end of the spoke comes in contact with the seal material, the head 
of the nipple or the end of the spoke pushes up or laterally moves the 
seal material due to complicated vibrations in all directions received 
during running, posing an inconvenience that the airtightness fails to 
hold due to the generation of breakage, deviation, peeling, and the like, 
of the seal material. 
For overcoming such an inconvenience as described above, there is proposed 
means as disclosed in Japanese Patent Application Laid-Open No. H7-112601. 
This means is constructed such that a dovetailed tenon groove is provided 
in a rim, a rubber band is disposed in the groove, a protrusion internally 
projecting from the rim forms a bead seat of a tire 5, that is, a 
bead-seating portion, and a tire bead extends internally from the 
bead-seating portion of the rim so that the bead is partly supported on 
the upper surface of the rubber band disposed in the groove to press the 
rubber band so as to maintain the airtightness. The means disclosed in 
that publication has a construction capable of securing the airtightness. 
However, since the tire bead is partly supported on the upper surface of 
the rubber band provided in the groove, the tire bead need be widened. In 
addition, when the tire is fitted in the rim, the extreme end of the bead 
required to fit the tire cannot be temporarily moved into the groove 
because the groove is filled with the rubber band and the tire bead is 
wide, as described above, thus posing an inconvenience that the tire is 
difficult to mount on the rim, and the thick rubber band causes the weight 
of the wheel to increase. 
The present invention is to solve the problem as noted above. The invention 
provides a bicycle spoke rim wheel for a tubeless tire of the wire-on type 
(so-called "WO Type"), in which airtightness can be maintained positively, 
the entire wheel can be reduced in weight, and mounting of tire on the rim 
can be done easily; and further, means is provided in which a seal 
material within a groove that is, a recess can be reduced in weight, and 
movement of a tire bead into the recess is enabled. 
SUMMARY OF THE INVENTION 
Technical means of the present invention taken to solve the problem noted 
above will be explained below: 
(1) A diaphragm is provided on a rim, a nipple hole formed in the diaphragm 
is sealed by a tape-like seal material and airtightened; 
(2) the tape-like seal material comprises a thin and flexible metal tape; 
(3) a flexible foam is mounted on the metal tape so that a tire bead 
portion is easily placed on a bead-seating portion of the rim when air is 
filled in a tubeless tire; 
(4) the shape of the rim from an ear portion to a hump portion of the 
bead-seated portion of the rim is curved to enlarge a sealing area in 
order to facilitate sealing even the tin (that is, narrow) 
tire bead; 
(5) a pneumatic valve is pressed and airtightened against the diaphragm 
through a packing formed of an elastic rubber material or an elastic 
plastic material; and 
(6) a thick-wall portion of the rim-body surface is bored with a 
through-hole, and a spoke end and a nipple head are received into a hollow 
portion. 
The foam used in the present invention is a foam formed of a rubber 
material or a plastic material, which has an elasticity and has a 
restoring force even if it is compressed, preferably a urethane resin 
foam. 
According to a first aspect of the present invention, there is provided a 
bicycle spoke rim wheel for a tubeless tire of the wire-on type, the wheel 
comprising a spoke mounting wall 4 on a rim inner side 2, a diaphragm 5 on 
a rim outer side 3, left and right rim side walls 6, and left and right 
ear portions 7 standing upright from the rim side walls 6 toward the rim 
outer side 3, wherein an internal region surrounded by the diaphragm 5 on 
the rim outer side 3, the rim side walls 6, and the spoke mounting wall 4 
on the inner side 2 is formed into a hollow portion 8. The diaphragm 5 on 
the rim outer side 3 has, in symmetry of a rim center 10, a bead-seating 
portion 11 extending substantially horizontally from left and right ear 
rising portions 9 toward a rim center 10, and a recess 13 recessed from a 
hump portion 12 closer to the rim center 10 of the bead-seating portion 11 
to the spoke-mounting wall 4. A plurality of nipple holes 20 are 
peripherally equidistantly formed in the recess 13, the spoke-mounting 
wall 4 being formed with a spoke-mounting hole 23 in alignment with each 
nipple hole 20 and into which a nipple 21 and a spoke end 28 are inserted. 
A nipple head 26 is mounted on the spoke mounting wall 4 in the hollow 
portion 8 through the nipple hole 20 of the recess 13. A valve head 32 of 
a valve 29 for filling air into a tubeless tire 37 is disposed on the 
diaphragm 5 of the recess 13. The valve body 33 is inserted into a valve 
hole 31 formed in the spoke mounting wall 4, and a nut 36 is tightened. 
According to the invention a tape-like seal material 24 is pasted to the 
diaphragm 5 of the recess 13 to seal the nipple hole 20. A plate-like foam 
25 having a width of substantially a bottom 15 of the recess 13 and a 
height substantially of the height of recess 13 is pasted on the tape-like 
seal material 24 of the recess 13. A packing 34 is disposed between the 
valve head 32 and the peripheral wall of the valve hole 30 of the recess 
13 to press the valve head 32 against the diaphragm 5 of the recess 13 so 
as to make the valve hole 30 airtight. 
According to a second aspect of the present invention, the bicycle spoke, 
rim wheel for a tubeless tire according to the first aspect has the shape 
of the bead-seating portion 11 curved inward to the spoke mounting wall 4 
from the rim ear portion 7 to the hump portion 12 to enlarge a sealing 
area of a tire bead portion 38.

The embodiment of the present invention will be described in detail with 
references to FIGS. 1 to 6. 
A rim 1 capable of mounting or fitting a wire-on (WO) type tubeless tire 37 
according to an embodiment of the present invention comprises a rim in 
sectional shape shown in FIG. 1. In the section of the rim 1 shown in FIG. 
1, suppose that the side on which the tubeless tire 37 is mounted is a rim 
outer side 3, and the side on which a hub is located is a rim inner side, 
the sectional shape of the rim comprises a spoke mounting wall 4 on the 
rim inner side 2, a diaphragm 5 on the rim outer side 3, left and right 
rim side walls 6, 6, and left and right ear portions 7, 7 standing upright 
from the rim side walls 6, 6 and extending toward the rim outer side 3. An 
internal region surrounded by the diaphragm 5 on the rim outer side 3, the 
left and right rim side walls 6, 6 and the spoke mounting wall 4 on the 
inner side 2 is formed into a hollow portion 8. The diaphragm 5 on the rim 
outer side 3 forms a bead-seating portion 11 extending substantially 
horizontally from an ear-rising portion 9 toward a rim center 10. A recess 
side wall 14 depends from a hump portion 12, i.e., an end closer to the 
rim center 10 of the bead-seating portion 11, on the obliquely downward 
rim side wall 6 side by about half the height of the hollow portion 8, and 
a recess bottom 15 extends horizontally in a direction of the rim center 
10 to constitute the diaphragm 5 in symmetry of the rim center 10. That 
is, the rim center 10 of the diaphragm 5 is formed with a recess 13 in 
which a lateral width of the recess bottom 15 is approximately 1/3 of a 
lateral width of the rim, and there is a difference in level between the 
bead-seating portion 11 and the recess bottom 15 to form the diaphragm 5. 
In other words, in FIG. 1, the sectional shape of the rim is that of 
substantially U-shaped portions 17 comprising the bead-seating portion 11 
on the rim outer side 3, the rim side walls 6, 6 of both left and right 
sides, and the spoke mounting wall 4 on the rim inner side 2 is 
symmetrical to the left and right in the rim section. The recess 13 is 
continuous and coexisting with the bead-seating portion 11 of the rim 
outer side 3 and is provided in the rim center 10. And the spoke-mounting 
wall 4 on the rim inner side 2 is formed below of the recess 13 being 
spaced therefrom by the hollow portion 8. On the other hand, the left and 
right side walls 6, 6 are formed with the ear portions 7, 7 which extend 
upward and within which the tire bead portions 38 are fitted. 
The bead-seating portion 11 is a portion on which the tire bead 38 having a 
bead wire 39 of the tubeless tire 37 is placed when the WO type tubeless 
tire 37 is mounted on the rim 1 and filled with air. This bead-seating 
portion 11 is curved from the top area toward the bottom of the spoke 
mounting wall 4. An end closer to the rim center 10 of the bead-seated 
portion 11 forms a hump portion 12. The recess 13 recessed from the hump 
portion 12 is formed at a position of the rim center 10 and 
circumferentially of the rim 1. The hump portion 12 which forms also an 
upper end of the slightly inclined side wall 14 of the recess 13 slightly 
projects toward the rim outer side 3. The slightly projected hump portion 
12 has a function to prevent the tire bead portion 38 of the tubeless tire 
37 placed on the bead-seating portion 11 from falling into the recess 13. 
The spoke-mounting wall 4 is formed, while depicting an arc slightly 
inflated toward the rim inner side 2, between the lower ends of the rim 
side walls 6, 6 below the left and right ear portions 7, 7 of the rim 1. 
The central portion of the body surface 18 of the spoke mounting wall 4 is 
formed in the thick-wall portion 19 in order the resist to tension of the 
mounted spoke 22. In the rim 1 shown in FIG. 1, the thick-wall portion 19 
is formed toward the hollow portion 8 in the rim. Alternatively, the 
thick-wall portion 19 can be provided while being projected in the 
direction of the hub from the body surface 18, unlike the above-described 
embodiment. 
As can be seen in FIG. 2, the body surface 18 of the spoke-mounting wall 4 
on the rim inner side 2 is bored with a spoke mounting hole 23 in the form 
of a through-hole for inserting the spoke 22 through a nipple 21 at a 
suitable pitch at equal intervals in the peripheral direction of the rim. 
Further, the recess bottom 15 of the recess 13 formed in the diaphragm 5 
on the rim outer side 3 is bored with a nipple hole 20 in the form of a 
through-hole for inserting the nipple 21. In the present embodiment, these 
through-holes bored in the recess bottom 15 of the recess 13 formed in the 
diaphragm 5 on the rim outer side 3 and the body surface 18 of the spoke 
mounting wall 4 are coaxially aligned, and a set of through-holes of the 
nipple hole 20 and the spoke-mounting hole 23 receives the nipple 21 and 
the spoke 22. Accordingly, the axes of one set of through-holes of the 
nipple hole 20 and the spoke-mounting hole 23 are inclined to be adapted 
to a degree of inclination of the spokes 22 extended from the hub. About a 
set of through-holes which are both nipple 20 and spoke-mounting holes 23, 
the size of nipple hole 20 located in the recess bottom 15 of the recess 
13 formed in the diaphragm 5 on the rim outer side 3 is larger in diameter 
than that of the nipple head 26 and the size of spoke-mounting hole 23 is 
smaller in diameter than that of the nipple head 26 and is larger in 
diameter than that of a nipple shaft portion 27. Accordingly, when the 
nipple 21 is mounted on the rim 1, the nipple 21 is dropped and inserted 
into the spoke-mounting hole 23 bored in the body surface 18 of the spoke 
mounting wall from the nipple hole 20 bored in the recess bottom 15 to the 
recess 13. As a result, the nipple head 26 is placed on the annular wall 
of the spoke mounting hole 23 bored in the body surface 18 of the spoke 
mounting wall 4 in the hollow portion 8. Accordingly, when the spoke 22 is 
mounted, the nipple head 26 and the end 28 of the spoke 22 are received in 
the hollow portion 8 between the diaphragm 5 on the rim outer side 3 and 
the spoke-mounting wall 4. 
On the rim outer side 3 of the recess bottom 15 of the recess 13 in which 
the nipple head 26 is inserted into the hollow portion 8, the nipple hole 
20 of the recess bottom 15 is blocked and sealed by a seal material 24 of 
the metal tape which is slightly wider than the width of the recess bottom 
15. The metal tape may be formed of an aluminum foil or a stainless steel 
foil and may have adhesives applied thereto, and the sides of the seal 
material 24 extending sideways from the recess bottom 15 are pasted to the 
left and right recess side walls 14, 14. While in the foregoing, the seal 
material 24 is formed of metal, it is to be noted that a high hardness 
elastomer other than metal can be used. Of course, the seal material 24 is 
preferably of a material having a high barrier property without being sunk 
into the nipple hole 20 under the internal pressure of a tire, and having 
a wall-thickness of not more than 2 mm. Preferably, the seal material 24 
is thin due to the influence on the whole weight of a tire or the fitting 
of the extreme end of the tire bead portion 38 into the recess 13 when the 
tire is fitted. 
Further, a plate-like foam 25, formed of urethane or rubber, having a 
thickness corresponding to substantially a depth or a height of the recess 
13 and having a width of the recess 13 and which is elastic and soft is 
bonded by means of an adhesive to the upper surface of the tape-like seal 
material 24 on the recess bottom 15. The foam 25 has a width which covers 
not less than 90 percent of the width of the recess 13; that is, the width 
between the upper ends of the recess side walls 14, 14, and has a height 
which is not lower than not less than 2 mm from the height of the hump 
portion 12; that is, from the upper end of the recess side wall 14. The 
foam 25 has an open cell structure. When the width of the foam 25 is less 
than 90 percent of the recess 13, or lower than 2 mm, or more from the 
height of the hump portion 12, a clearance between the tire bead portion 
38 and the foam 25 is large when the tire is fitted so that when air is 
filled, it is difficult to place the tire bead portion 38 on the 
bead-seating portion 11. Further, in the case in which the foam has a 
closed cell structure instead of open one, when the tubeless tire 38 is 
fitted, the foam 25 is more rigid, that is, the foam 25 is difficult to 
compress and the fitting is not easy. 
As can be seen in FIG. 3, the somewhat narrow tire bead portion 38 of the 
tubeless tire 37 fitted in the ear portion 7 of the rim 1 has a bead wire 
39 therein and is inflated circumferentially outward and downward, and the 
inflated tire bead portion 38 is placed on the circumferentially curved 
bead-seating portion 11 of the diaphragm 5 of the rim 1. 
As can be seen in FIG. 4, the valve 29 to inject air to the tubeless tire 
37 consists of valve head 32 having an air fitting port 35 in its center, 
a plate-like packing 34 about the valve head 32 combined with elastic 
rubber or elastic plastic material or broader area than the bottom of 
valve head 32 and an axial valve body 33 having a thread formed on the 
cylindrical surface thereon, and the said valve 29 penetrates the rim 1. A 
nut 36 for fastening the spoke-mounting wall 4 from the rim inner side 2 
is threadedly engaged with the thread of the valve body 33. 
This valve 29 is provided internally of the recess 13 and is capable of 
being attached from the other side of the spoke-mounting wall 4 by means 
of the nut 36 when the valve is extended through the packing 34 formed of 
a rubber material or a plastic material. The valve body 33 extends through 
a valve hole 30 bored in the recess bottom 15 and a valve hole 31 bored in 
the body surface 18 of the spoke-mounting wall 4 coaxial with the valve 
hole 30. The valve body 33 projects toward the hub in the ring center of 
the rim 1. Further, the packing 34 is formed to have the same shape as the 
sectional shape of the recess 13 of the diaphragm 5 on the rim outer side 
3, and a hole through which the valve body 33 passes extends through the 
center thereof. 
In manufacturing the bicycle spoke rim wheel for a tubeless tire 
constructed as described above, first, a rim stock formed of extended 
extruded material made of a light alloy and having a sectional shape of 
the rim 1 is curved into a ring-like configuration while maintaining the 
shapes of the ear portion 7, the diaphragm 5 and the body surface 18 of 
the rim 1 by means of a roll. The rim stock is then cut into a fixed 
length as a wheel with the peripheral edge length along the bead-seating 
portion 11 being a reference, and the cut ends abutted and welded to 
obtain an endless ring-like rim 1. 
Next, the head of each spoke 22 is inserted into, and engaged with, the 
spoke-mounting hole 23 of the hub. The thus inserted spoke being loose, 
the thread formed in the end 28 of the spoke 22 extends to the inside of 
the spoke-mounting hole 23 bored in the body surface 18 of the rim, and 
the nipple shaft portion 27 of the nipple 21 is inserted, from the side on 
the rim outer side 3, into the nipple hole 20 bored in the recess bottom 
15 in the recess 13 of the diaphragm 5. The nipple head 26 is dropped into 
the hollow portion 8 with the nipple shaft portion 27 protruded from the 
spoke-mounting hole 23, and the thread of the end 28 of the spoke 22 is 
loosely tightened at the nipple shaft portion 27. The rim 1 is rotated to 
perform a similar operation, and the threads of the remaining spokes 22 
are loosely tightened at the nipple shaft portion 27. 
The spokes 22 and the nipple in the loosely tightened state are then 
finally tightened to complete the spoke tightening. Next, as shown in FIG. 
4, the valve body 33 having the packing 34 inserted therethrough 
penetrates the valve hole 31 of the body surface 18 of the spoke-mounting 
wall 4 from the valve hole 30 of the recess 13. The valve head 32 is 
pressed on the recess bottom 15 side of the peripheral edge of the valve 
holes 30 to hold the packing 34 in the recess bottom 15, and the nut 36 is 
threadedly engaged with the valve body 33 projected from the body surface 
18. The nut 36 is screwed to press the valve head 32 against the recess 
bottom 15, and the valve hole 30 of the recess 13 is closed by the packing 
34 to complete sealing of the valve hole 30, as shown in FIG. 5. Next, as 
shown in FIG. 6, both left and right edges in the circumferential 
direction of the ring of the rim 1 of the packing 34 of the valve 29 are 
used as a start point and a terminal point, respectively, the tape-like 
seal material 24 formed of metal, for example, an aluminum foil, which is 
somewhat wider than the width of the recess bottom 15 of the recess 13 
formed in the periphery of the ring is bonded to the entire peripheral 
region of the recess 13 over the recess side walls 14, 14 on both sides 
from the recess bottom 15 to seal all the nipple holes 20 formed at equal 
intervals in the recess bottom 15. Further, the plate-like foam 25 having 
the width of the recess bottom 15 and the depth of the recess 13, for 
example, a urethane foam, is bonded to the upper surface of the 
thus-bonded seal material 24 of the recess 13 by means of adhesives to 
complete the closure by way of blocking of the nipple holes 20 in the 
entire periphery of the ring of the rim. 
Subsequently, the tubeless tire 37 is fitted in the rim 1, the tire bead 
portion 38 on one side of the tubeless tire 37 being placed on the foam 
25, and the tire bead portion 38 on the other side then also placed on the 
foam 25. Both the tire bead portions 38, 38 press the foam 25 against the 
recess bottom 15, but the tire bead portions 38, 38 are to be positioned 
upward of the recess side walls 14, 14 of the recess 13 by the restoring 
force of the foam 25. In this state, finally air is filled in the tubeless 
tire 37 from the air filling port 35 of the valve 29 to thereby elevate 
air pressure in the tubeless tire 37, and by the elevation of the air 
pressure, the tire bead portions 38, 38 of the tubeless tire 37 are 
automatically moved in a lateral direction by the expansion thereof, and 
placed on the bead-seating portions 11, 11 to complete the bicycle spoke 
rim wheel for a tubeless tire. 
As described above, the present invention provides a bicycle spoke rim 
wheel for a tubeless tire in which a region surrounding a diaphragm on the 
rim outer side, a rim side wall, and a spoke mounting wall on the rim 
inner side is formed into a hollow portion. A recess is formed in a center 
portion of the diaphragm. The diaphragm is of a two-stage construction so 
that the bead-seating portion on the upper stage is somewhat curved to 
slightly project a hump portion of the end thereof toward the rim outer 
side. A tape-like seal material such as a metal foil, is pasted to the 
recess bottom, and a plate-like foam, which has an elasticity and is soft, 
such as urethane foam, is further bonded onto the seal material. Thus the 
present invention exhibits the following effects: 
(1) A conventional tubeless tire can be mounted on the bicycle spoke rim 
wheel. 
(2) The spoke end projecting on the rim outer side and the nipple head are 
positioned within the hollow portion, and since these are not in contact 
with the seal material, the airtightness can be held positively without 
occurrence of breakage, deviation and peeling of the seal material. 
(3) Since the foam is further bonded to the upper surface of the seal 
material bonded within the recess, the tire bead portion is not in direct 
contact with the seal material when the tubeless tire is fitted. 
Therefore, the breakage of the seal material caused by the tire bead 
portion is prevented so that the airtightness can be secured. 
(4) Since the foam has an elasticity, is expansile and has a restoring 
force, in the case in which, when the tubeless tire is mounted on the rim, 
the tire bead portion on one side is first moved into the recess, the foam 
can be pressed and contracted to sink the tire bead portion in the 
vicinity of the recess bottom. Therefore, the other tire bead portion is 
very easily fitted in the rim, and workability of tire fitting is 
excellent. 
(5) In the case in which, when the tubeless tire is fitted in the rim, both 
the tire bead portions are placed on the recess, the tire bead portions 
are raised up to the neighborhood of the upper end of the recess side wall 
by the restoring force of the foam. Therefore, when air is filled from the 
valve into the tubeless tire fitted in that state, the tire bead portions 
are easily placed on the bead-seated portion continuous to the ear portion 
of the diaphragm to provide complete fitting of the tire. 
(6) The bead portion is formed into a circumferentially curved shape to 
enlarge a contact area between the bead-seating portion and the tire bead 
portion, that is, a sealing area. Therefore, even a tubeless tire having a 
thin, that is, narrow tire bead portion can fully secure airtightness, 
thus reducing the weight of the whole wheel. 
(7) A thin metal tape is used as a seal material, and the seal material in 
the form of a metal tape and the fitting of the tire bead portion is 
facilitated as described above, whereby the light-weight foam and the 
light-weight vehicle can be obtained.