Method of securing a blade for a torque converter

A method of securing a blade to a torque converter for use mainly in industrial construction vehicles provides a rigid and easy-to-manufacture construction. The structure includes plural circular blades which are secured to a concave surface of a shell with some space in the circumferential direction, and a core ring which extends along the circumferential direction of the shell and is secured to concave peripheries of the blades. A tab fitting in a slot of the shell is formed integrally on the convex periphery of the blade. A tab fitting in a slot of the core ring is formed integrally on the concave periphery of the blade. Ribs extending in the circumferential direction of the shell are only formed on both ends of the convex periphery and concave periphery of the blade. The convex periphery and the concave periphery are brazed to the shell and the core ring respectively.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates mainly to a securing structure of a blade for a 
torque converter for use in industrial construction vehicles such as a 
fork lift truck etc., and especially to a securing structure and a method 
of securing a blade. 
2. Description of the Invention 
As illustrated in FIG. 9 and FIG. 10, a torque converter 100 for use in 
industrial construction vehicles generally has such a structure that 
plural metal blades 102 formed into annular shape (each one is shown in 
FIG. 9 and FIG. 10 respectively) are installed on a concave surface of a 
turbine shell 101, flanges 103 and 104 extending in opposite directions 
with each other along the circumference of the shell 101 are formed 
integrally and entirely on a convex periphery and a concave periphery of 
the blade 102, respectively. The flange 103 and 104 are tacked to the 
surface of the shell 101 and the outside surface of a core ring 105 by 
spot welding, respectively. 
However, in such a structure, dispersion of installing distance and 
position of the blade 102 may occur because of the difficulty for locating 
the blade 102. The spot welding may also be impossible in some 
configurations of the blade 102, so that hand work must be employed. Thus, 
the manufacturing cost has been expensive. Moreover, the formation of 
these flanges 103 and 104 formed entirely on the convex and concave 
peripheries has increased the total weight of the whole torque converter. 
The formation would affect a flow of fluid (working oil). 
Therefore, in recent years, a securing structure of blade to a torque 
converter 120 (only a turbine portion is shown) for use in a general 
passenger car has been adopted for industrial construction vehicles. 
Such structure includes plural circular blades 122 which are secured to a 
concave surface of a shell 121 with some space in the circumferential 
direction. A core ring 123 is secured to a concave periphery of the blade 
122 and extends along the circumferential direction of the shell 121. 
Slots 126 and 127 in which tabs 124 and 125 of the blade 122 are fitted 
are formed in the shell 121 and the core ring 123 respectively. An inlet 
portion X1 of the convex periphery of the blade 122 is tacked by brazing 
when a turbine wheel is assembled, and then the convex periphery of the 
blade 122 and concave periphery are brazed. 
The structure has an advantageous feature in that positioning of each blade 
can be done easily when tacking by brazing. However, in the industrial 
construction vehicles such as fork lift trucks, special large loads must 
be required because changes of forward/backward shifting are carried out 
more frequently than in general vehicles such as a passenger car, and the 
turbine wheel may rotate in the reverse direction when the change of 
forward/backward shifting is carried out. It has been ascertained by 
experiments that, when the above-mentioned structure of the torque 
converter 120 is applied to this type of vehicle, a crack 130 as shown by 
FIG. 12 will be produced because of the excessive large torque load 
transmitted to the portion adjacent to an inlet of the blade 122. When the 
thickness of the blade 122 is increased in order to avoid the above 
trouble, a collision loss of fluid becomes large because a pressure area 
of the inlet of the blade 122 denoted by 131 increases (FIG. 13). The 
pressure area of the outlet of the blade 122 denoted by 132 also becomes 
large, so that eddies 133 (FIG. 14) may occur at the place adjacent to the 
fluid outlet end face 132 causing cavitation. 
An object of the present invention is to solve the above-mentioned problems 
by employing ribs which extend in a circumferential direction of the shell 
and are only formed on both ends of the convex periphery and concave 
periphery of the blade, and by brazing the convex periphery and concave 
periphery to the shell and the core ring respectively. 
SUMMARY OF THE INVENTION 
In order to solve the foregoing trouble, this invention provides a securing 
structure for a blade for a torque converter including plural circular 
blades which are secured to a concave surface of a shell with some space 
in a circumferential direction, a core ring which is secured to the 
concave peripheries of the blades and extends along the circumferential 
direction of the shell, a tab fitting in a slot of the shell integrally on 
the convex periphery of the blade, and a tab fitting in a slot of the core 
ring formed integrally on the concave periphery of the blade; ribs 
extending in the circumferential direction of the shell are formed on 
opposite ends of the convex periphery and opposite ends of the concave 
periphery of the blade. The convex periphery and concave periphery of the 
ribs are brazed to the shell and the core ring respectively. 
A securing method of a blade for a torque converter according to the 
invention includes a process comprising the steps of disposing the shell, 
in which slits have previously been formed, horizonally on its back; 
disposing the blade, which integrally has tabs on the concave periphery 
and convex periphery and has ribs only on both ends of the peripheries, on 
the shell so as to place the convex periphery of the blade so as to face 
the concave surface of the shell and fit the tabs formed on the convex 
periphery of the blade in the slots of the shell; bending the tabs on the 
convex periphery of the blade onto the outside face of the shell to locate 
the blade; securing the blades together with the ribs of the convex 
periphery to the shell by brazing and disposing the core ring on the 
concave peripheries of the blades in a horizontal position, fitting the 
tab formed on the concave periphery of the blades in the slots of the core 
ring, bending the tab formed on the concave periphery of the blades onto 
an inside face of the core ring, and brazing the core ring to the blade 
assembly. 
Function 
The tab, formed integrally on the convex periphery of the blade, is fitted 
in the slot of the shell, and then bent onto the outside face of the shell 
to be tacked thereto. 
The ribs, formed integrally on the convex periphery of the blade, are 
brazed to an inside face of the shell after the above-mentioned tacking. 
The tab, formed integrally on the concave periphery of the blade, is first 
fitted in the slot of the core ring, and then bent onto an inside face of 
the core ring to be tacked thereto. 
The ribs, formed integrally on the concave periphery of the blade, are 
brazed to an outside face of the core ring after the above-mentioned 
tacking.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 showing an embodiment of the present invention, 10 is an input 
shaft of engine, 11 is an output shaft (only its center line is shown) 
which is the input shaft of a transmission, 13 is a flywheel formed 
integrally around the input shaft 10, 14 is a front cover, one end of 
which is secured integrally to the flywheel 13, and the other end of which 
is secured integrally to one end of an impeller shell 16 of a pump wheel 
15. 17 is a turbine wheel, 18 is a turbine shell, 19 is a core ring, 20 is 
a hub which spline fits onto the output shaft 11, 21 is an outward hub 
flange extended integrally around the hub 20, 22 is a rivet fastening an 
outlet end of the turbine shell 18 on the hub flange 21, 23 is a stator, 
24 is an one-way clutch, and 25 is an inner race carrying the one-way 
clutch. The inner race 25 spline fits onto a fixed shaft not shown in the 
figure. 
Many slits 26 and 27 are formed, respectively, in the turbine shell 18 and 
in the core ring 19 with equal space in the circumferential direction. 
Tabs 29 and 30, which are formed into corresponding annular shapes 
respectively, of a blade 28 made of sheet metal fit in the slits 26 and 
27. 
The tabs 29 and 30 are formed simultaneously together with inlet side ribs 
31 and 32 and outlet side ribs 33 and 34 by the press work for producing 
the blade 28. The ribs 31, 32, 33 and 34 are only formed on both end 
portions of a convex periphery 35 and a concave periphery 36 of the blade 
28, respectively. 
As illustrated in FIG. 2, 3 and 4, the ribs 31, 32, 33 and 34 stretch along 
the circumference direction of the shell 18. In this embodiment, the ribs 
31 and 33 formed integrally on opposite ends of the convex periphery 35 
(FIG. 2) are so formed as to extend in the opposite direction to the ribs 
32 and 34 formed integrally on opposite ends of the concave periphery 36 
(FIG. 2), so and as to extends to a concave surface 28a side of the blade 
28. The ribs 32 and 34 are so formed so as to extend to a convex surface 
28b side of the blade 28. 
The assembly process will be described hereunder. 
Firstly, as illustrated in FIG. 5, the shell 18 previously provided with 
slits 26 is supported horizonally by a gauge 40 on its back. 
Secondly, as illustrated by an upper part of FIG. 6, the blade 28 is 
provided integrally with the tabs 29 and 30 and ribs 31, 32, 33 and 34 
formed by a press work, for example, and is so disposed that the convex 
periphery 35 is faced to the concave surface 37 of the shell 18, and the 
tabs 29 are fitted in the slits 26 of the shell 18. 
Thirdly, as illustrated by FIG. 7, the tabs 29 are bent onto the outside 
face of the shell 18 to locate the blade 28, and then the blade 28 is 
secured to the shell 18 by a brazing work. The ribs 31 and 33 formed 
integrally on the convex periphery 35 are also secured to the concave 
surface 37 of the shell 18 by the brazing work. As described above, this 
invention employs the structure which enable the tabs 29 formed on the 
convex periphery 35 first to fit in the slots 26 of the shell 18 and then 
to be bent onto the outside face of the shell 18, so that the blade 28 can 
be located easily when installing the blade on the shell 18. Further, 
because the ribs 31 and 33 are only formed on the opposite ends of the 
convex periphery 35 of the blade 28, they do not affect the flow of 
working oil. Moreover, because the ribs 31 and 33 are secured very 
rigidly, there is no fear of occurrence of cracks in the vicinity of the 
blade 28 inlet to which frequent stress is applied. 
Finally, as shown in an upper part of FIG. 7, the core ring 19 is disposed 
on the concave peripheries 36 of the blades 28 in the horizontal position, 
each of tabs 30 is first fitted in each of slots 27 of the core ring 19, 
and then bent onto and brazed to the inside face of the core ring 19, thus 
secure the core ring 19 to the blade assembly to complete the final 
structure as shown by FIG. 8. Further, the ribs 32 and 34 formed 
integrally on the concave periphery 36 of the blade 28 are brazed firmly 
to the outer peripheral surface of the core ring 19 by the brazing work. 
Also in this process, the tab 30 formed on the intermediate portion of the 
concave periphery 36 is first fitted in the slot 27 of the core ring 19 in 
the same way as the process shown by FIG. 5 and FIG. 6, so that it becomes 
easy to locate the core ring 19 and improve the securing strength of the 
core ring 19 by the ribs 32 and 34. 
Function will be described refering to FIG. 1. 
When an engine torque is transmitted to the input shaft 10, the torque is 
transmitted through the flywheel 13, the front cover 14 and the impeller 
shell 16 to the pump wheel 15, therby working oil from an oil pump not 
shown in the figure is driven, and the working oil flows to the turbine 
wheel 17 side to transmit the torque to the turbine wheel 17. The torque 
is transmitted from each blade 28 to the output shaft 11 through the 
turbine shell 18, the hub flange 21 and the hub 20. In the above-mentioned 
function; the stator 23 stands until the speed ratio reaches a clutch 
point, and then the stator 23 rotates on the one-way clutch 24 relatively 
to the not shown fixed shaft onto which the inner race 25 fits, when the 
speed ratio exceeds the clutch point. 
During the above operation, the blades 28 of the turbine impeller 17 
recieve a large load of the working oil. Especially in the industrial 
construction vehicles, the turbine wheel 17 frequently rotates in the 
reverse direction during the forward/backward shifting operation of the 
vehicle, so that the load becomes particularly large in this instance. In 
the present invention, however, the ribs 31, 32, 33 and 34 extending along 
the circumference of the shell 18 are only formed integrally on the convex 
periphery 35 and the concave periphery 36 of the blade 28. The convex 
periphery 35 and concave periphery 36 are brazed to the shell 18 and the 
core ring 19 respectively. Therefore, a sufficient durability of the blade 
28 can be maintained by these ribs 31, 32, 33 and 34 even if the blade is 
made of the thin steel plate. 
Effect of the Invention 
As described above, according to the present invention, the ribs 31, 32, 33 
and 34 extending along the circumference of the shell 18 are only formed 
integrally on the opposite ends of the convex periphery 35 and the concave 
periphery 36 of the blade 28, and the convex periphery 35 and concave 
periphery 36 are brazed to the shell 18 and the core ring 19 respectively; 
so that, in the assembly process, the tabs 29 formed integrally on the 
convex periphery 35 of the blade 28 are first fitted in the slots 26 of 
the shell 18 and then bent onto the outside face of the shell 18 to be 
tacked thereto. Further, when secure the core ring 19, the tab 30 formed 
integrally on the concave periphery 36 of the blade 28 is first fitted in 
the slot 27 of the core ring 19 and then bent onto the inside face of the 
core ring 19 to be tacked thereto. Accordingly, the tacking work becomes 
very easy and the efficiency of the assembly work can be improved. 
Moreover, according to the present invention, because ribs 31 and 32 having 
high securing strength are formed on the opposite ends of the blade 28, 
there is no fear of occurrence of cracks in the vicinity of the blade 28 
inlet to which frequent stress is applied. Furthermore, because the ribs 
31, 32, 33 and 34 are only formed on the opposite ends of the peripheries 
35 and 36, they do not affect the flow of working oil. The total weight 
can be reduced by an amount of omitted intermediate portions of the ribs. 
The present invention may be applied to the pump wheel 15.