Apparatus for inspecting mechanical strength of bottom portions of bottom-closed hollow pipes

A bottom strength-inspecting apparatus for bottom-closed hollow pipes is disclosed. This apparatus includes an air chuck 2 for holding an outer peripheral surface of the bottom-closed hollow pipe W, and a pressing elements coaxially provided with the air such as elastic pressing element 8 adapted to contact a bottom surface 9 of the bottom-closed hollow pipe W from an axially outer side of the hollow pipe and press the bottom surface by given forces.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an apparatus for inspecting mechanical 
strength of bottom portions of bottom-closed hollow pipes. For example, 
this apparatus may be used to inspect mechanical strength of bottom 
portions of bottom-closed hollow pipes made of zirconia and having the 
bottoms closed with the same material at one end. 
2. Related Art Statement 
Although the above ceramic-closed hollow pipe are used, for example, as 
constituent members for cells, no bottom portion strength-inspecting 
apparatuses have been formerly known which could accurately inspect 
strength of a bottom portion of the bottom-closed hollow pipe of this 
type. Strength of bottom-closed hollow pipes have been inspected by 
applying pressure inside the hollow pipe. However, it is difficult to 
inspect the strength of the bottom portion, because when high pressure is 
applied to the interior of the slender bottom-closed hollow pipe, a side 
wall is first broken. However, when such slender bottom-closed hollow 
pipes are used as constituent parts for fuel cells, they are often broken 
due to lack in strength at their bottom portions thereby posing a 
practical problem. 
SUMMARY OF THE INVENTION 
The present invention solves the above-mentioned problems possessed by the 
above prior art, and provides an apparatus for inspecting mechanical 
strength of bottom portions of slender bottom-closed hollow pipes, which 
enables ready and accurate inspection of the mechanical strength of the 
bottom portions of the slender bottom-closed hollow pipes. The term 
"mechanical strength" used in the specification and claims is intended to 
mean the following. 
The mechanical strength includes both mechanical strength of a bottom 
portion and bonding strength between a peripheral wall portion and the 
bottom portion in the case of a one end-closed pipe. If the bonding 
strength is smaller than the mechanical strength, the former is measured. 
On the other hand, if the bonding strength is greater than the mechanical 
strength, the latter is measured. 
In FIGS. 1A through 1E, specific forms of the bottom-closed hollow pipes 
are shown by way of example. In these figures, A and B denote a peripheral 
wall portion and a bottom portion of the bottom-closed hollow pipes, 
respectively. In FIGS. 1A through 1D, the bottom portion is bonded to an 
end portion of the peripheral wall portion with an appropriate bonding 
agent. The present invention is applicable not only to the bonded type 
bottom-closed hollow pipes as shown in FIGS. 1A through 1D but also to an 
integral type as shown in FIG. 1E. In the hollow pipe shown in FIG. 1E, a 
bottom portion B is not bonded to a peripheral wall portion A, but the 
former is simultaneously and integrally formed with the formation of the 
peripheral wall portion, for example, by a casting process. The mechanical 
strength of the bottom portion B of the bottom-closed hollow pipe as shown 
in FIG. 1E can be also measured according to the present invention. 
A first aspect of the present invention is characterized in that the 
inspecting apparatus includes an air chuck for holding the outer 
peripheral surface of the bottom-closed hollow pipe sealed at the bottom 
portion, and a pressing means provided coaxially with the air chuck, 
wherein the pressing means is provided with a elastic pressing element 
which is to contact the outer surface of the bottom portion of the 
bottom-closed hollow pipe from an outer side thereof and to axially press 
the outer surface of the bottom portion. 
A second aspect of the present invention is characterized in that the 
inspecting apparatus includes an air chuck for holding the outer 
peripheral surface of the bottom-closed hollow pipe sealed at the bottom 
portion, and a pressing means provided coaxially with the air chuck, 
wherein the pressing means is provided with a pressing rod for passing 
into the interior of the bottom-closed hollow pipe, and for reaching and 
pressing the bottom surface of the hollow pipe through an elastic pressing 
element attached to the tip of the pressing rod. 
In the inspecting apparatus according to the present invention, whether 
adhesion strength of the bottom portion of the bottom-closed slender 
hollow pipe is acceptable can be accurately determined by applying given 
forces to the bottom portion of the hollow pipe held by the air chuck by 
means of the elastic pressing element from the inner surface or the outer 
surface of the bottom portion in the axial direction of the hollow pipe. 
These and other objects, features and advantages of the invention will be 
appreciated upon reading of the following description of the invention 
when taken in conjunction with the attached drawings, with the 
understanding that some modifications, variations and changes of the same 
could be made by the skilled person in the art to which the invention 
pertains without departing from the spirit of the claims or the scope of 
claims appended hereto.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be explained in more detail with reference to 
the embodiments shown in the attached drawings. 
In FIGS. 2 and 3, a reference numeral 1 is a base, and an air chuck 2 is 
vertically arranged in a central hole of the base, for supporting the 
outer peripheral surface of a bottom-closed hollow pipe W. The air chuck 
includes guide members 3, 3 at upper and lower portions, and a ring-shaped 
elastic member 4 is arranged in the central portion of a frame of the air 
chuck. After the hollow pipe is passed through a central hole of the 
elastic member 4, the elastic member is radially inwardly expanded by air 
pressure to hold the outer peripheral surface of the bottom-closed hollow 
cylinder W. Thus, the air chuck can fixed hold the bottom closed hollow 
pipe W in the state that the pipe W is well aligned with the air chuck. If 
the holding forces are insufficient, as shown in FIGS. 2 and 3 by 
imaginary lines, another air chuck 2 may be provided above the air chuck 
2, through supporting poles and a base at upper ends of the poles. 
A reference numeral 5 is a pressing means coaxially arranged under the air 
chuck 2. In this embodiment, the pressing means 5 includes an air cylinder 
6 arranged vertically under the base 1, a pressing rod 7, and an elastic 
pressing element 8, made of hard rubber, for example, attached to the 
upper tip of the pressing rod 7. That is, rods X and Y are extended 
downwardly from the base 1, while upper ends of the rods are fixed to the 
base by bolts. The rods X and Y penetrate bases 1A and 1B under the base 
1. The bases 1A and 1B are slidably held through the rods X and Y by means 
of bolts. The air cylinder 6 is fixed to the under face of the base 1B, 
and a plunger of the air cylinder 6 is passed through a central hole of 
the base 1B, and butted or fixed to the under face of the load cell 10 
positioned above the base 1B. The lower end of the pressing rod 7 is 
placed or fixed onto the upper portion of the load cell 10, and the rod 7 
passes a central hole provided in the base 1A. A bearing 11 is located on 
the base 1A. The pressing rod 7 is aligned with the bottom-closed hollow 
pipe held by the air chuck by means of the upper end of the bearing 11 and 
the load cell 10. As shown in FIG. 4, the elastic pressing element 8 is 
adapted to contact and press only a sealed bottom surface 9 of the 
bottom-closed hollow pipe W from the exterior side. The pressing element 8 
has an upper surface curved to conform with the outer profile of the 
bottom-closed hollow pipe W. By so constructing, local concentration of 
loads upon the bottom surface 9 can be prevented, and alignment between 
the bottom-closed hollow pipe and the pressing element can be readily 
effected. Further, a load cell 10 is interposed between the air cylinder 6 
and the pressing rod 7, so that the inspecting means can accurately detect 
pressing forces at every moment. The bearing 11 which is vertically 
movably supports the pressing rod 7, and receives the pressing rod 7 at an 
upper end only. Thereby, the bearing 11 prevents slanting of the 
bottom-closed hollow pipe W in cooperation with the load cell. 
FIG. 5 illustrates a second embodiment in which an elastic pressing element 
8 has such a structure that the pressing element 8 is expanded with fluid 
pressure to be deformed to conform with the configuration of the bottom 
surface 9 of the bottom-closed hollow pipe W. That is, the elastic 
pressing element 8 is an elastic rubber member 12 attached to an interior 
end of a cylindrical guide 7' made of stainless steel or the like and 
attached to or extended from the upper end of the pressing rod 7. When 
fluid pressure such as oil pressure, hydraulic pressure, pneumatic 
pressure or the like is applied to the cylindrical guide 7' through the 
pressing rod 7, the elastic rubber 12 expands so that the elastic pressing 
element may closely adhere to the bottom surface 9 of the bottom-closed 
hollow pipe W. In this embodiment, the other constituent parts are the 
same (the base 1A and the bearing 11 are not shown, although they may be 
omitted), and therefore explanation thereof is omitted. 
In order to inspect mechanical strength of the bottom-closed hollow pipe W 
having the bottom portion sealed by means of the bottom 
strength-inspecting apparatus according to the first aspect of the present 
invention, the bottom-closed hollow pipe W is downwardly inserted through 
the air chuck 2 in an opened state as shown, and the bottom face 9 is 
placed on the elastic pressing element 8 of the pressing means 5. At that 
time, the bottom-closed hollow pipe W is aligned with the pressing element 
8 by means of the upper and lower guide portions 3, 3 of the air chuck 2 
and the elastic pressing element 8. Then, pneumatic pressure is applied to 
the air chuck 2, and the outer peripheral surface of the bottom-closed 
hollow pipe W is firmly chucked. By actuating the air cylinder 6, only the 
bottom surface 9 of the bottom-closed hollow pipe W is pressed. At that 
time, the pressing forces can be accurately detected by means of the load 
cell 10. Bottom-closed hollow pipes, which are not broken at the bottom 
face 9 under application of given forces, are judged acceptable. On the 
other hand, if bottom-closed hollow pipes W have weak mechanical strength 
for some reason, their bottom faces 9 will be broken. 
As explained above, according to the first aspect of the inspecting 
apparatus of the present invention, the mechanical strength of the bottom 
portion of the bottom-closed hollow pipe W can be readily and accurately 
inspected. In addition, since the elastic pressing element 8 is used, 
local concentration of load upon the bottom surface 9 can be prevented, 
and the mechanical strength can be measured, while breakage of the 
material itself constituting the bottom-close hollow pipe W can be 
avoided. 
FIG. 6 illustrates an embodiment according to the second aspect of the 
present invention in which a pressing means 13 is provided above an air 
chuck 2 arranged in a central hole of a base 1. This pressing means 13 is 
supported at another base fixed to upper ends of supporting poles to which 
the base 1 is also fixed. An air cylinder 6 is provided above the pressing 
means 13 through a load cell. The pressing means 13 is provided with a 
pressing rod 14 which can reach the inner bottom face 9 of the 
bottom-closed hollow pipe W. The pressing rod 14 is provided with an 
elastic pressing element 15 at its tip, and the elastic pressing element 
15 pushes the bottom surface of the hollow pipe W from the inside. The 
construction of the pressing element is the same or similar to that in the 
first aspect of the present invention. In the embodiment of FIG. 6, hard 
rubber is used as the elastic pressing element 15, but any material which 
is deformed by expansion by fluid pressure may be used. 
In order that the mechanical strength of the bottom portion of the 
bottom-closed hollow pipe W having the bottom sealed may be inspected by 
means of the bottom strength-inspecting apparatus for the bottom-closed 
hollow pipe according to the second aspect of the present invention, the 
bottom-closed hollow pipe W is first held by the air chuck 2, the pressing 
rod 14 is inserted into the interior of the hollow pipe, and the elastic 
pressing element 15 at its lower end is contacted with the bottom surface 
9 of the pipe. The pressing rod 14 is lowered by the air cylinder 6 to 
press the bottom surface 9 of the pipe from the inside. As a result, if 
the bottom-closed hollow pipe W has low mechanical strength, the bottom 
face 9 is broken. Similar first aspect of the present invention, 
bottom-closed hollow pipes which are not broken under application of given 
forces, are judged acceptable. 
As mentioned above, according to the present invention, the mechanical 
strength of the bottom portion of the slender bottom-closed hollow pipe 
having the bottom portion formed by sealing the end portion can be readily 
and accurately inspected from the outside or the inside of the pipe by 
means of the elastic pressing element. Further, according to the present 
invention, since the elastic pressing element may easily conform with the 
configuration of the bottom portion of the bottom-closed hollow pipe is 
used, the mechanical strength can be accurately inspected, while breakage 
of the material itself due to local concentration of stresses can be 
avoided. 
Therefore, the present invention can greatly contribute to the industrial 
development as the bottom strength-inspecting apparatus for the 
bottom-closed hollow pipes, which apparatus solves the problems possessed 
by the prior art.