A regenerator includes a cylindrical body and a plurality of improved wire mesh screens stacked inside the cylindrical body. Each wire mesh screen includes a number of interwoven wires that overlap one another at the cross points of the wire mesh screen, with the overlapping wires being compressed at the cross points in the direction in which the wire mesh screens are stacked. This shortens the distance between the central axes of the overlapping wires at the cross points in the stacking direction so that a greater number of the wire mesh screens may be stacked in the cylinder.

BACKGROUND OF THE INVENTION 
This invention relates to a heat regenerator and more particularly to a 
heat regenerator of the type arranged between the expansion space and 
compression space of a heat gas engine such as a stirling cycle engine to 
effect thermal regeneration. 
To operate a regenerator at a high performance, it is required not only 
that the materials to be used have a high thermal capacity but also that 
the regenerator have a large specific surface area, namely a large heat 
transfer or conductive surface area per unit volume, a smaller dead volume 
internally of the regenerator, and little fluidic resistance. For this 
purpose, Book B, Vol. 248, No. 435 of the technical papers of the Japan 
Mechanics Society (November, 1982) describes a regenerator structure 
comprising a cylindrical body and a number of wire mesh screens stacked in 
the cylindrical body and consisting of wires made of copper or SUS-27. 
With the wire mesh screens used in a conventional regenerator, thermal 
capacity, specific surface area, dead volume and fluidic resistance 
naturally are decided by the number of stacks of wire mesh screens in the 
regenerator, the wire mesh material, the number of meshes and the wire 
diameter. To increase thermal capacity and specific surface area, 
therefore, one possible approach is to enlarge the size of the wire mesh 
screens and increase the number of stacks thereof, and another is to 
reduce wire diameter and increase the number of meshes. However, the 
former increases dead volume, and the latter raises fluidic resistance by 
decreasing the degree of pore opening of the meshes. The end result in 
either case is a failure to improve regenerator performance. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a regenerator 
the peformance of which is improved by reducing dead volume and increasing 
specific surface area without raising fluidic resistance. 
According to the present invention, the foregoing object is attained by 
providing a regenerator comprising a cylindrical body and a plurality of 
wire mesh screens stacked inside the cylindrical body. Each wire mesh 
screen includes longitudinally and transversely extending wires of 
generally circular cross section woven into a mesh. The wires overlap each 
other at the cross points of the mesh, with the overlapping portions of 
the wires being compressed in the stacking direction to locally flatten 
their cross sections at the cross points and, hence, to reduce the 
distance between the central axes of the overlapping wires. This allows a 
greater number of the wire mesh screens to be stacked in the cylindrical 
body, thus enabling an increase in specific surface area and a reduction 
in dead volume without raising fluidic resistance. 
Other features and advantages of the present invention will be apparent 
from the following description taken in conjunction with the accompanying 
drawings, in which like reference characters designate the same or similar 
parts throughout the figures thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Before describing an embodiment of the present invention in detail, let us 
refer to FIGS. 1 and 2 for a review of the art to which the present 
invention appertains in order to grasp and understand the principle of the 
invention. 
FIGS. 1 and 2 show a portion of a conventional wire mesh screen 1 a number 
of which are stacked in a cylindrical body. It will be seen in the side 
view of FIG. 2 that the longitudinally and transversely extending wires 
1a, 1b constituting each screen 1 overlap each other, and that the 
distance in the stacking direction between the central axes of the wires 
1a, 1b where they overlap is l.sub.1. 
The inventors have given special attention to the dimension l.sub.1 and 
have discovered that this dimension makes it possible to be shortened, 
with a regenerator of the same volume, to increase the number of wire mesh 
screens in the stack, reduce dead volume and enlarge specific surface area 
without raising fluidic resistance. Based on this discovery, the inventors 
have developed a regenerator having an improved wire mesh screen in which 
the overlapping portions of the wire constituting the wire mesh screen are 
compressed in the stacking direction to reduce the distance between the 
central axes of these overlapping wires in the stacking direction. 
An embodiment of the present invention adopting the foregoing principle is 
illustrated in FIGS. 3 and 4. A wire mesh screen 10, a number of which are 
stacked axially in a cylindrical body 20 shown in FIG. 5, comprises 
longitudinally and transversely extending wires 10a, 10b of generally 
circular cross section woven into a mesh. The wires 10a, 10b overlap each 
other at the cross points of the mesh, as best seen in FIG. 3. The 
overlapping portions of the wires 10a, 10b are subjected to a compressive 
force applied by a roll to compress these portions in the stacking 
direction, whereby each overlapping portion is deformed from the generally 
circular cross section to one which is generally rectangular, as shown in 
FIG. 4. The overlapping portions of the wires 10a, 10b thus deformed have 
flattened surfaces, which are designated at numeral 30. The result is to 
reduce the distance between the central axes of the overlapping wires 10a, 
10b from l.sub.1 (FIG. 2) to l.sub.2, shown in FIG. 4. 
It will be appreciated from FIG. 3 that compressing the overlapping 
portions of the wires 10a, 10b to form the flattened surfaces 30 has 
almost no effect upon the degree of pore opening and, hence, does not 
increase fluidic resistance. Shortening the dimension l.sub.2 does, 
however, have the advantageous effect of allowing a greater number of the 
wire mesh screens 10 to be stacked in the cylindrical body 20, thus 
enabling an increase in specific surface area and a reduction in dead 
volume without raising fluidic resistance. 
Rather than applying a roll to the wire mesh screen following its 
fabrication, it is possible to shape those portions of individual wires 
that will eventually overlap into a rectangular or oval cross section in 
advance and then weave the wires into a mesh in such a manner that the 
portions so reduced in cross section overlap. 
As many apparently widely different embodiments of the present invention 
can be made without departing from the spirit and scope thereof, it is to 
be understood that the invention is not limited to the specific 
embodiments thereof except as defined in the appended claims.