Apparatus for connecting a cover band to guide blading of a turbomachine

A riveting machine for connecting semi-cylindrical cover bands to the head ends of guide blading provided with rivet spigots at any point within a blade-carrying semi-cylindrical turbine component includes a radially adjustable riveting arm mounted for rotation within a plane normal to the cylinder axis about a pivot axis coaxial with that of the cylinder, and a riveting group carried at the outer end of the arm which comprises a rotatable riveting spindle and associated mechanism for pressing the cover band firmly against the head ends of the rigidly held guide blading while the rotatable riveting spindle works a head onto the spigot.

FIELD OF THE INVENTION 
The present invention relates to an improved apparatus for obtaining a 
durable connection between guide blading on a blade-carrying 
semi-cylindrical component of an axial flow type turbo-machine and a 
semi-cylindrical cover band which is secured to the heads of the guide 
blading by a riveting operation. 
BACKGROUND OF THE INVENTION 
Durable connections between guide blading and cover bands therefor are 
accomplished in many instances by hot or cold riveting. In both cases, the 
riveting process can be carried out by means of a hammering or rolling 
operation. It is known to use stationary riveting machines for either 
procedure, and mobile riveting apparatus can be used for applying the 
hammering technique. 
A high-quality riveted joint can be accomplished by the known radial 
riveting method, a method that is similar to cold extrusion molding but it 
requires the use of special machines in view of the special operational 
requirements. This means that the objects to be riveted together, in the 
present case, guide blade carrying turbine semi-cylindrical components and 
their cover bands, must be fed into the radial riveting machine. Since 
modern, large-sized turbine cylinders cannot be readily moved in this 
manner, a manual riveting technique is being used in most cases. This 
manual riveting operation by means of a hammer, and possibly involving 
also a heating operation, requires great skill, aptitude and experience 
for accomplishing a properly riveted joint. The expenditure of time, and 
also the annoying noise level are relatively high in comparison with the 
mechanical radial riveting method. Furthermore, the riveted joints so 
produced will be of a diverse quality, and there will always be the danger 
of hidden deficiencies, such as crack formations, insufficient filling of 
rivet holes and stresses within the material, especially in the case of 
hot-riveting. 
SUMMARY OF INVENTION 
The principal objective of the present invention is to provide an improved 
and more economic riveting apparatus that makes it feasible to 
mechanically connect cover bands to the head ends of the guide blading at 
any point within the blade-carrying semi-cylindrical turbine component. 
The invention solves the problems previously existing in that the riveting 
machine includes a readily adjustable riveting arm which is mounted for 
rotation within a plane normal to the cylinder axis about a pivot axis 
coaxial with that of the cylinder, and a riveting group carried at the 
outer end of the arm which comprises a rotatable riveting spindle and 
associated mechanism for pressing the cover band firmly against the head 
ends of the rigidly held guide blading while the riveting action between 
these two parts is taking place. 
The invention offers the primary advantages that the riveting machine will 
provide greater work economy due to the precise, mechanical positioning of 
the rotatable and axially displaceable riveting spindle. Furthermore, the 
riveting machine is capable of being operated in a simple manner by 
semi-skilled personnel thus eliminating the need for use of highly skilled 
workers. 
It will be particularly advantageous to operate the riveting spindle in 
accordance with the radial cold riveting method because this will now make 
possible the preparation of high-quality riveted joints, resulting from 
the radial riveting method, in the interior of the cylinders, work areas 
which could not be reached by prior known standard riveting machines. 
It will be expedient to support the radially movable riveting arm by means 
of a pivot mounting, making it adjustable in a continuous, i.e. stepless 
manner over a range of 180.degree. from a horizontal line. It will also be 
helpful if the pivotal mounting includes adjustability in a stepless 
manner in the axial direction of the semi-cylindrical guide blade carrying 
turbine component, this being accomplished by means of an axially guided 
carriage on which the pivot mounting for the riveting arm is supported. 
The improved arrangement thus makes it possible to carry out the cover 
band-to-guide blading riveting operation by utilizing one and the same 
riveting machine regardless of the diameter and length of the turbine 
cylinder involved. 
In the case of a preferred embodiment, the mechanism for pressing the cover 
band against the heads of the guide blading includes a cylindrical jacket 
arranged co-axially with and surrounding the riveting spindle, and which 
is provided with piston components in common with the spindle serving to 
control the axial feed motions of the riveting spindle and cover band 
pressing mechanism towards and away from the rivet head and cover band 
respectively. 
It will also be advisable to equip the cover band pressing mechanism with a 
hold-down in the form of a press pad which is applied against the surface 
of the cover band which in turn exerts a force against the head end of the 
guide blading, the latter being provided with rivet spigots which project 
through holes provided in the cover band. A hold-down mechanism of this 
type ensures the essential full seating of the cover band at the head of 
the blading in that the contact surfaces of the press pad become engaged 
in close proximity to the rivet spigot. Furthermore, the mounting of the 
riveting spindle within the hold-down mechanism will permit a full 
absorption of the shearing forces which arise during the radial riveting 
operation so that there will be no need for additional supporting means.

Components which are immaterial insofar as the invention is concerned, such 
as drives and controls, have not been illustrated since these can be 
conventional and may take different modes. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
With reference now to the drawings, a semi-cylindrical component 1 of a 
turbo-machine is seen to be provided with guide blading 2. The 
semi-cylindrical cover band 3 to be riveted to the head ends of the guide 
blading is provided with apertures 18 through which project rivet spigots 
4 integral with the blading. The semi-cylindrical guide blade carrying 
component 1 rests with its diametral surface portions upon upstanding 
fixtures 6 on base plate 19 and is secured to the fixtures by way of 
fastening bolts, not specifically shown, which extend through flange 
portions into T-shaped slots located at the upper ends of the fixtures 6. 
Normally four such fixtures 6 and attachments are used for fastening the 
semi-cylindrical guide blade carrier 1 firmly in place on base plate 19. 
The fixtures 6 are adjustable along the base plate by means of T-slots, 
not illustrated, to different distances apart so that the riveting machine 
can accommodate semi-cylindrical guide blade carrying turbo-machine 
components of different diameters. Central alignment of the fixtures 6 
relative to the riveting machine mounted between them is accomplished by 
means of adjustable screw spindles 8 which extend between fixtures 6 and 
carriage bed 9 of the machine which is fastened firmly in place on base 
plate 19, the fastening being accomplished by any suitable, 
non-illustrated clamping arrangement. Base plate 19 and carriage bed 9 are 
so dimensioned in the direction of the axis of the semi-cylindrical 
turbine component 1 that they are capable of accommodating and processing 
any required length of the latter. 
A platen 10 connected to the carriage bed 9 by means of the usual dove-tail 
guide 20 or an equivalent in the form of a flat, prismatic or roller type 
guide serves as a mount for the riveting mechanism which can thus be moved 
axially within the semi-cylindrical guide blade carrying structure so as 
to be able to rivet the different rows of blading provided within the 
same. This riveting mechanism includes a control housing 11, a pivot 
mounting 12 atop the control housing and a rivet arm 13 supported by the 
pivot mounting 12 and which extends in a radial direction from the pivot 
axis 14. The height of the upstanding fixtures 6 is dimensioned in such 
manner that the rotational axis 14 of the pivot mounting 12 coincides with 
the axis of the semi-cylindrical guide blade carrier 1 which rests upon 
these fixtures. 
The pivot mounting 12 includes a turning plate which is mounted on both 
sides and which carries a receptacle for the rivet arm 13. The rivet arm 
13 and the turning plate are infinitely variable, i.e. in a stepless 
manner, by not illustrated hydraulic servo-drives located in the control 
housing 11, and the pivot mounting 12 is designed in such manner that the 
pivot arm 13 is capable of performing a rotational movement spanning 
180.degree. from the horizontal line, as indicated in FIG. 1, thus making 
it possible to reach all rivet spigots 4 on the guide blading 2. Since a 
very accurate positioning of rivet arm 13 is essential, an infinitely 
variable rotational adjustment of the mounting turning plate can be 
accomplished by use of a self-locking reduction worm gear drive. It will 
be expedient to protect the 180.degree. horizontal limit positions of 
rivot arm 13 by means of electrical circuit breakers in a known, but not 
illustrated manner. 
Within control housing 11 there are further located, not illustrated servo 
mechanisms which supply pressurized oil for operation of the riveting 
group 15 mounted at the outer end of rivet arm 13. The latter is connected 
mechanically with the turning plate of the pivot mounting 12. It serves to 
actuate the riveting group 15 along a semi-circular path and sets the 
starting position for the riveting operation. In order to make it possible 
to cover any operating range, determined by the smallest and largest 
diameters of the guide blade carriers being processed, the rivet arm 13 is 
designed in such manner that it can be adjusted. It consists of several, 
schematically illustrated, telescoped components 21 which can be extended 
or retracted synchronously, for example, by means of a non-illustrated 
worm-gear spindle. The inner telescopic part is equipped with a receptacle 
for mounting the riveting group 15 and also accommodates the necessary 
pressurized oil feed lines for actuating the riveting group. 
The riveting group 15 is illustrated at a larger scale in FIG. 2 from which 
it will be seen that it comprises a riveting spindle 16 and the cover band 
pressing and hold-down mechanism 17. The riveting spindle operates in 
accordance with the known radial cold-riveting method and is driven by a 
motor 22 actuated by pressurized oil. Spindle 16 is guided within a 
cylindrical jacket 23 of the hold-down mechanism 17 and has, in common 
with the latter, a piston chamber 25, 25'. Piston 26 which is located in 
this chamber and is attached to spindle 16 controls the riveting spindle 
motion. The latter forms also one part of the inner boundary of piston 
chamber 24, 24' within which the feeding motion of the hold-down mechanism 
17 takes place. For this purpose, jacket 23 is provided with pistons 27 
and 28. A stationary piston 29 forms an additional boundary for the piston 
chamber. A cover band press pad 30 is secured to the outer end of jacket 
23 by means, not illustrated, and includes a central opening through which 
the riveting spindle 16 can pass for working the heads of the rivet 
spigots 4 to secure the cover band 3 to the head ends of the guide blading 
2. 
The shaping of press pad 30 is based upon the requirement that the cover 
band 3 be forcefully pressed against the blading 2 and also be able to 
absorb shearing forces which arise during the radial riveting operation. 
The first requirement is important because the cover bands are usually 
made from rolled profile stock and therefore have bending resilience. The 
cover bands when placed onto the rivet spigots 4 will for this reason fail 
to make close contact with the heads of the blading 2 unless they are 
firmly braced. It is also the function of the hold-down mechanism 17 to 
support the riveting group 15 together with the rivet arm 13 by clamping 
the units between the cover band 3 and the turning plate of the pivot 
mounting 12. 
Before explaining the method of operation of the riveting machine it needs 
to be stated that all steps involved in the method are carried out 
preferably by electro-hydraulic mechanisms. Within the machine proper, the 
operational steps are performed mostly by mechanical means, i.e. by means 
of gearings. Axial movement of platen 10 on which the machine is mounted, 
as well as rotary movement of the pivot mounting 12 are controlled by 
means of hydraulic servo motors. Upon reaching their proper positions, 
these units are held in place by hydraulic clamping. 
The guide blade carrying semi-cylinder 1 shown in FIG. 1 is assumed to be 
properly aligned and fastened on the fixtures 6. The riveting machine is 
then moved by carriage bed 9 and platen 10 into the initial axial position 
which means that the rivet spindle 16 is moved into the plane of the rivet 
spigots 4 of a row of blading 2 to be riveted to the cover band. Following 
this positioning, the platen 10 is rigidly fastened to the stationary 
carriage base 9 by means of non-illustrated gripping ledges so that the 
forces which arise during the riveting operation will not place a stress 
on the carriage guides. 
The riveting group 15 is then brought into the initial radial position by 
means of the telescoped parts 21 of rivet arm 13, which means that the 
frontal area of press pad 30 is moved until its distance from the internal 
surface of cover band 3 is approximately 10 mm. The riveting group 15 is 
now moved by way of its pivot mounting 12 so that the axis of riveting 
spindle 16 is aligned with that of a rivet spigot 4 to be worked. The 
turning plate of the pivot mounting 12 is then clamped down centrally. 
The manner in which the hold-down mechanism 17 and riveting spindle 16 
operate will now be explained in more detail on the basis of FIG. 2. When 
the adjustment of the riveting group 15 in relation to a rivet spigot 4 
has been completed, piston chamber 24' is pressurized with oil. Piston 28 
then moves the cover band hold-down mechanism 17 forward and press pad 30 
forces the cover band 3 against the head of blading 2. The riveting 
machine is thus now positively coupled to the blade carrier 1 and a closed 
path of forces is created by the various mountings, to wit: the riveting 
machine/base plate, base plate/fixtures, and fixtures/blade carrier. This 
closed path of forces will become effective only if the power effect of 
the cover band hold-down mechanism 17 is greater than the pressure applied 
to the rivet spigot 4 by the riveting spindle 16. For this reason the 
hold-down function and riveting function are indpendently controlled. The 
riveting function is started by activating oil motor 22 causing spindle 16 
to rotate. Piston chamber 25 is now oil pressurized and riveting spindle 
16 is advanced by piston 26 to engage the end of the spigot 4 and will 
carry out the riveting operation which is known per se. It consists 
primarily of a radial rolling out of the end of the spigot transforming it 
into a rivet head by use of a steady axial force of up to 3.5 tons. The 
preciseness and uniformity of the height of all rivet heads attained by 
this mechanical riveting method makes it feasible to arrange later on an 
additional sealing strip at the cover band, thus increasing the degree of 
efficiency of the blading. Furthermore, the quality of the riveted joint 
is substantially improved in comparison with a joint produced by manual 
hammering because the radial riveting method preserves the structure of 
the rivet head material. 
When the riveting operation has been completed, piston chamber 25' is oil 
pressurized, the riveting spindle 16 is returned to its initial position 
and oil motor 22 is cut off. Piston chamber 24 is now oil pressurized and 
piston 27 returns the cover band hold-down mechanism 17 to its initial 
position, thereby breaking the closed force path. The lock on pivot 
mounting 12 is then released and the riveting machine can then be moved to 
the next riveting position. 
In conclusion, the inventive concept as defined in the appended claims is 
obviously not limited to the specific embodiment which has been described. 
It is possible, for example, to install the riveting group 15 on a mobile 
base in lieu of the locally fastened carriage guide as illustrated by FIG. 
1. A solution of this type results in a riveting machine of extremely 
great mobility and almost unlimited possibilities of practical use. It is 
also obvious that the pivot mounting 12 and the rivet arm 13 secured 
thereto are not limited to the specific embodiments illustrated, and that 
all known solutions relating to the production of linear and rotary 
movements do not exceed the scope of the invention.