Method for improved assembly of an actuator for an air bleed valve of a turbine engine

Abstract

A method for assembling an actuating ram of air bleed valves, which ram is placed between low pressure and high pressure compressors of a turbomachine, the ram including a piston rod surrounded by a spacer extending from the piston cylinder and configured to be connected to an end of the transmission mechanism linked to the bleed valves, the method including: deploying the piston rod such that it projects from the spacer; connecting the projecting piston rod to the end of the transmission mechanism; retracting the piston rod to bring the cylinder closer to the case wall; and attaching the spacer to the case wall.

Claims

1. A method for assembling an actuating ram of at least one air bleed valve placed between a low pressure compressor and a high pressure compressor of a turbomachine, the ram including a cylinder configured to be attached to a case wall from which projects an end of a connecting rod linked to the air bleed valve, the cylinder being extended by a spacer being used to attach the cylinder to the case wall, and including a piston rod surrounded by the spacer and configured to be connected to the end of the connecting rod, the method comprising: deploying the piston rod to project from the spacer; connecting the projecting piston rod to the end of the connecting rod projecting from the case wall on a side of the ram; retracting the piston rod to bring the cylinder closer to the case wall; and attaching the spacer to the case wall, wherein the retracting the piston rod is implemented such that a mechanical junction between the piston rod and the end of the connecting rod lies, after the retracting, inside the spacer, wherein the spacer is made to have no side opening, and wherein the method further comprises a prior dimensioning of the ram, respecting the following condition:
(C?M)/2=Y; with C corresponding to a theoretical maximum stroke of the piston; M corresponding to a mechanical stop margin in a retracted position of the rod; and Y corresponding to a distance between the wall and a center of the mechanical junction between the piston rod and the end, with the center of the mechanical junction arranged in the spacer attached to the wall, and bringing each valve into a closing position and bringing the piston rod into a retracted position.

2. The assembling method according to claim 1, wherein the attaching the spacer to the case wall is carried out by screwing.

3. The assembling method according to claim 1, wherein the deploying the piston rod is carried out such that in a ram position enabling the piston rod to be connected to the end of the connecting rod, the case wall and the spacer define between each other an access.

4. The assembling method according to claim 1, wherein the spacer is made as a single piece with the cylinder of the ram.

5. The assembling method according to claim 1, wherein the connecting the projecting piston rod to the end of the connecting rod is carried out using a ball-jointed connection or a hinged connection.

6. The assembling method according to claim 1, wherein the distance C?M is equal to 40 mm.

7. The assembling method according to claim 1, wherein the case wall is a downstream flange of an intermediate case of the turbomachine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood, and further details, advantages and characteristics thereof will appear upon reading the following description made by way of non-limiting example and in reference to the appended drawings wherein:

(2) FIG. 1, already described, is an axial cross-section schematic view of an airplane twin-spool turbojet engine of a known type;

(3) FIG. 2, already described, is an axial cross-section partial schematic view at a greater scale of a turbojet engine of a known type substantially of the same type as that of FIG. 1;

(4) FIG. 3, already described, is a cross-section schematic view for assembling an actuating ram of bleed valves, to a case wall;

(5) FIGS. 4a to 4d represent different successive steps for mounting an actuating ram of bleed valves, according to a preferred embodiment of the invention; and

(6) FIGS. 5 and 6 are schematic views illustrating dimensioning of the actuating ram.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) A preferred embodiment of the assembling method according to the invention is represented in FIGS. 4a to 4d. It aims at assembling, to the case wall 60, the ram 62 actuating the VBV bleed valves 48, through the transmission mechanism. For the implantation of the invention, the elements described in reference to FIGS. 1 to 3 remain identical or similar, except for the spacer 64 which is free of side openings. It thus has a fully solid side wall extending between its upstream collar 70 and its downstream end integral to the ram cylinder 66. Thus, in the figures, the elements bearing identical reference numerals correspond to identical or similar elements.

(8) Here again, the spacer 64 can be fixedly fastened to the ram cylinder 66, or be made as a single piece with the same. In the first case, steel will be preferentially chosen, whereas in the second case, it would rather be aluminium or an alloy thereof.

(9) For the implementation of the method, first the end 74 of the connecting rod 76 should be projecting with respect to the wall 60, to downstream, that is on the side where the ram should be assembled. The projection distance has to be such as to then allow handling by the operator, as will be described hereinafter. This position of the connecting rod 76 can correspond to any position of its stroke along its axis, at the end of which it places the VBV valves respectively in the opening position and in the closing position. However, preferentially, this position of FIG. 4a is close or identical to that placing VBV valves into the closing position.

(10) In parallel, the deployment of the piston rod 68 is carried out, such that it projects from the spacer 64 also on a suitable distance so as to then allow handling of the end of the rod by the operator, as will be described hereinafter. This deployment of the piston rod 68 is also schematized in FIG. 4a.

(11) Then, the ram with its deployed rod is brought closer to the end 74, as shown in FIG. 4b. In this closer position of the ram 62 enabling its rod 68 to be connected to the end 74, the case wall 60 and the collar 70 of the spacer define between each other an access 84 enabling an operator's fingers to go through. Typically, this access has an axial length in the order of the value of the ram stroke, for example about 40 mm. This access 84 can be increased by tilting the axis of the ram 62 with respect to the axis of the connecting rod 76, as has been schematized in FIG. 4b. The access 84 is then defined by the most extended part of the opening between elements 60 and 70, herein the radially outer part, the most accessible to the operator from outside the turbojet engine.

(12) The connection of the piston rod 68 to the end 74 of the transmission mechanism can then be performed via this access 84, using conventional means resulting in obtaining the mechanical junction 78, for example of the ball-jointed connection type.

(13) Once the mechanical junction is obtained, the partial or full retraction of the piston rod 68 is carried out so as to bring the cylinder 66 closer to the wall 60, as schematized in FIG. 4c. This retraction is preferably carried out by moving the cylinder 66 without moving the rod 68 relative to the wall 60, after the connecting rod 76 and the rod 68 have been realigned. It is manually implemented or using a suitable tooling, preferably a pump or the like. During this retraction of the piston rod 68, the latter as well as the connecting rod 76 thus remain substantially static with respect to the wall 60. The retraction is completed when the collar 70 comes to bear against the downstream surface of this wall 60, as is shown in FIG. 4d. At this stage, the mechanical junction 78 then lies inside the spacer 64, within which it can remain confined during the connecting rod stroke aiming at switching from the opening position of the VBV valves to their closing position, and reversely. Alternatively, during this stroke, the junction 78 can go through the opening of the wall 60, and thus go on the other side thereof.

(14) The attachment of the collar 70 to the wall 60 can then be carried out, for example by assembling screws on inserts (not represented) equipping this wall, this screwing being performed from the downstream side where lies the ram. Finally, the ram 62 is thus embedded into the case wall 60, cantilevered.

(15) The invention thus allows an easy assembly of the ram even with a restricted access to the operator, in particular limited to only the downstream side of the wall 60.

(16) For the disassembly of the ram 62 carried out during maintenance phases, the abovementioned operations are implemented in the reverse order.

(17) In reference now to FIGS. 5 and 6, an exemplary embodiment of the actuating ram 62 assembled to the case wall 60 is illustrated, with several preferred dimensioning criteria.

(18) In FIG. 5, the configuration is that placing the VBV bleed valves 48 into the closing position. The piston rod 68 is thus retracted into the regulated stop position. Only a margin M is then observed between the piston 68 and the mechanical stop formed by the cylinder bottom. In this configuration, the distance Y is defined between the wall 60 and the centre of the mechanical junction 78, along the direction of the connecting rod 76 and the piston rod 68. The distance X is in turn defined between the centre of the mechanical junction 78 and the end of the cylinder 66, still along the same direction. Finally, the distance C corresponds to the theoretical maximum stroke of the piston, that is the distance separating both bottoms of the cylinder 66.

(19) Thus, the length of the spacer 64 corresponds to the sum of the values X and Y. The length C?M, referenced in FIG. 6, here corresponds substantially to the access 84, without taking into account a possible tilting of the ram 62. This length therefore is preferentially sufficient to let an operator's fingers pass through. Finally, though not apparent in the figures, it is preferentially provided that the distance Y corresponds to about half the length C?M. The distance C?M is for example in the order of 40 mm, with M usually set to about 2 mm.

(20) It is besides noted that when the spacer 62 is attached to the wall 60, as in FIG. 5, respecting distance Y leads not only to place each valve 48 into the closing position, but also leads to place the piston rod 68 into the retracted position, wherein the aforesaid margin M is observed.

(21) Of course, various modifications could be made by those skilled in the art to the invention just described, only by way of non-limiting examples.