GB2395536A - Coupled Casings - Google Patents

Abstract

Tubular casings (10) and (12) are coupled in an axial direction by upstanding, part circumferential members (16) on casing (10) being caused to enter grooves in part circumferential end portions (14) on the overlapping end of casing (12) by effecting relative rotation of the casings one to the other. Inadvertent relative rotation between the casings (10,12) is prevented by screwed fastenings (30,32) passing radially through the overlapping portions of casings (10,12).

Description

COUPLED CASINGS

The present invention relates to tubular structures assembled from a plurality of casings arranged in co-axial 5 relationship, each being joined to the one adjacent thereto. In such assemblies as are described hereinbefore, it is the norm to fasten the casings, one to the next, via radial flanges formed on Or fixed to respective casings 10 ends, and through which bolts are passed and held in place by co-operating nuts. In such arrangements, it is also the norm that the flanges are thicker than the wall thickness of their respective casings. Further the flanges have to be of such radial depth as to overlap the nuts, bolts head 15 and washers where used so as to ensure sufficient seating area for those features.

The present invention seeks to provide a casing assembly having improved fastening means.

Accordingly the present invention comprises tubular 20 casings assembled by axial coupling, wherein the coupling means comprises part circumferential, equi angularly spaced grooved portions formed on at least one end of a casing, and at least a corresponding number of radially projecting part circumferential identically equi angularly spaced 25 members on at least one ens portion of a further casing, said grooved portions and members being so proportioned as to permit sliding of said asings together in overlapping relationship to position said members between said grooves and permit relative rotation of said casings to cause said 30 members to enter said grooves so as to achieve fixing of said casings together in the axial sense.

The invention will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic axial part cross sectional view of a pair of casings coupled by means in accordance with the present invention.

Figure 2 is a half view of the casings of Figure 1 in 5 the direction of arrow 2.

Figure 3 is a pictorial part view of the casings of Figure 1 with one each of their respective grooves and members. Figure 4 depicts an alternative form of groove in 10 accordance with the present invention.

Figure 5 depicts an alternative form of groove in accordance with the present invention.

Figure 6 is a diagrammatic axial cross sectional part view of a gas turbine engine ducted fan cowl incorporating 15 casings coupled by means in accordance with the present invention. Referring to Figure 1 a pair of cylindrical casings 10 and 12 are removably coupled against inadvertent separation in an axial direction by a number of inter engaging 20 features 14 and 16. Features 14 are part circumferential grooved portions on an end extremity of casing 12.

Features 16 are part circumferential members upstanding on an end portion of casing 10. These forms are best seen in Figure 3.

25 Features 14 and 16 are identically equi angularly spaced about their respective casings 12 and 10. Further the dimension of feature 16 in a direction circumferentially of casing 10 is of a magnitude such that on sliding casing 12 over casing 10, features 16 can be 30 positioned between features 14. Thereafter the casings 1D and 12 are relatively rotated so as to cause features 16 to slide into respective grooves in adjacent features 14,;;tius achieving coupling of the two casings and preventing inadvertent separation in axial directions..

Referring briefly to Figure 2 this view clearly illustrates the common angular spacing of features 14 and 16. Referring now to Figure 4 herein in which like parts 5 have like numbers, casing 12 and feature 14 as in Figure 1.

However, casing 10 is provided with a further circumferential array of features 18 which together with features 16 define grooves 20 in which respective lips 22 of features 14 (Figure 3) lie when casings 10 and 12 are 10 assembled as described hereinbefore.

Referring now to Figure 5 in this example of the present invention both casings have features 14 and 16 and could also incorporate feature 18 (Figure 4) though this is not shown in Figure 5.

15 Referring now to Figure 6 herein two cowl portions 24,26 of a ducted fan gas turbine engine surround a stage of fan blades 28 only one of which is shown. The cowl portions are coupled together by the groove and member features 14 and 16 as described with reference to Figure 1.

20 Figure 1 shows one of several bolts 30 passing through one pair of several pairs of holes 34, 36 in the overlapping portions of casing 10 and 12, in a direction radially of the casings axis (not shown). Nuts 32 on the projecting ends of bolts 30 when tightened, clamp casings 25 10 and 12 together, thus preventing inadvertent relative rotation thereof out of axial engagement.

Whilst nut and bolt fastenings are not shown in Figures 3 to 6, chain dotted lines 28 represent their axes and should be taken as indicating their use.

30 Advantages to be gained by utilising the present invention includes: a) a reduction in maximum diameter of the assembly relative to that obtained using standard flanged joints;

b) a reduction in the number of nuts and bats needed to achieve the desired fixing loads which in turn reduces assembly weight.

c) axial and radial operating loads will be 5 countered by the groove and member system without occurrence of casing separation which is a fault to which standard flanged joints are susceF ible.

d) When used in the environ-.ent depicted in Figure 6 the overlapping portions of th_ casings provide extra 10 resistance to the passage of a broken fan blade through the fan cowl to atmosphere.

Claims (7)

1. Tubular casings assembled by axial coupling wherein the coupling means comprises part circumferential equi 5 angularly spaced grooved portions formed on at least one end of a said casing, and at least a corresponding number of radially projecting, part circumferential identically equi angularly spaced members on at least one end portion of a further said casing, said grooved portions and members 10 being so proportioned as to permit sliding of said casings together in overlapping relationship to position said members between said grooved portions, and permit relative rotation of said casings to cause said members to enter the grooves, so as to achieve fixing of said casings together 15 in the axial sense.

2. Tubular casings as claimed in claim 1 including a further corresponding number of members on said further casings, said further members being angularly aligned with the first mentioned members and axially spaced therefrom so 20 as to receive the lips of respective groove portions therebetween when relative rotation of said casings is effected.

3. Tubular casings as claimed in claim 1 or claim 2 wherein each casing has grooved portions at one end and 25 members near said one end wherein the respective radial dimensions of the grooves of said grooved portions and members extend in opposing directions so as to provide double coupling of casing ends one to the other.

4. Tubular casings as claimed in any previous claim 30 wherein said casings comprise at least a portion of the fan duct of a ducted fan gas turbine engine.

5. Tubular casings substantially as described in this specification and with reference to Figures 1 and 3 of the

accompanying drawings.

6. Tubular casings substantially as described in this - specification and with reference to Figure 4 of the

accompanying drawings.

7. Tubular casings substantially as described in this 5 specification and with reference to Figure 5 of the

drawings.