GB2463392A

GB2463392A - Hydraulic clamping device

Info

Publication number: GB2463392A
Application number: GB0919250A
Authority: GB
Inventors: Benjamin John Ridehough; Francis Bernard Welch; Nicholas Michael Gibson
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-12-24
Filing date: 2009-11-03
Publication date: 2010-03-17
Anticipated expiration: 2029-11-03
Also published as: GB0823505D0; GB0919250D0; GB2463392B

Abstract

The device includes three main parts, a lower base 9, a middle section 10 and a top member 11. A moulded membrane or diaphragm (15, figure 5) is positioned and encapsulated within the middle section and has a concave lower base compatible with the profile of an airfoil blade contour 23. An oil reservoir is provided in the upper part of the membrane with a hand operated spindle 17 and piston 22, retained by screw-threaded means within the top member. The base has a convex portion 9b compatible with the blade to provide a gripping force to hold and securely retain the blade when subjected to hydraulic pressure from the membrane. The device may be used to rigidly hold the blade in readiness for machining purposes.

Description

IMPROVEMENTS RELATING TO MACHINING AIDS FOR

TURBINE BLADES

FIELD OF THE INVENTION

By present conventional methods, the machining of turbine blades, (and for this description only, will be that of Jet Engine turbine blades).

The major problem being that of Clamping/holding the said blades in a firm and rigid position, whilst the machining operation to certain areas of the blade is carried out.

The difficulty being, that the blades are of complex shapes, having concave and convex surfaces, leading to clamping problems.

One particular method which is currently in use will be described briefly as follows:-A typical blade requiring machining at the Root end, will be housed within a fabricated steel box, which has been manufactured for this purpose. Within the box and positioned at the base are three vertical Pegs/Dowels, and are in specified positions, known as K' points, which have been accurately calculated. The said pegs stand perpendicular to the base, and form a three point triangle., one spaced towards the Tip end of the said blade and Two towards the Root end, the said Pegs are secured at the base of the said box. A Crucifix like in shape member, manufactured from steel of a specified size and material specification is secured to the base of the box, at a specified position within the three point Peg triangle.

Finally the blade is placed within the box resting on all three Pegs, having been firmly clamped in position a molten alloy metal is poured within the said box, which on cooling and solidifying encapsulates the blade.

The Billet of the Alloy material having a recessed Crucifix cavity to the underside face will be compatible with a former housed within the clamping surface of the machine, and provides a Dovetail like joint., the alloy billet can now be adequately clamped in position in readiness for machining.

-I-

For reference purposes the Alloy in present use, having a trade name MCP 137, (Mining Chemical Products), having a low melting point of approximately 137, degrees C', and contains both Bismuth and Tin. Not only is the waste content of material cost, in machining one blade a disadvantage, but the material itself gives rise to problems in handling, with regard to health and safety regulations, caused by the debris. Dirt and dust problems are also encountered during the first operation of moulding. The invention seeks to improve upon the various problems as herein before described.

Summary of the Invention.

Although the following description and accompanying drawings are to emanate the novel step of the invention, they are describing that of a prototype device manufactured to describe the concept only, for the benefit of demonstration, and not intended as a device in its present design status for production use. The principal of the concept will be employed within the production design and will be different in its detail production parts, to satisfy the design criteria of each turbine blade to be housed within the device, in readiness for machining of the said blade.

Fig. I. Cross-sectional elevation Fig.2 Plan view.

Fig.3 Sectional view on centre member.

Fig. 4 Sectional view on base member.

Fig. 5 Sectional view on diaphragm.

Fig. 6 Hand wheel Fig. 7 Plan and end elevation.

Item 8 Fig. 1, is a cross sectional view taken on the centre line of the device, having a width denoted by the dimension W' of 11 centimetres (110 millimetres), and a body height denoted by the dimension H' of 9 centimetres (90 millimetres).The device consists of three main members, that of a base section item 9 fig's 1 and 4, and a middle and top member items 10 and 11 fig's 1, 2 and 3.

Item 11 Fig's 1 and 2 is the top member having a dimension of 10 centimetres (100 millimetres), represented by the dimension X'.

A collar item 12 Fig's I and 2, having an internal threaded bore, is secured to the upper face by screw fasteners (not shown).

The middle member item 10 Fig's 1 and 3 is secured in position as shown. Using the threaded holes 13 Fig. 3, and Hexagon socket head screws (not shown) fitted on the underside of the base member item 9 Fig's 1 and 4, using the holes 9a. Spacing of the said holes is as follows, Eight holes in total are used (Four each side, their centre spacing is as those in the top member, and denoted by the letter C'.

Machined within the middle member item 10 Fig's 1 and 3 is a recess 14. This recess is for housing the diaphragm item 15 fig's 1 and 5. (for this description only Polyurethane is the plastic material used). The diaphragm is a commercial type moulding, where the base profile is contoured to the respective curvature and helix of the turbine blade (not shown).

A convex shaped block item 9b Fig's I and 4 is secured to the base member item 9, by screw fasteners (not shown). Alternatively the convex portion may be machined as an integral part of the base member item 9.

The two side sections items 16 Fig 1 and 4, and occupy the fill longitudinal length from front to back, are secured to the base item 9 by screw fsteners (not shown).

These two sections items 16, act only as spacers between the middle section item 10 and the base section item 9 The diaphragm item 15 Fig. 5 is shown in section, having a square shaped profile (and for this description is 6 centimetres (6omillimetres). Positioned central within the middle member item 10. For reference only, the diaphragm will be in a position of 20 millimetres from the front and back of the device. The said diaphragm is housed within the recess 14 fig. 3, having external dimensions compatible with the internal dimensions of the recess.

Finally, the three sections namely top, middle and base, are positively located accurately together, by the insertion of two circular dowels These are located within the two holesi la fig. 2, the said dowels pass through all three sections from the base to top section, and stop short of the upper top surface of the top member item 11 fig.2, as shown in fig.l.

A spindle item 17 fig. 6, having a knurled circular hand wheel at the upper part and a threaded portion 18, immediately below, where the thread form is compatible with the internal thread of the collar item 12 fig's 1 and 2. A further internal fine thread form 19 fig. 6, is contained within the upper part of the said hand wheel, and is compatible with the thread form of a commercial Air-Bleed nipple (not shown). The bores 20 and 21 are for purposes of bleeding air from within the Oil-Chamber of the middle member item 9 fig's land 4. A standard hydraulic lip seal item 22 fig's 1 and 6 is fitted by a screw and washer,(the screw will require a drilled hole through the entire length to allow for Air bleeding). The seal will be fitted to the lower end of the spindle, having an internal thread within the bore 20 fig.6, the seal will act as both a piston and oil seal. Having sufficient surface area to displace the hydraulic oil. The hydraulic oil is introduced within the inner part of the membrane before the top member item 11 is secured in position.

In production use, although the concept herein before described will require accommodating within the design criteria, it will be necessary to have various sizes of these devices, each having an inner membrane and lower former, that is compatible with the contour of each and every turbine blade. It may also be necessary, in particular with medium to large blade sizes to have a hydraulic hand pump, as an alternative to a hand wheel as herein before described., incorporating a pressure gauge indicating oil pressure level, to ensure positive contour effectiveness to provide sufficient grip of each blade requiring this procedure Finally, item 23 fig.7 is an alloy block shaped to a concave shape at one side to a length represented by the dimension L', the outer end is the root end of the simulated blade. That will require machining to the specifications and requirements necessary to satisfy the design criteria of the fished turbine blade.

To successfully demonstrate the effectiveness of the device as related in the aforesaid description, the method of operation will now be described in greater detail, The concave shaped opening between the diaphragm item 15 fig 5, and the lower concave shaped former item 9a fig. 4, will be used for inserting the simulated blade profile item 23 fig. 7. The outer block will be positioned outside of the device leaving some 75 percent of the concave part dimension L', encapsulated within the device.

The hand wheel of the spindle item 17 fig. 6 will be turned in a clockwise direction, causing the spindle to move in a downwards direction. Once the piston item 22 fig. 1 creates displacement of the hydraulic oil, causing the diaphragm to flex'. This will execute the lower side of the membrane to adhere to the upper contour of the said blade, forcing the blade in a locked position on the lower former block, this will ensure that the simulated blade item 23 fig 7is locked rigidly within the device. The blade is now ready to be presented to the machine tool. -4-.

Finally, that both within the Title and throughout the whole of the Description relate to that of a Turbine Blade. It is important therefore to note, that for example Stator' and Compressor' blades fitted to Jet engines, also Blades having an Airfoil section, with concave and convex blade surfaces combined with compound Radii and angle profiles, could also be clamped within the device.

This will require design and modification to specified components within the said device for each type of Blade to be adequately secured in position. -5..

Claims

CLAIMS1. A Hydraulically operated device consisting of three main parts, a lower base, middle section and top member, a moulded membrane positioned and encapsulated within the middle section having a concave base part compatible with a Airfoil blade contour, a oil reservoir is provided at the upper part of the said membrane with a hand operated spindle and piston, retained by screw threaded means within the upper member, the base section having a convex portion compatible with the said blade section, when the membrane and said blade are subjected to Hydraulic pressure resisted by the lower convex portion, this will then provide the necessary gripping' force to hold and retain securely in position the said blade.
2. A Hydraulically operated device as claimed in claim 1, whereby the said hand operated spindle can be replaced with a hydraulic hand pump and oil pressure gauge.
3. A Hydraulically operated device as claimed in claims I and 2, and substantially as herein before described with reference to the accompanying drawings. *,.( a a. a. * a. * .S* .*..a * a a * a a. ** * . a *