1 Title of the Invention

Hydraulic Shape Memory Alloy (SMA) Ferrule Expander Machine

2 Field of the Invention

The present invention relates to improvement in expansion of the SMA Ferrule (Rings) in presence cryogenic liquid (i.e., liquid Nitrogen) with the application of Hydraulic force by means of SMA Ferrule expander machine.

3 Background of the Invention

The Fighter aircrafts use around 190 Nos. of 5 different sizes of Shape Memory Alloy (SMA) ferrule, rings for clamping Insulators (Non-metallic PEEK- Poly Ether Ether Ketone) onto the Aluminium alloy tubing. These insulators are introduced in the Aluminium pipe lines to break the electrical conductivity.

Shape Memory Alloy (SMA), is an advanced functional material which is also known as “Smart alloy"/ "Memory metal”. Shape Memory alloy "remembers" their sha^e. After afiSMA component has been deformed from its original shape; it regains its original geometry by itself during heating above its transformation temperature. This unique property is only seen in Shape Memory alloys. Most commonly used Shape Memory alloy is Nitinol which is an alloy nearly equal proportion of Nickel & Titanium.

SMA Ferrule rings of sizes 20, 25, 32 40 and 50mm are being used in fighter aircrafts. Once these ferrules are made, they are subjected to , quality inspection by using a manual expander setup. These SMA Ferrules are made of Ni-Ti-Fe Alloys. They are machined out from rolled / forged shape memory alloy plates, with their inside diameter smaller than the outside diameter of the PEEK Insulator Tubes .These Ferrules are mechanically expanded at cryogenic temperatures till their inside diameter becomes larger than the outside diameter of the PEEK Insulator Tube.
They are then fixed to the tubes in the expanded condition at cryogenic temperature. As they revert to room temperature, they return to their original shape, shrinking down onto the tube with a high radial force and constant clamping stress to form a permanent metal to metal seal which is vibration and leak proof. The advantages of SMA couplings are lesser weight, leak proof joints and uniform clamping pressure, compared to conventional couplings.

Every SMA ferrule is manually expanded under liquid nitrogen environment to see that the expansion is met as per the inspection standards. After the inspection the quality inspected Rings are supplied to the assembly shops wherein by using similar manual expander tools, expansion of ferrules will be done and assembly of the SMA ferrule ring over the pipe joints will be carried out.

Hence, there was a need to establish a hydraulic force based SMA ring expansion machine to work at cryogenic temperature, at low cost and indigenously to develop the technology within India. This has led to the below mentioned invention.

3.1 Prior Art

There is no past invention available for SMA ferrule expander machine working at cryogenic temperature. Previously these rings were expanded by wratchet which is ‘a laborious and time consuming process. The operation of manual expander tools are done by using the manual force to the order of 140 to 160 N-m torque. As this operation needs to be done at cryogenic temperature, with shorter period of time, and involves high rejection rate. The nearest existing patents in the field viz., 1) U.S patent titled “Oil ring with coil expander” US4194747A & 2) US patent titled “Monobore construction with dual expanders” US4738708P, are not suitable to the requirements, the costs of such machines are high, and are not suitable for cryogenic temperature applications.
4 Brief Summary of the Invention

A hydraulic machine was designed and fabricated with a provision for moving table mounted over a linear motion guide ways. A chamber to hold the expansion die holder with liquid nitrogen was designed and fabricated in house. The chamber was fabricated to accommodate the die holders of sizes 20mm, 25mm, 32mm, 40mm and 50mm.

A double acting hydraulic cylinder was fabricated. The hydraulic cylinder mounted over MS Top Frame with two columns. The MS Top Frame, Steel columns and the hydraulic cylinder was mounted over the MS table in a way the moving table is placed between the two columns.

Expander mandrels fo^ the die as per sizes mentioned above was designed and fabricated and mounted over the piston of hydraulic cylinders. A mandrel and its corresponding tool to the die holder will be in operation for expanding respective size of the SMA ferrules. A Mandrel tool holder (10) was fabricated to fasten the various sized mandrel to the piston of the hydraulic cylinder. The other end of the mandrel tool holder is fastened with respective mandrel. The Centre of the die holding chamber was made to fall in line with the centre of the piston of the hydraulic cylinder in order to achieve concentric expansion of the SMA Ferrules. The die holder was locked with the die holder chamber by using M8 CSK alien bolts. The die holder was made with 40mm square impression at the bottom end in order to ensure concentric of the die holder with respect to die holder chamber and centre of the hydraulic piston.

A hydraulic power pack was fabricated with the following specifications . and connected to the hydraulic cylinder of the machine.

a) 4 LPM gear pump

b) 3HP Motor

c) Direction Control valve
d) Pressure switch and relief valve

e) Check valve

f) Hydraulic tank of 30 Ltr capacity

g) Hydraulic Oil VG 68

h) 2 Mtr long hydraulic hoses

i) Pressure gauges and filters

The hydraulic power pack was assembled and hydraulic cylinder of the machine was connected to hydraulic pack through the hydraulic hoses. The pressure of the hydraulic cylinder can be adjusted to 160 bar Max. Based on load cell calculation we understood that when we expand the ferrule rings manually, around 1.2 to 1.6 tons of vertical force is required to expand all varieties of SMA ferrules. To overcome this, hydraulic cylinder was designed with 63mjjn bore size. Hence, with the pressure range of 40 to 60 kg/cm2.Accordingly, the hydraulic power pack is tuned to give hydraulic press at 40 bar and variable up to 60 bar.

5 Detail Description of the Drawings

Fig.1 schematically illustrates the views depicting all the components explicitly.

Fig.2: Exploded view of the machine.

Fig-3 : Die Holder and mandrel details

6 Detail Description of the Invention

1) Hydraulic Force based SMA ferrule expansion machine is designed for 20, 25, 32, 40 and 50mm SMA Ferrules in order to save production time and to increase productivity.

2) This Hydraulic ferrule expansion machine expands SMA Ferrules at a very faster rate for inspection and assembly as well.
3) This machine controls hydraulic force by varying the hydraulic pressure, so controlled expansion of SMA ferrules (5% of expansion on diameter is expected as per the design of SMA ferrule) is can be achieved.

4) The SMA ferrules are expanded using this machine were assembled over the Aluminium fuel pipes of an aircraft and found passed on all quality inspection parameters at the assembly unit.

5) The die holder chamber is fastened with the moving table which in turn is mounted over LM guides as such when the mandrel gets retracted the die holder(7) and SMA ferrule are undisturbed for the upward movement of the mandrel.

Construction

The hydraulic expansion machine is fabricated over a steel table (1) and hydraulic cylinder (5) is assembled over steel columns (3) and Top Frame (4). The Steel table is assembled with moving table (2) mounted over LM guide ways (12).The hydraulic power pack (13) generates the required hydraulic pressure. This pressurized hydraulic oil is fed to the hydraulic cylinder through the hoses (11) .Upon activation of forward movement via control panel (14), the expander mandrel (9) comes down into the die holder (7). The die holder is already assembled with die inserts (8) and SMA ferrule rings (16) for expansion, under the transition temperature i.e., -50 to -60° C as the die holder chamber (6) is filled with liquid nitrogen.

Function

Once the transition temperature is achieved with help of liquid nitrogen, ithe expander mandrel from the mandrel holder (10) of the hydraulic cylinder starts expanding the SMA Ferrule (16) till it touches the stopper Ring (15) of the die holder. Then the expander SMA Ferrule ring is taken out of the die holder and inserted over an inspection gauge to inspect the actual expansion radius of the ring as per the design.
The same operation is repeated for all the ferrule rings which are meant for expansion. In a similar way the SMA ferrule are expanded for assembly over the fuel pipes.

Referring to Figures 1,2 and 3, the hydraulic expansion machine is fabricated over a steel table (1) and hydraulic cylinder (5) is assembled over steel columns (3) and Top Frame (4). The Steel table is assembled with moving table (2) mounted over LM guide ways (12). The hydraulic power pack (13) generates the required hydraulic pressure. This pressurized hydraulic oil is fed to the hydraulic cylinder through the hoses (11).Upon activation or forward movement via control panel (14), the expander mandrel (9), which is held by mandrel holder (10) comes down into the die holder (7). The die holder is already assembled with die inserts (8) and SMA ferrule rings (16) for expansion, the expansion proceeds till it reaches stopper ring (15).

The die holder chamber (6) is filled with liquid nitrogen to initiate the transition temperature required for SMA ferrules (-50 to -60° C).