Hose machinery

Hose Machinery

A large variety of hose constructions are produced by the rubber industry for a wide range of applications. To contain transported liquids, usually under pressure, it is necessary to reinforce the hose construction with fabric, yarn or short fibres to constrain expansion of the rubber. Although hand-built construction using fabric still represents a proportion of the production, it is also very common to use yarns either braided or knitted directly onto the hose liner. For heavy duty purposes it is also necessary to use wire, in a braided form, to either reinforce or protect the hose from external  damage.  Use  of  short  fibres  as  reinforcement  represents  a  small  proportion of hose production and requires specialised dies for extrusion to orientate the fibres circumferentially.

Braiding Machineries

Braiding of rubber products, i.e., hoses, can be with either yarns produced from cotton or synthetic fibres, or metals, depending on the use of the hose. The principles of use of the braider are the same for both types of filaments. The yarns are laid down from the braiding machine in a similar manner to that of a maypole, the cross-over angle of the braid is critical to the stability of the hose in use. The correct angle of cross-over for the yarns, known as the Neutral Angle, is at 54 degrees to the axis. Angles greater than 54 degrees will cause the hose to grow longitudinally under pressure. A braiding angle of less than 54 degrees will cause the hose to grow in diameter.

Braiding hoses with wires to resist high burst pressures or for external protection is common, using a braiding machine. The wires used, usually of steel, will be either zinc- or brass-coated to achieve adhesion during vulcanisation. The gauge of the wire and its tensile properties will be matched to the expected service demands for the hose.

The bobbins of the braiding machine are loaded with the appropriate number of wire filaments to achieve the desired structure.

Braiding  machines  are  of  two  basic  types  vertical  and  horizontal  and  both  find  application depending upon the type of hose being manufactured.

                                                     Vertical hose Braiding 

                                                   Horizontal Hose Braiding 

Wire/Bobbin Winders

As with reinforcing textile cords it may be necessary to rewind treated wire from production spools to smaller unit spools for specific machines, such as braiders.

 Knitting Machines

There are two types of knitting used in rubber product construction, i.e., warp knitting and weft knitting.

Warp Knitting

The basic stitch produced in warp knitting is the chain stitch. The yarn is looped around the needle stem and another loop of the yarn is formed in the hook of the needle and is then pulled through the first loop, itself then becoming the loop held on the needle shaft, whilst another loop is formed in the hook. In this way a chain of interlaced loops is formed. By displacing every other loop onto the next needle, the chains of interlaced loops are linked together to form the simple knotted tricot structure. If one of the yarn loops become broken in this type of fabric then the whole fabric, in the line of the yarn, will ‘unzip’. This problem can be overcome by displacing the throw of the stitches.

Weft Knitting

In this method the looping yarn runs transversely to the length of the fabric. Loops are formed on a row of needles and the next loops are caught in the hooks of the needles and then drawn through the first loops. Weft knitting machines normally give a circular product and can be used to form the

reinforcement continuously around an extruded hose liner. Weft knitted fabric is very flexible, having high tear resistance, and is used in many types of hose structures for vehicle applications.

These fabrics can be applied in the hand-built construction of hoses in a spiral form at an angle to the axis of the hose. The knitted fabric can also be produced directly onto the surface of the inner liner of a hose and subsequently be covered with the outer cover compound by a cross-head extrude.

Hose Builders

Hose may be hand built using a three roll wrapping machine. The centres of the three rolls form an equilateral triangle. The hose during construction sits on the junction between the two lower rollers and pressure is exerted to consolidate the composite by the upper movable roller. An extruded inner liner, after fitting to a solid inner mandrel, is placed into the machine between the rollers and then the various layers of rubber coated or resorcinol-formaldehyde-latex treated, fabric are applied in a spiral form, with overlap. Once the reinforcement layers have been added the cover rubber is applied and a cloth, usually nylon, is spirally wrapped around the constructed hose using the roller system. The hose can undergo  vulcanisation process.