Abstract:
Continuous extrusion apparatus includes a rotatable wheel, the rotatable wheel including a circumferential groove. Continuous extrusion apparatus includes a shoe including an arcuate tooling bounding a radially outer portion of the groove provided with an exit aperture in a die body and an abutment displaced in the direction of rotation from the exit aperture. The shoe includes a heater body assembly including an electrical induction heating coil assembly arranged to be energisable to co-act with a magnetisable element to effect electrical induction heating thereof; and an element is provided to thermally induce movement of co-acting members for one of expanding and contracting to adjust clearances between the rotatable wheel and the abutment and the shoe within requisite limits.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of application Ser. No. 11/200,192, filed Aug. 10, 2005, now U.S. Pat. No. 6,988,389 to Hawkes, issued Jan. 24, 2006, which is a continuation of application no. PCT/GB2004/000701, filed Feb. 20, 2004, now WO 2004/073901 A1 to Hawkes, published 2 Sep. 2004, and which claims priority of United Kingdom application no. 0304114.2, filed Feb. 22, 2003, and each of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to apparatus for the forming of metals by a continuous extrusion process in which feedstock is introduced into a circumferential groove in a rotating wheel to pass into a passageway formed between the groove and arcuate tooling extending into the groove. 
   BACKGROUND OF THE INVENTION 
   WO 2004/073901 discloses continuous extrusion apparatus having a rotatable wheel formed with a circumferential groove, shoe means including arcuate tooling bounding a radially outer portion of the groove provided with an exit aperture in a die body and an abutment displaced in the direction of rotation from the exit aperture, the shoe means being provided with a heater body assembly including an electrical induction heating coil assembly arranged to be energisable to co-act with magnetisable means to effect electrical induction heating thereof. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   According to the present invention means are provided to thermally induce movement of co-acting members to expand or contract to adjust clearances between the rotating wheel and the abutment and shoe within requisite limits. 
   Preferably, the abutment is positioned on a die extension piece seated on a shoulder formed on the shoe and means are provided to induce thermal expansion of the die extension piece to adjust radially the position of the abutment relative to the rotatable wheel. 
   Relative terms such as left, right, up, and down are for convenience only and are not intended to be limiting. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partly diagrammatic, cross-sectional side view of continuous extrusion apparatus including a die heater body assembly  11 , together with a die extension piece heater body assembly  102 , and a stop block heater body assembly  104  according to the invention; and 
       FIG. 2  is a partially exploded perspective view of the die body heater assembly of the continuous extrusion apparatus according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Additionally, the shoe is mounted on a pivot  10  extending parallel to a drive shaft of the rotatable wheel and is urged against an elongated stop block positioned adjacent the rotatable wheel by means of a hydraulic ram bearing against a second shoulder formed on the shoe and means are provided to thermally expand or contract the elongated stop block to adjust the disposition of the shoe in relation to the rotatable wheel. 
   The invention will now be described, by way of example, in  FIG. 1 , with reference, in part, to the arrangement of continuous extrusion apparatus described in WO2004/073901 in conjunction with EP-A-0071490 and, in the main, to the accompanying, partly diagrammatic, cross-sectional side view of continuous extrusion apparatus including a die heater body assembly  11  similar to that shown in WO 2004/073901 together with a die extension piece heater body assembly  102  and a stop block heater body assembly  104 . 
     FIG. 2  shows the partly diagrammatic, isometric, exploded view of the die body heater assembly described in WO 2004/073901. 
   The die heater body assembly  11  includes an entry block  13 , a die block  15 , a centrally apertured bucket portion  17  and a die heater body  19 . 
   The die heater body  19  includes a helical coil of copper tubing set in ceramic support material to form an electrical induction heating coil assembly  21  provided with electric power and cooling water connections  23  extending rearwardly through the shoe. Low reluctance magnetic members  25  are positioned outwardly of the electrical induction heating coil assembly  21  and typically are formed of six millimetre thick stampings  27  of “Silicon-Iron” alloy having a high saturation magnetism and a Curie point in excess of 800° Celsius, spaced apart to form three millimetre gaps, mounted on a centrally apertured base plate  29 . End portions  31  of the stampings  27  are connected to first and second magnetic material end blocks  33  and  35  and  37 , the second end blocks  35  and  37  being separated by gap  39  to restrict eddy current circulation. A corresponding gap is formed in the base plate  29 . 
   The entry block  13  is formed with the die block  15  of non-magnetic material co-acting with the bucket portion  17  of magnetic material co-acting, in turn, as a sliding fit, with a pocket  41  in the die heater body  19 . Dowels (not shown) locate the end blocks  33 ,  35  and  37  on the shoe means whilst allowing differential thermal expansion. An abutment  43  is positioned on the die block  15  at a location displaced in the direction of rotation from a port  45  leading to a central aperture arranged to receive an extrusion die (not shown), located in the bucket portion  17  of the die block  15 . 
   Thin shims  47  of heat insulating material, such as mica, are positioned intermediate the end block  33 ,  35  and  37 , base plate  29  and the shoe to limit heat transmission to the shoe. 
   A thermocouple and lead  38  are provided to give a signal indicative of the temperature of the die heater body  19 . 
   The centrally apertured base plate  29  of die heater body assembly  11  seats on a forward end face  106  of the die extension piece heater body assembly  102  which, in turn, seats on a shoulder  108  formed in an extension  110  of the aperture  112  in the shoe housing the die heater body assembly  11 . The extension piece heater body assembly  102  is of a generally similar construction to that of the die heater body assembly  11 , and is provided with a thermocouple and lead  114 . 
   The shoe  8  is mounted on a pivot  10  extending parallel to a horizontal drive shaft  4  and is urged against a stop  12  positioned adjacent the wheel and above the drive shaft  4  by means of a main hydraulic ram  14  bearing against a shoulder  16  formed on the shoe  8 . 
   A stop block heater body assembly  104  is positioned on the stop block and is of generally similar construction to that of the die heater body assembly  11  and is provided with a thermocouple and lead  116 . 
   In operation, the shoe  8  is pivoted into position abutting the stop  12  and the wheel  2  and fluid supplied to the main hydraulic ram  14  to urge the shoe  8  against the stop  12 . The stop block heater body assembly  104  having previously been energised by passing an electrical current at a power level of approximately twelve kilowatts and a frequency of approximately 50 Hertz through the electrical induction heating coil assembly to raise the temperature of the stop block by around 200° C. to thermally expand the stop block  12  to a datum position. 
   The extension piece heater body assembly  102  is energised by passing an electrical current at a power level of approximately twelve kilowatts and a frequency of approximately 50 Hertz through the electrical induction heating coil assembly to raise the temperature of the extension piece by around 200° C. to thermally expand the extension piece to a datum position. 
   With the entry block  13 , the die block  15  and the bucket portion  17  positioned in the die heater body  19  to form the die heater body assembly  11  and positioned in the shoe of the continuous extrusion apparatus and with copper feedstock being urged to the entry block  13  and die, the bucket portion  17  is inductively heated to a temperature of approximately 700° Celsius by passing an electrical current at a power level of approximately twelve kilowatts and frequency of approximately 50 Hertz through the electrical induction heating coil assembly  21  to maintain the die, by conduction, at a temperature of 700° Celsius, thereby greatly facilitating the extrusion process through the die. 
   As the extrusion operation proceeds, over time the clearances between the shoe  8  and the wheel  2  vary from the initial settings, so that it is desirable to adjust the clearances to maintain the original settings or a requisite modification thereof without interrupting the extrusion process. To that end, the energy to the extension piece heater body assembly  102  is increased to raise the temperature of the extension piece and produce thermal expansion of the extension piece by an amount sufficient to move the abutment  43  toward the wheel  2 , by virtue of the entry block  13  being seated on the face  106  of the extension piece heater body assembly  102  which, in turn, seats on the fixed shoulder  108  in the shoe  8 . Decreasing the clearance between the abutment  43  and the wheel  2  toward the original setting reduces the amount of flash material escaping from the gap between the abutment block and the wheel. 
   The energy to the extension piece heater body assembly  102  is decreased to reduce the temperature of the extension piece and produce thermal contraction of the extension piece by an amount sufficient to move the abutment  43  away from the wheel  2 , by virtue of the entry block  13  being seated on the face  106  of the extension piece heater body assembly  102  which, in turn, seats on the fixed shoulder  108  in the shoe  8 . Increasing the clearance between the abutment  43  and the wheel  2  toward the original setting increases the amount of flash material escaping from the gap between the abutment block and the wheel. 
   To counteract movement of the shoe  8  in relation to the wheel  2  as the extrusion process proceeds over time, the heat input to the stop block  12  is reduced or increased by small steps to vary the position of the stop  12  in relation to the wheel  2 . Since the operating fluid of the hydraulic ram is maintained at constant pressure, the shoe  8  is urged against the stop  12  and the shape of the gap between the shoe  8  and the wheel  2  is maintained at an optimum disposition to minimise the escape of feed material as flash, since the shoe  8  is rotated about the pivot  10 . 
   The respective thermocouples and leads  38 ,  114  and  116  are arranged to provide signals indicative of the temperatures of the die body heater assembly  11 , the die extension piece heater body assembly  102  and the stop block heater body assembly  104  respectively, which signals may be input into a control system directed toward achieving optimum extrusion conditions. 
   The amount of flash produced is readily observable visually and by making incremental adjustments to the power inputs to the heater body assemblies  102  and  104  to adjust the associated clearances the formation of flash is thereby adjusted. 
   In an alternative arrangement, not shown, the die body heater assembly  11  seats directly on a shoulder formed in the aperture  112  in the shoe  8  and is of such a length and of a material having a coefficient of thermal expansion sufficient to give rise to a requisite thermal expansion within the range of operating temperatures of the die block to move the abutment block toward the wheel to maintain a desired clearance between the abutment block and the wheel, thereby minimising the amount of material issuing as flash. 
   Thus, in operation, the continuous extrusion apparatus is set up and brought up to an operating temperature at the die block of, say, 500° C. and extrusion of copper tube from continuous copper rod feedstock is commenced. As extrusion proceeds, the operating gap between the abutment block and the wheel tends to increase, resulting in an increasing formation of escaping flash material. To counteract the increase, the energy input into the heater block assembly is increased to produce increments in the temperature of the assembly in, say, 20° C. increments such that the resulting thermal expansion of the die body moves the abutment block toward the wheel to restore the gap to the original, predetermined, dimension and thereby limit the amount of flash material produced. 
   It will be appreciated that, in some circumstances, it will be sufficient to adjust the gap between the abutment and the wheel to restrain the escape of flash material, over time, within acceptable limits, and in such circumstances the heater body assembly associated with the stop block  12  may be omitted. 
   It further will be appreciated that means other than electric induction heating coils may be utilised to supply or reduce heating to produce the requisite thermal expansion or contraction. 
   While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, and uses and/or adaptations of the invention and following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the invention pertains, and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention or limits of the claims appended hereto.