PREPARING A TUBE END FOR ROD DRAWING

Abstract

An apparatus for preparing a tube end for rod drawing with a floating mandrel has a releasable holder for the tube end centered on an axis, a frustoconical and spreadable floating mandrel, and a device for inserting the mandrel into the tube end and spreading the mandrel to flare the tube end. The apparatus further has a feed mechanism for inserting the floating mandrel into the tube end and/or a deforming device for making at least one indentation in the tube for holding the floating mandrel.

Claims

1. An apparatus for preparing a tube end for rod drawing with a floating mandrel, the apparatus comprising: a releasable holder for the tube end centered on an axis; a frustoconical and spreadable floating mandrel; and means for inserting the mandrel into the tube end and spreading the mandrel to flare the tube end.

2. The apparatus defined in claim 1, further comprising: a deforming device for forming a first indentation in the tube for gripping the floating mandrel.

3. The apparatus defined in claim 1, wherein the mandrel has an injector for introducing drawing oil into the tube.

4. The apparatus defined in claim 2, wherein the deforming device form the first indentation axially in front of the mandrel and a second indentation axially behind the mandrel and spaced from the first mandrel.

5. The apparatus defined in claim 4, wherein the mandrel has a head axially captured in the tube between the indentations.

6. The apparatus defined in claim 4, wherein the tube can be held by the first indentation in a form-fitting manner axially of the tube when the spreadable mandrel widens the tube end.

7. The apparatus defined in claim 2, wherein the deforming device has at least two pressing pins spaced axially from one another and pressable independently of one another against the tube end.

8. The apparatus defined in claim 1, further comprising: a pointing press for imparting a pointed shape to the tube end for drawing tongs after introduction of the floating mandrel.

9. A method for preparing a tube end for rod drawing, the method comprising the steps of: a) holding the tube centered on an axis; b) forming a first indentation in the held tube end with a deforming device; c) widening the tube end of the held tube with a frustoconical spreadable mandrel while holding the tube end against axial movement by engagement of the deforming device in the first indentation; and d) introduction a floating mandrel into the tube end until before the first indentation.

10. The method defined in claim 9, wherein the tube end is widened by the frustoconical spreadable mandrel before the feed mechanism introduces the floating mandrel into the tube end.

11. The method defined in claim 9, wherein the tube end has a non-rectangular undefined cut edge, and the spreadable mandrel is engaged in the tube end without any correction of the cut edge.

12. The method defined in claim 9, further comprising the step of: forming a second indentation by the deforming device, with the floating mandrel being caught between the first and second indentations.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0031] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

[0032] FIG. 1 is a side view of a part of an apparatus according to the invention;

[0033] FIG. 2 is a top view in enlarged scale of a detail of the apparatus of FIG. 1 after a first tube process step;

[0034] FIG. 3 is a large-scale view of a detail of FIG. 2 during a second process step;

[0035] FIG. 4 is a view like FIG. 3 showing the apparatus 2 before the introduction of a floating mandrel into the tube;

[0036] FIG. 5 is another view like FIG. 3 after introduction of the mandrel;

[0037] FIG. 6 is yet another view like FIG. 2 after an additional tube process step; and

[0038] FIG. 7 is another detail view of the apparatus in side view as in FIG. 1 after pointing of the tube.

SPECIFIC DESCRIPTION OF THE INVENTION

[0039] As seen in FIG. 1 the apparatus of this invention has a frame 1 on which several displaceable elements are incorporated. A releasable holder 2 for receiving a tube 3 on the frame 1 has a gripper 2a that holds a tube 3 without marring or damaging it. The tube 3 is preferably made of a soft metal such as copper. It has one end 4 with a cut edge 4a that is largely undefined in terms of angle and orientation. Along most of its length the tube 3 is held in a drum (not shown) that supplies it to a drawing station after formation of the tube end 4 according to the invention. Alternatively, the apparatus according to the invention can also be movable as a whole and moved to a respective tube for forming the tube end 4.

[0040] After the tube end 4 is gripped in the holder 2 so the tube is centered on a normally horizontal axis A, a deforming device 5 engages over the tube end 4. The deforming device 5 comprises two spaced pressing pins 6 and 7 controlled by respective hydraulic cylinders 6a and 7a. Here, the pressing pins 6 and 7 are each formed by at least two opposing or mutually counteracting pairs of pins. Alternative arrangements with only one single pressing pin 6 and 7 and a corresponding abutment are also possible.

[0041] The deforming device 5 is carried on an arm 8 that can be pivoted by an actuator 8a about an axis 8b toward and away from the tube end 4. In addition to the deforming device 5, a clamp 9 with a clamps 9a for the tube end 4 is carried on the pivot arm 8.

[0042] A spreadable mandrel 10 with a frustoconical outer surface is carried on a mandrel support 11 that can be displaced on the frame. The mandrel support 11 can be moved automatically along the frame 1 axially of the tube 3 held in the holder 2 in order to insert the spreadable mandrel 10 into the tube end 4 (see FIG. 2). The spreadable mandrel 10 can then be driven forward automatically axially of the tube, which is horizontally in the present case. The spreadable mandrel enters the tube end 4 and flares it (see FIG. 3).

[0043] As indicated in FIGS. 3 and 4, the cut edge 4a of the tube end 4 has an undefined angle, in which case sufficient guidance and widening is ensured nonetheless by the small apex angle of the spreadable mandrel 10.

[0044] In order to achieve good holding and supporting of the tube 3 in the tube axial direction during widening, a first indentation 4b is formed in the tube 3 by the first pressing pin 6 before the spreadable mandrel widens the end. The pressing pin 6 remains initially in the inserted position in the indentation 4b so that the tube 4 is solidly gripped and cannot move axially (see position of the pressing pins 6 and 7 in FIG. 2). The forces of the spreadable mandrel 10 acting in the tube axial direction are thus transmitted to the frame 1 mainly by the first pressing pin 6 or the deforming device 5 via the pivot arm 8. Movement of the tube 3 during widening is effectively prevented. At this time, no indentation is yet made in the tube end 4 by the second pressing pin 7.

[0045] In addition, the spreadable mandrel 10 has a central passage 10a that acts as part of an injector for supplying drawing oil into the interior of the tube 3 in its end region. The drawing oil is expediently injected during widening, so that the friction of the spreadable mandrel can also be reduced. The drawing oil facilitates sliding of a floating mandrel 12 introduced into the tube end 4 after widening.

[0046] The floating mandrel 12 is releasably mounted on a lance-shaped feed mechanism 13. The feed mechanism 13 is held laterally adjacent the spreadable mandrel on a support 14 that can be displaced transverse to the tube axis A on the frame 1. The support 14 receives both the mandrel support 11 of the spreadable mandrel 10 and the feed mechanism 13 of the floating mandrel 12.

[0047] After the radial widening or flaring process described above, the spreadable mandrel 10 is retracted and the support 14 moves into a position in which the floating mandrel 12 is aligned along the axis with the now widened tube end 4. The mandrel 12 is now introduced by the feed mechanism 13 into the tube end 4 (see FIG. 5). The mandrel 12 ultimately comes to rest behind the first indentation 4b.

[0048] A second indentation 4c is then formed in the tube 3 by the second pressing pin 7, so that a head of the floating mandrel 12 is caught between the first indentation 4a positioned in front of the head of the mandrel 12 and the second indentation 4b positioned behind it (see FIG. 6). The feed mechanism 13 is now released from the mandrel 12 and retracted.

[0049] A pointing press 15, which is also held in a movable manner on the frame 1, then moves into position and presses the end of the tube 3 to a reduced diameter. This process is also referred to as the pointing of the tube end 4.

[0050] The tube end 4 prepared in this manner can be grasped in the pointed region using unillustrated drawing tongs and pulled through a die. The floating mandrel 12 is carried along in a known manner.

[0051] It will readily be understood that the entire process described above takes place continuously and automatically, particularly in a computer-controlled manner, from the initial supporting of the tube end 4 through the conclusion of the pointing.

[0052] Analogously with the individual stations and procedures described above, a method for preparing the tube end 4 comprises the following automatically proceeding steps: [0053] a) centered supporting of the tube end 4 in the holder 2 (see FIG. 1); [0054] b) forming the first indentation 4b by the deforming device 5, 6 (see FIG. 2)l [0055] c) widening of the tube end 4 by the tapered spreadable mandrel 10, with the tube end 4 being held axially of the tube by the deforming device 5, 6 and the first indentation 4b (see FIG. 3); [0056] d) introduction of the floating mandrel 12 into the tube end 4 until immediately behind the first indentation 4b (see FIG. 5); [0057] e) forming the second indentation 4c by the deforming device 5, 7, with the floating mandrel 12 between the two indentations 4b, 4c (see FIG. 6); and [0058] f) pointing the tube end 4 by the pointing press 15 (see FIG. 7).

[0059] In the example described above, the holder 2 and the deforming device 5 are separate units arranged so as to be spaced from one another. In unillustrated alternative embodiments of the invention, the holder and the deforming device can also be an integral unit. Depending on the details of the design, the deforming device can have one or more separately actuatable pressing pins in a manner similar to the described example. In an especially simple design, at least one of the pressing pins can be embodied as a fixed projection in the holder, so that closing the holder simultaneously forms an indentation in the tube end. In this case, the steps of the supporting of the tube end and of the formation of an indentation are not carried out automatically in a successive manner, but rather automatically in a simultaneous manner.