US3753365A

US3753365A - Swaging machine for the internal profiling of tubular workpieces

Info

Publication number: US3753365A
Application number: US00246137A
Authority: US
Inventors: B Kralowetz
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-05-06
Filing date: 1972-04-21
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21
Also published as: GB1349238A; FR2135189B1; DD96866A5; AT305734B; DE2218667A1; FR2135189A1; DE2218667C3; JPS5146510B1; DE2218667B2

Abstract

Mandrel means formed with a shoulder are adapted to enter said workpiece so that the latter surrounds said shoulder. A plurality of dies are spaced around said mandrel means and adapted to swage said workpiece onto said mandrel means. A gripping head surrounds said mandrel means and is adapted to axially support said workpiece at one end thereof and operable to rotate said workpiece about its axis and to advance it toward said dies at the same time. A holder-up is adapted to axially support said workpiece at the opposite end thereof and movable in the axial direction of said workpiece. Means are provided to apply a hydraulic backpressure to said holder-up so that the same yieldably resists the movement of said workpiece as the same is advanced by said gripping head. The gripping head comprises means defining a chamber adapted to contain a cushion of liquid under pressure, which cushion is adapted to axially support said workpiece, and a piston interposed between said cushion and said workpiece and surrounding said mandrel means. The machine also comprises valve means operable to reduce the pressure of said cushion when said shoulder enters between said dies.

Description

United States Patent 1191 Kralowetz Aug. 21, 1973 SWAGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES [76] Inventor: Bruno Kralowetz, Weinleiten 142,

St. Ulrich near Steyr, Austria [22] Filed: Apr. 21, 1972 [21] Appl. No.: 246,137

[30] Foreign Application Priority Data Primary Examiner-Lowell A. Larson Attorney-Kurt Kelman r H 7 s 24 25 u 57 Y ABSTRACT Mandrel means formed with a shoulder are adapted to enter said workpiece so that the latter surrounds said shoulder. A plurality of dies are spaced around said mandrel means and adapted to swage said workpiece onto said mandrel means. A gripping head surrounds said mandrel means and is adapted to axially support said workpiece at one end thereof and operable to rotate said workpiece about its axis and to advance it toward said dies at the same time. A holder-up is adapted to axially support said workpiece at the opposite end thereof and movable in the axial direction of said workpiece. Means are provided to apply a hydraulic backpressure to said holder-up so that the same yieldably resists the movement of said workpiece as the same is advanced by said gripping head. The gripping head comprises means defining a chamber adapted to contain a cushion of liquid under pressure, which cushion is adapted to axially support said workpiece, and a piston interposed between said cushion and said workpiece and surrounding said mandrel means. The machine also comprises valve means operable to reduce the pressure of said cushion when said shoulder enters between said dies.

8 Claims, 4 Drawing Figures SWAGING MACHINE FOR THE INTERNAL PROFILING F TUBULAR WORKPIECES This invention relates to a swaging machine for the inside profiling of tubular workpieces, particularly of barrels of firearms, by die impacts over an offset mandrel, in which machine the workpiece is gripped be tween a gripping head, which feeds the workpiece to the dies and rotates it at the same time, and a holderup, which is subjected to a constant backpressure by a liquid and against said backpressure is 'forced back as the workpiece advances, and the mandrel is secured to a rod, which extends through the gripping head.

Because the workpiece is gripped between the gripping head at one end and the holderup at the other end, the swaging results in a more accurate inside "profile as the length of the workpieces cannot 'be changed by the die blows so that the depth action of each blow is increased. it has now "been found that the use of a constant gripping force cannot lead to satisfactory results if an internal shoulder is formed in one-operation, e.g., a chamber is formed next to the grooved barrel. When the workpiece has been swaged onto the shoulder-forming portion of the mandrel so that a sharp edged shoulder has been formed, said shoulder will be stretched as the advance of the workpiece under the dies is continued and the axial flow of material forces the previously swaged internal edge away from the associated shoulder of the mandrel. During the next die blow, the mandrel shoulder is then forced into the workpiece once more so that inaccurate steps similar to a flight of stairs are formed.

To avoid this disadvantage, a swaging machine has been developed in which the workpiece is also firmly axially supported by the gripping head but the hydraulic backpressure applied to the holder-up in dependence on the desired internal shape of the workpiece portion disposed between the dies at any time can be automatically varied by means of at least one valve or the like, which is incorporated in the return conduit for the displaced liquid under pressure. As a result, the presstressing force applied to that portion of the work piece which is adjacent to the holder-up is not constant but increases when an internal shoulder or the like is being swaged so that the workpiece cannot be stretched toward the holder-up and material cannot flow from the previously swaged shoulder formed under the action of the mandrel at the beginning of the chamber. Practice has shown, however, that the forces which arise are often too large or the holder-up cannot apply the large backpressure forces required to prevent a stretching of the workpiece so that a satisfactory forging cannot be produced.

It is thus an object of the invention to eliminate this disadvantage and so to improve a forging machine as defined first hereinbefore that a satisfactory inside profiling of workpieces having internal shoulders is ensured.

In accordance with the invention, this object is essentially accomplished in that the workpiece is axially supported in the gripping head by a cushion of liquid under pressure through the intermediary of a piston, through which the mandrel extends, and the pressure applied to said cushion is adapted to be reduced by a valve or the like, which is preferably adapted to be additionally connected to the circuit, when the step of the mandrel enters the swagingzone between the dies. Hence, when it is desired to forge a shoulder the backpressure isnot increased but the pressure of the cushion of liquid under pressure is reduced so that the material of the workpiece adjacent to the grippinghead can flow toward the gripping head. This has the important advantage that even when the advance of the workpiece is continued does the material of the workpiece hug the step-forming shoulder of the mandrel and is not forced away from said shoulder in the feeding direction. Once the shoulder has been swaged, it is preserved as the swaging is continued, and a formation of inaccurate steps similar to a flight of stairs need not be feared. Excessively strong forces are also avoided because during the swaging of a shoulder the axial prestressing force need not be increased but is even reduced adjacent to the gripping head.

It will be particularly desirable if the cylinder chamber which contains the cushion of liquid under pressure is fed by a pump through a conduit which is provided with a check valve and a pressure-regulating valve, Le, a valve which acts to maintain a constant pressure, and a second pressure-regulating valve which is responsive to a much lower pressure is adapted to be connected to the circuit by means of a solenoid valve, which is operable by a limit switch or the like. While the barrel is being swaged, the pressure of the cushion of liquid under pressure is controlled by the first pressureregulating valve. When the shoulder on the mandrel enters the swaging zone between the hammers, a suitably offset stop, cam or the like acts on the limit switch, which then operates the solenoid valve to connect the second pressure-regulating valve to the circuit so that the latter valve now controls the pressure of the cushion of liquid under pressure. This pressure of the cushion is thus reduced and the piston which axially supports the workpiece can be pushed back opposite to the feeding direction under the action of the flow of the material. A comparatively simple hydraulic device is thus provided, which enables an automatic connection of the second valve into the circuit, provided that the stop, cam or the like for the limit switch is positioned as may be required.

To provide this simple design, the piston for axially supporting the workpiece is non-rotatably and axially slidably mounted in a sleeve, which defines the cylinder chamber for the cushion of liquid under pressure and which is rotatably and axially undisplaceably mounted in the gripping head.

An embodiment of the invention is shown by way of example on the accompanying drawings, in which FIG. 1 is a diagrammatic view, partly in section, showing an entire machine, and

FIGS. 2 to 4 are similar views showing the essential parts of the machine in three different operating position's.

Swaging dies 1 together with means, not shown, for driving them and means for varying the stroke position of the dies are mounted in a swaging box 2, which is preceded by a bed 3 for a displaceable gripping head 4. Rods 5 extend through the swaging box 2 and engage the gripping head 4. The rods 5 are connected to pistons 6, which are slidable in cylinders 7 secured to the swaging box 2. Through conduits 8, liquid under pressure delivered by a pump 9 is supplied to the pistons 6 so that the gripping head 4 is advanced toward the dies 1. A sleeve 10 is rotatably and axially nondisplaceably mounted in the gripping head 4 and is driven by a motor 11. A piston 12 which serves to directly axially support a workpiece 13 is nonrotatably and axially slidably mounted in the sleeve. A cushion 14 of liquid under pressure is contained in that cylinder chamber which is remote from the workpiece 13. The cushion is supplied by a pump 15, which is connected by a conduit 16 to the respective cylinder chamber. The conduit 16 extends from the pump 15 through a check valve 17 and is provided with a pressure-regulating valve 18. A solenoid valve 19 is operable by a limit switch, not shown, to connect a second pressureregulating valve 20 to the circuit. This second valve is set to a much lower pressure than the pressureregulating valve 18.

A yoke 21 is disposed between the two cylinders 7 and has another cylinder 22 secured to it. A rotatable holder-up 24 is axially supported by a piston 23 mounted in the cylinder 22. Pressure is applied to one end of the piston 23 by a pump 25. A pressureregulating valve 26 controls the backpressure of the liquid, which is displaced from the cylinder 22 during the movement of the holder-up. The workpiece 13 consists, e.g., of a barrel of a firearm and is axially gripped between the piston 12 of the gripping head 4 and the holder-up 24. As the workpiece is advanced by the pistons 6, the holder-up 24 and piston 23 are forced back and the liquid under pressure is forced back through the valve 26 into the oil reservoir (FIGS. 1 and 2). A rod 27 extends through the gripping head and the gripping head sleeve as well as the piston 12. A mandrel 28 is secured to the rod 27 and adapted to be retracted by an actuator 29. While the barrel and its grooves are being swaged, a portion 28' of the mandrel 28 is disposed between the dies 1 (FIG. 1). At the end of the barrel, the right-hand end of the mandrel engages an internal shoulder of the gripping head sleeve 10 so that the mandrel 28 together with the gripping head 4 is carried along toward the dies against the action of the hydraulic pressure in the actuator 29 (FIG. 2). When the mandrel step 28" has reached the swaging zone between the dies '1, the solenoid valve 19 is operated to connect the pressure-regulating valve 20 to the circuit so that the pressure of the cushion 14 of liquid under pressure is reduced and the material of the workpiece can flow toward the gripping head 4 and can force back the piston 12 (FlGS. 3 and 4). When the swaging has been completed, the

actuator

22, 23 for the holder-up returns the entire apparatus back to its initial position and the finished workpiece is removed.

What is claimed is:

1. A swaging machine for the internal profiling of a tubular workpiece, which comprises mandrel means formed with a shoulder and adapted to enter said workpiece so that the latter surrounds said shoulder,

a plurality of dies spaced around said mandrel means and operable to swage said workpiece onto said mandrel means,

a gripping head surrounding said mandrel means and adapted to axially support said workpiece at one end thereof and operable to rotate said workpiece about its axis and to advance it toward said dies at the same time,

a holder-up adapted to axially support said workpiece at the-opposite end thereof and movable in the axial direction of said workpiece, and means for applying a hydraulic backpressure to said holder-up so that the same yieldably resists the movement of said workpiece as the same is advanced by said gripping head,

said gripping head comprising means defining a chamber adapted to contain a cushion of liquid under pressure, which cushion is adapted to axially support said workpiece, and a piston interposed between said cushion and said workpiece and surrounding said mandrel;

said machine also comprising valve means operable to reduce the pressure of said cushion when said shoulder enters between said dies.

2. A swaging machine as set forth in claim 1, in which said gripping head is adapted to axially support said mandrel means adjacent to said one end of said workpiece and operable to advance said mandrel means toward said dies.

3. A swaging machine as set forth in claim 1, which is operable to form an internal profile in a tubular workpiece so as to produce a firearm barrel.

4. A swaging machine as set forth in claim 1, in which said mandrel means extend through said gripping head and comprise a mandrel formed with said shoulder and protruding from said gripping head toward said holderup and a mandrel rod connected to said mandrel at the end thereof remote from said holder-up.

5. A swaging machine as set forth in claim 1, which comprises a hydraulic circuit for controlling the pressure of said cushion,

said valve means being adapted to be connected to said hydraulic circuit.

6. A swaging machine as set forth in claim 5, in which said hydraulic circuit comprises a pump, a conduit connecting said pump to said cushion, a check valve incorporated in said cushion, and a first pressure-regulating valve connected to said conduit between said check valve and said cushion, and said valve means comprise a second pressure-regulating valve set to a much lower pressure than said first regulating valve and a connecting valve operable to connect said second regulating valve to said conduit between said check valve and said cushion.

7. A swaging machine as set forth in claim 6, in which said connecting valve consists of a solenoid valve and a limit switch is provided, which is operable thus to operate said solenoid valve when said mandrel means have reached a predetermined position relative to said dies.

8. A swaging machine as set forth in claim 1, in which said gripping head comprises a gripping head body which is movable toward said dies,

said means defining said chamber comprise a sleeve,

which is rotatably and axially nondisplaceably mounted in said gripping head body, and

said piston is nonrotatably and axially slidably mounted in said chamber.

k k I I.

Claims

1. A swaging machine for the internal profiling of a tubular workpiece, which comprises mandrel means formed with a shoulder and adapted to enter said workpiece so that the latter surrounds said shoulder, a plurality of dies spaced around said mandrel means and operable to swage said workpiece onto said mandrel means, a gripping head surrounding said mandrel means and adapted to axially support said workpiece at one end thereof and operable to rotate said workpiece about its axis and to advance it toward said dies at the same time, a holder-up adapted to axially support said workpiece at the opposite end thereof and movable in the axial direction of said workpiece, and means for applying a hydraulic backpressure to said holder-up so that the same yieldably resists the movement of said workpiece as the same is advanced by said gripping head, said gripping head comprising means defining a chaMber adapted to contain a cushion of liquid under pressure, which cushion is adapted to axially support said workpiece, and a piston interposed between said cushion and said workpiece and surrounding said mandrel; said machine also comprising valve means operable to reduce the pressure of said cushion when said shoulder enters between said dies.

4. A swaging machine as set forth in claim 1, in which said mandrel means extend through said gripping head and comprise a mandrel formed with said shoulder and protruding from said gripping head toward said holder-up and a mandrel rod connected to said mandrel at the end thereof remote from said holder-up.

5. A swaging machine as set forth in claim 1, which comprises a hydraulic circuit for controlling the pressure of said cushion, said valve means being adapted to be connected to said hydraulic circuit.

8. A swaging machine as set forth in claim 1, in which said gripping head comprises a gripping head body which is movable toward said dies, said means defining said chamber comprise a sleeve, which is rotatably and axially nondisplaceably mounted in said gripping head body, and said piston is nonrotatably and axially slidably mounted in said chamber.