Title:
Swaging machine
United States Patent 3893321
Abstract:
The machine serves to manufacture a tubular workpiece having an elongated, internally cylindrical, intermediate workpiece portion and two opposite workpiece end portions differing in inside diameter from said intermediate workpiece portion. The machine comprises die means defining a swaging zone and operable to swage a tubular workpiece in said swaging zone, and a feeding head and a holder-up, which are spaced apart and adapted to engage opposite ends of said tubular workpiece and to grip the same. The feeding head is operable to advance a workpiece thus gripped in its longitudinal direction through said swaging zone. Said holder-up is adapted to yield to the workpiece as it is thus advanced. A mandrel rod extends through said feeding head and carries a mandrel, which is adapted to extend in said workpiece in the longitudinal direction thereof and has opposite mandrel end portions which have outside surfaces conforming to the inside surfaces of respective ones of said workpiece end portions. The mandrel has also a cylindrical intermediate mandrel portion, which has an outside diameter that is equal to the inside diameter of said intermediate workpiece portion and has a length which is larger than the corresponding dimension of said swaging zone and substantially smaller than the length of said intermediate workpiece portion. Control means are provided which when said mandrel extends in said workpiece serve to couple said mandrel rod to said feeding head, so that said mandrel advances in unison with said workpiece, when a workpiece portion intended to form one of said workpiece end portions extends in said swaging zone, to hold said mandrel rod and mandrel in a fixed position when a workpiece portion intended to form said intermediate workpiece portion extends in said swaging zone, and in response to the displacement of said holder-up as it yields to the advancing workpiece to couple said mandrel rod to said feeding head, so that said mandrel advances in unison with said workpiece, when a workpiece portion intended to form the other of said workpiece end portions extends in said swaging zone.
US Patent References:
Tube swaging machine and method
Muller - August 1931 - 1819376
Apparatus for making tubular metal articles
Blair - October 1936 - 2058556
Apparatus for forming varying shaped bores in hollow members
Braatz - February 1964 - 3120137
Forging machine for the internal profiling of tubular workpieces, particularly of barrels for firearms
Kralowetz - April 1965 - 3177688
SWAGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES
Kralowetz - August 1973 - 3753365
Tube swaging machine and method
Muller - August 1931 - 1819376
Apparatus for making tubular metal articles
Blair - October 1936 - 2058556
Apparatus for forming varying shaped bores in hollow members
Braatz - February 1964 - 3120137
Forging machine for the internal profiling of tubular workpieces, particularly of barrels for firearms
Kralowetz - April 1965 - 3177688
SWAGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES
Kralowetz - August 1973 - 3753365
Application Number:
05/516009
Publication Date:
07/08/1975
Filing Date:
10/18/1974
View Patent Images:
Export Citation:
Assignee:
Gfm, Gesellschaft Fur Fertigungstechnik Und Maschinenbau (Steyr, OE)
Primary Class:
Other Classes:
42/78
International Classes:
B21J7/14; B21J13/08; B21J7/00; B21J13/00; B21K21/08
Field of Search:
72/76,370,402 29/1.1,1.11
Primary Examiner:
Larson, Lowell A.
Attorney, Agent or Firm:
Kelman, Kurt
Claims:
What is claimed is
1. A swaging machine for manufacturing a tubular workpiece having an elongated, internally cylindrical, intermediate workpiece portion and opposite workpiece end portions differing in inside diameter from said intermediate workpiece portion, said machine comprising
2. A swaging machine as set forth in claim 1, which comprises a stop which is axially engageable by said mandrel rod and adapted to be coupled to and disconnected from said feeding head under control of said control means.
3. A swaging machine as set forth in claim 2, in which said control means comprise
4. A swaging machine as set forth in claim 3, in which
5. A swaging machine as set forth in claim 4, in which
6. A swaging machine as set forth in claim 1, in which said control means comprise
7. A swaging machine as set forth in claim 1, in which
1. A swaging machine for manufacturing a tubular workpiece having an elongated, internally cylindrical, intermediate workpiece portion and opposite workpiece end portions differing in inside diameter from said intermediate workpiece portion, said machine comprising
2. A swaging machine as set forth in claim 1, which comprises a stop which is axially engageable by said mandrel rod and adapted to be coupled to and disconnected from said feeding head under control of said control means.
3. A swaging machine as set forth in claim 2, in which said control means comprise
4. A swaging machine as set forth in claim 3, in which
5. A swaging machine as set forth in claim 4, in which
6. A swaging machine as set forth in claim 1, in which said control means comprise
7. A swaging machine as set forth in claim 1, in which
Description:
This invention relates to a swaging machine, particularly for use in the manufacture of shotgun barrels, which are formed with an enlarged cylindrical portion or chamber portion at the rear end of the barrel, also with a cylindrical intermediate portion or barrel proper, and with a conically constricted portion or choke adjacent to the muzzle, which machine comprises a feeding head and a holder-up for gripping the workpiece, a stepped mandrel for shaping the inside surface of the barrel, and a mandrel rod, which extends through the feeding head and carries the mandrel and is adapted to be loaded by a piston, which is hydraulically operable to hold the mandrel in a fixed position between the tools whereas the mandrel is adapted to overcome the loading of said piston and to be moved through between the tools as the workpiece is advanced.
The swaging of shotgun barrels involves some difficulties, which are mainly due to the specific shape of such barrels. Shotgun barrels have a chamber portion at the rear end of the barrel, like other firearm barrels, and also have a so-called choke, which is a constricted portion near the muzzle and serves to prevent an excessive scattering of the shot as it leaves the barrel. It will be understood that these difficulties do not arise only in the manufacture of shotgun barrels but also in the manufacture of other tubular workpieces having a similar inside surface. So far, shotgun barrels or similar workpieces are swaged on a mandrel, which exactly conforms to the inside surface of the workpiece. During the swaging operation, the mandrel is moved through together with the workpiece between the dies so that the tubular workpiece which is initially smooth is shaped to have an inside surface conforming to the mandrel. In most cases the swaging operation proceeds from the chamber portion to the choke. This swaging process has the disadvantage that the mandrel has a large length, which is equal to the overall length of the barrel inclusive of the chamber portion and choke. The costs of manufacturing such mandrel are very high because a high precision is required. Eccentricities of the mandrel are permissible only within very small tolerance ranges because otherwise the resulting shotgun barrel does not have the desired quality. This results in a high rate of rejects. Besides, the mandrels have only a short life, particularly when the shotgun barrels are cold-swaged. For this reason, swaging with the aid of a long mandrel is not economical.
To avoid these disadvantages, swaging machines have been provided in which a short mandrel can be used. That mandrel conforms only to the chamber portion and a portion of the barrel proper. In these machines, the barrel proper is swaged first while that portion of the mandrel which corresponds to the barrel proper remains in a fixed position between the dies. Thereafter, the chamber portion is swaged while the mandrel is moved in unison with the workpiece. For this purpose, the mandrel rod is hydraulically loaded in such a manner that it is not advanced initially in spite of the feeding of the workpiece. A stop is fixed to the feeding head and after a predetermined advance of the feeding head engages a mating surface of the mandrel rod. This stop assists in overcoming the hydraulic loading so that the mandrel is now forced through between the dies at the feeding speed of the workpiece. Owing to its short length, this mandrel can be manufactured at much lower cost and because it can be made from cermets it has a long life. On the other hand, that swaging process has the disadvantage that only the barrel proper and the chamber portion can be swaged in one operation, which must be succeeded by a second operation for shaping the choke.
It is an object of the invention to eliminate these disadvantages and to provide a swaging machine which is of the kind described first hereinbefore and which enables with the aid of a short mandrel the swaging of shotgun barrels or similar tubular workpieces in a single operation.
This object is accomplished according to the invention in that the mandrel has in known manner a shape conforming to the inside surface of the shotgun barrel but that mandrel portion which corresponds to the barrel proper has only a length which is approximately as large as the length of the swaging zone, and that the mandrel rod is adapted to be coupled to the feeding head to move with it in the feeding direction in dependence on the displacement of the holder-up during the swaging operation. Because the intermediate mandrel portion has not the same length as the barrel proper but has only the length which is required for the swaging operation, it must be held in a fixed position between the dies during the shaping of the intermediate portion of the barrel. During the swaging operation, for this reason, the mandrel must first be pushed through together with the workpiece between the dies until the first portion has been swaged, then the mandrel must be held in a fixed position until the barrel proper has been swaged, and the mandrel must then be moved together with the workpiece until the shot barrel has been completed. In most cases, the swaging begins at the muzzle and the choke is swaged first, while the mandrel is moving, then the barrel proper is swaged with the mandrel fixed in position, and thereafter the chamber portion is swaged with the mandrel moving. To swage the barrel proper exactly in the desired length and to make an exact allowance for the stretching of the material, it is a feature of the invention that the mandrel movement is controlled in dependence on the displacement of the holder-up. In this way, the length of the barrel and of each portion thereof can be determined with the desired accuracy because the length of the previously swaged barrel portion will determine the time at which a new phase of the swaging operation begins. This is of special significance for the barrel proper, which should have exactly a predetermined length with very small tolerances. As soon as the barrel proper has been swaged in the prescribed length, the mandrel rod is automatically coupled to the feeding head so that the mandrel which was in position of rest is advanced at the feeding speed and the swaging of the chamber portion begins. In the swaging machine according to the invention, the mandrel movement and the beginning of a step of the swaging sequence depend on the previously swaged portion of the workpiece because in dependence on the position of the holder-up the mandrel rod is coupled to the feeding head and the mandrel is moved in the feeding direction at the same speed as the feeding head, or the mandrel rod is not connected to the feeding head and the mandrel is held in a fixed position by the hydraulic pressure which acts on the mandrel rod via a piston. This control of the mandrel by the holder-up permits of the use of a mandrel having a short intermediate portion, which conforms to the barrel proper. For this reason the mandrel can be manufactured at reasonably low cost. Besides, the mandrel according to the invention may be of cermets so that it has a long life.
The mandrel rods in swaging machines are usually stop-controlled. It is now necessary to control the mandrel movement in dependence on the previously swaged portion. To accomplish this in a simple manner it is a feature of the invention that a stop is provided which is engageable by the mandrel rod and is displaceable relative to the feeding head and can be coupled to the latter by a limit switch or the like which is actuable by the holder-up. As soon as the holder-up has been displaced a predetermined distance in the feeding direction, the limit switch is operated so that the stop is coupled to the feeding head and then acts immediately on the engaging surface of the mandrel rod because said engaging face has engaged the stop some time before the critical instance. The stop now forces the mandrel rod forwardly at the speed of the feeding head so that the workpiece and mandrel move through perfectly in unison between the dies and the desired step of the swaging sequence begins exactly at the desired point.
According to a preferred feature of the invention the stop consists of a hydraulically loaded piston, which is slidable in a cylinder that is fixed to the feeding head and is connected to an inlet and outlet conduit, which is adapted to be shut off by a solenoid valve or the like, which is operable by the limit switch or the like. As soon as the feeding head has advanced relative to the non-moving mandrel rod to such an extent that the engaging surface of the mandrel rod engages the piston -- this must reliably be effected before the holder-up actuates the limit switch -- said engaging surface forces back the piston in the cylinder until the holder-up has reached the limit switch. Before that time, the inlet and outlet conduit is open so that the piston can displace the hydraulic fluid in the cylinder. When the holder-up has actuated the limit switch, the solenoid valve shuts off the discharge of the hydraulic fluid so that the fluid forms immediately a hard pad, which cannot be displaced or compressed by the piston. The advance of the feeding head is now transmitted by this fluid pad and the piston to the mandrel rod, which is now moved through together with the workpiece between the swaging dies at the feeding speed and in doing so overcomes the hydraulic pressure which tends to hold the mandrel rod in its position of rest. As soon as the holder-up has actuated the limit switch, the mandrel advances and the next step of the swaging sequence begins. For this reason it is possible, e.g., to swage the chamber portion when the barrel proper has been swaged exactly in a predetermined length.
An embodiment of the invention is shown diagrammatically and by way of example on the accompanying drawings, in which
FIG. 1 is a partly sectional view showing a swaging machine according to the invention and
FIGS. 2 to 5 illustrate the swaging of a shotgun barrel comprising a choke and a chamber portion in four steps.
The swaging machine according to the invention comprises essentially a swaging box 1, dies 2, which are mounted in the swaging box, a feeding head 4, which is slidably guided on a suitable bed 3, and a holder-up 5, for gripping the workpiece, and a stepped mandrel 6 for shaping the inside surface of the shotgun barrel. The mandrel 6 is carried by a mandrel rod 7, which extends through the feeding head and at its free end forms a piston 8, which is slidable in a cylinder 9. The cylinder 9 is slidable in a stationary cylinder 10, which is connected to a constantly pressurized hydraulic conduit 11. The displacement of the cylinder 9 in the cylinder 10 is limited by stops. Hydraulic pressure can be selectively applied through conduit 12 to the piston 8, which is formed by the mandrel rod. Because the piston 8 has end faces of different sizes, the piston 8 and the mandrel rod 7 can be reciprocated in spite of the continuous application of pressure through conduit 11. A cylinder 13 is mounted on the feeding head 4, and a piston 14 is slidable in the cylinder 13 and serves as a stop for an engaging surface 15 provided on the mandrel rod 7. A solenoid valve 17 is incorporated in the conduit 16 connected to the cylinder 13 and either shuts off the conduit 16 or connects it to the supply conduit 16' or the discharge conduit 16". The solenoid valve 17 is controlled by a limit switch 18, which is actuable by the holder-up 5. The feeding head 4 is displaceable by the tie rods 19 in the feeding direction and opposite thereto and as means for engaging the workpiece comprises a piston 20, which is non-rotatably mounted in a sleeve 22. The latter is rotatably and non-displaceably mounted in the feeding head and adapted to be driven by a worm gearing 21. The sleeve 22 defines with the piston 20 a cylinder chamber 23, which is filled with liquid under pressure. This liquid under pressure forms a pad, which applies to the piston 20 a pressure which can be adjusted by a valve, not shown, and is selected so that material can flow toward the feeding head during the swaging of a shoulder. A neat, continuous internal shoulder can be swaged only when the pressure applied to the workpiece at its feeding head end is reduced during the swaging of the shoulder so that material can flow opposite to the feeding direction and a disengagement of the workpiece is thus prevented.
The mandrel 6 used in the swaging of a shotgun barrel has a shape which substantially conforms to the inside surface of the shotgun barrel. The mandrel has a portion 6' conforming to the choke, a portion 6" conforming to the barrel proper, and a portion 6" conforming to the chamber portion. The intermediate portion 6" is not as long as the barrel proper but is only approximately as long as the actual swaging zone. The entire swaging operation performed with the aid of the mandrel according to the invention will now be described:
The workpiece is first gripped between the feeding head 4 and the holder-up 5. For this purpose the holder-up is moved to a position between the dies 2. Hydraulic pressure is then applied through conduit 12 to the piston 8 of the mandrel rod 7, and the mandrel 6 is introduced into the workpiece until the mandrel engages the holder-up 5 (FIG. 2). Then the swaging operation begins. The feeding head 4 performs its feeding movement to move the workpiece together with the mandrel through between the dies and to force back the holder-up 5. As soon as the first portion 6' of the mandrel has moved through between the dies 1 and the choke has thus been swaged, the piston 8 engages the feeding head end of the cylinder 9 to stop the advance of the mandrel because the hydraulic pressure applied through conduit 11 into the cylinder 10 prevents a further movement of the cylinder 9. The cylindrical intermediate portion 6" of the mandrel is now disposed between the dies 2 and as the feeding of the workpiece is continued the barrel proper is swaged next to the choke (FIG. 3). When the workpiece has been fed so that the holder-up 5 has reached the limit switch 18, which is arranged at a distance corresponding to the desired length of the barrel proper (FIG. 4), the limit switch is actuated by the holder-up so that the solenoid valve 17 shuts off the conduit 16 connected to the cylinder 13. Before the holder-up can actuate the limit switch, the feeding head 4 has been displaced relative to the stationary mandrel rod 7 to such an extent that the engaging surface 15 of the mandrel rod 7 has engaged the piston 14 and has forced back the latter as long as the conduit 16 is open. Because the conduit 16 is connected by the valve 17 to the discharge conduit 16", the liquid can be displaced out of the cylinder 13 and does not impede the movement of the piston. When the holder-up 5 has actuated the limit switch 18 so that the solenoid valve 17 shuts off the conduit 16, a pad of liquid under pressure will form in the cylinder 13 and will prevent a further rearward movement of the piston 14. As a result, the piston 14 is compelled to follow the feeding movement of the feeding head and transmits this movement to the mandrel rod 7. The piston 8 formed by the mandrel rod 7 engages the feeding head end of the cylinder 9 and the force which is exerted by the feeding head 4 through the liquid pad and the piston 14 to the engaging surface 15 and the mandrel rod 7 is sufficient to advance the cylinder 9 against the hydraulic pressure in the cylinder 10 and to displace the hydraulic fluid from the cylinder 10 through conduit 11. The mandrel rod 7 is thus moved again at the feeding speed and forces the mandrel 6 through between the dies 2 so that the third position 6"' of the mandrel now enters the swaging zone and the chamber portion of the shotgun barrel is swaged (FIG. 5). The shotgun barrel has now been completely swaged and by means of the holder-up and the feeding head is returned to its initial position. The piston 8 is then hydraulically operated to withdraw the mandrel from the barrel. The workpiece consisting of the complete barrel is withdrawn from the machine and the machine is prepared for a new swaging sequence. The swaging machine according to the invention permits of manufacturing a shotgun barrel in one operation and with the aid of a short mandrel. Because the movement of the mandrel rod and the several steps of the swaging sequence are controlled in dependence on the displacement of the holder-up, the portions of the shotgun barrel, i.e., the choke, the barrel proper and the chamber portion, can be swaged in the required lengths to the desired accuracy.
The swaging of shotgun barrels involves some difficulties, which are mainly due to the specific shape of such barrels. Shotgun barrels have a chamber portion at the rear end of the barrel, like other firearm barrels, and also have a so-called choke, which is a constricted portion near the muzzle and serves to prevent an excessive scattering of the shot as it leaves the barrel. It will be understood that these difficulties do not arise only in the manufacture of shotgun barrels but also in the manufacture of other tubular workpieces having a similar inside surface. So far, shotgun barrels or similar workpieces are swaged on a mandrel, which exactly conforms to the inside surface of the workpiece. During the swaging operation, the mandrel is moved through together with the workpiece between the dies so that the tubular workpiece which is initially smooth is shaped to have an inside surface conforming to the mandrel. In most cases the swaging operation proceeds from the chamber portion to the choke. This swaging process has the disadvantage that the mandrel has a large length, which is equal to the overall length of the barrel inclusive of the chamber portion and choke. The costs of manufacturing such mandrel are very high because a high precision is required. Eccentricities of the mandrel are permissible only within very small tolerance ranges because otherwise the resulting shotgun barrel does not have the desired quality. This results in a high rate of rejects. Besides, the mandrels have only a short life, particularly when the shotgun barrels are cold-swaged. For this reason, swaging with the aid of a long mandrel is not economical.
To avoid these disadvantages, swaging machines have been provided in which a short mandrel can be used. That mandrel conforms only to the chamber portion and a portion of the barrel proper. In these machines, the barrel proper is swaged first while that portion of the mandrel which corresponds to the barrel proper remains in a fixed position between the dies. Thereafter, the chamber portion is swaged while the mandrel is moved in unison with the workpiece. For this purpose, the mandrel rod is hydraulically loaded in such a manner that it is not advanced initially in spite of the feeding of the workpiece. A stop is fixed to the feeding head and after a predetermined advance of the feeding head engages a mating surface of the mandrel rod. This stop assists in overcoming the hydraulic loading so that the mandrel is now forced through between the dies at the feeding speed of the workpiece. Owing to its short length, this mandrel can be manufactured at much lower cost and because it can be made from cermets it has a long life. On the other hand, that swaging process has the disadvantage that only the barrel proper and the chamber portion can be swaged in one operation, which must be succeeded by a second operation for shaping the choke.
It is an object of the invention to eliminate these disadvantages and to provide a swaging machine which is of the kind described first hereinbefore and which enables with the aid of a short mandrel the swaging of shotgun barrels or similar tubular workpieces in a single operation.
This object is accomplished according to the invention in that the mandrel has in known manner a shape conforming to the inside surface of the shotgun barrel but that mandrel portion which corresponds to the barrel proper has only a length which is approximately as large as the length of the swaging zone, and that the mandrel rod is adapted to be coupled to the feeding head to move with it in the feeding direction in dependence on the displacement of the holder-up during the swaging operation. Because the intermediate mandrel portion has not the same length as the barrel proper but has only the length which is required for the swaging operation, it must be held in a fixed position between the dies during the shaping of the intermediate portion of the barrel. During the swaging operation, for this reason, the mandrel must first be pushed through together with the workpiece between the dies until the first portion has been swaged, then the mandrel must be held in a fixed position until the barrel proper has been swaged, and the mandrel must then be moved together with the workpiece until the shot barrel has been completed. In most cases, the swaging begins at the muzzle and the choke is swaged first, while the mandrel is moving, then the barrel proper is swaged with the mandrel fixed in position, and thereafter the chamber portion is swaged with the mandrel moving. To swage the barrel proper exactly in the desired length and to make an exact allowance for the stretching of the material, it is a feature of the invention that the mandrel movement is controlled in dependence on the displacement of the holder-up. In this way, the length of the barrel and of each portion thereof can be determined with the desired accuracy because the length of the previously swaged barrel portion will determine the time at which a new phase of the swaging operation begins. This is of special significance for the barrel proper, which should have exactly a predetermined length with very small tolerances. As soon as the barrel proper has been swaged in the prescribed length, the mandrel rod is automatically coupled to the feeding head so that the mandrel which was in position of rest is advanced at the feeding speed and the swaging of the chamber portion begins. In the swaging machine according to the invention, the mandrel movement and the beginning of a step of the swaging sequence depend on the previously swaged portion of the workpiece because in dependence on the position of the holder-up the mandrel rod is coupled to the feeding head and the mandrel is moved in the feeding direction at the same speed as the feeding head, or the mandrel rod is not connected to the feeding head and the mandrel is held in a fixed position by the hydraulic pressure which acts on the mandrel rod via a piston. This control of the mandrel by the holder-up permits of the use of a mandrel having a short intermediate portion, which conforms to the barrel proper. For this reason the mandrel can be manufactured at reasonably low cost. Besides, the mandrel according to the invention may be of cermets so that it has a long life.
The mandrel rods in swaging machines are usually stop-controlled. It is now necessary to control the mandrel movement in dependence on the previously swaged portion. To accomplish this in a simple manner it is a feature of the invention that a stop is provided which is engageable by the mandrel rod and is displaceable relative to the feeding head and can be coupled to the latter by a limit switch or the like which is actuable by the holder-up. As soon as the holder-up has been displaced a predetermined distance in the feeding direction, the limit switch is operated so that the stop is coupled to the feeding head and then acts immediately on the engaging surface of the mandrel rod because said engaging face has engaged the stop some time before the critical instance. The stop now forces the mandrel rod forwardly at the speed of the feeding head so that the workpiece and mandrel move through perfectly in unison between the dies and the desired step of the swaging sequence begins exactly at the desired point.
According to a preferred feature of the invention the stop consists of a hydraulically loaded piston, which is slidable in a cylinder that is fixed to the feeding head and is connected to an inlet and outlet conduit, which is adapted to be shut off by a solenoid valve or the like, which is operable by the limit switch or the like. As soon as the feeding head has advanced relative to the non-moving mandrel rod to such an extent that the engaging surface of the mandrel rod engages the piston -- this must reliably be effected before the holder-up actuates the limit switch -- said engaging surface forces back the piston in the cylinder until the holder-up has reached the limit switch. Before that time, the inlet and outlet conduit is open so that the piston can displace the hydraulic fluid in the cylinder. When the holder-up has actuated the limit switch, the solenoid valve shuts off the discharge of the hydraulic fluid so that the fluid forms immediately a hard pad, which cannot be displaced or compressed by the piston. The advance of the feeding head is now transmitted by this fluid pad and the piston to the mandrel rod, which is now moved through together with the workpiece between the swaging dies at the feeding speed and in doing so overcomes the hydraulic pressure which tends to hold the mandrel rod in its position of rest. As soon as the holder-up has actuated the limit switch, the mandrel advances and the next step of the swaging sequence begins. For this reason it is possible, e.g., to swage the chamber portion when the barrel proper has been swaged exactly in a predetermined length.
An embodiment of the invention is shown diagrammatically and by way of example on the accompanying drawings, in which
FIG. 1 is a partly sectional view showing a swaging machine according to the invention and
FIGS. 2 to 5 illustrate the swaging of a shotgun barrel comprising a choke and a chamber portion in four steps.
The swaging machine according to the invention comprises essentially a swaging box 1, dies 2, which are mounted in the swaging box, a feeding head 4, which is slidably guided on a suitable bed 3, and a holder-up 5, for gripping the workpiece, and a stepped mandrel 6 for shaping the inside surface of the shotgun barrel. The mandrel 6 is carried by a mandrel rod 7, which extends through the feeding head and at its free end forms a piston 8, which is slidable in a cylinder 9. The cylinder 9 is slidable in a stationary cylinder 10, which is connected to a constantly pressurized hydraulic conduit 11. The displacement of the cylinder 9 in the cylinder 10 is limited by stops. Hydraulic pressure can be selectively applied through conduit 12 to the piston 8, which is formed by the mandrel rod. Because the piston 8 has end faces of different sizes, the piston 8 and the mandrel rod 7 can be reciprocated in spite of the continuous application of pressure through conduit 11. A cylinder 13 is mounted on the feeding head 4, and a piston 14 is slidable in the cylinder 13 and serves as a stop for an engaging surface 15 provided on the mandrel rod 7. A solenoid valve 17 is incorporated in the conduit 16 connected to the cylinder 13 and either shuts off the conduit 16 or connects it to the supply conduit 16' or the discharge conduit 16". The solenoid valve 17 is controlled by a limit switch 18, which is actuable by the holder-up 5. The feeding head 4 is displaceable by the tie rods 19 in the feeding direction and opposite thereto and as means for engaging the workpiece comprises a piston 20, which is non-rotatably mounted in a sleeve 22. The latter is rotatably and non-displaceably mounted in the feeding head and adapted to be driven by a worm gearing 21. The sleeve 22 defines with the piston 20 a cylinder chamber 23, which is filled with liquid under pressure. This liquid under pressure forms a pad, which applies to the piston 20 a pressure which can be adjusted by a valve, not shown, and is selected so that material can flow toward the feeding head during the swaging of a shoulder. A neat, continuous internal shoulder can be swaged only when the pressure applied to the workpiece at its feeding head end is reduced during the swaging of the shoulder so that material can flow opposite to the feeding direction and a disengagement of the workpiece is thus prevented.
The mandrel 6 used in the swaging of a shotgun barrel has a shape which substantially conforms to the inside surface of the shotgun barrel. The mandrel has a portion 6' conforming to the choke, a portion 6" conforming to the barrel proper, and a portion 6" conforming to the chamber portion. The intermediate portion 6" is not as long as the barrel proper but is only approximately as long as the actual swaging zone. The entire swaging operation performed with the aid of the mandrel according to the invention will now be described:
The workpiece is first gripped between the feeding head 4 and the holder-up 5. For this purpose the holder-up is moved to a position between the dies 2. Hydraulic pressure is then applied through conduit 12 to the piston 8 of the mandrel rod 7, and the mandrel 6 is introduced into the workpiece until the mandrel engages the holder-up 5 (FIG. 2). Then the swaging operation begins. The feeding head 4 performs its feeding movement to move the workpiece together with the mandrel through between the dies and to force back the holder-up 5. As soon as the first portion 6' of the mandrel has moved through between the dies 1 and the choke has thus been swaged, the piston 8 engages the feeding head end of the cylinder 9 to stop the advance of the mandrel because the hydraulic pressure applied through conduit 11 into the cylinder 10 prevents a further movement of the cylinder 9. The cylindrical intermediate portion 6" of the mandrel is now disposed between the dies 2 and as the feeding of the workpiece is continued the barrel proper is swaged next to the choke (FIG. 3). When the workpiece has been fed so that the holder-up 5 has reached the limit switch 18, which is arranged at a distance corresponding to the desired length of the barrel proper (FIG. 4), the limit switch is actuated by the holder-up so that the solenoid valve 17 shuts off the conduit 16 connected to the cylinder 13. Before the holder-up can actuate the limit switch, the feeding head 4 has been displaced relative to the stationary mandrel rod 7 to such an extent that the engaging surface 15 of the mandrel rod 7 has engaged the piston 14 and has forced back the latter as long as the conduit 16 is open. Because the conduit 16 is connected by the valve 17 to the discharge conduit 16", the liquid can be displaced out of the cylinder 13 and does not impede the movement of the piston. When the holder-up 5 has actuated the limit switch 18 so that the solenoid valve 17 shuts off the conduit 16, a pad of liquid under pressure will form in the cylinder 13 and will prevent a further rearward movement of the piston 14. As a result, the piston 14 is compelled to follow the feeding movement of the feeding head and transmits this movement to the mandrel rod 7. The piston 8 formed by the mandrel rod 7 engages the feeding head end of the cylinder 9 and the force which is exerted by the feeding head 4 through the liquid pad and the piston 14 to the engaging surface 15 and the mandrel rod 7 is sufficient to advance the cylinder 9 against the hydraulic pressure in the cylinder 10 and to displace the hydraulic fluid from the cylinder 10 through conduit 11. The mandrel rod 7 is thus moved again at the feeding speed and forces the mandrel 6 through between the dies 2 so that the third position 6"' of the mandrel now enters the swaging zone and the chamber portion of the shotgun barrel is swaged (FIG. 5). The shotgun barrel has now been completely swaged and by means of the holder-up and the feeding head is returned to its initial position. The piston 8 is then hydraulically operated to withdraw the mandrel from the barrel. The workpiece consisting of the complete barrel is withdrawn from the machine and the machine is prepared for a new swaging sequence. The swaging machine according to the invention permits of manufacturing a shotgun barrel in one operation and with the aid of a short mandrel. Because the movement of the mandrel rod and the several steps of the swaging sequence are controlled in dependence on the displacement of the holder-up, the portions of the shotgun barrel, i.e., the choke, the barrel proper and the chamber portion, can be swaged in the required lengths to the desired accuracy.