Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/28—Deep-drawing of cylindrical articles using consecutive dies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/26—Making hollow objects characterised by the use of the objects cans or tins; Closing same in a permanent manner

Definitions

• This invention relates generally to a can body making apparatus and more particularly to a ram assembly and a redraw assembly thereof.
• a can body making apparatus is described in U.S. Patent No. 3,696,657 issued to J. H. Maytag, which is hereby incorporated herein by reference for all that it discloses.
• the ram carriage and redraw carriage are each mounted on rollers which move over carriage way strips. Each pair of upper and lower rollers are urged toward each other so as to be in firm contact with the carriage way strip located therebetween.
• Both the ram and redraw carriages are reciprocated at rates sufficient to form about two hundred cans a minute.
• the constant recip ⁇ rocal movement of the ram and redraw carriages and the tight engagement of the rollers on the carriage way strips result in wear which causes misalignment of the ram or of the can blanks by the redraw sleeve. It is understood that this misalignment is small, between about 0.005 and 0.010 of an inch, but such misalignment can result in defective cans.
• magnet assemblies to support a moveable shaft.
• Magnet assemblies for supporting a moveable shaft are described in the following U.S. Patents which are hereby specifically incorporated by reference for all that is disclosed therein: 4,912,343 of Stuart; 4,892,328 of Kurtz an et al.; 4,831,212 of Matsushita et al.; 4,827,169 of Habermann; 4,795,927 of Morii et al.; 4,642,500 of
• the present invention may comprise a can body making apparatus for forming can blanks into elongated can bodies comprising: a stationary support frame; a housing having forming and ironing dies located therein mounted on said support frame; an elongated ram having a first end portion and a second end portion, said first end portion having an outer surface adapted for movement into a redraw assembly to contact a can blank in said redraw assembly and to move said can blank out of said redraw assembly and through said forming and ironing dies to form an elongated can body; reciprocating drive means for providing reciprocating axial displacement for said elongated ram; and a redraw assembly located adjacent to said housing, wherein said redraw assembly comprises: a redraw sleeve for supporting a can body preform thereon; redraw carriage means for supporting and axially displacing said redraw sleeve relative said elongated ram; redraw electromagnetic coil means fixedly positioned relative said stationary support frame and having a central coil
• the present invention may also comprise, in a can body maker apparatus of the type having a stationary support frame, a ram assembly which is reciprocatingly displaceable relative the support frame and a redraw assembly which is reciprocatingly displaceable relative the support frame, a method of reciprocating the redraw assembly comprising the steps of: mounting a magnetic coil assembly having a central longitudinal axis in fixed relationship with said support frame; mounting a permanent magnet in fixed relationship with said redraw assembly; displacing said permanent magnet along said central longitudinal axis of said coil assembly by selective application of electrical current to said coil assembly.
• Fig. 1 is a partially cross sectional, top plan view of a can body maker apparatus.
• Fig. 2 is a side elevation view of the can body maker apparatus of Fig. 1.
• Fig. 3 is a perspective view of a ram magnetic bearing assembly.
• Fig. 4 is a schematic illustration of a control system for the ram and redraw assembly of the body maker apparatus of Fig. 1.
• Fig. 5 is a graph illustrating typical vertical and lateral forces exerted on a bearing assembly by a ram.
• Fig. 6 is a block diagram illustrating the operation of a portion of the control system of Fig. 4.
• Fig. 7 is a block diagram illustrating the operation of another portion of the control system of Fig. 4.
• Fig. 8 is a partially cross ⁇ sectional top plan view of an alternative embodiment of a can body maker redraw assembly which is provided in a can body maker of the type illustrated in Figs. 1 and 2.
• Fig. 9 is a cross-sectional top plan view of a redraw actuator unit of the alternative redraw assembly illustrated in Fig. 8.
• Fig. 10 is a block diagram illustrating one manner by which the position of a redraw carriage shaft is controlled based upon the position of a body maker ram.
• Fig. 11 is a block diagram illustrating an alternative control method to that indicated in Fig. 10.
• Fig. 1 illustrates a can body maker apparatus 10 of the type having an axially reciprocal ram member 30 and a coaxially aligned redraw assembly 408 which is reciprocally displaceable independently of the ram member 30.
• a ram position sensing assembly 50, 148, 150, 248, 250, Fig. 4 senses the position of the ram member and generates a ram position signal in response thereto.
• An electromagnetic bearing assembly 60 frictionlessly radially supports and aligns the ram member with a predetermined ram displacement path RR.
• a redraw carriage actuator 439 applies magnetic force to a redraw carriage 416 which produces the reciprocal motion of the redraw assembly.
• a control unit 130 generates data signals for selectively energizing and deenergizing electromagnets in the electromagnetic bearing assembly 60 and the redraw carriage actuator 439 in response to the ram position signal.
• can body maker 10 comprises a support frame 12 comprising a pair of spaced apart linearly extending support beams 16 in parallel relationship and having support legs (not shown) fixedly mounted on a floating support base 14 as is conventional in the art.
• a plurality of cross-beam members 18 extend between and are connected to the support beams 16 to provide a rigid support structure.
• a housing 20 having conventional can forming and ironing dies located therein is fixedly mounted on the support beams 16 by suitable means such as nuts and bolts.
• An elongated ram 30 is provided and has a main body portion 32 having a generally cylindrical outer peripheral surface 34 and which is constructed from a magnetic material such as steel.
• the elongated ram 32 has a first end portion 36 for movement into a redraw assembly to contact a can blank (not shown) located therein and to move the can blank through conventional can forming and ironing dies (not shown) in the housing 20 to form an elongated can body (not shown) .
• the elongated ram 30 has a second end portion 38 which is securely mounted in a connecting device 40.
• Apparatus 42 extends from machinery, such as the straight line motion assembly described in detail in the above referenced Maytag and Grims et al. patents, which provides the apparatus 42 with a reciprocating linear motion.
• a connecting arm 44 is connected to the apparatus 42 and the connecting device 40 to transmit the reciprocating linear motion to the connecting device 40 and the elongated ram 30.
• Apparatus 42 receives motive force from a crankshaft 46, Fig. 4, which is connected by conventional mechanical linkage to an electric drive motor 48.
• An electronic encoder unit 50 is mounted on the crankshaft 46 and generates a pulse signal which is representative of crankshaft angular position. In one preferred embodiment an encoder is selected which generates 10,000 pulses per crankshaft revolution.
• the encoder may be either an incremental, absolute, or linear position indicator type as are commercially available in the industry.
• the encoder pulse signal is provided to a data processing device having a pulse counter which resets at the beginning of each new crankshaft revolution. The ram performs one ram stroke per crankshaft revolution. The encoder pulse count is thus representative of ram axial position.
• a magnetic bearing assembly 60 is mounted in a support structure 62 which is mounted on the support beams 16 so as to hold the magnetic bearing assembly 60 at a fixed location.
• the magnetic bearing assembly 60 described in more detail below, has a generally cylindrical inner surface 64, Fig. 3, having a diameter slightly greater than the diameter of the generally cylindrical outer surface 34 to provide for sliding movement of the ram main body portion 32 through the magnetic bearing assembly.
• the difference in diameters between the generally cylindrical outer surface 34 and the generally cylindrical inner surface 64 is between about 0.005 and 0.015 inches.
• the elongated ram 30 during the reciprocation thereof is frictionlessly supported solely by the magnetic force provided by the magnetic bearing assembly 60.
• the magnetic bearing support housing 62 is illustrated in Figs. 1 and 3.
• the support housing 62 comprises an integral casting preferably formed from nonmagnetic material such as cast aluminum and has a pair of linearly extending beams 66 each having a generally planar bottom surface. Beams 66 abut and are attached to beams 16 of support frame 12. A plurality of reinforcing ribs 68 extend between and are integral with beams 66.
• An interior wall 70 of support housing 62 comprises a plurality of flange portions 72, etc., projecting therefrom which are adapted to be fixedly secured, as by attachment bolts, to various portions of the bear .ng assembly 60.
• Magnetic bearing assembly 60 for frictionlessly supporting ram 30 main body portion 32 is illustrated in Fig: 3.
• the magnetic bearing assembly includes an elongated cylindrical sleeve 118 which comprises inner surface 64.
• a forward and a rear magnetic bearing, 102, 202 are provided by two sets of U-shaped stationary electromagnets 110, 112, 114, 116 and 210, 220, 224, 226 and position sensors 148, 150, and 248, 250 respectively are located at each end of sleeve 118 which may be 15 inches long.
• Each set of electromagnets preferably consists of four electromagnets, e.g. 110, 112, 114, 116, located 90 degrees apart around the periphery of the sleeve 118 and are operable to generate four orthogonal magnetic fields 130 within the sleeve 118.
• Each set of positions sensors e.g. 148, 150, are aligned with associated electromagnets, e.g. 110, 112, to define two orthogonal horizontal X j X 1f X 2 2 and vertical Y- j Ya, Y 2 Y 2 axes from which signals proportional to orthogonal ram shaft displacement are provided.
• These signals are provided to a data processing unit 130, Fig. 4, which also receives the pulse signal from encoder 50.
• the data processing unit 130 issues control signals to control circuits 142, 144, 144, 146, Fig.
• electromagnets which controls the current flow from electric energy source 150 to each opposed set of electromagnets so as to energize the coil windings 132, 134, 136, 138 and 232, 234, 236, 238 for radially centering the elongated ram 30 within the sleeve 118.
• the electromagnets may be energized either in a linear fashion or in a pulsed manner as is well known in the art. In the preferred embodiment, pulsed energization is employed.
• the data processing unit 130 generates control signals based solely on ram radial position as sensed by sensors 148, 150 248, 250.
• the data processing unit in this embodiment may comprise hard wired electronic components identical to those described in U.S. Patent 4,473,259 of Goldowsky.
• data processing unit 130 generates control signals based upon both ram radial position as sensed by sensors 148, 150 248, 250 and is also based upon ram axial position as indicated by encoder 50.
• encoder signal 300 comprises a set of signal pulses 302, 304, etc., which are indicative of the exact axial position of the ram 30 at any point in time.
• Fig. 5 also shows a force signal 310 which is typical of the total vertical force applied to a magnetic bearing e.g. 202 during a ram operating stroke. Forces which contribute to this total vertical force include a sinusoidal force applied by the ram drive apparatus 42 due to the fact that the linear motion assembly always has a small component of nonlinear force on apparatus 42. This force and also the force attributable to the weight of the ram 30 itself vary in magnitude during the ram stroke due to the changing length of the moment arm associated with each of these forces during a ram stroke.
• these components of the total vertical force exerted on the magnetic bearing are cyclical and under normal operating conditions represent substantially all of the vertical force which will be exerted on the magnetic bearing.
• This force may be empirically determined using conventional strain gages and/or other means and may be stored as a function of ram axial position in a conventional electronic storage medium such as the RAM of a conventional microcomputer which may comprise a portion of the data processing unit 50.
• Fig. 5 further illustrates at 350 the total lateral side loading force which may typically be exerted on electromagnet bearing 202 by ram 30.
• the short interval large magnitude force indicated at 352 is primarily due to a side force experienced at the end of ram 30 as it moves through the can forming dies.
• This relatively large magnitude force is cyclical and, like the cyclical vertical force, may also be empirically determined and stored as a function of ram axial position.
• the data processing means which may comprise a conventional microprocessor, at predetermined intervals, e.g. every 5 milliseconds, reads the encoder count and applies a predetermined algorithm thereto based upon the empirically determined force relationship e.g. 310 in order to determine the force to be applied and then provides a control signal to the control circuitry for the associated opposed pairs of magnets e.g.
• the data processing unit 130 may also determine a second (secondary) force signal based upon the radial position of the portions of the ram 30 sensed by sensors 148, 150 and 248, 250.
• a secondary signal is also generated for each magnet pair which is added to the primary signal to provide a resultant signal which is used to determine the force applied by the magnet pair.
• This secondary signal may be generated in a manner identical to that described in the Goldowsky patent.
• this secondary force signal may be generated through the use of a predetermined algorithm which is stored in computer software and which is applied to the raw sensor signal generated by an associated radial position sensor.
• control data representative of the each radial position sensor signal value as a function of ram axial position is accumulated and stored for at least one and preferably about 20 previous ram strokes. This stored data is then processed and used to adjust the predetermined algorithm, e.g.
• the primary control algorithm may be periodically modified to account for changing conditions, such as heating and cooling of machine components, which may effect the force which must be exerted on the ram to maintain it in a centered position during all phases of the stroke.
• the primary control algorithm e.g. 310 for each opposed set of electromagnets, e.g. 232, 236, by starting with a straight line primary algorithm and simply running the apparatus. During initial stages of operation most of the control would be provided by the secondary control signal. As the number of operating cycles progress the primary control algorithm, through periodic adjustment would become more and more representative of the actual total control force required and would thus require progressively less adjustment by the secondary control force signal.
• Fig. 6 The above described control method which provides a total control force signal based upon a primary force signal and a modifying secondary force signal and wherein an algorithm used to generate the primary force signal is periodically modified based upon a ram radial displacement signal is illustrated in block diagram form in Fig. 6. It will of course be understood that the method illustrated in Fig. 6 is described for a single pair of opposed electromagnets and that an identical process will be performed for each of the opposed pair of magnets at each sampling interval of the data processing means.
• redraw assembly 408 comprises a redraw sleeve 410 which is coaxial with ram displacement axis RR.
• Redraw sleeve 410 has a central cylindrical cavity extending therethrough which is adapted to slidingly receive ram member 30 therethrough.
• the general sequence of reciprocal motion of redraw sleeve with respect to the motion of ram 30 is as described in the above referenced Maytag patent.
• the redraw sleeve 410 comprises a forward end 410 which is adapted to receive a can body preform known as a cup (not shown) thereon.
• the redraw sleeve comprises a i sar end 414 which is fixedly secured to a redraw carriage 416.
• the redraw carriage has a first and second bushing 416, 418 mounted therein which are adapted to slide on post members 422, 424.
• the post members have rear end portions which are fixedly mounted on a forward portion of ram bearing housing 62 and which have forward end portions which are fixedly mounted on redraw support bracket 430 which is itself attached to the ram housing 62.
• a redraw actuator assembly 439 is fixedly supported by the support bracket 430.
• the actuator assembly comprises a forward ring shaped electromagnet 440 positioned forwardly of the redraw carriage and defining the forwardmost travel position of the redraw carriage.
• the actuator assembly also comprises a rear ring shaped electromagnet 442 positioned rearwardly of the redraw carriage and defining the rearwardmost travel position of the redraw carriage.
• the forward and rear redraw magnets 440, 442 are energized and deenergized in response to control signals generated by data processing unit 130.
• the data processing means generates control signals which are sent to control circuits 441, 443 to energize or deenergize electromagnets 440, 442.
• the control signals are generated in response to ram 30 position as determined by the pulse signal from encoder 50.
• the control signal for each electromagnet 440, 442 is generated by applying a predetermined algorithm to the ram position signal. The algorithm which is applied may be determined analytically or empirically.
• the resulting force applied by each of the electromagnets causes the redraw carriage to begin moving forwardly at the beginning of each ram stroke. The forward movement of the redraw carriage is sufficiently fast such that the cup carried by the redraw sleeve it moved into engaged position with the tool pack housing 20 prior to the arrival of the ram 30.
• Fig. 5 illustrates a typical force profile for obtaining such a result.
• the electromagnets are energized and deenergized in a similar manner to return the redraw carriage to its rearmost position at approximately the same time that the ram 30 begins its rearward travel.
• FIG. 8 illustrates a redraw portion of a can body maker which may be identical to the redraw assembly illustrated in Figs. 1 and 2, except that an alternative redraw actuator assembly 1010 replaces the redraw actuator assembly 439 shown in Fig. 1.
• the alternative redraw actuator assembly illustrated in Fig. 8 comprises a first and second redraw actuator unit 1012, 1014 associated with opposite lateral sides of the redraw carriage 416.
• the construction of each of the actuator units 1012, 1014 is preferably identical.
• Actuator unit 1014 comprises a shaft 1020 which is fixedly attached to one lateral side of the redraw carriage 416 as by threading attachment, welding, or other conventional attachment means well-known in the art.
• the shaft 1020 has a central longitudinal axis AA which is parallel to the path of reciprocal movement of redraw sleeve 410.
• Shaft 1020 passes through an electromagnet assembly 1022 which is energized with electricity provided through electrical cable 1024.
• the electromagnet assembly 1022 is fixedly mounted on a frame portion 12 of the body maker.
• Shaft 1020 is longitudinally displaceable with respect to electromagnet assembly 1022.
• a shaft position sensor 1026 is also fixedly mounted on body maker frame 12.
• Shaft 1020 is longitudinally displaceably received therethrough.
• Position sensor 1026 may comprise a linear voltage differential transformer of a type well-known in the art such as disclosed in Horowitz, P. and Hill, W. , The Art of Electronics, Cambridge University Press (1980) , pp.
• the shaft position sensor generates a signal indicative of the longitudinal position of shaft 1020 which is transmitted through electrical cable 1028 to redraw controller unit 1030.
• Actuator unit 1012 comprises a shaft 1021, electromagnet assembly 1023 with cable 1025, and shaft position sensor 1027 with cable 1029 which may be identical to corresponding components of actuator unit 1014.
• Redraw controller unit 1030 receives signals through cables 1028 and 1029 connected to shaft position sensors 1026 and 1027 indicative of the position of redraw actuator shafts 1020 and 1021 and also receives a signal indicative of ram 30 position, e.g. a signal from ram drive encoder unit 50 via cable 1032.
• the controller receives electrical power through power cable 1034.
• the redraw actuator shaft and ram shaft position signals are processed by the controller according to one or more predetermined control algorithms which determine the amount and direction of electric current which is supplied to the electromagnetic coils of units 1022, 1023.
• electromagnetic assembly 1022 may comprise a rigid, box-shaped housing 1052 which is fixedly attached to support frame 12.
• the housing 1052 defines an interior cavity 1054 having openings at front and rear portions thereof in which are mounted ram receiving bearings 1056 and 1058.
• An electrical coil 1060 helically wound about a central coil axis which is coaxial with shaft 1020 axis AA is provided near the outer periphery of housing interior cavity 1054.
• the electrical coil 1060 receives electrical energy through cable 1024.
• Shaft 30 is constructed from a nonmagnetic material.
• a plurality of ring magnets 1074, 1076, 1078, 1080 having an outer diameter equal to that of shaft 1020 are fixedly mounted in recessed portions-"of shaft 1020 in axially spaced relationship as shown in Fig. 9.
• the magnetic field produced by coil 1060 coacts with the ring magnets 1074, 1076, etc. to produce an axial force on shaft 1020 which is dependent upon the amount and direction of current through the coil 1060.
• Coaction between an electromagnetic coil and permanent magnet to produce an axially directed force is described in U.S. Patent Nos. 4,912,343; 4,892,328; and 4,814,732; each of which is hereby specifically incorporated by reference for all that is disclosed therein.
• the controller 1030 controls the position of redraw carriage shaft 1020 based upon the axial position of ram 30.
• the manner for controlling shaft 1021 is identical and thus will not be described.
• the block diagram of Fig. 10 indicates a typical control process which may take place during each sampling interval associated with ram 30 axial movement. Typically, there may be on the order of one sampling interval per millisecond.
• the controller 1030 receives and processes a signal from ram encoder unit 50 to determine the precise axial position of the ram.
• the controller 1030 receives and processes the signal from sensor 1026 to determine the actual axial position of redraw carriage shaft 1020.
• the controller 1030 determines the "ideal" axial position of shaft 1020 for the sensed ram axial position based upon a first predetermined algorithm.
• the first predetermined algorithm correlates ram position and shaft 1020 position during an "ideal" ram stroke in which the position of the redraw carriage at any particular point during the ram stroke is at the exact position intended by the body maker designer.
• This algorithm may be stored as a mathematical expression or may be stored as a series of correlated data points, etc.
• the ideal axial position of shaft 1020 is determined, this ideal position is compared with the actually sensed position of shaft 1020.
• coil 1060 is energized in the appropriate manner to accelerate or decelerate shaft 1020 to relatively move it in the direction of the ideal ram position.
• the amount of such acceleration produced on shaft 1020 is a function of the direction and amount of current flowing through coil 1060.
• the actual amount of current which is supplied is determined based upon a preset control algorithm which utilizes the comparison of shaft 1020 ideal and actual position as an input.
• the control algorithm may take into account the velocity and acceleration of both ram 30 and shaft 1020, their relative positions in the operating cycle, and/or other variables.
• the controller 1030 is provided with a data set indicative of the ideal redraw shaft position associated with each incremental ram position during an ideal operating stroke. Such data set will be referred to herein as the "ideal redraw/ram profile".
• the redraw actuator coil is energized according to a predetermined control algorithm which is adapted to nominally provide the ideal redraw profile.
• the actual redraw shaft axial position is monitored as a function of ram axial position during the first ram stroke and is stored as a data set which will be referred to herein as an "actual redraw/ram profile".
• the control algorithm used during the first ram stroke is modified so as to more accurate. energize the redraw actuator coil to produce the ideal redraw/ram profile.
• This same process again takes place during the second ram stroke, and the control algorithm used in the second stroke is modified at the end of the second stroke and used to control coil energization during the third stroke, etc.
• the actual redraw shaft displacement as a function of ram movement during several previous ram strokes may be averaged or otherwise collectively used and compared to the ideal redraw/ram profile to provide a basis for modifying the control algorithm.
• modification of the control algorithm may take place after several operating strokes, as opposed to after every single operating stroke.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

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• 1991
  • 1991-09-06 EP EP91917462A patent/EP0547153A1/en not_active Withdrawn
  • 1991-09-06 CA CA 2090875 patent/CA2090875A1/en not_active Abandoned
  • 1991-09-06 JP JP51616091A patent/JPH06500503A/ja active Pending
  • 1991-09-06 WO PCT/US1991/006437 patent/WO1992004142A1/en not_active Application Discontinuation

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