Distributed drives for a multi-stage can necking machine

A multi-stage can necking machine having distributed drives is provided. The multi-stage can necking machine may include a plural of operation stages, wherein at least some of the operation stages may be configured for can necking operations. Each operation stage may include a main turret shaft, a transfer starwheel shaft, and a support for mounting the main turret shaft and transfer starwheel shaft. Each main turret shaft and transfer starwheel shaft may have a gear, and the gears of the operation stages may be in meshed communication to form a continuous gear train. A plural of motors may be distributed among the operation stages and mechanically coupled to the gear train, wherein each one of the motors may be capable of transmitting power to the gear train.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related by subject matter to the inventions disclosed in the following commonly assigned applications: U.S. patent application Ser. No. 12/109,031 filed on Apr. 24, 2008 and entitled “Apparatus For Rotating A Container Body”, U.S. patent application Ser. No. 12/108,950 filed on Apr. 24, 2008 and entitled “Adjustable Transfer Assembly For Container Manufacturing Process”, U.S. patent application Ser. No. 12/108,926 filed on Apr. 24, 2008 and entitled “Container Manufacturing Process Having Front-End Winder Assembly”, U.S. patent application Ser. No. 12/109,131 filed on Apr. 24, 2008 and entitled “Systems And Methods For Monitoring And Controlling A Can Necking Process” and U.S. patent application Ser. No. 12/109,176 filed on Apr. 24, 2008 and entitled “High Speed Necking Configuration.” The disclosure of each application is incorporated by reference herein in its entirety.

FIELD OF THE TECHNOLOGY

The present technology relates to a manufacturing machine having distributed drives. More particularly, the present technology relates to a multi-stage can necking machine having distributed drives.

BACKGROUND

Metal beverage cans are designed and manufactured to withstand high internal pressure—typically 90 or 100 psi. Can bodies are commonly formed from a metal blank that is first drawn into a cup. The bottom of the cup is formed into a dome and a standing ring, and the sides of the cup are ironed to a desired can wall thickness and height. After the can is filled, a can end is placed onto the open can end and affixed with a seaming process.

It has been the conventional practice to reduce the diameter at the top of the can to reduce the weight of the can end in a process referred to as necking. Cans may be necked in a “spin necking” process in which cans are rotated with rollers that reduce the diameter of the neck. Most cans are necked in a “die necking” process in which cans are longitudinally pushed into dies to gently reduce the neck diameter over several stages. For example, reducing the diameter of a can neck from a conventional body diameter of 2 11/16thinches to 2 6/16thinches (that is, from a 211 to a 206 size) often requires multiple stages, often 14.

Each of the necking stages typically includes a main turret shaft that carries a starwheel for holding the can bodies, a die assembly that includes the tooling for reducing the diameter of the open end of the can, and a pusher ram to push the can into the die tooling. Each necking stage also typically includes a transfer starwheel shaft that carries a starwheel to transfer cans between turret starwheels.

The starwheel shafts and the main turret shafts each include a gear, wherein the gears of each shaft are in meshed communication to form a continuous gear train. In conventional can necking systems, a single motor is used to provide the torque required to drive the entire gear train at high speeds. In some circumstances, such as when personnel safety is implicated, an emergency requires rapid stopping of the turrets. An emergency stop put a high torque load on the gear teeth compared with normal operation. Start up conditions may also create relatively high torque load on some gear teeth.

There is a general need for improved driving configurations for necking machines.

SUMMARY

A multi-stage can necking machine may have distributed drives. Such a multi-stage can necking machine may include a plural of operation stages, wherein at least some of the operation stages may be configured for can necking operations. Each operation stage may include a main turret shaft, a transfer starwheel shaft, and a support for mounting the main turret shaft and transfer starwheel shaft. Each main turret shaft and transfer starwheel shaft may have a gear, and the gears of the operation stages may be in meshed communication to form a continuous gear train. A plural of motors may be distributed among the operation stages and mechanically coupled to the gear train, wherein each one of the motors may be capable of transmitting power to the gear train.

In some embodiments, the multi-stage can necking machine may not require an oil bath for the gears that drive the shafts to properly operate. For example, the multi-stage can necking machine may have some gears made of a composite material. Because the gears are made of a composite material, and not steel, they do not have to operate within an oil bath. Furthermore, certain composites may be used that expand when they heat up to thereby help reduce backlash between adjacent gears.

In some embodiments, the multi-stage can necking machine may be configured to provide easy access to the gears. For example, the multi-stage can necking machine may be configured such that each shaft may extend through a respective support so that the gears may be exterior to the supports.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A preferred configuration for driving a multi-stage can necking machine is provided. The multi-stage can necking machine incorporates technology that overcomes the many shortcomings of known multi-stage can necking machines. The present invention is not limited to the disclosed configuration, but rather encompasses use of the technology disclosed, in any manufacturing application according to the language of the claims.

As shown inFIG. 1, a multi-stage can necking machine10may include several necking stages14. Each necking stage14includes a necking station18and a transfer starwheel22. Each one of the necking stations18is adapted to incrementally reduce the diameter of an open end of a can body, and the transfer starwheels22are adapted to transfer the can body between adjacent necking stations18, and optionally at the inlet and outlet of necking machine10. Conventional multi-stage can necking machines, in general, include an input station and a waxer station at an inlet of the necking stages, and optionally include a bottom reforming station, a flanging station, and a light testing station positioned at an outlet of the necking stages. Accordingly, multi-stage can necking machine10, may include in addition to necking stages14, other operation stages such as an input station, a bottom reforming station, a flanging station, and a light testing station as in conventional multi-stage can necking machines (not shown). The term “operation stage” or “operation station” and its derivatives is used herein to encompass the necking station14, bottom reforming station, a flanging station, and a light testing station, and the like.

FIG. 2is a detailed view depicting operative parts of one of the necking stations18. As shown, each necking station18includes a main turret26, a set of pusher rams30, and a set of dies34. The main turret26, the pusher rams30, and the dies34are each mounted on a main turret shaft38. As shown, the main turret26has a plurality of pockets42formed therein. Each pocket42has a pusher ram30on one side of the pocket42and a corresponding die34on the other side of the pocket42. In operation, each pocket42is adapted to receive a can body and securely holds the can body in place by mechanical means, such as by the action pusher ram and the punch and die assembly, and compressed air, as is understood in the art. During the necking operation, the open end of the can body is brought into contact with the die34by the pusher ram30as the pocket on main turret26carries the can body through an arc along a top portion of the necking station18.

Die34, in transverse cross section, is typically designed to have a lower cylindrical surface with a dimension capable of receiving the can body, a curved transition zone, and a reduced diameter upper cylindrical surface above the transition zone. During the necking operation, the can body is moved up into die34such that the open end of the can body is placed into touching contact with the transition zone of die34. As the can body is moved further upward into die34, the upper region of the can body is forced past the transition zone into a snug position between the inner reduced diameter surface of die34and a form control member or sleeve located at the lower portion of pusher ram30. The diameter of the upper region of the can is thereby given a reduced dimension by die34. A curvature is formed in the can wall corresponding to the surface configuration of the transition zone of die34. The can is then ejected out of die34and transferred to an adjacent transfer starwheel.

As best shown inFIG. 2, a main turret gear46(shown schematically inFIG. 2without teeth) is mounted proximate to an end of shaft38. The gear46may be made of suitable material, and preferably is steel.

Also shown inFIG. 2, a plate50may be mounted near the end of shaft38but on the to the gear46. The plate50may help ensure that the shaft38does not move within a support.FIG. 1depicts each shaft38mounted in a respective support52.

As shown inFIG. 3, each starwheel22may be mounted on a shaft54, and may include several pockets58formed therein. The starwheels22may have any amount of pockets58. For example each starwheel22may include twelve pockets58or even eighteen pockets58, depending on the particular application and goals of the machine design. Each pocket58is adapted to receive a can body and retains the can body using a vacuum force. The vacuum force should be strong enough to retain the can body as the starwheel22carries the can body through an arc along a bottom of the starwheel22.

As shown, a gear62(shown schematically inFIG. 3without teeth) is mounted proximate to an end of the shaft54. Gear62may be made of steel but preferably is made of a composite material. For example, each gear62may be made of any conventional material, such as a reinforced plastic, such as Nylon 12.

As also shown inFIG. 3, a horizontal structural support66supports transfer shaft54. Support66includes a flange at the rear end (that is, to the right ofFIG. 3) for bolting to an upright support of the base of machine10and includes a bearing (not shown inFIG. 3) near the front end inboard of the transfer starwheel22. Accordingly, transfer starwheel shaft54is supported by a rear end bearing that preferably is bolted to upright support52and a front end bearing that is supported by horizontal support66, which itself is cantilevered from upright support52. Preferably the base and upright support52is a unitary structure for each operation stage.

FIG. 4illustrates a can body72exiting a necking stage and about to transfer to a transfer starwheel22. After the diameter of the end of a can body72has been reduced by the first necking station18ashown in the middle ofFIG. 4, main turret26of the necking station18adeposits the can body into a pocket58of the transfer starwheel22. The pocket58then retains the can body72using a vacuum force that is induced into pocket58from the vacuum system described in co-pending U.S. patent application Ser. No. 12/108,950, which is incorporated herein by reference in its entirety, carries the can body72through an arc over the bottommost portion of starwheel22, and deposits the can body72into one of the pockets42of the main turret26of an adjacent necking station18b. The necking station18bfurther reduces the diameter of the end of the can body72in a manner substantially identical to that noted above.

Machine10may be configured with any number of necking stations18, depending on the original and final neck diameters, material and thickness of can72, and like parameters, as understood by persons familiar with can necking technology. For example, multi-stage can necking machine10illustrated in the figures includes eight stages14, and each stage incrementally reduces the diameter of the open end of the can body72as described above.

As shown inFIG. 5, when the shafts38and54are supported near their rear ends by upright support52, and the ends of the shafts38and54preferably are cantilevered such that the gears46and62are exterior to the supports52. The gears46and62may have different diameters such that gear46may have a larger diameter than gear62. A cover (not shown) for preventing accidental personnel contact with gears46and62, may be located over gears46and62. As shown, the gears46and62are in mesh communication to form a continuous gear train. The gears46and62preferably are positioned relative to each other to define a zig-zag or saw tooth configuration. That is, the main gears46are engaged with the transfer starwheel gears62such that lines through the main gear46center and the centers of opposing transfer starwheel gears62form an included angle of less than 170 degrees, preferably approximately 120 degrees, thereby increasing the angular range available for necking the can body. In this regard, because the transfer starwheels22have centerlines below the centerlines of main turrets26, the operative portion of the main turret26(that is, the arc through which the can passes during which the necking or other operation can be performed) is greater than 180 degrees on the main turret26, which for a given rotational speed provides the can with greater time in the operative zone. Accordingly the operative zone has an angle (defined by the orientation of the centers of shafts38and54) greater than about 225 degrees, and even more preferably, the angle is greater than 240 degrees, as described in co-pending U.S. patent application Ser. No. 12/109,176. In general, the greater the angle that defines the operative zone, the greater the angular range available for necking the can body.

As shown inFIG. 5, the multi-stage can necking machine10may include several motors74to drive the gears46and62of each necking stage14. As shown, there preferably is one motor74per every four necking stages14. Each motor74is coupled to and drives a first gear80by way of a gear box82. The motor driven gears80then drive the remaining gears of the gear train. By using multiple motors74, the torque required to drive the entire gear train can be distributed throughout the gears, as opposed to prior art necking machines that use a single motor to drive the entire gear train. In the prior art gear train that is driven by a single gear, the gear teeth must be sized according to the maximum stress. Because the gears closest to the prior art drive gearbox must transmit torque to the entire gear train (or where the single drive is located near the center on the stages, must transmit torque to about half the gear train), the maximum load on prior art gear teeth is higher than the maximum tooth load of the distributed gearboxes according to the present invention. The importance in this difference in tooth loads is amplified upon considering that the maximum loads often occur in emergency stop situations. A benefit of the lower load or torque transmission of gears46and62compared with that of the prior art is that the gears can be more readily and economically formed of a reinforced thermoplastic or composite, as described above. Lubrication of the synthetic gears can be achieved with heavy grease or like synthetic viscous lubricant, as will be understood by persons familiar with lubrication of gears of necking or other machines, even when every other gear is steel as in the presently illustrated embodiment. Accordingly, the gears are not required to be enclosed in an oil-tight chamber or operate in an oil bath, but rather merely require a minimal protection against accidental personnel contact

Each motor74is driven by a separate inverter which supplies the motors74with current. To achieve a desired motor speed, the frequency of the inverter output is altered, typically between zero to 50 (or 60 hertz). For example, if the motors74are to be driven at half speed (that is, half the rotational speed corresponding to half the maximum or rated throughput) they would be supplied with 25 Hz (or 30 Hz).

In the case of the distributed drive configuration shown herein, each motor inverter is set at a different frequency. Referring toFIG. 6for example, a second motor88may have a frequency that is approximately 0.02 Hz greater than the frequency of a first motor92, and a third motor96may have a frequency that is approximately 0.02 Hz greater than the frequency of the second motor88. It should be understood that the increment of 0.02 Hz may be variable, however, it will be by a small percentage (in this case less than 1%).

The downstream motors preferably are preferably controlled to operate at a slightly higher speed to maintain contact between the driving gear teeth and the driven gear teeth throughout the gear train. Even a small freewheeling effect in which a driven gear loses contact with its driving gear could introduce a variation in rotational speed in the gear or misalignment as the gear during operation would not be in its designed position during its rotation. Because the operating turrets are attached to the gear train, variations in rotational speed could produce misalignment as a can72is passed between starwheel pockets and variability in the necking process. The actual result of controlling the downstream gears to operate a slightly higher speed is that the motors88,92, and96all run at the same speed, with motors88and96“slipping,” which should not have any detrimental effect on the life of the motors. Essentially, motors88and96are applying more torque, which causes the gear train to be “pulled along” from the direction of motor96. Such an arrangement eliminates variation in backlash in the gears, as they are always contacting on the same side of the tooth, as shown inFIG. 7. As shown inFIG. 7, a contact surface100of a gear tooth104of a first gear108may contact a contact surface112of a gear tooth116of a second gear120. This is also true when the machine starts to slow down, as the speed reduction is applied in the same way (with motor96still being supplied with a higher frequency). Thus “chattering” between the gears when the machine speed changes may be avoided.

In the case of a machine using one motor, reductions in speed may cause the gears to drive on the opposite side of the teeth. It is possible that this may create small changes in the relationship between the timing of the pockets passing cans from one turret to the next, and if this happens, the can bodies may be dented.

The present invention is illustrated herein. The present invention is not limited to the particular structure disclosed herein, but rather encompasses straightforward variations thereof as will be understood by persons familiar with can necking machine technology. The invention is entitled to the full scope of the claims.