WO1999034942A1

WO1999034942A1 - Press for can manufacture

Info

Publication number: WO1999034942A1
Application number: PCT/GB1998/003893
Authority: WO
Inventors: Kevin Ambrose; Mark Ian Davies; Julia Duncalf
Original assignee: Crown Cork & Seal Technologies Corporation; Carnaudmetalbox Plc
Priority date: 1997-12-30
Filing date: 1998-12-23
Publication date: 1999-07-15
Also published as: AU1774699A; ZA9811888B; GB9727444D0

Abstract

A press for can manufacture, such as a can bodymaker or cupper, comprising a geared drive mechanism and a forming tool, separated by a seal. The geared drive mechanism is lubricated with lubricating gear oil and the forming tool is supplied with lubricating coolant. The same lubricant is used in both the coolant and the gear oil so that leakage of gear oil into the coolant, or vice versa, does not cause contamination.

Description

PRESS FOR CAN MANUFACTURE

This invention relates to a press for can manufacture. In particular, it relates to a press such as a can bodymaker or cupper in which the drive mechanism is separated from the forming tool, for example by seals. Can bodyτnakers are well known and have been described in US-3735629 and US-4173138 (both Standun) , among other patent literature. These documents describe a bodymaker having a geared drive mechanism which drives a horizontally reciprocable ram. The geared drive mechanism includes a hydrostatic oil bearing assembly which ensures that all moving and load bearing parts are constantly supplied with pressurised gear oil and a slide assembly connected to the rear of the ram is typically immersed in several millimetres of this gear oil. The forward end of the ram exits the drive mechanism on its forward stroke to pass through a die assembly or tool pack for forming a can body. The die assembly in a bodymaker may include one or more ironing dies for wall ironing a cup into a can body. This operation necessarily generates a large amount of frictional heat and coolant containing lubricant is supplied to the cup and the dies to reduce both heat and friction in the can forming process. A seal pack is mounted between the drive section and the die assembly to wipe the outer circumference of the ram as it moves through the seals when exiting the drive assembly and entering the tool pack. This seal pack thus separates the bearing oil in the drive assembly from the coolant/lubricant in the die assembly.

In conventional can making processes, the cup or can body is removed from the press and washed to remove all traces of coolant/lubricant. One known method of cleaning the cup or can body is to wash off the residue with a chemical at 70°C to 80°C. An alternative method used more recently is to use a high pressure water rinse. This has also been found to provide effective removal of the coolant/lubricant .

A problem discovered since the move to washing by means of this high pressure water is that any traces of gear oil cannot be removed from the cup/can body without the use of chemicals. This is a particular problem where the chemical must be non-toxic if the can is to be used for packaging food products. Use of chemicals also negates any advantages which may have been gained by moving from a chemical wash to the pressurised water method. Although in theory the seal pack will prevent passage of oil from the drive assembly into the tool pack, in practice the Applicant has found that this cannot be prevented. Contamination to some extent is almost always a problem and up to 3% gear oil has been found during the wash process.

The present invention seeks to provide a solution to this problem.

According to the present invention, there is provided a press for forming metal can bodies, the press comprising: a first assembly including a ram, a geared drive mechanism for driving the ram and a lubricating gear oil for coating load bearing surfaces; a die pack assembly including means for holding a metal blank, a die pack and a lubricating coolant, the ram being enterable into the die pack on a forward stroke; and a seal assembly separating the first and second assemblies and isolating the lubricating gear oil and the lubricating coolant from each other; characterised in that the lubricating gear oil and the lubricating coolant both include the same lubricant, whereby any leakage of lubricating gear oil into the lubricating coolant or vice versa does not cause contamination. The press may comprise a can body maker.

In an alternative embodiment of the present invention, there is provided a press for forming metal can bodies, the press comprising: a first assembly including a punch, a geared drive mechanism for driving the punch and a lubricating gear oil for coating load bearing surfaces; and a tool assembly including means for holding a metal blank, a die and a forming lubricant, the punch being enterable into the tool assembly on a forward stroke; in which the lubricating gear oil is isolated from the forming lubricant; the lubricating gear oil and the forming lubricant both include the same lubricant, whereby any leakage of lubricating gear oil into the forming lubricant or vice versa does not cause contamination. This embodiment of press may comprise a cupper in which the forming lubricant may be applied to the sheet metal outside the press itself.

Since the function of the lubricating gear oil is to provide high load bearing support and to prevent metal to metal contact within the drive assembly, whereas the lubricating coolant is predominantly a coolant with some lesser friction reducing additive function, the lubricant used in the lubricating gear oil and the lubricating coolant of the present invention may differ from both the gear oil and the coolant lubricant of the prior art . Ideally, the lubricant is completely water soluble so that rinsing by means of high pressure water, without additional chemicals, is possible. Preferably, the lubricant base fluid is a stable polyglycol with additives as required to obtain the necessary load carrying capacity, thermal stability etc. The additives should not be dispersed in mineral oils. They should be dispersed in a water soluble medium to ensure that they can be completely removed by high pressure rinsing with water. The lubricant may be a standard lubricant, such as the ALPHASYN (trade name) PG Range produced by Castrol for example, or a minor modification of a known lubricant . Suitable lubricants are available from usual suppliers of such lubricants. A preferred embodiment of the invention will now be described, by way of example only, with reference to the drawings, in which:

Figure 1 is a side section of a can bodymaker; and Figure 2 is a perspective view of the drive assembly and seal pack for a bodymaker such as that of figure 1.

The schematic of figure 1 shows a press 1 comprising a frame 2 which supports a tool pack 5 and drive mechanism 10. The drive mechanism comprises a gearbox (not shown) and a first action assembly which includes a ram 12, lever arm 14 and crank shaft 16. Rotation of the crank shaft 16 moves the ram/punch 12 into and out of the tool pack 5.

Die pack assembly 20 comprises tool pack 5 and a second action assembly which includes a blank holder mounted on a crosshead 24 which is connected to push rods

26 (shown cut away in figure 1) and spreader plate/levers 28. A cam follower 30 on lever 28 engages a cam 32 on the crank shaft 16.

The die pack assembly 20 and drive mechanism 10 are separated from each other by primary bulkhead 40 and seal pack 42.

The drive assembly is shown in further detail in figure 2. It is apparent from this figure that the slide blocks 34 surrounding ram 12 can be immersed in gear oil in order to eliminate metal -to-metal contact with the ram. The primary bulkhead 40 and, in the exploded view, seal pack 42 can also be seen.

Although it might appear from this figure that the two assemblies are well separated from each other, in practice, as noted above, the Applicant has found this is not the case. In fact, can bodies made by bodymakers have only been fully cleaned by the use of a chemical wash in order to eradicate traces of gear oil which has penetrated into the die pack assembly from the drive mechanism. However, the solution of the present invention, which uses known washable lubricants or minor modifications thereto, has enabled can bodies to be fully cleaned simply by means of high pressure water jets.

The invention has been described above by way of example only and changes may be made without departing from the scope of the invention as defined by the claims. For example, although not described in any detail here, the same problem of contamination may arise in cuppers which form a shallow cup from a sheet metal blank. In cuppers, forming lubricant is applied to sheet metal outside the press and a closed circuit press lubrication system mechanism is provided with a separate lubricant within the press. Although the press lubricant is theoretically separated from the metal forming, occasionally such lubricant may fall onto the sheet metal before or during the cupping operation. If the press lubricant is the same as, or contains the same lubricating components as that for metal forming, no problem will arise in the subsequent wash process.

Claims

CLAIMS :

1. A press for forming metal can bodies, the press comprising: a first assembly including a ram, a geared drive mechanism for driving the ram and a lubricating gear oil for coating load bearing surfaces; a die pack assembly including means for holding a metal blank, a die pack and a lubricating coolant, the ram being enterable into the die pack on a forward stroke; and a seal assembly separating the first and second assemblies and isolating the lubricating gear oil and the lubricating coolant from each other; characterised in that the lubricating gear oil and the lubricating coolant both include the same lubricant, whereby any leakage of lubricating gear oil into the lubricating coolant or vice versa does not cause contamination .

2. A press according to claim 1, in which the press comprises a can body maker.

3. A press according to claim 1 or claim 2, in which the lubricant is water soluble.

4. A press for forming metal can bodies, the press comprising : a first assembly including a punch, a geared drive mechanism for driving the punch and a lubricating oil for coating load bearing surfaces; and a tool assembly including means for holding a metal blank, a die and a forming lubricant, the punch being enterable into the tool assembly on a forward stroke; characterised in that the lubricating oil is isolated from the forming lubricant; and the lubricating oil and the forming lubricant both include the same lubricant, whereby any leakage of lubricating oil into the forming lubricant or vice versa does not cause contamination .

5. A press according to claim 4, in which the press comprises a cupper.