Drum shell formation
View Patent ↗In the method of forming a drum shell that consists of plywood, the steps that includes forming the shell under pressure and heat into cylindrical configuration, providing inner and outer cooling platens adapted to respectively engage the interior and exterior surfaces of the heated shell, trapping the heated shell between the platens, at elevated pressure, allowing the shell to cool by heat transfer from shell side wall or walls into pressure exerting side walls, and while trapped between such platens, at elevated pressure, and removing the cooled shell from between the cooling platens.
1. In the method of forming a drum shell that consists of sheet plywood, the steps that include:
a) trapping and forming the shell under pressure and heat into generally cylindrical configuration,
b) providing separate sets of inner and outer cooling platens adapted to respectively engage the interior and exterior surfaces of the heated shell,
c) trapping the heated shell between such cooling platens, at elevated pressure,
d) allowing the shell to cool while trapped between said cooling platens, at elevated pressure,
e) and removing the cooled shell from between the cooling platens,
f) said trapping and forming including relatively displacing a primary set of inner and outer semi-circular platens toward one another to trap and progressively deform the sheet plywood into U-shape having leg portions projecting in generally parallel relation from a bend formed between the primary platens, and thereafter relatively displacing a secondary set of inner and outer semi-circular platens toward one another, then toward the primary platens to trap and progressively deform the sheet plywood leg portions into semi-circular shape, there being a gap maintained between the primary and secondary set platens.
2. The method of claim 1 including transferring heat from the shell side wall or walls to the cooling platens during such cooling.
3. The method of claim 1 including cooling the cooling platens during said heat transfer.
4. The method of claim 3 including passing coolant liquid in heat transfer relation with the cooling platens during said transfer of heat from the shell to the cooling platens.
5. The method of claim 2 including maintaining the rate of heat transfer from different portions of the shell, and sidewardly thereof, to sides of the cooling platens, substantially constant during said cooling.
6. The method of claim 1 wherein said elevated pressure is in excess of 1,000 psi.
7. The method of claim 5 wherein said elevated pressure is in excess of 1,000 psi.
8. The method of claim 1 wherein said elevated pressure is in excess of 2,000 psi.
9. The method of claim 1 wherein each of said inner and outer platens has circular segment configuration.
10. The method of forming a drum shell consisting of plywood, the steps that include:
a) providing first inner and outer shell forming semi-circular platens, in two sets,
b) trapping plywood between the two sets of platens at elevated temperature and pressure to annularly form the drum shell, by displacing one set of inner and outer semi-circular platens toward one another to trap and progressively deform the plywood into U-shape having leg portions projecting in generally parallel relation from a bend formed between said one set of inner and outer semi-circular platens, and thereafter displacing another set of inner and outer semi-circular platens toward one another, then toward said one set of inner and outer semi-circular platens to trap and progressively deform the plywood leg portions into semi-circular shape, while maintaining a gap between said two sets of inner and outer semi-circular platens,
c) providing second inner and outer shell cooling platens,
d) trapping the formed shell in heated state between the second platens at elevated pressure,
e) allowing the shell to cool between the second platens, by heat transfer sidewardly of the shell to second platens, while remaining at elevated pressure, and
f) removing the cooled shell from between the inner and outer second platens.
11. The method of claim 10 including transferring heat from the second platens to cooling liquid during said e) step.
12. The method of claim 10 wherein each of said first platens has multiple circular segment configuration.
13. The method of claim 10 wherein each of said second platens has multiple circular segment configuration.
14. The method of claim 10 wherein multiple of said first platens are provided in a first bank, and multiple of said second platens are provided in a second bank, and wherein the following steps are included:
f) multiple heated shells are transferred from the first bank to the second bank, for cooling in accordance with steps d) and e), and multiple cooled shells are removed from the second bank, for further processing.