Essential elements for making good glass containers is keeping the gob delivery equipment cooled and more importantly lubricated. Lubrication is introduced at a number of points and traditionally, scoop lubrication has been achieved by the overrun from the shear sprays but this can lead to problems at the scoops due to insufficient cooling/lubrication.
One answer has been to install separate scoop sprays directed into the funnels. The most common method is to use spray nozzles mounted opposite the interceptor (deflector) and spray into the funnels from a distance. Usually these nozzles spray the same emulsion as that fed to the shear sprays. This has the added benefit of cooling/lubricating the interceptor if it is in use but there are problems, principally the fact that the spray nozzles rarely direct all the spray into the funnels resulting in very poor conditions around the gob distributor. In addition, emulsion strength is determined by the shear spray requirements, and this may be far from the most efficient ratio of water to oil.
Graphoidal Developments, the Chesterfield based specialist in lubrication and engineering systems offers a complete solution that addresses all of the problems associated with other methods.
With the Graphoidal method, a Scoop Spray Plate, located above the funnels is used thus ensuring that 100% of cooling/lubrication is sprayed directly into the funnels. The oil and water are atomised in the air delivery system resulting in a very fine mist that provides optimum surface cooling and adhesion. This also gives total flexibility over the type and amount of oil sprayed, and additional water cooling.
Some manufacturers use oil only and there are many different types of oils designed specifically to assist with scoop lubrication. By injecting the oil into the individual air inlets of the scoop spray plate there is absolutely no possibility of blockages.
The quantity of oil used per cavity can be precisely controlled, resulting in a significant saving in running costs, and providing optimum lubrication of the funnels/scoops.
The timing for the operation of the solenoid valves in the air and water lines are usually controlled from the IS machine control system. It is usual for the air solenoid to operate at a high frequency as this will ensure that oil is applied consistently. The flow of water is controlled by a fine adjustment needle valve, and the frequency regulated to provide sufficient cooling for the production requirements. Bigger and faster cut rates will require more lubrication and cooling.
There is no "recognised standard" for scoop lubrication, and many different variants can be found. The simplest method is to use the shear spray emulsion which simulates the position of plants where the overrun of the shear emulsion provides cooling/lubrication.
A more flexible method is to use individual air inlets with oil injection. For SG operation this is easily achieved. For DG it is possible to produce a scoop spray plate with an internal geometry arranged to provide equal oil distribution to each cavity. For TG either individual oil feeds are required for each inlet, or the use of a special oil mixing/distributor block to ensure equal distribution per cavity.
Using this method it is possible to spray additional cooling water or emulsion should this be necessary. This system has the greatest flexibility, as both the delivery oil dosing rate can be controlled and the ratio and flow of the additional emulsion.
It may be necessary to retain the "old" spray system to cool the interceptor whilst in use, or alternatively use an interceptor cooling spray system. Control of oil dosing can be as a stand-alone system, or as part of a combined shear and scoop spray system.
Typical oil consumption per cavity is approximately 12-15 millilitres per hour which when compared to existing systems, is a very attractive cost saving option, regardless of other benefits including improvements in glass distribution, and improved machine productivity.