Rules Governing Correct Crimping
Crimp Collet. Use an appropriate crimp collet. This must have a shape perfectly adapted to the various kinds of bottles or cans to be crimped. Figure 14 shows a recommended shape for a crimp collet.
Depth Stop. Use a depth stop adapted to various kinds of valves and pumps. The shape of the depth stop must be designed according to the external shape of the valve ferrule. The depth stop has three functions. It transmits the necessary force to compress the sealing gasket; it enables adjustment of the crimping height; and it positions the valve ferrule correctly inside the crimp collet. The result is a good concentric crimp.
On the inside of the depth stop profile, it is often better to provide an inlet cone on which the stem and the dome of the valve will slide. A precise and gentle placement of the valve ferrule into the depth stop will, thus, be obtained, as shown in Fig. 15.
Crimping Diameter. The theoretical crimping diameter must be determined to adjust the crimp collect closing. Figure 16 shows a schematic of the adjustment of crimping diameter. The theoretical crimping diameter can be determined according to a simple equation. Assuming a glass bottle
configuration, the diameter of crimp collet, with tongs in their closed position, is:
where d is the bottle diameter beneath the neck, e is the thickness of the valve ferrule metal, and 0.008 in. is the clearance necessary to avoid breakage risk of the bottle and the crimp collet.
The practical adjustment of the crimp collet closing is performed by putting the machine in its low position (tongs closed). The crimp collet closing is then adjusted using a standard-diameter measuring gauge, as in Fig. 17.
Crimping Height. Calculate the theoretical crimping height to determine the position of the depth stop in the crimp collet. Knowledge of the theoretical
crimping height allows the adjustment of the depth stop to the correct position in the crimp collet. Figure 18 illustrates the crimp parameters. In a glass bottle configuration, the crimping height can be adjusted according to the following equation:
H = 2e + Jc + h where H is the crimping height, h is the height of the glass neck, e is the thickness of the valve ferrule metal, and Jc is the thickness of the compressed gasket.
Compression. To prevent leaks resulting from an imperfect crimp of the valve ferrule on the neck of the container, the thickness of the seal must be reduced. The seal will, thus, be compressed, providing sufficient vertical force that is applied to the ferrule just before crimping (Table 2). The object of the compression is to provide a sufficient vertical force on the valve ferrule during the crimping.
To obtain sufficient compression of the sealing gasket, it is necessary to respect the values given in Table 1. Compression of the sealing gasket is shown in Figs. 19 and 20 for a glass bottle, a coated glass bottle, and roll-neck (Cebal Safet) and cut-edge (Presspart) aluminum cans.
Figure 21 shows a crimp on a glass bottle indicating a correct crimp, a crimp that is too tight, and a crimp that is not tight enough. Figure 22 shows the same range of crimping phenomena for an aluminum can. A crimper control Socoge may be used to monitor crimp height. This device aims to define and control a size of crimping height on valves and pumps that are currently used on bottles in the perfumery and pharmaceutical industries.
The recommended crimp dimensions vary according to the types of container and valve being considered. The following discussion of dimensions for crimping is appropriate for Valois metering valves, type DF10 or DF30. Taking these examples, the precision with which valves may be attached to the containers can be indicated. Figure 23 refers to the 20-mm FEA standard glass bottle. The crimp collet closing diameter (D) may be
easily determined according to d, the diameter beneath the neck, which can be measured with a caliper gauge. As measured with a Socoge crimper control gauge, the crimping height is H = 0.209 ± 0.002 in. (5.3 ± 0.05 mm). These dimensions are valid only with a 1-mm gasket. Figure 24 refers to an aluminum can type of Cebal Safet. The crimp collet closing diameter should be D = 0.65 in., and the crimping height is the same as that for the FEA standard glass bottle. Figure 25 refers to the aluminum can type of Presspart. The crimp collet closing diameter is 0.697 in., whereas the crimping height is 5.7 mm.
Pressure Filling. The propellant is introduced under high pressure into the container through the valve, as shown in Fig. 26. Most valve manufactures design their valves for this method.
Cold Filling. The propellant is cooled to a very low temperature and poured into an open container. However, this procedure creates the inconvenience of requiring equipment able to produce an extremely low temperature (— 50°F).
Undercap Filling. The propellant is filled under the valve immediately before crimping. This technique is used mainly for the 1-in-opening containers, because large quantities of propellant can be filled very quickly. Nevertheless, this method results in large losses of propellant.
General Description of a High-Pressure Propellant Filler
A high-pressure propellant-filling installation consists of two main units: a propellant compressor pump and a propellant-filling machine.
Propellant Compressor Pump. To feed the propellant-filling machine properly, a propellant compressor pump is necessary. The pump guarantees a regular amount of propellant pressure supply and helps prevent the formation of a vapor phase in the metering cylinder of the filler and in the tubings of the system. When filling with propellant 12, for instance, an average pressure of 170-200 psig should be delivered at the outlet of the propellant pump.
When setting up or using a propellant-filling installation, the inlet of the pump must be connected to the liquid phase outlet of the propellant tank. On most of the propellant tanks that are commercially available, two valves allow the selection of either the vapor phase or the liquid phase of the propellant. It is important when using such a system to ensure that the vapor-phase valve of the propellant tank is correctly turned off. It is also important to avoid long pieces of tubing between the pump and the propellant tank. The maximum length of tubing should be 1 m (3 ft). This is shown in Figs. 26 and 27, which indicate a pressure-filling process.
Propellant Filler Unit. The propellant filler may also be compared with a syringe piston system, as was the concentrate-product filler. When the pneumatic pump pushes on the piston, a very high pressure builds up in the metering cylinder of the filler. A filling head is connected to the outlet of the metering cylinder and allows the introduction of the propellant into the container through the valve. As seen previously, this technique is called pressure filling.
To control the propellant pressure injection, that is, the pressure necessary to inject liquid propellant through the valve, an air regulator is fitted on the inlet of the pneumatic cylinder, as shown in Figs. 27 and 28. By adjusting the amount of air pressure allowed in the pneumatic cylinder, it is possible to decrease or increase the propellant pressure injection. This pressure injection varies, according to the type of valve, between 500 and 800 psi. Manufactures of valves usually recommend specific pressure injection for their products.
Filling Head. The filling head is the device that allows the propellant to be introduced into the container. Because valve manufacturers design their products differently, technical filling specifications cannot be the same for every valve on the market. Thus, it is not possible to use a standard filling head for all valves. Each valve requires an appropriate filling head to be pressure filled correctly. This filling head must also be designed according to the pressure-filling equipment used.
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