Toggle clamp

Typical double-toggle clamp (a) open and (b) closed (after Modem Plastics... 

While a hydraulic clamp machine requires a very large cylinder in the center of the platen to apply full clamp tonnage with hydraulic pressure, hydraulically actuated toggle clamps (Fig. 5.62i ) use a small cylinder and a mechanical toggle. To close the clamp, the cylinder moves forward, extending the toggle links (Fig. 5.6261" ). Clamp... 

A 2CK) ton HPM injection molder base with toggle clamp. A 220 ton hydraulic clamp unit was also considered. The toggle clamp unit is expected to be less costly by approximately... 

In most cases, the compression movement is done by the clamping unit of the injection-molding machine. Modern machines with hydraulic or toggle clamping units are able control the position and the... 

Fig. 3. Basic hydraulic (toggle clamp) injection-molding machine components. Illustration by John W. Bozzelli Rick J. Bujanowski.

Figure 3 depicts many of these components in a tsT)ical hydranhc injectionmolding machine with a toggle clamp. 

There are a number of variations in machine constmction and processing techniques (10). There are hydraulic (Fig. 4), hydromechanical, and toggle clamping machines (Fig. 4). There are also tiebar-less clamps as shown in Figure 5, and two-platen machines that were developed to save floor space over the normal three-platen machine. 

FIGURE 1.3 Injection molding machine in typical 3-platen design with toggle clamping unit, without mold... 

The force requirements ensure that the clamp unit must be engineered very robustly, but this conflicts with the need to open and close the mold rapidly to minimize production time. A variety of clamp mechanisms has evolved in the search for a suitable compromise. The two most common types are the direct hydraulic clamp (Fig. 7.2) and the toggle clamp (Fig. 7.3). Other variants include hybrid toggle/hydraulic types, lock-and-block systems, and electromechanical systems. 

Figure 7.3 Typical toggle clamp unit. A Movable platen, B fixed platen, C mold, D front link, E rear link, F actuating cylinder, G tiebar, H crosshead link.

The conventional manual and semiautomatic press is vertical and closes upward, downward, or bidirectionally. The pressure medium is hydraulic fluid or air clamp force is applied by hydraulic ramps or toggle clamps. The source of fluid can be separate or integrated in the press. Table 10.2 shows the force capacity (tonnage) of different press sizes. 

A typical example is shown in Fig. 19 where a toggle clamp is being used to hold a component flat on a base. Location is provided to this example by a stop and locator pins. Toggle clamps are normally purchased as standard items and give adequate pressure with only a small angular movement of their handles. With correct adjustment several hundred pounds of pressure may be exerted. 

In the more simple machines hand operated toggle clamps are used, but with the more expensive equipment the frame will be hydraulically operated, the clamping margin around the edge of the sheet is usually a minimum of 1 in (25.4 mm). 

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