A guard is "a protective device designed and fitted to reasonably minimize the possibility of inadvertent contact with machinery hazards, as well as to restrict access to other hazardous areas" (7). The same standard goes on to define four types of guards:

1. Shield or cover

2. Casing

3. Enclosure

4. Barrier

Guards are necessary to the prevention of traumatic injury and must always remain in place during machine operation. Removal of guards, either intentionally or forgetting to replace them following service or repairs, is a common factor in machine-related injuries (7).

Guards must allow routine maintenance, such as lubrication or cleaning, and still remain on the machine. Guards may also need to allow movement and flexibility of the guarded component if the component must move relative to other components. An example is the guarding system for the implement input driveline (IID), commonly known as the power takeoff (PTO) driveline. The driveline connects tractor to trailing machine and must move laterally, vertically, and telescopically. The guarding system made of three separate guards must maintain integrity while accommodating all movements. The guarding system must also allow a machine to be hooked up to a variety of different tractors.

Guards must maintain structural integrity while operating or being stored in harsh environments including weather, soil, manure, or physical abuse, over a period of decades. Guards must not be so difficult to remove and replace that operators find it simpler to leave them off after maintenance or repairs, yet not be so easily removed that they will fall off or be easily separated (intentionally or unintentionally) from the machines. Figure 6.1 shows a hinged shield on a new machine, in the raised position for access.

Openings that allow crops or other materials to enter may also be a path of entry for a hand, foot, or entire body. Increasing capacity of larger machines means larger and faster material intake. Guards that inhibit material intake are disliked and removed by owners. Augers, for example, are often guarded by cage-type guards that allow grain to pass through, yet prevent inadvertent contact with hands or feet. Yet some operators remove the guards because they feel the guard slows down grain flow. Also, such guards can be defeated by unsupervised small children where they are not designed to prevent small hands from reaching through, and would be restrictive if they did.

Replacement guards for older machines may be available from the manufacturer, but given the age of many machines and the fact that many smaller manufacturers have gone out of business, such guards may be difficult if not impossible to locate.

Figure 6.1. Hinged shield in raised (open) position for access.
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