The efficiency of a cattleyard system can be greatly increased by constructing self-locking gates. These gates offer some major advantages, the main ones being:
Self-locking gates obviously offer the most advantages around the working areas common to a set of yards (such as races and crushes), but their use in other areas should not be overlooked. They are equally useful and offer the same advantages in all parts of stockyards as well as on general farm gates.
There is no one specific design for self-locking cattle gate latches. They are generally tailored to specific situations and present gate designs. Included in this Agfact are two typical designs that are simple and functional (Figures 1a and 1b, and 2a and 2b). The suggested dimensions (Figures 1b and 2b) should be used as a guide only and it may be necessary to change them if they are to be adapted to old yards.
Self-locking latches are ideally suited to steel yards, being easily attached by welding, but there should be no problems if they are used on wooden gates.
A self-locking latch consists of three basic components:
Choose a bolt diameter large enough to withstand rough treatment from large animals. A diameter of 20 to 25 mm is required for cattle, and 15 to 20 mm for sheep. Chamfer the end of the bolt to assist it in sliding easily on the guide plate. The bolt is operated by a handle welded at right angles to it.
The spring used must have sufficient strength and travel length to provide a strong and positive location of the bolt. Use a galvanised spring on all designs to reduce corrosion. Figures 1 and 2 show alternative methods of locating the spring.
The backing plate is attached directly to the gate frame. Ten millimetre mild steel plate is suitable, welded to a steel gate or bolted to a wooden one. If it is required to be bolted, ensure that hole tolerances are small to minimise possible misalignment through movement of the fittings. Bolt guides can be made from drilled 10 mm plate (Figures 1a and 1b) or suitable diameter pipe (Figures 2a and 2b), welded to the backing plate.
The guide plate is attached to the latching post. Eight to ten millimetre mild steel plate is suitable, welded to a steel post or fastened to a wooden one with coach screws.
As the gate closes, the guide plate forces the bolt back, compressing the spring. To do this, the guide plate should be curved, from an initial angle of 45°, decreasing steadily to a flat section, perpendicular to the bolt, where the hole is located (Figure 3).
It is important to have the locating hole 10 mm larger than the bolt diameter to ensure engagement of the bolt.
A stop, 10 × 15 × 50 mm, welded on the guide plate just past the locating hole, halts the gate if the bolt doesn’t engage (see Figure 2a). The stop is not required if the gate is to swing both ways. In this case, a guide plate is then required on both sides of the latching post (Figure 3).
The latch mechanism should be routinely oiled and greased to ensure long life and trouble-free operation. Gates and latching posts that sag or shift will cause problems with misalignment, so ensure that these components are as secure as possible when considering this design of latch.
Well-designed and well-constructed self-locking gate latches will more than pay for themselves in ease of operation and safety as well as improving the overall efficiency of your stock-handling system.