致谢7附录（英文资料翻译）BalerA baler is a piece of farm machinery used to compress a cut and raked crop (such as hay, straw, or silage) into compact bales that are easy to handle, transport and store Several different types of balers are commonly used, each producing a different type of bales rectangular or cylindrical, of various sizes, bound with twine, netting, or wire. Industrial balers are also used in material recycling facilities, primarily for baling metal, plastic, or paper for transport.Round balerThe most frequently used type of baler in industrialized countries is the large round baler. It produces cylinder-shaped round or rolled bales. Grass is rolled up inside the baler using rubberized belts, fixed rollers, or a combination of the two. When the bale reaches a predetermined size, either netting or twine is wrapped around it to hold its shape. The back of the baler swings open, and the bale is discharged. The bales are complete at this stage, but they may also be wrapped in plastic sheeting by a bale wrapper, either to keep hay dry when stored outside or convert damp grass into silage. Variable-chamber balers typically produce bales from 48 to 72 inches (120 to 180 cm) in diameter and up to 60 inches (150 cm) in width. The bales can weigh anywhere from 1,100 to 2,200 pounds (500 to 1,000 kg), depending upon size, material, and moisture content. Originally conceived by Ummo Luebbens circa 1910, the first round baler did not see production until 1947, when Allis-Chalmers introduced the Roto-Baler. Marketed for the water-shedding and light weight properties of its hay bales, AC had sold nearly 70,000 units by the end of production in 1960. The next major innovation came in 1972, when the Vermeer Company began selling its model 605 - the first modern round baler. Previously, round hay bales had been little more than lumps of grass tied together, but the Vermeer design used belts to compact hay into a cylindrical shape as is seen today.Large rectangular balerAnother type of baler in common use produces large rectangular bales, each bound with a half dozen or so strings of twine which are then knotted. Such bales are highly compacted and generally weigh somewhat more than round bales. In the prairies of Canada they are called prairie raptors.Small rectangular balerA type of baler which is less common today in some places but which is still prevalent in many countries such as New Zealand and Australia to the exclusion of large bales produces small rectangular (often called square) bales. Each bale is about 15 in x 18 in x 40 in (40 x 45 x 100 cm). The bales are wrapped with two, three, or sometimes four strands of knotted twine. The bales are light enough for one person to handle, about 45 to 60 inches (1.1 to 1.5 m).To form the bale, the material to be baled, (which is often hay or straw) in the windrow is lifted by tines in the balers pickup. This material is then dragged or augered into a chamber that runs the length of one side of the baler. A combination plunger and knife moves back and forth in 附录the front end of this chamber. The knife, positioned just ahead of the plunger, cuts off the material at the spot where it enters the chamber from the pickup. The plunger rams the material rearwards, compressing it into the bales. A measuring device measures the amount of material that is being compressed and, at the appropriate length it triggers the mechanism (the knotter) that wraps the twine around the bale and ties it off. As the next bale is formed the tied one is driven out of the rear of the baling chamber onto the ground or onto a special wagon hooked to the rear of the baler. This process continues as long as there is material to be baled, and twine to tie it with.This form of bale is not much used in large-scale commercial agriculture, because of the costs involved in handling many small bales. However, it enjoys some popularity in small-scale, low-mechanization agriculture and horse-keeping. Besides using simpler machinery and being easy to handle, these small bales can also be used for insulation and building materials in straw-bale construction. Square bales will also generally weather better than round bales because a more much dense stack can be put up. Convenience is also a major factor in farmers deciding to continue putting up square bales, as they make feeding and bedding in confined areas (stables, barns, etc.) much easier.Many of these older balers are still to be found on farms today, particularly in dry areas, where bales can be left outside for long periods. The automatic-baler for small square bales took on most of its present form in 1940. It was first manufactured by the New Holland Ag and it used a small petrol engine to provide operating power. It is based on a 1937 invention for a twine-tie baler with automatic pickup.Wire balersBales prior to 1937 were manually wire-tied with two baling wires. Even earlier, the baler was a stationar