1、Design of sawing anti-blocking mechanism for no-tillage planter and its cutting mechanism Liao Qingxi1,Gao Huanwen2,Shu Caixia1 (1.Engineering and Technology College,Huazhong Agricultural University,Wuhan430070,China； 2.Engineering College,China Agricultural University,Beijing100083,China) Abstract:
2、 Based on blocking issues of no-tillage planter for dry-land farming in two-crop-a-year region in North of China and shortcomings of anti-blocking mechanism developed, such as higher rotation speed (above 1500 r/min) and bigger power consumption (width power consumption per unit up to 16 41.74 kW/m,
3、 including traction power), a new sawing anti-blocking mechanism was developed and its cutting mechanism was investigated in this paper. Meanwhile stress distribution of the saw-tooth blade calculated by the ANSYS finity element software showed that the saw-tooth blade would be feasible to cut corn
4、straws. Experimental results in the soil bin showed that: 1)The sawing anti-blocking mechanism with two cutting modes of sustaining and no-sustaining cut could realize an integrated function of cutting and directly throwing by reverse rotation, namely, it could throw straws directly to the rear of t
5、he opener by former angle of saw-tooth and thrower； 2)The cutting rate of straws would increase along with the rising of straw moisture and rotation speed, and higher moisture of straws would be of benefit to improving cutting quality； 3)The cutting rate of straws would decrease along with the risin
6、g of velocity of vehicle while interval of the moved and fixed blade was determined. And the sawing anti-blocking mechanism had higher cutting quality and lower power consumption without leaky cutting and tearing out with small interval of the moved and fixed blade. Compared with other driving anti-
7、blocking mechanisms, theoretical analysis and experimental results showed that the sawing anti-blocking mechanism had fine cut capability and lower rotation speed (650 r/min) and lower power consumption (power consumption per unit width up to 2.95 kW/m) as well as stronger suitability to different s
8、tubbles mulch. Additionally, a new way was found out to improve anti-blocking performance of no-tillage planter. Key words: no-tillage planter； sawing anti-blocking mechanism； cutting mechanism； cutting rate CLC number: S223.2 Document code: A Article ID:1002-6819(2003)05-0064-07 Received date:2003-
9、06-15 1 Introduction Anti-blocking issue of no-tillage planter had become one of the key factors affecting production efficiency and seeding quality of two-crop-a-year region in North of China. It was because there was a great deal of crop stubbles and crop seeding was started shortly after crop had
10、 been harvested, leaving no time for crop stubbles to decay. At present, there are two methods to solve anti-blocking issue of no-tillage: 1) Straws were chopped by the straw chopper before seeding, it would lead to adding working procedure and increase costs of production as well as delaying seedin
11、g time； 2) Stubbles were cleared out by driving chopping mechanism fixed on no-tillage planter, such as Strip Wheat Spinning and Furrow Planter made in Hebei Nonghaha Machinery Ltd Corporation and 2BMDF-Corn Strip Chopper made in China Agricultural University1and so on. In practice the driving chopp
12、ing mechanism had significant effect on anti- blocking, but also bigger vibration and noise as well as lower security because straws were chopped at high rotation speed. It was reported that the blade base linear velocity of several main straw chopping mechanisms was between 37 56 m/s2, mostly chopp
13、ing mechanism combined with cutting and striking had higher striking velocity and higher power consumption3, e.g. the blade base linear velocity up to 34 m/s could obtain fine cutting effect for corn straws4, and 24 m/s on rice and wheat straws by supporting pole, respectively5. Even if corn straws
14、were cut by sliding cut with vertical blade, its velocity of cutting one straw, two straws and three straws must be up to 10.3 m/s, 13.6 m/s, 15.8 m/s6, respectively, and had higher power consumption. In a word, because the driving chopping mechanism developed presently had high rotation speed ( abo
15、ve 1500 r/min ) and higher power consumption (width power consumption per unit up to 16 41.74 kW/m, including traction power), to decrease rotation speed and power consumption would be urgent in practice. Based on practical problems, the objective in this paper is to find a way to solve the shortcom
16、ing that it 64 is difficult for common smooth blade to seize straws and it must run at higher rotation speed, decrease power consumption and improve cutting effect as well as anti-blocking performance of no-tillage planter. Additionally some experiments were done by selecting saw-tooth as cutting bl
17、ade of no-tillage planter and cutting mechanism of the sawing anti-blocking mechanism was investigated. 2 Structure and cutting rule of the sawing anti-blocking mechanism 2.1 Structure and characteristics The sawing anti-blocking mechanism was made up of saw-tooth blade, throwing ban device, princip
18、al shaft, moved and fixed blade combination, covering shell, opener and working frame as well as transmission system. Sketch of the sawing anti-blocking mechanism is shown in Fig. 1. The main parts included saw-tooth blade, throwing ban device as well as fixed blade combinations. Diameter of saw-too
19、th with 60 teeth was 350 mm； throwing ban device with max 270 mm turning diameter was fixed on between adjacent saw-teeth； fixed blade combinations consisted of fixed blade with tooth and vertical type blade, and tooth type blade same to saw-tooth, Moreover, the vertical type blade would be used to
20、obstruct straws without cutting from throwing area and participated in cutting straws. The sawing anti-blocking mechanism was fixed on the soil bin device, its width was 600 mm, the interval of adjacent openers was 200 mm. The sawing anti-blocking mechanism had many characteristics such as straws wo
21、uld be chopped by saw-tooth blade and fixed blade combinations, and had two cutting modes with susta-ining and no-sustaining cutting, the blade base line velocity of saw-tooth was lower to tossing blade type, namely, the sawing anti-blocking mechanism could change higher speed hewing into lower spee
22、d sawing. 2.2 Cutting principle The sawing anti-blocking mechanism was driven to reverse rotation by power. First, straws were cut in no-sustaining mode by saw-tooth blades while saw-tooth blades touched straws, then after straws were completely cut down, they would be free and be thrown to the rear
23、 of opener by throwing ban device and inertial force. Second, straws not being completely cut down would be thrown to former upward and be cut in sustaining mode by fixed blade combinations until any of straws would be cut down, straws having been cut down were thrown to the rear of opener by throwi
24、ng ban device and saw-tooth. In turn, time after time, straws would be carried out continuously to cut and throw by the sawing anti-blocking mechanism. The lowest point of the saw-tooth blades kept 15 30 mm interval from the soil. In terms of spreading status of straws in field existed perpendicular
25、ity or certain angle with marching direction, saw principal in landscape orientation had been determined for the sawing anti-blocking mechanism in order to decrease repeated cutting, leaky cutting and tearing out. Working procedures of the sawing anti-blocking mechanism were as follows: 1) no-sustai
26、ning cut phase: static straws relative to ground were cut firstly atNpoint by saw-tooth blades, then, straws would be cut down completely or embedded in saw-tooth. Straws being cut down completely would be free and 65 Liao Qingxi et al: Design of anti-blocking mechanism for no-tillage planter droppe
27、d into adjacent saw-tooth； 2) dragging and delivering phase: after straws dropped into adjacent saw-tooth, they would be thrown to former upward by the throwing ban device, moreover, straws embedded in the saw-tooth would be thrown to former upward by the saw-tooth at higher speed rotation； 3) susta
28、ining cut phase: straws not being cut down completely in no-sustaining cut phase would be cut in sustaining mode by fixed blade combinations atK point until any of straws would be cut down completely； 4)throwing phase: straws being cut down were thrown directly to the rear of opener by tooth former
29、slanting angle of the saw-tooth and throwing ban device, time and again, straws would be carried out continuously to cut and throw. The working principle of the sawing anti-blocking mechanism is shown in Fig.2. 2.3 Analysis of mechanics characteristics of saw-tooth blade Cutting properties of saw-to
30、oth to cut straws belong to wriggly cut of no-metal materials, its ultimate objective is not only to improve surface cutting quality, but also to raise cutting efficiency, so it can decrease sawing force and power consumption9. Because the ratio of its diameter 350 mm to its thickness 1.8 mm is over
31、 150, the saw-tooth blade belongs to exceed thin disc. It is as plane stress and no-axis symmetry problem according to elasticity theory. And because the saw-tooth blade was tighten by flange tray, six freedoms of its center hole were restricted, so its center parts could be regarded as restricted s
32、tatus completely not to bring any displacement and rotation. Saw-tooth blade belongs to excessive blade tools, it would bring to alternative sawing forces in cutting straws, The reasons lied in: 1) structure of straws with inner empty and outside hardness had determined micro-hardness un-uniformity
33、distribution, so the single tooth force would be uncertain in cutting straws； 2) the total sawing forces of saw-tooth in horizontal direction would be uncertain because the tooth of saw-tooth blade is not continuous. These alternative characteristics would bring to transfiguration of the saw-tooth,
34、moreover, the transfigured properties an size was relative to the stress properties and size of the saw-tooth in supporting outside loading. So, it was very essential to make clear stress distribution of the saw-tooth in order to ensure smooth cutting. The stress distribution of the saw-tooth blade
35、was calculated by the ANASYS finity element software. Number of the tooth participating in cutting straws was determined to 2 3 teeth while diameter of straws was in 20 45 mm11. The saw-tooth made in 65Mn ofEequal to 210 GPa12andto 0.28 was separated into 1200 cells and 1260 nodes by trapezia griddi
36、ng. Thus the stress distributions ofX,YandXYplane had been obtained by the ANASYS software according to the most average wring value 26.8 Nm13of the saw-tooth to cut straws by the wring sensor. The stress distributions are shown in Fig.3. Calculated results showed: 1 ) the saw-tooth blade had acted
37、as alternative stress from the whole stress distribution of sawtooth, tooth and around center hole of the saw-tooth had been distributed primary stress, the biggest pressing stress was up to 70776 Pa, moreover, the biggest pulling stress up to 19945 Pa. Compared with yield fatigue intension 735 MPa1
38、2of the saw-tooth, the saw-tooth blade was difficult to be destroyed, so it would be feasible to cut corn straws； 2)Fig.3 showed, around stress distribution of the saw-tooth blade was in symmetry distribution, the area of relative bigger stress only occupied 3.33% of the saw-tooth whole area, the ot
39、her 96.67%； 3)the former tooth of saw-tooth supported the biggest forces among the whole saw-tooth while the former tooth of the saw-tooth touched firstly straws, and its stress value was the smallest before cutting straws, but when saw-tooth started to cut straws, the stress value would increase 66
40、 Vol.19, No.5 Transactions of the CSAE Sept.2003 sharply, its values would be over 105times comparing with the stress values before saw-tooth started to cut straws. However the stress would be down to the lowest point while saw-tooth had finished cutting straws. Thus, the saw-tooth was acted as alte
41、rnative stress. 3 Materials and method 3.1 Experimental equipment The experiment was conducted in the soil bin device, of 20m-long, 0.89m-wide, 0.6m-high, the available working journey of vehicle was 16 m, and the working velocity of vehicle was from 0.12 m/s to 1.2 m/s. And other equipment included
42、: AKC-205 type wring sensor, the sawing anti-blocking mechani-sm, control tank, computer operation platform, etc. 3.2 Experimental materials The average height and diameter of corn straw is 2.25 m, 25. 6 mm, respectively. It is made up of leaves and skin and marrow. The weight of leaves and marrow occupy above 55% of whole straw and their mechanical intension are much lower； and the weight of skin made up of scarfskin and bunchy organization occupy 35% or so,
